The study applies the phase-field method to simulate the behavior between bubble and liquid-solid front in the solidification. During the process, the two-phase flow module is used to match up with temperature and phase-field function to determine the percentage of- solid, liquid, and gas- in the domain. The governing equations for mass, momentum and energy contain coefficients which are related to percentage of phases.The result show that the surface tension and the temperature difference will influence the shape of bubble and the velocity of solidification.

A new two phase separator for use in space applications has been invented. It is a vortex separator designed to accommodate gas driven two phase flows of gas and liquid. The work presented here is a first of a kind study of this newly invented separator and is meant to determine the minimum inlet gas flow rate necessary for a stable vortex inside the separator for different separator geometries. A dimensional scaling analysis was done to predict this minimum inlet gas flow rate. Experiments were performed on the ground and in conjunction with NASA using their microgravity simulating plane to determine this minimum inlet gas flow rate. The results of the experiments and scaling analysis are compared. The new design consists of two chambers, a vortex generator and a separation chamber, meant to divide the functions of vortex creation and phase separation. The two phase flow is injected tangentially into the vortex generator causing the inlet linear momentum to be transformed into azimuthal momentum. The two phase mixture in the vortex generator then moves into the separation chamber where the two phases separate due to the density difference between the phases. The dimensional scaling analysis used the Weber number to predict the minimum rotational velocity of the spinning flow in the separation chamber during a stable vortex. This rotational velocity was related to the inlet gas flow rate by the inlet momentum rate. The scaling used the dimensions of each separator tested to predict the minimum inlet gas flow rate needed for a stable vortex. In all, twelve separators were tested, eleven on the ground and one on the plane. The ground testing was a parametric study varying the sizing of the separator components. The flight experiments kept the separator geometry constant and varied the gravitational field in which the separator operated. In general, the minimum inlet gas flow rate increased with the ratio of separation chamber diameter to vortex generator diameter. This same trend was consistent with the dimensional scaling analysis. Also, the inlet flow rate increases with gravitational acceleration.

The objective of this thesis is to update the outage management system (OMS) in Taipower by verifying the phasing of distribution transformers and the connectivity of customers served by each distribution transformer. The GPS based phase measurement unit (PMU) is used to measure the voltage phasing of the transformer. The power line carrier (PLC) based identifier has been developed to support the identification of distribution transformer and all the customers served. In the thesis, four practical distribution feeders in Fengshan District of Taipower are selected for the update of distribution transformer phasing of OMS system for the update of distribution transformer phasing of OMS system. After correcting the phasing of distribution transformer in the OMS database, the attributes of distribution components are retrieved for the OMS system. The network configuration of distribution feeders is identified by exacting the topology process and node reduction to prepare the input data for load flow analysis. With the monthly energy consumption of customer from the customer information system (CIS) and the typical load patterns of various customer classes, the hourly loading of each transformer can be derived. By retrieving the actual power data of test feeders from the distribution dispatch control center (DDCC), the three phase load flow analysis is executed to solve the three phase currents of trunk line sections, laterals and distribution transformers. The three phase currents solved can therefore be applied to derive the strategy of three phase balancing of distribution feeders.

Acrylamide is an industrially produced chemical with known neurotoxic, reproductive toxin and carcinogenic effects. The carcinogenicity associated with acrylamide is mostly attributed to its metabolism by liver CYP2E1. However, studies investigating the effects of acrylamide on CYP2E1 enzyme are limited. In this study, it was aimed to investigate in vivo interaction of carcinogenic acrylamide on microsomal cytochrome P450 enzyme activities, and protein levels, and on cytosolic NQO1 and GST enzyme activities of rabbit liver, kidney and lung of acrylamide-treated rabbits. The in vivo protective effect of resveratrol, a phenolic compound, was also investigated on acrylamide toxicity. New Zealand male rabbits were treated with acrylamide and resveratrol, separately in different doses and conditions. Their combined effects were also investigated. CYP2E1-dependent p-Nitrophenol hydroxylase, NDMA N-demethylase and aniline 4-hydroxylase activities were found to be significantly increased in acrylamide-treated rabbit liver (1.80-3.0 fold) and kidney (1.6-fold). Rabbit liver and kidney CYP2E1 protein levels (determined by western blot analyisis) also increased approximately 2-fold due to acrylamide treatment. In rabbit liver, resveratrol was found significantly effective in decreasing both acrylamide-induced CYP2E1-dependent enzyme activities (approximately 1.5-1.80 fold) and CYP2E1 protein levels (approximately 1.5-1.70 fold). Additionally, resveratrol significantly decreased acrylamide-induced CYP2E1 protein level (2-2.5 fold) in rabbit kidney. However, no significant change was observed in rabbit lung CYP2E1-dependent enzyme activities and CYP2E1 protein levels due to acrylamide, resveratrol or their combined treatments. Furthermore, it was found that acrylamide treatment significantly increased CYP3A6-dependent erythromycin N-demethylase enzyme activity (1.85-fold) and CYP3A6 protein levels in rabbit liver (1.69-fold). No change was observed in CYP2B4-dependent benzphetamine N-demethylase enzyme activities of rabbit liver, kidney and lung by in vivo acrylamide, resveratrol or their combined treatments. Moreover, total GST and GST-Mu activities of rabbit kidney (1.5-fold, respectively) and total GST activity of rabbit lung (1.6-fold) were increased significantly only in resveratrol treated group. NQO1 enzyme activity of rabbit kidney was significantly increased by acrylamide treatment (1.6-fold). The results of the present study have demonstrated for the first time that acrylamide induces rabbit liver and kidney CYP2E1-dependent enzyme activities and CYP2E1 protein levels. The induction of CYP2E1 enzyme activity and protein level by acrylamide treatment can stimulate formation of other toxic compounds and procarcinogens metabolized by CYP2E1 which in turn further potentiates the risk of hepatotoxicity, mutagenicity and carcinogenicity. In the present study, it was also demonstrated for the first time that acrylamide treatment also increases CYP3A6 enzyme activity in rabbit liver which may lead to alterations in drug metabolism. The results of this study have also suggested that resveratrol may have protective effects on acrylamide induced toxicity / however, further in vivo studies are required to clarify the effect of resveratrol on both acrylamide-induced toxicity and anti-oxidant enzymes.

Enhancing the quality of services in the distribution system is an important topic for power system research. It is imperative to employ precise network modeling and effective simulation tools, and a good system model is the key. This dissertation starts with modifying the building algorithms of Y-admittance and Z-impedance matrices. The Y-matrix will be built according to phase sequences. With the facts that the line self-impedance is significantly greater than the mutual-coupling terms and the existence of a high r/x ratio in distribution, two decoupled load flow methods (Phase-Decoupled¡BPD and Sub-Phase-Decoupled¡BSPD) with Current Injection Model(CIM) were developed. A new Z-matrix building algorithm was also developed in this dissertation. It decomposed the traditional Z into two sub-matrices, the upper and lower triangular matrices respectively. The matrices represent the relationships between the branch current and the bus injection current, and between the bus voltage and the branch current. Enhancing the quality of services will be effectively achieved by a proper capacitor placement technique. This dissertation develops a linear relationships of voltage changes versus the capacitor compensation, the branch current changes versus the capacitor compensation, and loss reductions versus the capacitor compensation. For loss reduction, a linear optimization function was defined to solve the capacitor placement problem. Tests have shown that the proposed methods were suitable for applications to an unbalance distribution system.

We present a general approach for determining the equilibrium shape of isolated, coherent, misfitting particles by minimizing the sum of elastic and interfacial energies using a synthesis of finite element and optimization techniques. The generality derives from the fact that there is no restriction on the initial or final shape, or on the elastic moduli of the particle and matrix, or on the nature of misfit. The particle shape is parameterized using a set of design variables which are the magnitudes of vectors from a reference point inside the particle to points on the particle/matrix interface. We use a sequential quadratic programming approach to carry out the optimization. Although this approach can be used to find equilibrium shapes of particles in three dimensional systems, we have presented the details of our formulation for two dimensional systems under plane strain conditions. Using our formulation, we have studied the equilibrium shapes in two dimensional systems with cubic anisotropy; the precipitate and matrix phases may have different elastic moduli, and the misfit may be dilatational or non-dilatational. The equilibrium shapes and their size dependence are analysed within the framework of symmetry-breaking shape transitions. These transitions are further characterized in terms their dependence on the cubic elastic anisotropy parameter, defined by A = 2C44/(C11 – C12), and on the modulus mismatch, defined by δ=μp/μm, where /μp and μm are the effective shear moduli of the precipitate and matrix phases, respectively. Depending on the type of misfit, the systems may be classified into the following four cases: Case A: For dilatational misfit, the equilibrium shapes in isotropic systems are circular (with an isotropic or I symmetry) at small sizes and undergo a transition at a critical size to become ellipse-like (with an orthorhombic or O symmetry). This I --O transition is continuous and is obtained only when the precipitate phase is softer than the matrix. These results are in good agreement with the analytical results of Johnson and Cahn. In cubic systems with dilatational misfit, the particles exhibit a transition from square-like shapes (with a tetragonal or T symmetry) at small sizes to rectangle-like shapes (with an O symmetry) at large sizes. This T -- O transition is continuous. It occurs even in systems with stiffer precipitates; however, it is forbidden for systems with δ >δC, where δ C represents a critical modulus mismatch. The critical size decreases with increasing cubic anisotropy (i.e., with increasing values of (A-1)/(A+1). The sides of the square-like and rectangle-like shapes are along the elastically soft directions. Case B: In these systems, the principal misfits e*xx and e*yy differ in magnitude but have the same sign. The precipitates at small sizes become elongated along the direction of lower misfit; this shape has an O symmetry. In systems with A > 1, they continue to become more elongated along the same direction, exhibiting no symmetry-breaking transition. However, in systems with A < 1, particles at large sizes are elongated along an intermediate direction between the direction of lower misfit and one of the elastically soft <11> directions; this shape has only a monoclinic or M symmetry. This O - M transition, in which the mirror symmetries normal to the x and y axes are lost, may be discontinuous or continuous. The critical size increases with δ (in the range 0.8 < δ <1.25), indicating that this transition would also be forbidden for systems with δ > δC. In systems with A < 1, the critical size decreases with increasing values of A-1/ A+1 Case C: In these systems, the principal misfits differ in both magnitude and sign, and the misfit strain tensor allows an invariant line along which the normal strain is zero. The precipitates at small sizes are elongated along the direction of lower absolute misfit, and possess an 0 symmetry. At large sizes, the mirror symmetries normal to the x and y axes are broken to yield shapes which are elongated along a direction between that of lower misfit and the invariant line. This 0 -> M transition is continuous and occurs in all the systems irrespective of the value of A The critical size increases with A and decreases with δ. Case D; The misfit in this case is a special form of that in Case C; the principal misfits have the same magnitude but opposite signs. The precipitates at small sizes have a square-like shape with its sides normal to the < 11 > axes, irrespective of the type of cubic anisotropy. At large sizes, they become rectangle-like with the long axis oriented along one of the <11> directions. Similar to Case C, this T - 0 transition is continuous and occurs in all the systems irrespective of the values of A. The critical size increases with A and decreases with δ. Thus, we have identified all the symmetry-breaking transitions in equilibrium shapes of coherent precipitates in two dimensional systems. We have identified their origin and nature, and characterized them in terms of their dependence on the anisotropy parameter and modulus mismatch.

<p>This thesis deals with modeling of two types of fuel cells:the polymer electrolyte fuel cell (PEFC) and the directmethanol fuel cell (DMFC), for which we address four majorissues: a) mass transport limitations; b) water management(PEFC); c) gas management (DMFC); d) thermal management.</p><p>Four models have been derived and studied for the PEFC,focusing on the cathode. The first exploits the slenderness ofthe cathode for a two-dimensional geometry, leading to areduced model, where several nondimensional parameters capturethe behavior of the cathode. The model was extended to threedimensions, where four di.erent flow distributors were studiedfor the cathode. A quantitative comparison shows that theinterdigitated channels can sustain the highest currentdensities. These two models, comprising isothermal gasphaseflow, limit the studies to (a). Returning to a two-dimensionalgeometry of the PEFC, the liquid phase was introduced via aseparate flow model approach for the cathode. In addition toconservation of mass, momentum and species, the model wasextended to consider simultaneous charge and heat transfer forthe whole cell. Di.erent thermal, flow fields, and hydrodynamicconditions were studied, addressing (a), (b) and (d). A scaleanalysis allowed for predictions of the cell performance priorto any computations. Good agreement between experiments with asegmented cell and the model was obtained.</p><p>A liquid-phase model, comprising conservation of mass,momentum and species, was derived and analyzed for the anode ofthe DMFC. The impact of hydrodynamic, electrochemical andgeometrical features on the fuel cell performance were studied,mainly focusing on (a). The slenderness of the anode allows theuse of a narrow-gap approximation, leading to a reduced model,with benefits such as reduced computational cost andunderstanding of the physical trends prior to any numericalcomputations. Adding the gas-phase via a multiphase mixtureapproach, the gas management (c) could also be studied.Experiments with a cell, equipped with a transparent end plate,allowed for visualization of the flow in the anode, as well asvalidation of the two-phase model. Good agreement betweenexperiments and the model was achieved.</p><p><b>Keywords:</b>Fuel cell; DMFC; PEFC; one-phase; two-phase;model; visual cell; segmented cell; scale analysis; asymptoticanalysis.</p>

Les travaux relatifs aux composés du tellure sont relativement récents et peu nombreux. L'étude systématique des propriétés chimiques et structurales de composés oxygénés du tellure +IV a été entreprise au laboratoire de manière à préciser les caractéristiques de la liaison tellure-oxygène et notamment d'apprécier l'influence du doublet inerte 5s2 sur l'architecture du réseau cristallin...

Texte remanié de: Thèse de doctorat--Médecine--Toulouse 3, 2003. / Bibliogr. p. 259-267.

The diffusion absorption refrigeration (DAR) cycle is a promising technology for fully thermally driven cooling. It is well suited to applications in medicine refrigeration and air-conditioning in off-grid settings. However, design and engineering knowhow for the technology is limited; therefore, system development has historically been an iterative and expensive process. Additionally, conventional system designs require high-grade energy input for operation, and are unsuitable for low-temperature solar- or waste-heat activated applications. In the present effort, component- and system-level DAR engineering analyses are performed. Detailed bubble-pump generator (BPG) component models are developed, and are validated experimentally and with direct simulations. Investigations into the BPG focus on the Taylor flow pattern in the intermediate Bond number regime, which has not yet been thoroughly characterized in the literature, and has numerous industry applications, including nuclear fuel processing and well dewatering. A coupling-fluid heated BPG design is also investigated experimentally for low-source-temperature operation. Phase-change simulation methodologies are developed to rigorously study the continuously developing flow pattern in this BPG configuration. Detailed component-level models are also formulated for all of the other DAR heat and mass exchangers, and are integrated to yield a complete system-level model. Results from these modeling studies are applied to develop a novel fully passive low-source-temperature (110 - 130°C) DAR system that delivers refrigeration grade cooling. This design achieves operation at target conditions through the use of alternate working fluids (NH3-NaSCN-He), the coupling-fluid heated BPG, and a novel absorber configuration. The complete DAR system is demonstrated experimentally, and evaluated over a range of operating conditions. Experimental results are applied to assess and refine component- and system- level models.