The main objective of this research is to analyze the performance of micro direct methanol fuel cell (£gDMFC) and observe the bubble behavior of carbon dioxide in the anode flow channel. The flow plate adopted in this study was manufactured through deep UV lithography manufacturing and micro-electroforming manufacturing process. The geometrical configuration of the flow field is in the serpentine form. Transparent acrylic (PMMA: Polymethylmethacrylate) was used to make the terminal plate placed on both sides of the cell in order to facilitate the observation of the bubble behavior of carbon dioxide in the anode flow channel. In this experiment, Micro Particle Image Velocimetry (£gPIV) is used in order to investigate the generation / removal process of carbon dioxide from the anode of micro direct methanol fuel cell (£gDMFC) through a visualized observation method. The behavior of carbon dioxide bubbles in liquidized methanol solution and micro flowfield is also explored. Major parameters of the experiment operation that consist of flow rate of anode and cathode, density of methanol and operational temperature are used to explore their influences on the fuel cell¡¦s polarization curve and power density. The results are presented by V-I curve and P-I curve. The relation between carbon dioxide bubble movement and behavior according to the anode pressure drop are also discussed.

The Electron Energy Corporation (EEC) along with National Aeronautics and Space Administration (NASA) in collaboration with Vibration Control and Electro mechanics Lab (VCEL), Texas A & M University, College Station, TX are researching on high temperature permanent magnet based magnetic bearings. The magnetic bearings are made of high temperature resistant permanent magnets (up to 1000 degrees F). A test rig has been developed to test these magnetic bearings. The test rig mainly consists of two radial bearings, one axial thrust bearing and two catcher bearings. The test rig that the catcher bearing is inserted in is the first ultra-high temperature rig with permanent magnet biased magnetic bearings and motor. The magnetic bearings are permanent magnet based which is a novel concept. The Graphalloy bearings represent a new approach for ultra-high temperature backup bearing applications. One of the main objectives of this research is to insure the mechanical and electrical integrity for all components of the test rig. Some assemblies and accessories required for the whole assembly need to be designed. The assembly methods need to be designed. The preliminary tests for coefficient of friction, Young's modulus and thermal expansion characteristics for catcher bearing material need to be done. A dynamic model needs to be designed for studying and simulating the rotor drop of the shaft onto the catcher bearing using a finite element approach in MATLAB. The assembly of the test rig was completed successfully by developing assembly fixtures and assembly methods. The components of the test rig were tested before assembly. Other necessary systems like Sensor holder system, Graphalloy press fit system were designed, fabricated and tested. The catcher bearing material (Graphalloy) was tested for coefficient of friction and Young's modulus at room and high temperatures. The rotor drop was simulated by deriving a dynamic model, to study the effect of system parameters like clearance, coefficient of friction, negative stiffness, initial spin speed on system behavior. Increasing the friction increases the backward whirl and decreases the rotor stoppage time. Increasing the clearance reduces the stoppage time and increases the peak bearing force. Increasing the initial spin speed increases the rotor stoppage time. The maximum stress encountered for as built conditions is more than allowable limits.

Pressure drops over a packed bed of pebble bed reactor type are investigated. Measurement of porosity and pressure drop over the bed were carried out in a cylindrical packed bed facility. Air and water were used for working fluids. There are several parameters of the pressure drop in packed beds. One of the most important factors is wall effect. The inhomogeneous porosity distribution in the bed and the additional wetted surface introduced by the wall cause the variation of pressure drop. The importance of the wall effects and porosity can be explained by using different bed-to-particle diameter ratios. Four different bed-to-particle ratios were used in these experiments (D/dp = 19, 9.5, 6.33 and 3.65). A comparison is made between the predictions by a number of empirical correlations including the Ergun equation (1952) and KTA (by the Nuclear Safety Commission of Germany) (1981) in the literature. Analysis of the data indicated the importance of the bed-to-particle size ratios on the pressure drop. The comparison between the present and the existing correlations showed that the pressure drop of large bed-to-particle diameter ratios (D/dp = 19, 9.5and 6.33) matched very well with the original KTA correlation. However the published correlations cannot be expected to predict accurate pressure drop for certain conditions, especially for pebble bed with D/dp (bed-to-particle diameter ratio) </= 5. An improved correlation was obtained for a small bed-to-particle diameter ratio by fitting the coefficients of that equation to experimental database.

Solder joints are the most fragile parts in electronic package. The properties of joints made of lead-free material are harder and crisper than those of lead-contained material. They tend to break due to dynamic loading by absorbing the impact energy and result in malfunction. Thus, how to improve the reliability of contact joints made of lead-free material in dynamic loading has become an important topic for research. This work is based on JEDEC Standard JESD22 - B111 ¡§Board Level Drop Test Method of Components for Handheld Electronic Products,¡¨ and JESD22 ¡V B110 ¡§Subassembly Mechanical Shock¡¨. The setup of drop test apparatuses was used to conduct dropping tests with the impact of acceleration 1500 G, in order to acquire the reliability of SnAgCu, SnCu, and SnAg alloy, which would be compared with 63Sn37Pb. The specimens would be red-dyed for an analysis under SEM to examine the distribution of the breakage. The results were analyzed by Weibull distribution to predict Mean Time to Failure (MTTF), it is revealed that MTTF of solder joints made of Sn0.7Cu, Sn2.6Ag0.5Cu, and Sn3.0Ag0.5Cu (MTTF=355.32, 295.82, 289.54 cycles respectively) are longer than that made of 63Sn37Pb (MTTF=152.52 cycles). Notably, MTTF of alloy Sn0.7Cu is 2.3 times of solder joints of SnPb. Alloy Sn3.0Ag0.5Cu has the shortest MTTF among the three, which is also 1.89 times of alloy SnPb. That is to say, under impact of 1500G, solder joints made of Sn0.7Cu, Sn2.6Ag0.5Cu, and Sn3.0Ag0.5Cu possess greater resistance to shock than alloy 63Sn37Pb, which is in common by used at present. In addition, the breakage of solder joints mainly generated on Intermetallic Compound (IMC) and around the four corners, distributed from the periphery to the central area. Especially, those on the corners receive greater stresses due to edge effect.

Due to the property of the photonic crystal, like bandgap, many researches on them are discussed. Photons with wavelength within the bandgap cannot propagate through the crystal. Then placing some defects in the crystal, because the periodic arrangement is destroyed, it is possible to build a waveguide to guide light along certain path. One kind is coupled cavity waveguide. The photons can propagate in a coupled-cavity waveguide by coupling without radiation losses. So it is widely used to implement a variety of optical devices. In this thesis, we use coupled cavity waveguide to construct devices. And the characteristics of Mach-Zehnder interferometer and power splitter are discussed. Then we propose two logic gate structures with an input port and two control ports. The state of control port determines the electric field at the output port. Besides, the four-port channel drop filter is proposed. It will make the three wavelengths ¢w1310, 1490 and 1550 nm¢w propagate in different waveguides. So it could be used as a wavelength demultiplexer for FTTH. Finally, the property of the PC-based rat-race circuit is investigated. By adjusting the phase of the control signal, we could decide the input signal to exit from output 1 or output 2. In this way, we could use it to function as a switch.

The purpose of this study was to examine the effects of landing on a combined inverted and plantarflexed surface on the ankle kinematics and electromyographic (EMG) activities of the medial gastrocnemius (MG), peroneal longus (PL) and anterior tibialis muscles (TA). Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to each of these surfaces: a flat surface, a 25° inversion surface (inverted), and a combined surface (combined) of 25° inversion and 25° plantarflexion. The three dimensional kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using one-way repeated measures analysis of variance (ANOVA, p < 0.05) and a 3 × 3 (surface × muscle) ANOVA, respectively. The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG and ankle plantarflexion angle were significantly higher for the combined surface compared to the inverted surface. These findings suggest that compared to inversion, a combination of plantarflexion and inversion provides a more realistic surface for simulating lateral ankle sprains.

Zugl.: München, Techn. Univ., Diss. / !01044663X! ; Nr. 384

Målet med examensarbetet har varit att ta fram teoretiskt underlag och en beräkningsmodell. Detta ska beskriva hur kabeltyp, kabellängd, kabelarea samt effektfaktor påverkar spänningsfallet över ett 400 Hz ledningssystem. Mätningar har utförts på två olika kablar som används i det aktuella systemet. En av kablarna var symm­et­riskt uppbyggd med 7 ledare, där respektive fas bestod av två ledare förskjutna 180° från varandra runt nolledaren. För att åstadkomma 115/200V 400 Hz, användes en 90 kVA frekvensomformare. Belastningen som användes var en resistiv, induktiv samt en kapacitiv belastning. Med den resistiva belastningen justerades effekten för att ställa in den effektfaktor som önskades under mätningarna. Detta var inte möjligt med den induktiva eller den kapacitiva belastningen, då de inte kunde regleras steglöst.   Beräkningsmodellen jämfördes sedan med mätningarna av spänningsfallet. Den visade sig ge en bra uppskattning av de uppmätta värdena för att kunna användas i Saabs fortsatta arbete. Vidare ges förslag på hur de distorsioner som uppstår, i samband med komplexa laster, kan minskas. Detta för att klara de standardiserade mått på elkvaliteten som ställs i de gällande standarderna MIL-STD-704E och ISO 6858-1982 (E). Beräkningsmodellen och dess beräkningar presenteras dock inte i denna rapport, då det av Saab AB är sekretessbelagda. / The goal with this bachelor thesis has been to present theoretical material and a calculation model. This is to be used to explain how cable type, cable length, cable area affects the voltage drop in a 400 Hz power system. Measurements have been made on two different cables that are being used in the current system. One of the cables was built symmetrically built with 7-conduktors, where each phase consisted of two conductors shifted 180° from each other around the neutral conductor. To establish the system voltage 115/200 V 400 Hz, a 90 kVA frequency converter was used. The load that was used under the measurements was a resistive, inductive and a capacitive load-equipment. With the resistive load active power is adjusted to obtain the proper power factor for different measurements. This was not an option with the inductive or the capacitive load-equipment since they could not be regulated with a rheostat as the resistive load. The calculation model was compared with the measured results of the voltage drop. It was proven that it approximated the voltage drop good enough to be used in Saabs future work. Furthermore, suggestions are made of how to minimize the distortions that are developed by complex loads, to clear the demands on power quality presented by the standards MIL-STD-704E and ISO 6858-1982 (E).

Nederbördsmätning är viktigt inom många områden och en relativt ny teknik är enoptisk distrometer som med hjälp av laserteknik mäter nederbördspartiklarnasdroppstorlek och fallhastighet. Syftet med detta arbete var att undersöka hur välThies distrometer stämmer överens med nederbördsmätning från ett vippkärl ochmanuella mätningar från institutionen för geovetenskaper vid Uppsala universitet.Institutionen för geovetenskaper överväger att gå över till denna teknik och därmedbehövdes distrometern utvärderas för olika faktorer som kan påverka instrumentet.Vid jämförelse mellan instrumenten visade det sig att distrometern totalt sett samladein mer nederbörd än de andra mätarna. Det är svårt att avgöra vad skillnaden mellaninstrumenten kan bero på men felkällor så som avdunstning och vätning hos vippkärletoch manuella mätningar kan ge mindre nederbörd. En annan orsak kan varafelkalibrering av datan från distrometern. Inga samband hittades för vindhastighet,vindriktning och typ av nederbörd mellan de tre instrumenten. En vidare undersökning gjordes för droppstorleksfördelningen för att ge exempelpå fördelar med en distrometer. Droppstorleksfördelningen från distrometernjämfördes med exponentialfördelningen framtagen av Marshall &amp; Palmer (1948).Resultatet visade sig stämma överens med tidigare studier, fördelningen stämmerbra överens för stratiforma väder, men sämre för konvektiva och snö. / Measuring precipitation is important in many areas of research. A relatively newtechnology for measuring precipitation is the optical disdrometer, which measures thefalling velocity and drop size of particles by using lasers. The purpose of this workwas to compare data from a disdrometer with data from a tipping bucket and amanual measurement series from the Department of Earth Sciences at UppsalaUniversity. The comparison between the instruments showed that the disdrometermeasured more precipitation than the tipping bucket and the manual measurements.A reason for this can be due to evaporation and wetting from the tipping bucket andmanual measurement. Errors in calibration of data from the disdrometer may alsohave influence. Furthermore, an analysis of the drop size distribution was done in order todetermine areas of special use for the device. The drop size distribution calculatedfrom the distrometer was compared with the Marshall and Palmer (1948) distribution.The results showed that the MP-distribution was a good fit for stratiform weather;however, for convective clouds and snow the fit was not satisfactory and some otherrelationship should be used instead.

This thesis investigates how a developer can move a desktop application to the web environment. The investigation also includes finding out what are the limitations of a web application and what is not possible to move to the web from the desktop. The question is whether there is any functionality that is gained or lost in the web application after the move. A survey has been conducted to find out what types of problems occur when moving an application from desktop to the web. The authors of this thesis have developed two prototypes for a company who wants to move a limited part of their current desktop application to the web in the future. The prototypes have been developed in Silverlight and ASP.NET. The survey has revealed that one of the disadvantages of web applications is the difficulty in working with local files and hardware on the computer. An information search has suggested that a function in a web application can be carried out faster or slower than in a desktop application depending on the conditions. Silverlight has shown through the practical work that it can make the move to the web easier for companies who are more specialized in desktop applications because there is not much knowledge required for the migration. Silverlight has also shown during the implementation of graphical components that it can easily move functionality such as drag and drop with the aid of its toolkit. The shift from desktop to the web can be seen as building a web application from scratch. The result can be influenced by the experience of the developer in the development of the web or desktop applications. Increased knowledge in the methods and technology used in the development of web applications is a necessity for anyone considering to make the move from the desktop.