In this thesis, a long-term operation direct methanol fuel cell (DMFC) stack is developed. In order to reach this goal required in many ways, including select highly chemical stability materials, operating conditions must also be stable, and avoid changing the MEA structure when preserved, then can cause the DMFC to maintain stable operation for a long time. First of all, in order to avoid contaminating electrode, this study find out the chemical instability materials. Second, this study design a device which does not require power then can stability supply consumption fuel, and apply this device in 16-cell DMFC. Finally compare with continuous fuel supply and without fuel supply, two operating conditions performance stability. From these experiments can find out, the DMFC indeed in stable operation for a long time under the appropriate supplement. Traditional fuel supply systems typically using the pump fuel recycling, so the structure is more complex, difficult to reduce the volume, and not conducive to carry. If using a passive operation, fuel completely stored in the reaction Chamber, even though the structure is simple there will be a problem with fuel supply. In recent years, someone use vapors of methanol to supply the fuel, although can use high concentration methanol to extend operating time, but the evaporation rate is difficult to control, the fuel can¡¦t be supplied in time, especially when the large current is needed, and CROSSOVER issues would be difficult to overcome. In our 16-cell DMFC, continues to add appropriate amount of fuel consumed which according to the different current. The fuel supply device with a sliding control plate which can control methanol and water diffusion rate respectively. This device only to provide consumed by reaction and leaked fuel in anode chamber, so that the methanol concentration can maintained in the proper range at anode chamber. This device only use diffusion and gravity effects, don't use a fuel pump, so will not consume DMFC power.

Abstract A one-watt portable air-breathing direct methanol fuel cell stack (called DMFC), which can supply fuel passively and operate steadily, is developed in this thesis. A DMFC to maintain its performance stable, the most important strategy is to keep the methanol concentration in reacting chamber to be proper and stable. A fuel supplying system will be in accordance with the depletion of chemical reaction and the leakage of fuel under different circuit current to supplying fuel. To regulate the methanol and water supplying, a fuel supplying system by gravitation and diffusion forces deliver methanol and water to fill up the consumed fuel to maintain the concentration of methanol solution in anode reaction chamber, by adjusting a sliding gate to control the area of a diffusive membrane and utilizing three cotton threads and hoses to distribute the fuel to proper location. In doing so, the methanol concentration in the anode chamber can keep within an appropriate range, so that the DMFC stack can operate stably for a longer period. Yet the diffusivity of the diffusive membrane is comparatively less, the supply system is not easy to downsize. To reduce the size of portable DMFC, we make use of a fuel plug tank to combine the supply tank and reacting chamber, and thus the cell package is more portable. Between the plug tank and the reacting chamber, the three cotton threads are used to distribute the fuel to proper location. The above two design with no extra auxiliary device; therefore, no extra energy will be consumed. To reduce the fuel leakage, and make more use of fuel, four block films is pasted on the bare area of the nafion membranes in a 16-cell DMFC stack. If no fuel is fed into reaction chamber, this will prolong the cell operation time. Under the condition of 3.7 V (cell phone rated voltage) and the operating current 225 mA, our experiments display that the stacks with the two fuel supplying systems can continuously operate for more than 3 hours with no obvious change in methanol concentration within reaction chamber. The experimental results show that this simple passive fuel supplemental system can really keep the DMFC stack operating stably for a sufficient long period.

Power consumption and device size have been placed at the primary concerns for battery-operated portable applications. Switching converters gain popularity in powering portable devices due to their high efficiency, compact sizes and high current delivery capability. However portable devices usually operate at light loads most of the time and are only required to deliver high current in very short periods, while conventional buck converter suffers from low efficiency at light load due to the switching losses that do not scale with load current. In this research, a novel technique for buck converter is proposed to reduce the switching loss by reducing the effective voltage supply at light load. This buck converter, implemented in TSMC 0.18 micrometers CMOS technology, operates with a input voltage of 3.3V and generates an output voltage of 0.9V, delivers a load current from 1mA to 400mA, and achieves 54 percent ~ 91 percent power efficiency. It is designed to work with a constant switching frequency of 3MHz. Without sacrificing output frequency spectrum or output ripple, an efficiency improvement of up to 20 percent is obtained at light load.

The present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150 degrees C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of >80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.

A new type of heterogeneous carbon fiber bunch bipolar plate developed in our lab is applied to portable pure hydrogen proton exchange membrane fuel cell stacks. Several different types of bipolar plate structures have been designed, and the voltages and currents of these fuel cell stacks are measured to compare their performance. The new type of heterogeneous carbon fiber bunch bipolar plate is well in low contact resistance, weight low, small volume and the flexible geometry shape. Due to its flexible structure of carbon fiber bunch, the compressing pressure is small while assembling stack so that the electrode can not be over compressed and out of shape. Therefore the high porosity of diffusion layer can be keep and reaction gas can enter and distribute to all reaction areas easily. For using to portable equipments, a small 6-cell flat type of fuel cell stack are developed firstly. The total weight is about 75g and the total volume is about 68cm . The second stack is cylinder-type(I) fuel cell stack. The total weight is about 60g and the total volume is about 71cm . The third stack is cylinder-type (II). The total weight has been reduced to about 20g and the total volume has been reduced to about 30cm . Above three kinds of the 6-cell stacks the total electrode area is 13.5cm . Using Nafion, the catalyst content anode Pt 0.4mg/cm , cathode Pt 1.0mg/cm , On room temperature and inlet hydrogen gauge pressure 0.15atm air-breathing, total output power of the cylinder (II) can reach 1.85W, and the power density of unit area can reach about 137mW/cm^2.

<p>USB has become a popular interface for exchanging data between PC’s and peripherals. An increasing number of portable peripherals are using the USB interface to communicate with the PC.The design and implementation of a synthesizable model of the USB 1.1 protocol engine is presented in this report The PHY is compatible with the USB 1.1 transceiver macrocell interface (UTMI) specification and the simulation test confirmed the successful operation of circuits for both full speed (12 Mbps) and low speed (1.5 Mbps) data transmission. the model is written completely in behavioral verilog with a top down approach and the model was verified and validated.</p>

<p>The purpose of this thesis is to develop a remote control application for personal computers. This application will have two devices implied, the computer to be controlled and a small portable device that will be used as remote controller.</p><p>In this specific case, the portable device picked is the Nintendo DS, for reasons discussed later in this document that make this device interesting as a remote controller.</p><p>The application should allow the final user to create his own set of remote controllers for any computer application he wants to control, and also, to define the commands the application should perform. This makes the developed solution a full customizable universal remote controlling application.</p><p>The first step taken was to do a small research about what kind of devices and software are present actually for remote control applications, so the differences, advantages and disadvantages of using the Nintendo DS will be shown. Then the developed solution will be explained and tested, controlling some computer applications under different scenarios.</p>

IH-35 is a major north-south interstate highway across the State of Texas. It is an important business corridor, conveniently connecting four large Texas cities, Austin, Dallas, Fort Worth, and San Antonio, as well as facilitating trade between Mexico and the United States. During construction of the SH-71/IH-35 Interchange, the Austin District of the Texas Department of Transportation (TxDOT) has had to close the main lanes of IH-35 and re-route traffic. Three main lane closures happened during three weekends in 2011. During those closures, a parallel route, the SH-130 toll road, was made free to travelers. TxDOT provided both pre-trip and en-route information about the closure. They used radio, TV, portable message sign (PMS), and dynamic message signs (DMS) to inform commuters about the closure. To inform travelers passing through Austin about the closure and the existing alternative (SH-130 was toll free), they even collaborated with Dallas and San Antonio TxDOT district personnel. However, usage of SH130 was less than anticipated, and there was significant traffic queuing on IH-35. In this study, we tried to document the quantity of traffic that used the alternative path during the IH-35 closure and explore options for relieving delays on IH-35 during future closures. / text

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Tidigare studier har indikerat att extroverta personer använder mobiltelefoni mer än vad introverta personer gör (Inyang et al. 2010). En enkätstudie genomfördes för att testa sambandet mellan personlighetstyp och huruvida en frekvenspreferens gällande brukandet av mobiltelefoni eller portabelt ljud förelåg. Hundra stycken deltagare svarade på enkäten som bestod av tre delar. Fyra hypoteser var formulerade; extroverta förutspåddes vara flitigare brukare av mobiltelefon än introverta, medan introverta förutspåddes vara flitigare i brukandet av portabelt ljud. Personer med social fobi förutspåddes använda mindre mobiltelefoni, men mer portabelt ljud, än personer utan social fobi. Neurotiker förutspåddes använda portabelt ljud i större utsträckning än de brukar mobiltelefoni. En skillnad förutspåddes finnas mellan män och kvinnor gällande användande av mobiltelefoni och portabelt ljud. Resultaten visade inte på något samband mellan extraversion eller social fobi och användningsfrekvens gällande mobiltelefon, eller portabelt ljud vilket inte stöder hypotesen, däremot så fanns ett samband mellan neuroticism och användningsfrekvens vilket delvis stöder hypotesen och förövrigt indikerar resultaten att kvinnor jämfört med män föredrar mobiltelefon framför portabelt ljud i detta avseende. / Previous studies have indicated that extroverts use mobile cell phones more than introverts (Inyang et al. 2010). A survey was carried out to test the relationship between personality type and frequency preference for mobile cell phones and portable sound use. A hundred individuals participated in the survey containing three parts of questions. It was predicted that extroverts will be more active users of mobile phones than introverts, while introverts were predicted to be more active users of portable sound. People with social phobia were predicted to use less of mobile telephony, but more of portable sound, than people lacking social phobia. Neurotics were predicted to use less of mobile telephony, but more of portable sound, than non-neuritics. A gender effect was also predicted. The result did not show any relation between extraversion or social fobia, and mobile phone or portable sound usage, which doesn’t support the hypothesis, on the other hand a relation between neuroticism and mobile phone usage and portable sound usage was supported and women compared to men were also shown to prefer mobile phone to portable sound.