Scipedia: Documents published in 2021

Long-Term Orbit Dynamics of Decommissioned Geostationary Satellites

Roberto Flores — Sat, 02 Jan 2021 19:58:02 +0100

In nominal mission scenarios, geostationary satellites perform end-of-life orbit maneuvers to reach suitable disposal orbits, where they do not interfere with operational satellites. This research investigates the long-term orbit evolution of decommissioned geostationary satellite under the assumption that the disposal maneuver does not occur and the orbit evolves with no control. The dynamical model accounts for all the relevant harmonics of the terrestrial gravity field at the typical altitude of geostationary orbits, as well as solar radiation pressure and third-body perturbations caused by the Moon and the Sun. Orbit propagations are performed using two algorithms based on different equations of motion and numerical integration methods: (i) Gauss planetary equations for modified equinoctial elements with a Runge-Kutta numerical integration scheme based on 8-7^th-order Dorman and Prince formulas; (ii) Cartesian state equations of motion in an Earth-fixed frame with a Runge-Kutta Fehlberg 7/8 integration scheme. The numerical results exhibit excellent agreement over integration times of decades. Some well-known phenomena emerge, such as the longitudinal drift due to the resonance between the orbital motion and Earth’s rotation, attributable to the J2 term of the geopotential. In addition, the third-body perturbation due to Sun and Moon causes two major effects: (a) a precession of the orbital plane, and (b) complex longitudinal dynamics. This study proposes an analytical approach for the prediction of the precessional motion and show its agreement with the (more accurate) orbit evolution obtained numerically. Moreover, long-term orbit propagations show that the above mentioned complex longitudinal dynamics persists over time scales of several decades. Frequent and unpredictable migrations toward different longitude regions occur, in contrast with the known effects due only to the perturbative action of J2

Safety assessment of corrosion-defective natural gas pipeline under ground overload based on FEM

Ting Zheng — Tue, 22 Dec 2020 03:21:09 +0100

Aiming at the safety problem of the pipeline containing corrosion defects caused by ground overload, a novel method is developed to assess the safety of buried pipelines with corrosion defects and predict the failure pressure. The effects of parameters including internal pressure, ground overload, length of the loading area, corrosion defect depth, buried depth and soil Young’s modulus, are discussed. Ground overload greatly increases the von Mises stress and strain at the corrosion defect location and decreases the internal pressure threshold. The von Mises stress and strain are an obvious nonlinear relationship with internal pressure. The high stress and strain area expand along the diagonal direction of the defect area. The local stress and strain concentration at the corrosion defect increases with the increase of ground overload, length of the loading area and corrosion defect depth, which reduces the failure pressure of the pipeline. Increasing the buried depth and soil Young’s modulus would effectively reduce local stress and strain concentration, and increase the failure pressure of the pipeline. The pipeline settlement displacement increases with the increase of internal pressure, ground overload, length of the loading area, and decreases with the increase of pipeline buried depth and soil Young’s modulus.

Thermal behavior characterization for MOSFETs and BJTs in hazardous locations

Dorindo Cardenas — Mon, 21 Dec 2020 08:54:07 +0100

This paper shows a numerical polynomial approximation to the issue of how junction transistors "BJT" and field effect transistors "FET" can work in safe or unsafe conditions in explosive atmospheres. We have analyzed the most widely used transistors with thermal imaging, working in a controlled environment, to characterize their thermal behavior. With this characterization, we can predict their possibility to ignite a classified location (explosive atmosphere) fundamentally by mean of thermal-conduction and reaching the minimum activation energy of the combustible vapor, dust or flying. We have bring these transistors to their nominal rated values specified by their currents and working voltages, and we found that the effect of heat dissipation on the base-emitter junction of a transistor BJT is really non linear and much greater than on the threshold voltage of polarization of the FET due to the inherent loses to obtain the nominal voltage of the diode that forms the base-emitter junction. We have found experimentally that it is very easy to obtain a thermal difference of more than 200 °C in overheating of a common BJT compared to a MOSFET with a similar load in fixed polarization. We found temperatures over 300ºC in BJTs in common operating ranges, when the accepted “safe” temperature is supposed to be no more than 200ºC in any case. This issue is addressed with performance-based analysis, focused on temperature, and it suggest that equipment with BJT technologies should not be implemented in some areas of hazardous or explosive locations; so MOSFET technologies are preferable.

The impact and sensitivity analysis of beam and stringer for stiffness center of composite wing structure

shengjun qiao — Mon, 21 Dec 2020 06:06:52 +0100

'''Wing stiffness center should be determined firstly for structure detail design. The present study focused on the impact analysis of beam and stringer for wing cross-section stiffness center based on thin wall structure mechanics theory. In order to discuss the impact of beam and stringer on stiffness center, the sensitivity formulas for stiffness center of wing cross-section were derived and expressed in terms of the dimension and layout of beams and stringers. The results indicated that the structural layouts of beam and stringer were important influencing factors in stiffness detail design of full composite wing structure. The research results can provide an important reference for the stiffness design and aeroelastic design of the full composite wing. '''Key words: '''Composite wing, Stiffness center, Layout, Dimension, Sensitivity

No-wait open shop with worker flexibility

Matheus Bazo do Nascimento — Thu, 03 Dec 2020 20:45:03 +0100

The Open Shop Problem is a Production Scheduling problem where jobs do not have predestined processing routes, which increases the solution space and, therefore, the complexity of the problem. This work proposes a novel mathematical model that addresses the Open Shop theme with worker flexibility and no-wait. We consider the resource constraint of flexible and multiskilled labor. That is, the workers can execute their activities in more than one workstation. Simultaneously, the latter the continued production is contemplated, which hinders the reachability of feasible solutions and therefore increases the problem complexity. To validate the model, we generate several benchmarks, and the results obtained highlight the importance of worker flexibility in achieving greater problem feasibility.

Seismic analysis of uplift-available gantry crane subjected to extreme earthquake loads

Qihui Peng — Thu, 03 Dec 2020 07:59:03 +0100

This paper aims to investigate the uplift behavior coupled with the non-linearity both in material properties and in geometry deformations of a typical gantry crane under near-field ground motions. First, the highly nonlinear and time variable model considering the uplift-available boundary condition based on the theory of Mohr-Coulomb friction is established of the gantry crane using the OpenSees platform. Then, a series of time-history analyses on this model structure is performed under three near-field seismic loadings with different exceeding probabilities. Furthermore, the comparison between the uplift-available gantry crane and the fixed crane is also carried out to provide in-depth insight into the structural responses under different boundary conditions. Finally, coupling with the material and geometry inelastic behavior, the uplift response process is modeled in this paper and the seismic incident angle from 0 up to 360 degrees is also examined to quantitatively confirm the prioritization of uplift event and the other inelastic responses. And the new conception of uplift probability is first proposed herein to reveal the nature of uncertainty. It is found that uplift behavior plays an essential role in designing and evaluating the seismic performance of gantry cranes; further, the uplift response increases the seismic demand of the gantry crane structure and even causes collapse under strong ground motions.

The dynamic characteristics of backfill made of mining waste at one-dimensional dynamic and static loading

Yunpeng Zhang — Wed, 02 Dec 2020 15:43:42 +0100

Backfill is widely used in underground mines around the world for its effective reduction in environmental impact of mining operations by utilizing a part of mine waste as underground backfill material. The strength of backfill plays a critical role in improving stop stability and preventing surface subsidence. In this paper, a series of SHPB (Split Hopkinson Pressure Bar) tests with different strain rates and static axial pressures are conducted. The results show that: (1) The dynamic strength of the backfill specimen increases first and then decreases with the increase of static axial pressure. It reaches a maximum when the static axial pressure reaches 30% of the static compressive strength in the SHPB test. (2) The stress-strain curves of backfill specimens can be divided into three stages: elastic stage, yield stage and failure stage. The compaction stage is obscure. The backfill specimens are not sensitive at low strain rate. (3)With the increase of incident energy, the absorbed energy mounts. (4) The failure mode of the backfill specimen is tensile failure when static axial pressure is 0MPa in the SHPB test while it becomes compression shear failure when static axial pressure is higher than 0MPa. (5) The backfill specimen is very compressed when it is loaded with axial stress and confining stress simultaneously. This compression property of backfill specimen may be related to the nature of hydration products at different curing times, which requires further research in the future.

Numerical investigation of setup effects in the vertical holding capacity of finless torpedo anchors

Guilherme Kronemberger Lopes — Thu, 26 Nov 2020 20:23:04 +0100

This article presents a numerical based study on the vertical holding capacity of a typical finless torpedo anchor embedded in a pure cohesive isotropic sol considering setup effects. A strategy based on two axisymmetric nonlinear FE models is proposed. In these models, the soil is represented with continuous solid elements with both plane translational and pore pressure degrees of freedom, which allow the modeling of the strength regain of the soil after the installation of the anchor, ''i. e.'', the soil setup. The anchor is also modeled with solid elements. Moreover, the anchor-soil interaction is addressed with contact elements. Several analyses are conducted to evaluate setup effects and, additionally, a parametric study on different soil undrained shear strengths and coefficients of permeability is performed. The results obtained show that the permeability of the soil and its undrained shear strength play an important role in the setup process. An inverse proportional relationship is observed between consolidation time and the permeability coefficient of the soil. Furthermore, an analytical approach is calibrated with a reasonable agreement to the numerical results.

Effects of surging and heaving movements of platform on mechanical behaviors of SCT installation pipe

Chen Neng — Wed, 28 Oct 2020 07:41:04 +0100

The effects of surging and heaving movements of installation platform on mechanical behaviors of SCT installation pipe was studied. Movements of SCT installation platform, ocean wave and current, water depth, SCT weight, installation pipe specification and those dominate the mechanical behaviors of installation pipe and SCT installation precision were considered. The results indicate that surging movement of the platform is the main factor that dominate the deformation of the installation pipe. The surging and heaving movements have significant effect on the tension force loaded on the installation pipe and thus need to be considered when designing SCT installation.

Conductas Suicidas En Los Adolescentes, Y Su Relación Con Las Negligencias En El Autocuidado Y Los Comportamientos Temerarios

Bustos Quiñones Otoniel Mauricio — Mon, 26 Oct 2020 21:37:03 +0100

The adolescents by multiple characteristics of they age are the most prone population to suicide, this is a phenomenon that represents an estimated 800,000 deaths a year in the world. The objective of this review is analyze a representative number of recent research results on suicidal behaviors in adolescents and their relationship with negligence in self-care and reckless behavior. For this, a systematic review of the literature published in the last five years was carried out in databases such as: National Center for Biotechnology Information, Virtual Health Library, Pubmed Central, Mediclatina - Ebsco and Google Scholar. Among others, the main findings are that risky sexual practices, the consumption of alcoholics beverages, psychoactive substances and sedentary lifestyle are behaviors linked to impulsivity that generate an impact on physical and emotional health, which favor the development of self-destructive behaviors in teenagers. In conclusion, the review allowed showing a close relationship of reckless behaviors and negligence in self-care and suicidal behavior in adolescence, which facilitated grouping them into these categories.

A study of droplet evaporation coupling model based on Eulerian method

Yan TAN — Sun, 25 Oct 2020 11:30:47 +0100

Research on engine icing is a hot topic among the world. Different from the aircraft wing or airframe icing, the evaporation phenomenon in the internal flow field has a great influence on the engine icing. Moreover, the thermodynamic coupling between droplets and flow field is not available in current particle trajectory calculations, or only for one-dimensional situation. Therefore, a three-dimensional droplet trajectory calculation model based on Eulerian method is used to demonstrate the thermodynamic coupling between droplets and flow field. The model was verified by NRC small engine icing wind tunnel test data and the flow field evolution is obtained which cannot be obtained by the one-dimensional coupling model. In the meanwhile, the effects of different initial LWC, relative humidity and MVD on the internal flow evaporation were studied, and the trends of droplets and flow field affected by evaporation were obtained. The numerical method in this paper can provide guidance for the subsequent research on engine icing.

Monitoring and support optimization analysis of surrounding rock pressure and initial supporting stress in deep-buried soft rock tunnel

RUIFENG LI — Sat, 24 Oct 2020 09:48:38 +0200

Attempting at the problems of surrounding rock pressure and initial supporting stress of deep-buried soft rock tunnel, a soft rock highway tunnel project in Northwest China was monitored on-site for surrounding rock deformation, surrounding rock pressure, initial stress and other items.Discuss the deformation laws and stress characteristics of surrounding rock and steel arch at different construction stages, and compare and analyze the deformation control effect of surrounding rock with different initial lining thickness, different initial elastic modulus and different anchor length through numerical simulation.The results show that the excavation stage of the upper step is a stage where the pressure and deformation of the surrounding rock increase rapidly. The steel arch support is mainly compressed, and the average stress can reach more than 50% of the peak value within 5 days. The stress is mostly higher than the measuring point of the lower step. The initial steel frame support of the upper step and the middle step bears a greater load. The excavation of the upper middle step should be "passed quickly and supported in time", and the construction should adopt The “letting first,then resisting” method appropriately increases the reserved deformation of the surrounding rock to relieve the support stress of the primary steel frame. When the deformation of the surrounding rock and the growth rate of the surrounding rock pressure slow down, the secondary lining can be applied in advance. The research results can provide reference and reference for the design and construction of similar tunnel projects.

The erosion wear mechanism of liquid-solid two-phase high pressure manifold tee pipes

H Z — Fri, 16 Oct 2020 09:30:14 +0200

The wall thickness of pressure pipe is often thinned due to the erosion wear, which leads to pipe failure and even safety accidents. In particular, the tee pipe is more prone to be erosive as a key component of transferring fluid with particles. Therefore, the erosion wear mechanism of high pressure manifold tee pipe based on liquid-solid two-phase flow is studied in this paper. Firstly, the standard tee pipe geometry model is established and the grid is divided. And then grid number independence is verified by the percentage difference. According to the structural characteristics of tee pipe, the wear of the inner wall under four different port combinations is predicted. In addition, the relationship between erosion rate and wall shear stress is further analyzed by fluid velocity, particle diameter and mass flow rate. Double tee pipes geometry model was established to explore the erosion wear on the inner walls. The effects of assembly length and different port combinations on erosion wear were discussed respectively. When the inlets are fixed, the wall shear stress distribution of the downstream tee pipe is mainly affected by the outlets. The assembly length mainly affects the erosion rate of the downstream tee pipe.

Seismic assessment of tall RC frames with hybrid friction damper and SMA designed by PBPD method

Heydar Dashti Naserabadi — Mon, 28 Sep 2020 10:25:03 +0200

This study, proposes a new lateral load resisting system for high-rise (Reinforced Concrete) RC frames, which includes friction damper-superelastic SMA wires. The proposed SMA-friction damper can not only regulate the mechanism of frictional energy dissipation components with its self-centering SMA wires according to the design method based on the proposed performance, which is able to provide a hysteretic behavior and high self-centering capacity with the lowest SMA consumption but also has some advantages such as simple configuration and economic application. In this paper, two high-rise 18 and 22-story RC frames were designed in two design modes of common and with the proposed damper. The nonlinear time history analysis subjected to 10 far-field earthquakes performed in Opensees software. The results of the analyses showed that using the proposed SMA-friction damper, in addition to the effective increase in ductility, lateral stiffness and lateral strength, provided an excellent self-centering capacity, which resulted to the significant reduction in the maximum drift and the residual deformations in the structure.

Investigating the nonlinear dynamic seismic response of double curvature arch dams under spatial and temporal excitation of heterogeneous ground motion

Heydar Dashti Naserabadi — Mon, 28 Sep 2020 10:21:04 +0200

One of the factors affecting the dynamic state of the dams that may cause damages to the dam is the change under the spatial and temporal Excitation of the Heterogeneous ground Motion. Therefore, in different states the stress, strain, displacement and hydrostatic pressure indices are changed and led to serious damage to the dam. In this study, Karun 3 dam is investigated which is classified as one of the double curvature arch and gravity dams. For this purpose, using ABAQUS software, these indices have been investigated and controlled and the effectiveness of indices in this dam has been investigated in nonlinear dynamic seismic state. Northridge, Kobe, Bam, Hector, Chi-Chi and Manjil earthquakes are applied to the Karun 3 Dam. The results showed that due to the large amplitude and periodicity of the near-fault mappings, under the near-field earthquake, the deformation of the Karun 3 dam is greater than the far-field fault zone. As the height of the Karun 3 Dam rises, the effectiveness of far-field earthquakes declines and near-field earthquakes show more impact on the structure. In far-field earthquakes, stress changes due to earthquakes with maximum dynamic acceleration, the relative percentage of mises stress change is 15.5% and maximum dam crest change is 68.5 mm, and for near-field earthquakes is 25% and maximum dam crest change is 100 mm.

The Idealized Smeared Reinforcement (ISR) method for the optimization of concrete sections: a survey of the state-of-the-art and analysis of potential computational approaches

Luis Fernando Verduzco Martínez — Mon, 28 Sep 2020 00:24:04 +0200

The present work aims to define formally the method termed as \textit{``Idealized Smeared Reinforcement'' (ISR)} for optimization in the design of reinforcing steel in concrete structures, its boundaries, background and potentials. Such method has been extensively used implicitly in many different studies of reinforced concrete structures related with optimization and mechanical structural behaviour, but it has not yet been formally established as a method itself even though it represents a great solution approach when designing optimally concrete sections, which is a tendency so vital nowadays for sustainability in construction projects. A general survey of such method of the ISR will be presented on in this document, presenting relevant background research related to the use of the method and optimization of reinforcing steel in general for concrete structures, thereafter proposals of different optimization methods, both classical optimization and meta-heuristic methods will be regarded as possible approaches to apply the ISR, specifically Gradient Descent Optimization methods when one variable for the ISR is considered and meta-heuristics for more than one variable involved given their versatility and flexibility to adapt to different problems, particularly the Particle Swarm Optimization PSO method and the Genetic Algorithm GA. At the end, these solution approaches for the application of the ISR method will be compared for the testing of rectangular solid geometries with different analysis parameters in order to show how adaptable and feasible such ISR method might be using a proper optimization algorithm and analysis for its approach when designing reinforcing steel.

Research on 3D elastoplastic seismic performance of reinforced concrete special-shaped column frame

Yang Liu — Fri, 04 Sep 2020 22:01:37 +0200

The special-shaped column structure system has more advantages than the rectangular column system in terms of architectural design and actual use. As a relatively new structural form, the concrete special-shaped column structure has not accumulated enough engineering practical experience. In this study, the rotation-moment curve of the plastic hinge of special-shaped column frame element was defined, the coupled PMM hinge applied to the frame element was studied, and the yield surface of the hinge was drawn. On this basis, an elastoplastic pushover analysis was conducted on a 12-storey special-shaped column frame model, its failure under different earthquakes was simulated, and its seismic performance was studied. The work of this article can provide reference for the engineering application of special-shaped column frame structure.

A hybrid multi-output approach to optimisation of PVC pipe quality characteristics

Milos Papic — Wed, 02 Sep 2020 11:21:03 +0200

A hybrid multi-output approach which combined the Taguchi method and fuzzy logic was used in this research in order to optimise the mechanical and physical properties of PVC pipes. Eight techological parameters which mostly define the extrusion process were taken into consideration in order to obtain the best possible results for six measurable quality characteristics of PVC pipes. Eighteen experiments with the same number of different parameter value sets were conducted resulting in eighteen various PVC pipe samples. The sample from the second experiment showed the highest value of comprehensive output measure (COM = 0.615), while the lowest COM value (0.359) was noted with the sample no. 13. The results of ANOVA revealed that traction speed is the most significant parameter affecting multiple characteristics with contribution of 28.86%. The optimum combination of factors and their levels is A₁, B₃, C₃, D₂, E₂, F₃, G₃, H₂– the sample produced at traction speed of 8.8 m/min, nozzle temperature of 211℃, expander doser speed of 23.2 rpm, extruder screw speed of 17.5 rpm, coextruder screw speed of 40.6 rpm, barrel temperature of 178 ℃, extruder mixture doser speed of 28.1 rpm and the coextruder mixture doser speed of 36.4 rpm.

Seismic response analysis of earth-rock fill dam on deep overburden under viscoelastic boundary condition

Long Wang — Fri, 14 Aug 2020 10:57:58 +0200

The dynamic response characteristics of an earth-rock fill dam on a deep overburden are the focus of seismic research. In particular, evaluating the influence of the earthquake safety of the dam. A dynamic response analysis of earth-rock fill dam on a deep overburden based on viscoelastic boundary conditions was used to study the influence of boundary conditions (including fixed boundary conditions and viscoelastic boundary conditions). The results show that the fixed boundary condition greatly improves the dynamic response level of the dam during an earthquake and has no obvious influence on the distribution of the acceleration response in the dam and the foundation. The difference in the calculation results under the two boundary conditions is related to the seismic input characteristics and dynamic deformation characteristics of the soil material. An analysis of the acceleration response spectrum shows that the influence of the boundary conditions on the calculation results is limited to the magnitude level of the acceleration response, while the spectral characteristics of the vibration of the dam and the foundation do not have a significant impact. '''Key words:''' deep overburden; earth-rock fill dam; seismic response analysis; boundary conditions; comparative analysis

Computation of energy release rate for interfacial crack in orthotropic bimaterials

Salah Bouziane — Sun, 09 Aug 2020 12:29:04 +0200

The interfacial crack in bimaterials is a very interesting problem for composite materials and which has received particular attention from several researchers. In this study, we will propose a numerical modeling of the interfacial crack between two orthotropic materials using a special mixed finite element. For the calculation of the energy release rate, a technique, based on the association of the present mixed finite element with the virtual crack extension method, was used. The numerical model proposed, in this work, was used to study a problem of interfacial crack in bimaterials. Two cases were treated: isotropic and orthotropic bimaterials. The results obtained, using the present element, were compared with the values of the analytical solution and other numerical models found in the literature.

Design and fabrication of a drill guide template for total elbow arthroplasty

Milad Heidari — Wed, 22 Jul 2020 19:22:05 +0200

Optimum implant positioning and technique used for its alignment are vital parameters to improve clinical results. Visual cues and jigs are utilized in the recent surgical techniques, which lead to some errors in the flexion-extension axis identification. Surgeons have used computer-assisted surgery for the alignment of the hip, knee, and shoulder. However, there is a restricted application of this technology to the elbow. In this study, a technique was used to model a drill guide template to precisely place an implant in the bone. The computed tomography dataset was used to construct four different elbow bones, and an elbow implant was modeled. The surgical drill guides were designed based on the computed tomography data. The drill guide templates and constructed bones were fabricated, using a 3D printer. The accuracy of the surgical guides was validated experimentally. The results showed that the mean deviations between the achieved and planned positions of the hole at the bone apex and base of bones were less than those reported in previous studies in both medial/lateral and posterior/anterior positions. The low positioning errors observed in this study proposed that the implant’s location can be precisely aligned to its target using the introduced technique.

Lateral buckling of steel beams. Compared analysis of CTE DB SE-A, EAE and EC3 codes

Arianna Guardiola-Víllora — Wed, 15 Jul 2020 13:30:10 +0200

The Basic Document, Structural Safety, Steel of the Spanish Technical Building Code provides mathematical expressions to obtain the lateral buckling resistance of hot-rolled steel beams. These expressions include a coefficient, C₁, that accounts for variation of the bending moment along the beam. However, this document only provides values for linear diagrams of bending moments.

The instruction for Structural Steel, a copy of the latest version of Eurocode 3, does not include any method to obtain the elastic critical moment. On the contrary, a table with correction factors applicable to different types of bending moments diagrams is included.

In this document both procedures have been combined and results have been compared to those obtained using other versions of the Eurocode 3. Finally, tables have been provided to ease the design of hot-rolled steel beams while preventing the lateral buckling.

Keywords: Lateral buckling; Steel Beams; Spanish steel code; CTE DB SE-A; Spanish code EAE; Eurocode 3

Spare parts supply network optimization with uncertain distributed lead times and demands

Yadong Wang — Tue, 14 Jul 2020 03:24:40 +0200

'''In the spare parts supply network, there are many uncertain factories, such as unpredictable demands and changeable lead times. The spare parts shortage caused by those uncertainties may lead to severe losses. To solve the uncertainty of supply network, a determined optimization model is developed and then reformulated as a robust counterpart. In the robust model, it is only necessary to know the moment information of the uncertain parameters rather than the true probability distribution. The solution obtained by the robust model can satisfy the constraints in the worst-case, that is, feasible for any probability distribution within the moment based ambiguity set. Two moment based robust models are studied in this work. The result of the experiment indicates that the robustness of the robust model is stronger than that of the determined model and chance constraint model, and the effect of safety tolerance on the robustness is revealed by sensitivity analysis. Finally, the second order moment model is verified be superior to the first order moment model in spare parts supply network optimization.

Investigation on modeling and simulation BLDC motor fed universal actuation system

Murali M — Wed, 08 Jul 2020 10:14:05 +0200

This paper deals with mathematical modeling of Permanent magnet brushless DC (BLDC) motor in MATLAB-SIMULINK environment.

Modeling of BLDC motor carried in transfer function, transfer equations and state space model to verify the performance as actuators. Mathematical switches to control electronic commutation of BLDC motor based on signals of Hall Effect position sensor using three-phase inverter drive. Performance of the simplified mathematical inverter fed BLDC motor under steady state and dynamic conditions analyzed. Due to the switching losses during PWM generation generates low ripple content in torque of BLDC motor which described and eliminated through state space model. Comparison made of proposed modeling of BLDC motor with motor parameters like back-EMF, stator current and speed of BLDC motor, proposed work suggests the state space modeling holds a superior method for design of BLDC motor during high dynamic load performance and operating ranges.

Blind source separation of rotor vibration signals in high-noise environments

Yinjie Jia — Wed, 08 Jul 2020 07:37:24 +0200

During the operation of the engine rotor, the vibration signal measured by the sensor is the mixed signal of each vibration source, and contains strong noise at the same time. In this paper, a new separation method for mixed vibration signals in strong noise environment (such as SNR=-5) is proposed. Firstly, the time-delay auto-correlation de-noising method is used to de-noise the mixed signals, and then one common algorithm (MSNR algorithm is used here) is adopted to separate the mixed vibration signals, which can improves the separation performance. The simulation results verify the validity of the method. The proposed method provides a new idea for health monitoring and fault diagnosis of engine rotor vibration signals.

Analysis of short-circuit failures in synchronous machinery rotor using finite elements

Edgardo Arrieta — Wed, 01 Jul 2020 19:21:03 +0200

In this paper, a mathematical model using finite element software is developed. An electromagnetic analysis is performed to determine the behavior of quantities such as magnetic flux density and output voltage when short-circuit failures occur in the winding of the rotor poles of a synchronous small size machine when it works as a generator. The voltage values obtained from the simulations were compared with data from actual tests performed in the laboratory.

AED: a novel visual representation based on AR and empathy computing in manual assembly

Zhuo, Wang — Sat, 20 Jun 2020 13:36:04 +0200

Adding personal perceptions to manufacturing engineering can be very challenging, especially when engineering-based methods are used to make artisans understand the designer's ideas. Unfortunately, the two-dimensional engineering definition can be extremely time-consuming for individuals who lack creativity or imagination, and model-based definition would be incapable of breaking the separation between the virtual space and the real world, which makes the interaction between natural persons exist spatial perception error. The emergence of Augmented Reality (AR), which allows individuals to perceive the intentions and strategies of the designer with visual cues that are attached to actual objects, fills this gap. In this paper, augmented engineering definition (AED) is proposed to enhance the information exchange between natural persons in a succinct, accurate and acceptable form of visual impression. Motivated by visual representation in remote collaboration, the specific empathy scenario bases on the AED design, which leads to the establishment of a mapping relationship between the visual cues and the augmented information. An inquiry had been conducted by involving participants who were paired up for the parts’ inspection, interacting via 2D visualization data only, interaction with 3D projection data, interaction with 3D visualization data, AED-based communication. The experimental results showed that participants with AED exhibited higher situational appeal and information understanding than using three other interactions. Besides, we discussed the feasibility of using AED in a collaborative manufacturing environment and the impact on AED users.

Analysis of operability envelopes for subsea production tree installation

Chen Neng — Sat, 06 Jun 2020 15:08:02 +0200

The article presents a mathematical model to investigate the operability envelopes for subsea production tress (SPT) installation using drill pipe. The finite differential method was used to solve the established governing equations in which the ocean conditions were considered. Based on the evaluations of the ocean wave, ocean current, water depth, specification of drill pipe and SPT weight that might dominate the mechanical behaviors of the pipe, the operability envelopes with permissible ocean conditions for SPT installation were obtained. The results indicate that changes of depths in deep water and SPT weight have few effects on the operation conditions and it would be better to choose smaller pipe to obtain larger permissible ocean conditions during SPT installation.

Multi-body dynamics modeling and transient characteristics analysis for a folding wing

Yingge Ni — Thu, 28 May 2020 14:22:33 +0200

The investigation of modeling the time evolution of a folding wing during the morphing process and the dynamic characteristics analysis is carried out. The governing equations with uniform form are developed from the integration of floating frame method in multi-body dynamics and component mode synthesis in structural dynamics. The time-dependent aerodynamic force is taken into the governing equations. The equation achieves the time-dependent coupling between structure and aerodynamics and avoids the data transmission and low efficiency, which holds true for the multi-segmented folding wing. The relative parameters in constraint equations are easily modified to be applied to both slow and fast-varying processes for a folding wing. Also, the influence of the velocity and attack angle on transient responses can be investigated. Transient response analysis shows that slower morphing means more stable transient responses. The flexibility of the folding wing has the significant influence on transient responses. To some extent, the aerodynamic force can be beneficial to the morphing process.

Naturally ventilated industrial sheds: an investigation about the influence of wind direction in flow rate efficiency in continuous roof vents

Bruno Camargos — Wed, 20 May 2020 01:34:05 +0200

Natural ventilation portrays an effective technique for lowering the internal temperature, without spending electricity, and directly contributes to the renewal of indoor air by establishing a healthy environment for workers. Given this, it is usual to have air vent openings located at the top of the roof (continuous roof vents), in addition to those present on the facades of sheds. In naturally ventilated buildings, it is recommended to give due importance to the provision of these openings, since depending on the proposed arrangement, the wind may or may not help in the effectiveness of this strategy. In this work, it is evaluated via computer simulation (EnergyPlus, version 8.7.0), for the climatic conditions of the city of Belo Horizonte/Brazil, the influence of the wind direction in the flow rate of indoor air through the ridge vents, of the longitudinal and transversal type, present in industrial sheds endowed with an internal source of high-intensity heat release. The results obtained show that the flow rate has a symmetrical behavior in the openings of the longitudinal continuous roof vent, that is, when an opening is with the maximum outflow of the internal air, the opening opposite the predominant wind direction is acting as an entry point for the air external. The transverse continuous roof vents are more sensitive about the wind direction since they are positioned perpendicular to the building. The best result found is for the wind situation occurring parallel to the shed, obtaining a reduction in the internal temperature of up to 1°C, an increase in the rate of air changes per hour, in the internal environment, at 1acph, and an increase of up to 10,7% in the volume of air infiltrated into the shed.

Analysis of damage failure in uniaxial compressive of cemented paste backfill by ultrasonic pulse velocity test

Lin Li — Thu, 30 Apr 2020 09:09:05 +0200

Cemented paste backfill (CPB) is prepared by mixing cementitious materials, tailings and water. Uniaxial compressive strength (UCS) is one of the most commonly used indicators for evaluating the mechanical performance of CPB. Ultrasonic pulse velocity (UPV) testing which is a non-destructive measurement, can also be applied to determine the mechanical properties of cement-based materials such as CPB. In order to study the failure mechanism of CPB,144 CPB samples prepared at different mass fraction and cement-tailing ratios were subjected to the UCS and UPV tests at 7,14 and 28 days of curing age. The effect of cement-tailing ratio and mass fraction on the UCS and UPV of CPB samples were obtained, the UCS values were correlated with the corresponding UPV data. Microstructural analysis was also performed on CPB samples to understand the effect of microstructure on the UCS data. The results show that the UCS and UPV values of CPB increased with cement-tailing ratio, mass fraction and curing time. Based on the experimental results, the damage constitutive equations and the damage evolution equations of different backfills were proposed on the basis of damage mechanics. Moreover, comparative analysis of constitutive model and experimental results were made to verify the reliability of the damage model. The results acquired by this paper provide a scientific basis for the rational strength design of backfill mine.

Evaluation of an accidental-torsion design proposal considering firm-soil ground motions

Juan Manuel Zarza González — Tue, 14 Apr 2020 21:56:05 +0200

Using non-linear analyses and Monte Carlo simulations, a simplified accidental-torsion design procedure is evaluated. The design procedure does not use an accidental eccentricity like the building codes do. For the evaluation, four reinforced concrete frame building models of four and seven stories are dynamically studied in the nonlinear range. The models are subjected to a set of five firm-soil, bidirectional seismic records. The design procedure is evaluated by comparing the ductility demands of both beams and columns for three conditions of each building model: a) the torsionally balanced model without accidental torsion (model TB), which establishes the reference values of ductility demands; b) the same nominal model but incorporating accidental torsion via the Monte Carlo method; and c) a model with amplified strength (model AS) according to the accidental-torsion design procedure to be evaluated. Results indicate that there is a probability smaller than 2.5% that accidental torsion can cause ductility demands approximately 20% to 25% larger than those of similar building models without accidental torsion. A comparison of ductility demands for the reference models without accidental torsion and those of models with accidental torsion and designed with the procedure that is evaluated, reveals that the design procedure is effective to control the effects of accidental torsion.

Generalized finite difference solution for the Motz Problem

Francisco Javier Domínguez Mota — Sun, 12 Apr 2020 20:28:10 +0200

In this paper, it is presented a formulation of a generalized finite difference scheme to solve the Motz problem. It is based on a general difference scheme defined by an optimality condition, which has been developed to solve Poisson-like equations whose domains are approximated by a wide variety of grids over general regions. Numerical examples showing second-order accuracy of the calculated solutions are presented.

Siphon pipe parameter optimization of the toilet using CFD-DEM coupling method

Zhanfu Li — Fri, 20 Mar 2020 08:44:18 +0100

The computational fluid dynamics (CFD) and discrete element method (DEM) coupling method is used to simulate the flushing process of the toilet and this paper analyzes the influence of different structural parameters of siphon pipe on the flushing performance of the toilet. And through the adjusted-parameters toilet, tlushing experments were carried out to verify the simulations. Meanwhile the orthogonal test of different structural parameters of siphon pipes were conducted to study the flushing Performance. The research results show that the CFD-DEM coupling method can be used to study the regularity of the toilet flushing performance. The toilet can get the better flushing performance when the tilt angle of the angle of inclination is 50°, the curvature width and length are 50 mm and 220 mm, the width and height of the secondary water seal are 100 mm and 25 mm and pipe diameter is 53 mm. The method in this paper can provide a new idea for the study and design of the flushing performance of the toilet.

Approximation of the transport of pollutants with reaction terms in shallow waters using finite elements

Ramon Codina — Thu, 05 Mar 2020 08:27:04 +0100

In this article we present the approximation of the coupled model of the equations of motion of a fluid in shallow waters with the convection-diffusion-reaction (CDR) equation of pollutant transport. This approximation is carried out using high order finite elements and using stabilised variational sub-scale methods. We write the coupled system of equations, previously discretised in time and linearised, as a transient vector equation of CDR. The stabilised finite element methods used are the known ASGS and OSS sub-scale methods, the same ones that allow us to use the same interpolation for all unknowns, as well as to deal with dominant convection and reaction flows. We consider the possibility of non-linearity in both the convective and reaction terms. We will not consider the possible development of shocks in the solution. In order to examine the accuracy and robustness of the ASGS and OSS methods, we present four test cases: mesh convergence, transport of a pollutant in a square cavity, transport of a pollutant in the Gulf of Roses and at the river Guadalquivir mouth, and the predator-prey model, which can be written as a transient CDR vector equation with non-linearity in the reaction term.

An historical perspective on the development of forest planning models with emphasis on operational level

Paulo Amaro V. H. dos Santos — Fri, 28 Feb 2020 19:51:02 +0100

The application of operations research techniques has led to a substantial improvement in the economic and ecologic efficiency of forest management, both for planted and natural forests. Forest planning addresses problems in different hierarchical levels that involve specific planning horizons and formulation complexity. This study proposes an historical perspective on the development of forest planning models in the last five decades, with a focus on the operational level. The emergence of operations research applied to forest planning problems can be dated back to the 60’s, with an intensification of this line of research on the 80’s and 90’s, accompanying the fast development on the available computing power. In the 90’s, forest planning problems started to be classified according to hierarchical levels in strategic, tactical and operational. While the strategic and tactical levels address decisions on the long- and medium-term, the operational level deals with short-term decisions, typically involving harvesting machinery allocation and transportation of forest products. In this sense, the operational planning is characterized by a high level of complexity of the planning models and economic importance to forest management. We conclude that despite the increasing number of publications related to forest planning, the operational level remains underrepresented and efforts to integrate decisions across the different hierarchical levels of forest planning are required.

Evaluation of monthly rainfall calculated with TRMM for meteorological drought studies

Leticia del Valle Vicario — Wed, 08 Jan 2020 16:20:06 +0100

Precipitation is considered the main variable for the evaluation of meteorological drought in a basin. Droughts is a phenomena of different spatial scale, so that is convenient to have simultaneous rainfall records in time and in different locations, in order to analyze their evolution in space, depending on the size and the variability of the characteristics in the basin. In Argentina, specifically in the central region, the availability of information on the spatial variability of rainfall is not usual, so drought studies in this region are limited. Due to this it is convenient to validate the rainfall information obtained through satellite missions. The present work evaluates the validity and applicability of monthly rainfall data estimated through TRMM in ten stations in the basin of the Carcarañá river in the central region of Argentina and its subsequent application to studies on meteorological droughts through a representative index (SPI). Statistical parameters such as the concordance coefficient, the correlation coefficient and the bias were used for this analysis. There was a significant variation of the parameters with respect to the height. Was observed better coefficients in stations located in plain compared with stations located in mountainous areas.

Hydraulic modeling of combined sewers overflow integrating the results of the SWMM and CFX models.

Juan Carlos Ruge C. — Fri, 15 Nov 2019 23:10:04 +0100

This study proposes a methodology for the calibration of combined sewer overflow (CSO), incorporating the results of the three-dimensional ANSYS CFX model in the SWMM one-dimensional model. The procedure consists of constructing calibration curves in ANSYS CFX that relate the input flow to the CSO with the overflow, to then incorporate them into the SWMM model. The results obtained show that the behavior of the flow over the crest of the overflow weir varies in space and time. Therefore, the flow of entry to the CSO and the flow of excesses maintain a non-linear relationship, contrary to the results obtained in the one-dimensional model. However, the uncertainty associated with the idealization of flow methodologies in one dimension is reduced under the SWMM model with kinematic wave conditions and simulating CSO from curves obtained in ANSYS CFX. The result obtained facilitates the calibration of combined sewer networks for permanent or non-permanent flow conditions, by means of the construction of curves in a three-dimensional model, especially when the information collected in situ is limited.

Development of a refinement algorithm for tetrahedral finite elements

Armando Hermosillo-Arteaga — Tue, 15 Oct 2019 05:56:04 +0200

Many of the engineering problems are analyzed using numerical methods such as the finite element (FEM) whose results provide a basis to make basic decisions regarding the design of many important works. accepted It is generally that FEM computations are reliable; however, the results may be affected by the definition of the finite element mesh, this is particularly true when the internal and external boundaries are time dependent, as is the case of soil consolidation. Accordingly, a thorough investigation was carried out with the main purpose of eliminating this inconvenience. The main steps to carried out the development of the innovative geometric procedure to automatically refine finite element tetrahedra-type (3D) are described. This geometric algorithm is based on the theory of fractals and is a generalization of the algorithm for triangular element finite element meshes (2D) [1, 2]. This paper presents the fundaments of this new algorithm and shows its great approximation using 3D close form solutions, and its versatility to adapt the original Finite Element Mesh when the load boundary conditions are modified (Neumann conditions).

EMPOWERING, a smart Big Data framework for sustainable electricity suppliers

Jordi Cipriano — Mon, 19 Nov 2018 09:47:02 +0100

This paper presents the EMPOWERING project, a Big Data environment aimed at helping domestic customers to save electricity by managing their consumption positively. This is achieved by improving the information received about energy bills and offering online tools. The main contributions of EMPOWERING are the creation of a novel workflow in the electricity utility sector regarding the implementation of data analytics for their customers and the fast implementation of data-mining techniques in massive datasets within a Big Data platform to achieve scalability. The results obtained show that EMPOWERING can be of use for customers of electrical suppliers by changing their energy habits to decrease consumption and so increase environmental sustainability. Index Terms—Big-data, Electricity supply industry, Sustainable development, Domestic consumption