Abstract

In this study, performance assessment of selected gas turbine power plants in Nigeria was evaluated using performance indices. The results of the study showed that for the period under review (2006–2010), the percentage shortfalls from the target energy in the selected power plants range from 26.33% to 86.61% as against the acceptable value of 5–10%. The capacity factor of the selected power plants varies from 16.88% to 73.67% as against the international value of 50–80%. The plant use factor varies from 45.89% to 97.03% and the utilization factor varies from 6.31% to 93.074% as against the international best practice of over 95%. From this result, it can be concluded that the generating units were underutilized. This is due to inadequate routine maintenance and equipment fault development. The analyses of reliability indicators revealed that the mean time between failures varies from 5.42 to 378.44 h, the mean time to repair varies from 18.3 to 153.88 h and the plant availability varies from 12.86% to 91.31% as against the Institute of Electrical and Electronics Engineers recommended standard of 99.9%. Evaluation of operating figures of the selected power plants revealed that starting reliability (SR) and operating reliability vary from 71.95% to 93.9% and 5.33% to 55%, respectively. The SR of the selected power plants is low in value compared with standard value of 99.9%. The statistical analysis carried out on plant availability revealed that at 95% confidence level, there is a significant difference in availability of the selected power plants. This indicates differences in their systems installation, operation and maintenance. The performance indicator developed to evaluate the performance indices for the selected stations can also be applicable to other power stations in Nigeria and elsewhere. Measures to improve the performance indices of the plants have been suggested in this paper.

Abstract

[EN] This paper is dedicated to the structure of airline networks as a sink of efficient airline operations. Parameters of complexity were derived and mirrored on level of service as well as efficiency parameters. Airlines usually considerers an operational overhead to predict the total flight operation cost. This parameter includes the expected cost for disruptions and delays. When an airline has to mobilize an aircraft in a base for recovering the service or for breaking an emergent dynamic, then it is running extra costs. The cost of managing complexity in the airline industry has a direct impact on profit and loss account. Therefore, this paper presents an integrated approach to evaluate this cost, based on padding and aircrafts dedicated to recover disruptions. Finally, some additional indicators are derived to evaluate reliability improvement as part of complex performance. Trapote-Barreira, C.; Deutschmann, A.; Robusté, F. (2016). Managing airlines: the cost of complexity. En XII Congreso de ingeniería del transporte. 7, 8 y 9 de Junio, Valencia (España). Editorial Universitat Politècnica de València. 25-35. https://doi.org/10.4995/CIT2016.2015.4092 OCS 25 35

Abstract

How many Teslas will it take to crash the Los Angeles, California, grid? This thesis conducts a thought experiment to explore whether rapid adoption of electric vehicles (EVs) in Los Angeles will reduce the reliability of electric power in the Los Angeles Department of Water and Power (LADWP) service territory. Federal and state regulations are encouraging the shift to electric transportation in support of policy priorities that include reducing greenhouse gas emissions and reducing dependence on foreign energy sources. However, high market penetration by EVs will change the patterns of electricity use, especially in urban areas. Under some scenarios, EVs could pose a risk to the reliability and resilience of the electric grid serving these areas. To explore this issue, I developed a model that projects the impact of EVs on the peak power load in Los Angeles in 2030 under different scenarios of EV market penetration and constraints on demand for vehicle charging (e.g., time-of-day pricing). I found that even with moderate EV penetration, if vehicle charging is unconstrained, the load placed on the LADWP grid will exceed the established reserve margin in 2030. Only by adopting some form of incentives for EV drivers to shift their power demands from the normal end-of-day charging routine will the LADWP be able to maintain the reliability and resilience of the power grid. http://archive.org/details/hittingtheaccele1094563490 Civilian, Department of Homeland Security Approved for public release; distribution is unlimited.

Abstract

This article presents results of a study based on the analysis of the development of the theory of reliability whose indicators are formulated indicators of transport systems reliability and contributed to building a system of factors determining their reliability. It is established that the formation of the theory of reliability of transport systems today is not completed. Based on the specifics of the systems, new reliability indicators were proposed and substantiated such as emergency downtime and reliability of emergency downtime. On the basis of the performed studies, it was found that the specifics of the transport process require the introduction of emergency downtime close to the recovery time and the reliability of emergency downtime. It is necessary to introduce two close parameters such as the average recovery time and the average emergency idle time. They are associated with the need to distinguish between the idle time of a technological system, or a separate element when a failure occurs, and the idle time that is needed. For the technological links of the transport system, the main purpose of which is to ensure efficient operation transport process, the probability of emergency downtime can serve as a criterion for assessing their reliability.

Abstract

The „Finkenwerder Ring“ is an important traffic junction in the Port of Hamburg – however, a lot of accidents per year impair traffic safety and reliability. The current traffic management, the signage, and the high number of lanes might be causal for the many crashes. Therefore, a requirements analysis was conducted to investigate the current traffic situation of the Finkenwerder Ring. Based on these results possible countermeasures were identified and subsequently implemented in a reproduction of the Finkenwerder Ring in a driving simulation. Four variations of the Finkenwerder Ring were realized which differ in signage and roadway geometry and were evaluated in a driving simulator study with N=30 participants. Even a small implementation like a modification of signage is able to have positive effects on drivers’ evaluations. However, a quite expensive and complex solution (the separation of traffic streams via an additional traffic light) shows the largest effect. These results show the benefit of driving simulation as a tool for roadway design.

Abstract

Mapping a pipelined application onto a distributed and parallel platform is a challenging problem. The problem becomes even more difficult when multiple optimization criteria are involved, and when the target resources are heterogeneous (processors and communication links) and subject to failures. This report investigates the problem of mapping pipelined applications, consisting of a linear chain of stages executed in a pipeline way, onto such platforms. The objective is to optimize the reliability under a performance constraint, i.e., while guaranteeing a threshold throughput. In order to increase reliability, we replicate the execution of stages on multiple processors. We present complexity results, proving that this bi-criteria optimization problem is NP-hard. We then propose some heuristics, and present extensive experiments evaluating their performance.

Abstract

"jats:p"The problem of safety of the flight operations will be valid as long as there will be aviation, both civil and military. Ensuring the safety was, is and will be one the most important issues in the functioning and development of aviation."/jats:p" "jats:p"The safety of flight operations affect the implementation of all the elements involved in this process, which can be summarized in three groups, namely: man, the aircraft and the environment, including "jats:bold"airfield pavements"/jats:bold". Airfield pavements are elements that can be intentionally destroyed by military action as well as a result of random unexpected situation (failure, catastrophe, natural disaster). The reconstruction of airfield pavements in crisis situations and in military operations should enable to restore the operational availability of destroyed elements in the shortest possible time. Document type: Article

Abstract

"jats:p"The purpose of this paper was to present a reliability comparison of two types of city transport buses. Case study on the example of the well-known brands of city buses: Solaris Urbino 12 and Mercedes-Benz 628 Conecto L used at Municipal Transport Company in Lublin was presented in details. A reliability index for the most failure parts and complex systems for the period of time failures was determined. The analysis covered damages of the following systems: engine, electrical system, pneumatic system, brake system, driving system, central heating and air-conditioning and doors. Reliability was analyzed based on Weibull model. It has been demonstrated, that during the operation significant reliability differences occur between the buses produced nowadays. Document type: Article

Abstract

In the paper, we address Bayesian sensitivity issues when integrating experts’ judgments with available historical data in a case study about strategies for the preventive maintenance of low-pressure cast iron pipelines in an urban gas distribution network. We are interested in replacement priorities, as determined by the failure rates of pipelines deployed under different conditions. We relax the assumptions, made in previous papers, about the prior distributions on the failure rates and study changes in replacement priorities under different choices of generalized moment-constrained classes of priors. We focus on the set of non-dominated actions, and among them, we propose the least sensitive action as the optimal choice to rank different classes of pipelines, providing a sound approach to the sensitivity problem. Moreover, we are also interested in determining which classes have a failure rate exceeding a given acceptable value, considered as the threshold determining no need for replacement. Graphical tools are introduced to help decisionmakers to determine if pipelines are to be replaced and the corresponding priorities. Document type: Article

Abstract

"jats:p"For a safe overtaking manoeuvre on two-lane highways, drivers need a sufficient sight distance along the roadway, but it depends on the traffic environment. To provide an adequate Passing Sight Distance (PSD), a number of models have been proposed since the initial model introduced by American Association of State Highways and Transport Officials (AASHTO) in 1954. It is a current design practice in Sri Lanka as well, however, not validated for local traffic conditions. This paper will present an alternative PSD model and an evaluation of AASHTO model for national highway design. Experiment was based on GPS data collection. In conclusion, PSD demand was satisfied by AASHTO PSD under mix traffic conditions, but not the safety concerns for speeds greater than 80 km/h, while alternative model successful for all speeds. Document type: Article