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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.
11

Reliability analysis considering product performance degradation

Huang, Wei January 2002 (has links)
This dissertation presents a statistical model and analysis procedure for product performance aging degradation data. This model takes into account the strictly increasing/decreasing nature of performance measurements at multiple observation times. Maximum likelihood estimation (MLE) is used to estimate the time varying parameters of the proposed statistical model. The analysis of both generated data and field data is presented. To demonstrate product reliability under aging, an analysis of surface mounted solder joints due to thermal fatigue is included in the dissertation. This analysis was done by first examining published life test data and then identifying the intermetallic compound (IMC) thickness randomness. Results indicate that the IMC layer thickness randomness may have significant influence on the Mean Time To Failure (MTTF) and the reliability at high thermal cycles. The analysis of products with competing hard and soft failure modes is presented in terms of distribution independence. Derivation and examples are included for the event when the product finally fails in a specific failure mode. Finally, an improved strength-stress interference (SSI) reliability model is derived for analyzing a more general engineering degradation problem. This model incorporates both stochastic strength aging degradation and the stochastic loading force directed at the product. Statistical inference for simple stochastic processes and numerical examples are analyzed and discussed to verify the model.
12

Maximizing customer satisfaction by optimal specification of engineering characteristics

Dawson, Donald Wight, 1956- January 1997 (has links)
The House of Quality (HOQ) has been widely discussed as a mechanism for capturing the Voice of the Customer and guiding the process of converting the customer's voice into internal engineering specifications. However, the discussion of this process to date has tended to be qualitative rather than quantitative. Various heuristic practices have evolved with little substantiation of their value or evaluation of their impact other than illustration in a few case studies. Examples of practices promoted by several authors and practitioners include the inclusion of the relative magnitude of effects, but not direction, in the body of the matrix; the restriction of relationships to an integer scale of subjective, ratio values; and allocating available engineering resources to the hard-to-improve characteristics (because the easy ones will presumably take care of themselves). The process for setting target specifications given the HOQ data has not been well defined either. Design teams are required to develop their own ad hoc rules. When multiple engineering characteristics affect a single customer attribute or when an engineering characteristic impacts multiple customer attributes, the design problem becomes difficult and current procedures are of little use to the design team. This is particularly true when some interactions are negative. The result may be lost opportunity from the selection of non-optimal designs. This research takes a scientific approach to optimally specifying the target values for engineering characteristics in a competitive marketplace. A methodology for building linear or nonlinear statistical models of customer preference (value) for each customer attribute followed by an optimization routine that will obtain the optimal specification of engineering characteristics is proposed. The optimization model considers economic and technological constraints as well as customer preferences. The process results in optimal, feasible design specifications. In addition the effect of variability in parameter estimates on the ability to correctly identify the key engineering characteristics for optimizing customer value is investigated. Model performance is also analyzed through random generation of 320 problem instances of varying linearity, size, density, monotonicity and correlation. Finally, the methodology is applied to a problem from industry and the results are compared with an actual, subjectively-derived design.
13

Conditional covering problem: Study of complexity and optimization methods

Horne, Jennifer Amy January 2004 (has links)
The Conditional Covering Problem (CCP) is a facility location problem on a graph, where the set of nodes represents the demand points and the potential facility locations. The CCP minimizes the sum of the facility location costs required to cover all demand points. The key aspect of the CCP is that a facility covers all nodes within a given coverage radius, except for the node on which it is located. Our investigation of the CCP will first show that solving CCP on a general graph structure is NP-Hard, prohibiting finding exact optimal solutions in a finite amount of time. While the CCP is NP-Hard on general graphs, we will present a quadratic algorithm that will find optimal solutions to CCP on path and extended star graphs (multiple path graphs with one node in common). We will then present a polynomial time algorithm for tree graphs building off the quadratic algorithms for a star and tree. Given that CCP is NP-Hard on general graphs we next focused on determining near optimal solutions for general graphs. We applied both greedy heuristics and metaheuristics to determine near-optimal solutions. Building off our understanding of optimal solutions on tree structures, we incorporate the idea of trees into our heuristic search. We found that greedy heuristics provide near-optimal solutions in a very short period of time. We showed that simulated annealing with binary encoding provided higher quality solutions to the CCP.
14

Scheduling flexible flow lines with sequence dependent setup times

Kurz, Mary Elizabeth January 2001 (has links)
This dissertation examines scheduling in flexible flow lines with sequence-dependent setup times to minimize makespan. This type of manufacturing environment is found in industries such as printed circuit board and automobile manufacture. Lower makespans can be associated with more efficient use of resources. Poor scheduling when sequence-dependent setup times exist can negatively impact productivity. As a building block, minimizing makespan in parallel identical machines with sequence-dependent setup times is examined. Several heuristics are compared empirically using statistical analysis. Experimental results indicate that a heuristic based on the Insertion Heuristic for the Travelling Salesman Problem is effective. Subsequently, minimizing makespan in flexible flow lines with sequence-dependent setup times is considered. An integer program that incorporates all aspects of the problem is formulated. Due to the NP-hard nature of the problem, heuristic methods are considered. The heuristics, based on greedy methods, flow line methods, the Insertion Heuristic for the Travelling Salesman Problem and genetic algorithms are compared empirically using statistical analysis. The heuristics are designed to take advantage of the flow line nature of the problem, the parallel machine nature and the combinatorial features of the problem. Problem data is generated in order to evaluate the heuristics. The characteristics are chosen to reflect those used by previous researchers. An effective lower bound is created in order to evaluate the heuristics. A random keys genetic algorithm is found to be very effective for the problems eyed. In addition, several extensions based on backwards pass of the schedule and focusing on the bottleneck stage are proposed and examined. These proved to be ineffective approaches but yielded insight regarding what features of schedule are important. Most significantly, the first stage is very important in determining the quality of the subsequent schedule. The heuristics considered here focus on setting a schedule for one stage and then considering the next. Areas for future research include developing methods of scheduling job-by-job and examination of branch and bound methods to find optimal solutions, aided by effective lower bounds and theorems regarding schedule domination.
15

Coordination mechanisms for new product introduction

Liang, Wei Hao January 2010 (has links)
Coordination mechanisms are described as any administrative tools for facilitating synchronization and integration among functions within an enterprise. Coordination mechanisms play a significant role in the resolution of the constraints caused by task interdependence. They can be used as a vehicle for supporting new product introduction, where a variety of interdependencies exists, thereby remaining a fundamental concern in a number of industries. The objective of this thesis is to discuss coordination mechanism best practices. The outcomes of the thesis include a classification of coordination mechanisms, a discussion of coordination mechanism best practices, the definition of a fitness parameter between characteristics of new product introduction and coordination mechanisms, and recommendations of coordination mechanisms for use by the aerospace industry for new product introduction. / Key Words: Coordination, Coordination Mechanisms, New Product Introduction / Les mécanismes de coordination sont décrits comme des outils administratifs pour faciliter la synchronisation et l'intégration pour les fonctions au sein d'une entreprise. Les mécanismes de coordination jouent un rôle important dans la résolution des contraintes causées par l'interdépendance des tâches. Ils peuvent être utilisés comme un moyen pour soutenir l'introduction de nouveaux produits, où une variété d'interdépendances existe, ainsi une préoccupation essentielle reste dans un certain nombre d'industries. L'objectif de cette thèse est de discuter de meilleures pratiques de mécanisme de coordination. Les résultats de cette thèse comportent une classification des mécanismes de coordination, une discussion sur les meilleures pratiques de mécanisme de coordination, la définition d'un paramètre correct entre les caractéristiques de l'introduction de nouveaux produits et les mécanismes de coordination, et les recommandations des mécanismes de coordination pour l'utilisation dans l'industrie aérospatiale pour l'introduction de nouveau produit. / Mots Clés: Coordination, Les Mécanismes de Coordination, Introduction de Nouveau Produit
16

Value estimation for software development processes

Wang, Zhihua, 1970- January 2004 (has links)
The management of software development processes is a continual challenge facing software development organizations. Previous studies used "flexible models" and empirical methods to optimize software development processes. In this thesis, the expected payoff is used to quantitatively evaluate processes. Payoff can be defined as the value of a team member's action, and the expected payoff combines the value of the payoff of a team member's action and the probability of taking that action. The mathematic models of a waterfall process and two flexible processes are evaluated in terms of total maximum expected payoff. The results show under which conditions which process is more valuable. An overview of this work and results will be presented in this seminar.
17

Value optimization for engineering tasks

Zhang, Xiao Qi January 2012 (has links)
Great competition drives the widespread application of lean value in many industries. Value identification and product delivery is challenging due to the various concerns of shareholders, the large number of disparate tasks, and the complex resource allocation process. The overall goal of this research, then, is to develop a value focused optimization process adopting an enterprise perspective by investigating value identification, decision support and resource allocation. Firstly, a multiple-attribute model is proposed to identify value covering all the important aspects of the decision objectives. Then, the large number of decision makers drives the development of a decision support method to determine value in an efficient and egalitarian way. Finally, the defined value is incorporated into a resource allocation procedure to optimize the value that is realized from limited resources. The research was validated through testing at an aerospace company. / La concurrence importante entraîne la mise en place des valeurs 'Lean' dans de nombreuses industries. L'identification de la valeur et la livraison du produit sont difficiles à cause des diverses soucis des parties prenantes, le nombre important des tâches distribuées et le processus complexe d'allocation des ressources. L'objectif global de cette recherche est de développer un processus d'optimisation basé sur le concept de valeur. Cela se fait en adoptant une perspective d'entreprise qui s'investit sur l'identification de valeur, l'aide à la décision et l'allocation des ressources.Tout d'abord, un modèle multi-attribut est proposé afin de définir la valeur comme étant un concept qui couvre tous les aspects importants des objectifs de décision. Puis, une méthode d'aide à la décision est développée à l'aide d'un grand nombre de décideurs pour déterminer la valeur d'une manière efficace et égalitaire. Enfin, la valeur définie est incorporée dans une procédure d'allocation des ressources, pour optimiser la valeur telle que réalisée à partir des ressources limitées. La recherche a été validée à travers une implémentation dans une entreprise aérospatiale.
18

Manufacturing execution systems integration and intelligence

Hadjimichael, Basil January 2005 (has links)
In order to survive in today's competitive manufacturing markets, manufacturing systems need to adapt at an ever-increasing pace to incorporate new technology which can lower the cost of production, while maintaining quality and delivery schedules. The task of the manufacturing system becomes even more challenging in the quest to use a common approach for different manufacturing plants and ever evolving manufacturing processes for specific plants. This thesis introduces a reference architecture that enables such changes between plants and updates within plants. For this, we use the paradigm of Manufacturing Execution Systems (MES). A developed MES architecture by the National Institute of Standards and Technology (NIST) is used as the standard reference architecture. Its flexibility and scalability is applied to a specific steel melt-shop plant case study. In this case study the standard framework is specified through re-labeling standard data and modules to specifics tailored for the melt process of a generic steel plant. Since steel plants are faced with difficult scheduling and disturbance handling problems, specific intelligent algorithms are developed to deal with these issues through integrating some of the control into the MES. Conclusions as to the success of the algorithms along with supporting data and recommendations of further use for them are also included.
19

Quantitative assessment of product value and change risk analysis in early design process

Oduncuoglu, Arman January 2011 (has links)
Many products that we see in our daily life are designed through modifications to existing products. The ever changing trends in current markets, along with customers' rising demands for quality, require many companies to make frequent changes to create new products. Due to the challenges in product modification, many companies have adopted a strategy of adaptive design to create new designs by incrementally improving the existing ones. This thesis develops a decision support system which helps product development managers to assess project performance metrics, such as development effort, development time, product cost and revenue, customer satisfaction, profit margin, and risk. The proposed model is a specialized calculator which integrates house of quality (HOQ), functional analysis system technique (FAST), risk assessment, product complexity analysis, and change propagation analysis to provide an overview of the design process from product attributes and design risk to cost and effort.The assessment of different design solutions is performed by comparing the obtained performance metrics with those from the original design. The system allows the recalculation of these performance metrics when engineering change occurs during the creation of new design solutions. The system then provides an estimate of the change in required resources and expected benefits through comparative analysis. Through these means, the proposed tool aims to help project managers identify an optimal design solution.The main goal of the proposed model is to increase product knowledge in the early stages of design to support project managers and design engineers in their decision making process. This is achieved through the visualization of the effects of engineering changes. In this thesis, the details of the proposed decision support system (DSS) are described and illustrated with a simple example of a thermoflask. / De nombreux produits d'usage courant ont été conçus en modifiant des produits déjà existants. L'évolution constante des tendances du marché actuel et la demande croissante des clients pour des produits de qualité forcent les entreprises à effectuer des modifications fréquentes en vue de créer de nouveaux produits. Les défis associés à la modification de produit ont incité beaucoup d'entreprises à développer une stratégie de conception adaptative permettant de créer de nouveaux produits en améliorant de manière incrémentielle les produits existants. Ce mémoire propose un système d'aide à la décision visant à appuyer les gestionnaires en développement de produits dans l'analyse des mesures de performance d'un projet tels que l'effort et le temps de développement, le coût et le potentiel de revenu, la satisfaction de la clientèle, la marge de profit et le risque. Le modèle proposé est un calculateur spécialisé intégrant la maison de la qualité (HOQ), la technique d'analyse fonctionnelle de système (diagramme FAST), l'analyse du risque, l'analyse de la complexité du produit et l'analyse de la propagation de la modification. Il est ainsi possible de fournir une vue d'ensemble du processus de conception du produit allant des attributs du produit et du risque de la conception jusqu'aux coûts et aux efforts requis.L'analyse des diverses solutions de conception est effectuée en comparant les mesures de performance obtenues avec celles qui sont associées à la conception initiale. Le système permet de recalculer les mesures de performance lorsque des modifications techniques sont apportées dans le cadre de la création de nouvelles solutions de conception. Le système fournit alors, par le biais d'une analyse comparative, une estimation de l'impact de la modification sur les ressources requises et les avantages escomptés. À l'aide de ces fonctionnalités, l'outil proposé vise à aider les chefs de projet à trouver la solution de conception optimale.Le principal objectif du modèle proposé est d'augmenter la connaissance du produit dès les étapes préliminaires de la conception afin d'appuyer le processus de prise de décision des chefs de projet et des ingénieurs de conception. Cet objectif est réalisé par la visualisation des impacts d'une modification technique. Dans ce mémoire, le système d'aide à la décision (SAD) proposé est décrit de manière détaillée et illustré par un exemple simple, celui d'un contenant isotherme.
20

Continuous approval methods for engineered-to-order projects

Bhuiyan, Farina. January 1996 (has links)
This thesis studies project management issues which are applicable to organizations which partake in complex engineered-to-order projects. Traditional approaches to management methods for planning and control of projects are examined, and potential problem areas are identified. An alternative approach, continuous approval methods, is developed. The potential for improved productivity is demonstrated. / The acquisition of defence systems in the Department of National Defence (DND) is used to provide examples of complex engineered-to-order projects. The DND study showed how continuous approval methods improved DND's existing engineered-to-order processes with a reduction in both delivery time and cost. Although the study focused on one organization, the results are applicable to the management of any engineered-to-order project which undergoes traditional report-review-approve cycles.

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