Thesis (Ph.D.)--Pennsylvania State University, 2005. / Mode of access: World Wide Web.

Computational simulations using empirical force fields are frequently used to model guest-host interactions in porous periodic systems, where the interaction energy is broken into electrostatic and van der Waals contributions. While simulations such as these have been instrumental in progressing our understanding of neutral periodic systems, limitations in deriving partial atomic charges has largely contributed to the difficulty in modeling charged periodic frameworks. However, many nanoporous materials possess frameworks that have a net charge, which is balanced by counter-ions that intercalate through the pores. For example, virtually all zeolites used in practice contain a proportion of Al, which bestows the framework with a negative charge. In this respect, we investigate two methods for the generation of partial atomic charges in periodic systems having a net framework charge. First, we examine the validity of generating REPEAT electrostatic potential fitted charges derived from periodic electronic structure calculations, where a constant background charge is added to neutralize the net charge on the framework without adding neutralizing counter-ions. The second method we explore is the split charge equilibration (SQE) method for very rapid charge generation. In its original formulation, the SQE model cannot be applied to systems with a net charge. In this work, we reformulate the SQE method for non-neutral systems to be treated. The new SQE model, which we call SQEAB, was shown to give equivalent results to those of the original SQE model for neutral systems. For charged frameworks, the model was shown to provide partial atomic charges in good agreement with the DFT derived REPEAT method. Taking advantage of that work, we next focus on the development of a force field for modeling CO2, N2, and CH4 gas adsorption in both neutral and charged zeolites, which we call the AMP (Aluminosilicate MicroPorous) force field. Commonly, the electrostatic potential of zeolites is represented through the use of generic charges, where every atom of the same type in the framework is assigned the same atomic charge. Though this model is fast, it fails to account for structural differences between framework geometries. In this work, we have optimized a set of SQEAB parameters to reproduce the DFT derived electrostatic potentials (ESPs) of a structurally representative set of both neutral and charged zeolite frameworks. Comparing with other popular models, the SQEAB-AMP charges are shown to better reproduce the QM ESP by more than 30%, on average. Gas uptakes obtained using SQEAB AMP charges were found to be within 5% of those obtained using DFT derived charges. We have further optimized a set of Lennard-Jones parameters to be combined the SQEAB-AMP charges that reproduce experimental uptake data in zeolites.

Le contrôle de la morphologie de la couche active en optoélectronique organique représente un objectif majeur du fait de son impact sur la stabilité et les performances des dispositifs. En particulier, le degré d'autoorganisation d'un mélange de deux composés à caractère donneur (D) et accepteur (A) d’électrons, ainsi que leurs orientations sont déterminants pour obtenir à la fois un de transfert de charges efficace et des chemins de percolation continus jusqu'aux électrodes. Durant ce travail de thèse, nous avons synthétisé plusieurs séries de co-oligomères à blocs donneur-accepteur capables de s’auto-organiser pour former des lamelles alternées D/A à longue distance. Les co-oligomères présentent une architecture moléculaire de type diade (DA) ou triade (DAD ou ADA), et sont constitués d’une longueur de bloc D variable. Les molécules sont toutes composées d'un bloc A à base de perylène diimide et d'un bloc D contenant les motifs thiophène, fluorène et benzothiadiazole. Une attention particulière a été portée sur l'étude des propriétés optiques, électrochimiques, photophysiques, structurales ou encore opto-électroniques de nos matériaux. En particulier, nous nous avons montré que l’organisation lamellaire était très fortement dépendante de l’architecture moléculaire, puisque seuls les systèmes AD et ADA conduisent à une structuration à longue distance. Par ailleurs, en ajustant la densité électronique au sein du bloc D, nous avons montré qu’il était possible de contrôler à la fois le temps de formation et la durée de vie des états à transfert de charges. Enfin,les premiers résultats de caractérisation du transport de charges et des propriétés photovoltaïques démontrent l’intérêt de ces matériaux dans la réalisation de dispositifs photovoltaïques organiques mono-composants. / In the field of organic opto-electronics, the good control of the active layer morphology in devices represents a major objective to improve the stability and the photovoltaic performances. Especially when blends of selforganizing electron donor (D) and acceptor (A) moieties are combined, their mutual orientation and the degree of supramolecular ordering are determinant in controlling the fundamental energy, the electron transfer processes and the existence of continuous percolation pathways for charge carriers. In this work, we have designed and synthesized different series of donor-acceptor block co-oligomers able toself-assemble in a lamellar structure at very long range. The co-oligomers are made of a dyad (AD) or triad (DAD, or ADA) molecular architecture, and have a variable length of the D block. The A block is constituted of a perylene diimide unit, and the D block of benzothiadiazole, thiophene and fluorene segments. A particular attention was paid on the studies of optical, electrochemical, photophysical, structural and opto-electronical properties. In particular, we showed that the lamellar organization was strongly dependent on the molecular architecture, since only the AD and ADA systems lead to long-range organization. Moreover, by tuning the electronic density along the D block, it has been possible to control both the formation and lifetime of the charge transfer states. Finally, the first results on charge transport and photovoltaic properties demonstrate the high interest of these materials for the elaboration of single component organic photovoltaic devices.

M.Comm. ( Accounting) / Globally, the temperature is rising and some of the consequences are starting to show. This effect is known as global warming. The issue of global warming and environmental pollution is more serious than people realise as it is the starting point of potentially catastrophic events to come. The implementation of global emission reductions is imperative in order to prevent further global warming. All countries should be actively involved in the prevention of further global warming and the reduction of pollution. With the use of a comparative analysis of various environmental taxes internationally, the countries with established environmental tax frameworks can be used as a basis for the development of effective environmental tax frameworks in developing countries. This will ensure that developed as well as developing countries will be held accountable for their emissions and hopefully will make efforts to reduce their emissions. South Africa has very few environmental tax policies and the existing acts are not sufficient to ensure the effective reduction and management of its emissions. Successful environmental tax policies are those that are economically viable and easy to implement. This is achieved through successful implementation by the tax authorities as well as the taxpayers’ cooperation and acknowledgement of these policies.

L’analyse dynamique non linéaire constitue la méthode la plus efficace pour l'évaluation de la réponse non linéaire des structures soumises à de fortes sollicitations sismiques. Compte tenu de la complexité associée à l'analyse non linéaire temporelle, l'utilisation de l'analyse statique équivalente «Push-over » constitue une alternative simple et efficace à l'analyse dynamique temporelle. Cette thèse développe une méthode statique non linéaire innovante pour évaluer le comportement sismique des immeubles de grande hauteur.Dans la première partie, le modèle "continuum" qui est un outil simple et efficace de l'analyse des immeubles de grande hauteur à contreventement mixte est revisité. L'influence de la précision de calcul dans la détermination de la hauteur optimale d'interruption des voiles est examinée tout en analysant la relation entre la hauteur optimale et les sollicitations induites. La deuxième partie propose une nouvelle procédure Push-over adaptative à exécution unique pour l'évaluation sismique des structures. Cette méthode possède deux avantages principaux : elle représente un outil pratique intégrant l’effet des modes supérieurs avec une interaction complète entre eux. D'un autre côté, elle permet d'éviter les critiques relatives aux analyses adaptatives à exécution unique. La troisième partie présente une méthode innovante permettant la détermination du point de fonctionnement des immeubles de grande hauteur. Le principe des méthodes adaptatives Push-over à exécution unique est intégré à la méthode du spectre de capacité proposé par le règlement ATC -40 dont l'application est limitée aux structures oscillant au mode fondamental. / Non linear dynamic analysis constitutes the most powerful method for the assessment of the non linear seismic response of structures subjected to strong earthquake motions. Considering the complexity associated to time history analysis, the use of nonlinear static techniques, or pushover analysis constitutes an efficient and easy to use alternative to dynamic analysis. This thesis develops innovative static nonlinear method to assess the seismic behavior of high-rise buildings. It is composed of three parts:In the first part, the continuum model which constitutes a simple and efficient tool to analyze high-rise wall-frame buildings is revisited. The influence of calculation precision in specifying the optimum level of wall curtailment is discussed. The relationship between the curtailment level and the resulting internal forces is investigated. The second part proposes a new single-run adaptive pushover method for the seismic assessment of shear wall structures. This method has two main advantages: It is practical tool to integrate the effect of higher modes with full interaction between them and it overcomes the criticisms forwarded against the previous single-run adaptive pushover analyses. The proposed method is presented as well as its numerical implementation. The third part presents an innovative method to specifying the seismic peak response quantities of the tall structures. The principle of the single-run adaptive pushover procedures is integrated with the capacity spectrum method proposed by ATC-40 (1996). Where, this latter is limited for structures that vibrate primarily in the fundamental mode.

<p> In this thesis we study three problems of joint pricing and inventory in a retail setting.</p> <p> The first problem deals with pricing and ordering for a retailer facing uncertain supply as well as price-sensitive uncertain demand. We first formulate the problem as two cases of pricing: a simultaneous pricing strategy where the price and the order quantity are simultaneously determined and a postponed pricing strategy where the price and the order quantity are sequentially determined. We provide a solution procedure to find the optimal price and order quantity that maximizes the retailer's profit. By conducting sensitivity analysis, we find that if the supplier is very unreliable, then the retailer is better off postponing the pricing decision in order to maximize profit. Reducing supply variability does not have the same impact on retailer's profit as much as increasing the expected supply amount. Most importantly we find that the difference between the expected profits in the two cases is not due to higher expected revenue, but due to lower expected salvage and shortage losses when the pricing decision is postponed.</p> <p> Next, we study a price setting retailer selling two substitutable goods to consumers. The retailer must decide on the optimal price and inventory that maximize the expected profit. Aside from making these decisions under demand uncertainty, the retailer must also account for the substitution that occurs upon stock out of one of the two products. Furthermore, we also take into account the related cannibalization of the available stock due to customers substituting. We formulate the problem and find the optimal prices analytically as well as conduct sensitivity analysis. We compare our findings to a model that does not consider substitution and the resultant cannibalization of inventory and find that the model that does not consider substitution tends to overestimate the expected profit for low degrees of substitution and tends to underestimate the expected profit for high degrees of substitution. Furthermore, the prices charged and the inventory held at the retailer for each product, tend to be suboptimal. The total quantity stocked in general, for both products, is lower when we account for substitution and cannibalization.</p> <p> Lastly, we study the problem of finding optimal order quantities and prices for the bundle (a collection of two or more goods sold jointly at one price) and individual items as well as how a supplier can use bundles to achieve coordination with its retailer. In a decentralized supply chain, we show that bundling is not always a feasible or a very profitable strategy. This is especially true if the products or the bundle are discounted beyond a certain point, because it may make the supplier worse off while making the retailer better off. This reduces the effectiveness of the bundling strategy in a supply chain setting. We find that the supplier, retailer and the supply chain can simultaneously improve their profits by offering bundled goods to the consumers and achieve performance of a coordinated supply chain when the supplier charges the retailer a bundling fee upfront and in exchange offering a bundling discount to the retailer.</p> <p> In the last chapter, we summarize our findings as well as provide direction for future research.</p> / Thesis / Doctor of Philosophy (PhD)

La contribution significative de cette thèse se situe dans le domaine de la déformation sismique de différents types de barrages en enrochement. La déformation excessive permanente à la crête d'un barrage causée par les secousses du sol menacera la sécurité du barrage. Les caractéristiques de ces barrages et la gravité des tremblements de terre (quantifiée par des mesures d'intensité, c'est-à-dire des IM) sont identifiées comme les composants les plus critiques impliquées dans la performance sismique du barrage. Dans la première partie, une étude est réalisée sur la déformation sismique (tassement de la crête) des barrages en enrochement avec masque en béton (CFRD) et sa corrélation avec les IM de mouvements de sol. De cette manière, l'importance des principales caractéristiques des charges cycliques dans une étude de cas CFRD typique modélisée numériquement est soulignée. On en conclut qu'en plus de l'amplitude et de la durée du mouvement de sol, la réponse du barrage est fortement affectée par les caractéristiques de fréquence du séisme. En rassemblant les histoires de cas de CFRD disponibles et en analysant leur tassement sismique, un nouveau IM est proposé pour décrire efficacement le potentiel d'un séisme à induire un règlement dans les CFRD. Une nouvelle relation prédictive est alors établie qui relie la IM suggérée et l'amplitude du tremblement de terre avec le tassement de crête étudié des cas CFRDs. Dans la deuxième partie, les données disponibles pour les barrages en enrochement à noyau de terre (ECRD) comprenant les valeurs de tassement rapportées et les mouvements de sol enregistrés lors des tremblements de terre sont analysées. Deux nouvelles approches sont développées en introduisant deux nouveaux IM et en les corrélant au règlement observé des cas ECRD. Les IM proposés pour les ECRD prennent en compte l'influence des aspects essentiels concernant le comportement non linéaire des barrages lors de séismes violents: dégradation de la rigidité des matériaux, augmentation de l'énergie dissipée et augmentation des périodes de vibration des barrages. Ces problèmes sont affectés par la déformation induite par le tremblement de terre, à travers laquelle la corrélation avec la déformation d'un barrage est découverte. Les analyses ont montré que l'occurrence du tassement est directement affectée par les amplitudes de déformation de cisaillement. Compte tenu de l'importance de la déformation de cisaillement, la dernière partie de cette thèse est consacrée aux caractéristiques dépendantes de la déformation des ECRD. À cette fin, des études empiriques ont été menées sur plusieurs séries chronologiques d'accélération pour les ECRD qui avaient été frappés par des tremblements de terre au Japon. Une série de graphiques et de relations a été établie pour estimer: (i) l'amplitude de la déformation de cisaillement induite; (ii) la diminution du module de cisaillement des noyaux des barrages; et (iii) augmentation des périodes fondamentales des barrages. Cette thèse fournit un assemblage approprié d'outils qui peuvent être utilisés dans la pratique de l'ingénierie, que ce soit à des fins d'analyse dynamique ou de conception. Les graphiques et les relations présentés ici sont basés sur l'examen et l'analyse de la performance réelle de nombreux barrages sous les tremblements de terre. Ils répondent non seulement aux lacunes des méthodes empiriques précédentes, mais sont également précis et efficaces. / The significant contribution of this thesis is in the area of earthquake-induced deformation of different types of rockfill dams. The permanent excess deformation at a dam's crest caused by ground-shaking will threaten the dam's safety. The characteristics of these dams and the severity of the earthquakes (quantified by intensity measures, i.e., IMs) are identified as the most critical components involved in the dam's seismic performance. In the first part, a study is performed on the seismic deformation (crest settlement) of concrete-face rockfill dams (CFRDs) and its correlation with ground motion IMs. In this way, the importance of cyclic loads' main characteristics on a numerically modelled typical CFRD case study is underlined. It is concluded that in addition to the amplitude and duration of ground motion, the dam's response is strongly affected by the frequency characteristics of the earthquake. By gathering available CFRD case histories and analyzing their seismic settlement, a new IM is proposed to efficiently describe an earthquake's potential to induce settlement in CFRDs. A new predictive relationship is then established which relates the suggested IM and earthquake magnitude with the surveyed crest settlement of the CFRD cases. In the second part, the data available for earth-core rockfill dams (ECRDs) comprising the reported settlement values and the ground motions recorded during the earthquakes are analyzed. Two novel approaches are developed by introducing two new IMs and correlating them to the observed settlement of the ECRD cases. The IMs proposed for ECRDs take into account the influence of the essential aspects regarding the nonlinear behaviour of the dams during severe earthquakes: stiffness degradation of the materials, increase in dissipated energy, and increase in the dams' periods of vibration. These issues are affected by the earthquake-induced strain, through which the correlation with a dam's deformation is discovered. The analyses showed that the occurrence of settlement is directly affected by the shear strain amplitudes. Given the importance of the shear strain, the last part of this thesis is devoted to the strain-dependent characteristics of ECRDs. To this end, empirical studies were performed on several acceleration time series for ECRDs that had been struck by earthquakes in Japan. A series of graphs and relationships were established to estimate: (i) the amplitude of the induced shear strain; (ii) the decreased shear modulus of the dams' cores; and (iii) increased fundamental periods of the dams. This thesis provides an appropriate assembly of tools that can be utilized in engineering practice, either for dynamic analysis or design purposes. The graphs and relationships presented herein are based on reviewing and analyzing the actual performance of numerous dams under earthquakes. They not only address the shortcomings of previous empirical methods, but are also accurate and efficient.

Thesis (M. Sc.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 68-70) and index.

Thesis (M. Sc.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 64-68).

Made available in DSpace on 2016-04-18T21:48:48Z (GMT). No. of bitstreams: 3 Ana Cristina Bornhausen Cardoso1.pdf: 1287212 bytes, checksum: 183f79f500ed6baa7c1d6fc34ebb9794 (MD5) Ana Cristina Bornhausen Cardoso2.pdf: 2626392 bytes, checksum: 45c3019a46a80e3612d3436dbd188369 (MD5) Ana Cristina Bornhausen Cardoso3.pdf: 1173289 bytes, checksum: 2326ed81c0f2ba258fa4acdeb84273dd (MD5) Previous issue date: 2007-08-01 / Fundo Mackenzie de Pesquisa / This dissertation has the aim to evaluate the process of charge s meaning reconstitution, considering that the semiotic studies search the signification that emerges from the texts. This analysis was based on Greimas theoretical support, focusing the generative process. However, there is a theorical argument that cannot be rejected: the text s meaning is transmitted as a total, independently of being verbal or visual. It is intended not to privilege, exclusively, the image examination, even though in determined government situation it is clear the tendency of using the visual text because it means less exposure/compromising. It was opted to make a research on the charges from the Military Dictatorship, investigating the possibility of existence of one distinguished marks. In other words, this dissertation allows us to re-read our country history and culture under a refined humour perspective. It has came to the conclusion that the ambiguity produced by the interpretation of the charges text works as true echo of voices of our time, dialoguing to other texts and translating into a poetic semiotics, as a result of the innovation presented in the expression plan. / Esta dissertação tem por finalidade avaliar os processos de (re)constituição de sentidos das charges, partindo do princípio de que os estudos semióticos se desenvolvem para depreender a significação que emerge dos textos. Há uma questão teórica de base que não pode ser desprezada: o sentido do texto é veiculado como um todo, independentemente de ser verbal ou visual. O exame do visual não foi prigilegiado, mesmo que, em determinadas situações por que passam os Governos, se verifique uma clara tendência à otimização do texto imagético, pois, em épocas de forte censura, o uso da imagem significa um menor comprometimento do chargista com a corrente ideológica do regime militar e uma forma de driblar a censura. Optou-se por fazer um estudo das charges do período de Ditadura Militar, investigando a possibilidade de existência de um traço específico nesse tipo de discurso ou, se fosse admissível, pensar-se na existência de vários modelos de charges para o período da Ditadura, o que, em última análise, permitiria (re)ler a História e a cultura do País sob a perspectiva do humor refinado. Chegou-se à conclusão de que o efeito de ambigüidade produzido pelo texto da charge pluraliza a sua interpretação, funcionando como um verdadeiro eco de vozes de seu tempo, dialogando com outros textos e traduzindo-se, em alguns casos, numa semiótica poética, dada a inovação com que se apresenta no plano da expressão.