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. 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. 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. Keywords:Fuel cell; DMFC; PEFC; one-phase; two-phase;model; visual cell; segmented cell; scale analysis; asymptoticanalysis.

<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>

In this study, domestic wastewater was used to determine the anaerobic treatment performances of a dilute wastewater in one-phase upflow anaerobic sludge blanket (UASB) system and two-phase upflow anaerobic filter (UAF) and UASB system. The acidification performances of domestic wastewater were compared in UAF and UASB reactors. The degree of acidification is higher in UAF reactor (31%) compared to UASB reactor (18%) at 2 h hydraulic retention time (HRT) in the anaerobic treatment of domestic wastewaters. The effluent total volatile fatty acid (tVFA) concentration was higher in UAF reactor than that the UASB reactor at 2 h HRT. The total chemical oxygen demand (tCOD) removal is 40% in winter and 53% in summer in UAF reactor at 2 h HRT. The tCOD removals in two-phase UAF and UASB system and one-phase UASB system were 83% and 63%, respectively, in 4 h HRT. The conversion rate of COD removed to methane were between 0.005 and 0.067 Nm3 methane/kg COD removed and between 0.158 and 0.233 Nm3 methane/kg COD removed in the UAF and the UASB reactor of the two-phase system, respectively. The conversion rate of COD removed to methane varied between 0.029 and 0.199 Nm3 methane/kg COD removed in one-phase UASB reactor. The results of this study showed that the two-phase reactor system consisting from UAF and UASB reactors provide a good removal of soluble organics variations in acidification reactor and better methane productions in UASB reactor at temperatures 20&deg / C and 35&deg / C through the treatment of domestic wastewater at a HRT of 4 hours.

Business transactions (a.k.a., business conversations) are series of message exchanges that occur between software applications coordinating to achieve a business objective. Web service has been proven to be a promising technology in supporting business transactions. Business transaction can either be long-running or short-lived. A transaction whether in a database or web service paradigm consists of an “all-or-nothing” property. A transaction could either succeed or fail. Web Service Atomic Transactions (WS-AT) is a specification that currently supports Two-Phase Commit (2PC) protocol in a short-lived transaction. WS-AT is developed by OASIS–a standards development organization. However, not all business process scenarios require a 2PC, in that case, just a One-Phase Commit (1PC) would be sufficient. But unfortunately, WS-AT currently does not support 1PC optimization. The ideal scenario where 1PC can be used instead of 2PC is when there is only a single participant. Short-lived transactions involving only one participant can commit without requiring initial “prepare” phase. Thus, there is no overhead to check whether the participant is prepared to either commit or rollback. This research focuses on designing a mechanism that can add 1PC support in WS-AT. The technical implementation of this mechanism is developed by using JBoss Transaction API. As a part of this thesis, 1PC mechanism for a single participant scenario was implemented. This mechanism optimizes the web service transaction process in terms of overhead and performance in terms of execution time. The technical implementation solution for 1PC mechanism was evaluated using three different business process scenarios in a controlled experiment as a presence or absence test. Evaluation results show that 1PC mechanism has a lower mean for execution time and performed significantly better than 2PC mechanism. Based on the contributions made by this thesis, we recommend OASIS to consider including 1PC mechanism as a part of the WS-AT specification.

The master‘s thesis deals with utilization of infrared camera for temperature measurement of electrical machines. The first part describes non-contact temperature measuring, the second part describes principle of sensors that evaluate quantity of incident infrared radiation. In the next part there is termovision camera SAT-HY 6800 presented and the instructional manual for SAT Report computer programme created. This computer programme is used for analyzing of termovision pictures from the SAT-HY 6800 termovison camera. The chapter 7 describes temperature measuring of one-phase asynchronous motor type J22TO484. The chapter 8 describes temperature measuring of semiconductor components of EC motor G6 series. Both of these motors are produced by ATAS elektromotory Náchod a.s. The last part of the thesis describes creation of animation of one-phase asynchronous motor type J22TO455. The animation was created in 3ds Max computer programme.

This project deals with increasing efficiency of one phase induction motor with permanent split capacitor. We can whole thesis divide into two parts, the first one is basic and the second is interested in analysis and measurement. First part handles with construction of single phase induction motor, explanation of function principle, start and run of motor. Calculating of efficiency including type of losses, which reduce efficiency. Second part concerns analysis losses including moment load characteristic, motor measurement while rotor is locked, with no load operation, measuring mechanical and additional losses. Further there will be measured useful values for creation model for simulation (reactance of windings etc.). Than will be the model created in ANSYS Maxwell with module RMxprt. After analytic calculation in RMxprt and using Finite Element Method (FEM) load characteristics will be compared together. This comparison gives us information about accuracy of model for simulation. Simulation and measurement will be carried out on another engine with high quality ferromagnetic material used for magnetic circuit of motor. Further will be done simulation of motor with modifications shown in previous chapter for high efficiency.