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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Rugged Individualism in F. Scott Fitzgerald's The Great Gatsby

Jensen, Sabina January 2016 (has links)
The aim of this essay is to analyze the concept of rugged individualism in F. Scott Fitzgerald's The Great Gatsby. This paper will also examine the American Dream since rugged individualism is related to the American Dream. Marxist criticism problematizes rugged individualism and the American Dream. The title character Jay Gatsby is portrayed as an exemplary rugged individualist. Gatsby shows several traits of rugged individualism and he can be used as a representative for both rugged individualism and the American Dream.
2

A Rugged, Low-Cost, Advanced Data-Acquisition System for Field Test Projects

Simms, D. A., Cousineau, K. L. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The National Renewable Energy Laboratory (NREL) has teamed up with Zond Systems, Inc., to provide a rugged, low-cost, advanced data-acquisition system (ADAS) for use in field test projects. The ADAS simplifies the process of making accurate measurements on mechanical equipment exposed to harsh environments. It provides synchronized, time-series measurement data from multiple, independent sources. The ADAS is currently being used to acquire data from large wind turbines in operational wind-plant environments. ADAS modules are mounted on rotating blades, turbine towers, nacelles, control modules, meteorological towers, and electrical stations. The ADAS has the potential to meet the testing and monitoring needs of many other technologies as well, including vehicles, heavy equipment, piping and power transmission networks, and building energy systems.
3

DESIGN AND TESTING OF A SIMPLE OPTICAL FIBER TELEMETRY LINK FOR USE IN RUGGED ENVIRONMENTS

Bachim, Brent L. 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / The design and testing of an optical fiber telemetry link for use in rugged environments is described. Several potential applications for this cost effective telemetry link built from readily available components are given. The results of testing the simple telemetry link for vibrations up to 20g and temperatures up to 150° C are reported.
4

Crafting an outdoor classroom: the nineteenth-century roots of the outdoor education movement

Hutchinson, Paul John 08 April 2016 (has links)
This dissertation examines the antecedents to the outdoor education movement that proliferated in the first decades of the twentieth century, arguing that it stemmed from the Romanticism that emerged in the nineteenth century. Drawing on a Romantic approach to pedagogy, early outdoor educators looked to nineteenth-century literature and art as inspiration for their educational methods, curriculum and marketing. Rejecting the concepts of "rugged individualism," these outdoor educators expressed an ideal of "rugged communalism" where concepts of selflessness, community, and democracy became the lessons learned in the outdoors. The first chapter provides an overview of Puritan understanding of the wilderness and corresponding perspectives on childhood and education by drawing on the writings of John Winthrop, Cotton Mather, and Jonathan Edwards as well as John Bunyan's Pilgrim's Progress and the experience of King Philip's War. The Romantic revolution as expressed by Washington Irving, James Fenimore Cooper and others form the basis of the second chapter. Chapter three charts the transformation of American perspectives on wilderness through the visual arts and literature, specifically those writings of Ralph Waldo Emerson and Nathaniel Hawthorne combined with the work of Thomas Cole. This chapter also explores the White Mountain tourist industry as an expression of these ideals. The fourth chapter follows the changing conceptions of childhood throughout the nineteenth century with a focus on the image of the barefoot boy and street urchins. Chapter five discusses the development of a Transcendental pedagogy through the writings and educational experiments of Ralph Waldo Emerson, Bronson Alcott, Margaret Fuller, Henry David Thoreau, and Louisa May Alcott, including the impact of the Temple School and Brook Farm. The second half of the dissertation addresses specific applications of experiential outdoor pedagogy. This includes the Boston Farm School on Thompson Island, Charlesbank and the playground movement in Boston, the North Bennett Street Industrial School's outdoor programs, the relationship between the Grand Army of the Republic and the Boy Scouts of America, and the impact of Dudley Allen Sargent and Sargent Camp.
5

Analysis and Modeling of Quality Improvement on Clinical Fitness Landscapes

Manukyan, Narine 01 January 2014 (has links)
Widespread unexplained variations in clinical practices and patient outcomes, together with rapidly growing availability of data, suggest major opportunities for improving the quality of medical care. One way that healthcare practitioners try to do that is by participating in organized healthcare quality improvement collaboratives (QICs). In QICs, teams of practitioners from different hospitals exchange information on clinical practices, with the aim of improving health outcomes at their own institutions. However, what works in one hospital may not work in others with different local contexts, due to non-linear interactions among various demographics, treatments, and practices. I.e., the clinical landscape is a complex socio-technical system that is difficult to search. In this dissertation we develop methods for analysis and modeling of complex systems, and apply them to the problem of healthcare improvement. Searching clinical landscapes is a multi-objective dynamic problem, as hospitals simultaneously optimize for multiple patient outcomes. We first discuss a general method we developed for finding which changes in features may be associated with various changes in outcomes at different points in time with different delays in affect. This method correctly inferred interactions on synthetic data, however the complexity and incompleteness of the real hospital dataset available to us limited the usefulness of this approach. We then discuss an agent-based model (ABM) of QICs to show that teams comprising individuals from similar institutions outperform those from more diverse institutions, under nearly all conditions, and that this advantage increases with the complexity of the landscape and the level of noise in assessing performance. We present data from a network of real hospitals that provides encouraging evidence of a high degree of similarity in clinical practices among hospitals working together in QIC teams. Based on model outcomes, we propose a secure virtual collaboration system that would allow hospitals to efficiently identify potentially better practices in use at other institutions similar to theirs, without any institutions having to sacrifice the privacy of their own data. To model the search for quality improvement in clinical fitness landscapes, we need benchmark landscapes with tunable feature interactions. NK landscapes have been the classic benchmarks for modeling landscapes with epistatic interactions, but the ruggedness is only tunable in discrete jumps. Walsh polynomials are more finely tunable than NK landscapes, but are only defined on binary alphabets and, in general, have unknown global maximum and minimum. We define a different subset of interaction models that we dub as NM landscapes. NM landscapes are shown to have smoothly tunable ruggedness and difficulty and known location and value of global maxima. With additional constraints, we can also determine the location and value of the global minima. The proposed NM landscapes can be used with alphabets of any arity, from binary to real-valued, without changing the complexity of the landscape. NM landscapes are thus useful models for simulating clinical landscapes with binary or real decision variables and varying number of interactions. NM landscapes permit proper normalization of fitnesses so that search results can be fairly averaged over different random landscapes with the same parameters, and fairly compared between landscapes with different parameters. In future work we plan to use NM landscapes as benchmarks for testing various algorithms that can discover epistatic interactions in real world datasets.
6

WIRELESS SENSOR NETWORK PLATFORM FOR HARSH INDUSTRIAL ENVIRONMENTS

El Kouche, AHMAD 28 September 2013 (has links)
Wireless Sensor Networks (WSNs) are popular for their wide scope of application domains ranging from agricultural, medical, defense, industrial, social, mining, etc. Many of these applications are in outdoor type environments that are unregulated and unpredictable, thus, potentially hostile or physically harsh for sensors. The popularity of WSNs stems from their fundamental concept of being low cost and ultra-low power wireless devices that can monitor and report sensor readings with little user intervention, which has led to greater demand for WSN deployment in harsh industrial environments. We argue that there are a new set of architectural challenges and requirements imposed on the hardware, software, and network architecture of a wireless sensor platform to operate effectively under harsh industrial environments, which are not met by currently available WSN platforms. We propose a new sensor platform, called Sprouts. Sprouts is a readily deployable, physically rugged, volumetrically miniature, modular, network standard, plug-and-play (PnP), and easy to use sensor platform that will assist university researchers, developers, and industrial companies to evaluate WSN applications in the field, and potentially bring about new application domains that were previously difficult to accomplish using off the shelf WSN development platforms. Therefore, we addresses the inherent requirements and challenges across the hardware, software, and network layer required for designing and implementing Sprouts sensor platform for harsh industrial environments. We fully implement the hardware, network, and software architecture for the Sprouts platform and verify that they meet the requirements for harsh environments. We deploy the Sprouts platform customized with our PnP ultrasound sensor module in an industrial application to monitor the health conditions of Syncrude's vibration screens operating under extreme harsh conditions. Sprouts has been showcased in OCE Discovery 2011, and has been proven to be extremely valuable for industrial mining companies such as Syncrude. / Thesis (Ph.D, Computing) -- Queen's University, 2013-09-28 16:14:48.223
7

Development of 3D inkjet printing heads for high viscosity fluids

Van Tonder, Petrus Jacobus Malan 07 1900 (has links)
D. Tech. (Department of Electronic Engineering, Faculty of Engineering and Technology) --Vaal University of Technology / Opening up local markets for worldwide competition has led to the fundamental change in the development of new products. In order for the manufacturers to stay globally competitive, they should be able to attain and sustain themselves as ‘World Class Manufacturers’. These ‘World Class Manufacturers’ should be able to:  Deliver products in fulfilling the total satisfaction of customers.  Provide high quality products.  Offer short delivery time.  Charge reasonable cost.  Comply with all environmental concern and safety requirements. When a design is created for a new product there is great uncertainty as to whether the new design will actually do what it is desired for. New designs often have unexpected problems, hence prototypes are part of the designing process. The prototype enables the engineers and designers to explore design alternatives, test theories and confirm performance prior to standing production of new products. Additive Manufacturing (AM) technologies enable the manufacturers to produce prototypes and products which meet the requirements mentioned above. However the disadvantage of AM technologies, is that the printing material which is required is limited to that of the supplier. When uncommon printing materials must be used to manufacture a prototype or product, the 3D printing process stood out above the rest owing to its printing method. However the printing heads used in current commercially available 3D printers are limited to specific fluid properties, which limits new and unique powder binder combinations. Owing to the problem mentioned, the need arose to develop a more ‘rugged’ printing head (RPH) which will be able to print with different fluid properties. The RPH could then be used to print using unique and new powderbinder combinations. The RPH was designed and constructed using the solenoid inkjet technology as reference. In order to determine the effect which the fluid properties have on the droplet formation, fourteen different glycerol-water test solutions were prepared. The fluid properties were different for each of the glycerol-water solutions. The fluid properties included the viscosity, density and surface tension of the solution. The control parameters of the RPH were theoretically calculated for each of the glycerol-water solutions and nozzle orifice diameter sizes. The control parameters of the RPH included the critical pressure and time. Using an experimental setup, droplets ejected from the RPH could be photographed in order to be analysed. It was determined that the theoretically calculated critical times could not be used in the RPH, as the pulse widths were much lower than the recommended minimum valve pulse width of the solenoid valve used. The control parameters were then determined practically for each of the different glycerol-water solutions as well as for each nozzle orifice diameter size. The practically determined control parameters were also compared to that of the theoretically determined parameters. A mathematical model was formulated for each of the practically determined critical pressure and time parameters. Non-glycerol-water solutions were also prepared in order to determine whether the control parameters could be calculated using the practically determined mathematical models. It was found that the practically determined mathematical models, used to calculate the control parameters, could not be used with non-glycerol-water solutions. Using the practically determined mathematical models, the drop formation process of the non-glycerol-water solutions was not optimized and satellite droplets occurred. Although the practically determined models did not work for non-glycerol-water solutions, the methods used to determine the control parameters for the glycerol-water solutions could still be used to determine the practical critical pressure and time for Newtonian solutions.
8

Transistores orgânicos ultracompactos produzidos por autoenrolamento de nanomembranas / Low-voltage, flexible, and self-encapsulated ultracompact organic thin-film transistors based on nanomembranes

Torikai, Kleyton 04 December 2018 (has links)
Submitted by Kleyton Torikai (kleyton.torikai@gmail.com) on 2019-01-28T20:34:40Z No. of bitstreams: 1 kleyton_dissertacao_finalv2.pdf: 9722270 bytes, checksum: 2a886af434c5689660841438b2412e23 (MD5) / Rejected by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: 1 - Inserir logo após a folha de rosto a ficha catalográfica, pois é um ítem obrigatório. Agradecemos a compreensão on 2019-01-29T10:56:24Z (GMT) / Submitted by Kleyton Torikai (kleyton.torikai@gmail.com) on 2019-01-29T14:41:56Z No. of bitstreams: 1 kleyton_dissertacao_finalv3_submetida.pdf: 9782713 bytes, checksum: 3775eee15d15983b2b404989e8170b7b (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2019-01-30T12:02:31Z (GMT) No. of bitstreams: 1 torikai_K_me_bauru.pdf: 9782713 bytes, checksum: 3775eee15d15983b2b404989e8170b7b (MD5) / Made available in DSpace on 2019-01-30T12:02:31Z (GMT). No. of bitstreams: 1 torikai_K_me_bauru.pdf: 9782713 bytes, checksum: 3775eee15d15983b2b404989e8170b7b (MD5) Previous issue date: 2018-12-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A eletrônica orgânica mostrou-se comercialmente viável e competitiva, já sendo integrada em diversas tecnologias, e.g., displays flexíveis de OLED, painéis solares de grande área, dispositivos biocompatíveis/vestíveis, entre outras. A utilização de materiais orgânicos na fabricação de dispositivos eletrônicos explora vantagens como: flexibilidade mecânica, baixas temperaturas de processamento e possibilidade de se implementar melhorias e ajustes por meio de sínteses químicas. Entretanto, a eletrônica inorgânica já bem estabelecida ainda se destaca na área da eletrônica robusta, uma vez que os semicondutores orgânicos (OSCs) são bastante suscetíveis a condições mais extremas, como exposição a gases e radiação. Nesse sentido, a tecnologia de nanomembranas autoenroladas (NM) tem mostrado, nos últimos anos, um grande potencial na fabricação de dispositivos híbridos ultracompactos em uma arquitetura inédita para transistores orgânicos de filmes finos (OTFTs). A partir das técnicas tradicionais de microfabricação—fotolitografia, deposição de filmes finos—fabricou-se OTFTs sobre NMs que, uma vez liberadas do substrato através da remoção sistemática de uma camada de sacrifício, remodelam os dispositivos em uma arquitetura tubular tridimensional, reduzindo a área ocupada em aproximadamente 90% e protegendo os OSCs da área ativa do OTFT entre as múltiplas voltas das NMs. Assim, mostrou-se que a arquitetura confere novas propriedades aos OTFTs sem prejudicar as propriedades elétricas, suportando centenas de ciclos de compressão mecânica e mostrando-se resistentes a radiação ultravioleta e a vapores agressivos, como a amônia. Por fim, para validar a arquitetura de OTFT inédita, mostra-se que a estratégia utilizada é válida para diferentes OSCs e pode ser utilizada na fabricação de circuitos eletrônicos mais complexos a partir da associação de múltiplos dispositivos, como o inversor aqui apresentado. / In the recent years, the organic electronics’ commercial viability and competitiveness became apparent, integrating a diversity of technologies, e.g., OLED flexible displays, large-area solar panels and biocompatible and wearable devices. The manufacturing of electronic devices with organic materials aims at exploiting inherent characteristics— mechanical flexibility, low processing temperatures and the potential of boosting and tailoring specific properties through chemical synthesis. However, there’s still a gap between the well-established inorganic and the organic electronics concerning applications on rugged electronics, since the organic semiconductors (OSCs) are very susceptible to harsh conditions, e.g., exposition to UV radiation and gases. In this sense, recent advances on strained nanomembrane (NM) technology has shown enormous potential in the manufacturing of hybrid ultracompact devices in a novel organic thin-film transistor (OTFT) architecture. Through traditional microfabrication techniques—photolithography, thin-film deposition—OTFTs were fabricated on top of strained NMs, which promotes a reshaping of the devices into a 3D tubular architecture when released from the substrate. This process promotes a reduction in about 90% of the footprint area while protecting the OSC in the active area in between the multiple device windings. Therefore, the OTFTs have been endowed with new proprieties without loss of electric performance, while enduring hundreds of mechanical compression cycles and showing increased resilience against UV radiation and hazardous vapors, such as ammonia. Finally, to validate this novel OTFT architecture, this strategy has been shown to be valid for different OSCs and can be used to manufacture electronic circuits through the association of multiple devices, such as the inverter reported in this study. / CAPES: Código de financeamento 001 / FAPESP: Jovem Pesquisador 2014/25979-2
9

Hydrophobicity and Composition-Dependent Anomalies in Aqueous Binary Mixtures, along with some Contribution to Diffusion on Rugged Energy Landscape

Banerjee, Saikat January 2014 (has links) (PDF)
I started writing this thesis not only to obtain a doctoral degree, but also to compile in a particular way all the work that I have done during this time. The articles published during these years can only give a short overview of my research task. I decided to give my own perspective of the things I have learned and the results I have obtained. Some sections are directly the published articles, but some other are not and contain a significant amount of unpublished data. Even in some cases the published plots have been modified / altered to provide more insight or to maintain consistency. Historical perspectives often provide a deep understanding of the problems and have been briefly discussed in some chapters. This thesis contains theoretical and computer simulation studies to under-stand effects of spatial correlation on dynamics in several complex systems. Based on the different phenomena studied, the thesis has been divided into three major parts: I. Pair hydrophobicity, composition-dependent anomalies and structural trans-formations in aqueous binary mixtures II. Microscopic analysis of hydrophobic force law in a two dimensional (2D) water-like model system III. Diffusion of a tagged particle on a rugged energy landscape with spatial correlations The three parts have been further divided into ten chapters. In the following we provide part-wise and chapter-wise outline of the thesis. Part I consists of six chapters, where we focus on several important aqueous binary mixtures of amphiphilic molecules. To start with, Chapter 1 provides an introduction to non-ideality often encountered in aqueous binary mixtures. Here we briefly discuss the existing ideas of structural transformations associated with solvation of a foreign molecule in water, with particular emphasis on the classic “iceberg” model. Over the last decade, several investigations, especially neutron scattering and diffraction experiments, have questioned the validity of existing theories and have given rise to an alternate molecular picture involving micro aggregation of amphiphilic co-solvents in their aqueous binary mixtures. Such microheterogeneity was also supported by other experiments and simulations. In Chapter 2, we present our calculation of the separation dependence of potential of mean force (PMF) between two methane molecules in water-dimethyl sulfoxide (DMSO) mixture, using constrained molecular dynamics simulation. It helps us to understand the composition-dependence of pair hydrophobicity in this binary solvent. We find that pair hydrophobicity in the medium is surprisingly enhanced at DMSO mole fraction xDMSO ≈ 0.15, which explains several anomalous properties of this binary mixture – including the age-old mystery of DMSO being a protein stabilizer at lower concentration and protein destabilizer at higher concentration. Chapter 3 starts with discussion of non-monotonic composition dependence of several other properties in water-DMSO binary mixture, like diffusion coefficient, local composition fluctuation and fluctuations in total dipole moment of the system. All these properties exhibit weak to strong anomalies at low solute concentration. We attempt to provide a physical interpretation of such anomalies. Previous analyses often suggested occurrence of a “structural transformation” (or, microheterogeneity) in aqueous binary mixtures of amphiphilic molecules. We show that this structural transformation can be characterized and better understood under the purview of percolation theory. We define the self-aggregates of DMSO as clusters. Analysis of fractal dimension and cluster size distribution with reference to corresponding “universal” scaling exponents, combined with calculation of weight-averaged fraction of largest cluster and cluster size weight average, reveal a percolation transition of the clusters of DMSO in the anomalous concentration range. The percolation threshold appears at xDMSO ≈ 0.15. The molecular picture suggests that DMSO molecules form segregated islands or micro-aggregates at concentrations below the percolation threshold. Close to the critical concentration, DMSO molecules start forming a spanning cluster which gives rise to a bi-continuous phase (of water-rich region and DMSO-rich region) beyond the threshold of xDMSO ≈ 0.15. This percolation transition might be responsible for composition-dependent anomalies of the binary mixture in this low concentration regime. Similar phenomenon is observed for another amphiphilic molecule – ethanol, as discussed in Chapter 4. We again find composition dependent anomalies in several thermophysical properties, such as local composition fluctuation, radial distribution function of ethyl groups and self-diffusion co-efficient of ethanol. Earlier experiments often suggested distinct structural regimes in water-ethanol mixture at different concentrations. Using the statistical mechanical techniques introduced in the previous chapter, we show that ethanol clusters undergo a percolation transition in the anomalous concentration range. Despite the lack of a precise determination of the percolation threshold, estimate lies in the ethanol mole fraction range xEtOH ≈ 0.075 - 0.10. This difficulty is probably due to transient nature of the clusters (as will be discussed in Chapter 6) and finite size of the system. The scaling of ethanol cluster size distribution and the fractal behavior of ethanol clusters, however, conclusively demonstrate their “spanning” nature. To develop a unified understanding, we further study the composition-dependent anomalies and structural transformations in another amphiphilic molecule, tertiary butyl alcohol (TBA) in Chapter 5. Similar to the above-mentioned aqueous binary mixtures of DMSO and ethanol, we demonstrate here that the anomalies occur due to local structural changes involving self-aggregation of TBA molecules and percolation transition of TBA clusters at xTBA ≈ 0.05. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration ≈ 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of the largest water cluster. This second transition gives rise to another set of anomalies around. We conclude this part of the thesis with Chapter 6, where we introduce a novel method for understanding the stability of fluctuating clusters of DMSO, ethanol and TBA in their respective aqueous binary mixtures. We find that TBA clusters are the most stable, whereas ethanol clusters are the most transient among the three representative amphiphilic co-solvents. This correlates well with the amplitude of anomalies observed in these three binary mixtures. Part II deals with the topic of hydrophobic force law in water. In the introductory Chapter 7 of this part, we briefly discuss the concept of hydrophobicity which is believed to be of importance in understanding / explaining the initial processes involved in protein folding. We also discuss the experimental observations of Israelachvili (on the force between hydrophobic plates) and the empirical hydrophobic force law. We briefly touch upon the theoretical back-ground, including Lum-Chandler-Weeks theory. We conclude this chapter with a brief account of relevant and important in silico studies so far. In Chapter 8, we present our studies on Mercedes-Benz (MB) model – a two dimensional model system where circular disks interact with an anisotropic potential. This model was introduced by Ben-Naim and was later parametrized by Dill and co-workers to reproduce many of the anomalous properties of water. Using molecular dynamics simulation, we show that hydrophobic force law is indeed observed in MB model, with a correlation length of ξ=3.79. The simplicity of the model enables us to unravel the underlying physics that leads to this long range force between hydrophobic plates. In accordance with Lum-Chandler-Weeks theory, density fluctuation of MB particles (leading to cavitation) between the hydrophobic rods is clearly distinguishable – but it is not sufficiently long ranged, with density correlation extending only up to ζ=2.45. We find that relative orientation of MB molecules plays an important role in the origin of the hydrophobic force in long range. We define appropriate order parameters to capture the role of orientation, and briefly discuss a plausible approach of an orientation-dependent theory to explain this phenomenon. Part III consists of two chapters and focuses on the diffusion of a Brownian particle on a Gaussian random energy landscape. We articulate the rich history of the problem in the introductory Chapter 9. Despite broad applicability and historical importance of the problem, we have little knowledge about the effect of ruggedness on diffusion at a quantitative level. Every study seems to use the expression of Zwanzig [Proc. Natl. Acad. U.S.A, 85, 2029 (1988)] who derived the effective diffusion coefficient, Deff =D0 exp (-β2ε2 )for a Gaussian random surface with variance ε, but validity of the same has never been tested rigorously. In Chapter 10, we introduce two models of Gaussian random energy surface – a discrete lattice and a continuous field. Using computer simulation and theoretical analyses, we explore many different aspects of the diffusion process. We show that the elegant expression of Zwanzig can be reproduced ex-actly by Rosenfeld diffusion-entropy scaling relationship. Our simulations show that Zwanzig’s expression overestimates diffusion in the uncorrelated Gaussian random lattice – differing even by more than an order of magnitude at moderately high ruggedness (ε>3.0). The disparity originates from the presence of “three-site traps” (TST) on the landscape – which are formed by deep minima flanked by high barriers on either side. Using mean first passage time (MFPT) formalism, we derive an expression for the effective diffusion coefficient, Deff =D0 exp ( -β2ε2)[1 +erf (βε/2)]−1 in the presence of TSTs. This modified expression reproduces the simulation results accurately. Further, in presence of spatial correlation we derive a general expression, which reduces to Zwanzig’s form in the limit of infinite spatial correlation and to the above-mentioned equation in absence of correlation. The Gaussian random field has an inherent spatial correlation. Diffusion coefficient obtained from the Gaussian field – both by simulations and analytical methods – establish the effect of spatial correlation on random walk. We make special note of the fact that presence of TSTs at large ruggedness gives rise to an apparent breakdown of ergodicity of the type often encountered in glassy liquids. We characterize the same using non-Gaussian order parameter, and show that this “breakdown” scales with ruggedness following an asymptotic power law. We have discussed the scope of future work at the end of each chapter when-ever appropriate.

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