Dissertations / Theses on the topic 'Physical Context Modeling'
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Sjöstedt, Carl-Johan. "Modeling and Simulation of Physical Systems in a Mechatronic Context." Doctoral thesis, KTH, Maskinkonstruktion (Avd.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10522.
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This thesis gives different views on the modeling and simulation of physical systems, especially together with embedded systems, forming mechatronic systems. The main considered application domain is automotive. One motivation behind the work is to find suitable representations of physical systems to be used in an architectural description language for automotive embedded systems, EAST-ADL2, which is implemented as a UML2 profile, and uses concepts from both UML and SysML. As a part of the thesis, several languages and tools are investigated, including bond graphs, MATLAB/Simulink, Ptolemy II, Modelica, MATLAB/Simscape and SysML. For SysML, the modeling of continuous-time systems and how it relates to MATLAB/Simulink and Modelica is evaluated. A case study of an electric power assisted steering is modeled to show the differences, the similarities and the usage of the above mentioned languages and tools. To be able to classify the tools and languages, five realization levels were developed: Physical modeling models Constraint models Continuous causal models Discretized models Discretized models with solver and platform implementation By using these realization levels, models, tools and modeling languages can be classified, and transformations between them can be set up and analyzed. As a result, a method to describe the simulation behavior of a MATLAB/Simulink model has been developed using SysML activity diagrams as an approach to achieve integrated system models. Another result is an evaluation of the parametric diagrams of SysML for continuous-time modeling, which shows that they do not enable “physical modeling”, i.e. modeling the topology of the system and getting the underlying equations out of this topology. By including physical ports and physical connectors to SysML internal block diagrams, this could be solved. The comparison also shows many similarities between the languages. The results led to a more detailed investigation on conjugate variables, such as force and velocity, and electric current and voltage, and how these are treated in various languages. The thesis also includes two industrial case studies: one of a twin-screw compressor, and one of a simulation environment for automotive fuel-cell systems. Conclusions are drawn from these models, referring to the realization levels.QC 20100810
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Sjöstedt, Carl-Johan. "Modeling and simulation of physical systems in a mechatronic context /." Stockholm : Skolan för indutstriell teknik och managemnet, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10522.
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Gopalkrishnan, Purnima. "Abusive Supervision and Group-Level Perceptions: Looking at the Social Context of Abuse in the Workplace." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1356791768.
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Badawi, Hawazin Faiz. "DT-DNA: Devising a DNA Paradigm for Modeling Health Digital Twins." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41906.
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The potential of Digital twin (DT) technology outside of the industrial field has been recognized by researchers who have promoted the vision of applying DTs technology beyond manufacturing, to purposes such as enhancing human well-being and improving quality of life (QoL). The expanded definition of DTs to incorporate living and nonliving physical entities into the definition of DTs was a key motivation behind the model introduced in this thesis for building health digital twins of citizens. In contrast with DTs that have been developed in more industrial fields, this type of digital twins modeling necessitates protecting each citizen's unique identity while also representing features common to all citizens in a unified way. In nature, DNA is an example of a model that is both unified, common to all humans, and unique, distinguishing each human as an individual. DNA’s architecture is what inspired us to propose a digital twin DNA (DT-DNA) model as the basis for building health DTs for citizens. A review of the literature shows that no unified model for citizens’ health has been developed that can act as a base for building digital twins of citizens while also protecting their unique identity thus we aim to fill this gap in this research. Accordingly, in this thesis, we proposed a DT-DNA model, which is specifically designed to protect the unique identity of each citizen’s digital twin, similar to what DNA does for each human. We also proposed a DT-DNA-based framework to build standardized health digital twins of citizens on micro, meso and macro levels using two ISO standards: ISO/IEEE 11073 (X73) and ISO 37120. To achieve our goal, we started by analyzing the biological DNA model and the influencing factors shaping health in smart cities. The purpose of the first is to highlight the DNA model features which provide the building blocks for our DT-DNA model. The purpose of the latter is to determine the main bases of our DT-DNA model of health DTs. Based on the analysis results; we proposed DT-DNA to model health DTs for citizens. In keeping with our DNA analogy, we have identified four bases, A, T, G, and C, for our unified and unique DT-DNA model. The A base in the proposed model represents a citizen’s anthropometric when we build the DT-DNA on an individual level and represents the city’s regulatory authorities when we build the DT-DNA on community and city levels. The T base represents different tasks included in the provided health data that are required to model citizens’ health DT-DNA on different levels. The G base represents the geographic and temporal information of the city, where the citizen exists at the time of data collection. The C base represents the context at the time of data collection. To proof the concept, we present our initial work on building health DTs for citizens in four case studies. The first two case studies are dedicated for health DTs at the micro level, the third case study is dedicated for health DTs at the meso level and the fourth case study is dedicated for health DTs at the macro level. In addition, we developed an algorithm to compare cities in terms of their community fitness and health services status. The four case studies provide promising results in terms of applicability of the proposed DT-DNA model and framework in handling the health data of citizens, communities and cities, collected through various sources, and presenting them in a standardized, unique model.
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Southey, Philip. ""Concept" and "Context": Toward modelling understanding in Physics Education research." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27857.
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"Context sensitivity" is a core issue in physics education research (PER). Why does student understanding of a concept depend so crucially on the context in which it is embedded? This dissertation attempts to answer this question by using a variety of theoretical tools to model understanding. We conducted three empirical studies which probed context sensitivity of student understanding of (i) Vector Addition; (ii) The FCI (Force Concept Inventory); and (iii) the learning of the concept of a Mathematical Group. (i) Regarding vector addition, we discovered context sensitivities involving the type of physical quantity added (e.g. force or momentum); the textual prompts "total", "net" and "resultant"; and the object on which a force acts. (ii) In the FCI, we discovered a moderate context sensitivity to unfamiliar words (i.e. when familiar words like "box" were substituted for unfamiliar words like "kist".) This sensitivity was moderately correlated with the difficulty of the question. (iii) Previous studies have shown that learners exhibit a sensitivity to the concreteness of the learning condition of a Mathematical Group; our study shows that students are engaged in different types of activity in these conditions. A variety of theoretical tools from PER, Cognitive Linguistics, Cognitive Psychology and other areas of Education Research are used to model student understanding in these various studies. Three key insights emerged. (a) The importance of one's model of "concept" - how it relates to the notion of "context", and how one chooses an appropriate grain size. (b) The difference between "expert" and "novice" - how this difference influences one's model of "concept", and how it influences one's notion of "sameness" and "difference". (c) Student reasoning - how a framing of a situation might result in fast, associative, linguistic reasoning on the one hand, or slow, deliberate simulative reasoning on the other. Finally, this thesis is grounded in Wittgensteinian ordinary language philosophy which maintains that notions of "concept", "context" and "understanding" obtain meaning not be referring to some transcendental "thing", but by being embedded in our messy form of life. In other words, by modelling understanding we are not approaching the "true meaning" of the term. Instead we are demonstrating how our various models are constitutive of what we mean when we say: "My students understand this concept".
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Dietz, Laura Elizabeth. "Effect of the Science Teaching Advancement through Modeling Physical Science Professional Development Workshop on Teachers' Attitudes, Beliefs and Content Knowledge and Students' Content Knowledge." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1404125737.
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Chaves, Café Daniel. "Multi-level modeling for verification and synthesis of complex systems in a multi-physics context." Thesis, CentraleSupélec, 2015. http://www.theses.fr/2015SUPL0019/document.
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À l'ère de systèmes électroniques intégrés, les ingénieurs font face au défi de concevoir et de tester des systèmes hétérogènes contenant des parties analogiques, numériques, mécaniques et même du logiciel embarqué. Cela reste très difficile car il n'y a pas d'outil unifiant ces différents domaines de l’ingénierie. Ces systèmes, dits hétérogènes, ont leur comportement exprimées et spécifiés par plusieurs formalismes, chacun particulier à son domaine d'expertise (diagramme de machines à état pour les circuits de contrôle numérique, équations différentielles pour les modèles mécaniques, ou bien des réseaux de composants pour les circuits analogiques). Les outils de conception existants sont destinés à traiter des systèmes homogènes en utilisant un seul formalisme à la fois. Dans l'état actuel, l'industrie se bat avec des problèmes d'intégration à chaque étape de la conception, à savoir la spécification, la simulation, la validation et le déploiement. L'absence d'une approche qui comprend les spécifications des interfaces inter-domaines est souvent la cause des problèmes d'intégration de différentes parties d'un système hétérogène. Cette thèse propose une approche pour faire face à l'hétérogénéité en utilisant SysML comme outil fédérateur. Notre proposition repose sur la définition d'une sémantique explicite pour les diagrammes SysML ainsi que des éléments d'adaptation sémantiques capables d'enlever les ambiguïtés dans les interfaces multi-domaines. Pour démontrer l'efficacité de ce concept, un ensemble d'outils basés sur l'ingénierie dirigé par les modèles a été construit pour générer du code exécutable automatiquement à partir des spécificationsIn the era of highly integrated electronics systems, engineers face the challenge of designing and testing multi-faceted systems with single-domain tools. This is difficult and error-prone. These so called heterogeneous systems have their operation and specifications expressed by several formalisms, each one particular to specific domains or engineering fields (software, digital hardware, analog, etc.). Existing design tools are meant to deal with homogeneous designs using one formalism at a time. In the current state, industry is forced to battle with integration issues at every design step, i.e. specification, simulation, validation and deployment. Common divide-to-conquer approaches do not include cross-domain interface specification from the beginning of the project. This lack is often the cause of issues and rework while trying to connect parts of the system that were not designed with the same formalism. This thesis proposes an approach to deal with heterogeneity by embracing it from the beginning of the project using SysML as the unifying tool. Our proposal hinges on the assignment of well-defined semantics to SysML diagrams, together with semantic adaptation elements. To demonstrate the effectiveness of this concept, a toolchain is built and used to generate systems simulation executable code automatically from SysML specifications for different target languages using model driven engineering techniques
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Essa, Irfan A. (Irfan Aziz). "Contact detection, collision forces and friction for physically based virtual world modeling." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14054.
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Rauen, William Bonino. "Physical and numerical modelling of 3-D flow and mixing processes in contact tanks." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55985/.
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Keywords: Computational Fluid Dynamics, Numerical Modelling, Physical Modelling, Contact Tanks, Hydrodynamics, Hydraulic Efficiency, Solute Transport, Mixing Processes, Finite Volume Method, Acoustic Doppler Velocimetry, Tracer Techniques.
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Hagger, Martin S. "The role of perceived control in the theory of planned behaviour in a physical activity context with children." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/7265.
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A series of studies aimed to examine the role of perceived behavioural control in Ajzen's (1985) Theory of Planned Behaviour (TPB) in a physical activity context with children aged 12-14 years. A broader, more differentiated role of perceived control was envisaged in the theory based on the conceptualisation of control and perceived competence put forward by Skinner (1995). The first two studies examined the role of control with respect to the TPB model variables and past behaviour. Study 1 investigated the relations between intention, behaviour, attitude, subjective norms and perceived behavioural control in 181 children. It was hypothesised that attitude, perceived control and subjective norms would be related to intention and intention to behaviour. In addition, it was hypothesised that the covariation between control and attitude observed in previous studies could be better explained by the specification of a direct path between perceived control and attitude. Path analysis confirmed the theoretical relations between the TPB variables and, uniquely, the existence of a perceived control- attitude path forming a triadic arrangement with attitude and intention. It was concluded that perceived control governed two routes to the formation of intentions: a direct, spontaneousp ath and an indirect, more deliberative path via attitudes. This relationship was subsequently confirmed in a sample of 382 children in Study 2 using latent measures of attitude and control. The study demonstrated that direct attitude-intention and attitude-behaviour paths regulated the intention-behaviour relationship and attenuated the control -intention relationship to zero. Further, past behaviour predicted control but not intentions or prospective behaviour suggesting that perceived control includes judgements regarding previous control experiences. Since Studies I and 2 indicated the diverse influence of control on the TPB variables, Study 3 diversified the perceived control variable according to Skinner's (1995) conceptualisation of control. This was achieved through the inclusion of a measure of self-efficacy alongside perceived control in a study of 1152 children. The resulting non-standard model using both latent and observed measures, indicated that self-efficacy regulated the control-intention relationship, while control remained an indirect predictor of intention via attitudes. It was concluded that the spontaneous pathway was largely due to the aspects of control related to past experiences of confidence or self-efficacy. This justified the diversification of the perceived control variable and indicated that when young people consider the control they have over certain behaviours, they refer to a number of different perceptions. To further examine the role of perceived control and examine the origins of the cognitive variables in the TPB, Study 4 examined perceived control from a human needs perspective in 1088 children. The measures included more general, domain-specific rather than behaviour- specific measures of perceived control and locus of causality (PLOC). The latter variables represented the human needs for competence and autonomy, which are hypothesised to be motivational in nature (Deci & Ryan, 1985). Results indicated that relative autonomy predicted perceived behavioural control and attenuated the control-intention relationship to zero. This suggested that autonomy was the driving force behind the process of intern ali sation, in which a person assimilates a behaviour by continual competence satisfying experiences. A final study aimed to confirm the triadic relationships between attitude, perceived control and intention in the TPB by a cumulative analysis of these relationships using the data from Studies 1-4. Meta-analytical techniques were used to produce cumulative correlations corrected for measurement and sampling error between the TPB relationships. Results indicated that the variation in the correlations may have been due to more than just sampling error, indicating the existence of moderating variables. A path analysis using these correlations indicated that the atti tude- intention relationship in the triadic arrangement tended to be attenuated by the control-intention relationship. This series of studies indicate that Perceived behavioural control is an important and diverse predictor of intention in the TPB. In particular, control was shown to be an antecedent of attitudes as well as a direct predictor of intentions and that spontaneous intention formation from control perceptions may have been due to self-efficacy beliefs and past behavioural beliefs being encompassed by perceived control. Finally, the adoption of self-determination theory indicated that more general motives for engaging in physical activity behaviour were antecedent variables of control, attitudes and intention from a social cognitive approach. Such theories helped interpret the relationships in the TPB, in particular the role of control as an important variable in the process of internalisation.
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DESHMUKH, DINAR V. "PHYSICS BASED REDUCED ORDER MODELS FOR FRICTIONAL CONTACTS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115997302.
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Wilson, Stephen P. "A methodology for physically-based contact and meniscus properties in rigid-body computational knee modeling." Thesis, The University of Texas at El Paso, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1594187.
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Determining natural inner knee mechanics is a longstanding goal for researchers with applications to prevention and treatment of knee trauma and osteoarthritis. Physical testing has only provided limited information of knee mechanics due to technical challenges and cost. Modeling has been used for decades to obtain some of this otherwise inaccessible information, and recently finite element analysis (FEA) has become a popular means to this end. However, FEA requires time intensive mesh-creation and has large computational requirements. Ideally, model creation should be easy and simulations should be fast to allow for sensitivity analysis. Although allowing easier model creation and offering over an order of magnitude more computational efficiency than FEA, current rigid body modeling of the knee is limited by imprecise methodologies for defining material properties. Cartilage and meniscus are particular points of weakness.
The following thesis develops an improved methodology for cartilage contact which is user-friendly and allows for precise definition of contact via user-supplied material properties while accounting for changes in stiffness due to discretization. Additionally, meniscus modeling is improved by developing and implementing equations which directly define stress-strain relationships to match values reported in literature or those selected by the user. Results from two implemented knee models are compared to experimental results in literature and sensitivity to material properties and driving kinematics is investigated.
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Mothersole, Peter John Michael. "Modelling physics teachers' pedagogical content knowledge through purposeful relationships between semiotic registers : KEPLER - "Knowledge Environment for Physics Learning and Evaluation of Relationships"." Thesis, University of Northampton, 2005. http://nectar.northampton.ac.uk/3003/.
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Ezrailson, Cathy Mariotti. "EMIT: explicit modeling of interactive-engagement techniques for physics graduate teaching assistants and the impact on instruction and student performance in calculus-based physics." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1467.
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This study measures the effect of a model of explicit instruction (EMIT) on the: 1) physics graduate teaching assistants adherence to reformed teaching methods, 2) impact of the instructional model on GTAs beliefs about the nature of physics and physics problem solving and 3) undergraduate physics students understanding and performance in an introductory calculus-based physics course. Methods included explicit modeling for the treatment group GTAs of the Reformed Teaching Observation Protocol (RTOP) and assessment of treatment and control GTAs and their students throughout the semester. Students understanding was measured using the Force Concept Inventory (FCI) and Flash-mediated Force and Motion Concept Inventory (FM2CA). Students were surveyed about performance of GTAs using the Student Survey (SS). Results indicated changes were tied to individual GTAs beliefs about the nature of physics. Student conceptual understanding reflected a two-fold Hake gain compared to the control group. General application of the EMIT model presupposes explicit instruction of the model for GTAs.
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Wretborn, Joel. "Modelling cracks in solid materials using the Material Point Method." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-136797.
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This thesis investigates a novel way to simulate cracks as an extension of the Mate- rial Point Method (MPM). Previous methods, like CRAMP (CRAcks with Material Points), often use an explicit crack representation to define the material crack. We use an implicit crack representation defined as the intersection between pieces of the original specimen created by a pre-fracture process. Material chunks are there- after forced together using massless particle constraints. The method has proven successful in tearing scenarios, and the main benefits are: (1) minor computational overhead compared to the initial MPM algorithm; (2) simple to implement and scales well in 3 dimensions; (3) gives easy and controllable setup phase for desired material failure mode. The development of the crack extension has required a fully general MPM solver that can handle arbitrarily many distinct bodies connected in the same simulation. Current collision schemes for MPM exists, however these are often focused on two-body collisions and does not scale well for additional objects due to inaccuracies in contact normal calculations. We present a method that uses an iterative pair-wise comparison scheme to resolve grid collisions that extends to any number of collision objects.
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Vitor, Ribeiro De Sá. "3D geostatistical modeling and integration of lithology, physical properties and element contents for characterizing metal deposit in a seafloor hydrothermal vent area." Kyoto University, 2020. http://hdl.handle.net/2433/254523.
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Hakanen, Jani. "Modeling of nanostructures with complex source and drain." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4285.
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In this thesis we report on calculations for open quantum mechanical and certain microwave systems. The models refer to a quantum point contact and an electron cavity. We model this open system with an imaginary potential as source and drain, and use the finite difference method to make our calculations. We report on general features of the model we have found, and compare our calculations with measurements made on microwave cavities.
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Emami, Anahita. "Investigation on Physics-based Multi-scale Modeling of Contact, Friction, and Wear in Viscoelastic Materials with Application in Rubber Compounds." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/97008.
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This dissertation aims to contribute towards the understanding and modeling of tribological phenomena of contact, friction, and wear in viscoelastic materials with application in rubber compounds. Tribiological properties of rubber compounds are important for many applications such as tires, shoe heels and soles, wiper blades, artificial joints, O-ring seals, and so on. In all these applications, the objective is to maximize the friction coefficient to avoid slipping and reduce the wear rate to improve the life expectancy and performance of the products.
The first topic in this study focuses on a novel multiscale contact theory proposed by Persson and explains the advantages of this theory over other classical contact theories. The shortcomings of this theory are also investigated, and three methods are proposed to improve Persson's original contact model by correcting the approximation of deformation in the contact area. The first method is based on the original Greenwood and Williamson (GW) contact theory, which neglects the effect of elastic coupling between asperities. The second method is based on an improved version of GW theory, which considers the elastic coupling effect of asperities in an approximate way. The third method is based on the distribution of local peaks of asperities, which is particularly suitable to determine the fraction of a skewed height profile involved in tribological processes. This method can be implemented within the framework of other proposed methods. Since the height profiles of rough surfaces studied in this dissertation are approximately normally distributed, the second correction method is applied to the original contact model to calculate the real contact area and friction coefficient.
The second topic addresses the theoretical model of hysteresis friction in viscoelastic materials. The multiscale temperature rise of the rubber surface due to hysteresis friction is also modeled and the effect of flash temperature on the real contact area and friction coefficient is studied. Since the hysteresis friction is not the only mechanism involved in the rubber friction, a semi-empirical model is added to the hysteresis model to include the contribution of adhesion and other processes on the real contact area. Based on the improved multiscale contact theory, a pressure-dependent friction model is also developed for viscoelastic materials, which is in good agreement with experimental results.
The third topic deals with the theory of stationary crack propagation in viscoelastic materials and the effect of crack tip flash temperature on the instability of crack propagation observed in some experimental results in the literature. Initially, a theoretical model is developed to calculate the tearing energy vs crack tip velocity in a Kelvin-Voigt rubber model. Besides, two coupled iterative algorithms are developed to calculate the temperature field around the crack tip in addition to the tearing energy as a function of crack tip velocity. In this model, the effect of crack tip flash temperature on the tearing energy is considered to update the relation between tearing energy vs crack tip velocity, which also affects the flash temperature. A theoretical model is also developed to calculate the contribution of the hysteresis effect to the tearing energy vs crack tip velocity using the dynamic modulus master curve of a rubber compound. Then, the low-frequency fatigue test results are compared with the theoretical predictions and used in the framework of powdery rubber wear theory to calculate the stationary rubber wear rate due to fatigue crack propagation.
Moreover, a sliding friction and wear test set-up, with both indoor and outdoor testing capability, is developed to validate the theoretical models. The experimental results confirm that the theoretical model can successfully predict the friction coefficient when there is no trace of thermochemical degradation on the rubber surface. Investigating the wear mechanism of rubber samples on three different surfaces reveals that the contribution of fatigue wear rate is less important than other wear mechanisms such as abrasive wear due to sharp asperities or thermochemical degradation due to a significant rise of temperature on the contact area. Finally, the correlation between friction coefficient and wear rate on different surfaces is studied, and it is found that the relation between friction and wear rate strongly depends on the dominant wear mechanism, which is determined by the surface characteristics, sliding velocity, normal load, and contact flash temperature.PHD
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Gonçalves, Daniel. "Citrus essential oil fractionation using ethanol with different water contents as solvents: phase equilibrium, physical properties and continuous equipment extraction." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-22092017-150246/.
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Essential oils are featured commodities in the global market due their many applications in food and chemical industries, in different medicine areas, and as antibacterial, antifungal, and antioxidant agent. One of the phenomena accountable for the loss of essential oils quality may be associated with the degradation of terpene hydrocarbons by oxidation when exposed to air, light or heat, causing disagreeable odors. The procedure of terpenes content reducing, known as deterpenation, can be performed by diverse techniques, among which the liquid-liquid extraction can be highlighted since this process can be operated without the use of heating and pressure changes, causing low impact on the essential oil sensory qualities and low energy consumption. This research was focused on the fractionation process of citrus essential oils, by liquid-liquid extraction, using ethanol/water mixtures as solvents. Experimental liquid-liquid equilibrium data of model and real citrus systems were obtained. The aroma profile of the crude citrus essential oils (orange - Citrus sinensis and lime - Citrus aurantifolia) and the phases from the liquid-liquid equilibrium was also evaluated. Moreover, the crude citrus essential oils were fractionated in a continuous operation equipment (perforated rotating disc contactor, PRDC). It was verified that the water has an important influence over the fractionation performance, but not over the aroma profile of the phases. The experimental data from the model systems (citrus essential oil model mixture + ethanol + water) were used to adjust parameters of empirical and thermodynamic models, which provided satisfactory results on the calculation of physical property values and compositions of the phases from the real systems (crude citrus essential oil + ethanol + water). The fractionation of citrus essential oils by liquid-liquid extraction technology was technically feasible and can be accomplished into continuous apparatus such as PRDC column. The solvents employed provided extract phases enriched in oxygenated compounds.Óleos essenciais são importantes produtos comercializados mundialmente devido às suas diversas aplicações em indústrias alimentícias e químicas, em diferentes áreas da medicina, e como agentes antibacteriano, antifúngico e antioxidante. Um dos fenômenos responsáveis pela sua perda de qualidade pode estar associado à degradação dos hidrocarbonetos terpênicos por oxidação, quando estes são expostos ao ar, luz ou calor, ocasionando odor desagradável. O procedimento para redução do teor de terpenos no óleo essencial, conhecido como desterpenação, pode ser realizado por diferentes técnicas, entre as quais a extração líquido-líquido se destaca uma vez que pode ser conduzida sem o emprego de calor e mudanças na pressão, o que atenua o impacto nas qualidades sensoriais e demanda menor gasto energético. Este estudo se concentrou no processo de fracionamento de óleos essenciais cítricos, pela técnica de extração líquido-líquido, empregando misturas de etanol e água como solventes. Foram obtidos dados de equilíbrio líquido-líquido de sistemas cítricos modelo e reais. O perfil de aroma dos óleos essenciais brutos (laranja - Citrus sinensis e lima ácida Citrus latifolia) e das fases provenientes do equilíbrio líquido-líquido também foram avaliados. Além disso, os óleos essenciais brutos foram submetidos ao processo de fracionamento em equipamento de operação contínua (coluna de discos rotativos perfurados, PRDC). Verificou-se que a água possui uma importante influência sobre o desempenho do processo de fracionamento, mas não afetou o aroma das fases. Os dados experimentais dos sistemas modelo (mistura modelo de óleo essencial cítrico + etanol + água) foram utilizados para o ajuste de parâmetros de modelos empíricos e termodinâmicos, os quais apresentaram bons resultados no cálculo de valores de propriedades físicas e da composição das fases oriundas dos sistemas reais (óleo essencial cítrico bruto + etanol + água). O fracionamento de óleos essenciais cítricos pela tecnologia de extração líquido-líquido mostrou-se tecnicamente viável e pode ser conduzido em equipamentos contínuos como a coluna de extração PRDC. Os solventes empregados permitiram a obtenção de fases extrato enriquecidas com compostos oxigenados.
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Pederson, Thomas. "From Conceptual Links to Causal Relations — Physical-Virtual Artefacts in Mixed-Reality Space." Doctoral thesis, Umeå : Univ, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-137.
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Thierry-Jebali, Nicolas. "Caractérisations et modélisations physiques de contacts entre phases métalliques et Nitrure de Gallium semi-conducteur." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00744661.
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Les composés III-N, et le Nitrure de Gallium (GaN) en particulier, sont devenus des matériaux semi conducteurs importants pour l'ensemble de l'humanité. Depuis la fin des années 1990, ils ont permis le développement de composants électroluminescents fiables, diodes LED et diodes laser, qui constituent une solution de remplacement à rendement énergétique amélioré par rapport aux composants à incandescence. Il est possible qu'ils jouent aussi un rôle dans les nouvelles générations de composants pour l'électronique de puissance. Lors du développement des composants, des recherches expérimentales permettent de trouver assez rapidement des solutions pour réaliser les briques technologiques indispensables, mais le temps manque pour comprendre les mécanismes physiques mis en jeu. Nos travaux ont eu pour objectif d'approfondir la compréhension de l'influence de la structure physico-chimique sur les propriétés électriques des contacts ohmiques et Schottky sur GaN de type N.
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Wang, Kui. "Characterization and modeling of the thermomechanical behavior of polypropylene-based composites : effect of recycling and filler content." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00962217.
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The use of thermoplastic olefins like polypropylene is currently growing in the automotive industry. However, the increase of wastes from end of life vehicles represents a threat to our environment. Mechanical recycling is the most acceptable and ecological method. The purpose of this thesis is to identify the thermomechanical degradation mechanisms of PP-based composites, as a function of fillers content. Recycling was simulated by multiple extrusions. The considered fillers consist of ethylene octene copolymer and talc. The different properties of recycled PP-based composites were studied by a multiphysical approach. A detailed study of high strain rate and temperature sensitivities of recycled PP-based composites is achieved. The micromechanical modeling is used to predict the yield and the elastic behaviors of non-recycled and recycled materials.
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Tai, Jui-He. "Effect of Void Fraction on Transverse Shear Modulus of Advanced Unidirectional Composites." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6591.
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In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.
Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, appropriate boundary conditions are applied to a three-dimensional representative volume element (RVE). To improve the accuracy of the model, multiple cells of the RVE are used and the value of the transverse shear modulus is calculated by an extrapolation technique that represents a large number of cells.
Comparing the available analytical and empirical models to the finite element model from this work shows that for polymeric matrix composites, the estimate of the transverse shear modulus by Halpin-Tsai model had high credibility for lower fiber volume fractions; the Mori-Tanaka model was most accurate for the mid-range fiber volume fractions; and the Elasticity Approach model was most accurate for high fiber volume fractions.
Since real-life composites have voids, this study investigated the effect of void fraction on the transverse shear modulus through design of experiment (DOE) statistical analysis. Fiber volume fraction and fiber-to-matrix Young’s moduli ratio were the other influencing parameters used. The results indicate that the fiber volume fraction is the most dominating of the three variables, making up to 96% contribution to the transverse shear modulus. The void content and fiber-to-matrix Young’s moduli ratio have negligible effects.
To find how voids themselves influence the shear modulus, the transverse shear modulus was normalized with the corresponding shear modulus with a perfect composite with no voids. As expected, the void content has the largest contribution to the normalized shear modulus of 80%. The fiber volume fraction contributed 12%, and the fiber-to-matrix Young’s moduli ratio contribution was again low.
Based on the results of this work, the influences and sensitivities of void content have helped in the development of accurate models for transverse shear modulus, and let us confidently study the influence of fiber-to-matrix Young’s moduli ratio, fiber volume fraction and void content on its value.
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Augustine, Robin. "Electromagnetic modelling of human tissues and its application on the interaction between antenna and human body in the BAN context." Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00499255.
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Les réseaux BAN (Body Area Network) révolutionnent le concept de la surveillance et de la prise en charge à distance de la santé du patient. Le BAN fournit des informations sur l'état de santé du patient en temps réel quelque soit l'endroit où il se trouve. Dans le « télé monitoring », des capteurs de mouvement, de respiration ou du rythme cardiaque placés à l'intérieur ou sur le corps humain transmettent des données via le réseau sans fil constituant le BAN, une antenne étant associée à chaque nœud du réseau. La communication peut être in/on, on/on ou on/off selon que les antennes sont placées à l'intérieur, sur ou à l'extérieur du corps. Le développement des BAN nécessite la réalisation de modèles (ou fantômes) simulant au mieux les propriétés électromagnétiques du corps humain. Des antennes portables, miniaturisées doivent être réalisées avec des contraintes d'intégration d'une part (aux vêtements, à des objets type montre ou badge), des contraintes de résistance ou de prise en compte de l'influence du corps d'autre part. La réduction de l'impact des antennes sur les tissus en terme de SAR (Specific Absorption Rate) doit également être considérée. Dans ce travail, l'objectif est de développer des fantômes valables pour les communications dans et sur le corps. Les matériaux de base sélectionnés sont d'origine biologique (biocéramiques et biopolymères) avec des propriétés proches de celles des tissus humains. Ces fantômes étant biocompatibles, ils sont essentiellement non toxiques alors que les fantômes usuels le sont en général. D'autre part, différents types d'antennes conformables, fonctionnant dans la bande ISM 2.4 GHz ont été développées et étudiées dans la perspective du BAN. Les antennes voient leur adaptation et leur efficacité chuter au contact ou à proximité du corps, ce qui constitue un écueil majeur pour établir une bonne communication. Différentes méthodes permettant de réduire l'influence du corps (plan de masse à l'arrière, surface haute impédance, feuille de ferrite polymère) sont testés et leurs avantages et inconvénients développés. Des mesures de SAR permettent aussi de démontrer l'efficacité de ces méthodes sur la réduction de la puissance absorbée par les tissus. Au final, ce travail apporte une contribution à l'étude théorique et expérimentale de l'interaction entre corps humain et antenne dans le cadre des réseaux BAN appliqués à la télésurveillance de la santé
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Öhnander, Fred. "An Attempt Towards FE-Modelling of Fracture Propagation in Railway Wheels." Thesis, KTH, Spårfordon, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234468.
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The demand for higher velocities and heavier axle loads for freight trains leads to higher forces on the railway wheels which in turn lead to an increase in stresses on and below the surface of the wheel-rail contact. By time, this induces wear on the wheels which consequently lead to higher maintenance costs and in some cases accidents. The ability to predict the evolution of wheel profiles due to uniform wear has been demonstrated with a rather accurate precision in most operational conditions. These wear models are based on wear coefficients and since they are not usually valid for real operational conditions, the models are generally calibrated against real-life scenarios in order to adjust the coefficients from test conditions to real-life lubrication conditions. This engineering approach can be useful in prediction of wear in systems where the materials and contact conditions do not vary. However, when addressing material development focused on reducing specific damage modes, the approach is of limited use because the obtained wear coefficients are not directly related to material properties. Therefore, attempts towards developing physical fracture propagation models that relates to the contact conditions and material properties have been made. The purpose has been to retrieve vital information about where a fracture initiates and how it propagates. In the long run, it is of great interest to be able to attain information about how a material particle is removed from the contact surface. Studies for this type of model was done in the 70’s and 80’s mainly with pin-disk experiments but has not been utilized in the specific field of wheel-rail contact. The thesis is part of the FR8RAIL project arranged by the European rail initiative Shift2Rail. Literature studies have been the basis for the thesis in order to gain vital insights into fracture mechanics and other related fields. The physical fracture propagation models have been constructed in the FE software Abaqus with the implementation of the XFEM. For the 2D model, the fracture initiates at the top of the implanted inclusion when the friction coefficient is and propagates upwards a few elements. For , the fracture initiates at the right surface boundary where the pressure distribution and traction is applied. The fracture propagation angle increases relative to the surface as the friction coefficient value is increased. The fracture for the 3D model extends broader compared to the 2D model at the top of the inclusion in the case of . The fracture initiates at the same surface location as for the 2D model for . The fracture propagation is however non-existent due to convergence problems. The FE-models constructed are initial steps towards analysing the fracture propagation and closely related phenomena for a railway freight wheel in detail. At the end of the thesis, the simplified models give mainly information about the fracture initiation, propagation and its patterns. From this first phase, further adjustments and improvements can take place in order to eliminate the margins of error. In the long run, fully integrated models with further implementations such as detailed microstructure for the contact conditions, plastic behaviour for the material, and complete three-dimensional models can finally be employed.Efterfrågan på högre hastigheter och tyngre axelbelastningar för godståg leder till högre krafter på järnvägshjulen som i sin tur leder till ökade spänningar på och under ytan vid hjul-räl-kontakten. Med tiden induceras slitage på hjulen som följaktligen leder till höga underhållskostnader och i vissa fall olyckor. Förmågan att förutse utvecklingen av hjulprofiler på grund av enhetligt slitage har visats kunna ske med en noggrann precision under de flesta driftsförhållanden. Dessa slitagemodeller bygger på slitagekoefficienter, och eftersom de vanligtvis inte är giltiga under realistiska driftsförhållanden är modellerna i allmänhet kalibrerade mot verkliga händelseförlopp för att justera koefficienterna från testförhållandena till realistiska smörjförhållanden. Detta tekniska tillvägagångssätt kan vara användbart vid prognos av slitage i system där material och kontaktförhållanden inte varierar. När man addresserar materialutveckling inriktad på att reducera specifika skadelägen är emellertid tillvägagångssättet av begränsad användning eftersom de erhållna slitagekoefficienterna inte är direkt relaterade till materialegenskaper. Därför har försök gjorts till att utveckla fysikaliska sprickbildningsmodeller som relateras till kontaktförhållanden och materialegenskaper. Syftet har varit att erhålla viktig information om var en spricka initieras och hur den fortskrider. I det långa loppet är det även av stor vikt att kunna erhålla information om hur en materialpartikel avlägsnas från kontaktytan. Studier för denna typ av modeller har gjorts på 70- och 80-talet i huvudsak med stift- och skivexperiment men har inte använts inom det specifika området för hjul-räl-kontakt. Avhandligen ingår i FR8RAIL-projektet som arrangeras av det europeiska järnvägsinitiativet Shift2Rail. Literaturstudier har varit grunden för avhandlingen för att få väsentlig insikt i frakturmekanik och andra relaterade områden. De fysiska sprickbildningsmodellerna har konstrueras i FE-mjukvaran Abaqus med XFEM som implementering. För 2D-modellen initieras sprickan överst vid den implanterade imperfektionen när friktionskoefficienten är och propagerar uppåt några få element. För initieras sprickan på högra ytgränsen där tryckfördelning och friktionskraft appliceras. Utbredningsvinkeln för sprickan ökar relativt till ytan då friktionskoefficienten ökar. Sprickan för 3D-modellen breder ut sig mer jämfört med 2D-modellen överst vid imperfektionen då . Sprickan initieras på samma ytplats som för 2D-modellen vid . Sprickbildningen är dock obefintlig på grund av konvergensproblem. De konstruerade FE-modellerna är initiala steg mot att analysera sprickutbredningen och närbesläktade fenomen för ett godstågs järnvägshjul i detalj. I slutet av avhandlingen ger de förenklade modellerna huvudsakligen information om sprickinitiering, utbredning och dess mönster. Ytterligare justeringar och förbättringar kan ske efter denna första fas i syfte att eliminera felmarginalerna. På lång sikt kan slutligen helt integrerande modeller med ytterligare implementeringar såsom detaljerad mikrostruktur för kontaktförhållandena, oelastiskt materialbeteende och kompletta tredimensionella modeller användas.
FR8RAIL
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Guégués, Maria Margarida Letras. "A modelação matemática com recurso a tecnologia: Um estudo em contexto de colaboração entre professoras de matemática e de física-química." Master's thesis, Universidade de Évora, 2009. http://hdl.handle.net/10174/18630.
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Este estudo teve como objectivo compreender o desenvolvimento de tarefas de modelação, por parte de uma professora de Matemática e de uma professora de Física Química, no âmbito de trabalho colaborativo. Para tal foram formuladas três questões orientadoras: 1. Como é que os professores seleccionam e preparam as tarefas de modelação a colocar aos alunos em situação de sala de aula? Que características das tarefas de modelação se mostram fundamentais para a sua selecção? 2. como desenvolvem os professores as tarefas de modelação na sala de aula? Como gerem e dinamizam as aulas onde colocam tarefas de modelação aos alunos? Que papel reservam ao professor e ao aluno? 3. como exploram os professores as potencialidades das calculadoras gráficas no desenvolvimento das tarefas de modelação? Que questões se colocam à utilização de sensores? O estudo decorreu numa escola secundária, durante o ano lectivo de 2005/06, sob proposta e com a participação da investigadora, envolvendo uma professora de Matemática e uma professora de Física-Química de uma mesma turma de 100 ano. O grupo colaborativo reuniu regularmente e preparou e leccionou aulas com tarefas de modelação matemática, recorrendo a calculadoras gráficas e sensores, tarefas e tecnologias novas para ambas as professoras. A metodologia utilizada na investigação tem natureza qualitativa, tendo sido realizadas duas entrevistas longas a cada professora, uma no início e outra no fim do estudo, bem como entrevistas de curta duração às professoras após cada uma das aulas onde foram desenvolvidas as tarefas. Foram também recolhidos registos das sessões colectivas de trabalho e elaborado um "diário de bordo". O estudo permitiu formular as seguintes conclusões: - Quando as professoras seleccionavam as tarefas de modelação a propor aos seus alunos tinham em consideração o cumprimento dos programas, os conteúdos a abordar e a diversidade de questões que se podem formular sobre os mesmos e o interesse e significado da experiência para os alunos. - O tempo que é necessário para a preparação e execução das tarefas de modelação pareceu ser factor de grande peso na sua selecção. - O elevado número de alunos por turma pode ser factor um negativo para o desenvolvimento de tarefas de modelação na sala de aula. -Na opinião das professoras, o recurso à calculadora gráfica e aos sensores para realizar a recolha de dados relativos a uma tarefa de modelação tomou-as mais apelativas e ajudou os alunos a compreender a situação em causa assim como permitiu tomar mais nítida a relação entre a Matemática e a Física. ABSTRACT: This study aimed to understand the development of modelling tasks, by a Mathematics teacher and a Physics-Chemistry teacher, as part of collaborative work. For this study were formulated three guidelines: 1. How do teachers select and prepare the modelling tasks to present to the students in a classroom situation? What characteristics of these tasks are essential for their selection? 2. How do teachers develop the modelling tasks in the classroom? How do they manage and dynamize the classes where the modelling tasks took place? What role it's reserd to the teacher and the student? 3. How do teachers exploit the potential of graphics calculator in the development of the modelling tasks? What issues arise for the use of sensors? This study took place at a secundary school during the academic year 2005/06, as a suggestion and with the participation of the researcher, involving a Mathematics teacher and a Physics-Chemistry teacher of the same class (10th grade). The collaborative group had regular meetings and prepared and developed modellin tasks in the classroom using graphics calculator and sensors, which was a new activity for all the teachears. The methodology used has a qualitative nature. Two interviews were made to each teacher, one at baseline and another at the end of the study, fourteen work sections and three modelling tasks were explored in classroom context after which followed small interviews to the teacher that gave the class. ln addition records were also made in a small "log-book". This study allowed to reach the following conclusions: - When the teachers select the modelling tasks to offer its students they take into account the programs, the contents and the diversity of questions that can be made on it and the interest and significance of the experience for students. - The time needed for preparation and implementation of the modelling tasks is another factor of great weight in its selection. - The high number of student per class can be a negative factor for the development of modelling tasks in the classroom. Iii - ln the teacher’s opinion, the use of the graphics calculator and sensors to collect data on a modelling tasks makes its more attractive and helps students to understand the situation and makes clearer the link between Mathematics and Physics.
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Pastor, Poquet Vicente. "Experimental and modeling assessment of the main bio-physical-chemical mechanisms and kinetics in high-solids anaerobic digestion of organic waste High-Solids Anaerobic Digestion requires a tradeoff between Total Solids, Inoculum-to-Substrate Ratio and Ammonia Inhibition Semi-continuous Mono-digestion of OFMSW and Co-digestion of OFMSW with Beech Sawdust: Assessment of the Maximum Operational Total Solid Content High-solids anaerobic digestion model for homogenized reactors Non-Ideal Bio-Physical-Chemical Effects on High-Solids Anaerobic Digestion of the Organic Fraction of Municipal Solid Waste." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC2206.
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La fraction fermentescible des ordures ménagères (FFOM) comprend des déchets facilement biodégradables (alimentaires), et des lentement biodégradables (lignocellulosiques). La digestion anaérobie (DA) est une biotechnologie dans laquelle la FFOM est décomposé dans biogaz (CH4 + CO2). En raison de la teneur élevée en CH4 (50-70%), le biogaz pouvant être utilisé comme source d'énergie. En outre, DA produit un digestat partiellement stabilisé, riche d'éléments nutritifs. La DA à haute teneur en solides est une stratégie pour l'amélioration de l'efficacité. Elle correspond à une opération avec une teneur en matières sèches (MS) ≥ 10%, qui permet de réduire la taille du réacteur et les coûts de fonctionnement. Toutefois, l'augmentation de la MS peut entraîner une instabilité biochimique, et même une défaillance par acidification, à cause de la forte charge organique et l'accumulation d'inhibiteurs. L'inhibiteur le plus notable est NH3. Par conséquent, un équilibre entre l'amélioration de l'économie et l'instabilité est requis pour le traitement de la FFOM par DA à haute teneur en solides. Cette thèse de doctorat porte sur les principaux mécanismes cinétiques bio-physiques-chimiques mis en jeu lors de la DA à haute teneur en solides, dans le but d’optimiser son application. Des expériences de laboratoire ont mis en œuvre pour élucider les principales forces et faiblesses de ce procédé. Simultanément, le développement d'un modèle spécifique à la DA à haute teneur en solides a permis de condenser les connaissances expérimentales sur les effets qui se produisent lors de l'augmentation de la teneur de la MS. Les expériences en réacteur batch ont nécessité un compromis entre la teneur initiale en MS, le rapport entre l'inoculum et le substrat (X/S), l'alcalinité et la teneur en azote, afin d'évaluer les effets de l'augmentation de la teneur initiale en MS sur le rendement en CH4, l’élimination de la MS et la conversion de la demande chimique en oxygène. En particulier, des ratios X/S bas ont conduit à l'acidification, tandis que l'accumulation de NH3 a conduit à une accumulation d’acides gras volatils (AGV). Dans des expériences en semi-continue, la DA à haute teneur en solides nécessitait de diminuer le débit de l’effluent pour contrer l'élimination de la masse. Cependant, la mono-digestion de la FFOM facilement biodégradable ne peut pas supporter MS ≥ 10% sans augmenter le risque de surcharge. La surcharge était associée à la forte biodégradabilité et à l'accumulation de NH3. Par conséquent, l'ajout de sciure de bois à FFOM a permis à des réacteurs semi-continus de fonctionner jusqu'à 30% de MS, en raison de la biodégradabilité et de la teneur d'azote plus faibles ce substrat. La principale nouveauté de cette thèse est le développement d'un modèle pour la DA à haute teneur en solides. Ce modèle permet de simuler la dynamique masse et de MS dans des digesteurs, contrairement aux modèles sur des simulations de MS < 10%. Ce modèle prend également en compte l’effet de la concentration en MS sur les espèces solubles. Un module bio-physico-chimique « non idéal », modifiant les constantes d’équilibre acide-base, a été couplé ensuite au modèle. Il est à noter que la DA à haute teneur en solides est souvent caractérisée par une force ionique élevée (I ≥ 0,2 M), affectant le pH, la concentration en NH3 et le transfert de CO2 liquide-gaz. L'étalonnage du modèle a montré que la DA à haute teneur en solides requis plusieurs jeux de données expérimentaux pour contourner la « non-identifiabilité » des paramètres. La DA à haute teneur en solides pouvait fonctionner à une I allant jusqu'à 0,9 M et NH3 allant jusqu'à 2,3 g N/L, à des teneurs en MS élevées (25-30%). En outre, l'étalonnage a suggéré que l'utilisation d'une inhibition non-compétitive de NH3 devrait être testée plus avant. Il a également été recommandé de mettre au point d'autres développements du modèle. Ces résultats pourraient aider à l'optimisation de la DA à haute teneur en solidesThe organic fraction of municipal solid waste (OFMSW) includes readily biodegradable wastes such as food waste, and slowly biodegradable wastes such as lignocellulosic materials. Anaerobic digestion (AD) is a mature treatment biotechnology in which OFMSW is decomposed to a mixture of methane (CH4) and carbon dioxide (CO2), known as biogas. Due to the elevated CH4 content (50-70%), biogas can be used as a source of renewable energy. Moreover, AD yields a partially stabilized digestate, allowing the recycle of nutrients to agriculture. High-solids anaerobic digestion (HS-AD) is a well-suited strategy to enhance the overall AD efficiency for OFMSW treatment. HS-AD is operated at a total solid (TS) content ≥ 10%, permitting to reduce the reactor size and overall operational costs. Nonetheless, the TS increase can result into biochemical instability, and even reactor failure by acidification. Both the high organic load and the buildup of inhibitors can be responsible for the HS-AD instability. The most notable inhibitor in HS-AD of OFMSW is NH3. Therefore, a balance is often required between enhancing the HS-AD economy and the ‘undesired’ instability for OFMSW treatment. This PhD research investigated the main bio-physical-chemical mechanisms and kinetics in HS-AD of OFMSW, with the aim to optimize the industrial application and maximize the kinetic rates. Laboratory-scale batch and semi-continuous experiments highlighted the main strengths and weaknesses of HS-AD. Simultaneously, the development of a HS-AD model permitted to condense the experimental knowledge about the bio-physical-chemical effects occurring when increasing the TS content in HS-AD.HS-AD batch experiments required a tradeoff between the initial TS, the inoculum-to-substrate ratio (ISR), the alkalinity and the nitrogen content, to assess the effects of increasing the initial TS content upon the methane yield, TS removal and chemical oxygen demand conversion. Particularly, a low ISR led to acidification, whereas the NH3 buildup led to volatile fatty acid (VFA) accumulation, reducing the methane yield, whether or not co-digestion of OFMSW with beech sawdust was used.In semi-continuous experiments, HS-AD of OFMSW required a reduced effluent compared to the influent to counterbalance the organic mass removal associated to the biogas production. Nonetheless, mono-digestion of readily-biodegradable OFMSW could not sustain a TS ≥ 10% without exacerbating the risk of substrate overload. Overloading was associated to the high biodegradability and the NH3 buildup. Thus, adding sawdust to OFMSW permitted to operate the reactors up to 30% TS, due to the lower biodegradability and nitrogen content of lignocellulosic substrates. As the main novelty of this PhD research, a HS-AD model based on the Anaerobic Digestion Model No.1 (ADM1) was developed. This model simulates the reactor mass and TS in HS-AD, in contrast of models focusing on ‘wet’ AD simulations (TS < 10%). Moreover, the HS-AD model considers also the TS concentration effect on soluble species. A ‘non-ideal’ bio-physical-chemical module, modifying predominantly the acid-base equilibriums, was subsequently coupled to the HS-AD model. Noteworthy, HS-AD is often characterized by a high ionic strength (I ≥ 0.2 M), affecting the pH, NH3 concentration and CO2 liquid-gas transfer, as the most important triggers for HS-AD inhibition. The HS-AD model calibration required multiple experimental datasets to circumvent parameter non-identifiability. The model calibration showed that HS-AD of OFMSW might be operated at I up to 0.9 M and NH3 up to 2.3 g N/L, particularly at higher TS (25-30%). Moreover, the model calibration suggested that the non-competitive NH3 inhibition should be further tested. Further HS-AD model developments (e.g. precipitation) were also recommended. All these results might aid in the optimization of HS-AD for organic waste treatment, renewable energy and nutrient recovery
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Picard-Limpens, Cécile. "Expressive Sound Synthesis for Animation." Phd thesis, Université de Nice Sophia-Antipolis, 2009. http://tel.archives-ouvertes.fr/tel-00440417.
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L'objectif principal de ce travail est de proposer des outils pour une synthèse en temps-réel, réaliste et expressive, des sons résultant d'interactions physiques entre objets dans une scène virtuelle. De fait, ces effets sonores, à l'exemple des bruits de collisions entre solides ou encore d'interactions continues entre surfaces, ne peuvent être prédéfinis et calculés en phase de pré-production. Dans ce cadre, nous proposons deux approches, la première basée sur une modélisation des phénomènes physiques à l'origine de l'émission sonore, la seconde basée sur le traitement d'enregistrements audio. Selon une approche physique, la source sonore est traitée comme la combinaison d'une excitation et d'un résonateur. Dans un premier temps, nous présentons une technique originale traduisant la force d'interaction entre surfaces dans le cas de contacts continus, tel que le roulement. Cette technique repose sur l'analyse des textures utilisées pour le rendu graphique des surfaces de la scène virtuelle. Dans un second temps, nous proposons une méthode d'analyse modale robuste et flexible traduisant les vibrations sonores du résonateur. Outre la possibilité de traiter une large variété de géométries et d'offrir une multi-résolution des paramètres modaux, la méthode permet de résoudre le problème de cohérence entre simulation physique et synthèse sonore, problème fréquemment rencontré en animation. Selon une approche empirique, nous proposons une technique de type granulaire, exprimant la synthèse sonore par un agencement cohérent de particules ou grains sonores. La méthode consiste tout d'abord en un prétraitement d'enregistrements destiné à constituer un matériel sonore sous forme compacte. Ce matériel est ensuite manipulé en temps réel pour, d'une part, une resynthèse complète des enregistrements originaux, et d'autre part, une utilisation flexible en fonction des données reportées par le moteur de simulation et/ou de procédures prédéfinies. Enfin, l'intérêt est porté sur les sons de fracture, au vu de leur utilisation fréquente dans les environnements virtuels, et en particulier les jeux vidéos. Si la complexité du phénomène rend l'emploi d'un modèle purement physique très coûteux, l'utilisation d'enregistrements est également inadaptée pour la grande variété de micro-événements sonores. Le travail de thèse propose ainsi un modèle hybride et des stratégies possibles afin de combiner une approche physique et une approche empirique. Le modèle ainsi conçu vise à reproduire l'événement sonore de la fracture, de son initiation à la création de micro-débris.
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Boutoutaou, Hamid. "Etude d'un emmanchement fretté compte tenu de l'effet combiné des défauts de forme et d'état de surface." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00728865.
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Le but principal de cette thèse est de présenter deux contributions dans le domaine desassemblages frettés en prenant en considération les défauts de forme et d'état de surface. Lapremière contribution concerne l'étude de l'influence du défaut de forme sur les caractéristiquesdes assemblages frettés en utilisant une approche basée sur la modélisation par éléments finis.Nous avons constaté que ce défaut a une influence notable sur la résistance de l'assemblage. Destravaux déjà réalisés dans le laboratoire de mécanique de l'université de Bourgogne ont étéconfirmés. Dans la deuxième contribution, nous avons proposé d'intégrer les défauts d'état desurface (rugosité) en créant un élément fini homogénéisé d'interface. Cette technique nous afacilité le maillage de l'interface formés par de macro-éléments traduisant le comportement desaspérités. Ce comportement particulier, dépend de plusieurs paramètres mécaniques etgéométriques qui ont été pris en compte pour définir et identifier numériquement une loid'élasticité isotrope transverse. Cette nouvelle loi a permis de simuler correctement lesassemblages frettés en prenant en compte le défaut d'état de surface. Les résultats obtenus ont étéconfrontés aux expérimentations. En fin, une méthodologie de conception des spécifications dufrettage en considérant le processus d'élaboration des surfaces a été proposée.
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Verez, Guillaume. "Contribution à l’étude des émissions vibro-acoustiques des machines électriques : cas des machines synchrones à aimants dans un contexte automobile." Thesis, Le Havre, 2014. http://www.theses.fr/2014LEHA0024/document.
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Dans un contexte automobile électrique et hybride, la part des machines synchrones à aimants permanents s'est accrue exponentiellement. Cette évolution s'accompagne d'exigences en termes d'émissions vibro-acoustiques. En termes de dimensionnement de la chaîne de traction, l'analyse multiphysique du moteur s'avère être un enjeu crucial pour son développement. La nécessité de disposer de codes informatiques de conception possédant des temps de calcul faibles pour une précision maximale se fait ressentir pour l'exploration de solutions potentiellement performantes dans les premières étapes du processus de dimensionnement. A ce titre, les aspects vibratoires et acoustiques sont modélisés analytiquement et par éléments finis dans la présente thèse. Ainsi, au moyen du modèle magnétique, l'analyse magnéto-vibro-acoustique faiblement couplée (résolution itérative des différentes physiques) peut être réalisée.La thèse est découpée en quatre parties. La première expose un état de l’art sur les émissions vibro-acoustiques des machines et notamment la modélisation du bruit d’origine magnétique. Les problématiques de la modélisation sont détaillées. Dans une deuxième partie, les modèles sont largement décrits. Les modèles éléments finis sont validés expérimentalement. Une troisième partie se propose de valider les modèles analytiques par éléments finis, en complexifiant progressivement la géométrie d’une machine à aimants montés en surface à flux radial. Enfin, la dernière partie utilise les modèles éléments finis pour étudier des machines non-conventionnelles comme les machines à commutation de flux et les machines à aimants en surface à flux axialThe proportion of permanent magnets synchronous motors used for electric and hybrid automotive traction has exponentially increased during the past decade. This evolution comes with ever-demanding low noise and vibrations requirements. Multi-physics analysis of the motor is a decisive issue for the development of the powertrain. For the exploration of potentially efficient motor solutions in first design steps, it is thus a necessity to have at disposal fast and accurate computer codes. In this respect, acoustic and vibratory aspects are modeled using finite element and analytical models in this thesis. As a result, using an electromagnetic model, the weakly-coupled magneto-vibro-acoustic analysis (iterative solving of each physic) can be performed.The thesis is divided into four parts. The first part states the art on machine vibro-acoustic emissions and focuses on noise of magnetic origins modeling. Issues of modeling are detailed. Then, models are described to a great extent in the second part. Finite element models are favorably compared to experimental measures. A third part validates analytical models in comparison to finite element analysis, by gradually complicating the geometry of a surface permanent magnets radial flux machine. Finally, a fourth part uses finite element models to study non-conventional machines such as flux switching radial flux machines and surface permanent magnets axial flux machines
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Sbartaï, Zoubir Mehdi. "Caractérisation physique des bétons par radar : approche neuromimétique de l'inversion." Toulouse 3, 2005. http://www.theses.fr/2005TOU30196.
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L'évaluation non destructive des ouvrages en béton vise un objectif majeur : obtenir des informations de nature à contribuer au diagnostic de l'état de l'ouvrage ou à alimenter des modèles de prédiction de durée de vie et/ou de requalification. Parmi les informations intéressantes à évaluer in situ, les teneurs en eau et en chlorures des bétons sont des indicateurs pathologiques pertinents, notamment vis-à-vis du risque de corrosion. La quantification de ces grandeurs physiques in situ et l'évaluation de leurs variations spatiales au sein des structures présentent donc un intérêt évident. L'objectif de ce travail de recherche s'inscrit dans ce contexte. Il porte sur l'application de la technologie radar à l'évaluation quantitative des teneurs en eau et en chlorures des bétons. Le problème a été abordé selon une approche statistique, basée sur le concept des réseaux de neurones artificiels. Une banque de données expérimentales, associant caractéristiques physiques de bétons et signatures radar, a été constituée en laboratoire. Cette banque de données a permis de développer un modèle neuromimétique d'inversion de la mesure radar capable de prédire, avec une précision acceptable, les teneurs en eau et en chlorures des bétonsThe main objective of the non-destructive evaluation is to obtain information permitting the diagnosis of concrete structures or to quantify input data of durability prediction and/or recalculation models. Among the interesting information to be evaluated on site, water and chlorides content of concrete are a relevant pathological features. The on site quantification of these physical factors and the evaluation of theirs spatial variation are very important. The goal of this research work is related to the application of radar technology for the physical characterization of concrete, especially on the quantitative evaluation of water and chlorides content. The problem has been resolved using statistical approach based on artificial neural network model. Experimental data base was then implemented, which related physical characteristics of concrete and radar parameters. This data base has been leaded to develop neural network model of radar measurement able to predict, with satisfactory error, water and chlorides content of concrete made in laboratory
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Taforel, Paul. "Apport de la Méthode des Éléments Discrets à la Modélisation des Maçonneries en Contexte Sismique : Vers une Nouvelle Approche de la Vulnérabilité Sismique." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2012. http://tel.archives-ouvertes.fr/tel-00801814.
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L'évaluation des risques naturels et du risque sismique en particulier a pris une importance croissante pour les autorités publiques ces dernières années, entraînant une adaptation importante des outils utilisés jusqu'à présent dans l'étude de la vulnérabilité du bâti. Il est nécessaire de mieux évaluer ces risques afin de mieux y faire face. De nouvelles approches doivent être proposées pour répondre à ces objectifs dont les approches numériques font partie. Parmi les méthodes numériques développées pour tenir compte de la spécificité du bâti maçonné figurent les approches par éléments discrets comme la méthode NSCD (" Non Smooth Contact Dynamics "). Les travaux présentés dans cette thèse visent à mieux appréhender le comportement mécanique et dynamique des ouvrages maçonnés en utilisant ce type de méthode implémenté dans le code de calcul LMGC90, afin d'affiner la compréhension et la caractérisation de la vulnérabilité sismique des édifices en maçonnerie. La méthodologie que nous cherchons à mettre en place vise à traiter la vulnérabilité sismique de bâtiments spécifiques ou au contraire d'ensembles de bâtiments de même typologie.
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Lacoursière, Claude. "Ghosts and machines : regularized variational methods for interactive simulations of multibodies with dry frictional contacts." Doctoral thesis, Umeå University, Computing Science, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1143.
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A time-discrete formulation of the variational principle of mechanics is used to provide a consistent theoretical framework for the construction and analysis of low order integration methods. These are applied to mechanical systems subject to mixed constraints and dry frictional contacts and impacts---machines. The framework includes physics motivated constraint regularization and stabilization schemes. This is done by adding potential energy and Rayleigh dissipation terms in the Lagrangian formulation used throughout. These terms explicitly depend on the value of the Lagrange multipliers enforcing constraints. Having finite energy, the multipliers are thus massless ghost particles. The main numerical stepping method produced with the framework is called SPOOK.
Variational integrators preserve physical invariants globally, exactly in some cases, approximately but within fixed global bounds for others. This allows to product realistic physical trajectories even with the low order methods. These are needed in the solution of nonsmooth problems such as dry frictional contacts and in addition, they are computationally inexpensive. The combination of strong stability, low order, and the global preservation of invariants allows for large integration time steps, but without loosing accuracy on the important and visible physical quantities. SPOOK is thus well-suited for interactive simulations, such as those commonly used in virtual environment applications, because it is fast, stable, and faithful to the physics.
New results include a stable discretization of highly oscillatory terms of constraint regularization; a linearly stable constraint stabilization scheme based on ghost potential and Rayleigh dissipation terms; a single-step, strictly dissipative, approximate impact model; a quasi-linear complementarity formulation of dry friction that is isotropic and solvable for any nonnegative value of friction coefficients; an analysis of a splitting scheme to solve frictional contact complementarity problems; a stable, quaternion-based rigid body stepping scheme and a stable linear approximation thereof. SPOOK includes all these elements. It is linearly implicit and linearly stable, it requires the solution of either one linear system of equations of one mixed linear complementarity problem per regular time step, and two of the same when an impact condition is detected. The changes in energy caused by constraints, impacts, and dry friction, are all shown to be strictly dissipative in comparison with the free system. Since all regularization and stabilization parameters are introduced in the physics, they map directly onto physical properties and thus allow modeling of a variety of phenomena, such as constraint compliance, for instance.
Tutorial material is included for continuous and discrete-time analytic mechanics, quaternion algebra, complementarity problems, rigid body dynamics, constraint kinematics, and special topics in numerical linear algebra needed in the solution of the stepping equations of SPOOK.
The qualitative and quantitative aspects of SPOOK are demonstrated by comparison with a variety of standard techniques on well known test cases which are analyzed in details. SPOOK compares favorably for all these examples. In particular, it handles ill-posed and degenerate problems seamlessly and systematically. An implementation suitable for large scale performance and accuracy testing is left for future work.
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Meriaux, Jean. "Etude expérimentale et modélisation de l'endommagement du contact aube-disque de soufflante soumis à des chargements de fretting fatigue." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00730679.
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L'optimisation du dimensionnement des structures passe par une meilleure connaissance de leur mode d'endommagement. Cette étude se focalise donc sur la caractérisation de l'endommagement du contact aube/disque des moteurs aéronautique. Cet assemblage mécanique est soumis a une combinaison d'un effort normal (force centrifuge) et tangentiel (dynamique de l'aube). La portée du disque en Ti-6Al-4V subi donc un chargement complexe de type fretting fatigue. Ce type de sollicitation entraine, entre autre dégradation, de la fissuration dont la modélisation expérimentale et numérique est rendue difficile par les limitations des moyens et des connaissances actuelles. Le premier objectif de ce travail de thèse est de développer un moyen d'essai et une instrumentation associée afin d'étudier de façon qualitative et quantitative la fissuration d'un contact Ti-6Al-4V/Ti-6Al-4V. Le second but est d'utiliser les données issues de ce moyen expérimental afin de proposer un modèle de prédiction des durées de vie de cet assemblage. Un montage inédit de fretting fatigue double vérin mono-contact a été mis en place avec une instrumentation nouvelle pour ce type d'essai : suivi de fissuration par suivi de potentiel et par émission acoustique. Une attention particulière a été apportée aux calibrations et aux méthodologies expérimentales. Ce banc d'essai permet notamment de simuler des efforts de fretting applique en phase ou alors de telle manière a simuler un vrai cycle de vol. Cet outil a permis de décrire quantitativement les premières courbes de Wohler en fretting à amorçage (Effort de fretting vs Nombre de cycles à amorçage) pour deux configurations de contact (cylindre/plan et plan/plan). Les impacts des différents paramètres de fretting sur l'amorcage ont pu être quantifies. Les paramètres influant sont : la configuration du contact, les niveaux des efforts appliques et leur mode de combinaison (cycles en phase ou cycles de type vol). De plus des courbes de cinétique de propagation des fissures ont pu être extraites des différents essais, montrant un fort impact du fretting sur les vitesses de propagation des fissures. Une analyse qualitative via l'émission acoustique a montré un mécanisme d'amorçage et de propagation en 3 étapes suivant la perte d'influence du contact. Un modèle de prédiction de l'amorçage et de simulation de la propagation des fissures a été mis en place. Bien que limite dans la prise en compte des effets gradients (approches non locales), ce modèle se montre très performant surtout dans sa capacité à utiliser les données expérimentales dans l'identification des lois d'amorçage ou de propagation. Ce travail a donc permis d'importantes avancées dans la compréhension des mécanismes de fissuration et dans leur modélisation ouvrant ainsi la porte vers une prédiction fiable de l'endommagement des contacts aube/disque.
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BARRE, Olivier. "Contribution à l'étude des formulations de calcul de la force magnétique en magnétostatique, approche numérique et validation expérimentale." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2003. http://tel.archives-ouvertes.fr/tel-00005921.
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Ce mémoire présente une étude des méthodes de calcul de la force engendrée par les champs magnétiques sur les matériaux linéaires en magnétostatique et se propose d'en comparer les performances sur les matériaux de faibles perméabilité. Les démonstrations de ces méthodes sont abordées et les hypothèses mises en évidence. Pour discriminer les formulations, courants équivalents, masses magnétiques équivalentes, tenseur de Maxwell, dérivée de l'énergie, une expérience et les mesures associées sont conçues par calcul de champ. Un matériau spécifique, de faible module d'élasticité est également synthétisé. Plongé dans un champ magnétique, un volume de test de ce matériau se déforme. Chaque formulation permet d'obtenir une répartition des contraintes sur le volume. Pour chaque répartition, la déformation du volume est calculée. Chaque déformation est comparée à celle qui est obtenue expérimentalement. Il apparaît que les méthodes énergétiques sont les plus précises.
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Matulík, Martin. "Modelování a animace biologických struktur." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377662.
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Following work deals with subject matter of digital modelling and animation of biological structures. Software tools for computer generated images (CGI), well proven in common practice, are evaluated, as well as tools for specific activities, available inside chosen software environment. Among vast pool of modelling approaches are discussed tools suitable for creation and representation of selected structures, along with tools essential for their consequent animation. Possible rendering approaches and their parameters in relation to qualities of resulting computer-generated images are discussed as well. Above-mentioned approaches will be consequently utilized for modelling, physical simulation and animation of erythrocyte’s flow throughout blood vessel in following project. Resulting output of that work will be based on series of digital images, suitable for creating video-sequence containing abovementioned animation in end-user digestible form.
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Jiang, Shuang. "Bacterial leaching from dairy shed effluent applied to a fine sandy loam under flood and spray irrigations." Lincoln University, 2008. http://hdl.handle.net/10182/668.
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Land application of wastes has become increasingly popular, to promote nutrient recycling and environmental protection, with soil functioning as a partial barrier between wastes and groundwater. Dairy shed effluent (DSE), may contain a wide variety of pathogenic micro-organisms, including bacteria (e.g. Salmonella paratyphyi, Escherichia coli. and Campylobacter), protozoa and viruses. Groundwater pathogen contamination resulting from land-applied DSE is drawing more attention with the intensified development of the dairy farm industry in New Zealand. The purpose of this research was to investigate the fate and transport of bacterial indicator-faecal coliform (FC) from land-applied DSE under different irrigation practices via field lysimeter studies, using two water irrigation methods (flood and sprinkler) with contrasting application rates, through the 2005-2006 irrigation season. It was aimed at better understanding, quantifying and modelling of the processes that govern the removal of microbes in intact soil columns, bridging the gap between previous theoretical research and general farm practices, specifically for Templeton soil. This study involved different approaches (leaching experiments, infiltrometer measurements and a dye infiltration study) to understand the processes of transient water flow and bacterial transport; and to extrapolate the relationships between bacterial transport and soil properties (like soil structure, texture), and soil physical status (soil water potential ψ and volumetric water content θ). Factors controlling FC transport are discussed. A contaminant transport model, HYDRUS-1D, was applied to simulate microbial transport through soil on the basis of measured datasets. This study was carried out at Lincoln University’s Centre for Soil and Environmental Quality (CSEQ) lysimeter site. Six lysimeters were employed in two trials. Each trial involved application of DSE, followed by a water irrigation sequence applied in a flux-controlled method. The soil columns were taken from the site of the new Lincoln University Dairy Farm, Lincoln, Canterbury. The soil type is Templeton fine sandy loam (Udic-Ustochrept, coarse loamy, mixed, mesic). Vertical profiles (at four depths) of θ and ψ were measured during leaching experiments. The leaching experiments directly measured concentrations of chemical tracer (Br⁻ or Cl⁻) and FC in drainage. Results showed that bacteria could readily penetrate through 700 mm deep soil columns, when facilitated by water flow. In the first (summer) trial, FC in leachate as high as 1.4×10⁶ cfu 100 mL⁻¹ (similar to the DSE concentration), was detected in one lysimeter that had a higher clay content in the topsoil, immediately after DSE application, and before any water irrigation. This indicates that DSE flowed through preferential flow paths without significant treatment or reduction in concentrations. The highest post-irrigation concentration was 3.4×10³ cfu 100 mL⁻¹ under flood irrigation. Flood irrigation resulted in more bacteria and Br⁻ leaching than spray irrigation. In both trials (summer and autumn) results showed significant differences between irrigation treatments in lysimeters sharing similar drainage class (moderate or moderately rapid). Leaching bacterial concentration was positively correlated with both θ and ψ, and sometimes drainage rate. Greater bacterial leaching was found in the one lysimeter with rapid whole-column effective hydraulic conductivity, Keff, for both flood and spray treatments. Occasionally, the effect of Keff on water movement and bacterial transport overrode the effect of irrigation. The ‘seasonal condition’ of the soil (including variation in initial water content) also influenced bacterial leaching, with less risk of leaching in autumn than in summer. A tension infiltrometer experiment measured hydraulic conductivity of the lysimeters at zero and 40 mm suction. The results showed in most cases a significant correlation between the proportion of bacteria leached and the flow contribution of the macropores. The higher the Ksat, the greater the amount of drainage and bacterial leaching obtained. This research also found that this technique may exclude the activity of some continuous macropores (e.g., cracks) due to the difference of initial wetness which could substantially change the conductivity and result in more serious bacterial leaching in this Templeton soil. A dye infiltration study showed there was great variability in water flow patterns, and most of the flow reaching deeper than 50 cm resulted from macropores, mainly visible cracks. The transient water flow and transport of tracer (Br⁻) and FC were modelled using the HYDRUS-1D software package. The uniform flow van Genuchten model, and the dual-porosity model were used for water flow and the mobile-immobile (MIM) model was used for tracer and FC transport. The hydraulic and solute parameters were optimized during simulation, on the basis of measured datasets from the leaching experiments. There was evidence supporting the presence of macropores, based on the water flow in the post-DSE application stage. The optimised saturated water content (θs) decreased during the post-application process, which could be explained in terms of macropore flow enhanced by irrigation. Moreover, bacterial simulation showed discrepancies in all cases of uniform flow simulations at the very initial stage, indicating that non-equilibrium processes were dominant during those short periods, and suggesting that there were strong dynamic processes involving structure change and subsequently flow paths. It is recommended that management strategies to reduce FC contamination following application of DSE in these soils must aim to decrease preferential flow by adjusting irrigation schemes. Attention needs to be given to a) decreasing irrigation rates at the beginning of each irrigation; b) increasing the number of irrigations, by reducing at the same time the amount of water applied and the irrigation rate at each irrigation; c) applying spray irrigation rather than flood irrigation.
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Saint-Cyr, Baptiste. "Modélisation des matériaux granulaires cohésifs à particules non convexes : Application à la compaction des poudres d'UO2." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2011. http://tel.archives-ouvertes.fr/tel-00660146.
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On s'intéresse à la modélisation des matériaux granulaires composé d'agrégats non convexes et cohésifs en vue d'application à la rhéologie des poudres d'UO2 . L'influence du degré de non-convexité des particules est analysé en termes de grandeurs macroscopiques (frottement interne et cohésion de Coulomb) et de paramètres micro-mécaniques tels que l'anisotropie de la texture et la transmission des efforts. Il apparaît en particulier que la compacité évolue d'une manière complexe avec la non-convexité et que la résistance au cisaillement augmente mais sature sous l'effet d'imbrication entre agrégats. Des modèles simples sont introduits pour décrire ces comportements en termes de paramètres micro-mécaniques. De même, des études systématiques par cisaillement, compaction uniaxiale et compression simple montrent que la cohésion interne augmente avec la non-convexité mais est fortement contrôlée par les conditions aux limites et l'apparition de bandes de cisaillement ou de concentrations de contraintes.
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Yi, Meng-Han, and 易孟函. "Hierarchical Linear Modeling Analysis of Physical Education Teacher’s Work Context and Teaching Self-efficacy." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/92626035281542985329.
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碩士國立聯合大學
資訊與社會研究所
101
With the activities of education reform actions in Taiwan, Health and Physical Education is classified as an independent field. Physical Education will play an important role. Over the past ten years of research on junior high school physical education teacher's appraisal, a number of issues have appeared, some of which remain controversial in spite of reams of data on junior high school physical education teacher's appraisal. Previous studies focus on physical education teacher appraisal indicator, teaching evaluation and professional performance. Recently there has been a shift in attention from a focus on junior high school physical education teacher's appraisal to an emphasis on improving junior high school physical education teacher's efficacy. Work context is an ability about the perception of physical education teacher to control organization context. It is the environmental factors of teaching self-efficacy. Physical education teachers’ professional is teachers' personal characteristics. It affects the difference of teaching self-efficacy of physical education teacher. Previous studies focus on the Overall performance of teaching self-efficacy, and ignore the interactive effects of personal teaching efficacy and general teaching efficacy. In addition, past studies explore the impact of physical education teachers teaching efficacy factors still take individual-level logical way that leads to results with hierarchical bias. This study considers the nested structure of teachers and schools, and the different levels of the factors included in the same study structure were discussed. This study use cross-level analysis through questionnaires to collect Work Context, Physical Education Teachers’ Professional, Personal Teaching Efficacy, and General Teaching Efficacy. And this study use the organizational level’s work context to explore the context influence the individual level’s PTE and GTE. Next, this study explores the interactive effects between PTE and GTE, and the effects between Physical Education Teachers’ Professional, PTE and GTE. This research was conducted through literature review, to establish the theoretical basis and according to the preparation "Junior high school physical education teachers teaching self-efficacy questionnaire." Questionnaire survey is expected to analyze the number of classes of 70 or more classes of junior high school, received a total of 36 schools in the country samples and 301 valid questionnaires physical education teachers, and use the hierarchical linear model for authentication. The study found that Work Context affects PTE and GTE, thus establishing the antecedents of organizational level is also a future reference for evaluation indicators of teacher professional development. In addition, PTE and GTE influence each other, which verify they are the important intension of teaching self-efficacy.
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"Modeling Mechanisms of Water Affinity and Condensation on Si-based Surfaces via Experiments and Applications." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.8870.
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abstract: Water affinity and condensation on Si-based surfaces is investigated to address the problem of fogging on silicone intraocular lenses (IOL) during cataract surgery, using Si(100), silica (SiO2) and polydimethylsiloxane (PDMS) silicone (SiOC2H6)n. Condensation is described by two step nucleation and growth where roughness controls heterogeneous nucleation of droplets followed by Ostwald ripening. Wetting on hydrophilic surfaces consists of continuous aqueous films while hydrophobic surfaces exhibit fogging with discrete droplets. Si-based surfaces with wavelength above 200 nm exhibit fogging during condensation. Below 200 nm, surfaces are found to wet during condensation. Water affinity of Si-based surfaces is quantified via the surface free energy (SFE) using Sessile drop contact angle analysis, the Young-Dupré equation, and Van Oss theory. Topography is analyzed using tapping mode atomic force microscopy (TMAFM). Polymer adsorption and ion beam modification of materials (IBMM) can modify surface topography, composition, and SFE, and alter water affinity of the Si-based surfaces we studied. Wet adsorption of hydroxypropyl methylcellulose (HPMC) C32H60O19 with areal densities ranging from 1018 atom/cm2 to 1019 atom/cm2 characterized via Rutherford backscattering spectrometry (RBS), allows for the substrate to adopt the topography of the HPMC film and its hydrophilic properties. The HPMC surface composition maintains a bulk stoichiometric ratio as confirmed by 4.265 MeV 12C(α, α)12C and 3.045 MeV 16O(α, α)16O, and 2.8 MeV He++ elastic recoil detection (ERD) of hydrogen. Both PIXE and RBS methods give comparable areal density results of polymer films on Si(100), silica, and PDMS silicone substrates. The SFE and topography of PDMS silicone polymers used for IOLs can also be modified by IBMM. IBMM of HPMC cellulose occurs during IBA as well. Damage curves and ERD are shown to characterize surface desorption accurately during IBMM so that ion beam damage can be accounted for during analysis of polymer areal density and composition. IBMM of Si(100)-SiO2 ordered interfaces also induces changes of SFE, as ions disorder surface atoms. The SFE converges for all surfaces, hydrophobic and hydrophilic, as ions alter electrochemical properties of the surface via atomic and electronic displacements.Dissertation/Thesis
Ph.D. Physics 2011