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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

A Measurement System for Science and Engineering Research Center Performance Evaluation

Gibson, Elizabeth Carole 07 November 2016 (has links)
This research provides performance metrics for cooperative research centers that enhance translational research formed by the partnership of government, industry and academia. Centers are part of complex ecosystems that vary greatly in the type of science conducted, organizational structures and expected outcomes. The ability to realize their objectives depends on transparent measurement systems to assist in decision making in research translation. A generalizable, hierarchical decision model that uses both quantitative and qualitative metrics is developed based upon program goals. Mission-oriented metrics are used to compare the effectiveness of the cooperative research centers through case studies. The US National Science Foundation (NSF) industry university cooperative research center (IUCRC) program is the domain of organizational effectiveness because of its longevity, clear organizational structure, repeated use and availability of data. Not unlike a franchise business model, the program has been replicated numerous times gaining recognition as one of the most successful federally funded collaborative research center (CRC) programs. Understanding IUCRCs is important because they are a key US policy lever for enhancing translational research. While the program model is somewhat unique, the research project begins to close the gap for comparing CRCs by introducing a generalizable model and method into the literature stream. Through a literature review, program objectives, goals, and outputs are linked together to construct a four-level hierarchical decision model (HDM). A structured model development process shows how experts validate the content and construct of the model using these linked concepts. A subjective data collection approach is discussed showing how collection, analysis and quantification of expert pair-wise-comparison data is used to establish weights for each of the decision criteria. Several methods are discussed showing how inconsistency and disagreement are measured and analyzed until acceptable levels are reached. Six case studies are used to compare results, evaluate the impact of expert disagreement and conduct criterion-related validity. Comparative analysis demonstrates the ability of the model to efficiently ascertain criteria that are relatively more important towards each center's performance score. Applying this information, specific performance improvement recommendations for each center are presented. Upon review, experts generally agreed with the results. Criterion-related validity discusses how the performance measurement scoring system can be used for comparative analysis among science and engineering focused research centers. Dendrograms highlight where experts disagree and provide a method for further disagreement analysis. Judgment quantification values for different expert clusters are substituted into the model one-at-a-time (OAT) providing a method to analyze how changes in decisions based on these disagreements impact the results of the model's output. This research project contributes to the field by introducing a generalizable model and measurement system that compares performance of NSF supported science and engineering focused research centers.
122

Auto-Generating Models From Their Semantics and Constraints

Pati, Tanumoy 20 August 2013 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Domain-specific models powered using domain-specific modeling languages are traditionally created manually by modelers. There exist model intelligence techniques, such as constraint solvers and model guidance, which alleviate challenges associated with manually creating models, however parts of the modeling process are still manual. Moreover, state-of-the-art model intelligence techniques are---in essence---reactive (i.e., invoked by the modeler). This thesis therefore provides two contributions to model-driven engineering research using domain-specific modeling language (DSML). First, it discusses how DSML semantic and constraint can enable proactive modeling, which is a form of model intelligence that foresees model transformations, automatically executes these model transformations, and prompts the modeler for assistance when necessary. Secondly, this thesis shows how we integrated proactive modeling into the Generic Modeling environment (GME). Our experience using proactive modeling shows that it can reduce modeling effort by both automatically generating required model elements, and by guiding modelers to select what actions should be executed on the model.
123

The Importance of Construct Definition and Specification in Operations Management Structured Model Research: The Case for Quality and Sustainability Constructs in a Decision-Making Model

Xu, Lu 08 1900 (has links)
In the operations management research, the inconsistent use of the same term for different concepts and the use of the similar concepts for different constructs potentially causes theoretical and statistical problems. This research addresses the importance of construct definitions and specification methodologically within the context of quality and sustainability management. It involves three essays using multiple quantitative methods such as partial least squares structural equation modeling and multiple regression in different consumer decision-making models in the automobile industry. In the first two essays, a comprehensive literature review results in definition and contextualization of the quality and sustainability constructs as applied to operations management and marketing research. The relationships of these constructs with consumer behavior are empirically tested. Building upon the first two essays, the third essay addresses the methodological issues on formative and reflective measurements by summarizing a procedure of validating formative measurements. The quality construct was used to illustrate the methodology. This research contributes to the literature, theory, and practices in the area of quality and sustainability management.
124

Farm planning for a typical crop-livestock integrated farm : an application of a mixed integer linear programming model

Ghebretsadik, Amanuel Habte 12 1900 (has links)
Assignment (MSc) -- University of Stellenbosch, 2004. / ENGLISH ABSTRACT: In an integrated crop-livestock production farm, the profitability and sustainability of farm production is dependent on the crop rotation strategy applied. Crop rotations have historically been applied to maintain long-term profitability and sustainabiliry of farming production by exploiting the jointly beneficial interrelationships existing among different crop types and the animal production activity. Monocrop (specifically wheat) growers in the Swartland area of the Western Cape are struggling to maintain long-term profitability and sustainability of the crop production, challenging them to rethink about the introduction crop rotation in the production planning. By making proper assumptions, this paper develops a mixed integer linear programming model to suggest a decision planning for the farm planning problem faced by an integratedcrop- livestock production farmer. The mathematical model developed includes crop production, dairy production and wool sheep production activities, which permitted the consideration of five crop types within a crop rotation system. By assuming that a farmer uses a cycle of at most three years, the crop rotation model was incorporated in the composite mixed integer linear farm planning model. In order to demonstrate the application of the mathematical farm planning model formulated, a case study is presented. Relevant data from the Koeberg area of the Swartland region of the Western Cape was applied. For each planning period, the model assumed that the farm has the option of selecting from any of 15 cropping strategies. A land which is not allocated to any of the 15 crop rotation strategies due to risky production situation is left as grass land for roughage purposes of the animal production. Results of the mathematical model indicated that farm profit is dependent on the cropping strategy selected. Additionally, animal production level was also dependent on the crop strategy appl ied. Furthermore, study results suggest that the profit generated from the integrated crop-livestock farm production by adopting crop rotation was superior to profit generated 1'1'0111 the farm activities which are based on monocrop wheat strategy. Empirical results also indicated that the complex interrelationship involved in a mixed crop-livestock farm operation play a major role in determining optimal farm plans. This complex interrelationships favour the introduction of crop rotation in the crop production activities of the farm under investigation. Crop production risk is the major risk component of risk the farmer faces in the farm production. In this study, risk is incorporated in the mixed integer programrnmg farm planning model as a deviation from the expected values of an activity of returns. Model solution with risk indicated that crop rotation strategy and animal production level is sensitive to risk levels considered. The Results also showed that the incorporation of risk in the model greatly affects the level of acreage allocation, crop rotation and animal production level of the farm. Finally, to improve the profitability and sustainability of the farm activity, the study results suggest that the introduction of crop rotation which consist cereals, oil crops and leguminous forages is of paramount importance. Furthermore, the inclusion of forage crops such as medics in the integrated crop livestock production is beneficial for sustained profitability from year to year. / AFRIKAANSE OPSOMMING: Wisselbou is baie belangrik om volhoubare winsgewindheid te verseker in 'n geintegreerde lewendehawe I gewasverbouing boerdery in die Swartland gebied van Wes-Kaap. "n Monokultuur van veral koring produksie het ernstige problerne vir produsente veroorsaak. In hierdie studie word 'n gemengde heeltallige liniere prograrnmerings-model gebruik om te help met besluitneming in sulke boerderye.Die wiskundige model beskou die produksie van kontant- en voer-gewasse (5 verskillende soorte) asook suiwel- en wol/vleis-produksie (beeste en skape) .Daar word aanvaar dat die boer "n siklus van hoogstens 3 jaar in die wisselbou rotasie model gebruik .. 'n Gevallestudie word gedoen met behulp van toepaslike data van 'n plaas in die Koeberg gebied. Die model aanvaar dat die produsent 'n keuse het uit 16 wisselbou strategic .Resultate toon dat winsgewindheid afhanklik is van die strategie gekies en dat wisselbou beter resultate lewer as in die geval van "n monokultuur.Dit wys ook dat die wisselwerking tussen diereproduksie en gewasproduksie baie belangrik is in die keuse van 'n optimale strategie. Die risiko in gewasverbouing is die belangrikste risiko factor vir die produsent.In hierdie studie word risiko ook ingesluit in die gemengde heeltallige model, naamlik as 'n afwyking van die verwagte opbrengs-waardes .Die model toon duidelik dat gewasproduksie en lewendehawe-produksie baie sensitief is ten opsigte van die gekose risiko vlak. Die studie toon ook dat 'n wisselbou program wat die produksie van graan (veral koring) .oliesade asook voere insluit belangrik is vir volhoubare winsgewindheid Die insluiting van klawers (bv "medics") is veral belangrik hier.
125

Sources and management of risk in large-scale sugarcane farming in KwaZulu-Natal, South Africa.

Mac Nicol, Richard. January 2007 (has links)
The South African (SA) sugar industry supports approximately 50,940 small and large scale producers who collectively produce 22 million tons of sugarcane seasonally, on average. SA farmers face many challenges that lead to an uncertain decision making environment. Despite a general consensus among agricultural economists that risk constitutes a prevalent feature of the production and marketing environment, various authors have recently stated that risk-related research has failed to provide a convincing argument that risk matters in farmers' decisions. The various shortcomings of previous research have been identified and recommendations for the future proposed. Recommendations include that the focus of future risk research should be on holistic risk management. This study firstly identified the perceived importance of 14 separate sources of risk for a sample of 76 large-scale commercial sugarcane farmers in KwaZulu-Natal. Once a sufficient understanding of the risk perceptions of respondents had been attained, their use of 12 risk-related management strategies was determined. Principal components analysis (PCA) was used to investigate how individual management instruments are grouped together by respondents into choice brackets in order to make use of complementary and substitution effects. The study then proposed and demonstrated a technique that may be used in future research to isolate the effects of risk on individual risk-related management responses by modelling the management strategies contained within individual choice brackets with two-stage least squares regression analysis (2SLS). The most important risk sources were found to be the threats posed by land reform, minimum wage legislation and the variability of the sugar price, in that order. PCA identified seven risk dimensions, collectively explaining 78% of the variance in all 14 risk sources considered. These dimensions were: the "Crop Gross Income Index", "Macroeconomic and Political Index", "Legislation Index", "Labour and Inputs Index", "Human Capital and Credit Access Index", "Management Index" and the "Water Rights Index". Respondents were also asked questions regarding risk-related management strategies, including diversification of on-farm enterprises, investments and management time. PCA identified six management response brackets, collectively explaining 77% of the variance in the 12 responses considered. These response indexes were: the "Mechanisation and Management Bracket", "Enterprise and Time Diversification Bracket", "Insurance and Credit Reserve Bracket", "Geographic and Investment Diversification Bracket", "Land Trade Bracket" and the "Labour Bracket". Lastly, the study proposed a methodology for investigating the role of individuals' risk preferences in decision making. The recommended technique involves the simultaneous modelling of the major risk-related management strategies within each management response bracket, using 2SLS. A measure of risk preference was included in the 2SLS analysis to establish the influence of risk on decision making. By applying this methodology to the data obtained in this study, respondents were shown to be taking advantage of various complementary and substitution effects that exist between management responses. This was evident from the PCA and confirmed for the first previously identified management response bracket using 2SLS regression analysis. Risk attitude was shown to be a significant determinant of management decisions regarding the extent to which back-up management is kept in reserve. Important policy recommendations stemming from this study include that government review restrictive labour legislation and decrease the uncertainty surrounding new land redistribution legislation. Farmers need to make better use of available information by considering the effects of any single management decision on separate decisions, enabling them to take further advantage of substitution and complementary effects that may exist between management strategies previously considered in separate decision brackets. The fact that mechanisation and labour use occur in separate risk-related management response brackets in this study is an example of one such substitution effect that farmers do not seem to be utilising in terms of their management decision making. Future research using time series data is important in order to identify how risk perceptions and management portfolios change over time. Also, further research using the methodology proposed in this study may prove to be a useful means of more adequately addressing the question "Does risk matter in farmers' decisions?" / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.
126

The economic rationale for stochastic urban transport models and travel behaviour : a mathematical programming approach to quantitative analysis with Perth data

Ernst, Wolfgang F. January 2003 (has links)
[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] This thesis reviews, extends and applies to urban traffic analysis the entropy concept of Shannon and Luce's mathematical psychology in a fairly complex and mathematically demanding model of human decision making, if it is solved as a deeply nested structure of logit calculus. Recognising consumers' different preferences and the universal propensity to seek the best choice when going to some desired goal (k), a transparent mathematical program (MP) is developed: the equivalent of a nested multinomial logit model without its inherent computational difficulty. The MP model makes a statistical assessment of individual decisions based on a randomised (measurable) utility within a given choice structure: some path through a diagram (Rk, Dk), designed a priori, of a finite number of sequential choices. The Equivalence Theorem (ET) formalises the process and states a non-linear MP with linear constraints that maximises collective satisfaction: utility plus weighted entropy, where the weight (1/θn) is a behavioural parameter to be calibrated in each case, eg for the Perth CBD. An optimisation subject to feasible routes through the (Rk, Dk) network thus captures the rational behaviour of consumers on their individually different best-choice decision paths towards their respective goals (k). This theory has been applied to urban traffic assignment before: a Stochastic User Equi-librium (SUE). What sets this thesis apart is its focus on MP models that can be solved with standard Operations Research software (eg MINOS), models for which the ET is a conditio sine qua non. A brief list of SUE examples in the literature includes Fisk's logit SUE model in (impractically many) route flows. Dial's STOCH algorithm obviates path enumeration, yet is a logit multi-path assignment procedure, not an MP model; it is nei-ther destination oriented nor an optimisation towards a SUE. A revision of Dial's method is provided, named STOCH[k], that computes primal variables (node and link flows) and Lagrangian duals (the satisfaction difference n→k). Sheffi & Powell presented an unconstrained optimisation problem, but favoured a probit SUE, defying closed formulae and standard OR software. Their model corresponds to the (constrained) dual model here, yet the specifics of our primary MP model and its dual are possible only if one restricts himself to logit SUE models, including the ET, which is logit-specific. A real world application needs decomposition, and the Perth CBD example is iteratively solved by Partial Linearisation, switching from (measured) disutility minimisation to Sheffi & Powell's Method of Successive Averages near the optimum. The methodology is demonstrated on the Perth Central Business District (CBD). To that end, parameter Θ is calibrated on Main Roads' traffic count data over the years 1997/98 and 1998/99. The method is a revision of Liu & Fricker's simultaneous estimation of not only Θ but an appropriate trip matrix also. Our method handles the more difficult variable costs (congestion), incomplete data (missing observations) and observation errors (wrong data). Finally, again based on Main Roads' data (a sub-area trip matrix), a Perth CBD traffic assignment is computed, (a) as a logit SUE and - for comparison - (b) as a DUE (using the PARTAN method of Florian, Guélat and Spiess). The results are only superficially similar. In conclusion, the methodology has the potential to replace current DUE models and to deepen transport policy analysis, taking into account individual behaviour and a money-metric utility that quantifies 'social benefits', for instance in a cost-benefit-analysis.
127

Stratégies de regroupement pour la maintenance des systèmes à composants multiples avec structure complexe / Grouping strategies for the maintenance of multi-component systems with complex structure

Vu, Hai Canh 12 March 2015 (has links)
Au cours des dernières décennies, avec un fort développement de l'économie mondiale et des nouvelles technologies, la structure des systèmes industriels devient de plus en plus complexe. Elle peut être une combinaison des structures élémentaires telles que structures séries, structures parallèles, structures séries-parallèles, etc. Dans la littérature, la plupart des travaux s'intéressent à développer des stratégies de regroupement en considérant des structures séries. Cette hypothèse est parfois très pénalisée et se limite l'application de ces stratégies dans la réalité. C'est pourquoi, l'objectif principal de cette thèse est de développer des stratégies de regroupement (dynamique et stationnaire) pour la maintenance des systèmes multi-composants avec structure complexe. Ces stratégies développées se basent sur des modèles de durée de vie avec la durée de maintenance non-négligeable. De plus, les conditions dynamiques (contextes dynamiques) telles que opportunités de faire la maintenance, changements de la structure, etc. sont étudiées et intégrées dans la planification de maintenance. Les études montrent la nécessité et les difficultés de la prise en compte de la structure complexe dans les décisions de maintenance. Exemples numériques confirment les avantages de nos stratégies de maintenance en comparant avec les autres stratégies existantes dans la littérature / In the recent decades, with a strong development of the global economy and new technologies, the structure of industrial systems is more and more complex. It can be a combination of elementary structures such as series structures, parallel structures, series-parallel structures, etc. In the literature, the most work focused on developing grouping strategies by considering series structures. This assumption is sometimes much penalized and limited the application of these strategies in reality. Therefore, the main objective of this thesis is to develop dynamic and stationary grouping strategies for the maintenance of multi-component systems with complex structure. These strategies have been developed for age-based models with non-negligible maintenance durations. In addition, dynamic conditions (dynamic context) such as maintenance opportunities, changes of the structure, etc., are considered and integrated into the maintenance scheduling.Our studies show the necessity and the difficulties of taking into account of the complex structure in the maintenance decisions. Numerical examples confirm the advantages of our maintenance strategies by comparing with other existing strategies in the literature
128

Maîtrise des systèmes industriels : optimisation de la conception des lignes de production / Mathematical modeling, analysis and optimization of production lines design

Ouazène, Yassine 29 November 2013 (has links)
Lors de la phase de conception d'un système de production, toutes les alternatives fonctionnelles et technologiques doivent être étudiées afin de proposer la ou les meilleures solutions possibles. Ceci se traduit souvent par une conjugaison de plusieurs sous-problèmes tels que: la sélection de pièces d'équipements à partir d'un ensemble de solutions candidates pour chaque opération de fabrication; l'équilibrage et le dimensionnement des postes de travail; le dimensionnement des zones de stockage; le dimensionnement des systèmes de transport et l'aménagement des emplacements.Dans ce contexte, nous nous sommes intéressés à l’évaluation des performances ainsi qu’à l’optimisation de la conception d’un système de production très répandus dans l'industrie manufacturière à gros volume à savoir les lignes de production en série.Nous avons proposé une nouvelle méthode analytique d’évaluation de performances dite « Méthodes par Machines Equivalentes ». Cette méthode présente les avantages d'être plus précise et plus rapide que les approches existantes dans la littérature. Nous avons aussi montré la pertinence de cette méthode pour l’évaluation du taux de production des systèmes en configuration séries-parallèles ainsi que les lignes avec des machines ayant plusieurs modes de défaillance. Nous avons aussi développé un nouvel algorithme de programmation non linéaire afin d’optimiser le dimensionnement des stocks intermédiaires / During the design phase of a production system, all functional and technological alternatives should be explored in order to propose the best possible solutions. This often results in a combination of several sub-problems such as: selection of pieces of equipments from a set of candidate solutions for each manufacturing operation, dimensioning and allocation of buffers and storage areas, balancing workload among the different workstations, the specification of the type and capacity of the material handling system and the layout of equipments which consists of determining which workstations should be adjacent to each other and how they should be connected.In this context, we were interested in performance evaluation and optimization of serial production lines which are very common in high volume production systems.We have proposed a new analytical method, known as « Equivalent Machines Method» to evaluate the production line throughput. This method has the advantages to be more accurate and faster than the existing approaches in the literature.We have also established the relevance of this method for evaluating the production rate of series-parallel systems and other serial lines with machines having multiple failure modes.We have also developed a new algorithm based on nonlinear programming approach to solve the buffer allocation problem
129

Benefit, cost and risk analysis of designing: a third-party e-commerce logistics center.

January 2001 (has links)
Fu Gang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 71-72). / Abstracts in English and Chinese. / ABSTRACT OF THESIS ENTITLED --- p.I / ACKNOWLEDGEMENT --- p.III / TABLE OF CONTENT --- p.IV / LIST OF FIGURES --- p.VII / LIST OF TABLES --- p.VIII / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- A Third-party E-commerce Logistics Center in Need --- p.1 / Chapter 1.2 --- Difficulty in Designing the Logistics Center --- p.2 / Chapter 1.3 --- AHP and ANP --- p.3 / Chapter 1.4 --- Scope of the Study --- p.4 / Chapter 1.5 --- Organization of the Thesis --- p.5 / Chapter CHAPTER 2 --- BACKGROUND AND LITERATURE REVIEW --- p.7 / Chapter 2.1 --- Third-party E-commerce Logistics Center --- p.7 / Chapter 2.2 --- "Government, Investors, and Users" --- p.8 / Chapter 2.3 --- Center Design --- p.11 / Chapter 2.3.1 --- Information and Physical Infrastructure --- p.11 / Chapter 2.3.2 --- Ownership Arrangement --- p.12 / Chapter 2.3.3 --- Design Alternatives --- p.13 / Chapter 2.4 --- Evaluating Design Alternatives --- p.17 / Chapter CHAPTER 3 --- AHP MODEL --- p.19 / Chapter 3.1 --- Introduction of AHP --- p.19 / Chapter 3.2 --- AHP Models for Government --- p.20 / Chapter 3.2.1 --- Benefit to Government --- p.20 / Chapter 3.2.2 --- Cost to Government --- p.23 / Chapter 3.2.3 --- Risk to Government --- p.24 / Chapter 3.3 --- AHP Models for Investors --- p.25 / Chapter 3.3.1 --- Benefit to Investors --- p.25 / Chapter 3.3.2 --- Cost to Investors --- p.28 / Chapter 3.3.3 --- Risk to Investors --- p.29 / Chapter 3.4 --- AHP Models for Users --- p.32 / Chapter 3.4.1 --- Benefit to Users --- p.32 / Chapter 3.4.2 --- Cost to Users --- p.34 / Chapter 3.4.3 --- Risk to Users --- p.36 / Chapter CHAPTER 4 --- RISK SHARING IN CENTER DESIGN ´ؤ USING AHP MODEL --- p.38 / Chapter 4.1 --- "Solution Methodology of Aggregating Benefit, Cost and Risk in AHP" --- p.38 / Chapter 4.2 --- Aspects in Determining an Agreeable Solution --- p.40 / Chapter 4.3 --- Sensitivity Analysis in AHP --- p.42 / Chapter 4.4 --- A Conflict-Resolving Solution Procedure for AHP --- p.44 / Chapter 4.5 --- An Illustrative Numerical Example in AHP --- p.48 / Chapter CHAPTER 5 --- ANP MODEL --- p.51 / Chapter 5.1 --- Introduction of ANP --- p.51 / Chapter 5.2 --- ANP Models for Government --- p.53 / Chapter 5.2.1. --- Benefit to Government --- p.55 / Chapter 5.2.2. --- Cost to Government --- p.54 / Chapter 5.2.3. --- Risk to Government --- p.54 / Chapter 5.3 --- ANP Models for Investors --- p.56 / Chapter 5.3.1 --- Benefit to Investors --- p.56 / Chapter 5.3.2 --- Cost to Investors --- p.56 / Chapter 5.3.3 --- Risk to Investors --- p.56 / Chapter 5.4 --- ANP Models for Users --- p.56 / Chapter 5.4.1 --- Benefit to Users --- p.56 / Chapter 5.4.2 --- Cost to Users --- p.58 / Chapter 5.4.3 --- Risk to Users --- p.58 / Chapter CHAPTER 6 --- RISK SHARING IN CENTER DESIGN ´ؤ USING ANP MODEL --- p.60 / Chapter 6.1 --- Aggregated Benefit-Cost-Risk ANP Model --- p.60 / Chapter 6.2 --- Sensitivity Analysis of ANP Model in an AHP Fashion --- p.61 / Chapter 6.3 --- Sensitivity Analysis of General ANP Model --- p.62 / Chapter 6.4 --- A Conflict-Resolving Solution Procedure for ANP --- p.63 / Chapter 6.5 --- An Illustrative Numerical Example in ANP --- p.66 / Chapter CHAPTER 7 --- p.69 / CONCLUSION --- p.69 / BIBLIOGRAPHY --- p.71
130

Développement de stratégies de maintenance prévisionnelle de systèmes multi-composants avec structure complexe / Predictive maintenance strategies for multi-component systems with complex structure

Nguyen, Kim Anh 16 October 2015 (has links)
Aujourd'hui, les systèmes industriels deviennent de plus en plus complexes. Cette complexité est due d’une part à la structure du système qui ne se résume pas à des structures classiques en fiabilité, d’autre part à la prise en compte de composants présentant des phénomènes de dégradation graduelle que des systèmes de monitoring permettent de surveiller. Ceci mène à l'objectif de cette thèse portant sur le développement des stratégies de maintenance prévisionnelle pour des systèmes multi-composants complexes. Les politiques envisagées proposent notamment des stratégies de regroupement de composants permettant de tirer des dépendances économiques identifiées. Des facteurs d'importance permettant de prendre en compte la structure du système et la dépendance économique sont développés et combinés avec les évaluations de fiabilité prévisionnelle des composants pour l’élaboration de règles de décision de regroupement. De plus, un couplage des règles de décision de maintenance et de gestion des stocks est également étudié. L’ensemble des études menées montrent l’intérêt de la prise en compte de la fiabilité prévisionnelle des composants, des dépendances économiques et de la structure complexe du système dans l'aide à la décision de maintenance et de gestion des stocks. L’avantage des stratégies développées est vérifié en les comparant à d’autres existantes dans la littérature / Today, industrial systems become more and more complex. The complexity is due partly to the structure of the system that cannot be reduced to classic structure reliability (series structures, parallel structures, series-parallel structures, etc), secondly the consideration of components with gradual degradation phenomena that can be monitored. This leads to the main purpose of this thesis on the development of predictive maintenance strategies for complex multi-component systems. The proposed policies provide maintenance grouping strategies to take advantage of the economic dependence between components. The predictive reliability of components and importance measures allowing taking into account the structure of the system and economic dependence are developed to construct the grouping decision rules. Moreover, a joint decision rule for maintenance and spare parts provisioning is also studied.All the conducted studies show the interest in the consideration of the predictive reliability of components, economic dependencies as well as complex structure of the system in maintenance decisions and spare parts provisioning. The advantage of the developed strategies is confirmed by comparing with the other existing strategies in the literature

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