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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.
371

Inelastic collision and three-body recombination

Li, Bo 19 May 2009 (has links)
The quantum impulse approximation theory has been extended to the inelastic collision. The total inelastic cross sections for the degenerated states with different angular momenta was calculated. It was proved that summing over the transitions from nl to n' and from nl to n'l' would give us the total cross section of transition from n to n'. Rate coefficients were calculated for the common gases in the atmosphere being the third particle. The resonant effect of the rate coefficients had been observed. Recombination coefficients were then calculated in terms of rate coefficients. Previous calculations were carried out in compare with the net rate flow through certain excited levels, which were found to be more stable and reflected a clearer picture of the whole process. Results have been compared with the elastic collision. A dramatic decreasing of rates when temperature increased was also observed. More thermal energy increases the probability of electrons for being re-ionized. Similar calculations had been carried out for the upper atmosphere gases, such as N₂, O₂, CO, CO₂, and H₂O. The recombination coefficients for electron combining with metallic ion Na+ were also calculated.
372

Of Malicious Motes and Suspicious Sensors

Gilbert, Seth, Guerraoui, Rachid, Newport, Calvin 19 April 2006 (has links)
How much damage can a malicious tiny device cause in a single-hopwireless network? Imagine two players, Alice and Bob, who want toexchange information. Collin, a malicious adversary, wants to preventthem from communicating. By broadcasting at the same time as Alice orBob, Collin can destroy their messages or overwhelm them with his ownmalicious data. Being a tiny device, however, Collin can onlybroadcast up to B times. Given that Alice and Bob do not knowB, and cannot distinguish honest from malicious messages, howlong can Collin prevent them from communicating? We show the answerto be 2B + Theta(lg|V|) communication rounds, where V is theset of values that Alice and Bob may transmit. We prove this resultto be optimal by deriving an algorithm that matches our lowerbound---even in the stronger case where Alice and Bob do not start thegame at the same time.We then argue that this specific 3-player game captures the generalextent to which a malicious adversary can disrupt coordination in asingle-hop wireless network. We support this claim by deriving---via reduction from the 3-player game---round complexity lower boundsfor several classical n-player problems: 2B + Theta(lg|V|) for reliable broadcast,2B + Omega(lg(n/k)) for leader election among k contenders,and 2B + Omega(k*lg(|V|/k)) for static k-selection. We then consider an extension of our adversary model that also includes up to t crash failures. We study binary consensus as the archetypal problem for this environment and show a bound of 2B + Theta(t) rounds. We conclude by providing tight, or nearly tight, upper bounds for all four problems. The new upper and lower bounds in this paper represent the first such results for a wireless network in which the adversary has the ability to disrupt communication.
373

Applications of ion mobility spectrometry, collision-induced dissociation and electron activated dissociation tandem mass spectrometry to structural analysis of proteins, glycoproteins and glycans

Pu, Yi 09 November 2016 (has links)
This dissertation mainly focuses on analytical method development for characterization of proteins, glycoproteins and glycans using the recently developed ion mobility spectrometry (IMS) techniques and various electron activated dissociation (ExD) tandem mass spectrometry methods. IMS and ExD have become important techniques in structure analysis of biomolecules. IMS is a gas-phase separation method orthogonal to liquid chromatography (LC) fractionation. ExD is capable of producing a large number of structurally informative fragment ions for elucidation of structural details, complementary to collision-induced dissociation (CID). We first applied the selected accumulation-trapped IMS (SA-TIMS)-electronic excitation dissociation (EED) method to analyze various mixtures of glycan isomers. Glycan linkage isomers with linear or branched structure were successfully separated and subsequently identified. Theoretical modeling was also performed to gain a better understanding of isomer separation. The calculated collisional cross section (CCS) values match well with the experimentally measured ones, and suggested that the choice of metal charge carrier and charge state is critical for successful IMS separation of isomeric glycans. In addition, a SA-TIMS-electron capture dissociation (ECD) approach was employed to study gas-phase protein conformation, as the ECD fragmentation pattern is influenced by both the charge distribution and the presence of various non-covalent interactions. We demonstrated that different conformations of protein ions in a single charge state could produce distinct fragmentation pattern, presumably because of their differences in tertiary structures and/or proton locations. The second part describes characterization of glycoproteins using LC-hot ECD. To improve the cleavage coverage of glycopeptides, hot ECD, a fragmentation method utilizing the irradiation of high-energy electrons, was optimized for both middle-down and bottom-up analyses of glycopeptides, including peptides with multiple glycosylation sites. Hot ECD was shown to be an effective fragmentation technique for sequencing of glycopeptides, even for ions in lower charge states. In addition, the online LC-hot ECD approach was applied to characterize extensively modified glycoproteins from biological sources in which all glycosylation sites could be unambiguously determined. This study expands the applications of IMS, CID and ExD to structural analysis of various biomolecules, and explores the analytical potential of combining them for investigation of complex biological systems, in particular, enzyme mechanisms.
374

A intermediação da noção de probabilidade na construção de conceitos relacionados à cinética química no ensino médio /

Cirino, Marcelo Maia. January 2007 (has links)
Orientador: Aguinaldo Robinson de Souza / Banca: Ourides Santim Filho / Banca: Marcelo Carbone Carneiro / Resumo: Este trabalho procurou identificar como estudantes do Ensino Médio se apropriam de conceitos e elaboram determinados modelos inseridos em Cinética Química, especificamente o modelo cinético de colisão de partículas numa reação (Teoria das Colisões). Esta análise e as reflexõe que a seguiram foram baseadas principalmente nos estudos realizados por Piaget (1975, 1975b, 1977), Piaget & Inhelder (1975, 1977), Jun (2000) e Fischbein (1975). Utilizamos como documentos as transcrições das entrevistas (pré e pós-testes) realizadas individualmente com cada aluno. Inicialmente os estudantes foram entrevistados (pré-testes) com o intuito de identificar a familiaridade com a noção de evento probabilístico ou aleatório. Numa segunda etapa (pós-testes) esse conhecimento (ou a ausência parcial/total dele) foi posto à prova numa tentativa de estabelecer relações com um conteúdo específico da Química (Teoria das Colisões). Os resultados obtidos apontam para grandes discrepâncias entre o modelo cinético de colisões elaborado pelos estudantes e o cientificamente aceito. / Abstract: The purpose of this work is to contribute for Science teaching making analysis and reflections on the way high school students appropriate the concepts and models related to Chemical Kinetics, mainly particles collisions' kinetics model in chemical reaction (Collision Theory Model). This investigation was based on Piaget and Inhelder' studies (1975), and also on Piaget (1975, 1977), Jun (2000), and Fischbein (1975) works, which have studied the connection between the young students and the probabilistic thinking. The analysis of the document evidences had the aim to evaluate if the students would be able to achieve generalization and develop concepts about Probability Theory. In the second part these concepts or its partial/total lacks were linked with chemical kinetics in attempt to establish relationships between correct explanation of collision kinetic model and the students' failure models. The obtained result points to great misconceptions related to the correct and scientific model and the student's. / Mestre
375

AUGMENTED REALITY SOM DIGITALT VERKTYG I PRODUKTIONSSKEDET / Augmented reality as a digital tool in the production phase

Jimenez Parra, Jefferson, Radulovic, Milan January 2018 (has links)
Detta examensarbete utreder augmented reality (AR) som digitalt verktyg i byggproduktionen. Byggproduktionen präglas av kollisionsproblem och bakgrunden till dessa problem ligger ofta i bristande kommunikation och bristande samordning i byggprojekten. Installationsarbeten tar mer än 50% av produktionstiden och kräver mycket kommunikation och samordning. Installationsarbeten utförs ofta på begränsade arbetsytor och med en dålig samordning mellan de inblandade yrkesgrupperna bidrar detta till att det uppstår kollisioner och farliga arbetssituationer. Skanska vill effektivisera deras arbetsproccess genom nya teknologier och har därmed valt att testa Microsoft Hololens som använder teknologin AR i sina byggprojekt. Målet med arbetet är att undersöka genom en fallstudie om AR är lämpligt att användas i byggproduktionen genom att besvara (1) Hur lämplig är AR för informationsöverföringen och hantering i byggproduktionen? (2) Hur noggrann är AR teknologin för att kunna användas i installationsarbeten? (3)Vilka möjlighter har AR att implementeras i Skanskas verksamhet? Studien innefattar en fallstudie med observationer och intervjuer på ett av Skanskas byggprojekt i Göteborg, Tändstickan 3. Arbetarna får använda Microsoft Hololens som ett arbetsverktyg medan författarna observerar deras arbete. Intervjuer utförs före och efter användnigen av Microsoft Hololens. En dokumentanalys och litteraturstudie kommer att utföras för att bekräfta eller motsäga resultatet. Arbetarna som ingår i observationerna intervjuas efter användningen av Microsoft Hololens för att kontrollera om AR är lämpligt för deras arbete. Resultatet från intervjuerna och observationerna visar att AR kan minimera kollisionerna och effektivisera arbetet. Jämförelsen av resultaten från intervjuerna av AR specialister, arbetsledare, installationsledare, platschef och montörer visar att teknologin har potentialen att implementeras i Skanskas verksamhet. Svårigheten ligger i användarvänligheten och om hårdvaran är lämplig att användas på en arbetsplats. Studien utfördes under ett pågående projekt där installationsarbeten var i slutskedet, vilket påverkar studiens resultat. Det arbeten som medför mest svårigheter var redan avklarade vilket minskar resultatens giltighet. Studien utfördes i samarbeten med Skanska vilket gör det svårt att generallisera med mindre företag eftersom de inte har lika mycket resurser.
376

Considerações sobre a dinâmica veicular visando acidentes veiculares / Analyze and modeling of vehicular dynamic aplies in the accident reconstruction

Peruzzo, Régis Aurélio January 2010 (has links)
A reconstrução de acidentes se faz necessário sempre que não houver um consenso entre as partes envolvidas no evento. A maior ou menor complexidade do trabalho de reconstrução dependerá da quantidade de informações registradas, da qualidade dessas informações e do tipo de acidente com o envolvimento de vítimas fatais ou não. Para facilitar o desenvolvimento do trabalho de reconstrução as informações registradas devem ter fidelidade para auxiliar no esclarecimento das etapas do evento. Neste trabalho busca-se, partindo das informações registradas sobre um acidente veicular, verificar a possibilidade da sua reconstrução a partir dessas informações. A metodologia escolhida para alcançar o objetivo do trabalho esta centrada na revisão da teoria da dinâmica veicular, abordando os tópicos da aceleração, sistema de freios e sistema de direção. São feitas simplificações no equacionamento em termos das forças aerodinâmicas por não se estar analisando o desempenho do veículo e pelo fato dessas forças não interferirem no resultado do evento. Simplificações quanto o comportamento dos pneus que ocorrem na interface via-pneu e a própria deformação da camada de borracha foram desprezadas pelo fato desses estarem derrapando sobre a via, mantendo um comportamento de deslizamento. A rolagem também sofre simplificações seguindo o mesmo raciocínio. Para verificar os resultados da abordagem teórica e os resultados constantes no registro faz-se uso de programas computacionais para confirmar ou não esses resultados. O conjunto de soluções analíticas com soluções obtidas com programas de simulação permite obter resultados que reproduzem com relativa precisão o acidente veicular, dependendo da qualidade das informações disponíveis. Os resultados obtidos desse desenvolvimento, traduzido em vídeos, imagens e gráficos, confirmam algumas informações do registro e se contrapõem em outros. / The accident reconstruction will be necessary always that there isn’t agreement between of both parts. The major or minor problems work of reconstruction will depends of the quantity of information registered, of the quality this information and of kind accident with involvement of fatal victims or no. To facility the discovery of knowledge event dynamic of a collision clear the real sequence of this event. In this work get the intention reconstructs an accident starting of registered information and concludes if these information are sufficient for realizer the accident reconstruction. The methodology used to make this work and the objectives is centered in the revision the topics how acceleration, brake system and steering wheel system. Are make simplification about of the aerodynamic forces because the focus not is study the behavior of vehicle. The type of fragment bon, the injuries more common to the occupants of vehicle and to the pedestrian, as well as know the vehicle deformation mechanism. The environment of specific programs to accident reconstruction and determinate the trajectory of vehicles appears with the base to confirm and certify the information related in the officials documents. Moreover the creation multibody dynamics simulation programs have been used to modeling the movement of human body during the collision. Furthermore environment the best external form that vehicle must have to cause minor injuries in the pedestrian. Know the elements that do this universe, identify how the vehicles response about the characteristics constructive road. The pedestrian, passenger and driver too are paces this universe and identify yours behavior is very important. Using the all theory developed until today to know the dynamic vehicle, analyze and simulate by means of specific programs to reconstruction accidents is the main this work.
377

Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms / Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms

Dutra, Teófilo Bezerra January 2015 (has links)
DUTRA, Teófilo Bezerra. Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms. 2015. 122 f. Tese (Doutorado em Ciência da Computação)-Universidade Federal do Ceará, Fortaleza, 2015. / Submitted by Vitor Campos (vitband@gmail.com) on 2016-09-28T21:38:15Z No. of bitstreams: 1 2015_tese_tfdutra.pdf: 18611468 bytes, checksum: efc5f80ee6b8df68191af2bca394a07a (MD5) / Approved for entry into archive by Jairo Viana (jairo@ufc.br) on 2016-09-28T22:54:58Z (GMT) No. of bitstreams: 1 2015_tese_tfdutra.pdf: 18611468 bytes, checksum: efc5f80ee6b8df68191af2bca394a07a (MD5) / Made available in DSpace on 2016-09-28T22:54:58Z (GMT). No. of bitstreams: 1 2015_tese_tfdutra.pdf: 18611468 bytes, checksum: efc5f80ee6b8df68191af2bca394a07a (MD5) Previous issue date: 2015 / Most recent crowd simulation algorithms equip agents with a synthetic vision component for steering. They offer promising perspectives by more realistically imitating the way humans navigate according to what they perceive of their environment. In this thesis, it is proposed a new perception/motion loop to steer agents along collision free trajectories that significantly improves the quality of vision-based crowd simulators. In contrast with previous solutions - which make agents avoid collisions in a purely reactive way - it is suggested exploring the full range of possible adaptations and to retain the locally optimal one. To this end, it is introduced a cost function, based on perceptual variables, which estimates an agent’s situation considering both the risks of future collision and a desired destination. It is then computed the partial derivatives of that function with respect to all possible motion adaptations. The agent adapts its motion to follow the steepest gradient. This thesis has thus two main contributions: the definition of a general purpose control scheme for steering synthetic vision-based agents; and the proposition of cost functions for evaluating the dangerousness of the current situation. Improvements are demonstrated in several cases. / Alguns dos algoritmos mais recentes para simulação de multidão equipam agentes com um sistema visual sintético para auxiliá-los em sua locomoção. Eles oferecem perspectivas promissoras ao imitarem de forma mais realista a forma como os humanos navegam de acordo com o que eles percebem do seu ambiente. Nesta tese, é proposto um novo laço de percepção/ação para dirigir agentes ao longo de trajetórias livres de colisões que melhoram significativamente a qualidade dos simuladores de multidão baseados em visão. Em contraste com abordagens anteriores - que fazem agentes evitarem colisões de maneira puramente reativa - é sugerida a exploração de toda gama de adaptações possíveis e a retenção da que for ótima localmente. Para isto, é introduzida uma função de custo, baseada em variáveis de percepção, que estima a situação atual do agente considerando tanto os riscos de futuras colisões como o destino desejado. São então computadas as derivadas parciais dessa função com respeito a todas adaptações de movimento possíveis. O agente adapta seu movimento de forma a seguir o gradiente descendente. Esta tese possui assim duas principais contribuições: a definição de um esquema de controle de propósito geral para a orientação de agentes baseados em visão sintética; e a proposição de funções de custo para avaliar o perigo da situação atual. As melhorias obtidas com o modelo são demonstradas em diversos casos.
378

A igualdade e a proteção ao trabalhador hipossuficiente sob a égide da proporcionalidade

Santos, Dartagnan Ferrer dos January 2011 (has links)
Esta dissertação analisa a relação entre os princípios da isonomia e da proteção ao trabalhador, examinando como ambos atuam para efetivar ou não a igualdade material entre empregador e empregado. Parte-se de uma contextualização histórica e científica do debate. A seguir será estudado o conceito de princípio do direito, analisando-se três deles: a igualdade, a proporcionalidade e a proteção ao trabalhador. Então, será averiguado se a isonomia e a norma protetora são complementares ou contraditórias, bem como a possível existência de um quantum justo de tutela a se conferir ao ―hipossuficiente‖ em cada caso concreto, procedimento esse que teria como fim igualar os polos da relação laboral – acaso não seja assim, a proteção a ser concedida será invariável. A metodologia usada será a pesquisa bibliográfica e, eventualmente, jurisprudencial, com um enfoque primordialmente dogmático, mas também zetético e interdisciplinar. Para o exame dessas questões – bem como para respondê-las -, seguir-se-á principalmente os chamados ―neoconstitucionalismo‖ e o ―pós-positivismo‖ naquela vertente liderada por Robert Alexy. Ao final, serão apresentadas conclusões no sentido de ser ou não possíveis a adoção do princípio da proporcionalidade para ponderar igualdade e proteção ao trabalhador, equiparando-se assim as partes em justa medida na busca pela Justiça. / This study analyses the relationship between the principles of legal equality and worker protection, examining how both operate to effect or otherwise the material equality between employer and employee. It starts from an historical and scientific contextualization of the debate and then moves on to study the concept of the principles of law, analyzing three of them: equality, proportionality and worker protection. Then it will examine whether equality under the law and protection regulations are complementary or contradictory, together with the possible existence of fair portion of protection which would provide the ―disadvantaged ― in each case with a procedure aimed at equalizing the opposing positions in the labour relationship - otherwise, it would be an unvarying protection. The method will employ bibliographical and juridical research, which is primarily focused on the strictly legal, but is also zetetic and interdisciplinary. Examination of these questions, together with responses to them, will principally follow the ―neo-constitutionalism‖ and ―post-positivism‖ of the approach propounded by Robert Alexy. Finally, it will present conclusions about whether or not it is possible to adopt the principle of proportionality in consideration of worker protection and equality, thus equalizing the parties in the fair pursuit of justice.
379

Robotic Offline Path Planning

Kamkarian, Pejman 01 December 2015 (has links)
The aim of this study is to disseminate a novel path planner which is particularly used for offline robots to build more efficient collision-free trajectories in terms of the length in more skilled fashion. Robotic path planning as one of the most important problems has been under investigation by a variety of researchers within the last few decades. Path planner refers to a unit which is responsible to perform a series of operations on the robots’ environment with the sole purpose of building proper trajectories from a start point to the goal configuration. A robot’s planner generally consists of some or all of the following units: analyzing the workspace, mapping the workspace into an alternative methodology such as a graph, optimizing the constructed map, and calculating and refining the desired trajectory. Various path planners have been proposed based on the different robots’ functionalities as well as the environmental specifications. A path planner basically uses a methodology inspiring a scientific theory or event to build optimal paths. This research tends to propose a novel path planner which is able to be successfully applied on a variety of workspaces with different constraints. Moreover, the presented planner successfully builds the shortest collision-free trajectories from an initial to the goal configurations. In addition, compared to the other majority of path planners, the illustrated path planner uses less environmental global information to build optimal paths. This leads the planner unit to allocate less of system resources such as memory, hence, increasing the performance of the planner in terms of preserving more system resources.
380

Thermophoresis in colloidal suspensions

Burelbach, Jérôme January 2018 (has links)
This dissertation examines the motion of colloids in a temperature gradient, a non-equilibrium phenomenon also known as thermophoresis. Chapter 1 gives an introduction to the existing applications and basic concepts of thermophoresis and outlines some of the experimental and theoretical challenges that serve as a motivation for this PhD project. In Chapter 2, a general theoretical description for thermophoresis is formulated using the theory of non-equilibrium thermodynamics. The colloidal flux is split up into an interfacial single-colloid contribution and a bulk contribution, followed by a determination of transport coefficients based on Onsager’s reciprocal relations. It is further shown how the phenomenological expression of the thermophoretic flux can be recovered when the fluid is at steady-state. The results issuing from this description are then discussed and compared to other existing approaches, some of which are shown to neglect the hydrodynamic character of colloidal thermophoresis. Chapter 3 is dedicated to the validation of the introduced theoretical framework by means of computer simulations, using a simulation technique known as multi-particle collision dynamics. More specifically, the dependence of the thermophoretic force on different system parameters is examined and deviations from the theoretical prediction are explained by an advective distortion of interfacial fluid properties at the colloidal surface. Chapter 4 presents steady-state measurements of functionalised colloids in a temperature gradient, showing how the addition of molecular surface groups increases the experimental complexity of thermophoretic motion. The relaxation process behind this steady-state is also studied, to determine how the relaxation speed depends on the applied temperature gradient. In chapter 5, a general conclusion is drawn from the presented work and its implications are briefly discussed in relation to the current state of knowledge. Finally, the discussion is closed with an outlook on remaining challenges in understanding colloidal motion that could be the subject of future research.

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