Dissertations / Theses on the topic 'Modeling analyses'

In recent years, the concept of safety barriers has become increasingly popular in regulations and standards for the offshore oil and gas industry, both in Norway and internationally. There are requirements from the Petroleum Safety Authority Norway and operators in the oil and gas industry that the condition of both technical and human/organizational safety barriers on installations should be reflected in risk analyses. However, implementing this in a manner which supports appropriate analysis- and decision making processes has proved to be difficult. The peformance of barriers is often not explicitly modeled in analyses, and human/organizational aspects are often not addressed in detail. This master thesis examines how safety barriers can be modeled in risk analyses, and to which level of detail this can be achieved. A comprehensive literature review is performed in order to examine how the concept of safety barriers is defined, and which barrier properties are used to categorize and measure the performance of barriers. In addition, relevant standards and guidelines for the offshore oil and gas industry are reviewed in order to identify which barriers are important for offshore operations. A brief case study of blowouts is performed to illustrate how safety barriers are implemented on oil and gas installations.Methods and techniques for modeling safety barriers in risk analyses are reviewed and presented. The different objectives of risk analysis, and the relevant barrier properties for risk analyses, are discussed. The tools developed in "Barrier and Operational Risk Analysis", "Hybrid Causal Logic in Offshore Risk Analysis" and "Risk Modelling - Integration of Organizational, Human and Technical Factors" are included in the discussion. The current approach for quantitative risk analysis in DNV is presented briefly. Based on these discussions, two main suggestions for improvement are identified:1. Include relevant barrier functions for each scenario as events in event tree models.2. When appropriate and practicable, the technical and human/organizational condition of barriers should be taken into account using fault tree and/or Risk Influence Diagram/ Bayesian Belief Network models.Safety barriers should be included more consistently in event trees in order to better illustrate the effect of barriers on major accident risk, and to allow for explicit modeling of the barrier systems implemented to perform each barrier function. Fault tree and bayesian belief network analysis can be applied to model both the technical and human/organizational condition of barrier systems.It is suggested that simplified methods for adjusting industry average probabilities are applied for the modeling of risk influencing factors. Because of the massive workload and amount of data required for detailed statistical modeling of each risk influencing factor, these simplified methods are considered to be a more feasible alternative.While it may seem inappropriate to tamper with probabilities which are based on historical data, it is important to consider whether the historical data accurately reflects the object under analysis. If conditions differ from the industry average, industry average numbers will not reflect the reality of the specific installation. Using adjusted probabilities will be particularly useful when barriers are found to be in worse condition than than the industry average, because this means the average frequencies will be artificially optimistic. In this case, an adjusted probability will be a conservative estimate.It should be noted that the energy-barrier perspective has received criticism from some researchers because it is based on linear causal chains, and does not account for complex interactions in larger socio-technical systems. While the approach does have its shortcomings, methods based on the barrier approach have proved to be useful and suitable for a number of applications. The approach is also continuously improved, as manifested by the introduction of bayesian belief networks in traditional risk analysis.

The safety of nuclear power plants must be proved, certified and improved. Probabilistic safety assessments are used to estimate the core meltdown risk, by means of sequential analyses of accidents. In order to assess probabilities of the appearance of these sequences, it is necessary to specifically assess probabilities of operation failures accomplished by human operators in a degraded mode. For this purpose, EDF, the French producer of electricity, developed a method that models failures of human actions, by means of a systematic determination of scenarios corresponding to different failure modes.

This method, called MERMOS, has been used for several probabilistic safety assessments. In order to increase its reproducibility and to make it more robust, example missions and scenarios will be built. This set of example analyses will be used by experts assessing human reliability: they will develop studies and deduce results more easily.

The purpose of this study involves the creation of a methodology to model existing analyses and human reliability data used in MERMOS. This study consists of optimizing a second generation human reliability assessment method in order to overpass its current weaknesses in an operational context by means of the identification of a set of example analyses.
Master of Science

Extreme rainfall events and consequent floods are being observed more frequently in the Western Black Sea region in Turkey as climate changes. In this study, application of a flood early warning system is intended by using and calibrating a combined model system. A regional-scale hydro-meteorological model system, consisting of Weather Research and Forecasting (WRF) model, NOAH land surface model and fully distributed NOAH-Hydro hydrologic models, is used for simulations of 25 heavy-rainfall and major flooding events observed in the Western Black Sea region between years 2000 and 2011. The performance of WRF model system in simulating precipitation is tested with 3-dimensional variational (3DVAR) data assimilation scheme. WRF-derived precipitation with and without data assimilation and Multi Precipitation Estimates (MPE) are used in NOAH-Hydro model to simulate streamflow for flood events. Statistical precipitation analyses show that WRF model with 3DVAR improved precipitation up to 12% with respect to no-assimilation. MPE algorithm generally underestimates rainfall and it also showed lower performance than WRF model with and without data assimilation. Depending on reliability of precipitation inputs, NOAH-Hydro model produces reasonable flood hydrographs both in structure and volume. After model calibration is performed using assimilated precipitation inputs in Bartin Basin, NOAH-Hydro model reduced the average error in streamflow by 23.24% and 53.57% with calibration for testing events. With calibrated parameters, NOAH-Hydro model forced by WRF non-assimilated precipitation input also reduced the error in streamflow but with lower rates (16.67% and 40.72%). With a proper model calibration and reliable precipitation inputs, hydrologic modeling system is capable of simulating flood events.

This thesis is concerned with the development of Bayesian inference approach for the analysis of infectious disease models. Stochastic SIS household-based epidemic models were considered with individuals allowed to be contracted locally at a given rate and there also exists a global force of infection. The study covers both when the population of interest is assumed to be constant and when the population is allowed to vary over time. It also covers when the global force of infection is constant and when it is spatially varying as a function of some unobserved Gaussian random fields realizations. In addition, we also considered diseases coinfection models allowing multiple strains transmission and recovery. For each model, Bayesian inference approach was developed and implemented via MCMC framework using extensive data augmentation schema. Throughout, we consider two most prevalent forms of endemic disease data- the individual-based data and the aggregate-based data. The models and Bayesian approach were tested with simulated data sets and successfully applied to real-life data sets of tick-borne diseases among Tanzania cattle.

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 84-89).
Vapor intrusion is the migration of volatile organic compounds (VOCs) from a subsurface source into the indoor air of an overlying building. Vapor intrusion models, including the Johnson and Ettinger (J&E) model, can be used to predict the concentration of VOCs in the indoor air of a building based on a measured subsurface soil gas concentration or contaminant source concentrations, either in non-aqueous phase liquid (NAPL), groundwater, or soil. An analysis of two of the EPA-implemented J&E spreadsheet models, one that considers subsurface soil gas data and one that considers groundwater data, was conducted. The governing equations, assumptions, and limitations of these spreadsheet models were investigated. A value of information (Vol) worksheet was developed that can assist practitioners in deciding what additional data to collect as part of a remedial investigation. The Vol worksheet calculates how varying values of model input parameters affect the model-predicted indoor air carcinogenic risk. The worksheet then compares the user-defined target risk to the range of potential risk values for different combinations of varying parameters. The results of this analysis allow the user to determine which groups of parameters have the most impact on the model results. This information can assist the practitioner in deciding whether or not to collect additional data to reduce the uncertainty in the input parameters. The EPA J&E soil gas and groundwater spreadsheet models, as well as the Vol worksheet developed for each model, were applied to case study data for a trichloroethylene-impacted site in Rhode Island. The results of the J&E model and Vol worksheet analyses for this case study predicted incremental carcinogenic risk values for trichloroethylene (TCE) below the risk value calculated based on measured indoor air data. This comparison suggests the potential for other sources of TCE within the building. Groups of parameters were identified for each model that impacted the model-predicted carcinogenic risk. The development of a cost-benefit analysis, which would be used to quantify the value of obtaining additional data for these critical parameters, is recommended for future research.
by Jessica M. Friscia.
M. Eng.

The transport and urban economics literature applies different labor supply approaches when studying economic or planning instruments. Some studies assume that working hours are endogenous while the number of workdays is given, whereas others model only decisions on workdays. Unfortunately, empirical evidence does hardly exist on account of missing data. Against this background, we provide an assessment of whether general effects of transport policies are robust against the modeling of leisure demand and labor supply. We introduce different labor supply approaches into a spatial general equilibrium model and discuss how they affect the welfare implication of congestion policies. We, then, perform simulations and find that in many cases the choice of labor supply modeling not only affects the magnitude of the policy impact but also its direction. While planning instruments are suggested to be quite robust to different labor supply approaches, the way of modeling labor supply may crucially affect the overall welfare implications of economic instruments such as congestion tolls. Based on these findings it becomes clear which labor supply approach is the most appropriate given specific conditions. Our study also emphasizes the need for better micro labor market data that also feature days of sickness, overtime work used to reduce workdays, the actual number of leave days, part-time work, days with telecommuting etc.

Gusset plate connections are commonly used in steel truss bridges to connect individual members together at a node. Many of these bridges are classified as non-load-path-redundant bridges, meaning a failure of a single truss member or connection could lead to collapse. Current gusset plated design philosophy is based upon experimental work from simplified, small-scale connections which are seldom representative of bridge connections. This makes development of a refined methodology for conducting high-fidelity strength capacity evaluations for existing bridge connections a highly desirable goal. The primary goal of this research effort is to develop an analytical model capable of evaluating gusset plate stresses and ultimate strength limit states. A connection-level gusset connection model was developed in parallel with an experimental testing program at Oregon State University. Data was collected on elastic stress distributions and ultimate buckling capacity. The analytical model compared different bolt modeling techniques on their effectiveness in predicting buckling loads and stress distributions. Analytical tensile capacity was compared to the current bridge gusset plate design equations for block shear. Results from the elastic stress analysis showed no significant differences between the bolt modeling techniques examined, and moderate correlation between analytical and experimental values. Results from the analytical model predicted experimental buckling capacity within 10% for most of the bolt modeling techniques examined. Tensile capacity was within 7% of the calculated tensile nominal capacity for all bolt modeling techniques examined. A preliminary parametric study was conducted to investigate the effects of member flexural stiffness and length on gusset plate buckling capacity, and showed an increase in member length or decrease in member flexural stiffness resulted in diminished gusset plate buckling capacity.

Future microprocessor poses many challenges to its dedicated power supplies, the voltage regulators (VRs), such as the low voltage, high current, fast load transient, etc. For the VR designs using multiphase buck converters, one of the results from these stringent challenges is a large amount of output capacitors, which is undesired from both a cost and a motherboard real estate perspective. In order to save the output capacitors, the control-loop bandwidth must be increased. However, the bandwidth is limited in the practical design. The influence from the switching frequency on the control-loop bandwidth has not been identified, and the influence from multiphase is not clear, either. Since the widely-used average model eliminates the inherent switching functions, it is not able to predict the converter's high-frequency performance. In this dissertation, the primary objectives are to develop the methodology of high-frequency modeling for the buck and multiphase buck converters, and to analyze their high-frequency characteristics. First, the nonlinearity of the pulse-width modulator (PWM) scheme is identified. Because of the sampling characteristic, the sideband components are generated at the output of the PWM comparator. Using the assumption that the sideband components are well attenuated by the low-pass filters in the converter, the conventional average model only includes the perturbation-frequency components. When studying the high-frequency performance, the sideband frequency is not sufficiently high as compared with the perturbation one; therefore, the assumption for the average model is not good any more. Under this condition, the converter response cannot be reflected by the average model. Furthermore, with a closed loop, the generated sideband components at the output voltage appear at the input of the PWM comparator, and then generate the perturbation-frequency components at the output. This causes the sideband effect to happen. The perturbation- frequency components and the sideband components are then coupled through the comparator. To be able to predict the converter's high-frequency performance, it is necessary to have a model that reflects the sampling characteristic of the PWM comparator. As the basis of further research, the existing high-frequency modeling approaches are reviewed. Among them, the harmonic balance approach predicts the high-frequency performance but it is too complicated to utilize. However, it is promising when simplified in the applications with buck and multiphase buck converters. Once the nonlinearity of the PWM comparator is identified, a simple model can be obtained because the rest of the converter system is a linear function. With the Fourier analysis, the relationship between the perturbation-frequency components and the sideband components are derived for the trailing-edge PWM comparator. The concept of multi-frequency modeling is developed based on a single-phase voltage-mode-controlled buck converter. The system stability and transient performance depend on the loop gain that is affected by the sideband component. Based on the multi-frequency model, it is mathematically indicated that the result from the sideband effect is the reduction of magnitude and phase characteristics of the loop gain. With a higher bandwidth, there are more magnitude and phase reductions, which, therefore, cause the sideband effect to pose limitations when pushing the bandwidth. The proposed model is then applied to the multiphase buck converter. For voltage-mode control, the multiphase technique has the potential to cancel the sideband effect around the switching frequency. Therefore, theoretically the control-loop bandwidth can be pushed higher than the single-phase design. However, in practical designs, there is still magnitude and phase reductions around the switching frequency in the measured loop gain. Using the multi-frequency model, it is clearly pointed out that the sideband effect cannot be fully cancelled with unsymmetrical phases, which results in additional reduction of the phase margin, especially for the high-bandwidth design. Therefore, one should be extremely careful to push the bandwidth when depending on the interleaving to cancel the sideband effect. The multiphase buck converter with peak-current control is also investigated. Because of the current loop in each individual phase, there is the sideband effect that cannot be canceled with the interleaving technique. For higher bandwidths and better transient performances, two schemes are presented to reduce the influence from the current loop: the external ramps are inserted in the modulators, and the inductor currents are coupled, either through feedback control or by the coupled-inductor structure. A bandwidth around one-third of the switching frequency is achieved with the coupled-inductor buck converter, which makes it a promising circuit for the VR applications. As a conclusion, the feedback loop results in the sideband effect, which limits the bandwidth and is not included in the average model. With the proposed multi-frequency model, the high-frequency performance for the buck and multiphase buck converters can be accurately predicted.
Ph. D.

Diese Forschung zielt darauf ab, den Einsatz realistischer Mineralmikrostrukturen in Mineralverarbeitungssimulationen Simulationen von Aufbereitungsprozessen zu ermöglichen. Insbesondere Zerkleinerungsprozesse, wie z.B. das Brechen und Mahlen von mineralischen Rohmaterialien, werden stark von der mineralischen Mikrostruktur beeinflusst, da die Textur und die Struktur der vielen Körner und ihre mikromechanischen Eigenschaften das makroskopische Bruchverhalten bestimmen. Ein Beispiel: Stellen wir uns vor, wir haben ein mineralisches Material, das im Wesentlichen aus Körnern zweier verschiedener Mineralphasen, wie Quarz und Feldspat, besteht. Wenn die mikromechanischen Eigenschaften dieser beiden Phasen unterschiedlich sind, wird sich dies wahrscheinlich auf das makroskopische Bruchverhalten auswirken. Unter der Annahme, dass die Körner eines der Minerale bei geringeren Belastungen brechen, ist es wahrscheinlich, dass sich ein Riss durch einen Stein dieses Materials durch die schwächeren Körner ausbreitet. Tatsächlich ist dies eine wichtige Eigenschaft für die Erzaufbereitung. Um wertvolle Mineralien aus einem Erz zu gewinnen, ist es wichtig, sie aus dem kommerziell wertlosen Material, in dem sie vorkommen, zu befreien. Dazu ist es wichtig zu wissen und zu verstehen, wie das Material auf Korngrößenebene bricht. Um diesen Bruch simulieren zu können, ist es wichtig, realistische Modelle der mineralischen Mikrostrukturen zu verwenden. Diese Studie zeigt, wie solche realistischen zweidimensionalen Mikrostrukturen auf der Grundlage der quantitativen Mikrostrukturanalyse am Computer erzeugt werden können. Darüber hinaus zeigt die Studie, wie diese synthetischen Mikrostrukturen dann in die gut etablierte Diskrete-Elemente-Methode integriert werden können, bei der der Bruch von mineralischem Material auf Korngrößenebene simuliert werden kann.:List of Acronyms VII List of Latin Symbols IX List of Greek Symbols XV 1 Introduction 1 1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1 1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4 1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7 2 Background 9 2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9 2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21 2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26 2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29 2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29 2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49 2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49 3 Synthesis of realistic mineral microstructures for DEM simulations 51 3.1 Development of a computer-assisted QMA for the analysis of real and synthetic mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53 3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54 3.1.3 The conversion of a given real mineral microstructure into a false-color image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59 3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.1.6 Summary of the principles of the adapted Quantitative Microstructural Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71 3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76 3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77 XVIII List of Greek Symbols 3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81 3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85 3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89 3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90 3.4.2 Procedure for generating a realistic synthetic microstructure of a given real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 Validation of the synthesis approach 103 4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103 4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108 4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109 4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114 4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127 4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138 4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139 4.3.2 Realization and evaluation of the real extended indenter test . . . . 142 4.3.3 Realization and evaluation of the simulated extended indenter test . 154 4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171 4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173 4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176 4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188 4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203 5 Conclusions and directions for future development 205 6 References 211 List of Figures 229 List of Tables 235 Appendix 237
This research aims to make it possible to use realistic mineral microstructures in simulations of mineral processing. In particular, comminution processes, such as the crushing and grinding of raw mineral materials, are highly aff ected by the mineral microstructure, since the texture and structure of the many grains and their micromechanical properties determine the macroscopic fracture behavior. To illustrate this, consider a mineral material that essentially consists of grains of two diff erent mineral phases, such as quartz and feldspar. If the micromechanical properties of these two phases are diff erent, this will likely have an impact on the macroscopic fracture behavior. Assuming that the grains of one of the minerals break at lower loads, it is likely that a crack through a stone of that material will spread through the weaker grains. In fact, this is an important property for ore processing. In order to extract valuable minerals from an ore, it is important to liberate them from the commercially worthless material in which they are found. For this, it is essential to know and understand how the material breaks at grain-size level. To be able to simulate this breakage, it is important to use realistic models of the mineral microstructures. This study demonstrates how such realistic two-dimensional microstructures can be generated on the computer based on quantitative microstructural analysis. Furthermore, the study shows how these synthetic microstructures can then be incorporated into the well-established discrete element method, where the breakage of mineral material can be simulated at grain-size level.:List of Acronyms VII List of Latin Symbols IX List of Greek Symbols XV 1 Introduction 1 1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1 1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4 1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7 2 Background 9 2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9 2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21 2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26 2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29 2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29 2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49 2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49 3 Synthesis of realistic mineral microstructures for DEM simulations 51 3.1 Development of a computer-assisted QMA for the analysis of real and synthetic mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53 3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54 3.1.3 The conversion of a given real mineral microstructure into a false-color image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59 3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.1.6 Summary of the principles of the adapted Quantitative Microstructural Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71 3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76 3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77 XVIII List of Greek Symbols 3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81 3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85 3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89 3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90 3.4.2 Procedure for generating a realistic synthetic microstructure of a given real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 Validation of the synthesis approach 103 4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103 4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108 4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109 4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114 4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127 4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138 4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139 4.3.2 Realization and evaluation of the real extended indenter test . . . . 142 4.3.3 Realization and evaluation of the simulated extended indenter test . 154 4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171 4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173 4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176 4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188 4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203 5 Conclusions and directions for future development 205 6 References 211 List of Figures 229 List of Tables 235 Appendix 237

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第16901号
農博第1917号
新制||農||998(附属図書館)
学位論文||H24||N4662(農学部図書室)
29576
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 河地 利彦, 教授 村上 章, 教授 川島 茂人
学位規則第4条第1項該当

This study identified the relationships of student engagement with senior student satisfaction and perceived employability skills from STEM fields in the U.S. A comparison of the relationships of student engagement, student satisfaction, and perceived employability skills was made across senior Asian international students and their American peers in STEM programs. The National Study of Student Engagement (NSSE) data (2011) was used in this study. Structural equation modeling analyses and invariance tests were employed to estimate different models of student engagement, student satisfaction, and perceived employability skills across different samples. The results found that both sense of support and relationships with others of emotional engagement were found the most important constructs to predict college student satisfaction and perceived employability skills. The cognitive engagement had a significant positive effect on student perceived employability skills across all college students, Asian international students, and American students in STEM education. Moreover, this study identified the mediator role of student perceived employability skills on the relationship between student engagement and student satisfaction for all three samples. Additionally, Asian international students differed from American students regarding academic involvement, participating in extracurricular activities, and sense of support in STEM education. Last but not least, this study supported that the three-dimension student engagement model developed by Fredricks et al. (2004) could apply to U.S. college students. Practical and theoretical implications were discussed and limitations acknowledged.
Doctor of Philosophy
It is widely accepted that attracting STEM talents to the U.S. is a key element to maintain the United States' economic supremacy and competitive advantage in a global economy. Asian international students play a significant role to maintain a steady supply of STEM talent pipelines in the U.S. job market. The purpose of this study is to understand the relationships of student engagement with senior student satisfaction and perceived employability skills from STEM fields in the U.S. This study This study was also to identify the relationships of student engagement, student satisfaction, and perceived employability skills across senior Asian international students and their American peers in STEM programs. The results found that both sense of support and relationships with others of emotional engagement were the most important factors to predict college student satisfaction and perceived employability skills. Cognitive engagement had a significant positive influence on student perceived employability skills across all college students, Asian international students, and American students in STEM education. Moreover, this study identified the mediator role of student perceived employability skills on the relationship between student engagement and student satisfaction. Additionally, Asian international students differed from American students regarding academic involvement, participating in extracurricular activities, and sense of support in STEM education. Last but not least, this study supported that the three-dimension student engagement model could apply to U.S. college students. Practical and theoretical implications were discussed and limitations acknowledged.

The theme that binds together the four papers in this dissertation is the tracking of physical quantities of water used by industries in the economy, and an exploration of whether and how this tracking could be helpful in informing water policies, as applied to the state of Nevada or sub-regions of Nevada. The concept of water footprints has been wildly popular in disciplines outside of economics and has been used to help make policy decisions normally considered to lie within the economist's realm. Yet many economists shun 'footprints' in general and water footprints in particular, seeing them as descriptive methods that have little or nothing to add to policy analysis. This thesis attempts to bridge a gap between economists, engineers and planners and the popular imagination about what economic concepts footprints are related to and how they can best be used in policy analysis.

With the traditional fracture mechanics approaches, an initial crack and self-similar progression of cracks are assumed. In this treatise, theoretical and numerical tools are developed to mathematically describe non-self-similar progression of cracks without specifying an initial crack. A cohesive-decohesive zone model, similar to the cohesive zone model known in fracture mechanics as Dugdale-Barenblatt model, is adopted to represent the degradation of the material ahead of the crack tip. This model unifies strength-based crack initiation and fracture based crack progression. The cohesive-decohesive zone model is implemented with an interfacial surface material that consists of an upper and lower surface connected by a continuous distribution of normal and tangential nonlinear elastic springs that act to resist either Mode I opening, Mode II sliding, Mode III sliding, or mixed mode. The initiation of fracture is determined by the interfacial strength and the progression of fracture is determined by the critical energy release rate. The material between two adjacent laminae of a laminated composite structure or the material between the adherend and the adhesive is idealized with an interfacial surface material to predict interfacial fracture. The interfacial surface material is positioned within the bulk material to predict discrete cohesive cracks. The proper work-conjugacy relations between the stress and deformation measures are identified for the interfacial surface theory. In the principle of virtual work, the interfacial cohesive-decohesive tractions are conjugate to the displacement jumps across the upper and lower surfaces. A finite deformation kinematics theory is developed for the description of the upper and lower surface such that the deformation measures are invariant with respect to superposed rigid body translation and rotation. Various mechanical softening constitutive laws thermodynamically consistent with damage mechanics are postulated that relate the interfacial tractions to the displacement jump. An exponential function is used for the constitutive law such that it satisfies a multi-axial stress criterion for the onset of delamination, and satisfies a mixed mode fracture criterion for the progression of delamination. A damage parameter is included to prevent the restoration of the previous cohesive state between the interfacial surfaces. In addition, interfacial constitutive laws are developed to describe the contact-friction behavior. Interface elements applicable to two dimensional and three dimensional analyses are formulated for the analyses of contact, friction, and delamination problems. The consistent form of the interface element internal force vector and the tangent stiffness matrix are considered in the formulation. We investigate computational issues related to interfacial interpenetration, mesh sensitivity, the number of integrations points and the integration scheme, mathematical form of the softening constitutive law, and the convergence characteristics of the nonlinear solution procedure when cohesive-decohesive constitutive laws are used. To demonstrate the predictive capability of the interface finite element formulation, steadystate crack growth is simulated for quasi-static loading of various fracture test configurations loaded under Mode I, Mode II, Mode III, and mixed-mode loading. The finite element results are in agreement with the analytical results available in the literature and those developed in this work. A progressive failure methodology is developed and demonstrated to simulate the initiation and material degradation of a laminated panel due to intralaminar and interlaminar failures. Initiation of intralaminar failure can be by a matrix-cracking mode, a fiber-matrix shear mode, and a fiber failure mode. Subsequent material degradation is modeled using damage parameters for each mode to selectively reduce lamina material properties. The interlaminar failure mechanism such as delamination is simulated by positioning interface elements between adjacent sublaminates. The methodology is validated with respect to experimental data available in the literature on the response and failure of quasi-isotropic panels with centrally located circular cutouts. Very good agreement between the progressive failure analysis and the experiments is achieved if the failure analyses includes the interaction of intralaminar and interlaminar failures in the postbuckling response of the panels. In addition, ideas concerning the implementation of a fatigue model incorporated with a cohesive zone model are discussed.
Ph. D.

The motivation for this thesis was the need for further development of multibody dynamics simulation packages focused on detailed contact analysis. The thesis makes contributions in three different areas: Part I summarizes the equations, algorithms and design decisions necessary for dynamics simulation of flexible bodies with moving contacts. The assumed general shape function approach is presented. Additionally, the described technique enables studies of the residual stress release during grinding of flexible bodies. The proposed set of mode shapes was also successfully applied for modeling of heat flow. Part II is motivated by the need to reduce the computation time. The availability of the new cost-efficient multiprocessor computers triggered the development of the presented hybrid parallelization framework. The framework is designed to be easily portable and can be implemented without any system level coding or compiler modifications. Part III is motivated by the need for inter-operation with other simulation tools. A co-simulation framework based on the Transmission Line Modeling (TLM) technology was developed. The framework enables integration of several different simulation components into a single time-domain simulation. The framework has been used for connecting MSC.ADAMS and SKF BEAST simulation models. Throughout the thesis the approach was to present a practitioner roadmap. The detailed description of the theoretical results relevant for a real software implementation is put in focus. The software design decisions are discussed and the results of real industrial simulations are presented. This work has been supported by SKF, SSF/ProViking, ECSEL, KK-stiftelsen.

In der vorliegenden Arbeit werden verschiedene Simulationsansätze angewandt um die Hydrodynamik in einem neu entwickelten Wirbelschichtvergaser zu untersuchen. Die Ansätze umfassen a) entdimensionalisierter Ähnlichkeitskennzahlen und empirischer Gleichungen, b) 1D Simulationen mittels ASPEN Plus®, c) 3D CFD Simulationen mittels Ansys Fluent® zur detaillierten Abbildung der zu erwartenden Hydrodynamik. Vor- und Nachteile der jeweiligen Ansätze sowie Klassen von ermittelbaren Simulationsdaten werden diskutiert. Ein Schwerpunkt der Arbeit liegt in der Identifizierung geeigneter Experimente aus der Literatur, auf Basis von Ähnlichkeitskennzahlen, um die Simulationen zu validieren. Die Vergasersimulationen zeigen, dass sich erwartungsgemäß ein aus hydrodynamischer Sicht gestufter Prozess ausbildet. Die entstehenden Zonen lassen sich als Festbett, blasenbildende Wirbelschicht, Jet-Wirbelschicht mit Rezirkulationszelle und strähnenbildende, zirkulierende Wirbelschicht identifizieren und entsprechen demnach dem Verfahrensanspruch.

Le suivi, le contrôle et la surveillance (MCS) des pêches marines sont des problèmes essentiels pour la gestion durable des ressources halieutiques. Dans cette thèse, nous étudions le suivi spatial des activités des navires de pêche en utilisant les données de trajectoire du système de surveillance des navires (VMS) dans le cadre du projet INDESO (2013-2017). Notre objectif général est de développer une chaîne de traitement des données VMS afin de: i) effectuer un suivi de l'effort de pêche des flottilles de palangriers indonésiens, ii) détecter les activités de pêche illégales et évaluer leur importance. L'approche proposée repose sur des modèles de mélange gaussien (GMM) et les modèles de Markov cachés (HMM), en vue d'identifier les comportements élémentaires des navires de pêche, tels que les voyages, la recherche et les activités de pêche, dans un cadre non supervisé. Nous considérons différentes paramétrisations de ces modèles avec une étude particulière des palangriers indonésiens, pour lesquels nous pouvons bénéficier de données d'observateurs embarqués afin de procéder à une évaluation quantitative des modèles proposés et testés.Nous exploitons ensuite ces modèles statistiques pour deux objectifs différents: a) la discrimination des différents flottilles de pêche à partir des trajectoires des navires de pêche et l'application à la détection et à l'évaluation des activités de pêche illégale, b) l'évaluation d'un effort de pêche spatialisé à partir des données VMS. Nous obtenons de très bons taux de reconnaissance (environ 97%) pour la première tâche et nos expériences soutiennent le potentiel d'une exploration opérationnelle de l'approche proposée. En raison du nombre limité de données d'observateurs embarqués, seules des analyses préliminaires on pu être effectuées pour l'estimation de l'effort de pêche à partir des données VMS. Au-delà des développements méthodologiques potentiels, cette thèse met l'accent sur l'importance de la qualité de données d'observation en mer représentatives pour développer davantage l'exploitation des données VMS tant pour la recherche que pour les questions opérationnelles
Monitoring, control and surveillance (MCS) of marine fisheries are critical issues for the sustainable management of marine fisheries. In this thesis we investigate the space-based monitoring of fishing vessel activities using Vessel Monitoring System (VMS) trajectory data in the context of INDESO project (2013-2017). Our general objective is to develop a processing chain of VMS data in order to: i) perform a follow-up of the fishing effort of the Indonesian longline fleets, ii) detect illegal fishing activities and assess their importance. The proposed approach relies on classical latent class models, namely Gaussian Mixture Models (GMM) and Hidden Markov Models (HMM), with a view to identifying elementary fishing vessel behaviors, such as travelling, searching and fishing activities, in a unsupervised framework. Following state-of-the-art approaches, we consider different parameterizations of these models with a specific focus on Indonesian longliners, for which we can benefit from at-sea observers¿ data to proceed to a quantitative evaluation. We then exploit these statistical models for two different objectives: a) the discrimination of different fishing fleets from fishing vessel trajectories and the application to the detection and assessment of illegal fishing activities, b) the assessment of a spatialized fishing effort from VMS data. We report good recognition rate (about 97%) for the former task and our experiments support the potential for an operational exploration of the proposed approach. Due to limited at-sea observers¿ data, only preliminary analyses could be carried out for the proposed VMS-derived fishing effort. Beyond potential methodological developments, this thesis emphasizes the importance of high-quality and representative at-sea observer data for further developing the exploitation of VMS data both for research and operational issues

FE-modeling is a rapidly spreading method to analyze structures nowadays. With this theunderstanding of the outcome is of very high importance and potential inaccuracies areimportant to find so that faulty and over dimensioning of the structure does not occur whichleads to unnecessary costs. One of these inaccuracies is the unrealistic sectional forces that occurdue to thermal effects in the transversal direction for concrete frame bridges which leads to anexcessive amount much reinforcement in the structure than actually needed. This has beenstudied with several cases by using two approaches on how to apply the temperature in the framebridge, only in the superstructure and in the whole structure, but also by analyzing severalboundary conditions. By examining the results for the sectional forces and stresses one of thetemperature approaches could be disregarded because of the extreme values in the transitionbetween superstructure and support. But the other approach was much more useful because ofits better compliance with reality. With these results and by calculating the reinforcement neededfor the worst case, one model has been found to be the most favorable and can be used whenmodeling concrete frame bridges with acceptable outcome. The study resulted in a model whereone applies a varying temperature on the whole structure, with spring boundary conditions over asurface that represents the bottom slab.

A partir de l’étude d’une structure composite multifonctionnelle prédéfinie, cette thèse a pour objectif l’analyse du comportement thermomécanique et des modes d’endommagement d’une structure composite intégrant des conducteurs électriques. Des éprouvettes représentatives sont fabriquées et testées sous différentes conditions mécaniques, thermiques et électriques. L’influence des chargements mécaniques hors-plan, et plus particulièrement d’un impact basse énergie, sur la fonctionnalité électromécanique de la structure est ensuite étudiée. Des mesures de résistance électrique et te tension de claquage sont réalisées afin de déterminer les performances électriques post-impact de la structure. L’échauffement résistif interne des conducteurs, conjugué à l’environnement thermique d’une structure aéronautique nous invite finalement à étudier le comportement thermomécanique de tels assemblages multicouches et multi-matériaux. Nous présentons donc une méthodologie de caractérisation du comportement thermomécanique d’un assemblage sandwich multicouche via l’analyse de ses composants pris séparément et caractérisés par des analyses mécaniques dynamiques (DMA). La contribution majeure de ce travail réside dans la détermination de critères de dégradation électrique, et de dimensionnement, pour le développement de structures composites intégrant des conducteurs électriques
From the study of a particular multifunctional composite structure, this thesis aims at analyzing the thermomechanical behavior and failure modes of a composite structure embedding electrical wires. Representative test specimens embedding flat electrical cables are manufactured and tested under various conditions. The influence of out-of-plane loadings, and especially of low energy impacts on the electro-mechanical functionality of the structure is then investigated with both experimental and numerical considerations. Post impact electrical tests such as resistance measurements and dielectric strength tests are carried out to investigate on the post-impact electrical performances of the structure. Then, resistive heating of the embedded electrical components combined to the thermal environment of an aerospace structure lead us to further investigate on the thermo-mechanical behaviour of such multi-layered multi-materials structures. Hence, a methodology using Dynamic Mechanical Analysis (DMA) testings is developed to characterize both the temperaturedependent stiffness of the constituents, and the resulting thermo-mechanical behaviour of the assembly. The main contribution of this work consists in determining electrical degradation and sizing criteria for the development of robust composite structures embedding electrical wires

Statistical analyses and modeling have contributed greatly to our understanding of the pathogenesis of HIV-1 infection; they also provide guidance for the treatment of AIDS patients and evaluation of antiretroviral (ARV) therapies. Various statistical methods, nonlinear mixed-effects models in particular, have been applied to model the CD4 and viral load trajectories. A common assumption in these methods is all patients come from a homogeneous population following one mean trajectories. This assumption unfortunately obscures important characteristic difference between subgroups of patients whose response to treatment and whose disease trajectories are biologically different. It also may lack the robustness against population heterogeneity resulting misleading or biased inference. Finite mixture models, also known as latent class models, are commonly used to model nonpredetermined heterogeneity in a population; they provide an empirical representation of heterogeneity by grouping the population into a finite number of latent classes and modeling the population through a mixture distribution. For each latent class, a finite mixture model allows individuals in each class to vary around their own mean trajectory, instead of a common one shared by all classes. Furthermore, a mixture model has ability to cluster and estimate class membership probabilities at both population and individual levels. This important feature may help physicians to better understand a particular patient disease progression and refine the therapeutical strategy in advance. In this research, we developed mixture dynamic model and related Bayesian inferences via Markov chain Monte Carlo (MCMC). One real data set from HIV/AIDS clinical management and another from clinical trial were used to illustrate the proposed models and methods. This dissertation explored three topics. First, we modeled the CD4 trajectories using a finite mixture model with four distinct components of which the mean functions are designed based on Michaelis-Menten function. Relevant covariates both baseline and time-varying were considered and model comparison and selection were based on such-criteria as Deviance Information Criteria (DIC). Class membership model was allowed to depend on covariates for prediction. Second, we explored disease status prediction HIV/AIDS using the latent class membership model. Third, we modeled viral load trajectories using a finite mixture model with three components of which the mean functions are designed based on published HIV dynamic systems. Although this research is motivated by HIV/AIDS studies, the basic concepts and methods developed here have much broader applications in management of other chronic diseases; they can also be applied to dynamic systems in other fields. Implementation of our methods using the publicly- vailable WinBUGS package suggest that our approach can be made quite accessible to practicing statisticians and data analysts.

Lakes have historically been overlooked as important nutrient processors within their watersheds. In general ecologists have focused on streams as zones of uptake and transformation, while viewing lakes as simple nutrient traps. However, recent research has highlighted the large influence that lakes may have on water chemistry within their watersheds. Within the field of limnology, researchers have traditionally focused on the pelagic zone for in-lake production. Further research in shallow lakes has highlighted the role benthic production within the littoral zone plays in the lake ecosystem. The greater influence of lakes is highlighted when comparing watersheds containing lakes with watersheds composed of solely stream channels. To assess the influence that lakes have on water chemistry and nutrient transport, both field and modeling analyses were performed for Bull Trout Lake, Idaho. In 2008 a large field sampling effort was conducted along with a 15N tracer experiment to characterize the limnology of Bull Trout Lake (Idaho) and nitrogen uptake and transport through the lake. Following the termination of the field season a multi-lake ecosystem model was developed with the use of a one-dimensional lake water quality model. Results from both experiments demonstrated the role of Bull Trout Lake as a nutrient processor and source within its watershed and further suggested the added influence additional lakes might have on water chemistry. The outcomes of the tracer study indicated that pelagic primary producers have the first opportunity to assimilate nitrogen delivered by the inflow stream; however, nutrients incorporated into plants within the littoral zone are held on to longer. Further the tracer experiment demonstrated the small role that large organisms have in ecosystem nutrient dynamics. The multi-lake model demonstrated the effect of BTL as a nutrient source within the watershed and indicated that although multiple lakes in sequence may have additive effects, most of this influence is expressed in the first two lakes of a series. Our research provides examples of valuable tools in limnological research. While whole-lake tracer studies have rarely been performed, they are extremely effective in understanding ecosystems. Additionally, even though lake models may be simplifications of natural systems, they can provide an efficient means of understanding lake functioning and testing hypotheses.

Le sujet de cette thèse concerne les études structurales d'une nouvelle génération d'oligomères, les foldamères, construits à partir de mimes pseudopeptidiques capables d'adopter des structures secondaires déterminées. Trois familles d'oligomères ont été étudiées. Plusieurs méthodes spectroscopiques ont été à chaque fois employées couplées à la modélisation moléculaire, afin de caractériser les propriétés structurales des foldamères. La première famille a été synthétisée par le groupe de Muriel Amblard et Monique Calmès de l'IBMM à Montpellier. Nous avons évalué les propriétés à se structurer du motif (S)-ABOC. Plusieurs oligomères de tailles variables ont été synthétisés et nous avons montré le motif (S)ABOC lorsqu'il est introduit dans une séquence peptidique est capable de générer des coudes beta. L'enchaînement de ces coudes conduits à la formation d'hélices qui en fonction des motifs pseudo-peptidiques associés présentent des caractéristiques différentes. La seconde famille étudiée comprenait des oligomères formés à partir de monomères contraints de type thiazole. Nous avons montré que ce motif, développé par Ludovic Maillard à l'IBMM à Montpellier forme des pseudocycles en C9 qui s'organisent ensuite en une hélice qui est observable dès le tétramère. La troisième famille d‘oligomères étudiée est issue du LCPM. Elle comprend des oligomères alternant des acides alpha-aminés et des acides aminés de type aza dans lesquels le carbone alpha a été remplacé par un atome d'azote. Nous avons montré que le motif aza induit un repliement en coude beta facilitant la cyclisation de la molécule. Dans ma thèse nous avons caractérisé les propriétés à s'auto-structurer de trois familles de foldamères pseudopeptidiques en combinant les résultats expérimentaux issus de la résonance magnétique nucléaire, la spectroscopie infrarouge, le dichroïsme circulaire et la diffraction des rayons X et en les intégrant à des calculs de modélisation moléculaire. Notre étude répertorie les propriétés de chaque motif à former des éléments de structure secondaire et à induire la formation de foldamères
The subject of this thesis deals with the structural studies of a new generation of oligomers, so called foldamers, constructed from pseudopeptidic mimics and able to adopt determined secondary structures. Three families of oligomers were investigated. For each oligomer several spectroscopic methods have been used combined with molecular modeling in order to characterize their structural properties. The first family was studied in collaration with the group of Muriel Amblard and Monique Calmès at IBMM in Montpellier. We have evaluated the structural properties of the motif (S)-ABOC. Several oligomers of varying sizes were synthesized and we have shown that the pattern (S)-ABOC, when introduced into a peptide sequence, is capable of generating beta turn. The sequence of these turn leads to the formation of helices, which, according to associated pseudo-peptide patterns shows different characteristics. The second project discussed the conformation of oligomers family formed from constrainted thiazole monomers. We have shown that this pattern developed by Ludovic Maillard at IBMM in Montpellier adopted pseudocycles C9 which led to helices. THis property was observed starting from the tetramer. The third family of oligomers comes from the LCPM, alternating oligomers of alpha amino acids and aza amino acids, in which the alpha carbon has been replaced by a nitrogen atom. We showed that the pattern aza induces folding of the beta turn, facilitating the cyclization of the molecule. In this thesis we have characterized the properties to self-structuring of three families of pseudopeptide foldamers by combining experimental results from nuclear magnetic resonance, infrared spectroscopy, circular dichroism and X-ray diffraction combined with molecular modeling calculations. Our study lists the properties of each pattern to form secondary structure elements and to induce the formation of foldamers

Master of Science
Department of Civil Engineering
Hayder A. Rasheed
The Kansas Department of Transportation’s (KDOT) Bridge 059-045 is a reinforced concrete box girder bridge constructed in 1965 to connect the rural Shawnee Drive across Interstate 135 near McPhearson, Kansas, in between Salina and Wichita. The bridge was observed, during an annual inspection in 1998, to have experienced some settlement, which was further found to be due to its proximity to a sinkhole. This settlement progressed to noticeable levels in 2012 necessitating a semi-annual elevation profile survey that was consistently conducted by KDOT. In April 2016, KDOT determined that the bridge required a detailed finite element analysis to determine the safety and suitability of the bridge to stay open to traffic. Accordingly, a two-level Finite Element Analysis was performed using RISA 3D and Abaqus to assess the level of distress in the bridge due to the continuous differential settlement as a result of the active sinkhole deep in the soil under the bridge. The force-moment results were taken from the RISA 3D model for further analysis of various structural components that make up the bridge, including the box girder, piers, and piles. The stress distribution results from the Abaqus model were investigated for the same components of the bridge. A strengthening design scheme using near surface mounted fiber reinforced polymer rebar was developed to extend the service life of the bridge.

The software engineering community recognized the importance of addressing security requirements with other functional requirements from the beginning of the software development life cycle. Therefore, there are some techniques that have been developed to achieve this goal. Thus, we conducted a theoretical study that focuses on reviewing and evaluating some of the techniques that are used to model and analyze security requirements. Thus, the Abuse Cases, Misuse Cases, Data Sensitivity and Threat Analyses, Strategic Modeling, and Attack Trees techniques are investigated in detail to understand and highlight the similarities and differences between them. We found that using these techniques, in general, help requirements engineer to specify more detailed security requirements. Also, all of these techniques cover the concepts of security but in different levels. In addition, the existence of different techniques provides a variety of levels for modeling and analyzing security requirements. This helps requirements engineer to decide which technique to use in order to address security issues for the system under investigation. Finally, we found that using only one of these techniques will not be suitable enough to satisfy the security requirements of the system under investigation. Consequently, we consider that it would be beneficial to combine the Abuse Cases or Misuse Cases techniques with the Attack Trees technique or to combine the Strategic Modeling and Attack Trees techniques together in order to model and analyze security requirements of the system under investigation. The concentration on using the Attack Trees technique is due to the reusability of the produced attack trees, also this technique helps in covering a wide range of attacks, thus covering security concepts as well as security requirements in a proper way.

This research investigates the environment and development issues of three stakeholders at multiple scales—global, national, regional, and local. Through the analysis of financial, social, and environmental metrics, the potential benefits and risks of each case study are estimated, and their implications are considered. In the first case study, the relationship of manufacturing and environmental performance is investigated. Over 700 facilities of a global manufacturer that produce 11 products on six continents were investigated to understand global variations and determinants of environmental performance. Water, energy, carbon dioxide emissions, and production data from these facilities were analyzed to assess environmental performance; the relationship of production composition at the individual firm and environmental performance were investigated. Location-independent environmental performance metrics were combined to provide both global and local measures of environmental performance. These models were extended to estimate future water use, energy use, and greenhouse gas emissions considering potential demand shifts. Natural resource depletion risks were investigated, and mitigation strategies related to vulnerabilities and exposure were discussed. The case study demonstrated how data from multiple facilities can be used to characterize the variability amongst facilities and to preview how changes in production may affect overall corporate environmental metrics. The developed framework adds a new approach to account for environmental performance and degradation as well as assess potential risk in locations where climate change may affect the availability of production resources (i.e., water and energy) and thus, is a tool for understanding risk and maintaining competitive advantage. The second case study was designed to address the issue of delivering affordable and sustainable energy. Energy pricing was evaluated by modeling individual energy consumption behaviors. This analysis simulated a heterogeneous set of residential households in both the urban and rural environments in order to understand demand shifts in the residential energy end-use sector due to the effects of electricity pricing. An agent-based model (ABM) was created to investigate the interactions of energy policy and individual household behaviors; the model incorporated empirical data on beliefs and perceptions of energy. The environmental beliefs, energy pricing grievances, and social networking dynamics were integrated into the ABM model structure. This model projected the aggregate residential sector electricity demand throughout the 30-year time period as well as distinguished the respective number of households who only use electricity, that use solely rely on indigenous fuels, and that incorporate both indigenous fuels and electricity. The model is one of the first characterizations of household electricity demand response and fuel transitions related to energy pricing at the individual household level, and is one of the first approaches to evaluating consumer grievance and rioting response to energy service delivery. The model framework is suggested as an innovative tool for energy policy analysis and can easily be revised to assist policy makers in other developing countries. In the final case study, a framework was developed for a broad cost-benefit and greenhouse gas evaluation of transit systems and their associated developments. A case study was developed of the Atlanta BeltLine. The net greenhouse gas emissions from the BeltLine light rail system will depend on the energy efficiency of the streetcars themselves, the greenhouse gas emissions from the electricity used to power the streetcars, the extent to which people use the BeltLine instead of driving personal vehicles, and the efficiency of their vehicles. The effects of ridership, residential densities, and housing mix on environmental performance were investigated and were used to estimate the overall system efficacy. The range of the net present value of this system was estimated considering health, congestion, per capita greenhouse gas emissions, and societal costs and benefits on a time-varying scale as well as considering the construction and operational costs. The 95% confidence interval was found with a range bounded by a potential loss of $860 million and a benefit of $2.3 billion; the mean net present value was $610 million. It is estimated that the system will generate a savings of $220 per ton of emitted CO2 with a 95% confidence interval bounded by a potential social cost of $86 cost per ton CO2 and a savings of $595 per ton CO2.

The goal of more efficiently and more reliably realizing energy conversion in the power electronics industry is pushing the limits of current wire bonding packaging technology. Emerging three-dimensional power packaging techniques have shown their potential to replace wire bonding technology down the road. However, these innovative technologies have not yet been fully understood in terms of thermal and thermo-mechanical performance. Therefore, a comparative evaluation between the thermally induced response in conventional wire bonding (a 2-Dimensional technology) and 3-Dimensional packaging technologies is essential. Thermal and thermo-mechanical analysis using the Finite Element Method (FEM) has been performed to evaluate a three-dimensional power module packaged in a Metal Post Interconnected-Parallel Plate Structure (the MPIPPS), and the result is compared with that of a wire bond module. Under the same single-sided cooling conditions, thermal modeling results show a significantly lower junction temperature of 17oC in the MPIPPS module than that in the wire bond module, due to the more uniform heat flow distribution in the MPIPPS module. The top DBC (direct bonded copper) substrate in the MPIPPS module helps direct the excessive heat generated from IGBT (Insulated Gate Bipolar Transistor) chips to diode chips (which dissipates less heat). The maximum junction temperature is reduced to 108 oC in the MPIPPS module by the implementation of double-sided cooling, which the wire bonding technique can not achieve. Subsequent thermo-mechanical analysis reveals the weak points in both modules during temperature cycling and power cycling. In the wire bond module, temperature cycle results have shown more severe stress and strain than that those of the power cycling conditions in the regions where the wires attach the device emitter pads. In the MPIPPS module, the solder joints exhibit high plastic and creep deformation. Power cycling produces more inelastic deformation at the solder joints between the posts and device, due to local over-heating, which causes more severe high-temperature creep deformation. Using a deformation-based thermal fatigue theory, the solder joint fatigue lives are predicted. Compared with the commercial wire bond module temperature cycle test, the fatigue life of MPIPPS is limited. We conclude that the MPIPPS module is better in thermal management but is thermo-mechanically less reliable than the wire bond module.
Master of Science

In this thesis, studies associated with the stability analyses of the box-shaped dump-site culvert constructed in Tinaz Surface Mine of Turkish Coal Enterprises (TKi) are presented. In addition, stability conditions of other culvert alternatives are evaluated. Existence of creeks in a surface mining area is a significant factor to be considered in selection of dump-site location. Since, the dumped overburden material on the valley acts as a barrier and behaves like a dam causing flood problem behind the dump-site. TKi engineers prevented the flood potential that might have occurred behind the dump-site by constructing a 480-meter long reinforced-concrete culvert on the downstream of Gevenez Creek Valley. However, considerable amount of deformations occurred in the first 100 meters of the culvert, as a result of overburden material being replaced on this structure. In order to determine the failure mechanism associated with the culvert, a series of numerical modeling analyses were carried out utilizing back analysis technique. The validity of the numerical model was justified by convergence measurements and observations carried out inside the culvert as overburden material being replaced on the stable part of this structure. Finally, based on the numerical model developed, the stability of other culvert alternatives that could be used in future projects were evaluated considering different embankment conditions (positive projecting and negative projecting), bedding conditions (impermissible, ordinary, first-class and concrete cradle), culvert shapes (box and circular) and dumping conditions.

Modélisation globale de l'énergie dans les réseaux de capteurs (incluant le matériel, les couches protocolaires, l'application, et l'environnement physique).
Application de méthodes de validation formelle au cas des réseaux de capteurs.
Etude de cas du projet ANR ARESA.

Soil erosion is a key issue in rangelands, but current approaches for predicting soil erosion are based on research in croplands and may not be appropriate for rangelands. An improved model is needed that accounts for the dominant erosion processes that operate in rangelands rather than croplands. In addition, effective application of such a model of rangeland erosion requires improved methods for assessing both model sensitivity and uncertainty if the model is to be applied confidently in natural resources management.I developed a new equation for calculating the combined rate of splash and sheet erosion (Dss, kg/m2) using existing rainfall-simulation data sets from the western United States that is distinct from that for croplands: Dss = Kss I 1.052q0.592, where Kss is the splash and sheet erosion coefficient, I (m/s) is rainfall intensity, and q (mm/hr) is runoff rate. This equation, which accounts for inter-relationship between I and q, was incorporated into a new model, the Rangeland Hydrology and Erosion Model (RHEM). This new model was better at predicting observed erosion rates than the commonly used, existing soil erosion model Water Erosion Prediction Project (WEPP).New approaches for assessing model uncertainty and sensitivity were developed and applied to the model. The new approach for quantifying localized sensitivity indices, when combined with techniques such as correlation analysis and scatter plots, can be used effectively to compare the sensitivity of different inputs, locate sensitive regions in the parameter space, decompose the dependency of the model response on the input parameters, and identify nonlinear and incorrect relationships in the model. The approach for assessing model predictive uncertainty, called "Dual-Monte-Carlo" (DMC), uses two Monte-Carlo sampling loops to not only calculate predictive uncertainty for one input parameter set, but also examine the predictive uncertainty as a function of model inputs across the full range of parameter space. Both approaches were applied to RHEM and yielded insights into model behavior.Collectively, this research provides an important advance in developing improved predictions of erosion rates in rangelands and simultaneously provides new approaches for model sensitivity and uncertainty analyses that can be applied to other models and disciplines.

The emplacement of tholeiitic magmas along two NE-SW trending rift zones is the dominant mechanism of crustal accretion on Iceland. Small volumes of transitional to alkaline magmas are also erupted through older crust in several off-rift settings, including the Snæfellsnes Peninsula in western Iceland where the basement is formed by 6-8 Ma flood basalts. In this study, we are investigating how these off-rift magmatic plumbing systems compare to those in the main rift zones, given the significant differences in crystal structure and degree of crustal extension, through application of quantitative textural analysis and mineral geothermobarometry. Our focus is Vatnafell, a sub-glacial eruptive unit (414 ± 11 ka) at the western end of the off-rift Ljósufjöll volcanic system in the Snæfellsnes volcanic zone. Samples are highly phyric (∼14% phenocrysts), with large phenocrysts (1-12 mm) of clinopyroxene, olivine, and plagioclase. Crystal size distributions for olivine and clinopyroxene both show kinked profiles, indicating two distinct populations. Glomerocrysts in which large clinopyroxene oikocrysts enclose smaller rounded olivine chadacrysts are common, and a small horizon strongly enriched in large (> 5 mm) olivine and clinopyroxene crystals was found near the base of the unit. These observations suggest incorporation of olivine gabbroic/wehrlitic cumulates by the host magma. Analyses show a bimodal composition for clinopyroxene (cores: mg# 83-88; rims/groundmass mg# 72-77), and calculations suggest crystallization of cores at or near the moho in the deep crust (∼25 km). More extensive analyses of mineral compositions have been used to calculate residence times and ascent rates of the crystalline cargo, and indicate rapid ascent soon after the incorporation of the wehrlitic cumulate. These data have been used to develop a more complete picture of an extension-limited off-rift magmatic plumbing system and allow a more detailed comparison with plumbing systems beneath the extension-dominated main rift zones on Iceland.

In the current research, a framework based on classical molecular dynamics (MD) is developed for computational mechanical analyses of complex nanoscale materials. The material system of focus is a combination of fcc-Al and and #945;-Fe₂O₃. The framework includes the development of an interatomic potential, a scalable parallel MD code, nanocrystalline composite structures, and methodologies for the quasistatic and dynamic strength analyses. The interatomic potential includes an embedded atom method (EAM) cluster functional, a Morse type pair function, and a second order electrostatic interaction function. The framework is applied to analyze the nanoscale mechanical behavior of the Al+Fe₂O₃ material system in two different settings. First, quasistatic strength analyses of nanocrystalline composites with average grain sizes varying from 3.9 nm to 7.2 nm are carried out. Second, shock wave propagation analyses are carried out in single crystalline Al, Fe₂O₃, and one of their interfaces. The quasistatic strength analyses reveal that the deformation mechanisms in the analyzed nanocrystalline structures are affected by a combination of factors including high fraction of grain boundary atoms and electrostatic forces. The slopes as well as the direct or inverse nature of observed Hall-Petch (H-P) relationships are strongly dependent upon the volume fraction of the Fe₂O₃ phase in the composites. The compressive strengths of single phase nanocrystalline structures are two to three times the tensile strengths owing to the differences in the movement of atoms in grain boundaries during compressive and tensile deformations. Analyses of shock wave propagation in single crystalline systems reveal that the shock wave velocity (US) and the particle velocity (UP) relationships as well as the type and the extent of shock-induced deformation in single crystals are strongly correlated with the choice of crystallographic orientation for the shock wave propagation. Analyses of shock wave propagation through an interface between Al and Fe2O3 point to a possible threshold UP value beyond which a shock-induced structural transformation that is reactive in nature in a region surrounding the interface may be taking place. Overall, the framework and the analyses establish an important computational approach for investigating the mechanical behavior of complex nanostructures at the atomic length- and time-scales.

Clostridium thermocellum is a thermophilic anaerobe that is capable of producing ethanol directly from lignocellulosic compounds, however this organism suffers from low ethanol tolerance and low ethanol yields. In vivo mathematical modeling studies based on steady state traditional metabolic flux analysis, metabolic control analysis, transient and steady states’ flux spectrum analysis (FSA) were conducted on C. thermocellum’s central metabolism. The models were developed in Matrix Laboratory software ( MATLAB® (The Language of Technical Computing), R2008b, Version 7.7.0.471)) based on known stoichiometry from C. thermocellum pathway and known physical constraints. Growth on cellobiose from Metabolic flux analysis (MFA) and Metabolic control analysis (MCA) of wild type (WT) and ethanol adapted (EA) cells showed that, at lower than optimum exogenous ethanol levels, ethanol to acetate (E/A) ratios increased by approximately 29% in WT cells and 7% in EA cells. Sensitivity analyses of the MFA and MCA models indicated that the effects of variability in experimental data on model predictions were minimal (within ±5% differences in predictions if the experimental data varied up to ±20%). Steady state FSA model predictions showed that, an optimum hydrogen flux of ~5mM/hr in the presence of pressure equal to or above 7MPa inhibits ferrodoxin hydrogenase which causes NAD re-oxidation in the system to increase ethanol yields to about 3.5 mol ethanol/mol cellobiose.

La mise en œuvre des préimprégnés unidirectionnels à fibre de carbone et résine époxyde est une étape fondamentale pour la conception de pièces structurales aéronautiques. Elle influe directement sur la qualité de la pièce et notamment sur la quantité de défauts poreux qu’elle renferme. Ainsi, deux phénomènes de création de la porosité ont été identifiés expérimentalement : l’un mécanique, l’autre thermodynamique. Une fois créés, ces défauts peuvent être extraits hors de la pièce si le marouflage et le cycle de polymérisation favorisent cette évacuation gazeuse. Les effets sur la porosité de la température et de la pression imposées pendant la réticulation de la résine sont modélisés en prenant en compte les phénomènes thermo-diffuso-mécaniques entre la résine et la bulle de gaz. Un protocole expérimental reposant sur l’analyse d’image a été développé afin de quantifier le plus précisément possible le taux volumique de porosité, ainsi que leurs tailles et leurs localisations
Long fiber reinforced epoxy matrix composite laminate manufacturing process is divided into several stages. The most critical one is the polymerization stage. If not optimized, defects in the bulk material such as voids can occur. The aim of this work is to investigate the void formation and evolution processes in order to improve the thermoset laminates quality in minimizing the void ratio. Two phenomena causing void formation have been identified. The first is the mechanical entrapment of gas bubbles between prepreg plies during the lay up. Second is a thermodynamical one. Solvents and humidity absorbed by the prepreg during its manufacturing can be evaporated by increasing the temperature. Then, it has been shown that the vaccum bag lay up permeability in combination with the vaccum pressure could favour the gas washing out. In parallel, thermo-mechanical and diffusion models are coupled to obtain an accurate void size prediction along temperature and pressure applied during the polymerisation. In fact, these two parameters induce variations of the gas bubble radius inside resin. The first experimental results seem to validate qualitatively the calculated void size behaviour. Indeed, hydrostatic pressure imposed during polymerization plays a very important role on gas bubble shrinkage. Finally, a new experimental setup using image analyses has been developed to measure as accurate as possible the volume void ratio. Under specific conditions, stereology allows to extrapolate 2D results to 3D ones. Void ratios obtained with this method are in good agreement with acid digestion results. Complementary morphometric studies on void shapes have given new information about the heterogeneous void distribution in the specimen and also on the statistical void size distribution versus polymerization conditions

Estimation of effective diffusion coefficients is essential to be able to describe the diffusive transport of solutes in porous media. It has been shown in theory that in the case of uncharged porous materials the effective diffusion coefficient of solutes is a function of the pore morphology of the material and can be described by their tortuosity (tensor). To estimate the apparent diffusion coefficients, the values of tortuosity and porosity should be known first. In contrast with calculation of porosity, which can be easily obtained, estimation of tortuosity is intricate, particularly with increasing micro-geometry complexity in porous media. Moreover, many engineering materials (e.g, clays and shales) are characterized by electrical surface charges on particles of the porous material which can strongly affect the diffusive transport properties of ions. For these materials, estimation of effective diffusion coefficients have been mostly based on phenomenological equations with no link to underlying microscale properties of these charged materials although a few recent studies have used alternative methods to obtain the diffusion parameters.
In the first part of this thesis a numerical method based on a recently proposed up-scaled Poisson-Nernst-Planck type of equation (PNP) and its microscale counterpart is employed to estimate the tortuosity and thus the effective and apparent diffusion coefficients in thin charged membranes. Beside this, a new mathematical approach for estimation of tortuosity is applied and validated. This mathematical approach is also derived while upscaling of micro-scale Poisson-Nernst-Planck system of equations using the volume averaging method. A variety of different pore 2D and 3D micro-geometries together with different electrochemical conditions are studied here. To validate the new approaches, the relation between porosity and tortuosity has been obtained using a multi-scale approach and compared with published results. These include comparison with the results from a recently developed numerical method that is based on macro and micro-scale PNP equations.
Results confirm that the tortuosity value is the same for porous media with electrically uncharged and charged particles but only when using a consistent set of PNP equations. The effects of charged particles are captured by the ratio of average concentration to effective intrinsic concentration in the macroscopic PNP equations. Using this ratio allows to consistently take into account electro-chemical interactions of ions and charges on particles and so excludes any ambiguity generally encountered in phenomenological equations.
Steady-state diffusion studies dominate this thesis; however, understanding of transient ion transport in porous media is also important. The last section of this thesis briefly introduces transient diffusion through bentonite. To do so, the micro Nernst-Planck equation with electro-neutrality condition (NPE) is solved for a porous medium which consists of compacted bentonite. This system has been studied before in another research using an experimental approach and the results are available for both transient and steady-state phases. Three different conditions are assumed for NPE governing equations and then the numerical results from these three conditions are compared to the experimental values and analytical phenomenological solution. The tortuosity is treated as a fitting parameter and the effective diffusion coefficient can be calculated based on these tortuosity values. The results show that including a sorption term in the NPE equations can render similar results as the experimental values in transient and steady state phases. Also, as a fitting parameter, the tortuosity values were found varying with background concentration. This highlights the need to monitor multiple diffusing ion fluxes and membrane potential to fully characterize electro-diffusive transport from fundamental principles (which have been investigated in first part of this thesis) rather than phenomenological equations for predictive studies.
This research has lead to two different journal articles submissions, one already accepted in Computers and Geotechnics (October 22, 2009, 5-yrs Impact Factor 0.884) and the other one still under review.

Incentive for this research stems from the fact that Business-to-Consumer electronic commerce sector is going to oligopoly and the new actors have relatively less chance to accomplish in the current market if they follow the same ways that the old companies have already paved. Considering this challenge, the aim is to understand the adoption process of customers by analyzing the contemporary perceptions of individuals against e-shopping. Initially, business-to-consumer electronic commerce adoption model is developed. Proposed model and hypotheses are tested with Partial Least Squares as a Structural Equation Modeling technique using data collected from 1115 respondents via an online survey. Then, semi-structured open-ended interviews are conducted in order to grasp the perceptions of customers. The results are interpreted following a systematic mixed methodology involving Interpretative Phenomenological Analysis to elucidate the antecedents and causal relations of constructs in an inductive and exploratory way to illuminate a socio-technical phenomenon as complementary to deductive and confirmatory quantitative perspective. Findings and implications are asserted to be utilized as a roadmap especially for start-up companies that challenge to survive and succeed in current market conditions. Trust is found to be the predominant factor in e-shopping adoption. It is proved that, after almost two decades shopping via Internet had been invented, contemporarily, definitions for the dimensions of Enjoyment, Perceived Usefulness, Store Familiarity, Perceived Ease of Use and Subjective Norm have evolved into new semantics and customers perceive each factor according to their actual cognition contexts.

Les écoulements (ou coulées) pyroclastiques (PFs) sont des mélanges concentrés de gaz et de particules à haute température qui représentent l’aléa volcanique le plus meurtrier qui soit. La protection des populations nécessite la mise au point de cartes des menaces précises, qui requièrent une connaissance fine de ces phénomènes. Cependant, les causes et les conséquences de l’érosion/incorporation associée aux PFs au cours de leur mise en place restent encore largement méconnues. Cette thèse se propose de caractériser la capacité érosive des PFs, de définir des mécanismes d’érosion, et de quantifier leurs impacts sur les budgets éruptifs et sur l’aléa associé. Pour cela, cette étude se concentre sur les PFs de volumes modestes mis en place pendant l’éruption d’août 2006 du volcan Tungurahua (Equateur) et adopte une démarche double, basée sur des investigations sédimentologiques et texturales des dépôts, couplées à la modélisation numérique. Une méthode originale, basée sur l’analyse d’images haute résolution corrigées par stéréologie, sur des études texturales détaillées des dépôts, et sur des bilans massiques de matière, permet de déterminer la granulométrie, la composition lithologique et la morphologie des produits sur l’ensemble de leur gamme de taille. Le calcul des bilans de matière montre que près de 50 wt. % des dépôts de PFs sont composés de matériaux non-juvéniles incorporés lors de la mise en place. Ces derniers proviennent principalement de la partie supérieure du volcan. La pente est ainsi le paramètre contrôlant au premier ordre l’intensité de l’érosion. Les budgets éruptifs complets indiquent un VEI de 3 (0,09 km 3 ) pour l’éruption, et soulignent l’importance de considérer séparément les matériaux juvéniles et non-juvéniles pour estimer la taille d’une éruption. L’étude détaillée des constituants met en évidence une ségrégation dynamique des clastes par densité au cours du transport, avec un taux de sédimentation de ≈10 cm.s -1 . Les données lithologiques, granulométriques et morphologiques démontrent la présence de phénomènes de fragmentation-abrasion des clastes pendant leur transport. Les clastes massifs (ex : laves anciennes) sont le principal agent de fragmentation des clastes scoriacés (ex : bombes). Des populations granulométriques fines, capables d’être transférées depuis l’écoulement dense principal vers les déferlantes et/ou le panache co-pyroclastique sont produites pendant toute la durée de la mise en place. Les modèles numériques basés sur une nouvelle loi d’érosion développée ici (et intégrée au code VolcFlow), démontrent la capacité de la rhéologie plastique à reproduire des PFs érosifs. L’érosion est associée à des variations dynamiques du rapport des contraintes normales/cisaillantes pendant la mise en place des écoulements, provoquées par des fluctuations d’épaisseur lors de phases de décélération. Le front fin des PFs, fortement frictionnel et érosif, est poussé par une tête et un corps plus épais, tous deux non érosifs. L’incorporation s’accompagne d’une augmentation de distance de parcours de l’ordre de 10-30% en fonction du taux d’incorporation, qui dépend de la quantité de matière affouillable disponible sur le volcan avant l’éruption. Ces résultats montrent que l’érosion peut avoir un rôle majeur sur les zones impactées par les PFs, et soulignent l’importance de prendre en compte cette capacité lors de la définition de l’aléa, ainsi que pour les études futures
Pyroclastic flows (PFs) are hot mixtures of gas and particles that represent the most deadly volcanic hazard. To protect the populations, it is necessary to work on precise risk maps, which require having a deep knowledge of these phenomena. However, the causes and consequences of erosion and incorporation of non-juvenile material during PFs emplacement remain poorly known. This thesis aims at characterizing the erosive capacity of pyroclastic flows, defining erosion mechanisms and quantifying their impact on eruptive budgets and associated hazards. Here, we focus on small-volume PFs and use an approach based on field and textural investigations coupled with numerical modeling of PFs emplacement. The August 2006 PF-forming eruption of Tungurahua volcano (Ecuador) is used as a case-study for this work.An original method, based on high-resolution, stereologically-corrected image analyses, detailed textural analyses of PFs deposits and mass budget, enables determining the grain size distribution and the componentry of PFs products along their entire clast size range. Volume calculation and mass budgets show that about 50 wt. % of the whole deposit consists of non-juvenile materials incorporated during PFs emplacement, and mostly coming from the upper part of the volcano. The slope is a prevailing parameter that controls PFs erosive power. Eruptive budgets support a VEI 3 event (0.09 km 3 ) for the 2006 eruption of Tungurahua and highlight the importance of separating juvenile from non-juvenile material. Detailed analyses of deposits’ componentry suggest a strong dynamic density-driven segregation of the clasts during PFs emplacement, associated with sedimentation rates of ≈10 cm.s -1 . Lateral variations of lithological, grain size, and morphological data demonstrate the occurrence of componentry-driven clast fragmentation and abrasion processes. Massive components (e.g. old lavas) are the main grinding agents of scoriaceous components (e.g. bombs). During emplacement, these processes continuously create fine grained populations, which are transferred from the main dense flow to pyroclastic surge or Co-PF cloud. Numerical models of erosive PFs based on a new erosion law integrated into VolcFlow code show the ability of plastic rheology to reproduce natural erosion patterns of PFs. The erosion is produced by dynamic variations of normal stress / shear stress ratio during emplacement, due to thickness unsteadiness during flow deceleration. The thin, highly frictional and erosive front of PFs pulses is pushed by the thicker and non-erosive head and flow body. Incorporation implies longer PFs runouts of about 10-30%, depending on the amount of incorporated material, which is related to the quantity of erodible material available on the volcano’s flanks before the eruption. These results show that erosion has a significant role on PFs runouts, and thus in hazard assessment, which should be closely taken into account in future works

Le réchauffement climatique est un problème majeur pour le monde scientifique et les sociétés. La concentration de dioxyde de carbone a augmenté de 45% depuis la période préindustrielle (Harris, 2010), conséquence des activités humaines déséquilibrant le cycle du carbone mondial. Cela se traduit par un réchauffement de la planète avec des impacts dramatiques sur la terre et encore plus pour les populations fragiles.Parmi les solutions d'atténuation, une meilleure utilisation du sol est proposée. En effet, les sols ont la plus grande capacité d'échange de carbone avec l'atmosphère et renferment un stock important de carbone. Une augmentation minime du stock de carbone du sol, les échanges de carbone entre l'atmosphère et le sol plus favorables à la séquestration du carbone dans le sol compenseraient les émissions de carbone provenant de la combustion des combustibles fossiles. Cependant, la dynamique du carbone dans le sol souffre encore de connaissances insuffisantes. Il subsiste alors une grande incertitude quant à la réponse du carbone du sol aux changements climatiques et aux changements d'affectation des terres.Plusieurs modèles mécanistiques ont été développés pour mieux comprendre la dynamique du carbone du sol. Cependant, ces modèles mécanistes ont encore une vue incomplète des processus physiques affectant la matière organique (MO) du sol. Il faudra beaucoup de temps pour obtenir un modèle complet et à jour de la dynamique des sols.Dans ma thèse, nous avons proposé un modèle statistique bayésien visant à décrire la dynamique verticale du carbone du sol. Cela se fait grâce à la modélisation du carbone organique du sol et aussi des données radiocarbone, car elles illustrent le temps de séjour de la MO et donc la dynamique du carbone du sol. Cette approche statistique visait à mieux représenter les incertitudes sur la dynamique du carbone du sol et quantifier les effets des facteurs climatiques et environnementaux sur le carbone des sols superficiels et profonds.Cette méta-analyse a été réalisée sur une base de données de 344 profils, collectés à partir de 87 articles scientifiques et archéologiques et paléoclimatologiques, sous différentes conditions climatiques et environnementales.Un modèle non linéaire hiérarchique avec effets aléatoires a été proposé pour modéliser la dynamique verticale du radiocarbone en fonction de la profondeur. Les techniques de sélection bayésiennes, récemment publiées, ont été appliquées aux couches latentes de notre modèle, elles-mêmes liées par une relation linéaire aux facteurs climatiques et environnementaux. Le Bayesian Group Lasso, le Bayesian Sparse Group Selection(BSGS) et le Bayesian Effect Fusion(BEF) ont été testés pour identifier les principaux prédicteurs explicatifs catégoriels et le Stochastic Search Variable Selection pour identifier les prédicteurs explicatifs numériques influents. Une comparaison de ces techniques bayésiennes a été effectuée sur la base des critères de sélection du modèle bayésien pour spécifier quel modèle a le meilleur pouvoir prédictif En plus de la sélection de prédicteurs catégoriels, le BSGS permet de formuler une probabilité d'inclusion a posteriori pour chaque niveau dans les prédicteurs catégoriels comme type de sol et type d'écosystème. En outre, le BEF a permis de fusionner les types de sol et les types d’écosystèmes qui, selon le BEF, sont supposés avoir les mêmes effets sur nos réponses d’intérêts que la réponse du radiocarbone du sol arable.L'application de ces techniques a permis de prédire, en moyenne et au niveau mondial, la dynamique verticale du radiocarbone dans le cas d'une augmentation de température et de changement d’usage des sols. Par exemple, nous avons étudié l'impact de la déforestation des forêts tropicales et leur remplacement par des terres cultivées sur la dynamique du carbone du sol. La même analyse statistique a également été effectuée pour mieux comprendre la dynamique verticale de la teneur en carbone du sol
Global warming is a major issue for both the scientific world and societies. The concentration of carbon dioxide has increased by 45% since the pre-industrial era (Harris, 2010) as a consequence of human activities, unbalancing the global carbon cycle. This results in global warming with dramatic impacts on the Earth, particularly for fragile populations.Amongst mitigation solutions, a better use of soil is proposed. Soils have the largest capacity of carbon exchanges with the atmosphere and contain a large stock of carbon. A tiny increase in this soil carbon stock and in carbon exchanges between atmosphere and soil would be more favorable to soil carbon sequestration and would compensate for carbon emissios from burning fossil fuel. However, soil carbon dynamics still suffers from insufficient knowledge. There remains therefore a huge uncertainty about the soil carbon response to climate and land-use changes.While several mechanistic models have been developed to better understand the dynamics of soil carbon, they provide an incomplete view of the physical processes affecting soil organic matter (OM). It will be long before a complete and updated soil dynamics model becomes available.In my thesis, I propose a Bayesian statistical model aiming at describing the vertical dynamics of soil carbon. This is done thanks to the modeling of both soil organic carbon and of radiocarbon data as they illustrate the residence time of organic matter and thus the soil carbon dynamics. The purpose of this statistical approach was to better represent the uncertainties on soil carbon dynamics and to quantify the effects of climatic and environmental factors on both surface and deep soil carbon.This meta-analysis was performed on a database of 344 profiles, collected from 87 soil science papers and the literature in archeology and paleoclimatology, under different climate conditions (temperature, precipitation, etc.) and environments (soil type and type of ecosystem).A hierarchical non-linear model with random effects was proposed to model the vertical dynamics of radiocarbon as a function of depth. Bayesian selection techniques, recently published, were applied to the latent layers of the model, which in turn are linked by a linear relationship to the climatic and environmental factors. The Bayesian Group Lasso with Spike and Slab Prior (BGL-SS), the Bayesian Sparse Group Selection (BSGS) and the Bayesian Effect Fusion model-based clustering (BEF) were tested to identify the significant categorical explanatory predictors (soil type, ecosystem type) and the Stochastic Search Variable Selection method to identify the influential numerical explanatory predictors. A comparison of these Bayesian techniques was made based on the Bayesian model selection criteria (the DIC (Deviance Information Criterion), the Posterior Predictive Check, etc.) to specify which model has the best predictive and adjustment power of the database profiles. In addition to selecting categorical predictors, the BSGS allows the formulation of an a posteriori inclusion probability for each level within the categorical predictors such as soil type and ecosystem type (9 soil types and 6 ecosystem types were considered in our study). Furthermore, the BEF made it possible to merge the types of soil as well as the types of ecosystem, which according to the BEF, are considered to have the same effects on the responses of interest here, such as the response of the topsoil radiocarbon.The application of these techniques allowed us to predict, on average and on a global level, the vertical dynamics of the radiocarbon in the case of a temperature increase of 1, 1.5 and 2 °C, and in the case of a change in vegetation cover. For example, we studied the impact of deforesting tropical forests and replacing them by cultivated land on soil carbon dynamics. The same statistical analysis was also done to better understand the vertical dynamics of soil carbon content