This research addresses the ability of dissipative passive actuators to generate control effects on a passive haptic interface. A haptic display is a human-machine interface that constructs a sensation of touch for the human operator. Applications can be found in various industries, space, medicine and construction etc. A dissipative passive haptic display contains passive actuators that can remove energy from the system by resisting motions in the system. The advantage of a dissipative passive haptic display is better safety compared to an active display. Its disadvantage is the limited control ability from the passive actuators. This research starts with the identification of the control ability and limitations of dissipative passive haptic interfaces. The ability is identified as the steerability, the ability to redirect motions of a manipulator. The force generation analysis of each individual actuator is then selected as an approach to evaluate the steerability. Steerability metrics are defined to evaluate the steerability. Even though non-redundant manipulators dont have desired steerability, optimal steering configurations are found for the best operation. Steerability is improved by redundancy in serial or parallel structures. A theorem is developed to evaluate steerability for redundant manipulators. The influence of system dynamics on their steerabilities is discussed. Previously developed haptic interfaces are evaluated based on their steerabilities. Steerability analysis of three-dimensional haptic interfaces is also given to a limited extent as an extension of the two-dimensional cases. Brakes and clutches are the two types of dissipative passive actuators in this research.

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Nowadays, volatile and complex environment has forced most organizations to operate in team-based ways to increase their flexibility and adaptability. For teams to adapt, local innovation and change, that is, self-organization, is the most critical process. However, the self-organizing process is poorly understood both in academic and practice. To deep our understanding of self-organizing teams, this research attempts to explore the self-organizing mechanism in group cognitive system perspective. One System Dynamics model is built to represent important self-organization processes. And the classical self-organizing theory-Dissipative Structure Theory is applied to guide important simulations to acquire knowledge of dynamic interactions among those processes. Several positive loops are found to be quite essential in structuring and de-structuring team¡¦s operation structure. With the knowledge of evolutionary feedback acquired, impact of critical environmental factors, such as knowledge redundancy, communication quality, and open interactions, are further investigated and experimented.

Zugl.: Freiburg (Breisgau), Univ., Diss., 2009

The current study addresses the stability of shock waves propagating through dissipative media, analogous to both granular media and molecular gases undergoing endothermic reactions. In order to investigate the stability, a simple molecular dynamics model was developed to observe shock waves and their structures with the inclusion of energy dissipation. For this, an Event Driven Molecular Dynamics model was implemented in a 2D environment, where a molecule is represented by a disk. The simulations addressed the formation of a shock wave in a gas by the sudden acceleration of a piston. Inelastic collisions were assumed to occur only if an impact velocity threshold is surpassed, representing the activation energy of the dissipative reactions. Parametric studies were conducted for this molecular model, by varying the strength of the shock wave, the activation threshold and the degree of inelasticity in the collisions. The resulting simulations showed that a shock structure does indeed become unstable with the presence of dissipative collisions. This instability manifests itself in the form of distinctive high density non-uniformities behind the shock wave, which take the form of convective rolls. The spacing and size of this ``finger-like" unstable pattern was shown to be dependent on the degree of inelasticity, the activation energy, and the strength of the driving piston. The mechanism responsible for the instability was addressed by studying the time evolution of the material undergoing the shock wave compression and further relaxation. It is found that the gas develops the instability on the same time scales as the clustering instability in homogeneous gases, first observed by Goldhirsch and Zanetti in granular gases. This confirmed that the clustering instability is the dominant mechanism.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-10T17:19:34Z No. of bitstreams: 1 MISAELLE DO NASCIMENTO OLIVEIRA - DISSERTAÇÃO PPGMAT 2015..pdf: 1209511 bytes, checksum: 5d4b2e49f1d20c974e738f463c1e1165 (MD5) / Made available in DSpace on 2018-08-10T17:19:34Z (GMT). No. of bitstreams: 1 MISAELLE DO NASCIMENTO OLIVEIRA - DISSERTAÇÃO PPGMAT 2015..pdf: 1209511 bytes, checksum: 5d4b2e49f1d20c974e738f463c1e1165 (MD5) Previous issue date: 2015-08 / Capes / O estudo do comportamento assintótico de sistemas dissipativos é um campo de pesquisa em Equações Diferenciais Parciais-EDP. Existem na literatura várias técnicas para abordar o comportamento assintótico. Contudo, o objetivo deste trabalho é aplicar a técnica devido ao resultado obtido por Gearhart (ver Z. Liu e S. Zheng [21]) que consiste em explorar as propriedades dissipativas do semigrupo associado ao sistema. / The study of the asymptotic behavior of dissipative systems is an important part of the research of Partial Di erential Equations-PDE. Consequently, there are various methods to analize this one. The objective of this work is to apply the a result due to Gearhart (see Z. and S. Liu Zheng [21]) which consits in to explore the dissipation properties of the semigroups associated to dissipative systems.

xiv, 144 leaves : ill. A print copy of this title is available through the UO Libraries under this call number: SCIENCE QH541.5.S35 M37 2007

This thesis addresses the sampling problem in a high-dimensional space, i.e., the computation of averages with respect to a defined probability density that is a function of many variables. Such sampling problems arise in many application areas, including molecular dynamics, multiscale models, and Bayesian sampling techniques used in emerging machine learning applications. Of particular interest are thermostat techniques, in the setting of a stochastic-dynamical system, that preserve the canonical Gibbs ensemble defined by an exponentiated energy function. In this thesis we explore theory, algorithms, and numerous applications in this setting. We begin by comparing numerical methods for particle-based models. The class of methods considered includes dissipative particle dynamics (DPD) as well as a newly proposed stochastic pairwise Nosé-Hoover-Langevin (PNHL) method. Splitting methods are developed and studied in terms of their thermodynamic accuracy, two-point correlation functions, and convergence. When computational efficiency is measured by the ratio of thermodynamic accuracy to CPU time, we report significant advantages in simulation for the PNHL method compared to popular alternative schemes in the low-friction regime, without degradation of convergence rate. We propose a pairwise adaptive Langevin (PAdL) thermostat that fully captures the dynamics of DPD and thus can be directly applied in the setting of momentum-conserving simulation. These methods are potentially valuable for nonequilibrium simulation of physical systems. We again report substantial improvements in both equilibrium and nonequilibrium simulations compared to popular schemes in the literature. We also discuss the proper treatment of the Lees-Edwards boundary conditions, an essential part of modelling shear flow. We also study numerical methods for sampling probability measures in high dimension where the underlying model is only approximately identified with a gradient system. These methods are important in multiscale modelling and in the design of new machine learning algorithms for inference and parameterization for large datasets, challenges which are increasingly important in "big data" applications. In addition to providing a more comprehensive discussion of the foundations of these methods, we propose a new numerical method for the adaptive Langevin/stochastic gradient Nosé-Hoover thermostat that achieves a dramatic improvement in numerical efficiency over the most popular stochastic gradient methods reported in the literature. We demonstrate that the newly established method inherits a superconvergence property (fourth order convergence to the invariant measure for configurational quantities) recently demonstrated in the setting of Langevin dynamics. Furthermore, we propose a covariance-controlled adaptive Langevin (CCAdL) thermostat that can effectively dissipate parameter-dependent noise while maintaining a desired target distribution. The proposed method achieves a substantial speedup over popular alternative schemes for large-scale machine learning applications.

Submitted by Liliane Ferreira (ljuvencia30@gmail.com) on 2018-04-25T14:22:37Z No. of bitstreams: 2 Dissertação - André Vinícius Freire Baleeiro - 2018.pdf: 3591684 bytes, checksum: aefaee47a62e78df179a8ef1086b815d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-04-26T11:03:11Z (GMT) No. of bitstreams: 2 Dissertação - André Vinícius Freire Baleeiro - 2018.pdf: 3591684 bytes, checksum: aefaee47a62e78df179a8ef1086b815d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-04-26T11:03:11Z (GMT). No. of bitstreams: 2 Dissertação - André Vinícius Freire Baleeiro - 2018.pdf: 3591684 bytes, checksum: aefaee47a62e78df179a8ef1086b815d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Syntropic Farming is a type of agriculture that combines practices and principles that reconcile agricultural production and regeneration of forests. Some experiences and publications have tested its agronomic and economic viability besides its environmental benefits, but a very few have approached the theoretical basis that made Ernst Götsch choose the term syntropy (a complementary opposite to entropy) to name this agriculture. This dissertation reviews the scientific literature that addresses the issues raised by the creation of the term "entropy" and the consequences of the Second Law of Thermodynamics. In addition, I analyze the intersection area of Thermodynamics and Ecology, demonstrating the difficulties and potentialities of this interdisciplinary area. Finally, I highlight the coherences between Syntropic Farming and the scientific literature, some methods are pointed out due to their consonance and a hypothesis is launched to test the theoretical propositions of this agriculture. / A Agricultura Sintrópica é uma tipo de agricultura recente que reúne práticas e princípios que conciliam a produção agrícola e a regeneração das florestas. Alguns trabalhos e experiências têm demonstrado sua viabilidade Agronômica e Econômica além dos benefícios ambientais, mas poucos se aprofundaram no embasamento teórico que levou Ernst Götsch a escolher o termo sintropia (um oposto complementar à entropia) para denominar essa agricultura. Este trabalho revisa a literatura científica que aborda as questões levantadas pela criação do termo “entropia” e as consequências da Segunda Lei da Termodinâmica. Além disso, ele analisa a área de intersecção da Termodinâmica com a Ecologia, demonstrando as limitações e potencialidades desta área interdisciplinar. Por fim, as coerências entre a Agricultura Sintrópica e a literatura acadêmica Termodinâmica-Ecológica são ressaltadas, alguns métodos são apontados e uma hipótese é lançada para testar as proposições desta agricultura.

Apresentamos um estudo sobre o fenômeno da decoerência durante a evolução temporal de um estado atômico ao interagir com o campo eletromagnético de uma cavidade não ideal. Apresentamos um modelo em que o campo da cavidade esta acoplado a um banho externo e mostramos os efeitos dissipativos que este acoplamento pode gerar na decoerência para um sistema átomo campo. Discutimos as grandezas relevantes para analise da decoerência através de modelos analíticos e numéricos, principalmente entre os acoplamentos átomo campo e campo banho. Sugerimos que o retardamento observado no processo de decoerência seja uma característica geral em sistemas analisáveis como constituídos de três subsistemas acoplados sequencialmente, com propriedades espectrais e acoplamentos suficientemente assimétricos. / We present a study of the phenomenon of decoherence in the time evolution of an atomic state with the electromagnetic field of a non-ideal cavity. We present a model where the cavity field is coupled to an external bath and show the dissipative effects this coupling can generate in the decoherence of the atom field system. We discuss the relevant variables for the analysis of decoherence in terms of analytic and numerical models, especially the atom-field and field-bath couplings. We suggest that the observed hindrance of the decoherence process may be a general property in systems which can be considered as formed by three subsystems coupled sequentially, with spectral properties and sufficiently asymmetric coupling.