Documents published in 2017 : Scipedia

Strategies for Mobile Web Design
A. Cazañas, E. Parra

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 62

Abstract
This paper presents a literature review on the topic of web design, specifically with regard to mobile web design. The aim of the review is to identify and analyze major strategies and approaches to design for small-screen-size devices. Three strategies consistently appeared across the reviewed literature, namely, responsive web design, adaptive web design, and separate site. The analysis of these strategies intends to provide a clear understanding of their advantages and disadvantages, in terms of cost and user experience.
Abstract
This paper presents a literature review on the topic of web design, specifically with regard to mobile web design. The aim of the review is to identify and analyze major strategies [...]
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Case based reasoning applied to medical diagnosis using multi-class classifier: A preliminary study
D. Viveros-Melo, M. Ortega-Adarme, X. Blanco Valencia, A. Castro-Ospina, S. Murillo Rendón, D. Peluffo-Ordóñez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 61

Abstract
Case-based reasoning (CBR) is a process used for computer processing that tries to mimic the behavior of a human expert in making decisions regarding a subject and learn from the experience of past cases. CBR has demonstrated to be appropriate for working with unstructured domains data or difficult knowledge acquisition situations, such as medical diagnosis, where it is possible to identify diseases such as: cancer diagnosis, epilepsy prediction and appendicitis diagnosis. Some of the trends that may be developed for CBR in the health science are oriented to reduce the number of features in highly dimensional data. An important contribution may be the estimation of probabilities of belonging to each class for new cases. In this paper, in order to adequately represent the database and to avoid the inconveniences caused by the high dimensionality, noise and redundancy, a number of algorithms are used in the preprocessing stage for performing both variable selection and dimension reduction procedures. Also, a comparison of the performance of some representative multi-class classifiers is carried out to identify the most effective one to include within a CBR scheme. Particularly, four classification techniques and two reduction techniques are employed to make a comparative study of multiclass classifiers on CBR
Abstract
Case-based reasoning (CBR) is a process used for computer processing that tries to mimic the behavior of a human expert in making decisions regarding a subject and learn from [...]
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ECU@Risk, a methodology for risk management applied to MSMEs
E. Crespo Martínez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 60

Abstract
Information is the most valuable element for any organization or person in this new century, which, for many companies, is a competitive advantage asset (Vásquez & Gabalán, 2015). However, despite the lack of knowledge about how to protect it properly or the complexity of international standards that indicate procedures to achieve an adequate level of protection, many organizations, especially the MSMEs sector, fails to achieve this goal.Therefore, this study proposes a methodology for information security risk management, which is applicable to the business and organizational environment of the Ecuadorian MSME sector. For this purpose, we analyze several methodologies as Magerit, CRAMM (CCTA Risk Analysis and Management Method), OCTAVE-S, Microsoft Risk Guide, COBIT 5 COSO III. These methodologies are internationally used in risk management of information; in the light of the frameworks of the industry: ISO 27001, 27002, 27005 and 31000.
Abstract
Information is the most valuable element for any organization or person in this new century, which, for many companies, is a competitive advantage asset (Vásquez & Gabalán, [...]
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Monitoring System of Environmental Variables Using a Wireless Sensor Network and Platforms of Internet of Things
M. Quiñones-Cuenca, V. González-Jaramillo, R. Torres, M. Jumbo

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 59

Abstract
This work proposes a system for collecting meteorological data using a Wireless Sensor Network (WSN), that is able to transmit data in real-time. The system automatizes the process of collecting the data in a continuous manner for long periods of time, for this, the module is equipped with a source of solar energy that allows autonomous operation. In order to obtain viability of design and prototype implementation, the construction of two systems was proposed based on DigiMesh and Wi-Fi; those prototypes could be applied to different scenarios such as urban and rural areas. Additionally, it was performed an evaluation of broadcasting of information to platforms of Internet of Things (IoT), where the data collected by the nodes will be managed and displayed. This system was conceived as a low-cost alternative compared with conventional weather stations that offer these facilities and are based on free hardware and software components. Finally, the validation of the obtained results was performed using a statistical analysis with the collected data of the weather station Davis Vantage Pro, obtaining a maximum average relative error of 4.93%.
Abstract
This work proposes a system for collecting meteorological data using a Wireless Sensor Network (WSN), that is able to transmit data in real-time. The system automatizes the [...]
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Biomedical equipment for the control of nutrition and for the physical exercise of people with diabetes
A. Mantilla Guerra

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 58

Abstract
In order to contribute to the treatment of diabetes, which is one of the main causes of death in Ecuador and in the world, a research project is being developed to create equipment that allows the effective control and treatment of this disease. The electronic equipment created for nutrition control, allows the diabetic patient to have information about the amount of calories they should ingest in consideration of their activities and their medical treatment. The mechatronic equipment for the physical exercise of people with diabetic foot, allows the application of therapies according to the severity of the affection. Considering that this is a delicate and complex treatment, the equipment helps the patients to alleviate its discomfort, to decrease the time of recovery and in some cases even to avoid amputation. The construction of the biomedical equipment for the control of nutrition is completed. While the equipment for the treatment of diabetic foot is in a stage of development of prototypes and tests. Both equipment has been conceived and developed with rigorous engineering methods and under quality standards, making an important contribution to research, development of science, technology, and innovation.
Abstract
In order to contribute to the treatment of diabetes, which is one of the main causes of death in Ecuador and in the world, a research project is being developed to create [...]
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Tool for the quantitative evaluation of a Facebook app-based informal training process
A. Calle-Gómez, F. Fernández-Peña, P. Urrutia-Urrutia

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 57

Abstract
The study of the impact of Facebook in academy has been mainly based on the qualitative evaluation of the academic performance and motivation of students. This work takes as starting point the use of the Facebook app Sigma in the Universidad Técnica de Ambato. Students of this university share educative resources through Sigma. This constitutes an informal learning process. We have proposed to construct Gamma, a tool for the generation of statistics and charts that illustrates the impact of the social network in the resulting learning process. This paper presents the results of the study of how Gamma is valued by those who like to do informal learning. It was checked that 1) Gamma gives feedback about the value of educative resources and social actions and that 2) it allows the quantitative measurement of the impact of using Facebook in the informal learning process. As an added value, Gamma supports the communication between supporters and detractors of the use of Facebook in the academia.
Abstract
The study of the impact of Facebook in academy has been mainly based on the qualitative evaluation of the academic performance and motivation of students. This work takes [...]
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Design and implementation of a Smart Measurement System for AMI in the microgrid of the University of Nariño
A. Arciniegas M., D. Imbajoa R., J. Revelo F.

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 56

Abstract
This project describes a proposed Measure Management System, from the design stage to the implementation of a prototype smart meter, adapted to operate in the microgrid at the University of Nariño. This device features a constant record of measures, with resolution of 24 bits, sufficient to perform power quality analysis. In addition, it is integrated into the SCADA system through the open protocols MODBUS, DNP3 and IEC 61850, with scheduled cybersecurity techniques. Likewise, several management platforms for the monitoring of electrical variables and control over the current flow to the loads is designed. Finally, two study cases show the application of the implemented measure management system in the microgrid.
Abstract
This project describes a proposed Measure Management System, from the design stage to the implementation of a prototype smart meter, adapted to operate in the microgrid at [...]
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Evaluating the Graph-based Visualization Technique: A Controlled Experiment
G. Cárdenas, J. Aponte

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 55

Abstract
Many researchers have highlighted the scarcity of empirical studies that systematically examine the advantages and disadvantages of the use of visualization techniques for software understanding activities. Such studies are crucial for gathering and analyzing objective and quantifiable evidence about the usefulness of proposed visualization techniques and tools, and ultimately, for guiding the research in software visualization. This paper presents a controlled experiment aimed at assessing the impact of a graph-based visualization technique on comprehension tasks. Six common comprehension tasks were performed by 20 undergraduate software engineering students. The completion time and the accuracy of the participants’ responses were measured. The results indicate that on one hand the use of the graph-based visualization increases the correctness (by 21.45% in average) but on the other hand it does not reduce the completion time in program comprehension tasks.
Abstract
Many researchers have highlighted the scarcity of empirical studies that systematically examine the advantages and disadvantages of the use of visualization techniques for [...]
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Analysis of the accessibility in websites of Ecuadorian universities of excellence
T. Acosta, S. Luján-Mora

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 54

Abstract
Since the publication of the Ecuadorian Technical Standard NTE INEN ISO / IEC 40500 in 2014 and the Ecuadorian Technical Regulation RTE INEN 288 "The web contents accessibility" in 2016, web accessibility in Ecuador has taken great importance. In the educational field, the websites of Higher Education Institutions (HEI) have become a communication channel, where universities publish the information and services they offer. In addition, HEI must satisfy the rights of all citizens to have access to education, which includes persons with disabilities. In order to ensure access to the websites of HEI to all people it is important that HEI incorporate web accessibility as an essential requirement in their websites. The objective of this research is to perform the accessibility analysis of the websites of the Ecuadorian universities of excellence belonging to categories A, B and C; identify websites accessibility errors and to present some recommendations for a better fulfillment of the WCAG 2.0 accessibility guidelines by website designers and developers.
Abstract
Since the publication of the Ecuadorian Technical Standard NTE INEN ISO / IEC 40500 in 2014 and the Ecuadorian Technical Regulation RTE INEN 288 "The web contents accessibility" [...]
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Vertical Integration in factories using OPC-UA and IEC-61499
M. V. García, E. Irisarri, F. Pérez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 53

Abstract
Nowadays, factory automation systems need to cope with very different challenges, such as big data, IIoT, etc. These challenges lead to a new generation of automation systems based on the so-called Cyber-Physical Production Systems (CPPS) globally connected to form a flexible System of Cyber-Physical Production Systems (SoCPPS). CPPSs require acquisition of production system data and smart data processing to extract information to improve the overall system performance. To achieve that it is needed to bridge the gap between the control systems and higher layers. This paper discusses an approach to use the IEC 61499 function block concept to exchange data between plant floor and higher layers using an industrial standard like OPC UA. The OPC UA server offers subscription mechanisms, making possible the integration of several resources residing at plant floor. As it runs on embedded devices, the proposal makes possible to acquire plant information at low cost, enabling at the same time, a component-based design for enterprise plant floor control with independence of the hardware platform used
Abstract
Nowadays, factory automation systems need to cope with very different challenges, such as big data, IIoT, etc. These challenges lead to a new generation of automation systems [...]
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An Approach to the Optimization of Mobile Payments for the Transport System using (NFC) through Cloud Computing
E. Gómez Torres, N. Herrera-Herrera, M. Díaz

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 52

Abstract
The use of mobile devices has gradually increased. Every day, the number of organizations adopting systems which include some type of mobile payments is becoming bigger. Because of this reason, it is mandatory to have agile and quick systems to guarantee security and reliability, not only for the user but also for the operator. In that way, users will get a high-quality service based on mobile technologies. An analysis of NFC Technology has been made in this paper taking into consideration a proposal of a system development including mobile payments, which could be used in the transportation system of Metro of Quito. To assure the response time and transactional security, the use of cloud computing is recommended.
Abstract
The use of mobile devices has gradually increased. Every day, the number of organizations adopting systems which include some type of mobile payments is becoming bigger. Because [...]
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Low-Cost Solutions Using the Infrastructure as a Service with High Availability and Virtualization Model
C. Moreira Zambrano, W. Zambrano-Romero, R. Guamán-Quinché, W. Cuenca Álava

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 51

Abstract
This paper presents the results obtained from the implementation of an infrastructure to improve technological services of email, virtual learning environment, digital repository and virtual library at the Polytechnic Agricultural Higher School of Manabí (Polytechnic School of Agriculture of Manabí), ESPAM, through the use of high availability and virtualization mechanisms to provide more reliable resources. Virtualization is an empowering and cutting-edge technology that is transforming the operation of technological services, but it involves a paradigm shift in serviceoriented information technologies and cloud computing. To execute each of the processes the V-cycle methodology was used as a strategy. Virtualization services empowers companies and institutions by transforming how they operate to be at the forefront of innovation in their services as a technological solution. So the implementation of redundant technology in the ESPAM, has allowed its technological services are always operative, for the benefit of the university community, because if there were failures in the main system or services, the backups will be enabled quickly allowing the systems come into operation immediately.
Abstract
This paper presents the results obtained from the implementation of an infrastructure to improve technological services of email, virtual learning environment, digital repository [...]
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Analysis of free SSL/TLS Certificates and their implementation as Security Mechanism in Application Servers.
M. Cueva Hurtado, D. Alvarado Sarango

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 50

Abstract
Security in the application layer (SSL), provides the confidentiality, integrity, and authenticity of the data, between two applications that communicate with each other. This article is the result of having implemented Free SSL / TLS Certificates in application servers, determining the relevant characteristics that must have a SSL/TLS certificate, the Certifying Authority generate it. A vulnerability analysis is developed in application servers and encrypted communications channel is established to protect against attacks such as man in the middle, phishing and maintaining the integrity of information that is transmitted between the client and server.
Abstract
Security in the application layer (SSL), provides the confidentiality, integrity, and authenticity of the data, between two applications that communicate with each other. [...]
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Canny Edge Detection in Cross-Spectral Fused Images
P. Suárez, M. Villavicencio

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 49

Abstract
Considering that the images of different spectra provide an ample information that helps a lo in the process of identification and distinction of objects that have unique spectral signatures. In this paper, the use of cross-spectral images in the process of edge detection is evaluated. This study aims to assess the Canny edge detector with two variants. The first relates to the use of merged cross-spectral images and the second the inclusion of morphological filters. To ensure the quality of the data used in this study the GQM (Goal-Question- Metrics), framework, was applied to reduce noise and increase the entropy on images. The metrics obtained in the experiments confirm that the quantity and quality of the detected edges increases significantly after the inclusion of a morphological filter and a channel of near infrared spectrum in the merged images.
Abstract
Considering that the images of different spectra provide an ample information that helps a lo in the process of identification and distinction of objects that have unique [...]
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Estimating Sample Size for Usability Testing
A. Cazañas, A. de San Miguel, E. Parra

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 48

Abstract
One strategy used to assure that an interface meets user requirements is to conduct usability testing. When conducting such testing one of the unknowns is sample size. Since extensive testing is costly, minimizing the number of participants can contribute greatly to successful resource management of a project. Even though a significant number of models have been proposed to estimate sample size in usability testing, there is still not consensus on the optimal size. Several studies claim that 3 to 5 users suffice to uncover 80% of problems in a software interface. However, many other studies challenge this assertion. This study analyzed data collected from the user testing of a web application to verify the rule of thumb, commonly known as the “magic number 5”. The outcomes of the analysis showed that the 5-user rule significantly underestimates the required sample size to achieve reasonable levels of problem detection.
Abstract
One strategy used to assure that an interface meets user requirements is to conduct usability testing. When conducting such testing one of the unknowns is sample size. Since [...]
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Unsupervised analysis applied to the detection cardiac arrhythmias
M. Moreno-Revelo, S. Patascoy-Botina, A. Pantoja-Buchelli, J. Revelo Fuelagán, J. Rodríguez-Sotelo, S. Murillo-Rendón, D. Peluffo-Ordóñez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 47

Abstract
An arrhythmia is a pathology that consists on altering the heartbeat. Although, the 12-lead electrocardiogram allows evaluation of the electrical behavior from heart to determine certain pathologies, there are some arrhythmias that are difficult to detect with this type of electrocardiography. In this sense, it is necessary the use of the Holter monitor because it facilitates the records of the heart electrical activity for long periods of time, it is usually 24 up to 48 hours. Due to the extension of the records provided by the monitor, it is common to use computational systems to evaluate diagnostic and morphological features of the beats in order to determine if there is any type of abnormality. These computational systems can be based on supervised or unsupervised pattern recognition techniques, however considering that the first option requires a visual inspection about the large number of beats present in a Holter record, it is an arduous task, as well as it involves monetary costs. Consequently, throughout this paper we present the design of a complete system for the identification of arrhythmias in Holter records using unsupervised pattern recognition techniques. The proposed system involves stages of preprocessing of the signal, segmentation and characterization of beats, as well as feature selection and clustering. In this case, the technique k-means is used. These steps are applied within the framework of a segment-based methodology that improves the detection of minority classes. Additionally, initialization criteria are considered, which allow to enhance quality measures, especially sensitivity. As a result, it is determined that using k-means with the max-min initialization and a number of groups equal to 12, it is possible to obtain the best results, with values of: 99.36%, 91.31% and 99.16% for accuracy, sensitivity and specificity, respectively.
Abstract
An arrhythmia is a pathology that consists on altering the heartbeat. Although, the 12-lead electrocardiogram allows evaluation of the electrical behavior from heart to determine [...]
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MOOCs: factors that decrease desertion in students
M. Yamba-Yugsi, S. Luján-Mora

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 46

Abstract
We are experiencing constant technological change, which implies that learning and training requirements have been increased, they are increasingly high. One of these changes are Massive Open Online Courses (MOOC). As this is a new technology in our environment, the amount of desertion is high, it is essential to the analysis, to know the reasons of the high amounts of desertion and reduce the dropout of users in MOOC courses. For that, it is proposed to meet the different factors of the problem, for example, previous experience of users in making the MOOC courses, the level of satisfaction in the interaction with platforms that have courses MOOC and satisfaction by the end of a course. Additionally, knowing the user’s profile will make it easier for future courses suit them, although entails increasing the team and tailor a course to users, for the purpose of that they feel supported, intending to follow course and that they possess a new learning experience.
Abstract
We are experiencing constant technological change, which implies that learning and training requirements have been increased, they are increasingly high. One of these changes [...]
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Information security in data exchange between mobile devices with Android system using RSA encryption
F. Solís, D. Pinto, S. Solís

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 45

Abstract
The new styles and ways of life lead to greater use of wireless networks, the mobile device being a tool for data transmission, which are susceptible to threats in the transmission channels in the network. IT security plays a very important role in guaranteeing the availability, privacy and integrity of information, one of the techniques that helps in this task is cryptography, whose foundation is to transform a message so that it is unintelligible except for those who have the Key to decipher it. The research focuses on the use of the RSA algorithm between mobile devices, the encrypted data is sent through communication channels called threads that through formulas and processes executed on the server, will help to execute the encryption and decryption of the data. To carry it out, a prototype for the exchange of data between mobile devices wirelessly was designed and implemented, conducting performance tests with three nodes to improve the security. The results show the efficiency of the algorithm and additionally its functionality, the times of encryption and decryption are fast against the sending of information without any method or algorithm used.
Abstract
The new styles and ways of life lead to greater use of wireless networks, the mobile device being a tool for data transmission, which are susceptible to threats in the transmission [...]
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Knowledge based systems as an aid in information systems audit
R. Proaño Escalante, C. Saguay Chafla, S. Jácome Canchig, F. Sandoval Zambrano

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 44

Abstract
One of the problems that the IT auditor has when expressing an opinion about a finding is the subjectivity that can be due to many aspects, among the main ones: emotional, technical skills or abilities with which this opinion can be right or wrong. This is a major problem because the audit report issued may have distortions of the facts. On the other hand, the development of the expert systems involves capturing the knowledge of the human and transferring it to a computer program in which all the characteristics of this knowledge are emulated and considering a group of rules, the system can make decisions as a human does. Advances in artificial intelligence over the last few years have led to the development of these knowledge-based systems increasing and the results obtained are more real. The use of these systems presents a promising future in the field of computer audit. The objective of this article is to give a general idea of the characterization and use of knowledge based systems, the way they are implemented and their application to the audit of information systems as a tool to help the opinion issue at the moment of realization of an audit.
Abstract
One of the problems that the IT auditor has when expressing an opinion about a finding is the subjectivity that can be due to many aspects, among the main ones: emotional, [...]
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Internet of Things and Artificial Vision, Performance and Applications: Literature Review
V. Alvear-Puertas, P. Rosero-Montalvo, D. Peluffo-Ordóñez, J. Pijal-Rojas

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 43

Abstract
Internet of Things (or also known as IoT) is one of the technologies most named today because of the ability it envisages to connect all kinds of devices to the Internet. If to the potentialities of IoT we add another technology of high impact as It is the Artificial Vision we have a wide field of innovative applications, where the processing of images and video in real time allow the visualization of large amounts of data on the Internet. The main applications developed with IoT and Artificial Vision can be implemented in education, medicine, intelligent buildings, surveillance systems of people and vehicles, among others. This type of applications improves the quality of life of users, however, for their development an infrastructure is required that allows the convergence of different protocols and devices, but in a special way that can handle the different phases of the acquisition of images. In this work, a review of the beginnings, concepts, technologies and applications related to the Artificial Vision with the Internet of Things has been carried out to be able to understand in a precise way the impact of its application in daily life.
Abstract
Internet of Things (or also known as IoT) is one of the technologies most named today because of the ability it envisages to connect all kinds of devices to the Internet. [...]
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Development of Enterprise Architecture using a Framework with Agile Approach
F. Sandoval, V. Galvez, O. Moscoso

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (1), 42

Abstract
The development of an enterprise architecture (EA) in large organizations is complex. Thus, is important that the implementation of EA creates value in early stages of the process. This document contains a proposal of an EA framework design with agile approach based in TOGAF. This proposal is done with the objective to streamline the EA process. This framework presents a new design taking into account the current regulations, the target line of the organization and the principles proposed by the agile approach of EA. The objectives of each phase of the architecture development method ADM of TOGAF are matched with the requirements of the organization to extract only those that are aligned to the business. The deliverables proposed by TOGAF are analyzed with the goal to obtain, integrate and reduce the documentation in the implementation and modeling phases. This reduction allows more flexibility, less impact in the processes, reduction in development time and costs.
Abstract
The development of an enterprise architecture (EA) in large organizations is complex. Thus, is important that the implementation of EA creates value in early stages of the [...]
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Potential native trees and shrubs for reforestation in the Central Sierra of Ecuador
J. Caranqui Aldaz

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 17

Abstract
Within the National Forest Restoration Plan of the Ministry of Environment of Ecuador, the ESPOCH herbarium identified the species used in the Autonomous Parochial Governments of the provinces of Chimborazo, Cotopaxi and Tungurahua. The different institutions sent samples to the Herbarium of the Escuela Superior Politécnica del Chimborazo. We checked that the mentioned species are native and that they correspond to the established zones, for this the catalog of vascular plants was used. We processed the information from which 17 lists of forest species belonging to 21 families, 26 Genres and 49 species were generated. The most frequent species is Alnus acuminata Kunth in all provinces. The species should be generated from the environmental conditions of each of the provinces, and the species to be used in the program should be exclusively native since it is about preserving what little we have, even using known species in the first stage. In addition, not all species can be found in native populations, but only cultivated; this is, therefore, necessary to take into account since the requirements of the species for its development are not the same.
Abstract
Within the National Forest Restoration Plan of the Ministry of Environment of Ecuador, the ESPOCH herbarium identified the species used in the Autonomous Parochial Governments [...]
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Design and implementation of an automatically controlled plastic bottles cutting recycling machine
L. Hidalgo Aguilera, J. Imbaquingo, D. Mideros

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 16

Abstract
An automatic machine has been designed to obtain threads and ribbons through a continuous rotational cutting process. This machine processes plastic bottles used as containers for storage and transportation of soft drinks and non-carbonated drinks with a capacity of three liters. It is a mechatronic design, composed of simple mechanical / pneumatic, electrical and control systems, which allows to process up to fifty bottles per hour. A variety of products can be obtained; from threads with approximately 46.5 m in length and 1.6 mm thick (width) to ribbons with 11.3 m in length and 6.7 mm in width per bottle can be obtained. These products are economic raw material obtained from waste material such as plastic bottles, which are highly polluting elements of the environment due to the small percentage that is recycled especially in Ecuador. This raw material can have applications in some manufacturing processes such as the manufacture of brooms, ropes, baskets, bags, fasteners among others.
Abstract
An automatic machine has been designed to obtain threads and ribbons through a continuous rotational cutting process. This machine processes plastic bottles used as containers [...]
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Study of the compliance of the INEN 2205 standard in the seats of urban public transport bus
V. Reyes, C. Rosales, A. Guzmán, S. Báez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 15

Abstract
An important participation in the urban public transport offer of Quito is in the hands of the private company. Given the high demand, it will show the safety indicators and the quality of the service. This fact is the fundamental motivation of this article, which verified the compliance with the INEN 2205 standard for passenger and driver seats in a specific urban transport company. A sample of the units is shown and each point shows a body model. In particular, measurements were made of seats using: flexometer, bubble level and inclinometer. In addition, visual inspections and simple experiments of mechanical friction were carried out to evaluate the qualitative characteristics. Finally, a simple verification count was performed on the sample and confidence intervals and hypothesis tests were constructed for the statistical ratio. Population inferences showed that 41% and 55% of seats for passengers and drivers, respectively, did comply with the regulations; while the multivariate analysis allowed to identify sample groups and correlations between them. It was concluded that it exists in the observation of the regulations regarding the state of the seats and angular parameters.
Abstract
An important participation in the urban public transport offer of Quito is in the hands of the private company. Given the high demand, it will show the safety indicators and [...]
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Physical, chemical and microbiological evaluation of cassava silage with cowpea and microbial culture
J. Miranda-Yuquilema, A. Marín-Cárdenas, M. González-Pérez, D. Sánchez-Macías

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 14

Abstract
The aim of this work was to evaluate the physical, microbiological, fibrous and lactic acid changes of cassava silage with cowpea used on biological mix. Fifty kg whole cassava (root, stem and leaves), 20 kg of cowpea flour and 4 L of microbial culture containing Lactobacillus acidophillus, Streptococcus thermophillus and Klyumyces fragilis (L-4 UCLV) were used. The evaluated treatments were: Y100integral cassava (Y100), integral cassava more 20% cowpea (Y+C), and integral cassava more 20% cowpeas and 8% of microbial culture (Y+C+BP). The ensiled material was preserved in sterile glass bottles with wide mouth. A completely randomized design was used. The physicochemical, microbiological, fibrous and lactic acid characteristics were evaluated. For 18 months, the dry matter, crude and true protein, lactic acid contents and the microbial viability was higher (P
Abstract
The aim of this work was to evaluate the physical, microbiological, fibrous and lactic acid changes of cassava silage with cowpea used on biological mix. Fifty kg whole cassava [...]
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Use of sodium bentonite as a pretreatment to the tangential microfiltration of Castilla’s blackberry wine Rubus glaucus Benth
G. Mariño, M. Coronel, C. González, E. Beltrán

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 13

Abstract
This research studied the influence of clarification techniques of Castilla's blackberry wine Rubus glaucus Benth on its chromaticity, turbidity and yields of the process. Initially, the tangential microfiltration (TMF) at three different working pressures (1.5, 2.0 and 2.5 bar) and then the treatment of the feed with sodium bentonite prior the filtration. The TMF at 1.5 bar obtained the highest Volume Reduction Factor (VRF) and the best performance, standardizing the pressure conditions for the TMF with pretreatment. According the pH, the optimum quantity of flocculant added to each batch of wine was established at 9 grams, carried to rest at 6 ° C (6, 12 and 24 hours), obtaining 610 ± 38 g for the highest proportion of turbid in the batch of 6 hours of rest, product of a greater unstable catch by the clarifier. The TMF of the pretreated batches indicated representative improvements in the yield, up to 40%. All the analyzed microfiltered wine samples with and without pretreatment achieved a turbidity less than 2 NTU, accomplishing with the quality criterion of "bright red", concluding that the TMF separately and with pretreatment improve the quality of the product, but they can cause color deterioration.
Abstract
This research studied the influence of clarification techniques of Castilla's blackberry wine Rubus glaucus Benth on its chromaticity, turbidity and yields of the process. [...]
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The visual effect and the necessity of determinating the superficial whitening method of the macadamia’s nut
M. Jijón, T. Guerrero Villegas, A. Barahona, P. Aguilar Barriga

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 12

Abstract
Macadamia nut is considered "the queen of nuts", because of its high energy content and nutritional value. Certain types of nuts are considered to be non-commercial due to their color; therefore, the aim of this study was determining a method of surface bleaching using additives that do not affect the taste, smell and texture of the walnut. Color is a sensory quality of food; it’s an indicator and a critical quality factor in fresh and processed products. Three food additives were used as bleaching agents: 1% citric acid for 2 minutes and 3% for 1 minute, 0.1% ascorbic acid for 1 minute and 0.3% for 3 minutes, and 5 and 10% sodium bicarbonate for 1 minute. For all treatments, color analysis, walnut moisture, sensory analysis of odor, taste and texture were carried out. Walnuts were bleached superficially after drying. The results indicate that the best treatment for bleaching macadamia nut is ascorbic acid at 0.3%, with this it is possible to add a more homogeneous and natural color to the nut, free of blackish spots.
Abstract
Macadamia nut is considered "the queen of nuts", because of its high energy content and nutritional value. Certain types of nuts are considered to be non-commercial due to [...]
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Influence of the seaweed Ascophyllum nodosum as a growth promoter in the stage of rainbow trout (Oncorhynchus mykiss)
D. López, I. Naranjo, O. Pérez, V. Uday

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 11

Abstract
The quality of the algae Ascphyllum nodosum was assessed as a growth promoter in the breeding stage of Rainbow Trout (Oncorhynchus mykiss) and its immunostimulant effect with regard to fungal diseases as the Saprolegnia sp. 6000 fingerlings of 77 days of age were used, with an average weight of 0.15 g, distributed under a DCA. For the analysis of the results, it was applied the analysis of variance and separation of averages (Duncan to p
Abstract
The quality of the algae Ascphyllum nodosum was assessed as a growth promoter in the breeding stage of Rainbow Trout (Oncorhynchus mykiss) and its immunostimulant effect with [...]
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Risk assessment and modeling of technical solutions for filtrations earth dams
M. Álvarez González, L. Álvarez Gil, R. Vázquez Rodríguez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 10

Abstract
The paper presents the evaluation and the analysis of three types of filter geometry to evaluate the filtration risk in Zaza Reservoir, taking as starting point the historic characteristics of the fluctuation of water levels inside the earth dam. The work is based on the experience of a multidisciplinary team and previous research with bi-dimensional models, using the Finite Elements Method for the solution of basic engineering problems. Also, the results of the installation of a new filter system with a geospatial index are evaluated (under criteria of threats, vulnerability, and risk) with spatial visualization data in a Geographical Information System for thematic maps generation, that represent how much the water level varies inside the dam according to the different filters evaluated.
Abstract
The paper presents the evaluation and the analysis of three types of filter geometry to evaluate the filtration risk in Zaza Reservoir, taking as starting point the historic [...]
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An Hybrid Genetic Algorithm to Optimization of Flow Shop Scheduling Problems under Real Environments Constraints
R. Najarro, R. López, R. Racines, A. Puris

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 9

Abstract
This paper aims to analyzing the effect of the inclusion of several constraints that have negative influence in the real manufacturing productions. For the solution of the scheduling problem treated in this paper, known as Flow Shop Scheduling, an efficient Genetic Algorithm is introduced combined with the Variable Neighborhood Search for problems of n tasks and m machines minimizing the total completion time or makespan. Release date, dependent setup-times and transport times are entered. These are common restrictions that can be found in multiple manufacturing environments where there are machines, tools, and a set of jobs must be processed in these, following the same flow pattern. The computational experiments carried out on a set of instances of problems of different sizes of complexity show that the proposed hybrid metaheuristic achieves high quality solutions comparable to the optimum ones reported.
Abstract
This paper aims to analyzing the effect of the inclusion of several constraints that have negative influence in the real manufacturing productions. For the solution of the [...]
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Use of distributed ledger technology by central banks: A review
C. Del Río

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (4), 8

Abstract
This paper reviews what stage the central banks of the world’s leading economies are at in their study and adoption of distributed ledger technology (DLT) to reengineer their various systems and functions. A brief description of DLT will be given, followed by an analysis of central banks’ publications and pronouncements to determine what each central bank is doing on their journey to DLT adoption. It was found that of the central banks for which information was available, all of them have expressed interest in DLT and have evaluated it to some extent. Nevertheless, no central bank has an operational DLT-based system at this point. This is because some issues remain regarding the speed, cost of processing, security, transparency and privacy, legal settlement finality, scalability and network effects of the technology. As DLT matures, the expectation is that these issues will begin to be resolved.
Abstract
This paper reviews what stage the central banks of the world’s leading economies are at in their study and adoption of distributed ledger technology (DLT) to reengineer [...]
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Applied geostatistics for reservoir characterization: High Resolution Cells based model
G. Cerón López

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 7

Abstract
Is it easy to use geostatistics for reservoir characterization or not? Is SGEMS able to reproduce reservoir geological characteristics in a 3D high resolution model? After years, Geostatistics has been allowing high resolution models generation to increase reservoir lithological detail. This work presents a straightforward methodology to create a facies model conditioned with the porosity model. Therefore, Open source geostatistics software was used to interpolate data. Rock type and porosity data, obtained from 26 well-logs of the Oriente Basin, were loaded in SGEMS. A high vertical and areal resolution 3D grid was built. Finally, 20 facies and porosity equiprobable models were generated. The model that better represents the reservoir characteristics was selected. The result is a high-resolution grid that represents the porosity conditioned to a facies model.
Abstract
Is it easy to use geostatistics for reservoir characterization or not? Is SGEMS able to reproduce reservoir geological characteristics in a 3D high resolution model? After [...]
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Evaluation of extraction of fatty acids from sardine’s head (Opisthonema libertate) by-product of fishing industry
B. Carrillo, M. Mosquera

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 6

Abstract
Polyunsaturated fatty acids are bioactive compounds employed as nutritional supplements in the food and pharmaceutical industry, those are present in blue fish like sardine (Opisthonema libertate). The purpose of this investigation was the recovery of these acids from sardine heads. A basic hydrolysis was carried out in order to extract the oil. NaOH was the hydrolyzing agent, tested in four concentrations. As a result, 3.64 % was the highest percentage of saponified oil recovery, with a concentration of 1M NaOH. This base allowed simultaneously saponify the recovered oil in the extraction. The influence of temperature and the concentration of H2SO4 in the isolation of fatty acids by the acidulation process was analyzed. The best experimental condition of the process was given at 20 °C and 75 % of H2SO4 concentration in the extracted oil, it was determined 2233.70 μg/mL of fatty acids, where 82.55% corresponded to saturated fatty acids, 13.72% to monounsaturated acids and 3.73% to polyunsaturated acids. Among the polyunsaturated fatty acids, was emphasized the presence of eicosapentaenoic acid EPA (omega-3) with a concentration of 73.12 μg/mL.
Abstract
Polyunsaturated fatty acids are bioactive compounds employed as nutritional supplements in the food and pharmaceutical industry, those are present in blue fish like sardine [...]
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Extraction purification and characterization of trypsin inhibitors from Andean seeds
P. Castillo, L. Quinchuela, P. Echeverría, G. Jácome

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 5

Abstract
This work established the conditions of covalent immobilization of trypsin on a Sepharose matrix, which could be applied for the purification of trypsin inhibitors. The higher values of retention of enzymatic activity and immobilized enzymatic activity were obtained with a Sepharose 6B-CL matrix, at room temperature, a pH value of 10.5, an enzymatic load of 25 mg/mL, and a minimum immobilization time of 12 hours, in order to obtain a stable immobilization. The most active trypsin inhibitors were selected through the comparison of, extracts obtained from the seeds of amaranth (Amaranthus caudatus L.), pea (Pisum sativum), lupine or “chocho” (Lupinus mutabilis), bean (Phaseolus vulgaris) and “sangorache” (Amaranthus hybridus L.). The inhibitors were partially purified using centrifugal ultrafiltration, heat treatment, and TCA precipitation. The permeated and retained fractions of “sangorache” were selected as the most active trypsin inhibitors, and they were selectively purified using affinity chromatography in a Trypsin - Glyoxyl - Sepharose 6B-CL matrix. The kinetic characterization showed the presence of two inhibitors; the first one corresponded to a competitive inhibitor, while the second one behaved as a mixed inhibitor.
Abstract
This work established the conditions of covalent immobilization of trypsin on a Sepharose matrix, which could be applied for the purification of trypsin inhibitors. The higher [...]
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Towards the construction of a device to support blind people in the “cuarenta” game
H. Ortega, R. Tufiño, J. Estévez

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 4

Abstract
The present work has the objective of developing a system for the automatic recognition of a playing card on a table, as part of a more general project to create a device to assist the blind in the chance game called “cuarenta”. The aim of this device will be to inform the user about the cards being played, via audio. For this phase of the project the algorithm used was k-NN, trained with a set of alphanumeric synthetic characters. The test set contained photographs taken in controlled lighting conditions, with the card positioned in arbitrary orientations. The parameterization of the algorithm gave a value of 1 as the optimal k, with which a classification error of 5% was obtained in the test set. Only two characters were confused by the classifier, the “A” and the “J”, with 20% and 40% errors each one. The algorithm was implemented in an embedded Raspberry Pi 3 system, obtaining a response time of 5 seconds, including the conversion to audio, and a memory occupation no greater than 60% of the total capacity of the system. These results suggest its applicability in portable devices.
Abstract
The present work has the objective of developing a system for the automatic recognition of a playing card on a table, as part of a more general project to create a device [...]
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Overhead impact on ad hoc mobile networks
P. Ludeña-González, R. Torres, M. Quiñónez, S. Cueva

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 3

Abstract
Overhead quantifies how much routing and control information is necessary for the application data to reach the destination node. This is very important in Ad Hoc networks because the mobility of nodes makes routing paths change constantly, therefore, the exchange of control and routing information increases. In this work the overhead for AODV, BCHP and DSVD mobile routing protocols is analyzed. Protocol reliability is used like a metric based on overhead behavior. The results show that the overhead can be between 30% to 60% with respect to the total throughput. BCHP is the most effective protocol because with similar expected overhead it has a better level of application information delivered.
Abstract
Overhead quantifies how much routing and control information is necessary for the application data to reach the destination node. This is very important in Ad Hoc networks [...]
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Thermal projection shielding in teeth flanks of a sugar cane mill drainer of a sugar factory
S. Espín Lagos, J. Guamanquispe Toasa, D. Coello-Fiallos, J. Paredes Zumbana

Enfoque UTE - Scientific Engineering Journal (2017). Vol. 8, (3), 2

Abstract
Shielding was performed on the flanks of teeth of a cane mill by means of the flame thermal projection technique using the Eutalloy 11496 micropulverized alloy. The material of the toner is AISI 1045 steel and the surface of shielding was prepared by the jet process with abrasive material of volcanic nature, in order to achieve an optimum anchorage surface for the alloy. Next, in software, iterations of the thickness of the shield were realized with the purpose of determining its useful life and through the distribution of Weibull we estimated the function of reliability and the function of probability of failure, considering a complete harvest of 240 days.
Abstract
Shielding was performed on the flanks of teeth of a cane mill by means of the flame thermal projection technique using the Eutalloy 11496 micropulverized alloy. The material [...]
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A finite element model for fluid–structure interaction problems involving closed membranes, internal and external fluids
P. Ryzhakov, E. Oñate

Comput. Methods Appl. Mech. Engrg., (2017). Vol. 326, pp. 422-445

Abstract
In this paper we propose a Finite Element model for analyzing closed membranes (“bags”) interacting with internal and external (surrounding) fluids. The approach is based on embedding a Lagrangian monolithic model describing the membrane containing an internal fluid into an Eulerian external fluid model. The combination of kinematic frameworks allows us to accurately track the location of the membrane and naturally represent flow variables discontinuities across it. In order to obtain stable coupling for membrane materials with low density, a slight fluid compressibility is assumed. The coupling between the membrane and the internal fluid is automatically accounted for by a monolithic set-up. The filled membrane and the external fluid are coupled in a Dirichlet–Neumann fashion. The model is validated in several numerical examples and its potential application to a civil engineering problem of coast protection via water-filled bag reefs is shown.
Abstract
In this paper we propose a Finite Element model for analyzing closed membranes (“bags”) interacting with internal and external (surrounding) fluids. The approach [...]
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PFEM formulation for thermo-coupled FSI analysis. Application to nuclear core melt accident
A. Franci, E. Oñate, J. Carbonell, M. Chiumenti

Comput. Methods Appl. Mech. Engrg., (2017). Vol. 325, pp. 711-732

Abstract
The aim of this paper is to present a Lagrangian formulation for thermo-coupled fluid–structure interaction (FSI) problems and to show its applicability to the simulation of hypothetical scenarios of a nuclear core melt accident. During this emergency situation, an extremely hot and radioactive lava-like material, the corium, is generated by the melting of the fuel assembly. The corium may induce collapse of the nuclear reactor devices and, in the worst case, breach the reactor containment and escape into the environment. This work shows the capabilities of the proposed formulation to reproduce the structural failure mechanisms induced by the corium that may occur during a meltdown scenario. For this purpose, a monolithic method for FSI problems, the so-called Unified formulation, is here enhanced in order to account for the thermal field and to model phase change phenomena with the Particle Finite Element Method (PFEM). Several numerical examples are presented. First, the convergence of the thermo-coupled method and phase change algorithm is shown for two academic problems. Then, two complex simulations of hypothetical nuclear meltdown situations are studied in 2D as in 3D.
Abstract
The aim of this paper is to present a Lagrangian formulation for thermo-coupled fluid–structure interaction (FSI) problems and to show its applicability [...]
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A FIC-based stabilized finite element formulation for turbulent flows
J. Cotela-Dalmau, R. Rossi, E. Oñate

Comput. Methods Appl. Mech. Engrg., (2017). (preprint) Vol. 315, pp. 607-631

Abstract
We present a new stabilized finite element (FEM) formulation for incompressible flows based on the Finite Increment Calculus (FIC) framework (Oñate, 1998). In comparison to existing FIC approaches for fluids, this formulation involves a new term in the momentum equation, which introduces non-isotropic dissipation in the direction of velocity gradients. We also follow a new approach to the derivation of the stabilized mass equation, inspired by recent developments for quasi-incompressible flows (Oñate et al., 2014). The presented FIC-FEM formulation is used to simulate turbulent flows, using the dissipation introduced by the method to account for turbulent dissipation in the style of implicit large eddy simulation.
Abstract
We present a new stabilized finite element (FEM) formulation for incompressible flows based on the Finite Increment Calculus (FIC) framework (Oñate, [...]
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Generalized parametric solutions in Stokes flow
P. Diez, S. Zlotnik, A. Huerta

Comput. Methods Appl. Mech. Engrg. (2017). (Preprint) Vol. 326, pp. 223-240

Abstract
Design optimization and uncertainty quantification, among other applications of industrial interest, require fast or multiple queries of some parametric model. The Proper Generalized Decomposition (PGD) provides a separable solution, a computational vademecum explicitly dependent on the parameters, efficiently computed with a greedy algorithm combined with an alternated directions scheme and compactly stored. This strategy has been successfully employed in many problems in computational mechanics. The application to problems with saddle point structure raises some difficulties requiring further attention. This article proposes a PGD formulation of the Stokes problem. Various possibilities of the separated forms of the PGD solutions are discussed and analyzed, selecting the more viable option. The efficacy of the proposed methodology is demonstrated in numerical examples for both Stokes and Brinkman models.
Abstract
Design optimization and uncertainty quantification, among other applications of industrial interest, require fast or multiple queries of some parametric model. The Proper [...]
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A semi‐analytical scheme for highly oscillatory integrals over tetrahedra
R. Hospital-Bravo, J. Sarrate, P. Diez

Comput. Methods Appl. Mech. Engrg., (2017). (Preprint) Vol. 111 (8), pp. 703-723

Abstract
This paper details a semi‐analytical procedure to efficiently integrate the product of a smooth function and a complex exponential over tetrahedral elements. These highly oscillatory integrals appear at the core of different numerical techniques. Here, the partition of unity method enriched with plane waves is used as motivation. The high computational cost or the lack of accuracy in computing these integrals is a bottleneck for their application to engineering problems of industrial interest. In this integration rule, the non‐oscillatory function is expanded into a set of Lagrange polynomials. In addition, Lagrange polynomials are expressed as a linear combination of the appropriate set of monomials, whose product with the complex exponentials is analytically integrated, leading to 16 specific cases that are developed in detail. Finally, we present several numerical examples to assess the accuracy and the computational efficiency of the proposed method, compared with standard Gauss–Legendre quadratures.
Abstract
This paper details a semi‐analytical procedure to efficiently integrate the product of a smooth function and a complex exponential over tetrahedral elements. These highly [...]
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Monitoring a PGD solver for parametric power flow problems with goal-oriented error assessment
R. García-Blanco, D. Borzacchiello, F. Chinesta, P. Diez

Int. J. Numer. Meth. Engng. (2017). Vol. 111 (6), pp. 529-552

Abstract
The parametric analysis of electric grids requires carrying out a large number of Power Flow computations. The different parameters describe loading conditions and grid properties. In this framework, the Proper Generalized Decomposition (PGD) provides a numerical solution explicitly accounting for the parametric dependence. Once the PGD solution is available, exploring the multidimensional parametric space is computationally inexpensive. The aim of this paper is to provide tools to monitor the error associated with this significant computational gain and to guarantee the quality of the PGD solution. In this case, the PGD algorithm consists in three nested loops that correspond to 1) iterating algebraic solver, 2) number of terms in the separable greedy expansion and 3) the alternated directions for each term. In the proposed approach, the three loops are controlled by stopping criteria based on residual goal-oriented error estimates. This allows one for using only the computational resources necessary to achieve the accuracy prescribed by the end- user. The paper discusses how to compute the goal-oriented error estimates. This requires linearizing the error equation and the Quantity of Interest to derive an efficient error representation based on an adjoint problem. The efficiency of the proposed approach is demonstrated on benchmark problems.
Abstract
The parametric analysis of electric grids requires carrying out a large number of Power Flow computations. The different parameters describe loading conditions and grid properties. [...]
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Enhanced goal-oriented error assessment and computational strategies in adaptive reduced basis solver for stochastic problems
K. Serafin, B. Magnain, E. Florentin, N. Parés, P. Diez

Int. J. Numer. Meth. Engng. (2017). (Preprint) Vol. 110 (5), pp. 440-466

Abstract
This work focuses on providing accurate low-cost approximations of stochastic finite elements simulations in the framework of linear elasticity. In [E. Florentin, P. Diez, Adaptive reduced basis strategy based on goal oriented error assessment for stochastic problems, Comput. Methods Appl. Mech. Engrg. 225-228 (2012) 116-127], an adaptive strategy has been introduced as an improved Monte-Carlo method for multi-dimensional large stochastic problems. We provide here a complete analysis of the method including a new enhanced goal-oriented error estimator and estimates of CPU cost gain. Technical insight of these two topics are presented in details and numerical examples show the interest of these new developments.
Abstract
This work focuses on providing accurate low-cost approximations of stochastic finite elements simulations in the framework of linear elasticity. In [E. Florentin, P. Diez, [...]
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Proper generalized decomposition solution of the parameterized Helmholtz problem: application to inverse geophysical problems
M. Signorini, S. Zlotnik, P. Diez

Int. J. Numer. Meth. Engng. (2017). (Preprint) Vol. 109, (8), pp. 1085-1102

Abstract
The identification of the geological structure from seismic data is formulated as an inverse problem. The properties and the shape of the rock formations in the subsoil are described by material and geometric parameters, which are taken as input data for a predictive model. Here, the model is based on the Helmholtz equation, describing the acoustic response of the system for a given wave length. Thus, the inverse problem consists in identifying the values of these parameters such that the output of the model agrees the best with observations. This optimization algorithm requires multiple queries to the model with different values of the parameters. Reduced order models are especially well suited to significantly reduce the computational overhead of the multiple evaluations of the model. In particular, the proper generalized decomposition produces a solution explicitly stating the parametric dependence, where the parameters play the same role as the physical coordinates. A proper generalized decomposition solver is devised to inexpensively explore the parametric space along the iterative process. This exploration of the parametric space is in fact seen as a post‐process of the generalized solution. The approach adopted demonstrates its viability when tested in two illustrative examples.
Abstract
The identification of the geological structure from seismic data is formulated as an inverse problem. The properties and the shape of the rock formations in the subsoil are [...]
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A new equilibrated residual method improving accuracy and efficiency of flux-free error estimates
N. Parés, P. Diez

Comput. Methods Appl. Mech. Engrg., (2017). (Preprint) Vol. 313 (1), pp. 785-816

Abstract
This paper presents a new methodology to compute guaranteed upper bounds for the energy norm of the error in the context of linear finite element approximations of the reaction-diffusion equation. The new approach revisits the ideas in [20, 18] with the goal of substantially reducing the com- putational cost of the flux-free method while retaining the good quality of the bounds. The new methodology provides also a technique to compute equilibrated boundary tractions improving the quality of standard equilibration strategies. The zeroth-order equilibration conditions are imposed using an alternative less restrictive form of the first-order equilibration conditions, along with a new efficient minimization criterion. This new equilibration strategy provides much more accurate up- per bounds for the energy and requires only doubling the dimension of the local linear systems of equations to be solved.
Abstract
This paper presents a new methodology to compute guaranteed upper bounds for the energy norm of the error in the context of linear finite element approximations of the reaction-diffusion [...]
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Background of Lara State cardiovascular program
R. Flores, S. Trujillo

Rev Vzlana Salud Pub (2017). 27

Abstract
Since the beginning of Cardiology in the world and then started as specialty in Venezuela history have occurred various events that influenced the development of the Cardiovascular Program in Venezuela created to become a national response to cardiovascular disease as a public health problem. In this context, this historical note particular places emphasis on the commencement of the Cardiovascular Program in Lara State, taking into account the set of individual and institutional situations that gave the necessary momentum, before 1976, for its establishment. In accordance with the foregoing, this factual account is intended to understand the evolution of the program in the region, which, following the same doctrinal basis of the national proposal and implementing different strategies, has achieved its permanence in time. By the way of closure, in the historical note, the strengths of the Cardiovascular Program in the state of Lara, Which through time have allowed it to consolidate itself as a unique and successful experience in the country, namely, the organized participation of the community, the link with the doctrinal issues, the organization and articulation of services by levels of resolution capacity, The teaching-assistance linkage, complementary sources of program financing and teamwork.
Abstract
Since the beginning of Cardiology in the world and then started as specialty in Venezuela history have occurred various events that influenced the [...]
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Internal communication and organizational climate in the management of health institutions
T. Vizcaya, M. Mujica, R. Gásperi

Rev Vzlana Salud Pub (2017). 26

Abstract
The organizational climate of health institutions is affected by many factors, such as leadership style, the level of motivation that exists, the way decisions are made and especially the type of communication that predominates. Internal communication is a real response to growing organizational complexity, however; the tendency is to recognize dialogic communication as a dimension and as a tool to achieve effectiveness in the organizational plan of the health institution. This is designated as internal communication version 2.0, which is the second generation of communication, in which the recognition of the interlocutor predominates. In this article, internal communication and the organizational climate in the management of health institutions were analyzed through a review of publications that discuss these issues. As inclusion criteria were used thematic coherence, timeliness of the source and indexation of the same. Consultation of the primary sources was done using databases. It was concluded that management combined with organizational climate and communication allow the interaction between its members, exchange and dialogue, in order to guide the processes that determine the behavior of the collective and the health organization.
Abstract
The organizational climate of health institutions is affected by many factors, such as leadership style, the level of motivation that exists, the way decisions are made and [...]
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Frequency of depression and risk factors associated with students from first to eight semester in a decanate of UCLA, january-may 2013
E. Nur, E. Pulgar, I. Piñero, M. Mendoza, M. Paredes, M. Morales, O. Ortiz, Y. Pernalete, D. Daza

Rev Vzlana Salud Pub (2017). 25

Abstract
Depression occupies one of the first places as a reason for consultation in psychiatry, with university students being one of the groups most affected. The objective of this investigation was to determine the frequency of depression and associated risk factors in students from the first to the eighth semester in a UCLA Deanery January-May 2013. A cross-sectional, observational analytical study was carried out, In 230 students, 149 females and 81 males. Data collection included a self-administered questionnaire for the measurement of risk factors, validated by experts, and the Beck Depression Inventory of 21 items. It was evidenced that there are 22.6% of depressed students, of whom 20.0% correspond to mild depression and 2.6% to moderate depression. There was a higher frequency of depression in the female sex (25.3%); In students over 20 years old (24.2%); In foreigners (28.1%); In students from the III and VII semesters (29.4% and 34.8%, respectively). In students with regular academic performance, 36.2% (p = 0.0001) of depression was observed; In those who do not share quality time with their family, 50% were evidenced (p = 0.0000); 44.4% (p = 0.000) and 50% (p = 0.007), respectively. Likewise, there is a 35.7% depression rate in students who have poor teacher-student relationships (p = 0.0007), with no respect (p = 0.021) and equity (p = 0.003). Likewise, 28.9% of students with depression have a poor relationship with their classmates. In conclusion, there is a significant percentage of depressed students, mild depression prevailing in them, however, non-depressed students present some risk factors. This paper aims to serve as a pioneer in the aforementioned campus for other research since there is little information on the subject
Abstract
Depression occupies one of the first places as a reason for consultation in psychiatry, with university students being one of the groups most affected. The objective of this [...]
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Cardiac structural alterations in obese patients with or without metabolic syndrome and other cardiovascular risk factors.
I. Ramones, R. Cammarata, B. Canache, B. Pacheco

Rev Vzlana Salud Pub (2017). 24

Abstract
Obesity has become a serious health problem worldwide, being an independent risk factor for cardiovascular disease. In that sense, to evaluate the frequency of cardiac geometric alterations in obese patients with or without metabolic syndrome and other CV risk factors, a study was performed in 28 obese participants and 13 non-obese who went voluntarily to the Clinical Pharmacology Unit of the Dean of Health Sciences of UCLA who were given a questionnaire to determine other CV risk factors and had the following tests: triglycerides , Total and fractionated cholesterol, creatinine, fasting glycemia and insulin using the ELISA technique, and a transthoracic echocardiogram. The obese, sedentary population as a whole, showed significantly higher values in the dimensions of the interventricular septum (SVI), posterior wall of the left ventricle (PPVI), and left atrial diameter (AI); 25% of the obese population presented concentric remodeling and 4% had eccentric hypertrophy. 32.14% of the obese presented metabolic syndrome, 64.29% dyslipidemia, 21% arterial hypertension and 28.57% smoking habits. Conclusions: Mild left ventricular morphologic alterations were found in obese patients, the presence of smoking habits in males exacerbates such alterations Keywords: Obesity, Cardiovascular Risk Factors, ventricular geometry
Abstract
Obesity has become a serious health problem worldwide, being an independent risk factor for cardiovascular disease. In that sense, to evaluate the frequency of cardiac geometric [...]
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Rhodnius pictipes naturally infected with Beauveria bassiana invading an urban domicile in Trujillo, Venezuela
Y. Ruiz, L. Avendaño, L. Cañizales, M. Oviedo, C. Guedez, J. Suarez, A. González

Rev Vzlana Salud Pub (2017). 23

Abstract
The objectives of this work were the identification of a triatomine captured within a home located at 9 ° 17'2 "LN and 70 ° 25¨49" LO in the capital city of Trujillo State and the characterization of an entomopathogenic fungus found on the Integument and articulations of the captured specimen. For the isolation of the entomopathogen the insect was placed in a humid chamber for four days for a greater sporulation and for the development and isolation was used potato, Dextrose, Agar (PDA) culture medium. On the basis of the morphological characteristics of the specimen studied, these correspond to Rhodnius pictipes according to the pictorial key of triatomines (Hemiptera: Triatominae) from Venezuela. No eggs or nymphs were found inside the house to discuss possible colonization. As for the fungus, this was characterized as Beauveriabassiana whose characteristics are more noticeable its pattern of development of white color, turning to a yellowish coloration on the back of the plates, with conidiogenic globose to sub globose cells. In this work, we refer for the first time to the state Trujillo, Venezuela the invasion of Rhodnius pictipes to a house and its infestation with the entomopatógeno Beauveria bassiana.
Abstract
The objectives of this work were the identification of a triatomine captured within a home located at 9 ° 17'2 "LN and 70 ° 25¨49" LO in the capital city of Trujillo State [...]
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Psychosocial risks assesment on Lara State workers
C. Carpintero, L. Lozada

Rev Vzlana Salud Pub (2017). 22

Abstract
A descriptive transversal investigation was conducted with the aim of evaluating the exposure to psycho-social risks in a stratified sample of 556 workers of the main areas of economic activities in Lara State, Venezuela. The questionnaire for evaluation of psychosocial risk in the workplace (ISTAS) was applied for the identification and measurement of exposure of workers to psychosocial demands related to claims about labor and control over job content. The results indicate that the proportion of workers exposed to situations most unfavourable to health is low (9% to 27%) prevailing dimensions of double presence and psychological demands. The rate exposure for intermediate situations is relatively high (55% to 69%) in the psychological demands dimension, active work, skill development and also compensation. Workers with higher exposures are those belonging to financial, insurance and real estate industries, shops, restaurants and hotels. The results from this study suggest that the workers whose activity involves customer interactions are exposed to higher psychological (cognitive and emotional) demands and they are limited to make decisions about their tasks, have almost no chance of skill development or control over their working time. Workers under community, social and personal service activities perceive that compensations received (stability and esteem) are not in accordance with their efforts. Social support and leadership was the dimension perceived as the most favorable for the health of all workers.
Abstract
A descriptive transversal investigation was conducted with the aim of evaluating the exposure to psycho-social risks in a stratified sample of 556 workers of the main areas [...]
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Importance of epidemiological reports
R. Gásperi

Rev Vzlana Salud Pub (2017). 21

Abstract
Los reportes epidemiológicos periódicos en Salud Publica son fundamentales para el buen desempeño de los sistemas de salud en un país. Los programas, planes de salud y la respectiva atención y resolución de estos problemas sanitarios ameritan de sistemas de información confiables y emitidos de forma periódica, continua y completa. Recientemente fue publicado en la página Web oficial del Ministerio del Poder Popular para la Salud, los Boletines Epidemiológicos Semanales de las 25 últimas semanas del año 2015 y de las 52 semanas del 2016, con una mora de casi dos años. En ellos llama la atención un aumento de la mortalidad materna del 2014 al 2015 del 15%, así como la aparición de 324 casos de difteria, reportados en el Boletín Epidemiológico Semanal número 52, patología no reportada en Boletines anteriores hasta el 2012. De igual manera se notifican 240.637 casos de malaria en 2015, con un aumento considerable tomando como referencia el 2012 cuando se reportaron 136.402 casos
Abstract
Los reportes epidemiológicos periódicos en Salud Publica son fundamentales para el buen desempeño de los sistemas de salud en un país. Los programas, planes de salud [...]
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NaWaraos, a contribution in public health
L. Valles

Rev Vzlana Salud Pub (2017). 20

Abstract
The Warao indigenous community in the Delta Amacuro state, Venezuela, without intending it, became historical internationally, when the English writer, Daniel Defoe, published in 1719, the adventures of Robinson Crusoe (autobiographical and fictional), considered the first English novel1; This pre-Columbian community, whose name comes from its own language: Wa, boat and Arao, people (canoe people), presented a series of public health needs (2-5) that motivated a diverse group of professionals, headed by the Doctors Raúl Arocha, Gerardo Sánchez, Gustavo Báez and Gloria Álvarez to place all their knowledge and skills in the solution of these diseases, is how the Non-Governmental Organization and apolitical "Na'Waraos" is created, which selects the population of Nabasanuka (Naba: pipe or river, and Sanuka: small) located at the geographic coordinates of LN 09 ° 08 '11.9 "and LO 061 ° 03'31.2", to be the epicenter of the control of endemic and epidemic diseases of its inhabitants and others 30 nearby towns such as Wisidatu, Joarotu, Bajanarotu and Araguabici
Abstract
The Warao indigenous community in the Delta Amacuro state, Venezuela, without intending it, became historical internationally, when the English writer, Daniel Defoe, published [...]
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Dengue risk factors study in juan guillermo iribarren municipality, Lara State.
Y. Ontiveros, X. Bullones, O. Cárdenas

Rev Vzlana Salud Pub (2017). 19

Abstract
Dengue es una de las arbovirosis más importantes en el mundo en términos de morbi-mortalidad. En América, destaca Venezuela donde son afectados niños, mujeres y hombres, en todos sus estados, en particular Lara, en el cual se desarrolló una investigación para determinar los factores de riesgo de dengue en cuatro parroquias del municipio Juan Guillermo Iribarren del estado en el año 2006. La muestra quedó constituida por 516 viviendas, se aplicó un cuestionario a los jefes de familia o persona mayor de edad de la vivienda seleccionada. Entre los resultados: la prevalencia de dengue fue 11,4% (IC95%:8,59 -14,23), en el grupo de edad de 1-29 años, 43,4% tuvo dengue (ORa =21, IC95%:10,7- 41,1), en el género femenino 15,3% fue afectado (ORa=1,9, IC95%: 0,9-3,5). Entre quienes desconocían sobre la transmisión de dengue, 13.3% lo padecieron (ORa=1,48, IC95%: 0,7-2,9). Con relación a las variables ambientales, se encontró que en las viviendas con presencia de criaderos de larvas de Aedes aegypti, 15,3% de los entrevistados presentaron dengue (ORa=2,1, IC95%: 1- 4,7). Los resultados evidenciaron que existe asociación significativa (c2; p
Abstract
Dengue es una de las arbovirosis más importantes en el mundo en términos de morbi-mortalidad. En América, destaca Venezuela donde son afectados niños, mujeres y [...]
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Measurement of the Wingbeart Frequency of the Aedes aegypti PROVENIENTS FROM A REGION OF VENEZUELA
Á. Daboín, L. Valles, F. Torrealba, T. Gharbi

Rev Vzlana Salud Pub (2017). 18

Abstract
In order to develop intelligent traps as vector control mechanisms for the prevention and reduction of metaxenic diseases, a physiological parameter is determined as the wingbeat frequency used for later characterization by genus of the Aedes aegypti mosquito in Venezuelan strains. For this, acoustic records were made with wild samples collected in rainwater reservoirs and emerged under controlled conditions in the laboratory. The recordings were made during one minute, in more than a hundred mosquitoes of this species and in both sexes, using a particle speed microphone connected to the audio input of a portable computer and a specialized program for acoustic records. A spectral analysis of the samples was carried out, determining that the average fundamental frequency of flutter for females corresponded to 454.78 ± 55.19 Hz and for males 688.39 ± 40.82 Hz, concluding that the groups were very separated in Its fundamental frequency, with which this parameter is a characteristic that can be used for the detection and classification of mosquitoes of this species, using artificial intelligence in capture devices for vector monitoring and control.
Abstract
In order to develop intelligent traps as vector control mechanisms for the prevention and reduction of metaxenic diseases, a physiological parameter is determined as the wingbeat [...]
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Microbiological and parasitological evaluation of fish of the species Mugil cephalus (lisa) commercialized in the city of Barquisimeto, Lara State.
N. Padilla, A. Arrollo, C. Márquez, M. Pineda

Rev Vzlana Salud Pub (2017). 17

Abstract
The rate of deterioration of fish and its safety are related to the hygienic management of the fish and its conditioning,consuming poorly cooked or raw fish can lead to food poisoning, hepatitis, cholera and parasitism. The dishesregularlyinvolved include sushi, sashimi and ceviche. The parasitic disease is caused by the larval phases of anematode of the family Anisakidae. The parasite develops as an adult in marine mammals that acquire the diseasethanks to the infective L3 form developed in fish. The human consumes poorly cooked fish and acquires L3 larva,causing gastric, intestinal and extraintestinal disease or a gastro-allergic modality. Fourty - five specimens ofMugilcephalus purchased in popular markets, refrigerators and stalls in the city of Barquisimeto were studied.Through the visual inspection we evaluated the freshness index and through microbiological analysis we detectedsanitary indicators, fecal contamination and pathogens. A recount of the larvae extracted during the visual inspectionand during in vitro digestion, the results indicate that the freshness of the specimens was 8.36 ± 3.28 points.Staphylococcus aureus appeared in 64.7% of the samples. The 82.2% of the specimens showed parasitism, with anaverage of 24.48 larvae per specimen. Microscopic examination of the parasites present structures that coincide withthe genus Anisakis. These larvae are foodborne, so that in the face of symptoms and history of consumption of theseproducts,its important to consider these parasites as etiological agentsof these diseases.
Abstract
The rate of deterioration of fish and its safety are related to the hygienic management of the fish and its conditioning,consuming poorly cooked or raw fish can lead to food [...]
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Prevalence of Burnout Syndrome, risk of exposure. medical attention. San Francisco Ambulatory. Barquisimeto. Lara State. 2016
K. Bastidas, Y. Coll, Y. Delgado, M. Escobar, D. Flores, Z. González, Á. Riera

Rev Vzlana Salud Pub (2017). 16

Abstract
In order to determine the prevalence of Burnout Syndrome, occupational risk to develop it in the health personnel and the user's opinion about on medical attention, a descriptive cross-sectional study was carried out in San Francisco's Type I Ambulatory. The sample consisted of 17 workers and 120 users. Two instruments were used to collect data addressed to health personnel: ISTAS questionnaire (CoPsoQ) 2000 short version and Maslach Burnout Inventory and a third questionnaire to users that measured opinion about medical care. For Psychosocial Risk in the staff, a favorable level was found in the categories active work and self-development possibilities with 88.2% as well as a social support and quality of leadership of 64.7%; the unfavorable level was presented in the categories insecurity 58.8%, double presence 47% and estimated 47%. Likewise, it was highlighted that no worker presented Burnout syndrome since the dimensions of personalization and depersonalization with 88.2% were located at a low level. In turn, 90.9% of the users felt totally satisfied with the medical care, deducting that the factors that contributed to feelings of exhaustion or stress did not influence the quality of care provided in the premises. This served to project new studies and make new references regarding the Burnout syndrome and its scope, giving the pertinent recommendations, both to the community and to the ambulatory staff to reduce the risks of developing the disease.
Abstract
In order to determine the prevalence of Burnout Syndrome, occupational risk to develop it in the health personnel and the user's opinion about on medical attention, [...]
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Antimicrobial activity of natural products against Helicobacter pylori
D. Zea, M. Bayona

Rev Vzlana Salud Pub (2017). 15

Abstract
Since its discovery and identification in gastric tissue by Marshall and Warren in 1983, our knowledge about the effects of Helicobacter pylori infection has grown considerably. Its role in the multifactorial pathology of peptic ulcer disease (gastroduodenal ulcer disease), gastric adenocarcinoma, is now widely accepted. Currently, numerous antibiotic-based therapies are available. However, these therapies have several problems, including the appearance of resistance to the antibiotics used and associated adverse effects, the risk of re-infection and the high cost of treatment. This paper summarizes and analyzes the most important recent studies of plants with anti H. pylori activity. Plants species are presented as a very diverse source of bactericidal compounds, as well as for the development of new therapies for H. pylori control.
Abstract
Since its discovery and identification in gastric tissue by Marshall and Warren in 1983, our knowledge about the effects of Helicobacter pylori infection has grown considerably. [...]
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Prevalnce of dengue in the Parist of “Lagunillas”, Sucre Muicipaly, Mérida State, 2005 – 2015.
Y. Paredes, J. Chipia, L. Contreras

Rev Vzlana Salud Pub (2017). 14

Abstract
Dengue is a viral disease that depends on interactions between environment, agent, population of hosts and vector, as well as socioeconomic, political, technical and administrative determinants. The article aims to describe the prevalence of dengue for the period 2005 to 2015 in the Lagunillas parish of the municipality of Sucre, Mérida, Venezuela. Methodology: quantitative approach, descriptive type and non-experimental longitudinal design. Results: 2947 cases of dengue were found between the years under study. The presence of dengue with signs of alarm was recorded in the last three years of the study period and for severe dengue, the highest incidence occurred in 2010 with 1,085 cases / 100,000 inhabitants, the standardized prevalence rate: 2005 13/1000 inhabitants, by 2010 28/1000 inhabitants and 2015 of 8/1000 inhabitants and the projection (2016-2025) of the cases of dengue, a relation was obtained directly proportional in the time series, as Years increase the casuistry of the disease. Conclusions: The Lagunillas parish of Mérida state presents a high prevalence of dengue, being classified as an epidemic zone. It was determined that in the years 2013-2015 the dengue with signs of alarm, has suffered an increase in its incidence, although it has not been determined the cause, it is very probable that local environmental phenomena, such as the water deficit, as well as the social context , May translate into an increase in the density of the dengue transmitter vector and an increase in the reporting of dengue cases.
Abstract
Dengue is a viral disease that depends on interactions between environment, agent, population of hosts and vector, as well as socioeconomic, political, technical and [...]
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Public health and social problems
R. Gásperi

Rev Vzlana Salud Pub (2017). 13

Abstract
Health conceived as a complex phenomenon constitutes a circuit where the effects retroact on the causes and the health disease process as a product, reproduces its causes in a reiterative way so its approach should not be made from a simplified but multidimensional and interdisciplinary logic. In the same way, the paradigm of complexity proposes to articulate the interdependencies of disciplinary or specialized knowledge, and conceives an organization or systemic complexity between the whole and the parts, which allows it to be capable of self-echo-reproduction and regeneration when relating to others. with its environment or environment. Under this approach, public health becomes a crucible where many disciplines can converge to understand and address the problems that affect the well-being of the population from that complex view of their environment that includes the physical, psychological, anthroposocial, spiritual, cultural and the politically and ideologically constructed
Abstract
Health conceived as a complex phenomenon constitutes a circuit where the effects retroact on the causes and the health disease process as a product, reproduces its causes [...]
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Variational Multiscale error estimators for solid mechanics adaptive simulations: An Orthogonal Subgrid Scale approach
J. Baiges, R. Codina

Comput. Methods Appl. Mech. Engrg., (2017). Vol. 325, pp. 37-55

Abstract
In this work we present a general error estimator for the finite element solution of solid mechanics problems based on the Variational Multiscale method. The main idea is to consider a rich model for the subgrid scales as an error estimator. The subscales are considered to belong to a space orthogonal to the finite element space (Orthogonal Subgrid Scales) and we take into account their contribution both in the element interiors and on the element boundaries (Subscales on the Element Boundaries). A simple analysis shows that the upper bound for the obtained error estimator is sharper than in other error estimators based on the Variational Multiscale Method. Numerical examples show that the proposed error estimator is an accurate approximation for the energy norm error and can be used both in simple linear constitutive models and in more complex non-linear cases.
Abstract
In this work we present a general error estimator for the finite element solution of solid mechanics problems based on the Variational Multiscale method. [...]
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Interpolation with restrictions between finite element meshes for flow problems in an ALE setting
A. Pont, R. Codina, J. Baiges

Comput. Methods Appl. Mech. Engrg., (2017). Vol. 110 (13), pp. 1203-1226

Abstract
The need for remeshing when computing flow problems in domains suffering large deformations has motivated the implementation of a tool that allows the proper transmission of information between finite element meshes. Because the Lagrangian projection of results from one mesh to another is a dissipative method, a new conservative interpolation method has been developed. A series of constraints, such as the conservation of mass or energy, are applied to the interpolated arrays through Lagrange multipliers in an error minimization problem, so that the resulting array satisfies these physical properties while staying as close as possible to the original interpolated values in the L2 norm. Unlike other conservative interpolation methods that require a considerable effort in mesh generation and modification, the proposed formulation is mesh independent and is only based on the physical properties of the field being interpolated. Moreover, the performed corrections are neither coupled with the main calculation nor with the interpolation itself, for which reason the computational cost is very low.
Abstract
The need for remeshing when computing flow problems in domains suffering large deformations has motivated the implementation of a tool that allows the proper transmission [...]
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Numerical analysis of a stabilized finite element approximation for the three-field linearized viscoelastic fluid problem using arbitrary interpolations
E. Castillo, R. Codina

Mathematical Models and Methods in Applied Sciences (2017). Vol. 51 (4), pp. 1407-1427

Abstract
In this paper we present the numerical analysis of a three-field stabilized finite element formulation recently proposed to approximate viscoelastic flows. The three-field viscoelastic fluid flow problem may suffer from two types of numerical instabilities: on the one hand we have the two inf-sup conditions related to the mixed nature problem and, on the other, the convective nature of the momentum and constitutive equations may produce global and local oscillations in the numerical approximation. Both can be overcome by resorting from the standard Galerkin method to a stabilized formulation. The one presented here is based on the subgrid scale concept, in which unresolvable scales of the continuous solution are approximately accounted for. In particular, the approach developed herein is based on the decomposition into their finite element component and a subscale, which is approximated properly to yield a stable formulation. The analyzed problem corresponds to a linearized version of the Navier–Stokes/Oldroyd-B case where the advection velocity of the momentum equation and the non-linear terms in the constitutive equation are treated using a fixed point strategy for the velocity and the velocity gradient. The proposed method permits the resolution of the problem using arbitrary interpolations for all the unknowns. We describe some important ingredients related to the design of the formulation and present the results of its numerical analysis. It is shown that the formulation is stable and optimally convergent for small Weissenberg numbers, independently of the interpolation used.
Abstract
In this paper we present the numerical analysis of a three-field stabilized finite element formulation recently proposed to approximate viscoelastic flows. The three-field [...]
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An adaptive Fixed-Mesh ALE method for free surface flows
J. Baiges, R. Codina, A. Pont, E. Castillo

Comput. Methods Appl. Mech. Engrg., (2017). Vol. 313, pp. 159-188

Abstract
In this work we present a Fixed-Mesh ALE method for the numerical simulation of free surface flows capable of using an adaptive finite element mesh covering a background domain. This mesh is successively refined and unrefined at each time step in order to focus the computational effort on the spatial regions where it is required. Some of the main ingredients of the formulation are the use of an Arbitrary-Lagrangian–Eulerian formulation for computing temporal derivatives, the use of stabilization terms for stabilizing convection, stabilizing the lack of compatibility between velocity and pressure interpolation spaces, and stabilizing the ill-conditioning introduced by the cuts on the background finite element mesh, and the coupling of the algorithm with an adaptive mesh refinement procedure suitable for running on distributed memory environments. Algorithmic steps for the projection between meshes are presented together with the algebraic fractional step approach used for improving the condition number of the linear systems to be solved. The method is tested in several numerical examples. The expected convergence rates both in space and time are observed. Smooth solution fields for both velocity and pressure are obtained (as a result of the contribution of the stabilization terms). Finally, a good agreement between the numerical results and the reference experimental data is obtained.
Abstract
In this work we present a Fixed-Mesh ALE method for the numerical simulation of free surface flows capable of using an adaptive finite element mesh covering a background [...]
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Finite element approximation of the viscoelastic flow problem: A non-residual based stabilized formulation
E. Castillo, R. Codina

Computers & Fluids (2017). Vol. 142, pp. 72-78

Abstract
In this paper, a three-field finite element stabilized formulation for the incompressible viscoelastic fluid flow problem is tested numerically. Starting from a residual based formulation, a non-residual based one is designed, the benefits of which are highlighted in this work. Both formulations allow one to deal with the convective nature of the problem and to use equal interpolation for the problem unknowns σ−u−p (deviatoric stress, velocity and pressure). Additionally, some results from the numerical analysis of the formulation are stated. Numerical examples are presented to show the robustness of the method, which include the classical 4: 1 planar contraction problem and the flow over a confined cylinder case, as well as a two-fluid formulation for the planar jet buckling problem.
Abstract
In this paper, a three-field finite element stabilized formulation for the incompressible viscoelastic fluid flow problem is tested numerically. Starting from a residual based [...]
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Conserving algorithms for frictionless and full stick friction contact dynamic problems using the direct elimination method
C. Agelet de Saracibar, D. Di Capua

Int. J. Numer. Meth. Engng. (2017). (preprint) Vol. 113 (6), pp. 910-937

Abstract
In this paper, conserving time‐stepping algorithms for frictionless and full stick friction dynamic contact problems are presented. Time integration algorithms for frictionless and full stick friction dynamic contact problems have been designed to preserve the conservation of key discrete properties satisfied at the continuum level. Energy and energy‐momentum–preserving algorithms for frictionless and full stick friction dynamic contact problems, respectively, have been designed and implemented within the framework of the direct elimination method, avoiding the drawbacks linked to the use of penalty‐based or Lagrange multipliers methods. An assessment of the performance of the resulting formulation is shown in a number of selected and representative numerical examples, under full stick friction and slip frictionless contact conditions. Conservation of key discrete properties exhibited by the time‐stepping algorithm is shown.
Abstract
In this paper, conserving time‐stepping algorithms for frictionless and full stick friction dynamic contact problems are presented. Time integration algorithms for frictionless [...]
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The CIMNE model for generating knowledge on computational engineering and its transfer to society
E. Oñate

(2017). Research Report, Nº PI417

Abstract
We present an overview of the model implemented by the International Centre for Numerical Methods in Engineering (CIMNE, www.cimne.com ) for the generation of scientific and technical knowledge on computational engineering, understood in the broad sense, the subsequent generation of product resulting from the research activities and the transfer of these products to society for their exploitation in the industrial sector. We present examples of application of the CIMNE model to a number of academic, scientific and industry activities of CIMNE.
Abstract
We present an overview of the model implemented by the International Centre for Numerical Methods in Engineering (CIMNE, www.cimne.com ) for the generation of scientific [...]
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Early detection of anomalies in dam performance: A methodology based on boosted regression trees
F. Salazar, M. Toledo, J. González, E. Oñate

Structural Control Health Monitoring (2017). Vol. 24 (11), Article Number: e2012

Abstract
The advances in information and communication technologies led to a general trend towards the availability of more detailed information on dam behaviour. This allows applying advanced data‐based algorithms in its analysis, which has been reflected in an increasing interest in the field. However, most of the related literature is limited to the evaluation of model prediction accuracy, whereas the ulterior objective of data analysis is dam safety assessment. In this work, a machine‐learning algorithm (boosted regression trees) is the core of a methodology for early detection of anomalies. It also includes a criterion to determine whether certain discrepancy between predictions and observations is normal, a procedure to compute a realistic estimate of the model accuracy, and an original approach to identify extraordinary load combinations. The performance of causal and noncausal models is assessed in terms of their ability to detect different types of anomalies, which were artificially introduced on reference time series generated with a numerical model of a 100‐m‐high arch dam. The final approach was implemented in an online application to visualise the results in an intuitive way to support decision making.
Abstract
The advances in information and communication technologies led to a general trend towards the availability of more detailed information on dam behaviour. This allows applying [...]
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Discrete/finite element modelling of rock cutting with TBM disc cutter
C. Labra, J. Rojek, E. Oñate

Rock Mechanics and Rock Engineering (2017). Vol. 50 (3), pp. 621-638

Abstract
This paper presents advanced computer simulation of rock cutting process typical for excavation works in civil engineering. Theoretical formulation of the hybrid discrete/finite element model has been presented. The discrete and finite element methods have been used in different subdomains of a rock sample according to expected material behaviour, the part which is fractured and damaged during cutting is discretized with the discrete elements while the other part is treated as a continuous body and it is modelled using the finite element method. In this way, an optimum model is created, enabling a proper representation of the physical phenomena during cutting and efficient numerical computation. The model has been applied to simulation of the laboratory test of rock cutting with a single TBM (tunnel boring machine) disc cutter. The micromechanical parameters have been determined using the dimensionless relationships between micro- and macroscopic parameters. A number of numerical simulations of the LCM test in the unrelieved and relieved cutting modes have been performed. Numerical results have been compared with available data from in-situ measurements in a real TBM as well as with the theoretical predictions showing quite a good agreement. The numerical model has provided a new insight into the cutting mechanism enabling us to investigate the stress and pressure distribution at the tool–rock interaction. Sensitivity analysis of rock cutting performed for different parameters including disc geometry, cutting velocity, disc penetration and spacing has shown that the presented numerical model is a suitable tool for the design and optimization of rock cutting process.
Abstract
This paper presents advanced computer simulation of rock cutting process typical for excavation works in civil engineering. Theoretical formulation of the hybrid discrete/finite [...]
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An Implicit Material Point Method Applied to Granular Flows
I. Iaconeta, A. LARESE, R. Rossi, E. Oñate

Procedia Engineering (2017). Vol. 175, pp. 226-232

Abstract
The main objective of this work lies in the development of a variational implicit Material Point Method (MPM), implemented in the open source Kratos Multiphysics framework. The ability of the MPM technique to solve large displacement and large deformation problems is widely recognised and its use ranges over many problems in industrial and civil engineering. In the current work the continuum based implicit MPM is applied to engineering applications, where granular material flow is involved. For the resolution of the length and time scale of these particular problems, both continuum and discrete models are typically used. Even if discrete techniques predict more feasible results, nowadays, their use is limited to the investigation of element tests of particles, or to the simulation of reduced systems, not allowing to make important decisions in the analysis and design of granular processes. Some advantages of MPM over discrete methods are tested, such as, the ability to simulate granular flow at the large scale with acceptable computational cost and the capability to get information of stress and strain state in a more straightforward way. The focus of this paper is a comparative study between an irreducible and a mixed formulation, both implemented in the MPM code, to assess the improvement in accuracy and reliability of the numerical results when the latter formulation is adopted.
Abstract
The main objective of this work lies in the development of a variational implicit Material Point Method (MPM), implemented in the open source Kratos Multiphysics framework. [...]
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A FIC‐based stabilized mixed finite element method with equal order interpolation for solid–pore fluid interaction problems
I. de-Pouplana, E. Oñate

Int. J. Numer. Anal. Meth. Geomech. (2017). Vol. 41 (1), pp. 110-134

Abstract
A new mixed displacement‐pressure element for solving solid–pore fluid interaction problems is presented. In the resulting coupled system of equations, the balance of momentum equation remains unaltered, while the mass balance equation for the pore fluid is stabilized with the inclusion of higher‐order terms multiplied by arbitrary dimensions in space, following the finite calculus (FIC) procedure. The stabilized FIC‐FEM formulation can be applied to any kind of interpolation for the displacements and the pressure, but in this work, we have used linear elements of equal order interpolation for both set of unknowns. Examples in 2D and 3D are presented to illustrate the accuracy of the stabilized formulation for solid–pore fluid interaction problems.
Abstract
A new mixed displacement‐pressure element for solving solid–pore fluid interaction problems is presented. In the resulting coupled system of equations, the balance [...]
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Numerical modelling of granular materials with spherical discrete particles and the bounded rolling friction model. Application to railway ballast
J. Irazábal González, F. Salazar, E. Oñate

Computers and Geotechnics (2017). Vol. 85, pp. 220-229

Abstract
The Discrete Element Method (DEM) was found to be an effective numerical method for the calculation of engineering problems involving granular materials. However, the representation of irregular particles using the DEM is a very challenging issue, leading to different geometrical approaches. This document presents a new insight in the application of one of those simplifications known as rolling friction, which avoids excessive rotation when irregular shaped materials are simulated as spheric particles. This new approach, called the Bounded Rolling Friction model, was applied to reproduce a ballast resistance test.
Abstract
The Discrete Element Method (DEM) was found to be an effective numerical method for the calculation of engineering problems involving granular materials. [...]
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A hierarchical finite element for composite laminated beams using a refined zigzag theory
L. Nallim, S. Oller, E. Oñate, F. Flores

Composite Structures (2017). Vol. 163, pp. 168-184

Abstract
In this work a kinematics for laminated beams enriched with a refined formulation ZigZag (RZT), originally presented by Tessler et al. in 2007, introduced in a hierarchical one dimensional type “p” finite element is presented. The finite element employs Lagrange polynomials for the approximation of the degrees of freedom of the ends (nodes) and orthogonal Gram-Schmidt polynomials to the internal degrees of freedoms. This finite element allows a very low discretization, is free of shear locking and behaves very well when the analysis of laminated composites with accurate determination of local stresses and strains at laminar level is necessary. This element has been validated in the analysis of laminated beams with various sequences of symmetric and asymmetric stacking, studying in each case its accuracy and stability.
Abstract
In this work a kinematics for laminated beams enriched with a refined formulation ZigZag (RZT), originally presented by Tessler et al. in 2007, introduced in a hierarchical [...]
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Data-Based Models for the Prediction of Dam Behaviour: A Review and Some Methodological Considerations
F. Salazar, R. Morán Moya, M. Toledo, E. Oñate

Archives of Comp. Meths. Engng. (2017). Vol. 24 (1), pp. 1-21

Abstract
Predictive models are an important element in dam safety analysis. They provide an estimate of the dam response faced with a given load combination, which can be compared with the actual measurements to draw conclusions about dam safety. In addition to numerical finite element models, statistical models based on monitoring data have been used for decades for this purpose. In particular, the hydrostatic-season-time method is fully implemented in engineering practice, although some limitations have been pointed out. In other fields of science, powerful tools such as neural networks and support vector machines have been developed, which make use of observed data for interpreting complex systems . This paper contains a review of statistical and machine-learning data-based predictive models, which have been applied to dam safety analysis . Some aspects to take into account when developing analysis of this kind, such as the selection of the input variables, its division into training and validation sets, and the error analysis, are discussed. Most of the papers reviewed deal with one specific output variable of a given dam typology and the majority also lack enough validation data. As a consequence, although results are promising, there is a need for further validation and assessment of generalisation capability. Future research should also focus on the development of criteria for data pre-processing and model application.
Abstract
Predictive models are an important element in dam safety analysis. They provide an estimate of the dam response faced with a given load combination, which can be compared [...]
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Cracking of quasi-brittle structures under monotonic and cyclic loadings: A d+/d− damage model with stiffness recovery in shear
M. Cervera, C. Tesei, G. Ventura

Int. J. Solids and Structures (2017). (preprint) Vol. 135, pp. 148–171

Abstract
In the present paper, a new d+/d− damage model apt for quasi-brittle materials is described and its validation is carried out considering unreinforced concrete, reinforced concrete and masonry elements. Two independent scalar damage variables, d+ and d−, in combination with the split of the reversible strain tensor into its positive and negative counterparts, are adopted in order to simulate the pronounced dissimilar response under tension and compression, typical of these materials. An energy-equivalent framework is considered for representing the orthotropy induced in the material by the degradation process, with the consequence that a thermodynamically consistent constitutive operator, positive definite, symmetric and strain-driven, is derived. In addition to the degradation parameters, the permanent strain tensor is also contemplated by the model and a modification of the exponential softening modulus is proposed in order to treat the evolution of the two causes of dissipation, damage and irreversible deformations, in a coupled way. The formulation is integrated with a multidirectional damage procedure, addressed to extend the microcrack closure-reopening (MCR) capabilities of the model to shear cyclic conditions, characterized by orthogonal (or however intersecting) sets of cracks. Maintaining unaltered the dependence of the constitutive law from two scalar indeces, d+ and d−, this approach activates or deactivates a tensile(compressive) damage value on the base of the current maximum (minimum) principal strain direction. In correspondence with damage activation (crack opening) or deactivation (crack closure), a smooth transition is introduced, in order to avoid abrupt changes in stiffness and enhance the numerical performance and robustness of the multidirectional procedure. The adequacy of the proposed constitutive model in reproducing experimental results has been proven for both monotonic and cyclic loading conditions. The two examples of application involving cyclic loads, dominated by shear, constitute a validation of the multidirectional damage approach, showing how the suitable representation of unilateral effects and permanent deformations is essential to model the observed structural response in terms of maximum resistance, evolution of stiffness degradation and dissipation capacity.
Abstract
In the present paper, a new d+/d− damage model apt for quasi-brittle materials is described and its validation is carried out considering unreinforced [...]
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Experimental validation of a FSW model with an enhanced friction model: application to a threaded cylindrical pin tool
N. Dialami, M. Cervera, M. Chiumenti, A. Segatori, W. Osikowicz

Metals (2017). (preprint) Vol. 7 (11), pp. 491

Abstract
This work adopts a fast and accurate two-stage computational strategy for the analysis of FSW (Friction stir welding) processes using threaded cylindrical pin tools. The coupled thermo-mechanical problem is equipped with an enhanced friction model to include the effect of non-uniform pressure distribution under the pin shoulder. The overall numerical strategy is successfully validated by the experimental measurements provided by the industrial partner (Sapa). The verification of the numerical model using the experimental evidence is not only accomplished in terms of temperature evolution but also in terms of torque, longitudinal, transversal and vertical forces.
Abstract
This work adopts a fast and accurate two-stage computational strategy for the analysis of FSW (Friction stir welding) processes using threaded cylindrical pin tools. The coupled [...]
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Enhanced friction model for Friction Stir Welding (FSW) analysis: Simulation and experimental validation
N. Dialami, M. Chiumenti, M. Cervera, A. Segatori, W. Osikowicz

Int. J. Mechanical Sciences (2017). (preprint) Vol. 133, pp. 555-567

Abstract
Friction is one of the main heat generation mechanisms in Friction Stir Welding (FSW). This phenomenon occurs between the pin and the workpiece as the rotating tool moves along the weld line. An accurate friction model is essential for obtaining realistic results in a FSW simulation in particular temperature, forces and torque. In this work, a modified Norton's friction law is developed. The suggested enhanced friction model aims at providing not only the realistic temperature field but also the forces and torque. This model does not exclusively relate the frictional shear stress to the sliding velocity; conversely it takes into account the effect of non-uniform pressure distribution under the shoulder, as this latter has an important role in the process of heat generation. Longitudinal, transversal and vertical forces and torque are numerically calculated. The effect of the enhanced friction model is reflected in these forces. In particular, it leads to a more realistic estimation of the transversal and longitudinal forces in comparison with the results obtained using former models. The friction model is successfully validated by the experimental measurements provided by the industrial partner (Sapa). The experimental analysis is performed for the material characterization, the calibration of the friction model and, more generally, the assessment of the overall numerical strategy proposed for the FSW simulation.
Abstract
Friction is one of the main heat generation mechanisms in Friction Stir Welding (FSW). This phenomenon occurs between the pin and the workpiece as the rotating tool moves [...]
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Numerical modelling and experimental validation in Selective Laser Melting
M. Chiumenti, E. Neiva, E. Salsi, M. Cervera, E. Badia, J. Moya, Z. Chen, C. Lee, C. Davies

Additive Manufacturing (2017). (preprint) Vol. 18, pp. 171-185

Abstract
In this work a finite-element framework for the numerical simulation of the heat transfer analysis of additive manufacturing processes by powder-bed technologies, such as Selective Laser Melting, is presented. These kind of technologies allow for a layer-by-layer metal deposition process to cost-effectively create, directly from a CAD model, complex functional parts such as turbine blades, fuel injectors, heat exchangers, medical implants, among others. The numerical model proposed accounts for different heat dissipation mechanisms through the surrounding environment and is supplemented by a finite-element activation strategy, based on the born-dead elements technique, to follow the growth of the geometry driven by the metal deposition process, in such a way that the same scanning pattern sent to the numerical control system of the AM machine is used. An experimental campaign has been carried out at the Monash Centre for Additive Manufacturing using an EOSINT-M280 machine where it was possible to fabricate different benchmark geometries, as well as to record the temperature measurements at different thermocouple locations. The experiment consisted in the simultaneous printing of two walls with a total deposition volume of 107 cm3 in 992 layers and about 33,500 s build time. A large number of numerical simulations have been carried out to calibrate the thermal FE framework in terms of the thermophysical properties of both solid and powder materials and suitable boundary conditions. Furthermore, the large size of the experiment motivated the investigation of two different model reduction strategies: exclusion of the powder-bed from the computational domain and simplified scanning strategies. All these methods are analysed in terms of accuracy, computational effort and suitable applications
Abstract
In this work a finite-element framework for the numerical simulation of the heat transfer analysis of additive manufacturing processes by powder-bed technologies, [...]
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Finite element modeling of quasi-brittle cracks in 2D and 3D with enhanced strain accuracy
M. Cervera, G. Barbat, M. Chiumenti

Computational Mechanics (2017). (preprint) Vol. 60 (5), pp. 767–796

Abstract
This paper discusses the finite element modeling of cracking in quasi-brittle materials. The problem is addressed via a mixed strain/displacement finite element formulation and an isotropic damage constitutive model. The proposed mixed formulation is fully general and is applied in 2D and 3D. Also, it is independent of the specific finite element discretization considered; it can be equally used with triangles/tetrahedra, quadrilaterals/hexahedra and prisms. The feasibility and accuracy of the method is assessed through extensive comparison with experimental evidence. The correlation with the experimental tests shows the capacity of the mixed formulation to reproduce the experimental crack path and the force–displacement curves with remarkable accuracy. Both 2D and 3D examples produce results consistent with the documented data. Aspects related to the discrete solution, such as convergence regarding mesh resolution and mesh bias, as well as other related to the physical model, like structural size effect and the influence of Poisson’s ratio, are also investigated. The enhanced accuracy of the computed strain field leads to accurate results in terms of crack paths, failure mechanisms and force displacement curves. Spurious mesh dependency suffered by both continuous and discontinuous irreducible formulations is avoided by the mixed FE, without the need of auxiliary tracking techniques or other computational schemes that alter the continuum mechanical problem.
Abstract
This paper discusses the finite element modeling of cracking in quasi-brittle materials. The problem is addressed via a mixed strain/displacement finite element formulation [...]
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Tracking multi-directional intersecting cracks in numerical modelling of masonry shear walls under cyclic loading
S. Salaustros, M. Cervera, L. Pelà

Meccanica (2017). (preprint) Vol. 53 (7), pp. 1757–1776

Abstract
In-plane cyclic loading of masonry walls induces a complex failure pattern composed of multiple diagonal shear cracks, as well as flexural cracks. The realistic modelling of such induced localized cracking necessitates the use of costly direct numerical simulations with detailed information on both the properties and geometry of masonry components. On the contrary, computationally efficient macro-models using standard smeared-crack approaches often result in a poor representation of fracture in the simulated material, not properly localized and biased by the finite element mesh orientation. This work proposes a possible remedy to these drawbacks of macro-models through the use of a crack-tracking algorithm. The macro-modelling approach results in an affordable computational cost, while the tracking algorithm aids the mesh-bias independent and localized representation of cracking. A novel methodology is presented that allows the simulation of intersecting and multi-directional cracks using tracking algorithms. This development extends the use of localized crack approaches using tracking algorithms to a wider field of applications exhibiting multiple, arbitrary and interacting cracking. The paper presents also a novel formulation including into an orthotropic damage model the description of irreversible deformations under shear loading. The proposed approach is calibrated through the comparison with an experimental test on a masonry shear wall against in-plane cyclic loading.
Abstract
In-plane cyclic loading of masonry walls induces a complex failure pattern composed of multiple diagonal shear cracks, as well as flexural cracks. The realistic modelling [...]
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An enhanced finite element macro-model for the realistic simulation of localized cracks in masonry structures: A large-scale application
S. Salaustros, L. Pelà, M. Cervera, P. Roca

International Journal of Architectural Heritage (2017). (preprint) Vol. 12 (3), pp. 432-447

Abstract
Finite element macro-modeling approaches are widely used for the analysis of large-scale masonry structures. Despite their efficiency, they still face two important challenges: the realistic representation of damage and a reasonable independency of the numerical results to the used discretization. In this work, the classical smeared crack approach is enhanced with a crack-tracking algorithm, originating from the analysis of localized cracking in quasi-brittle materials. The proposed algorithm is for the first time applied to a large-scale wall exhibiting multiple shear and flexural cracking. Discussion covers structural aspects, as the response of the structure under different assumptions regarding the floor rigidity, but also numerical issues, commonly overlooked in the simulation of large structures, such the mesh-dependency of the numerical results.
Abstract
Finite element macro-modeling approaches are widely used for the analysis of large-scale masonry structures. Despite their efficiency, they still face two important challenges: [...]
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Strain localization analysis of elastic-damaging frictional-cohesive materials: Analytical results and numerical verification
J. Wu, M. Cervera

Materials (2017). (preprint) Vol. 10 (4), pp. 434

Abstract
Damage-induced strain softening is of vital importance for the modeling of localized failure in frictional-cohesive materials. This paper addresses strain localization of damaging solids and the resulting consistent frictional-cohesive crack models. As a supplement to the framework recently established for stress-based continuum material models in rate form (Wu and Cervera 2015, 2016), several classical strain-based damage models, expressed usually in total and secant format, are considered. Upon strain localization of such damaging solids, Maxwell’s kinematics of a strong (or regularized) discontinuity has to be reproduced by the inelastic damage strains, which are defined by a bounded characteristic tensor and an unbounded scalar related to the damage variable. This kinematic constraint yields a set of nonlinear equations from which the discontinuity orientation and damage-type localized cohesive relations can be derived. It is found that for the “Simó and Ju 1987” isotropic damage model, the localization angles and the resulting cohesive model heavily depend on lateral deformations usually ignored in classical crack models for quasi-brittle solids. To remedy this inconsistency, a modified damage model is proposed. Its strain localization analysis naturally results in a consistent frictional-cohesive crack model of damage type, which can be regularized as a classical smeared crack model. The analytical results are numerically verified by the recently-proposed mixed stabilized finite element method, regarding a singly-perforated plate under uniaxial tension. Remarkably, for all of the damage models discussed in this work, the numerically-obtained localization angles agree almost exactly with the closed-form results. This agreement, on the one hand, consolidates the strain localization analysis based on Maxwell’s kinematics and, on the other hand, illustrates versatility of the mixed stabilized finite element method.
Abstract
Damage-induced strain softening is of vital importance for the modeling of localized failure in frictional-cohesive materials. This paper addresses strain localization of [...]
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An energy-equivalent d+/d− damage model with enhanced microcrack closure-reopening capabilities for cohesive-frictional materials
M. Cervera, C. Tesei

Materials (2017). (preprint) Vol. 10 (4), pp. 433

Abstract
In this paper, an energy-equivalent orthotropic d+/d− damage model for cohesive-frictional materials is formulated. Two essential mechanical features are addressed, the damage-induced anisotropy and the microcrack closure-reopening (MCR) effects, in order to provide an enhancement of the original d+/d−model proposed by Faria et al. 1998, while keeping its high algorithmic efficiency unaltered. First, in order to ensure the symmetry and positive definiteness of the secant operator, the new formulation is developed in an energy-equivalence framework. This proves thermodynamic consistency and allows one to describe a fundamental feature of the orthotropic damage models, i.e., the reduction of the Poisson’s ratio throughout the damage process. Secondly, a “multidirectional” damage procedure is presented to extend the MCR capabilities of the original model. The fundamental aspects of this approach, devised for generic cyclic conditions, lie in maintaining only two scalar damage variables in the constitutive law, while preserving memory of the degradation directionality. The enhanced unilateral capabilities are explored with reference to the problem of a panel subjected to in-plane cyclic shear, with or without vertical pre-compression; depending on the ratio between shear and pre-compression, an absent, a partial or a complete stiffness recovery is simulated with the new multidirectional procedure.
Abstract
In this paper, an energy-equivalent orthotropic d+/d− damage model for cohesive-frictional materials is formulated. Two essential mechanical features are addressed, [...]
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3D numerical modelling of twisting cracks under bending and torsion of skew notched beams
L. Benedetti, M. Cervera, M. Chiumenti

Engineering Fracture Mechanics (2017). (preprint) Vol. 176, pp. 235–256

Abstract
The testing of mode III and mixed mode failure is every so often encountered in the dedicated literature of mechanical characterization of brittle and quasi-brittle materials. In this work, the application of the mixed strain displacement ε-u finite element formulation to three examples involving skew notched beams is presented. The use of this FE technology is effective in problems involving localization of strains in softening materials. The objectives of the paper are: (i) to test the mixed formulation in mode III and mixed mode failure and (ii) to present an enhancement in terms of computational time given by the kinematic compatibility between irreducible displacement-based and the mixed strain-displacement elements. Three tests of skew-notched beams are presented: firstly, a three point bending test of a PolyMethyl MethaAcrylate beam; secondly, a torsion test of a plain concrete prismatic beam with square base; finally, a torsion test of a cylindrical beam made of plain concrete as well. To describe the mechanical behavior of the material in the inelastic range, Rankine and Drucker-Prager failure criteria are used in both plasticity and isotropic continuum damage formats. The proposed mixed formulation is capable of yielding results close to the experimental ones in terms of fracture surface, peak load and global loss of carrying capability. In addition, the symmetric secant formulation and the compatibility condition between the standard irreducible method and the strain-displacement one is exploited, resulting in a significant speedup of the computational procedure.
Abstract
The testing of mode III and mixed mode failure is every so often encountered in the dedicated literature of mechanical characterization of brittle and quasi-brittle [...]
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A fast and accurate two-stage strategy to evaluate the effect of the pin tool profile on metal flow, torque and forces during friction stir welding
N. Dialami, M. Cervera, M. Chiumenti, C. Agelet de Saracibar

Int. J. Mechanical Sciences (2017). (preprint) Vol. 122, pp. 215–227

Abstract
Pin geometry is a fundamental consideration in friction stir welding (FSW). It influences the thermal behaviour, material flow and forces during the weld and reflects on the joint quality. This work studies four pin tools with circular, triflute, trivex, and triangular profiles adopting a validated model of FSW process developed by the authors. The effect of the rotating tool geometry on the flow behaviour and process outcomes is analysed. Additionally, longitudinal and transversal forces and torque are numerically calculated and compared for the different pin shapes. The study is carried out for slip and stick limiting friction cases between pin and workpiece. The main novelties of the paper are a “speed-up” two-stage simulation methodology and a piecewise linear version of the constitutive model, both of them conceived for the use in real case industrial applications, where the achievement of accuracy with affordable simulation times is of importance. The Norton-Hoff constitutive model is adopted to characterize the material behaviour during the weld. The piecewise linear version of the model developed by the authors greatly facilitates the convergence of the numerical solution ensuring both computational efficiency and accuracy. A two-stage computational procedure is applied. In the first stage, a forced transient is carried out; in the second one, the magnitudes of interest are computed. The study shows that the proposed modelling approach can be used to predict and interpret the FSW behaviour for a specific pin geometry. Moreover, the reduction of the simulation time using the two-stage strategy can be up to 90%, compared to a standard single stage strategy.
Abstract
Pin geometry is a fundamental consideration in friction stir welding (FSW). It influences the thermal behaviour, material flow and forces during the weld and [...]
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Finite element modelling of internal and multiple localized cracks
S. Salaustros, L. Pelà, M. Cervera, P. Roca

Computational Mechanics (2017). (preprint) Vol. 59 (2), pp. 299–316

Abstract
Tracking algorithms constitute an efficient numerical technique for modelling fracture in quasi-brittle materials. They succeed in representing localized cracks in the numerical model without mesh-induced directional bias. Currently available tracking algorithms have an important limitation: cracking originates either from the boundary of the discretized domain or from predefined “crack-root” elements and then propagates along one orientation. This paper aims to circumvent this drawback by proposing a novel tracking algorithm that can simulate cracking starting at any point of the mesh and propagating along one or two orientations. This enhancement allows the simulation of structural case-studies experiencing multiple cracking. The proposed approach is validated through the simulation of a benchmark example and an experimentally tested structural frame under in-plane loading. Mesh-bias independency of the numerical solution, computational cost and predicted collapse mechanisms with and without the tracking algorithm are discussed.
Abstract
Tracking algorithms constitute an efficient numerical technique for modelling fracture in quasi-brittle materials. They succeed in representing localized cracks in the numerical [...]
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Numerical simulation and experimental calibration of Additive Manufacturing by blown powder technology. Part I: thermal analysis
M. Chiumenti, X. Lin, M. Cervera, W. Lei, Y. Zheng, W. Huang

Rapid Prototyping Journal (2017). (preprint) Vol. 23 (2), pp. 448-463

Abstract
In this work the numerical simulation of Additive Manufacturing (AM) processes is addressed. The numerical results are compared with the experimental campaign carried out at SKLSP laboratories, where a Laser Solid Forming (LSF) machine, also referred to as Laser Engineered Net Shaping (LENS), is used to fabricate metal parts directly from CAD models. Ti-6Al-4V metal powder is injected into the molten pool created by a focused, high-energy laser beam and a layer of added material is sinterized according to the laser scanning pattern speciÖed by the user. The objectives of this paper are twofold: Örstly, this work is intended to calibrate the software for the numerical simulation of the AM process, to achieve high accuracy. Secondly, the sensitivity of the numerical model to the process parameters and modelling data is analysed. The numerical model adopts an apropos FE activation technology, which reproduces the same scanning pattern set for the numerical control system of the AM machine. This consists of a complex sequence of polylines, used to deÖne the contour of the component, and hatches patterns to Öll the inner section. The full sequence is given through the Common Layer Interface (CLI) format, a standard format for di§erent manufacturing processes such as Rapid Prototyping (RP), Shape Metal Deposition (SMD) or machining processes, among others. The result is a layer-by-layer metal deposition which can be used to build-up complex structures for components such as turbine blades, aircraft sti§eners, cooling systems, or medical implants, among others.
Abstract
In this work the numerical simulation of Additive Manufacturing (AM) processes is addressed. The numerical results are compared with the experimental campaign carried out [...]
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Local–global strategy for the prediction of residual stresses in FSW processes
N. Dialami, M. Cervera, M. Chiumenti, C. Agelet de Saracibar

International Journal of Advanced Manufacturing Technology (2017). (preprint) Vol. 88 (9), pp. 3099–3111

Abstract
This work describes the local–global strategy proposed for the computation of residual stresses in friction stir welding (FSW) processes. A coupling strategy between the analysis of the process zone nearby the pin tool (local level analysis) and the simulation carried out for the entire structure to be welded (global level analysis) is implemented to accurately predict the temperature histories and, thereby, the residual stresses in FSW. As a first step, the local problem solves the material stirring as well as the heat generation induced by the pin and shoulder rotation at the heat affected zone. The Arbitrary Lagrangian Eulerian (ALE) formulation is adopted to deal with the rotation of complex pin shapes. A thermo-rigid-viscoplastic constitutive law is employed to characterize the viscous flow of the material, driven by the high-strain rates induced by the FSW process. A mixed temperature–velocity–pressure finite element technology is used to deal with the isochoric nature of the strains. The output of this local analysis is the heat generated either by plastic dissipation or by friction, and it is used as the power input for the welding analysis at structural (global) level. The global problem is tackled within the Lagrangian framework together with a thermo-elasto-viscoplastic constitutive model. In addition, in this case, the mixed temperature–displacement–pressure format is introduced to deal with the deviatoric nature of the plastic strains. The outcomes of this analysis are the distortions and the residual stresses after welding. The material used in this work is stainless steel 304 L; however, the methodology presented is applicable to a wide range of materials. The proposed numerical strategy is validated by the experimental evidence.
Abstract
This work describes the local–global strategy proposed for the computation of residual stresses in friction stir welding (FSW) processes. A coupling strategy between [...]
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Challenges in thermo-mechanical analysis of Friction Stir Welding processes
N. Dialami, M. Chiumenti, M. Cervera, C. Agelet de Saracibar

Archives of Comp. Meths. Engng. (2017). (preprint) Vol. 24 (1), pp. 198-225

Abstract
This paper deals with the numerical simulation of friction stir welding (FSW) processes. FSW techniques are used in many industrial applications and particularly in the aeronautic and aerospace industries, where the quality of the joining is of essential importance. The analysis is focused either at global level, considering the full component to be jointed, or locally, studying more in detail the heat affected zone (HAZ). The analysis at global (structural component) level is performed defining the problem in the Lagrangian setting while, at local level, an apropos kinematic framework which makes use of an efficient combination of Lagrangian (pin), Eulerian (metal sheet) and ALE (stirring zone) descriptions for the different computational sub-domains is introduced for the numerical modeling. As a result, the analysis can deal with complex (non-cylindrical) pin-shapes and the extremely large deformation of the material at the HAZ without requiring any remeshing or remapping tools. A fully coupled thermo-mechanical framework is proposed for the computational modeling of the FSW processes proposed both at local and global level. A staggered algorithm based on an isothermal fractional step method is introduced. To account for the isochoric behavior of the material when the temperature range is close to the melting point or due to the predominant deviatoric deformations induced by the visco-plastic response, a mixed finite element technology is introduced. The Variational Multi Scale method is used to circumvent the LBB stability condition allowing the use of linear/linear P1/P1 interpolations for displacement (or velocity, ALE/Eulerian formulation) and pressure fields, respectively. The same stabilization strategy is adopted to tackle the instabilities of the temperature field, inherent characteristic of convective dominated problems (thermal analysis in ALE/Eulerian kinematic framework). At global level, the material behavior is characterized by a thermo–elasto–viscoplastic constitutive model. The analysis at local level is characterized by a rigid thermo–visco-plastic constitutive model. Different thermally coupled (non-Newtonian) fluid-like models as Norton–Hoff, Carreau or Sheppard–Wright, among others are tested. To better understand the material flow pattern in the stirring zone, a (Lagrangian based) particle tracing is carried out while post-processing FSW results. A coupling strategy between the analysis of the process zone nearby the pin-tool (local level analysis) and the simulation carried out for the entire structure to be welded (global level analysis) is implemented to accurately predict the temperature histories and, thereby, the residual stresses in FSW.
Abstract
This paper deals with the numerical simulation of friction stir welding (FSW) processes. FSW techniques are used in many industrial applications and particularly in the aeronautic [...]
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Agenda
-. EPI

El profesional de la información (2017). Vol. 26, (3), 138
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Library systems report 2017. Competing visions for technology, openness, and workflow
M. Breeding

El profesional de la información (2017). Vol. 26, (3), 137

Abstract
The
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Artistic heritage during the Spanish Civil War and the postwar period: Research, cataloging, and digital management of saved art
A. Colorado-Castellary, I. Moreno-Sánchez

El profesional de la información (2017). Vol. 26, (3), 136

Abstract
This research analyzes and catalogs the thousands of works rescued and deposited in safe places by the Spanish Republic during the Spanish Civil War and checks the destination of these works during the postwar period under the Franco regime. A web site with a narrative and participative database, open and accessible, that would allow analysis, collaboration from other investigators and interested people was created. The objective of this site is to establish the confluence between historic and heritage-oriented inquiry and collaborative and open management to transmit to society the results of a pending investigation. The possibilities offered by the 2.0 semantic web and of artificial intelligence are taken advantage of in order to follow the destinations of the works. Free software is always used, with added algorithms and applications necessary for their optimization. These inputs will also become part of the public domain.
Abstract
This research analyzes and catalogs the thousands of works rescued and deposited in safe places by the Spanish Republic during the Spanish Civil War and checks the destination [...]
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Records in contexts: A new model for the representation of archival information in semantic web scenarios
D. Llanes-Padrón, M. Moro-Cabero

El profesional de la información (2017). Vol. 26, (3), 135

Abstract
This article studies the main concepts, properties, attributes, and connections included in Records in contexts (RiC), a draft of a new conceptual model for record description by the International Council of Archives (ICA). The analysis shows the new design of representation, access, use, preservation, and interoperability for information-records that this model represents in the environment of the semantic web. The intrinsic advantages of RiC for the integration and compatibility of records information systems with libraries, museums, and other cultural institutions are shown, also highlighting its relevance for distribution, reutilization, and free-use of records’ resources in digital scenarios.
Abstract
This article studies the main concepts, properties, attributes, and connections included in Records in contexts (RiC), a draft of a new conceptual model for record description [...]
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The library and informational competences in the curriculum of students of Sciences, Medicine, and Health Sciences of the University of Alcalá, Spain
M. Domínguez-Aroca

El profesional de la información (2017). Vol. 26, (3), 134

Abstract
This paper aims to explain how the libraries in Sciences, Medicine, and Health Sciences at the University of Alcalá (UAH), Spain, have implemented information literacy (IL) in courses from 2010-2011 to 2015-2016, usually as part of the curriculum, including them in most teaching guides. This article discusses the strategy followed, the information available to achieve teacher collaboration, the opportunities offered by the European Higher Education Area (EHEA), the background data, the way IL has been gradually incorporated in various studies, and finally, the obvious advantages in the learning process.
Abstract
This paper aims to explain how the libraries in Sciences, Medicine, and Health Sciences at the University of Alcalá (UAH), Spain, have implemented information literacy (IL) [...]
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Integrated communication 2.0 in municipal administration
C. Campillo-Alhama, A. Martínez-Sala

El profesional de la información (2017). Vol. 26, (3), 133

Abstract
Municipal communication transcends the simple information about public services, activities, projects, and administrative procedures. Communicative and information strategies in the local context are oriented towards citizens who participate in a shared municipal project in which they are prosumers in the design and development of sectorial strategies linked to public policies. Consequently, city councils must integrate a communication structure that takes advantage of public information from governance, transparency, and proactive citizen participation. Since the first Spanish democratic legislature in 1979 the evolution and adaptation of process and production routines has been justified by the need to shape a positive perception of government action and consolidate their institutional reputation. In this paper an approach to municipal communication, based on the rigid and standardized models of the 80s and 90s, is presented to influence the current revolution that represents the paradigm of communication 2.0, the implementation of the social web in the context of proximity and social media strategy.
Abstract
Municipal communication transcends the simple information about public services, activities, projects, and administrative procedures. Communicative and information strategies [...]
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Integrated communication 2.0 in municipal administration
C. Campillo-Alhama, A. Martínez-Sala

El profesional de la información (2017). Vol. 26, (3), 132

Abstract
La comunicación municipal trasciende la simple información sobre servicios públicos, actividades, proyectos o trámites administrativos. Las estrategias comunicativas y de información en el contexto local se orientan hacia los ciudadanos para poner en valor un proyecto municipal compartido en el que éstos se implican como prosumidores en el diseño y desarrollo de estrategias sectoriales vinculadas a las políticas públicas. En consecuencia, los ayuntamientos deben integrar en su estructura una dirección de comunicación que asuma la función de información pública desde la gobernanza, la transparencia y la participación ciudadana proactiva. Desde la primera legislatura democrática en 1979 la evolución y adaptación de sus procesos y rutinas productivas se justifica por la necesidad de configurar una percepción positiva de la acción del gobierno y consolidar su reputación institucional. En este trabajo se realiza una aproximación a la dirección de comunicación municipal basada en los modelos rígidos y estandarizados de los años 80 y 90, para incidir en la revolución actual que representa el paradigma de la comunicación 2.0, la implementación de la web social en el contexto de proximidad y la estrategia de medios sociales.Abstract Municipal communication transcends the simple information about public services, activities, projects, and administrative procedures. Communicative and information strategies in the local context are oriented towards citizens who participate in a shared municipal project in which they are prosumers in the design and development of sectorial strategies linked to public policies. Consequently, city councils must integrate a communication structure that takes advantage of public information from governance, transparency, and proactive citizen participation. Since the first Spanish democratic legislature in 1979 the evolution and adaptation of process and production routines has been justified by the need to shape a positive perception of government action and consolidate their institutional reputation. In this paper an approach to municipal communication, based on the rigid and standardized models of the 80s and 90s, is presented to influence the current revolution that represents the paradigm of communication 2.0, the implementation of the social web in the context of proximity and social media strategy.
Abstract
La comunicación municipal trasciende la simple información sobre servicios públicos, actividades, proyectos o trámites administrativos. Las estrategias comunicativas y [...]
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Women journalists in Spain: An analysis of the sociodemographic features of the gender gap”
R. De-Miguel, T. Hanitzsch, S. Parratt, R. Berganza

El profesional de la información (2017). Vol. 26, (3), 131

Abstract
Sociodemographic features and their relative weight related to the gender gap between male and female journalists in Spain are analyzed. A national representative survey of 390 journalists was carried out as part of an international study “Worlds of journalism”. The results show that patterns of female inequality within Spanish media companies are routinely cited in scientific literature (underrepresentation, barriers in their professional careers, and lower salaries than men). The results also confirm the 3R hypothesis (ratio of Recurrent and Reinforced Residuum): men hold three quarters of the posts with managerial responsibility and make two thirds of the decisions related to content, in spite of the fact that female journalists have higher levels of academic education and are therefore better trained for journalistic practice. Women are also paid lower salaries and tend to hold positions with a higher editorial responsibility in digital media, where the greatest progress towards equality is shown.
Abstract
Sociodemographic features and their relative weight related to the gender gap between male and female journalists in Spain are analyzed. A national representative survey of [...]
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Women journalists in Spain: An analysis of the sociodemographic features of the gender gap
R. De-Miguel, T. Hanitzsch, S. Parratt, R. Berganza

El profesional de la información (2017). Vol. 26, (3), 130

Abstract
Se analizan las características sociodemográficas y su peso relativo en la brecha de género entre los/as periodistas españoles/ as. Para ello se realizó una encuesta nacional representativa a 390 periodistas dentro del estudio internacional “Worlds of journalism study”. Los resultados muestran que los patrones de desigualdad femenina más citados en la bibliografía científica (infrarrepresentación, barreras en la carrera profesional y salarios inferiores) prevalecen en las empresas de comunicación españolas. También confirman la hipótesis de las 3R (la ratio del Residuo Reforzado Recurrente): los hombres ocupan tres cuartas partes de los cargos de máxima responsabilidad gerencial y dos tercios de los puestos de toma de decisiones sobre contenidos, a pesar de que ellas poseen mayor formación académica y mayor nivel de estudios de capacitación en la práctica del periodismo. Ellas obtienen, además, salarios inferiores y tienden a ocupar cargos de mayor responsabilidad editorial en los medios digitales, donde se observan mayores avances hacia la igualdad.Abstract Sociodemographic features and their relative weight related to the gender gap between male and female journalists in Spain are analyzed. A national representative survey of 390 journalists was carried out as part of an international study “Worlds of journalism”. The results show that patterns of female inequality within Spanish media companies are routinely cited in scientific literature (underrepresentation, barriers in their professional careers, and lower salaries than men). The results also confirm the 3R hypothesis (ratio of Recurrent and Reinforced Residuum): men hold three quarters of the posts with managerial responsibility and make two thirds of the decisions related to content, in spite of the fact that female journalists have higher levels of academic education and are therefore better trained for journalistic practice. Women are also paid lower salaries and tend to hold positions with a higher editorial responsibility in digital media, where the greatest progress towards equality is shown.
Abstract
Se analizan las características sociodemográficas y su peso relativo en la brecha de género entre los/as periodistas españoles/ as. Para ello se realizó una encuesta [...]
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Probability of paying for digital news in Spain
M. Goyanes, A. Vara-Miguel

El profesional de la información (2017). Vol. 26, (3), 129

Abstract
The probability of paying for a digital newspaper in Spain is analyzed. Using a survey of a representative sample of 2,104 Spanish adults, we show, in general terms, the lack of people willing to pay for digital information. In addition, through a logistic regression analysis, we explore which factors affect this probability and discuss the main practical implications of developing paid-content strategies in the newspaper industry.
Abstract
The probability of paying for a digital newspaper in Spain is analyzed. Using a survey of a representative sample of 2,104 Spanish adults, we show, in general terms, the lack [...]
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