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Oteyaka, Hasan Candan. "Optimal cost and availability replacement models for multi-component systems." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25613/25613.pdf.
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Placzek, Tina Simone. "Optimal shelf availability : Analyse und Gestaltung integrativer Logistikkonzepte in Konsumgüter-Supply chains /." Wiesbaden : Dt. Univ.-Verl, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015918906&line_number=0002&func_code=DB_RECORDS&service_type=MEDIA.
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Wibowo, Rulianda Purnomo. "Optimal irrigation strategy with limited water availability accounting for the risk from weather uncertainty." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/34148.
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Doctor of PhilosophyDepartment of Agricultural Economics
Nathan P. Hendricks
Risk averse farmers face a substantial challenge managing irrigation water when they face limited water availability. The two primary reasons for limited water availability in the High Plains Aquifer region of the United States are limited well capacity (i.e., the rate at which groundwater can be extracted) or a constraint imposed by a policy. In this dissertation, I study how risk averse farmers optimally manage limited water availability in the face of weather uncertainty and also the impact of limited water availability on farmer welfare. I use AquaCrop, a daily biophysical crop simulation model, to predict corn yield under alternative irrigation scenarios with historical weather. Since no simple functional form exists for the crop production function, I use discrete optimization and consider 234,256 potential irrigation strategies. I also account for risk preferences by using expected utility analysis to determine the optimal irrigation strategy. Using a daily biophysical model is important because water stress in a short period of the growing season can impact crop yield (even if average water availability throughout the growing season is sufficient) and well capacity is a constraint on daily water use. The daily biophysical crop simulation model accounts for the dynamic response of crop production to water availability. First, I examine how optimal irrigation strategies change due to limited water availability. I find that it is never optimal for irrigators to apply less than a particular minimum instantaneous rate per irrigated acre. An optimal required instantaneous rate implies that a farmer with a low well capacity focuses on adjustment at the extensive margin. On the other hand, farmers who initially have a high well capacity should adjust at the intensive margin in response to well capacity declining. I also find that total water use increases as the degree of risk aversion increases. More risk averse farmers increase water use by increasing irrigation intensity to reduce the variance in corn yields. Another important finding is that a higher well capacity could actually promote less water use because the higher well capacity allows a greater instantaneous rate of application that allows the farmer to decrease irrigation intensity while still maintaining or increasing corn yield. This finding may imply an accelerated rate of groundwater extraction when the groundwater depletion reaches a particular threshold. Second, I analyze the welfare loss due to limited water availability. The relationship between welfare loss and well capacity due to a policy constraint differs by soil type. I found the welfare loss from a water constraint policy does not always increase as well capacity increases. Farmers with very high well capacity may make small or no adjustment at the extensive margin due to a higher instantaneous rate and higher soil water holding capacity. However, that is not the case for a farmer with land that has lower soil water holding capacity as the increase in well capacity results in greater welfare loss. I also investigate the effect of risk averse behavior on the magnitude of welfare loss. I found that the welfare loss per unit of reduced water use is lower for the farmer with more risk aversion. Thus, economic models that ignore risk aversion misestimate the cost of reducing water use. Finally, I investigate the incentive for adopting drip irrigation and its effect on water use. I find that a decrease in well capacity increases the benefits of adopting drip irrigation but is not sufficient to overcome the high initial investment cost without government support. While subsidies of the magnitude offered by current U.S. programs are sufficient to induce drip irrigation adoption, I find that such subsidies have the unintended consequence of increasing total water use, particularly for small well capacities.
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Savatovic, Anita, and Mejra Cakic. "Estimating Optimal Checkpoint Intervals Using GPSS Simulation." Thesis, Linköping University, Department of Mathematics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8558.
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In this project we illustrate how queueing simulation may be used to find the optimal interval for checkpointing problems and compare results with theoretical computations for simple systems that may be treated analytically.
We consider a relatively simple model for an internet banking facility. From time to time, the application server breaks down. The information at the time of the breakdown has to be passed onto the back up server before service may be resumed. To make the change over as efficient as possible, information of the state of user’s accounts is saved at regular intervals. This is known as checkpointing.
Firstly, we use GPSS (a queueing simulation tool) to find, by simulation, an optimal checkpointing interval, which maximises the efficiency of the server. Two measures of efficiency are considered; the availability of the server and the average time a customer spends in the system. Secondly, we investigate how far the queueing theory can go to providing an analytic solution to the problem and see whether or not this is in line with the results obtained through simulation.
The analysis shows that checkpointing is not necessary if breakdowns occur frequently and log reading after failure does not take much time. Otherwise, checkpointing is necessary and the analysis shows how GPSS may be used to obtain the optimal checkpointing interval. Relatively complicated systems may be simulated, where there are no analytic tools available. In simple cases, where theoretical methods may be used, the results from our simulations correspond with the theoretical calculations.
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Ellison, Brooke. "Development of nutrition resources in a smartphone application to promote optimal energy availability in collegiate endurance runners." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10108184.
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The purpose of this directed project is to develop nutrition resources aimed at optimizing energy status in male and female elite collegiate endurance runners. Specifically, this project includes personalized meal plans and a post-workout meal suggestion matrix that will be featured within a goal-based smartphone app called “Run Fueled.” A Formative Evaluation Survey was conducted. An expert panel of three Registered Dietitians completed the survey, and their opinions were determined using a 5-point Likert scale. Overall, the expert panel tended to agree with the specific evaluation items, indicating that the nutrition resources were appropriate and useful for the intended audience. In the future, a research project or qualitative assessment may be conducted on the endurance runners using “Run Fueled” to determine the effectiveness of the nutrition resources.
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Bright, John Charles. "Optimal control of irrigation systems : an analysis of water allocation rules." Lincoln College, University of Canterbury, 1986. http://hdl.handle.net/10182/2089.
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A feasibility study of an irrigation development proposal should include an analysis of the effects of water supply conditions on the degree to which development objectives are expected to be realised. A method of making this analysis was developed based on procedures for solving two problems. These were; (a) optimally allocating a property's available supply of water among competing crops, and, (b) optimally controlling an open channel distribution system to meet temporally and spatially varying water demand. The procedure developed for solving (a) was applied. A stochastic dynamic programming procedure was developed to optimally schedule the irrigation of a single crop, subject to constraints on the timing of water availability and total application depth. A second procedure was developed, employing a constrained differential dynamic programming algorithm, for determining optimal irrigation schedules for use with variable application depth systems, and when several crops compete for an intra-seasonally limited supply of water. This procedure was called, as frequently as water supply conditions allowed, to provide short-term irrigation schedules in a computer simulation of the optimal irrigation of several crops. An application system model was included in these procedures to transform a crop water-use production function into the required irrigation water-use production function. This transformation was a function of the application device type and the mean application depth. From an analysis of the on-property effects of water supply conditions, it was concluded that in order to achieve high economic and irrigation efficiencies, water supply conditions must be sufficiently flexible to allow the application system operator to vary the mean application depth but not necessarily the time periods of water availability. Additionally, irrigation scheduling procedures which seek economically optimum strategies offer the potential to achieve a maximum level of net benefit at levels of water availability significantly lower than has previously been used for design purposes.
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Satir, Benhur. "An Analysis Of Benefits Of Inventory And Service Pooling And Information Sharing In Spare Parts Management Systems." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12612073/index.pdf.
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Inventory management and production control problem of a dealer operating in a decentralized
spare parts network is analyzed in this dissertation. Spare parts network is
assumed to be formed of two dealers and the problem of a dealer is considered under
the assumption that the other dealer has a known policy. These dealers collaborate
through inventory and service pooling. Furthermore, the dealers collaborate through
sharing information on the net inventory status.
Upon demand arrival, a dealer may request a part from the other dealer, in which
case a payment is made. Under this competitive and collaborative environment, the
optimal operating policy of an individual dealer is characterized under full information.
Through computational analysis, the conditions under which the dealer under
consideration is most profitable are identified. Finally, by comparing dierent pooling
strategies and several information availability levels, the benefit of information
sharing is quantified.
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Zhou, Ling. "Availability analysis and optimization in optical transport networks /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17191.
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Levander, Fredrik, and Per Sakari. "Design and Analysis of an All-optical Free-space Communication Link." Thesis, Linköping University, Department of Science and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1198.
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Free Space Optics (FSO) has received a great deal of attention lately both in the military and civilian information society due to its potentially high capacity, rapid deployment, portability and high security from deception and jamming. The main issue is that severe weather can have a detrimental impact on the performance, which may result in an inadequate availability.
This report contains a feasibility study for an all-optical free-space link intended for short-range communication (200-500 m). Laboratory tests have been performed to evaluate the link design. Field tests were made to investigate availability and error performance under the influence of different weather conditions. Atmospheric impact due to turbulence related effects have been studied in detail. The most crucial part of the link design turned out to be the receiver optics and several design solutions were investigated. The main advantage of an all-optical design, compared to commercially available electrooptical FSO-systems, is the potentially lower cost.
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Sharma, Ameeth. "Performance comparison of two dynamic shared-path protection algorithms for WDM optical mesh networks." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01262009-141918/.
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Palkopoulou, Eleni. "Homing-Architekturen für Multi-Layer Netze: Netzkosten-Optimierung und Leistungsbewertung." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-101633.
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Die schichtenübergreifende Steuerung von Multi-Layer Netzen ermöglicht die Realisierung fortgeschrittener Netzarchitekturen sowie neuartiger Konzepte zur Steigerung der Ausfallsicherheit. Gegenstand dieser Arbeit ist ein neues ressourcensparendes Konzept zur Kompensation von Core-Router-Ausfallen in IP-Netzen. Core-Router-Ausfälle führen zur Abkopplung der an Ihnen angeschlossenen Zugangsrouter vom Netz. Daher werden die Zugangsrouter üblicherweise mit jeweils zwei oder mehreren verschiedenen Core-Routern verbunden (engl.: dual homing) was jedoch eine Verdoppelung der Anschlusskapazität im IP Netz bedingt. Bei dem neuen Verfahren - Dual Homing mit gemeinsam genutzten Router-Ersatzressourcen (engl.: dual homing with shared backup router resources, DH-SBRR) - erfolgt die Zugangsrouter-Anbindung zum einen zu einem Core-Router des IP-Netzes und zum anderen zu einem Netzelement der darunterliegenden Transportschicht. Damit lassen sich Router-Ersatzressourcen, die im IP-Netz an beliebigen Stellen vorgehalten werden können, uber das Transportnetz an die Stelle eines ausgefallenen Core-Routers schalten. Die Steuerung dieser Ersatzschaltung geschieht über eine schichten übergreifende, d.h. das Transportnetz- und IP-Netz umfassende Control-Plane - beispielsweise auf Basis von GMPLS. Da beim Umschalten der Routerressourcen auch aktuelle Zustände (bspw. Routing-Tabellen) auf die Router-Ersatzressourcen mit übertragen werden müssen, beinhaltet das neue Verfahren auch Konzepte zur Router-Virtualisierung. Zum Vergleich und zur Bewertung der Leistungsfähigkeit des neuen DH-SBRR Verfahrens werden in der Arbeit verschiedene Zugangsrouter-Homing-Varianten hinsichtlich Netz-Kosten, Netz-Verfügbarkeit, Recovery-Zeit und Netz-Energieverbrauch gegenübergestellt. Als Multi-Layer Netzszenarien werden zum einen IP über WDM und zum anderen IP über OTN (ODU) betrachtet. Zur Bestimmung der minimalen Netz-Kosten ist ein generisches Multi-Layer Netzoptimierungsmodell entwickelt worden, welches bei unterschiedlichen Homing-Architekturen angewendet werden kann. Neben dem Optimierungsmodell zur Netzkostenminimierung wird auch eine Modellvariante zur Minimierung des Energieverbrauchs vorgestellt. Um die Rechenzeit für die Lösung der Optimierungsprobleme zu verringern und damit auch größere Netzszenarien untersuchen zu können bedarf es heuristischer Lösungsverfahren. Im Rahmen der Arbeit ist daher eine neue speziell auf die Multilayer-Optimierungsprobleme zugeschnittene Lösungsheuristik entwickelt worden. Aus der Netzkosten-Optimierung ergibt sich, dass durch den Einsatz von DH-SBBR signifikante Kosteneinsparungen im Vergleich zu herkömmlichen Homing-Architekturen realisiert werden können. Änderungen der Verkehrslast, der Kosten der IP-Netzelemente oder der Netztopologie haben keinen signifikanten Einfluss auf dieses Ergebnis. Neben dem Kosten- und Energieeinsparungspotential sind auch die Auswirkungen auf die Netz-Verfügbarkeit und die Recovery-Zeit untersucht worden. Für die Ende-zu-Ende Verfügbarkeit bei Anwendung der verschiedenen Homing-Architekturen Können untere Grenzwerte angegeben werden. Zur Bestimmung der Recovery-Zeit bei Einsatz von DH-SBRR ist ein eigenes analytisches Berechnungsmodell entwickelt und evaluiert worden. Damit kann das DH-SBRR Verfahren zur Einhaltung vorgegebener Recovery-Zeiten (wie sie für bspw. Für bestimmte Dienste gefordert werden) entsprechend parametriert werdenThe emergence of multi-layer networking capabilities opens the path for the development of advanced network architectures and resilience concepts. In this dissertation we propose a novel resource-efficient homing scheme: dual homing with shared backup router resources. The proposed scheme realizes shared router-level redundancy, enabled by the emergence of control plane architectures such as generalized multi-protocol label switching. Additionally, virtualization schemes complement the proposed architecture. Different homing architectures are examined and compared under the prism of cost, availability, recovery time and energy efficiency. Multiple network layers are considered in Internet protocol over wavelength division multiplexing as well as Internet protocol over optical data unit settings - leading to the development of multi-layer optimization techniques. A generic multi-layer network design mathematical model, which can be applied to different homing architecture considerations, is developed. The optimization objective can be adapted to either minimizing the cost for network equipment or the power consumption of the network. In order to address potential issues with regard to computational complexity, we develop a novel heuristic approach specifically targeting the proposed architecture. It is shown that significant cost savings can be achieved - even under extreme changes in the traffic demand volume, in the cost for different types of network equipment, as well as in the network topology characteristics. In order to evaluate occurring tradeoffs in terms of performance, we study the effects on availability and recovery time. We proceed to derive lower bounds on end-to-end availability for the different homing architectures. Additionally, an analytical recovery time model is developed and evaluated. We investigate how service-imposed maximum outage requirements have a direct effect on the setting of the proposed architecture
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Kvíčala, Radek. "CHYBOVOST A DOSTUPNOST ATMOSFÉRICKÝCH OPTICKÝCH SPOJŮ." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233454.
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This dissertation deals with the problematic of the free space optical link availability determination. For the presumption of the free space optical link unavailability we have to know statistical distribution of the atmospheric attenuations. In this work is also presented the measurement of these atmospheric attenuations with the specially designed optical link. Measurement is using switching of the two separate transmitters with wavelengths of 830 nm and 1550 nm. Presented statistic distribution let us determine the suitability of the link in the chosen locality during its design. Comparison of our measurement with other models like model based on the meteorological visibility is also presented. The last part of this work is focused on the preconditions for the hi-speed network bit error rate determination. Sample of the bit error rate measurement obtained by our designed bit error rate tester is attached.
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Vaněk, Jiří. "Kvalita služeb a kvalita zážitku pro sítě nové generace." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377148.
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The thesis sums up the traffic parameters for the evaluation of next-generation access networks. There are mentioned parameters for service quality management and parameters for measuring the quality of experience. The EU regulation on High Speed Internet in the Czech Republic is analyzed. The practical part compares the results between the implementation of the quality management of services and without implementation. Also there is comparing theoretical and practical transmission rates of physical ports. Part of the thesis is a questionnaire focused on the quality of experience of the video sequence.
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Huang, Chi-Jen, and 黃琦蓁. "Evaluation Water Availability Using Reliability-Based Optimal Streamflow Allocation Model." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/56431472295276817227.
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博士國立臺灣大學
土木工程學研究所
105
Deterministic approaches are difficult to apply when simulating water availability and reliability because of the natural stochastic variability of streamflow and water withdrawals. A reliability-based optimal streamflow allocation model was developed in this study using flow duration curves (FDCs) to evaluate allocations of streamflow and their associated reliabilities for each water abstraction location and water availability in the basin. The developed model is a chance constraint programming model, which was solved by mixed integer linear programming. In order to estimate the FDCs at ungauged locations, hydrologic regions were delineated to select streamflow gaging stations in the first place. Twenty-two river basins in Taiwan with major demands were grouped into homogeneous regions using principal component analysis (PCA), cluster analysis (CA), and discriminant analysis (DA). The dividing line between two adjacent river basins was easier to differentiate by combining adjacent river basins to form several contiguous regions and comparing their clustering results. Second, models were built for FDC estimations, applying three regression methods including the traditional multiple linear regression (MLR), principle component regression (PCR), and partial least squares regression (PLSR). A comparison of the model performances obtained using a cross-validation procedure showed some unstable conditions for MLR in the regional regression models for estimating the FDC; this was due to the variation of selected variables among percentile flows. The PCR and PLSR approaches can address the difficulties of variable selection and achieve a more robust model of FDC estimation. Optimal streamflow allocation model was applied to the Wu River, situated in the central part of Taiwan. First, Wu River catchments were divided into 661 sub-catchments as hydrological units for allocating streamflow. Based on the streamflow gaging stations in the hydrologic homogeneous region, regional regression models for estimating the FDC were built using PLSR method. The FDC estimation results of each hydrological unit in the river basin were taken as the initial values before allocating streamflow. Second, optimal streamflow allocation model was developed according to the upstream and downstream relationships of hydrological units. The allocation of streamflow and their associated reliabilities for 130 existing withdrawal sites and water availability for each hydrological units were solved by the optimal model. Finally, optimal streamflow allocation model was applied to evaluate the instream flow reserved by a new reservoir and their influence on the downstream existing withdrawal sites.
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Liao, Lu-Wen, and 廖祿文. "Optimal Parallel Machine Scheduling with Machine Availability and Eligibility Constraints." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/26969310513500353108.
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博士國立中央大學
工業管理研究所
95
In this dissertation we consider the parallel machine scheduling problem with machine availability and eligibility constraints under a given planning horizon. Machine availability constraint indicates that each machine is not continuously available at all times throughout the planning horizon; machine eligibility constraint means that each job can only be processed on specified machines. We observe that there is a little published works in machine scheduling considered machine availability and eligibility constraints simultaneously. But this type of scheduling problem can be found in some practical environments, such as TV advertising scheduling and the testing of fabricated wafers in semiconductor manufacturing. In this dissertation, therefore, we extend the existing works to consider the following three types of scheduling problems with machine availability and eligibility constraint simultaneously. We first consider the first type of the scheduling problem where the objective is to minimizing the maximum makespan (Cmax). Then, we consider the second type of scheduling problem where the objective is to minimizing the minimum lateness (Lmax). Finally, we extend the result of the second type of scheduling problem to deal with the more general scheduling problem where the job preemption is not allowed. For the minimization of Cmax, we utilize a network flow approach to formulate the scheduling problem into a series of maximum flow problem, and propose a polynomial time algorithm to solve the scheduling problem optimally. For the minimization of Lmax, we first introduce the concept of the critical values, and then apply the network flow approach for developing a two-phase binary search algorithm to solve the problem optimally. Finally, we extend the result of the second type of scheduling problem to derive a lower bound of the scheduling problem in which job preemption is not allowed; and then we investigate the characteristics of jobs and machines to find related propositions for developing a branch and bound algorithm to solve the scheduling problem optimally.
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Kuo, Sheng-Yuan, and 郭昇源. "Optimal Availability for Determining Choice and Repair Policy of System Components." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/73049608041398842271.
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碩士逢甲大學
工業工程學系
90
In this paper, it’s main purpose is that provides designer a research method which based on “Statistics”. By this way, it can help us to make policies reasonably. And, we expect that determiners do not use the “Experience Rules” to make decisions. Therefore, we will put each combination of factor levels by using the skills of Taguchi method and BBD matrix into reliability analysis software. Then, it needs availability/TC as response value, and applying it to run SAS for statistical analysis and optimization. The result can provides us with optimal solution of parameters (e.g. Mean Time Between Failure (MTBF) and Mean Time To Repair (MTTR)) through Monte Carlo Simulation (MCS) and Response Surface Methodology (RSM). Thus, we hope that the availability of system is going to get maximum in the consideration of limited time and cost, and help determiners to make the choice and repair policies.
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MISHRA, SMRITI. "OPTIMAL AVAILABILITY ANALYSIS OF BRAKE DRUM MANUFACTURING SYSTEM BY USING MARKOVIAN APPROACH." Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/14980.
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In this thesis availability analysis is carried out for a Brake Drum manufacturing system using Markovian approach with the purpose to improve its operational availability. The analysis helped in identifying the key factors that affects the system reliability and there exists good scope to improve the system availability by controlling the contributing factors.
Separate models are developed for active and passive redundancy cases. All the feasible states and, failure and repair transitions are identified to develop the system model. Keeping in mind the limitation of the Markov model the failure and repair rates are taken as constant. The set of ordinary differential equations are obtained for the change of probability of being in respective system states with respect to time in each model. This system of rate equations is solved using Runge- Kutta method in MATLAB. The system availability assessment is based in the sum of probabilities of all working states. Sensitivity analysis is also carried out by varying the repair rates of constituent components in the system which helped in identifying the critical factors and assessing their impact on the system availability. These results are helpful to identify the more sensible elements for overall plant availability and suggest some maintenance and operational action to reduce down-time and maintenance costs.
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Kuo, Ching Chang, and 郭清章. "Optimal Redundancies for Reliability and Availability of Series Systems with Mixed Standby Components." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/91460641311441661316.
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碩士國立中興大學
應用數學系
87
In this thesis, we study the reliability and the availability of four different series system configurations with mixed standby (include warm standby and cold standby) components. The failure times of the primary and warm standby components are assumed to be exponentially distributed with parameters λandα,respectively. The repair times of each server is also exponentially distributed with parameter μ. We derive the mean time-to-failure, and the steady state availability, for four configurations. In this project, we compare their mean time-to-failure, and the steady state availability, and perform comparisons. For all four configurations, comparisons are made for specific values of distribution parameters and of the cost of the components. Finally the configurations are ranked based on:mean time-to-failure, the steady state availability, and cost-benefit where benefit is either mean time-to-failure or the steady state availability. Keywords: availability, cost-benefit, reliability, series system, mean time-to-failure.
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劉怡均. "Optimal Redundancies for Availability of Series Systems with Warm Standby Components and General Repair Times." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/03336278614742048808.
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碩士國立中興大學
應用數學系
92
Abstract In this thesis, we study the availability analysis of three different series system configurations with warm standby components and general repair times. The time-to-failure for each of the primary and warm standby components is assumed to be exponentially distributed with respective parameter λ and α. This thesis presents a recursive method, using the supplementary variable technique and treating the supplementary variable as the remaining repair time, to develop the steady-state probability distribution of the number of working components in the system. We develop the explicit expressions for the steady-state availability, for three configurations and perform comparisons. For all three configurations, comparisons are made for specific values of distribution parameters and of the cost of the components. The configurations are ranked based on availability and cost∕benefit ratio, for three various repair time distributions: exponential, 3-stage Erlang, and deterministic, where benefit is availability. Keywords：availability, cost-benefit, series system, general distribution, recursive method, supplementary variable technique.
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謝錦秀. "Optimal Redundancies for Reliability and Availability of Series Systems with Cold Standby Components and a Repairable Service Station." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/62960734754948299934.
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碩士國立中興大學
應用數學系
92
This thesis studies the cost/benefit analysis of series systems with cold standby components and a repairable service station. Service times and failure times of the primary components are assumed to be exponentially distributed. Breakdown times and repair times of the service station are also assumed to be exponentially distributed. We develop the explicit expressions for the mean time to failure (or MTTF) and the steady-state availability (or ) for three configurations and perform comparisons. Under thecost/benefit (C/B) criterion, comparisons are made for specific values of distribution parameters and of the costs of the components. For all three configurations, the configurations are ranked based on : MTTF, , and C/B where B is either MTTF or .
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Lai, Min-Hsiu, and 賴民修. "A Study on Optimal Strategy in Hybrid Remanufacturing System under Limitations of Component Availability, Capacity Constraint and Product Substitutatility." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/51303378134340543003.
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碩士國立成功大學
工業與資訊管理學系碩博士班
96
Owing to the scarceness of natural resources and the increase of the world protection the problem of energy shortage has become a serious issue which has to be deal with nowadays and as a result, the focus of environmental protection has been essentially critical. Therefore, more and more manufacturers and companies are involved in the recycle of used products. This can explained by the following two main reasons: First of all, products with regeneration process are attractive to consumers who possess the concept of environmental protection. Secondly, on account of the restriction of law, manufactures have to effectively recycle and reuse the abandoned old or broken products in order to be beneficial to the environment. Typical production systems have only new products in production line. When manufacturers collect used-products and perform the process of remanufacturing, they use production lines: for producing the new products and the remanufacturing products, respectively, and which are called “Hybrid system with remanufacturing.” It is desirable to establish a suitable strategy for such a remanufacturing system. In this paper, focus it on a hybrid remanufacturing system, we consider related costs with manufacturing and remanufacturing processes to construct a model in determining the optimal strategy of production. In addition, due to the variability of the collection of used-product and competition between the new and the remanufacturing products, we also consider the impacts of capacity constraint, product substitution and limitations of component availability. The model is utilized by the Lingo software to obtain the optimal new product production quantities and the collect rate of the used-product. The expected total profit and remanufacturing quantities can also be derived. Finally, sensitivity analyses are conducted on various parameters to gain insight into the proposed model.
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Kung, Shyang-Jeu, and 孔祥舉. "Using Life Cycle Cost and Availability for Analyzing Optimal Repair Level - A Case Study of the Landing Gear System of a Fighter Plane." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/06834065860245887437.
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碩士國防大學中正理工學院
兵器系統工程研究所
89
In this research, the landing gear system of a single-seat fighter plane is used as a case study in analyzing the level of repair. The life-cycle cost analysis is accomplished for both the linear replacement units (LRU) and shop replaceable units (SRU) to identify the optimal level of repair through the evaluation of system cost effectiveness and operational availability requirements. The results of this evaluation are then compared with the existing maintenance policy to derive the recommendations for corrective action and/or design improvement. Based on the technical documents of the landing gear system, this research utilizes the Equipment Designer’s Cost Analysis System (EDCAS® v3.0) and the Air Forces Logistics Information Management System (LIMS) to establish and construct the hardware structures of the landing gear system, as well as to collect the related logistics data. After analyzing and comparing with the current situation, we derive the suggestion for the optimal repair level in which there are 31 SRUs being different from the existing maintenance policy. Through analyzing hardware characteristics, we arrange the 31 SRUs into five categories. In each category we choose one item to further analyze and compare.
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Shifali, Shifali. "Optimal Mammography Schedule Estimates Under Varying Disease Burden, Infrastructure Availability, and Other Cause Mortality: A Comparative Analyses of Six Low- and Middle- Income Countries." 2020. https://scholarworks.umass.edu/masters_theses_2/992.
Full textAbstract:
Low-and-middle-income countries (LMICs) have a higher mortality-to-incidence ratio for breast cancer compared to high-income countries (HICs) because of late-stage diagnosis. Mammography screening is recommended for early diagnosis, however, current screening guidelines are only generalized by economic disparities, and are based on extrapolation of data from randomized controlled trials in HICs, which have different disease burdens and all-cause mortality compared to LMICs. Moreover, the infrastructure capacity in LMICs is far below that needed for adopting current screening guidelines. This study analyzes the impact of disease burden, infrastructure availability, and other cause mortality on optimal mammography screening schedules for LMICs. Further, these key features are analyzed under the context of overdiagnosis, epidemiologic/clinical uncertainty in pathways of the initial stage of cancer, and variability in technological availability for diagnosis and treatment. It uses a Markov decision process (MDP) model to estimate optimal schedules under varying assumptions of resource availability, applying it to six LMICs. Results suggest that screening schedules should change with disease burden and life-expectancy. For countries with similar life-expectancy but different disease burden, the model suggests to screen age groups with higher incidence rates. For countries with similar incidence rate and different life expectancy, the model suggests to screen younger age groups for countries with lower life-expectancy. Overdiagnosis and differences in screening technology had minimal impact on optimal schedules. Optimality of screening schedules were sensitive to epidemiologic/clinical uncertainty. Results from this study suggest that, instead of generalized screening schedules, those tailored to disease burden and infrastructure capacity could help optimize resources. Results from this study can help inform current screening guidelines and future health investment plans.
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Gabler, Christopher. "Restoration ecology of ecosystems invaded by Triadica sebifera (Chinese tallow tree): theory and practice." Thesis, 2012. http://hdl.handle.net/1911/71650.
Full textAbstract:
Invasive exotic species threaten biodiversity and ecosystem functions globally, creating need for and encumbering ecological restoration. When restoring exotic plant-dominated ecosystems, reinvasion pressure is the rate of new exotic recruitment following mature exotic removal. It can vary broadly among similarly invaded habitats and is crucial to restoration outcomes and costs, but is difficult to predict and poorly understood.
Initial results from the experimental restoration of a wetland dominated by Triadica sebifera led us to develop the ‘outgrow the stress’ hypothesis. It holds: (1) Variation in reinvasion pressure is driven by differences in propagule abundance and spatiotemporal availability of realized recruitment windows, which are defined by abiotic conditions and biotic interactions. (2) Differences in reinvasion pressure become masked by exotic dominance when increases in niche breadth during development enable exotic persistence across sites where recruitment windows range from frequent to episodic.
We validated this hypothesis. First, we used greenhouse and field experiments to quantify Triadica’s moisture niche early in development. By two months post-germination, seedling tolerances broadened to include conditions unsuitable for germination. This clearly demonstrated a rapid ontogenetic niche expansion, which could decouple mature Triadica density and average reinvasion pressure.
Second, we used a greenhouse mesocosm experiment to quantify how recruitment window duration, competition and fertility impacted population-level Triadica establishment in stressful environments. As ‘outgrow the stress’ predicts, longer windows increased Triadica success and multi-factor interactions were common, with competition and fertility effects varying among environmental contexts.
Third, we substantiated predictions of ‘outgrow the stress’ regarding propagule availability and soil moisture by manipulating these in a multi-site field experiment spanning eleven experimental restorations of Triadica-dominated habitats along a moisture gradient. Triadica reinvasion pressure varied broadly among sites but correlated with moisture and fertility. Propagule availability drove reinvasion in favorable environments, but availability of suitable conditions trumped propagules in extreme environments. Competition reduced Triadica performance and sometimes survival. Triadica prevalence reduced native plant prevalence. Six restorations require minimal Triadica management for success.
This work advances our understanding and enables better predictions of reinvasion pressure and invasions in general. Accurate predictions enhance restoration efficiency by informing site selection and optimal management strategies.
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Nien, Ting-hu, and 粘丁戶. "Availability Estimation and Analysis for ADM Equipment and SDH Optical Fiber Ring Networks." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/46484087688957459294.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
92
Nowadays, communication requirements are changing gradually from traditional voice conversations to multi-media transmission mode with voice conversations, video, and data. In order to provide larger bandwidth and high reliability for customer, synchronous digital hierarchy (SDH) technology is the best choice for high-speed optical fiber backbone transmission network. As a point of view of system network planning and actual operation & maintenance, this article is to approach the reliability estimated for main equipment, an add drop multiplexer (ADM) of SDH network. We would like to compare the influences of the mean time between failure (MTBF) and availability of ADM equipped with/without redundant circuit interface modules and also to analyze that the different results of availability in different combined circuit interface modules and different number of mean time to repair (MTTR) to evaluate availability of maintenance. In addition, the ring topology of SDH network is the most popular for Telecom service provider now and there are two protections switch schemes including multi section shared protection ring (MS-SPRING) and subnetwork connection protection (SNCP). Because different types of fiber cut will affect different kinds of availability of circuits, here, we would like to assume that there are four ADM nodes typically to form a ring topology. Based on the assumption, we investigate how the protection schemes affect the circuit availability, and the result will be reference what are the suitable applications we could use. Finally, we hope these analytic results could be good references for telecom service provider in SDH optical transmission network maintenance improvement
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Vangala, Sarma V. "Applications Of Ldpc Codes For Hybrid Wireless Optical And Magnetic Recording Systems." 2007. https://scholarworks.umass.edu/theses/54.
Full textAbstract:
This thesis comprises of two parts. In the first, we improve the performance of existing hybrid FSO/RF communication systems. Conventional hybrid RF and optical wireless communication systems make use of independent and parallel Free Space Optical (FSO) and RF channels to achieve higher reliability than individual channels. This thesis is based on the idea that true hybridization can be accomplished only when both channels collaboratively compensate the shortcomings of each other and thereby, improve the performance of the system as a whole. We believe that optimization on the combined channel capacities instead of the individual channel capacities of the FSO and RF channels can increase the system availability by a large amount. Using analysis and simulation, we show that, by using Hybrid Channel Codes, we can obtain more than two orders of magnitude improvement in bit error rates and many-fold increase in system availability over the currently existing best systems. Simulations also show that the average throughput obtained using the new system is over 35% better when compared to the present systems. The goodput is much higher because of the elimination of data repetition. Also by avoiding data duplication, we preserve to a great extent the crucial security benefits of FSO communications.
The second half of the thesis deals with magnetic recording systems. Due to the insatiable and ever-increasing needs of data storage, novel techniques have to be developed to improve the capacity of magnetic recording channels. These capacity requirements translate to improving storage densities and using higher recording rates. For these channels, improvements even in the order of a tenths of a dB have a big impact on the storage densities of the recording device. Recently, LDPC codes have been constructed to achieve the independent and uniformly distributed (i.u.d.) capacity of partial response (PR) channels. The “guess algorithm” has been proposed for memoryless channels, to improve the performance of iterative belief propagation decoding to that of Maximum Likelihood (ML) decoding. In the second part of this thesis, the “guess algorithm” is extended to channels with memory. It is shown using asymptotic density evolution analysis that the gains obtained using this algorithm on these channels are more than those obtained over memoryless channels. The “guess algorithm” is further extended to magnetic recording channels which are characterized by ISI and additive white gaussian noise (AWGN). Simulations show that gains of upto one dB are possible on magnetic recording channels.
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Palkopoulou, Eleni. "Homing-Architekturen für Multi-Layer Netze: Netzkosten-Optimierung und Leistungsbewertung." Doctoral thesis, 2011. https://monarch.qucosa.de/id/qucosa%3A18770.
Full textAbstract:
Die schichtenübergreifende Steuerung von Multi-Layer Netzen ermöglicht die Realisierung fortgeschrittener Netzarchitekturen sowie neuartiger Konzepte zur Steigerung der Ausfallsicherheit. Gegenstand dieser Arbeit ist ein neues ressourcensparendes Konzept zur Kompensation von Core-Router-Ausfallen in IP-Netzen. Core-Router-Ausfälle führen zur Abkopplung der an Ihnen angeschlossenen Zugangsrouter vom Netz. Daher werden die Zugangsrouter üblicherweise mit jeweils zwei oder mehreren verschiedenen Core-Routern verbunden (engl.: dual homing) was jedoch eine Verdoppelung der Anschlusskapazität im IP Netz bedingt. Bei dem neuen Verfahren - Dual Homing mit gemeinsam genutzten Router-Ersatzressourcen (engl.: dual homing with shared backup router resources, DH-SBRR) - erfolgt die Zugangsrouter-Anbindung zum einen zu einem Core-Router des IP-Netzes und zum anderen zu einem Netzelement der darunterliegenden Transportschicht. Damit lassen sich Router-Ersatzressourcen, die im IP-Netz an beliebigen Stellen vorgehalten werden können, uber das Transportnetz an die Stelle eines ausgefallenen Core-Routers schalten. Die Steuerung dieser Ersatzschaltung geschieht über eine schichten übergreifende, d.h. das Transportnetz- und IP-Netz umfassende Control-Plane - beispielsweise auf Basis von GMPLS. Da beim Umschalten der Routerressourcen auch aktuelle Zustände (bspw. Routing-Tabellen) auf die Router-Ersatzressourcen mit übertragen werden müssen, beinhaltet das neue Verfahren auch Konzepte zur Router-Virtualisierung.
Zum Vergleich und zur Bewertung der Leistungsfähigkeit des neuen DH-SBRR Verfahrens werden in der Arbeit verschiedene Zugangsrouter-Homing-Varianten hinsichtlich Netz-Kosten, Netz-Verfügbarkeit, Recovery-Zeit und Netz-Energieverbrauch gegenübergestellt. Als Multi-Layer Netzszenarien werden zum einen IP über WDM und zum anderen IP über OTN (ODU) betrachtet.
Zur Bestimmung der minimalen Netz-Kosten ist ein generisches Multi-Layer Netzoptimierungsmodell entwickelt worden, welches bei unterschiedlichen Homing-Architekturen angewendet werden kann. Neben dem Optimierungsmodell zur Netzkostenminimierung wird auch eine Modellvariante zur Minimierung des Energieverbrauchs vorgestellt. Um die Rechenzeit für die Lösung der Optimierungsprobleme zu verringern und damit auch größere Netzszenarien untersuchen zu können bedarf es heuristischer Lösungsverfahren. Im Rahmen der Arbeit ist daher eine neue speziell auf die Multilayer-Optimierungsprobleme zugeschnittene Lösungsheuristik entwickelt worden.
Aus der Netzkosten-Optimierung ergibt sich, dass durch den Einsatz von DH-SBBR signifikante Kosteneinsparungen im Vergleich zu herkömmlichen Homing-Architekturen realisiert werden können. Änderungen der Verkehrslast, der Kosten der IP-Netzelemente oder der Netztopologie haben keinen signifikanten Einfluss auf dieses Ergebnis.
Neben dem Kosten- und Energieeinsparungspotential sind auch die Auswirkungen auf die Netz-Verfügbarkeit und die Recovery-Zeit untersucht worden. Für die Ende-zu-Ende Verfügbarkeit bei Anwendung der verschiedenen Homing-Architekturen Können untere Grenzwerte angegeben werden. Zur Bestimmung der Recovery-Zeit bei Einsatz von DH-SBRR ist ein eigenes analytisches Berechnungsmodell entwickelt und evaluiert worden. Damit kann das DH-SBRR Verfahren zur Einhaltung vorgegebener Recovery-Zeiten (wie sie für bspw. Für bestimmte Dienste gefordert werden) entsprechend parametriert werden.The emergence of multi-layer networking capabilities opens the path for the development of advanced network architectures and resilience concepts. In this dissertation we propose a novel resource-efficient homing scheme: dual homing with shared backup router resources. The proposed scheme realizes shared router-level redundancy, enabled by the emergence of control plane architectures such as generalized multi-protocol label switching. Additionally, virtualization schemes complement the proposed architecture. Different homing architectures are examined and compared under the prism of cost, availability, recovery time and energy efficiency. Multiple network layers are considered in Internet protocol over wavelength division multiplexing as well as Internet protocol over optical data unit settings - leading to the development of multi-layer optimization techniques. A generic multi-layer network design mathematical model, which can be applied to different homing architecture considerations, is developed. The optimization objective can be adapted to either minimizing the cost for network equipment or the power consumption of the network. In order to address potential issues with regard to computational complexity, we develop a novel heuristic approach specifically targeting the proposed architecture. It is shown that significant cost savings can be achieved - even under extreme changes in the traffic demand volume, in the cost for different types of network equipment, as well as in the network topology characteristics. In order to evaluate occurring tradeoffs in terms of performance, we study the effects on availability and recovery time. We proceed to derive lower bounds on end-to-end availability for the different homing architectures. Additionally, an analytical recovery time model is developed and evaluated. We investigate how service-imposed maximum outage requirements have a direct effect on the setting of the proposed architecture.