Dissertations / Theses on the topic 'Reentrancy'

Orientador: Iakov Veniaminovitch Kopelevitch
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: No presente trabalho estudamos os semimetais bismuto Bi, antimônio Sb e Bi1-xSbx, materiais com propriedades topologicamente não triviais. Observamos a ocorrência de supercondutividade intrínseca em bismuto com TC »= 8:5K. Construímos, a partir dos dados de magnetização e resistência, o diagrama de fase do campo crítico H versus a temperatura T. Esse diagrama de fase, pode ser ajustado segundo modelos da literatura válidos para supercondutividade granular. Detectamos, no bismuto, o aumento da corrente Josephson e acoplamento intergranular no limite quântico devidos à quantização de Landau. Isso se manifesta como uma supercondutividade reentrante. Foi também encontrada transição tipo metal-isolante induzida por campo magnético em todos os materiais estudados. O diagrama de fase H versus T mostra uma extraordinária semelhança entre os três materiais. A amostra Bi1-xSbx, com x = 0:052, revelou a ocorrência de transição semimetal-isolante topológico já em campo magnético zero. Fizemos uma comparação com resultados anteriores da literatura, analisando a dependência da temperatura em que ocorre essa transição em relação à concentração de antimônio x e ao campo magnético B e demonstramos a similaridade entre eles. Observamos, também, supercondutividade nos semimetais bismuto, antimônio e no Bi1-xSbx, induzida por dopagem com os metais ouro e índio, e mostramos que a supercondutividade está associada à interface entre os metais e os semimetais. Finalmente, encontramos a indução de supercondutividade mediante a aplicação de campo magnético em bismuto, consistente com a ocorrência de férmions de Majorana na interface entre esse material e a tinta prata usada para os contatos. Tal observação pode ser devida, também, à ocorrência de um estado supercondutor fora do equilíbrio.
Abstract: In this work we studied the semimetals bismuth Bi, antimony Sb and Bi1-xSbx, all of them with non-trivial topologic properties. We observed an intrinsic superconductivity in bismuth, with TC »= 8:5 K. The phasediagram of the critical field H versus the temperature T, based upon the magnetization and resistance data, may be well fitted according to theoretical models valid for granular superconductivity. We also detected, in bismuth, the increase of the Josephson current and interganular coupling in the quantum limit due to Landau quantization. This manifests itself as a reentrant superconducting state. Our results revealed a metal-insulator transition triggered by magnetic field, for all the studied materials. The phase diagram H ¡T shows a striking similarity between them. The sample Bi1-xSbx with x = 0:052 demonstrated a semimetal-insulator transition even at zero field. We compared our results with previous results of other groups and analyzed the temperature dependence of the transition as a function of the antimony amount x and the magnetic field B and demonstrated their similarity. We also observed supeerconductivity in the semimetals bismuth, antimony and Bi1-xSbx, triggered by doping with the metals gold and indium, and showed that the superconductivity is associated to the interface between the metals and the semimetals. Finally, we found the superconductivity induced by the aplication of magnetic field in bismuth, consistent with the Majorana fermions present in the interface between this material and the silver paste contacts. This may also be related to a non-equilibrium superconduting state.
Doutorado
Física
Doutor em Ciências

This dissertation presents a study of instabilities in the propagation of excitation pulses within spatially-distributed models of cardiac reentry. In one-dimensional closed rings, I study the onset of oscillations in the dynamics of circulating pulses as the ring length is decreased. In two-dimensional sheets, I analyze the spontaneous breakup of rotating spiral waves. In both cases, numerical results illustrating the instability phenomena are obtained using simulations of a partial differential equation (PDE) that models cardiac electrical activity using the Beeler-Reuter (BR) equations. The properties of the PDE model are summarized using the restitution and dispersion curves. The restitution curve gives the dependence of the pulse duration on the recovery time, defined as the elapsed time between the onset of an excitation pulse and the end of the previous excitation pulse. The dispersion curve gives the dependence of the pulse speed on the recovery time. I use these two properties to construct simplified models aimed at capturing the essence of the instabilities observed in the PDE. On the ring, I derive an integral-delay equation for the evolution of the recovery time as a function of the distance along the ring that incorporates the restitution and the dispersion curves. Numerical simulations and bifurcation analysis of the delay equation explain and predict the dynamics of the PDE. In two-dimensions, I extend early work that presented the first clear demonstration of spiral wave breakup in a reasonable discretization of a continuous PDE model of cardiac propagation. Spiral breakup can be observed in the BR model, depending on the value of a parameter controlling the duration of the electrical pulses. I study the appearance of spiral wavebreaks and relate it to the change in restitution properties of the BR equations as the parameter is varied. Finally, the effects of restitution and dispersion in two dimensions are examined in a discrete space/continuous time model of cardiac propagation. Results about the dependence of the propagation speed on the excitation threshold and on the excitation front curvature are obtained analytically. Inclusion of restitution relations derived from the BR equations into this simple model can give rise to spiral wavebreaks.

La programación orientada a aspectos (POA) es un paradigma de programación. Permite encapsular funcionalidad que se encuentra dispersa en un sistema. Para ello utiliza pointcuts, predicados que definen eventos del programa, y advices, el código que es ejecutado en los eventos definidos por un pointcut. Un aspecto es una entidad que agrupa pointcuts y advices. AspectJ es un lenguaje de programación para POA. Está diseñado como una extensión de Java, de forma que cualquier programa Java es también un programa AspectJ válido. Además del compilador oficial del proyecto AspectJ existen otros, de los cuales AspectBench Compiler (abc) es el más avanzado. La reentrancia de aspectos ocurre cuando la ejecución de un aspecto desencadena nuevamente su propia ejecución; produciéndose bucles infinitos. Actualmente la reentrancia se soluciona utilizando chequeos y patrones adhoc. La introducción de niveles de ejecución evita la reentrancia de aspectos. La ejecución del programa se separa en distintos niveles. Por defecto, la computación base ocurre en el nivel 0, mientras que los aspectos que observan esta ejecución se ubican en el nivel 1. La ejecución en el nivel 1 sólo puede ser observada desde el nivel 2, y así sucesivamente. Esta estructura para la ejecución de los programas soluciona casi todos los casos de reentrancia. Para el caso faltante, se utiliza un mecanismo adicional de control de reentrancia. Para esta memoria se extendió el compilador abc para incorporar una adaptación de niveles de ejecución. El lenguaje soportado por el compilador extendido incorpora nueva sintaxis para ello. Y los programas compilados contienen rutinas adicionales que agregan la estructura de niveles de ejecución y el control de reentrancia. Además, es posible controlar el nivel de ejecución en que se ejecutará una expresión, si fuese necesario. Se hicieron distintas pruebas para validar el trabajo realizado. Se confeccionaron tests para las distintas funcionalidades que, en conjunto, implementan niveles de ejecución. También se verificó la correcta compilación y ejecución de AJHotDraw, un framework para interfaces gráficas de programas de dibujo. Adicionalmente se probó el compilador con RacerAJ, una herramienta para la detección de data races implementada en AspectJ. RacerAJ es de interés porque incorpora pointcuts para evitar la ocurrencia de reentrancia de aspectos; removidos estos pointcuts, el programa funciona correctamente al ser compilado con esta versión extendida de abc. Además se realizó un ligero análisis de performance para medir el impacto en los programas compilados. Para ello se utilizó una suite de benchmarks para AspectJ. Se compararon los tiempos de ejecución logrados al utilizar el compilador desarrollado y la versión original.

This thesis describes a study of reentrant metal-insulator transitions observed in the inversion layer of extremely high mobility Si-MOSFETs. Magneto-transport measurements were carried out in the temperature range 20mK-4.2 K in a $\sp3$He/$\sp4$He dilution refrigerator which was surrounded by a 15 Tesla superconducting magnet. Below a melting temperature $(T\sb{M}\sim500$ mK) and a critical electron density $(n\sb{s}\sim9\times10\sp $ cm$\sp{-2}),$ the Shubnikov-de Haas oscillations in the diagonal resistivity enormous maximum values at the half filled Landau levels while maintaining deep minima corresponding to the quantum Hall effect at filled Landau levels. At even lower electron densities the insulating regions began to spread and eventually a metal-insulator transition could be induced at zero magnetic field. The measurement of extremely large resistances in the milliKelvin temperature range required the use of very low currents (typically in the $10\sp{-12}$ A range) and in certain measurements minimizing the noise was also a consideration. The improvements achieved in these areas through the use of shielding, optical decouplers and battery operated instruments are described. The transport signatures of the insulating state are considered in terms of two basic mechanisms: single particle localization with transport by variable range hopping and the formation of a collective state such as a pinned Wigner crystal or electron solid with transport through the motion of bound dislocation pairs. The experimental data is best described by the latter model. Thus the two dimensional electron system in these high mobility Si-MOSFETs provides the first and only experimental demonstration to date of the formation of an electron solid at zero and low magnetic fields in the quantum limit where the Coulomb interaction energy dominates over the zero point oscillation energy. The role of disorder in favouring either single particle localization or the formation of a Wigner crystal is explored by considering a variety of samples with a wide range of mobilities and by varying the ratio of the carrier density (controlled by the applied gate voltage) to the impurity density (fixed during sample growth). A phase diagram showing the boundaries between the two dimensional electron gas, the Wigner solid, and the single particle localization induced insulator is established in terms of carrier density and sample mobility.

This study presents a new simulation-based local search approach for solving shop scheduling problems. Results for classical problems from the literature demonstrate the effectiveness and quality of the approach. Application is also shown for reentrant flexible job shop with sequence dependent setup times (RFJSSDS), a new, very general, class of problems. RFJSSDS is a generalization of the classical job shop, reentrant flow shop and flexible job shop problems. Multiple products (routes), sequence dependent setup times at the work centers and reentrancy of the jobs make RFJSSDS one of the more general and difficult shop scheduling problems. Examples of this type of problem include semiconductor wafer fabrication facilities and flexible machining systems. The solution methodology developed in this study features a new Simulation Based Local Improvement with Multi Start (SBLIMS) algorithm. The local search procedure modifies an initial feasible solution provided by the simulation module to generate promising neighbor solutions. A generated solution is considered to be better if there is a reduction in the total completion time or makespan. A unique filtering strategy is used to select and rank moves, using both task and resource views of a schedule. Multiple random starting points are generated in multistart fashion as part of the solution process. New theorems are presented that form the basis for SBLIMS. The SBLIMS algorithm was evaluated using test instances for several shop scheduling problems as well as RFJSSDS. A set of synthetic problems was generated to study RFJSSDS, because there were no RFJSSDS instances available from the literature. The SBLIMS algorithm was compared with various dispatch rules in the RFJSSDS domain and its performance was found to be better in most cases. SBLIMS was also tested with well known special cases of RFJSSDS: the classical job shop, reentrant flow shop and flexible job shop problems. The SBLIMS algorithm provided excellent results compared with those provided in the literature, establishing the generality of the approach for solving a broad class of shop scheduling problems.

Este trabalho se ocupa da tradução comentada para o português do Instruccion de Musica sobre la Guitarra Espanõla, de Gaspar Sanz (1697), um dos mais importantes livros de repertório e de instruções de como tocar a guitarra de cinco ordens, que ora denominamos guitarra barroca. A tradução procura contextualizar o texto de Sanz, levando ao leitor, mesmo aquele não habituado à leitura dos tratados dos séculos XVII e XVIII, subsídios que lhe permitam compreender o texto e tirar utilidade prática de seu conteúdo. Assim como o Instruccion, o trabalho aborda temas os mais diversos concernentes à guitarra barroca: música solística, para a compreensão da qual a afinação reentrante mostra-se essencial, música de acompanhamento em suas diferentes vertentes, Rasqueado, Ponteado e Obbligato, instruções de afinação, ornamentação, escolha das cordas e diferentes afinações. Abrange também, embora não como objetivo principal, uma proposta de metodologia para transcrição da tablatura original, levando em conta a afinação reentrante modificada. Os comentários sobre o vasto conteúdo do Instruccion baseiam-se na leitura da obra de Sanz, no cotejamento com outras fontes primárias e secundárias, mas também, e não menos importante, na minha experiência como instrumentista de cordas dedilhadas antigas há mais de quinze anos. Todos os exemplos e transcrições trazem o fac-símile para confronto, convidando o leitor a exercer sua curiosidade em relação às fontes primárias e fazendo disto, de fato, seu principal objetivo.
This work deals with the commented translation into Portuguese of the Instruccion de Musica sobre la Guitarra Española , by Gaspar Sanz (1697), one of the most important books of repertoire and instructions on how to play the five orders guitar, we now call baroque guitar. This translation aims to contextualize Sanz\'s, text, leading the reader, even those not used to reading the treaties of the seventeenth and eighteenth centuries, subsidies to help understanding the text and make practical use of it\'s content. As the Instruccion, this work addresses the most diverse topics concerning the baroque guitar: solo music, where reentrant tuning shows to be essential to their understanding, accompanying music in its various aspects, rasqueado, ponteado and obbligato, ornamentation, choice of chords and different tunings. It also covers, although not as its main objective, a proposed methodology for transcription of the original tablature, taking into account the modified reentrant tuning. Comments on the vast content of the Instruccion are based on the reading of Sanz\'s work in mutual comparison with other primary and secondary sources, but also, and not least, in my experience as a player of early plucked strings over fifteen years. All examples and transcriptions bring also the facsimile, inviting the reader to exercise their curiosity about primary sources and making it in fact their main goal.

Post-myocardial infarction arrhythmias are a leading cause of death in developed countries, motivating research to improve treatment strategies. Ischemic damage occurring due to a myocardial infarction results in the formation of inexcitable infarct scars. Electrical activation waves circumvent these structural barriers and can propagate in perpetual reentrant circuits giving rise to ventricular tachycardia. The success of reentrant propagation depends on the wavelength of the activation wave with respect to the physical path length, determining the extent of wavefront-waveback interactions. A wide variety of animal and computational models are used to perform research however, the optimal species for studying clinical arrhythmias is unknown. One aim of the research in this Thesis was to suggest a species model which most closely replicates clinical arrhythmia dynamics. Computational models were utilised to compare the susceptibility to reentry, by calculating the effective electrical size of the heart, which takes into consideration both the size of the wavelength and the physical size of the heart. Results suggested that species differences in effective size exist between human and animal models. However, the effective size of the rabbit model was most similar to the human. This conclusion was utilised to formulate methodologies for the following studies. Current techniques employed to locate ablation lesion sites during radiofrequency catheter ablation are inaccurate, leading to insufficient procedure success rates. Here, a method to accurately locate optimal ablation lesion targets was investigated utilising computational models. Quantification of wavelength permitted the observation of wavefront-waveback interactions to predict susceptibility to reentry. The clinical application of the methodology was modelled to ensure that ablation of the susceptible tissue could terminate reentry and that the limitations of clinical data acquisition did not invalidate the technique. The method accurately located a region of tissue where reentry could potentially occur and ablation of the region terminated reentry even when clinical protocol was simulated. This research suggests the most suitable species models to research ventricular tachycardia, guiding further in vivo and in silico methodologies. Additionally, a protocol to improve the success of the ablation procedure has been further investigated. Clinical implementation of this technique could vastly improve the treatment of post-myocardial infarction arrhythmias.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2012.
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A ligação direta entre pilares e lajes de concreto armado é uma alternativa cada vez mais freqüente nos projetos de construção civil. Diversos fatores podem indicar a conveniência da utilização de um modelo estrutural do tipo laje lisa, ou solução com pilar apoiado em uma laje. Em ambos os casos, têm-se a situação da carga aplicada em uma área reduzida, gerando tensões de cisalhamento significativas na região da laje ao redor do pilar ou área carregada. Assim a laje tende a romper por punção. Neste trabalho foram investigados o comportamento estrutural e a resistência última à punção de ligações entre lajes lisas e pilares de canto reentrante. As principais variáveis consideradas foram: armadura de cisalhamento e excentricidade de carga na ligação. Foram ensaiados quatro modelos locais de ligação laje-pilar de canto reentrante, distribuídos em dois grupos: um com duas lajes sem armadura de cisalhamento, ensaiadas com diferentes excentricidades de carga e o outro grupo com duas lajes, uma com três e a outra com quatro camadas de double headed studs com disposição radial. Foram analisados os resultados de cargas últimas, fissuração, deslocamento vertical, deformações das armaduras de flexão e de cisalhamento e do concreto, e rotação das lajes. A armadura de cisalhamento e as diferentes excentricidades de carga influenciaram o comportamento e a carga de ruptura das lajes. Essas influências foram quantificadas. Os resultados experimentais foram comparados com os estimados segundo as normas: NBR 6118:2007, Eurocode 2:2004 e ACI 318:2008. Para os modelos sem armadura de cisalhamento as estimativas de resistência à punção obtidas com a NBR 6118:2007 e o Eurocode 2:2004 foram semelhantes aos resultados obtidos experimentalmente, enquanto que o ACI 318:2008 apresentou resultados mais conservadores de resistência à punção em relação aos observados em laboratório. _________________________________________________________________________________ ABSTRACT
The direct link between reinforced concrete columns and slabs is an alternative increasingly common in civil construction projects. Several factors may indicate the convenience of the use of a structural model of the type flat slab or with column supported by a slab. In both cases, there is the situation of load applied in a small area, generating significant shear stresses in the region of the slab around the column or the loaded area, thus the slab tends to fail by punching. In this work it was investigated the structural behavior and ultimate punching strength of connections between flat slabs and reentrant corner columns. The main variables considered were shear reinforcement and eccentricity of the load on the link. Four local models of slab-reentrant corner column link were tested, divided in two groups: one with two slabs without shear reinforcement tested with different load eccentricities and the other with two slabs, one with three and the other with four layers of double headed studs with radial layout. It was analyzed the results of ultimate load, cracking, vertical displacement, strains in bending and shear reinforcement and at the bottom surface of the concrete, and slab rotation. The shear reinforcement and different load eccentricities influenced the behavior and rupture load of the slabs. These influences were quantified. The experimental results were compared with those estimated according to the codes: NBR 6118:2007, Eurocode 2:2004 and ACI 318: 2008. For models without shear reinforcement, estimates of punching strength obtained with NBR 6118:2007 and Eurocode 2:2004 were similar to those obtained experimentally, while ACI 318:2008 presented more conservative results of punching strength than those observed in laboratory.

Acute myocardial ischemia is the main cause of ventricular tachycardia and ventricular fibrillation. Reentrant activity is the most common mechanism of these ventricular arrhythmias, and is often initiated from the border zone between the ischemic and normal tissue. Theoretical studies have suggested that spiral-wave activity may be one form of reentrant arrhythmia. Our study explores the possible relation between spiral-wave activity and ischemia-induced ventricular arrhythmias. We numerically simulate reentrant activity in a two-dimensional sheet of ventricular myocardium which contains an ischemic area. We construct this ischemic area by increasing the extracellular potassium concentration in that area. When pacing the sheet with a sequence of stimuli delivered at a sufficiently high frequency, different types of spiral waves are initiated either within the ischemic area itself or in the normal area close to the ischemic boundary, depending on the potassium concentration in the ischemic area. The formation of the spiral wave is influenced by several factors such as the frequency of stimulation, the geometry of the ischemic area, and the exact level of the extracellular potassium concentration in the ischemic area. Future work should model the ischemic area more realistically with a spatially-extended border zone.

[EN] Atrial tachyarrhythmias present a high prevalence in the developed world, and several studies predict that in the coming decades it will be increased. Micro or macro-reentrant mechanisms of the electrical wavefronts that govern the mechanical behavior of the heart are one of the main responsibles for the maintenance of these arrhythmias. Atrial flutter is maintained by a macro-reentry around an anatomical or functional obstacle located in the atria. In the case of atrial fibrillation, the hypothesis which describes high frequency rotors as dominant sources of the fibrillation and responsible for the maintenance of the arrhythmia, has been gaining relevance in the last years. However, the therapies that target high frequency sources have a limited efficacy with current techniques. Radiofrequency ablation allows the destruction of parts of the cardiac tissue resulting in the interruption of the reentrant circuit in case of macro-reentries or the isolation of micro-reentrant circuits. The non-invasive location of reentrant circuits would increment the efficacy of these therapies and would shorten surgery interventions. In parallel, pharmacological therapies modify ionic expressions associated to the excitability and electrical refractoriness of the cardiac tissue with the objective of hindering the maintenance of reentrant behaviors. These therapies require a deep knowledge of the ionic mechanisms underlying the reentrant behavior and its properties in order to be effective. The research in these mechanisms allows the evaluation of new targets for the treatment and thus may improve the efficacy in atrial fibrillation termination. In this thesis, mathematical modeling is used to go forward in the minimization of the limitations associated to these treatments. Body surface potential mapping has been evaluated, both clinically and by means of mathematical simulations for the diagnosis and location of macro-reentrant circuits. The analysis of phase maps obtained from multiple lead electrocardiographic recordings distributed in the whole torso allowed the discrimination between different reentrant circuits. It is the reason why this technique is presented as a tool for the non-invasive location of macro and micro-reentrant circuits. A population of mathematical models designed in this thesis based on the action potentials recordings of atrial cardiomyocites from 149 patients, allowed the evaluation of the ionic mechanisms defining the properties of reentrant behaviors. This study has allowed us defining the blockade of ICaL as a target for the pharmacological treatment. The blockade of this current is associated with the increase of the movement in the core of the rotor which easies the collision of the rotor with other wavefronts or anatomical obstacles promoting the extinction of the reentry. The variability observed between patients modeled in our population has allowed showing and explaining the mechanisms promoting divergent results of a single treatment. This is why the introduction of populations of models will allow the prevention of side effects associated to inter-subject variability and to go forward in the development of individualized therapies. These works are built through a simulation platform of cardiac electrophysiology based in Graphic Processing Units (GPUs) and developed in this thesis. The platform allows the simulation of cellular models, tissues and organs with a realistic geometry and shows features comparable to that of the platforms used by the most relevant electrophysiology research groups at the moment.
[ES] Las taquiarritmias auriculares tienen una alta prevalencia en el mundo desarrollado, además diversos estudios poblacionales indican que en las próximas décadas ésta se verá incrementada. Los mecanismos de micro o macro-reentrada de los frentes de onda eléctricos que rigen el comportamiento mecánico del corazón, se presentan como una de las principales causas del mantenimiento de estas arritmias. El flutter auricular es mantenido por un macro-reentrada alrededor de un obstáculo anatómico o funcional en las aurículas, mientras que en el caso de la fibrilación auricular la hipótesis que define a los rotores de alta frecuencia como elementos dominantes y responsables del mantenimiento de la arritmia se ha ido imponiendo al resto en los últimos años. Sin embargo, las terapias que tienen como objetivo finalizar o aislar estas reentradas tienen todavía una eficacia limitada. La ablación por radiofrecuencia permite eliminar zonas del tejido cardiaco resultando en la interrupción del circuito de reentrada en el caso de macro-reentradas o el aislamiento de comportamientos micro-reentrantes. La localización no invasiva de los circuitos reentrantes incrementaría la eficacia de estas terapias y reduciría la duración de las intervenciones quirúrgicas. Por otro lado, las terapias farmacológicas alteran las expresiones iónicas asociadas a la excitabilidad y la refractoriedad del tejido con el fin de dificultar el mantenimiento de comportamientos reentrantes. Este tipo de terapias exigen incrementar el conocimiento de los mecanismos subyacentes que explican el proceso de reentrada y sus propiedades, la investigación de estos mecanismos permite definir las dianas terapéuticas que mejoran la eficacia en la extinción de estos comportamientos. En esta tesis el modelado matemático se utiliza para dar un paso importante en la minimización de las limitaciones asociadas a estos tratamientos. La cartografía eléctrica de superficie ha sido testada, clínicamente y con simulaciones matemática,s como técnica de diagnóstico y localización de circuitos macro-reentrantes. El análisis de mapas de fase obtenidos a partir de los registros multicanal de derivaciones electrocardiográficas distribuidas en la superficie del torso permite diferenciar distintos circuitos de reentrada. Es por ello que esta técnica de registro y análisis se presenta como una herramienta para la localización no invasiva de circuitos macro y micro-reentrantes. Una población de modelos matemáticos, diseñada en esta tesis a partir de los registros de los potenciales de acción de 149 pacientes, ha permitido evaluar los mecanismos iónicos que definen las propiedades asociadas a los procesos de reentrada. Esto ha permitido apuntar al bloqueo de la corriente ICaL como diana terapéutica. Ésta se asocia al incremento del movimiento del núcleo que facilita el impacto del rotor con otros frentes de onda u obstáculos extinguiéndose así el comportamiento reentrante. La variabilidad entre pacientes reflejada en la población de modelos ha permitido además mostrar los mecanismos por los cuales un mismo tratamiento puede mostrar efectos divergentes, así el uso de poblaciones de modelos matemáticos permitirá prevenir efectos secundarios asociados a la variabilidad entre pacientes y profundizar en el desarrollo de terapias individualizadas. Estos trabajos se cimientan sobre una plataforma de simulación de electrofisiología cardiaca de basado en Unidades de Procesado Gráfico (GPUs) y desarrollada en esta tesis. La plataforma permite la simulación de modelos celulares cardiacos así como de tejidos u órganos con geometría realista, mostrando unas prestaciones comparables con las de las utilizadas por los grupos de investigación más potentes en el campo de la electrofisiología.
[CAT] Les taquiarítmies auriculars tenen una alta prevalença en el món desenvolupat, a més diversos estudis poblacionals indiquen que en les pròximes dècades aquesta es veurà incrementada. Els mecanismes de micro o macro-reentrada dels fronts d'ona elèctrics que regeixen el comportament mecànic del cor, es presenten com una de les principals causes del manteniment d'aquestes arítmies. El flutter auricular és mantingut per una macro-reentrada al voltant d'un obstacle anatòmic o funcional en les aurícules, mentre que en el cas de la fibril·lació auricular la hipòtesi que defineix als rotors d'alta freqüència com a elements dominants i responsables del manteniment de l'arítmia s'ha anat imposant a la resta en els últims anys. No obstant això, les teràpies que tenen com a objectiu finalitzar o aïllar aquestes reentrades tenen encara una eficàcia limitada. L'ablació per radiofreqüència permet eliminar zones del teixit cardíac resultant en la interrupció del circuit de reentrada en el cas de macro-reentrades o l'aïllament de comportaments micro-reentrants. La localització no invasiva dels circuits reentrants incrementaria l'eficàcia d'aquestes teràpies i reduiria la durada de les intervencions quirúrgiques. D'altra banda, les teràpies farmacològiques alteren les expressions iòniques associades a la excitabilitat i la refractaritat del teixit amb la finalitat de dificultar el manteniment de comportaments reentrants. Aquest tipus de teràpies exigeixen incrementar el coneixement dels mecanismes subjacents que expliquen el procés de reentrada i les seues propietats, la recerca d'aquests mecanismes permet definir les dianes terapèutiques que milloren l'eficàcia en l'extinció d'aquests comportaments. En aquesta tesi el modelatge matemàtic s'utilitza per a fer un pas important en la minimització de les limitacions associades a aquests tractaments. La cartografia elèctrica de superfície ha sigut testada, clínicament i amb simulacions matemàtiques com a tècnica de diagnòstic i localització de circuits macro-reentrants. L'anàlisi de mapes de fase obtinguts a partir dels registres multicanal de derivacions electrocardiogràfiques distribuïdes en la superfície del tors permet diferenciar diferents circuits de reentrada. És per açò que aquesta tècnica de registre i anàlisi es presenta com una eina per a la localització no invasiva de circuits macro i micro-reentrants. Una població de models matemàtics, dissenyada en aquesta tesi a partir dels registres dels potencials d'acció de 149 pacients, ha permès avaluar els mecanismes iònics que defineixen les propietats associades als processos de reentrada. Açò ha permès apuntar al bloqueig del corrent ICaL com a diana terapèutica. Aquesta s'associa a l'increment del moviment del nucli que facilita l'impacte del rotor amb altres fronts d'ona o obstacles extingint-se així el comportament reentrant. La variabilitat entre pacients reflectida en la població de models ha permès a més mostrar els mecanismes pels quals un mateix tractament pot mostrar efectes divergents, així l'ús de poblacions de models matemàtics permetrà prevenir efectes secundaris associats a la variabilitat entre pacients i aprofundir en el desenvolupament de teràpies individualitzades. Aquests treballs es fonamenten sobre una plataforma de simulació de electrofisiologia cardíaca basat en Unitats de Processament Gràfic (GPUs) i desenvolupada en aquesta tesi. La plataforma permet la simulació de models cel·lulars cardíacs així com de teixits o òrgans amb geometria realista, mostrant unes prestacions comparables amb les de les utilitzades per els grups de recerca més importants en aquesta área.
Liberos Mascarell, A. (2016). Mathematical modeling approaches for the diagnosis and treatment of reentrant atrial tachyarrhythmias [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62166
TESIS

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2015.
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Ligações laje-pilar em lajes lisas podem romper por punção para uma carga inferior à correspondente de flexão, devido às altas tensões advindas do momento fletor e do esforço cortante, e por isso tem sido muito estudadas. No entanto, dentre os tipos de ligação lajepilar (pilar interno, de borda ou de canto), as ligações com pilares de canto reentrante não havia ainda sido estudado com profundidade, principalmente no caso de momentos desbalanceados em uma ou duas direções. Nesta pesquisa foram analisadas experimentalmente 12 (doze) ligações lajes lisas / pilar, com pilar quadrado de canto reentrante com 300 mm de lado, com espessura de 180 mm, e as principais variáveis investigadas foram a presença de armadura de cisalhamento disposta radialmente, a taxa de armadura de flexão na região do pilar, que variou de 0,8 a 2,1%, a presença de armadura de torção no bordo, e o desbalanceamento dos momentos nas duas direções, com excentricidades variando de 267 a 504mm. Durante os ensaios foram monitoradas as deformações nas armaduras de flexão, cisalhamento e torção; deformações no concreto; deslocamentos verticais; padrão de fissuração; cargas últimas; rotações das lajes e modos de ruptura. Os resultados experimentais foram comparados com uma proposição para a determinação das resistências esperadas pelas normas NBR 6118 (2014), Eurocode 2 (2004) e ACI 318 (2014), e pelas recomendações do MC2010 (2013), pois as lajes lisas com pilares reentrantes não são abordados por estas normas e recomendações. Também foi realizada uma simulação numérica utilizando o software ATENA, que emprega o método dos elementos finitos para efetuar análises tridimensionais não lineares em estruturas de concreto armado. ____________________________________________________________________________________________________ ABSTRACT
In failure slab-column connection failure of flat slabs is observed high stresses are originated by that of bending and shearing efforts, which can cause failure by punching with a load lower than the bending. The types of slab-column connection, internal, edge, corner and re-entrant corner can appear in any deck. However the connection slab-column of reentrant corner is not discussed by any research as the other cases, its mechanical model and its behavior with unbalanced moments in one or both directions are unknown. In this research were analyzed experimentally 12 flat slabs with thickness of 180 mm, supported by a square column with sides of 300 mm and molded with machined concrete with average strength of 45 MPa. The experimental results were: strain in bending, shear and torsion reinforcement; concrete strains; vertical displacement; map of cracking; ultimate loads; rotations of the slabs and failure modes. The variables were: eccentricity, bending reinforcement ratio, amount of shear reinforcement and torsion reinforcement. Strength of punching shear get in the tests was compared with the strength provided by the NBR 6118 code (2014), Eurocode 2 (2004), ACI 318 (2014) and MC2010 (2013), but all the standards had to be adapted because they do not cover punching in slabs with reentrant corner column. Also a numerical simulation was made using the ATENA software designed to make non-linear three-dimensional analysis of reinforced concrete structures. Thus, the data monitored in the laboratory ware correlated with the results from finite element modeling. Some of the major contributions of this study were to show the general behavior of the slab connection with reentrant corner column with respect to displacements, strains, cracking, failure mode and failure surface; analyze the behavior and the adapted codes; and show how to treat this type of connection.

Ventricular fibrillation is one of the leading causes for Sudden Cardiac Death and is characterized by multiple activation wavefronts. Multiple activation wavefronts originate from a reentrant circuit which requires the presence of a unidirectional block in the path of a propagating excitation wave. It has been proposed that at the cellular level beat to beat alternation in the action potential duration at rapid pacing rates can result in a conduction block. Various mechanisms have been postulated to show the mechanisms of alternans. We use simulated activation in a one dimensional tissue fiber to show the existence of a new mechanism via which alternans can result. We used a new pacing protocol to eliminate alternans at the pacing site, and thus eliminating restitution of action potential duration at this site to reveal existence of alternans down the fiber. Effects on alternans of manipulations of specific ionic currents such as the sodium current (INa), calcium current (ICaL), potassium current (Ikr) and of the diffusion co-efficient (Dx) which simulates reduced expression of connexin 43 were determined. Decrease in sodium conductance, i.e. in excitability by half caused the alternans to occur at the pacing site itself even though APD restitution was eliminated. An increase or decrease in calcium current (ICaL) eliminated alternans throughout the fiber. The use of a novel pacing approach in investigation of alternans, as in this study, furthers our understanding of the mechanism of alternans and may prove helpful in the development of better anti-arrhythmic drugs in the future.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and, (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; in conjunction with the Leaders for Manufacturing Program at MIT, 2007.
Includes bibliographical references (p. 46).
This thesis quantifies the sensitivity of tool availability variability with respect to product throughput and examines how Intel's High Precision Maintenance initiative can be used to minimize these effects. Tools with variable availability release spikes of material into a route which can cause down stream areas to experience irregular queues. The reentrant multi product loops typical to Intel's manufacturing processes can make it difficult to identify the source of long queues. The variability analysis, developed during the internship uses D2 facility availability and cycle time data to generate a variability correlation, called TAC-TOOT which identifies tools within the facility contributing to throughput time. The High Precision Maintenance initiative is an Intel developed program which focuses on the standardization of maintenance processes. The success of the High Precision Maintenance initiative is closely linked to the ability of factory management to motivate equipment technicians. The thesis examines a number of tools with highly variable availability, the effects of the high precision initiative on variability and levers factory management can use to motivate technicians.
by Milo Camp Peavey.
M.B.A.
S.M.

La familia de transportadores heteroméricos de aminoácidos posee la característica única de estar compuestos por dos subunidades: una subunidad pesada y una subunidad ligera unidas por un puente disulfuro. Mutaciones en alguno de sus miembros son responsables de aminoacidurias hereditarias, como la lisinuria con intolerancia a proteínas (LPI) o la cistinuria.

Al inicio de esta tesis, nos propusimos identificar alguna nueva subunidad ligera humana de esta familia. Mediante búsqueda por homología de secuencia se clonó el cDNA correspondiente a una nueva proteína altamente homóloga a una proteína de ratón asociada al sistema de transporte xc-. La caracterización funcional confirmó que xCT humano, en combinación con 4F2hc, induce una actividad de transporte de cistina y glutamato, con sodio-independencia (sistema xc-). Los perfiles de captación de los sustratos en función del pH del medio de transporte indican que tanto el L-glutamato como la L-cistina son transportados de forma aniónica, cada uno con una carga negativa neta. Por experimentos de salida de sustrato se determinó el carácter intercambiador de este transportador, con una estequiometría de 1:1.
El patrón de expresión de xCT humano por Northern blot muestra una ligera banda presente únicamente en cerebro. Experimentos de RT-PCR también resultaron positivos para los islotes pancreáticos y líneas celulares correspondientes a líneas epiteliales y tumorales, mientras riñón e hígado no mostraron ninguna señal. El papel fisiológico de xCT parece estar implicado en la captación de cistina para la síntesis de glutatión y su mantenimiento, dándole un papel relevante en situaciones de estrés oxidativo.
A continuación se abordó la determinación de la topología de xCT como modelo de subunidad ligera. Experimentos de inmunodetección evidencian la localización intracelular de los dos extremos de la proteína. Utilizando la estrategia de introducir cisteínas individuales en los distintos loops y testar su accesibilidad a reactivos tiol-específicos, la topología de xCT es compatible con un modelo de 12 dominios transmembrana. Los resultados obtenidos en la zona IL2-3, con dos residuos de accesibilidad exterior (el 110 y 112) flanqueados por residuos de accesibilidad interior (el 102, 109 y 116) en un rango de 15 aminoácidos nos hacen pensar en una estructura de reentrant loop, con el residuo H110 como ápice. El hecho que estas estructuras suelen ser zonas asociadas a la ruta de paso del sustrato del transportador, nos llevó a estudiar la implicación del residuo H110.
En resumen, los resultados muestran que i) la biotinilación del residuo H110C se bloquea por los sustratos y el inhibidor no transportable 4SCPG; ii) la inactivación provocada por MTSES en el transporte de h110c también es protegida por los sustratos con una IC50 similar a la Km para cada sustrato; iii) esta protección es independiente de temperatura, y por tanto no implica grandes cambios conformacionales; y iv) aunque los mutantes H110C y H110D no alteraron la Km del transportador ni su especificidad de sustrato, la sustitución por una lisina inactiva totalmente la función de xCT. Por tanto, tenemos evidencias de que H110 se encuentra cercano al lugar de unión al sustrato o ruta de paso del mismo.
Estos resultados pueden encontrarse en las publicaciones siguientes: J Biol Chem (2004) vol. 279, 31228-36, J Biol Chem (2004) vol. 279, 11214-21, y Pflugers Arch. (2001) vol. 442 (2) 286-296.

ENGLISH
The family of heteromeric amino acid transporters has the particular characteristic of being composed of two proteins: a light subunit (LSHAT) and a heavy subunit (HSHAT) linked by a disulfide bridge. Some of its members are associated with hereditary aminoacidurias. Characterisation of a new human LSHAT, responsible for transport system xc-, is reported here. Human xCT associates with 4F2 heavy chain and induces cystine/glutamate exchange with sodium independence and 1:1 molar ratio.
Topology studies using immunodetection and substituted cysteine accessibility method reveal a model compatible with 12 transmembrane domains and intracellular N and C-terminus. The results obtained in the intracellular loop between 2 and 3 transmembrane domain (IL2-3), with two residues of extracellular accessibility (110 and 112) flanked by residues of intracellular accessibility (the 102, 109 and 116) in a rank of 15 amino acids, resembles the structure of a reentrant loop with apex in position H110. The fact that these structures are usually associated with the substrate pathway through the transporter, lead us to further studies with residue H110.
In summary, the results on that position show that: i) biotinylation of H110C is blocked by its substrate and the non-transportable inhibitor 4-S-carboxiphenyl-glycine (4-S-CPG); (ii) the inactivation caused by MTSES in the transport of mutant H110C is also protected by each substrate with a IC50 similar to the Km; (iii) this protection is independent of temperature, and therefore it does not imply great conformational changes; and (iv) although mutants H110C and H110D did not alter the Km of the transporter nor their specificity of substrate, the substitution by a lysine inactivates the function of xCT totally. Therefore, we conclude that residue H110 resides near the binding site/translocation pathway of the substrates in the transporter xCT.
These results can be found in the following publications: J Biol Chem (2004) vol. 279, 31228-36, J Biol Chem (2004) vol. 279, 11214-21, y Pflugers Arch. (2001) vol. 442 (2) 286-296.

Etude de l'ordre magnetique et des transitions de phase dans les systemes de spins frustres. Une attention particuliere est donnee au phenomene de reentrance, au probleme du champ aleatoire et aux excitations elementaires lorsque les spins sont quantiques

This work is motivated by the pressing need for operational control in the fabrication of Microelectromechanical systems or MEMS. MEMS are miniature three-dimensional integrated electromechanical systems with the ability to absorb information from the environment, process this information and suitably react to it. These devices offer tremendous advantages owing to their small size, low power consumption, low mass and high functionality, which makes them very attractive in applications with stringent demands on weight, functionality and cost. While the system''s "brain" (device electronics) is fabricated using traditional IC technology, the micromechanical components necessitate very intricate and sophisticated processing of silicon or other suitable substrates. A dearth of fabrication facilities with micromachining capabilities and a lengthy gestation period from design to mass fabrication and commercial acceptance of the product in the market are factors most often implicated in hampering the growth of MEMS. These devices are highly application specific with low production volumes and the few fabs that do possess micromachining capabilities are unable to offer a complete array of fabrication processes in order to be able to cater to the needs of the MEMS R&D community. A distributed fabrication network has, therefore, emerged to serve the evolving needs of this high investment, low volume MEMS industry. Under this environment, a central facility coordinates between a network of fabrication centers (Network of MEMS job shops -- NMJS) containing micromachining capabilities. These fabrication centers include commercial, academic and government fabs, which make their services available to the ordinary customer. Wafers are shipped from one facility to another until all processing requirements are met. The lengthy and intricate process sequences that need to be performed over a network of capital intensive facilities are complicated by dynamic job arrivals, stochastic processing times, sequence-dependent set ups and travel between fabs. Unless the production of these novel devices is carefully optimized, the benefits of distributed fabrication could be completely overshadowed by lengthy lead times, chaotic routings and costly processing. Our goal, therefore, is to develop and validate an approach for optimal routing (assignment) and sequencing of MEMS devices in a network of stochastic job shops with the objective of minimizing the sum of completion times and the cost incurred, given a set of fabs, machines and an expected product mix. In view of our goal, we begin by modeling the stochastic NMJS problem as a two-stage stochastic program with recourse where the first-stage variables are binary and the second-stage variables are continuous. The key decision variables are binary and pertain to the assignment of jobs to machines and their sequencing for processing on the machines. The assignment variables essentially fix the route of a job as it travels through the network because these variables specify the machine on which each job-operation must be performed out of several candidate machines. Once the assignment is decided upon, sequencing of job-operations on each machine follows. The assignment and sequencing must be such that they offer the best solution (in terms of the objective) possible in light of all the processing time scenarios that can be realized. We present two approaches for solving the stochastic NMJS problem. The first approach is based on the L-shaped method (credited to van Slyke and Wets, 1969). Since the NMJS problem lacks relatively complete recourse, the first-stage solution can be infeasible to the second-stage problem in that the first stage solution may either violate the reentrant flow conditions or it may create a deadlock. In order to alleviate these infeasibilities, we develop feasibility cuts which when appended to the master problem eliminate the infeasible solution. Alternatively, we also develop constraints to explicitly address these infeasibilities directly within the master problem. We show how a deadlock involving 2 or 3 machines arises if and only if a certain relationship between operations and a certain sequence amongst them exists. We generalize this argument to the case of m machines, which forms the basis for our deadlock prevention constraints. Computational results at the end of Chapter 3 compare the relative merits of a model which relies solely on feasibility cuts with models that incorporate reentrant flow and deadlock prevention constraints within the master problem. Experimental evidence reveals that the latter offers appreciable time savings over the former. Moreover, in a majority of instances we see that models that carry deadlock prevention constraints in addition to the reentrant flow constraints provide at par or better performance than those that solely carry reentrant flow constraints. We, next, develop an optimality cut which when appended to the master problem helps in eliminating the suboptimal master solution. We also present alternative optimality and feasibility cuts obtained by modifying the disjunctive constraints in the subproblem so as to eliminate the big H terms in it. Although any large positive number can be used as the value of H, a conservative estimate may improve computational performance. In light of this, we develop a conservative upper bound for operation completion times and use it as the value of H. Test instances have been generated using a problem generator written in JAVA. We present computational results to evaluate the impact of a conservative estimate for big H on run time, analyze the effect of the different optimality cuts and demonstrate the performance of the multicut method (Wets, 1981) which differs from the L-shaped method in that the number of optimality cuts it appends is equal to the number of scenarios in each iteration. Experimentation indicates that Model 2, which uses the standard optimality cut in conjunction with the conservative estimate for big H, almost always outperforms Model 1, which also uses the standard optimality cut but uses a fixed value of 1000 for big H. Model 3, which employs the alternative optimality cut with the conservative estimate for big H, requires the fewest number of iterations to converge to the optimum but it also incurs the maximum premium in terms of computational time. This is because the alternative optimality cut adds to the complexity of the problem in that it appends additional variables and constraints to the master as well as the subproblems. In the case of Model 4 (multicut method), the segregated optimality cuts accurately reflect the shape of the recourse function resulting in fewer overall iterations but the large number of these cuts accumulate over the iterations making the master problem sluggish and so this model exhibits a variable performance for the various datasets. These experiments reveal that a compact master problem and a conservative estimate for big H positively impact the run time performance of a model. Finally, we develop a framework for a branch-and-bound scheme within which the L-shaped method, as applied to the NMJS problem, can be incorporated so as to further enhance its performance. Our second approach for solving the stochastic NMJS problem relies on the tight LP relaxation observed for the deterministic equivalent of the model. We, first, solve the LP relaxation of the deterministic equivalent problem, and then, fix certain binary assignment variables that take on a value of either a 0 or a 1 in the relaxation. Based on this fixing of certain assignment variables, additional logical constraints have been developed that lead to the fixing of some of the sequencing variables too. Experimental results, comparing the performance of the above LP heuristic procedure with CPLEX over the generated test instances, illustrate the effectiveness of the heuristic procedure. For the largest problems (5 jobs, 10 operations/job, 12 machines, 7 workcenters, 7 scenarios) solved in this experiment, an average savings of as much as 4154 seconds and 1188 seconds was recorded in a comparison with Models 1 and 2, respectively. Both of these models solve the deterministic equivalent of the stochastic NMJS problem but differ in that Model 1 uses a big H value of 1000 whereas Model 2 uses the conservative upper bound for big H developed in this work. The maximum optimality gap observed for the LP heuristic over all the data instances solved was 1.35%. The LP heuristic, therefore, offers a powerful alternative to solving these problems to near-optimality with a very low computational burden. We also present results pertaining to the value of the stochastic solution for various data instances. The observed savings of up to 8.8% over the mean value approach underscores the importance of using a solution that is robust over all scenarios versus a solution that approximates the randomness through expected values. We, next, present a dynamic stochastic scheduling approach (DSSP) for the NMJS problem. The premise behind this undertaking is that in a real-life implementation that is faithful to the two-stage procedure, assignment (routing) and sequencing decisions will be made for all the operations of all the jobs at the outset and these will be followed through regardless of the actual processing times realized for individual operations. However, it may be possible to refine this procedure if information on actual processing time realizations for completed operations could be utilized so that assignment and sequencing decisions for impending operations are adjusted based on the evolving scenario (which may be very different from the scenarios modeled) while still hedging against future uncertainty. In the DSSP approach, the stochastic programming model for the NMJS problem is solved at each decision point using the LP heuristic in a rolling horizon fashion while incorporating constraints that model existing conditions in the shop floor and the actual processing times realized for the operations that have been completed. The implementation of the DSSP algorithm is illustrated through an example problem. The results of the DSSP approach as applied to two large problem instances are presented. The performance of the DSSP approach is evaluated on three fronts; first, by using the LP heuristic at each decision point, second, by using an optimal algorithm at each decision point, and third, against the two-stage stochastic programming approach. Results from the experimentation indicate that the DSSP approach using the LP heuristic at each decision point generates superior assignment and sequencing decisions than the two-stage stochastic programming approach and provides solutions that are near-optimal with a very low computational burden. For the first instance involving 40 operations, 12 machines and 3 processing time scenarios, the DSSP approach using the LP heuristic yields the same solution as the optimal algorithm with a total time savings of 71.4% and also improves upon the two-stage stochastic programming solution by 1.7%. In the second instance, the DSSP approach using the LP heuristic yields a solution with an optimality gap of 1.77% and a total time savings of 98% over the optimal algorithm. In this case, the DSSP approach with the LP heuristic improves upon the two-stage stochastic programming solution by 6.38%. We conclude by presenting a framework for the DSSP approach that extends the basic DSSP algorithm to accommodate jobs whose arrival times may not be known in advance.
Ph. D.

Etude par effet moessbauer de **(57)fe de l'occupation en fonction de sa concentration x des sites interstitiels tetraedriques, par l'hydrogene dans erfe::(2)h::(x). Comparaison des champs hyperfins sur les noyaux de fer aux moments magnetiques obtenus par diffraction de neutrons. Etude des alliages au::(0,96)fe::(0,03)sn::(0,01) (verre de spin) et au::(0,79)fe::(0,19)sn::(0,02) (ferromagnetique reentrant) par effet moessbauer sur **(57)fe et **(119)sn. Mise en evidence d'amas ferromagnetiques dans au::(0,79)fe::(0,19)sn::(0,02) par etude moessbauer en presence de champ applique

L'industrie des semi-conducteurs est caractérisée par une production de forte variabilité et de faible volume, des flux de production ré-entrants ainsi que d'un processus de fabrication complexe. Au sein de ce contexte industriel complexe, a été considéré un problème de planification à capacité finie. C'est le problème de projection des encours de production et des commandes clients à capacité finie. Il s'agit d’estimerles dates de début, les temps d'attente et les dates de fin de chacun des steps des différents lots ainsi que la charge accumulée sur les équipements. Cette projection doit tenir compte des contraintes de capacité et qualifications des équipements et des dates d'échéance de livraison des lots. La contrainte de qualification définit l'éligibilité d'un équipement à traiter un produit. Ainsi, l'objectif de cette étude consiste à établir un plan de production réalisable à moyen terme. Afin de réaliser cet objectif, des méthodes exactes et approchées sont proposées. Des résultats en termes de complexité, et d'algorithmes de résolution, ont permis une application industrielle, dans la mesure où un logiciel de planification de la production à capacité finie a été développé
In this study, we consider the problem of production planning in the semiconductor industry characterized by high mix low volume production, reentrant flows and complex manufacturing process.The aim of this work is to establish a feasible production schedule that takes into account the limited capacity of the manufacturing system, equipment qualifications constraints and delivery due dates. In this context, we have formulated the objective and constraints in a mixed linear program (MIP). The objective of the MIP is to minimize delivery delays to guarantee on-time delivery. While executing different tests of the MIP, we have reached a limit of resolution in a reasonable time. Thus, we use an approximate method to solve the problem. The results show the effectiveness of the heuristic established as solution quality and time resolution.The obtained results led to an industrial application and a software that provides feasible schedules in reduced execution time in a specific fab

Made available in DSpace on 2016-08-19T18:20:34Z (GMT). No. of bitstreams: 1 Juliana Fukuda.pdf: 14767349 bytes, checksum: 528a36df5cb8d77aa472422e59b6b486 (MD5) Previous issue date: 2006-11-30
The protected areas (PAs) for nature conservation are important tools for maintaining ecological function and biodiversity conservation in a determined region. Specific laws for their protection are applied in the defined space within their limits. Thus, considering boundaries definition as a characteristic of fundamental importance to reach the goals for which the protected area has been created, in this work we aimed to evaluate socioeconomic- cultural and environmental features, and also management and political variables for suggesting boundaries to a marine costal protected area (MCPA) in the Reentrâncias Maranhenses region, with special attention to the municipality of Porto Rico do Maranhão. This portion of coast is characterized for its high nutrients levels, macro-tidal regimes, large continental shelf and exuberant mangroves, and the artisanal fishing as the main economic activity. We limited the purpose of this study to the managed MCPAs. We used interviews, field observations, water and sediment samples and secondary information to reach the following goals: 1) survey on the MCPAs in Brazil, analysing the management difficulties answered by their managers related to the boundaries definition; 2) discussion whether to create a new protected area in the region and its advantages; 3) characterize the local fishery and the direct users of fishery resources; 4) make a list of vertebrates species (not including herpetofauna) and benthos species which have occurrence indication in the area; 5) classify the local environments based on orbital images and field work; 6) sample estuarine waters for physical and chemical analysis; 7) consider land tenure, fishery management and navigation safety issues. The main contributions of this work are: a) information on 141 publicly managed coastal and marine protected areas; b) confirmation that in the older protected areas there have been fewer studies on boundary definition, in inverse proportion to current occurrence of management problems. These studies have been more frequent in the Extractive Reserves than in the Environmental Protected Areas; c) indications of an unsustainable fishery, socially, economically and environmentally endangering the region; d) occurrence indication of 89 fish morphospecies, 25 of shore birds and 6 of mammals, emphasizing the ones in danger of extinction; e) elaboration and analysis of a multi-criteria matrix to indicate the most important environments for protection; f) indication of an ideal area for protection, only considering environmental concepts and indication of an area we believe would be the most suitable for a PA, considering the other management variables. Yet, this suggestion must be discussed with all the stakeholders, in a consistent effort to make aware and empower the users so that they realize that the conflicts and problems will only be minimized with stakeholder participation and commitment to the issue.
As Unidades de Conservação (UCs) áreas protegidas para conservação da natureza são importantes instrumentos para conservação da biodiversidade e dos recursos ambientais de determinada região. Legislações específicas para sua proteção se aplicam ao espaço definido pelos seus limites. Desta forma, considerando a delimitação de uma UC como característica de fundamental importância para atingir os objetivos pelas quais a área foi criada, buscamos neste trabalho avaliar características ambientais e sócio-econômico-culturais, bem como variáveis políticas e de gestão, para sugerir limites para uma Unidade de Conservação costeiro-marinha (UCCM) na região das Reentrâncias Maranhenses, com especial atenção à região do município de Porto Rico do Maranhão. Esta porção da costa é caracterizada pelo alto aporte de nutrientes, regime de macro-marés, plataforma continental larga e manguezais exuberantes, sendo a pesca artesanal a principal atividade econômica. O escopo deste trabalho foi limitado às UCCMs de uso sustentável. Através de entrevistas, observações de campo, coleta de água e sedimento, e dados secundários, realizaramse: 1) levantamento das UCCMs de uso sustentável do Brasil, analisando-se as dificuldades de gestão relacionadas aos limites da área, de acordo com seus atuais gestores; 2) discussão sobre a necessidade e vantagens de se criar uma nova UC na região; 3) caracterização da pesca e dos usuários diretos dos recursos pesqueiros na região; 4) listagem das espécies de vertebrados (exceto herpetofauna) e de bentos de ocorrência na área; 5) classificação de ambientes lcoais com base em imagens orbitais e trabalho de campo; 6) amostragem de águas estuarinas para análises físicoquímicas; 7) considerações referentes a questões fundiárias, de pesca e de segurança da navegação. Como principais contribuições deste trabalho citam-se: a) levantamento de dados referentes a 141 UCCMs de uso sustentável, exceto RPPNs; b) confirmação de que as UCs mais antigas tiveram menos estudos para delimitação da área a ser protegida, em proporção inversa à ocorrência de problemas de gestão atuais. Entre as Reservas Extrativistas os estudos foram mais freqüentes do que entre as Áreas de Proteção Ambiental; c) demonstração de indícios de insustentabilidade da atividade pesqueira, com comprometimento social, econômico e ambiental da região; d) indicação de ocorrência de 89 morfoespécies de peixes, 25 de aves costeiras e 6 de mamíferos, destacando-se espécies ameaçadas de extinção; e) elaboração e análise de uma matriz-multi-critérios, para indicar ambientes mais importantes para proteção; f) indicação de uma área ideal para proteção, considerando apenas conceitos ambientais, e de uma área que acreditamos ser a mais adequada para a uma UC, considerando demais variáveis de gestão. Esta proposta deve ainda ser discutida juntamente com todos os grupos interessados, em um esforço consistente de conscientização dos usuários e empoderamento dos mesmos, assim como promoção de alternativas de geração de renda, de forma que eles percebam que os conflitos existentes só serão minimizados com a própria participação e comprometimento da comunidade interessada em relação à questão.

Experiments show that MgSO4 salt has a non-monotonic effect as a function of MgSO4 concentration on the ejection of DNA from bacteriophage lambda. There is a concentration, N0, at which the minimum amount of DNA is ejected. At lower or higher concentrations, more DNA is ejected. We propose that this non-monotonic behavior is due to the overcharging of DNA at high concentration of Mg⁺² counterions. As the Mg⁺² concentration increases from zero, the net charge of ejected DNA changes its sign from negative to positive. N0 corresponds to the concentration at which DNA is neutral. Our theory fits experimental data well. The DNA-DNA electrostatic attraction is found to be -0.004 kBT/nucleotide. Simulations of DNA-DNA interaction of a hexagonal DNA bundle support our theory. They also show the non-monotonic DNA-DNA interaction and reentrant behavior of DNA condensation by divalent counterions. Three problems in understanding the capsid assembly for a retrovirus are studied: First, the way in which the viral membrane affects the structure of in vivo assembled HIV-1 capsid is studied. We show that conical and cylindrical capsids have similar energy at high surface tension of the viral membrane, which leads to the various shapes of HIV-1 capsids. Secondly, the problem of RNA genome packaging inside spherical viruses is studied using RNA condensation theory. For weak adsorption strength of capsid protein, most RNA genomes are located at the center of the capsid. For strong adsorption strength, RNA genomes peak near the capsid surface and the amount of RNA packaged is proportional to the capsid area instead its volume. Theory fits experimental data reasonably well. Thirdly, the condensation of RNA molecules by nucleocapsid (NC) protein is studied. The interaction between RNA molecules and NC proteins is important for the reverse transcription of viral RNA which relates to the viral infectivity. For strong adsorption strength of the NC protein, there is a screening effect by RNA molecules around a single NC protein.

Die vorliegende Arbeit beschäftigt sich mit der elektrischen Charakterisierung 10 nm dünner Schichten bestehend aus amorphen Ga-Nanoclustern eingebettet in Ga-dotiertes polykristallines Si. Die Herstellung der Schichten geschieht via Ionen-Implantation in Si-Wafer samt anschließender thermischer Ausheilung. Elektrische Transportmessungen in Magnetfeldern von bis zu 50 T zeigen, dass die Schichten durch Variation der Ausheilparameter zwei strukturelle Supraleiter-Isolator-Übergänge durchlaufen. TEM-gestützte Strukturanalysen decken auf, dass den Übergängen eine Gefügetransformation zugrunde liegt, die das Wechselspiel zwischen supraleitender Cluster-Kopplung und kapazitiver Ladungsenergie sowie dem Ausmaß von thermischen und Quantenfluktuationen beeinflusst. Im supraleitenden Regime (Tc = 7 K) wird ein doppelt reentrantes Phänomen beobachtet, bei dem Magnetfelder von mehreren Tesla in anisotroper Form die Supraleitung begünstigen. Eine qualitative Erklärung gelingt via selbstentwickeltem theoretischen Modell basierend auf Phaseslip-Ereignissen für Josephson-Kontakt-Netzwerke. Für Anwendungen im Bereich der Sensor-Technologie und Quanten-Logik werden die Schichten erfolgreich via Fotolithographie und FIB (focused ion beam) mikro- und nanostrukturiert. Dadurch gelingt die erstmalige Beobachtung des Little-Parks-Effektes in einer Nanostruktur aus amorphem Ga
The following thesis is devoted to the electrical characterization of 10 nm thin layers consisting of amorphous Ga nanoclusters embedded in Ga-doped polycrystalline Si. The preparation of the layers is realized via ion implantation in Si wafers plus subsequent thermal annealing. Electrical-transport measurements in magnetic fields of up to 50 T show that the layers undergo two structural superconductor-insulator transitions upon variation of the annealing parameters. Structural analyzes based on TEM investigations reveal an underlying transformation of the size and distance of the clusters. This influences the interplay of the superconducting cluster coupling and capacitive charging energy as well as the extent of thermal and quantum fluctuations. In the superconducting regime (Tc = 7 K) a double-reentrant phenomenon is observed. Here, magnetic fields of several Tesla facilitate superconductivity in an anisotropic way. A qualitative explanation is given via a self-developed theoretical model based on phase-slip events for Josephson-junction arrays. With respect to applications regarding sensor technology and quantum logic circuits the layers are successfully micro- and nanostructured via photolithography and FIB. This allows for the first observation of the Little-Parks effect in a nanostructure of amorphous Ga

Nous avons utilise la diffraction des rayons x et des neutrons ainsi que l'etude des seuils d'absorption x afin de determiner les structures cristallographiques ou magnetiques de composes de ces deux series. Dans la premiere partie, portant sur la serie des stannures de terres rares et metaux precieux, nous determinons la structure de la phase i par affinement d'un diagramme de poudre collecte avec le rayonnement synchrotron. Nous etudions plusieurs composes en phases i et i par mesure de seuils d'absorption x et montrons notamment que l'ytterbium est dans un etat de valence intermediaire dans le stannure de rhodium et d'ytterbium supraconducteur a 8 k. Nous etudions ensuite les relations entre structure magnetique, supraconductivite et composition chimique dans le stannure de rhodium et d'erbium en phase ii, supraconducteur reentrant. Nous determinons la structure magnetique et montrons que l'ordre magnetique est etabli a courte distance. Dans la deuxieme partie, nous etudions les structures de plusieurs cuprates supraconducteurs appartenant aux systemes y-ba-cu-o et (bi, pb)-sr-ca-cu-o, ainsi que des composes voisins. Nous approfondissons plus specialement les problemes lies a la stoichiometrie de ces composes, en relation avec leurs proprietes physiques. Enfin, nous comparons les structures des differents composes connus et discutons de la valence du cuivre dans ces composes

La spectroscopie d'absorption par mesure du temps de vie des photons piégés dans une cavité optique haute-finesse, ou Cavity Ring Down Spectroscopy (CRDS), compte parmi les outils de diagnostic optique les plus sensibles. L'excitation « mode matchée » d'un laser continu rapidement et continûment balayé (~4 THz.s-1 durant ~2 ms), i.e. la cw-CRDS monomode rapide, garantit à la technique ses meilleures performances en termes de limites de détectivité avec, en contrepartie, des points de mesures séparés de l'Intervalle Spectral Libre du résonateur (ISL=c/2L) : le dosage d'environnements basse pression requiert de longues cavités. Cette étude originale propose de mettre à profit la structure transverse du résonateur afin de rendre possible la miniaturisation du dispositif de cw-CRDS rapide. L'excitation multimode d'une cavité fractionnellement dégénérée (dite de taille « magique »), ici présentée, permet de bénéficier d'un gain d'échantillonnage spectral qui vaut l'ordre réentrant N employé. Nous développons deux schémas d'injection multimode : l'injection multimode axiale et l'injection multimode réentrante, dite dans ce dernier cas hors de l'axe optique, de telles cavités et nous en étudions les principales différences. Une étude détaillée du champ intracavité existant aux N résonances constitutives de l'ISL est proposée afin de rendre compte des limites de détectivités associées à ces deux schémas d'injection multimode sensiblement distincts. Une seconde partie de ce travail de thèse est dédiée à caractériser de façon approfondie l'observation des profils spatiaux intracavités formés en injection hors axe lorsque la cavité souffre d'un faible astigmatisme (ΔR/R~2 %) : on parle de profil de Lissajous. Cette étude rend compte des mécanismes fondamentaux, telle la coïncidence particulière de modes particuliers par dispersion modale, qui aboutissent en un intervalle millimétrique de dégénérescence. Celui-ci est le siège d'une succession de profils transverses de Lissajous symétriques les uns des autres de part et d'autre d'une taille particulière de cavité : nous en précisons les causes. Le résiduel astigmatisme ainsi mis en évidence et mesuré permet, en outre, d'expliquer la disparition des oscillations Doppler normalement présentent en début de décroissance ring down dans ce type d'injection dynamique. De façon connexe, nous développons plusieurs types de cellules multipassages non-résonantes comme alternative à la CRDS pour le dosage d'environnements hostiles.

La plasticité corticale du cerveau est l'une des principales caractéristiques qui nous permettent d'apprendre et de nous adapter à notre environnement. En effet, le cortex cérébral a la capacité de s'auto-organiser grâce à deux formes de plasticité : la plasticité structurelle qui crée ou coupe les connexions synaptiques entre les neurones, et la plasticité synaptique qui modifie la force des connexions synaptiques. Ces mécanismes sont très probablement à la base d'une caractéristique extrêmement intéressante du développement du cerveau humain : l'association multimodale. Malgré la diversité des modalités sensorielles, comme la vue, le son et le toucher, le cerveau arrive aux mêmes concepts. De plus, les observations biologiques montrent qu'une modalité peut activer la représentation interne d'une autre modalité lorsque les deux sont corrélées. Pour modéliser un tel comportement, Edelman et Damasio ont proposé respectivement la réentrance et la zone de convergence/divergence où les communications neurales bidirectionnelles peuvent conduire à la fois à la fusion multimodale (convergence) et à l'activation intermodale (divergence). Néanmoins, ces cadres théoriques ne fournissent pas de modèle de calcul au niveau des neurones.L'objectif de cette thèse est d'abord d'explorer les fondements de l'auto-organisat-ion inspirée par le cerveau en termes (1) d'apprentissage multimodal non supervisé, (2) de calcul massivement parallèle, distribué et local, et (3) de traitement efficace sur le plan énergétique. Sur la base de ces lignes directrices et d'une étude des modèles neuronaux de la littérature, nous choisissons la carte auto-organisée (SOM) proposée par Kohonen comme composant principal de notre système. Nous introduisons la grille itérative, une architecture entièrement distribuée avec une connectivité locale entre les neurones matériels qui permet un calcul cellulaire dans le SOM, et donc un système qui passe à l'échelle en termes de temps de traitement et de connectivité.Ensuite, nous évaluons la performance du SOM dans le problème de l'apprentissage non supervisé post-étiqueté : aucun label n'est disponible pendant l'entrainement, puis très peu de labels sont disponibles pour étiqueter les neurones du SOM. Nous proposons et comparons différentes méthodes d'étiquetage afin de minimiser le nombre d'étiquettes tout en conservant la meilleure précision. Nous comparons nos performances à une approche différente utilisant des réseaux neuronaux à spike (SNN).Ensuite, nous proposons d'améliorer les performances du SOM en utilisant des caractéristiques extraites au lieu de données brutes. Nous menons une étude comparative sur la classification du SOM avec extraction non-supervisée de caractéristiques à partir de la base de données MNIST en utilisant deux approches différentes : une approche d'apprentissage machine avec des auto-encodeurs convolutionnels et une approche bio-inspirée avec des SNN.Pour prouver la capacité du SOM à classifier des données plus complexes, nous utilisons l'apprentissage par transfert dvec la base de données mini-ImageNet.Enfin, nous passons au mécanisme d'association multimodale. Nous construisons le modèle bio-inspiré ReSOM basé sur les principes de réentrance en utilisant les SOMs et l'apprentissage Hebbien. Nous proposons et comparons différentes méthodes de calcul pour l'apprentissage et l'inférence multimodale non supervisée, puis nous quantifions le gain des mécanismes de convergence et de divergence sur trois bases de données multimodales. Le mécanisme de divergence est utilisé pour étiqueter une modalité à partir de l'autre, tandis que le mécanisme de convergence est utilisé pour améliorer la classification globale du système. Nous comparons nos résultats avec des SNNs, puis nous montrons le gain de la plasticité dite matérielle induite par notre modèle, où la topologie du système n'est pas fixée par l'utilisateur mais apprise au fil de l'expérience du système par l'auto-organisation
The brain's cortical plasticity is one of the main features that enable our capability to learn and adapt in our environment. Indeed, the cerebral cortex has the ability to self-organize itself through two distinct forms of plasticity: the structural plasticity that creates (sprouting) or cuts (pruning) synaptic connections between neurons, and the synaptic plasticity that modifies the synaptic connections strength. These mechanisms are very likely at the basis of an extremely interesting characteristic of the human brain development: the multimodal association. In spite of the diversity of the sensory modalities, like sight, sound and touch, the brain arrives at the same concepts. Moreover, biological observations show that one modality can activate the internal representation of another modality when both are correlated. To model such a behavior, Edelman and Damasio proposed respectively the Reentry and the Convergence Divergence Zone frameworks where bi-directional neural communications can lead to both multimodal fusion (convergence) and inter-modal activation (divergence). Nevertheless, these theoretical frameworks do not provide a computational model at the neuron level.The objective of this thesis is first to explore the foundations of brain-inspired self-organization in terms of (1) multimodal unsupervised learning, (2) massively parallel, distributed and local computing, and (3) extremely energy-efficient processing. Based on these guidelines and a review of the neural models in the literature, we choose the Self-Organizing Map (SOM) proposed by Kohonen as the main component of our system. We introduce the Iterative Grid, a fully distributed architecture with local connectivity amongst hardware neurons which enables cellular computing in the SOM, and thus a scalable system is terms of processing time and connectivity complexity.Then, we assess the performance of the SOM in the problem of post-labeled unsupervised learning: no label is available during training, then very few labels are available for naming the SOM neurons. We propose and compare different labeling methods so that we minimize the number of labels while keeping the best accuracy. We compare our performance to a different approach using Spiking Neural Networks (SNNs) with Spike Timing Dependant Plasticity (STDP) learning.Next, we propose to improve the SOM performance by using extracted features instead of raw data. We conduct a comparative study on the SOM classification accuracy with unsupervised feature extraction from the MNIST dataset using two different approaches: a machine learning approach with Sparse Convolutional Auto-Encoders using gradient-based learning, and a neuroscience approach with SNNs using STDP learning.To prove the SOM ability to handle more complex datasets, we use transfer learning in the mini-ImageNet few shot classification benchmark to exploit a Wide Residual Network backbone trained on a base dataset as a feature extractor, then we use the SOM to classify the obtained features from the target dataset.Finally, we move into the multimodal association mechanism. We build the Reentrant SOM (ReSOM), a brain-inspired neural system based on the Reentry principles using SOMs and Hebbian-like learning. We propose and compare different computational methods for multimodal unsupervised learning and inference, then quantify the gain of both convergence and divergence mechanisms on three multimodal datasets. The divergence mechanism is used to label one modality based on the other, while the convergence mechanism is used to improve the overall accuracy of the system. We compare our results to SNNs with STDP learning and different fusion strategies, then we show the gain of the so-called hardware plasticity induced by our model, where the system's topology is not fixed by the user but learned along the system's experience through self-organization

Le rôle du désordre sur les phases onde de densité de spin induites par le champ magnétique (ODSIC) a été étudié sur un monocristal de (TMTSF)2ClO4. Les propriétés à basse température de ce conducteur organique quasi-unidimensionnel dépendent de la vitesse de refroidissement au passage de la transition de mise en ordre des anions qu'il subit à 24 kelvins. Nous avons utilisé cet effet de cinétique pour contrôler le taux de désordre dans l'échantillon. Nos investigations ont été effectuées à l'aide de mesures calorimétriques: d'une part, des mesures simultanées de la chaleur spécifique et de l'effet magnétocalorique en champ variable, et d'autre part, des mesures de la chaleur spécifique en champ fixe. Nous avons mis en évidence un nouveau comportement multicritique en un point de la ligne de transition du second ordre, qui sépare la phase métallique et les sous-phases ODSIC. La criticité de ce point passe de "tétracritique" à bicritique lorsque le désordre augmente. Le point "tétracritique" peut être interprété comme le résultat de la superposition de deux sous phases-ODSIC adjacentes. Nous rapportons aussi un effet de dépairage de paires électron-trou induit par le désordre non magnétique Ce dépairage diffère du comportement universel. De plus l'écart par rapport à ce dernier dépend du champ magnétique. Enfin il n'est pas monotone en fonction du champ. Par ailleurs, les mesures que nous avons effectuées montrent que la mise en ordre des anions n'influence pas directement les réentrances partielles de l'état métallique dans les sous-phases ODSIC entre 3 et 7 teslas. Ceci permet de penser que, dans ce domaine de champs magnétiques, la bande interdite ouverte dans le spectre d'énergie du fait de la mise en ordre des anions ne serait pas directement responsable des réentrances.

博士
國立臺灣科技大學
工業管理系
91
Most production scheduling-related research assumes that a job visits certain machines at most once. A new type of manufacturing system, the reentrant shop, has recently become prominent. In a reentrant shop, a job may be processed by a certain machine many times. This research studies the problem of scheduling the reentrant job-shop (RJS), reentrant flow-shop (RFS), and reentrant permutation flow-shop (RPFS) with the objective of minimizing the makespan of jobs. This dissertation first proposes six mixed binary integer programming (BIP) models and two level division procedures for the RJS scheduling problems. The six RJS models proposed are RJS-1, RJS-2, RJS-3, RJS-4, RJS-5, and RJS-6. LDB (Level Division by Backtracking) and LDR (Level Division by Reentering) are the two level division procedures. The outcome of the LDB and LDR procedures are incorporated into both the RJS-5 and RJS-6 models to generate the RJS-5B, RJS-5R, RJS-6B, and RJS-6R formulations, respectively. In addition, totally seven mixed BIP models are presented for the RFS and RPFS scheduling problems, where models of RFS-1, RFS-2, RFS-3, and RFS-4 are for the RFS problems, and the other three models of RPFS-1, RPFS-2, and RPFS-3 are for the RPFS problems. This research also presents heuristic methods to solve RJS, RFS, and RPFS problems. For the RJS and RFS problems, this research presents heuristic procedures, including ACT and NDY, based on active and non-delay schedules. Random sampling procedures are used to compare ACT and NDY procedures and test the combinations of 12 priority rules with ACT and NDY. For the RPFS problems, there are six extended heuristic methods provided, and they are RPFS-H1, RPFS-H2, RPFS-H3, RPFS-H4, RPFS-H5, and RPFS-H6 heuristics. Finally, all the mixed BIP models and heuristic methods are tested and their performance measures of such schedules are evaluated and compared.

碩士
輔仁大學
管理學研究所
95
A good production scheduling may reduce the production cost effectively, increase the operation efficiency, and reduce the idle capacity. It also may deliver products or services to customers in time. The just-in-time concept is more and more popular, and delivering products to customers in time becomes an important factor of the customer satisfaction. Its concept is to hope the finishing time of jobs may close to the due date. The past literatures mostly set the due date as a point. However, it is usually an interval in practice. So this study set the due date as an interval. Most production scheduling-related research assumes that a job visits certain machines at most once. A new type of manufacturing system, the reentrant shop, has recently become prominent. In a reentrant shop, a job may be processed by a certain machine many times. This research discusses a production scheduling with muti-type reentrant flow. The objective is to minimize the sum of total earliness and total tardiness. It proved the ACO is stable, and is effective in efficiency and time.

碩士
雲林科技大學
工業工程與管理研究所碩士班
96
Flow-shop scheduling is one of the most important and popularly discussed subjects in production scheduling. In the recent years, the development of flexible manufacturing system caused the traditional production styles to expand their original characters into reentrant processing, particularly in semi-conductor industry and printed circuit board industry. Moreover, the applications in reentrant job-shop scheduling or reentrant flow-shop scheduling are distinctive from the traditional ones. In this study, some characteristics such as the reentrant processing and buffer limit within the shop stations are taken into account for the proposed a flow shop scheduling problem with minimization of the makespan. Two heuristics based on particle swarm optimization (PSO) and hybrid genetic algorithm (HGA) are developed for solving the proposed scheduling problem. The experimental results demonstrate that the hybrid genetic algorithm achieves higher solution quality than particle swarm optimization heuristic; nevertheless, particle swarm optimization provides more solution efficiency than hybrid genetic algorithm.

碩士
輔仁大學
管理學研究所
95
The industrial environment is getting more and more competitive today. It is a big challenge for companies to enhance their competency by using their resources efficiently and raising the productivity. Through scheduling technology, we can deliver our products in time, increase our productivity, and enhance our competency. In the traditional setting of scheduling, each job only process on one stage once. However, a job could pass certain stage for several times in a reentrant flow shop. And such kind of producing system can be found in some high tech industry and some specific producing systems. Production sequencing problem with reentrant work flow is getting more and more popular in recent year. As we review all the literatures about the reentrant flow shop with multiple processors, we found that most of them only consider single object, which is not sufficient to fulfill what companies really need today. So we consider the multiple objects, the cost of tardiness, job waiting time, and machine idling time. And we try to apply the ant colony system to solve the NP-complete scheduling problem. Our study uses the integer programming and ant colony system, and we compare the results by simulated data. We prove that the ant colony system is good at timeliness and robustness. And it’s much better than LINGO 8.0 in timeliness. It can provide a quality solution within a reasonable time.

碩士
國立交通大學
工業工程與管理系
87
This thesis develops a heuristic dispatching rule for wafer fabrication. Queue-time limit, rework, due date, WIP and so on are some key factors to be considered in the proposed dispatching rule. To demonstrate the effectiveness of the proposed dispatching rule, a simple++ simulation model with real fabrication data is employed. Two sets of conventional dispatching rules : (1)commonly used rules includes FIFO and SPT and (2)due-date-based rules including EDD and Slack. Results show that the proposed dispatching rule does give a better performance.

碩士
輔仁大學
企業管理學系管理學碩士班
99
It is needless to say that high-tech industry is one of representative industries in the world. All corporations are pursuing the goal of maximizing effective and efficiency. But, how they achieve this target is a key issue need to find out. In this case, corporations must attain these objectives which are the improvements of produce effective, satisfactory of customer, and creating the ability of continually profiting via allocating resources properly. The reentrant production scheduling points out that a procedure of making a product may come from a machine processing more time. And it is easy to see this common scene in high-tech industries such as, semiconductor manufacturing. Because of this, the reentrant production problem is gaining more and more attention in recent year. Particle swarm optimization (PSO) has been proven to be a tool of achieving effective and efficient in data clustering, financial forecasting, image processing, etc., but PSO isn’t easily seen in scheduling comparing to other traditional algorithms. This study will use basic PSO concept to improve PSO, named as the Farness Particle Swarm Optimization (FPSO), and compare results of its computational result with the traditional PSO and Ant Colony Optimization (ACO). Experiments confirmed that the FPSO provides both time and solving efficiencies.

碩士
國立成功大學
醫學資訊研究所
107
To explore the possibilities of deep learning techniques for interpreting medical images, we work with the Division of Cardiology within the Department of Internal Medicine of National Cheng Kung University Hospital. We outline some related challenges in machine learning for medical image processing and image analysis. Through multi-convolution operation with a large number of medical images, the target feature map is extracted from the images. After that, we get a prediction model which could be used to assist medical researches or medical diagnoses. We pay attention to the deep learning of electrocardiogram (ECG) since deep learning is an extensive and fast-developing field. We extract the electrocardiogram of the single disease-atrioventricular reentrant tachycardia (AVRT) from the database, hope to pre-process the data according to patient's electrocardiogram, apply image recognition and deep learning techniques to the ECG disease prediction and distinguish the characteristic differences between the onset and the normal ECG. We produce a deep learning model to cross-align these ECGs, and train the model to learn image recognition by the characteristics of the ECGs. By this method, we can obtain a prediction model with the accuracy of 96%, which predicts ECGs of a normal person and ECGs of AVRT patients before the attack. Also, we make another model be trained with ECGs of AVRT patients after the attack, we get another prediction model with the accuracy of 82%. Our goal is to apply deep learning to medical processes to assist medical diagnosis and treatment course.

碩士
輔仁大學
企業管理學系管理學碩士班
107
Scheduling is an important part of production management, and its purpose is to effectively allocate production resources. With the advancement of science and technology, the production system of enterprises has become more complicated. How to improve the performance of production systems with good production schedule has become an important goal pursued by firms which have scheduling problems. 　　Reentrant scheduling problem and no-wait scheduling problem have been proven to be NP-hard in the production schedule, while scheduling problems with no-wait constraint and reentrant are more complex, such as the manufacturing process of wafer fabrication. In several production scheduling environments, flexible flow shop is common in many industries, such as assembly, pharmaceutical and high-tech industries. Therefore, this study focuses on the flexible flow shop Scheduling Problem with no-wait and Reentrant constraints, and proposes the modified genetic algorithm solves the problem in an effective way. 　　The research result of the simulation data shows that the overall improvement rate of the modified genetic algorithm is 19.95%, which is better than 16.76% of the genetic algorithm. As for robustness, both the modified genetic algorithms and the genetic algorithms have robustness rate of more than 87.58%. The results of t-test confirmed that the average solution of the modified genetic algorithm appeared significant different in the average solution of the gene algorithm, indicating that the modified genetic algorithm is better than the genetic algorithm.