Project/Report (M.S.)--Virginia Polytechnic Institute and State University. M.S. 1992. / Vita. Includes bibliographical references (leaf 21). Also available via the Internet.

Project report (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 97-98). Also available via the Internet.

Project report (M. Eng.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaf 114). Also available via the Internet.

Approved for public release; distribution is unlimited / The purpose of this thesis is to analyze the relationship between predicted system reliability and planned spare parts levels. This will be accomplished through the integration of factors impacting spare parts levels and Life Cycle Costs into a spreadsheet model that will establish the appropriate relationship between the factors. This thesis will then attempt to determine the impact that varying estimations of reliability will have on both Life Cycle Costs nd spares levels for the H-1 Upgrades Program. / Major, United States Marine Corps

Thesis (M.S. in Management)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Don Eaton. Includes bibliographical references (p. 97-98). Also available online.

First, we consider a fundamental pricing model for a single type of reusable resource in which a fixed number of units are used to serve stochastically arriving customers. Customers choose to purchase the resource based on their willingness-to-pay and the current price. If purchased, occupy one unit of the reusable resources for a random amount of time. The firm seeks to maximize a weighted combination of profit, market share, and service level. We establish a series of theoretical results that characterize the strong universal performance of static pricing in such an environment. Second, we describe a comprehensive approach to pricing analytics for reusable resources in the context of rotable spare parts with an industrial partner. We discuss the process of instilling a new pricing culture and developing a scalable new pricing methodology at a major aircraft manufacturer. We develop a novel pricing analytics approach for all rotable spare parts. The new approach tackles the challenges of limited data availability, minimal demand information, and complex inventory dynamics. We also present a successful large-scale implementation of our approach which led to significant profit gains. Third, we extend the pricing model for reusable resources to the setting of multiple customer classes. We describe two types of heuristics for this class of problem with accompanying numerical experiments. In addition, we provide a universal performance guarantee for a special case. We also discuss the role of substitution effects between different classes of customers.

Cette thèse porte sur la restauration de champs d'ondes sismiques perturbés par trois sources de dégradation. Ces sources sont dues à des trajets de propagation complexes, au dispositif d'acquisition, à des sources liées ou non à l'acquisition, et potentiellement présentes simultanément : des réflexions multiples (ou échos), une dégradation de la réponse impulsionnelle attendue (ou flou) et des perturbations plus aléatoires (ou bruits).Nous avons considéré dans un premier temps le problème des réflexions multiples, réflexions qui se sont réfléchies plusieurs fois sur au moins une interface. Nous nous intéressons ici au filtrage adaptatif de ces réflexions sismiques multiples à partir de modèles approximatifs issus de modélisation sismique. Ce filtrage est réalisé dans un domaine de trames d'ondelettes discrètes, mono- et bidimensionnelles, sous contraintes de parcimonie et de variation lente des filtres adaptatifs. Ceci est intéressant en réflexion sismique, car les méthodes standard peuvent produire des filtres très mal conditionnés, du fait notamment du caractère passe-bande des données sismiques. Dans ce travail, une formulation variationnelle des problèmes de réflexions multiples est proposée. Nous utilisons des algorithmes proximaux, dont la convergence est garantie lorsqu'il s'agit d'optimiser dans un cadre convexe. L'avantage de ces approches est l'utilisation d'une régularisation sophistiquée, permettant de considérer la parcimonie à la fois a) dans le domaine d'ondelettes, b) via des a priori sur les filtres pour lesquels nous avons utilisé différentes fonctions de régularisation (norme l1, l2, mixte l1-2 et nucléaire). Notre méthode vise à étendre et améliorer certains aspects de la méthode proposée par S. Ventosa en collaboration avec CGG en 2012, et testée avec succès sur plusieurs campagnes sismiques. Les résultats que nous avons obtenus démontrent la performance de notre méthode non seulement sur des données synthétiques bruitées mais également sur des données réelles. Nous nous intéressons ensuite au problème de déconvolution aveugle. En géophysique, un modèle simplifié de la Terre souvent utilisé fait l'hypothèse d'un nombre de couches localement parallèles, chacune avec des propriétés constantes. Mais la vitesse, la densité ou les deux peuvent varier d'une couche à l'autre. L'impédance acoustique est calculée pour chaque couche ; puis les coefficients de réflexion pour une incidence normale sont calculés aux endroits où il y a des changements d'impédance acoustique. Chaque changement d'impédance acoustique opère une modification d'amplitude et de polarisation liée aux coefficients de réflexion. Ainsi, la séquence de réflectivité (réponse impulsionnelle) est convoluée avec la forme d'onde descendante pour donner une trace sismique. Ce problème constitue un contexte de déconvolution aveugle où l'on recherche un signal inconnu, convolué avec une forme d'onde elle aussi inconnue en présence de bruit additif. La déconvolution requiert souvent d'introduire des hypothèses complémentaires sous forme de pénalisation, notamment non convexe. L'ambiguïté d'échelle en déconvolution aveugle suggère l'usage de fonctions de contraste invariantes en échelle. Dans cette thèse, nous proposons un algorithme de minimisation alternée, de type explicite-implicite à métrique variable. Il traite une approximation lisse du rapport l1/l2 (SOOT pour "Smoothed One-Over-Two penalty") pour des données réelles signées. Nous étudions les propriétés de convergence de la méthode proposée, basées sur l'inégalité de Kurdyka-Lojasiewicz. Les performances de cette nouvelle approche sont illustrées à travers un exemple en déconvolution aveugle de données sismiques, mais aussi sur des images / This thesis deals with two different problems within the framework of convex and non convex optimization. The first one is an application to multiple removal in seismic data with adaptive filters and the second one is an application to blind deconvolution problem that produces characteristics closest to the Earth layers. More precisely : unveiling meaningful geophysical information from seismic data requires to deal with both random and structured “noises”. As their amplitude may be greater than signals of interest (primaries), additional prior information is especially important in performing efficient signal separation. We address here the problem of multiple reflections, caused by wave-field bouncing between layers. Since only approximate models of these phenomena are available, we propose a flexible framework for time-varying adaptive filtering of seismic signals, using sparse representations, based on inaccurate templates. We recast the joint estimation of adaptive filters and primaries in a new convex variational formulation. This approach allows us to incorporate plausible knowledge about noise statistics, datas parsity and slow filter variation in parsimony-promoting wavelet transforms. The designed primal-dual algorithm solves a constrained minimization problem that alleviates standard regularization issues in finding hyper parameters. The approach demonstrates significantly good performance in low signal-to-noise ratio conditions, both for simulatedand real field seismic data. In seismic exploration, a seismic signal (e.g. primary signal) is often represented as the results of a convolution between the “seismic wavelet” and the reflectivity series. The second goal of this thesis is to deconvolve them from the seismic signal which is presented in Chapter 6. The main idea of this work is to use an additional premise that the reflections occur as sparsely restricted, for which a study on the “sparsity measure”is considered. Some well known methods that fall in this category are proposed such as[Sacchi et al., 1994; Sacchi, 1997]. We propose a new penalty based on a smooth approximation of the l1/l2 function that makes a difficult non convex minimization problem. We develop a proximal-based algorithm to solve variational problems involving this function and we derive theoretical convergence results. We demonstrate the effectiveness of our method through a comparison with a recent alternating optimization strategy dealing with the exact l1/l2 term

<p>This report focused on the suboptimization of a logistics support system that is assumed to be in existence. A minimum steady-state level of spares was sought to meet a demand due to the discarding of failed items.</p> / Master of Science

<p>During the early stages of the acquisition cycle for a military equipment, the question arises as to how the system will be maintained at an operationally capable level. The desired level of readiness must be balanced against the cost of system maintenance. The primary question to be answered is what is the optimum (i.e., least cost) maintenance concept which will allow the system to meet its specified performance goals. In order to answer this question, one must compare the costs associated with the possible choices in maintenance alternatives.</p> <p> Level of Repair Analysis, or LORA for short, is an optimization technique used to determine the optimum level of repair for each component in the system. Premised on accurately addressing selected system life-cycle maintenance costs, the methodology, data requirements, and algorithms used to conduct a LORA are found in Military Standard 1390C, Level of Repair Analysis.</p> <p> LORA examines the feasibility of repair from both technical (non-economic) and economic standpoints. The optimization process will determine whether it is feasible to repair an item, and if so, where and how. While LORA is an excellent and necessary tool, like many analyses of its type, it has limitations. Like any analytical tool, one must understand both the strengths and weaknesses of the process to properly apply its techniques and interpret its results. Data collection and entry into a computer model can be made relatively easily. Paramount however to properly applying the techniques and results is a thorough understanding of the LORA process. Therefore, the primary focus of this project and report is to illustrate the strengths and limitations of the WRA process by its application to a specific example. It is not intended to pass judgement on the LORA process as implemented and utilized by DOD. Rather, it is intended that this report present an overview of the LORA process and detail some of the nuances one could expect to encounter when performing a LORA.</p> <p> This report contains a description of the Level of Repair Analysis process and how this process was applied to a specific United States Department of Defense electronics system. This report documents the analysis (data and calculations used) to reach the repair and discard decisions for the NIXIE Signal Generator Engineering Change Kit for the AN/SLQ-25, a US Navy electronics equipment. This report differs from the one submitted under the contract in that it contains more theoretical detail on the overall LORA process and does not include any classified or proprietary data.</p> / Master of Engineering

Submitted by HENRIQUE KRIGUER (henriquekriguer@uol.com.br) on 2016-02-15T11:56:47Z No. of bitstreams: 1 Dissertação de Mestrado Henrique Kriguer 2015 corrigido após qualificação.pdf: 1729817 bytes, checksum: 2ab0f19734b9d93a734ea53248959168 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-02-15T12:20:05Z (GMT) No. of bitstreams: 1 kriguer_h_me_guara.pdf: 1729817 bytes, checksum: 2ab0f19734b9d93a734ea53248959168 (MD5) / Made available in DSpace on 2016-02-15T12:20:05Z (GMT). No. of bitstreams: 1 kriguer_h_me_guara.pdf: 1729817 bytes, checksum: 2ab0f19734b9d93a734ea53248959168 (MD5) Previous issue date: 2015-12-21 / O gerenciamento de estoques torna-se cada vez mais importante em função da necessidade de aperfeiçoamento da eficiência na cadeia logística, que se traduz na redução de custos e aumento do nível de serviço. A literatura sobre o gerenciamento de estoques de peças de reposição é ampla, porém é pouco abordada em relação à escolha do modelo de classificação. Neste trabalho, o método Analytic Hierarchy Process (AHP) foi aplicado em uma Empresa de bens de capital para determinar o vetor de prioridade dos critérios adotados para a classificação de peças de reposição. Apresentamos, com base no resultado deste estudo o Índice de Reposição, que foi adotado como um fator de correção nos valores de estoque segundo a classificação ABC. O objetivo foi atingido com o aperfeiçoamento do método de classificação, tornando o trabalho do planejador de estoques melhor estruturado, permitindo que possa tomar a decisão de reabastecimento de forma estruturada conforme parâmetros pré estabelecidos. / The inventory management becomes increasingly important due to the need for improved efficiency in the supply chain, which translates into cost savings and increased service level. The literature on the management of spare parts inventory is wide, but is rarely addressed in relation to the choice of classification model. In this work, the Analytic Hierarchy Process (AHP) method was applied to a Company of capital goods to determine the priority vector of the criteria adopted for the spare parts classification. Here, based on the results of this study the Replacement Index, which was adopted as a correction factor in inventory values according to the ABC classification. The goal was achieved with the improvement of classification method, making the work of the best structured inventory planner, allowing can take the form of structured replenishment decision as pre-established parameters