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A novel method of current sensing using resistance of power delivery path is introduced as a mean to measure static or dynamic load current in high-power system-on-chips, where conventional methods deemed inadequate. It is named “IRS” here, and it stands for Inherent Resistance Current Sensing. To explain its application and to provide motivation beyond this work, pros and cons of conventional techniques are reviewed with a look at previous works done in this area. It is followed with review of discreet implementation of the sensor (IRS) in chapter three. The measurements results collected using the discrete circuits are included with an in-depth analysis of the results and compensation techniques. It offers insight to effectiveness of the solution and its potential, while highlighting shortcomings and limitation of discrete implementation. This would set the tone to design integrated version of the sensor. In order to select amplifier architecture, a rundown of common methods to construct the instrumentation amplifier is discussed in chapter 4, primarily based on the latest work already done in this field per cited references. This is to help readers to get an overall view of the challenges and techniques to overcome them. Finally, the architecture for the integrated version of the sensor (IRS) is presented, with a proof of concept design. The design is targeted for low voltage VLSI systems to allow integration within large SoCs such as GPUs and CPUs. The primary block, the instrumentation amplifier, is constructed using rail-to-rail current conveyers and simulated using TSMC 32nm process node. The simulation results are analyzed and observations are provided.

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In the present study we use Argo float data, in-situ shipboard ADCP data,IFREMER wind stress curl data, QuikSCAT wind data and AVISO sea level anomaly data from 2006 to 2010 to investigate hydrographical characteristics and surface and deep currents in the seas surrounding Taiwan. The studied areas consist of the followings: the cyclonic eddy off the northeastern Taiwan coast, flow structure of the Luzon Strait, anticyclonic eddies off the southwestern Taiwan coast and east of Kuroshio. Our results found that some Argo floats drifting northward with the Kuroshio were occasionally intruded to the continental shelf off the northeastern Taiwan at 25¢XN-26¢XN,122¢XE-123¢XE. Statistics indicate that this phenomenon occurs most frequently in winter, and float profiling data reveal a marked upwelling above 150m depth. Temperature drops within this area can reach 5.1¢J and 8¢J, respectively at 50m and 100m depths. A deep southward current with a maximum speed of 30 cms can be found to exist between northeastern Taiwan and Kuroshio. On the other hand, Surface flows have strong seasonal variations in the Luzon strait, i.e., toward the southeastern side of Taiwan in the summer and intrude into the South China Sea (SCS) in the fall and winter. Deep currents in the Luzon Strait, however, flow mostly into the SCS regardless of seasonality. Maximum speed of deep current can reach 6 cms . Mixed-layer depth in the northern SCS is approximately 50m in the spring and summer, and about 110m depth in winter. The third part of this thesis concerns with the anticyclonic circulation off the southwestern Taiwan coast. Float observations show that this circulation exists almost all year round in 2009. Surface currents have a maximum speed in early May, reaching 104 cms , and the wind stress curl attains a maximum negative value. It is conjectured that this anticyclonic eddy is generated primarily due to the restriction of local coast and topography, and the wind stress curl is the secondary mechanism. Surface current derived from Shipboard ADCP is also consistent with the float results. The diameter of this eddy is about 110 km. T-S characteristics of Kuroshio can be observed at 150-210m depth, indicating a close link between this eddy and the Kuroshio. Finally, anticyclonic warm eddies east of Kuroshio are also investigated from the float data. It is found that the eddy flow structure in this region is more obvious in depths than in surface. Temperature distribution below the depth of 200 m also confirms the warm core structure. At an event during which when one float incidentally travelling through a cold eddy and an adjacent warm eddy, the temperature difference can reach 4.5 ¢J at 160m depth. The warm eddies are found to be more stable and more frequently observed than the cold eddies in this region.

In this thesis, we design electrode shape of light emitter diode (LED) to help the current diffusing uniformly. The purpose of the uniform current is to avoid the waste heat from the devices and enhance the efficiency of active region. The LED samples adopted in this study are GaN base materials grown on sapphire. The P-N electrodes must be processed on the same side since the poor conductivity of sapphire. The same side P-N electrode will results in current crowding phenomena. We design special electrode shapes to make the current diffuse uniformly and reduce the current crowding phenomena. First, we use COMSOL simulation software to simulate the current spreading between the electrodes. We adopt the same parameters from the reference papers to confirm the reliabilities of the simulation. Then we simulate several electrode shapes with highly uniform current spreading. Second, we use the simulation results to fabricate electrode on chips. The first set is LED without transparent conductive layer. This set is to confirm whether the fabrication processes is feasible and adjust the simulation parameters at the same time. The second set is LED with transparent conductive layer. The experimental emission intensity has deviation from the simulation results. We deduce the emission intensities from smaller LED chip size will have great influence on illumination surface. The third set is electrodes fabricated on large size LED chip. The electrode patterns successfully enhance the uniformity of current spreading, and enhance the output light intensity of 21%. The current density distribution trend from simulation is matched with the illumination intensities.

While evaluating the depth of corrosive defect of the pipe through Remote Field Eddy Current (RFEC) Testing technology, the critical principle of the process is to use the interaction of the magnetic field. Generally, exciter coils in the low-frequency alternating current and detector coils can generate the magnetic field. The signal curve can be transformed by receiving and plotting the induction voltage of detector coils. In addition, the signal curve can be used to identify the existence and the depth of corrosive defect from the shape and angle of the curve. Thus, the structure of the detector has a great influence on the exactitude of the testing. However, in the real experiment, RFEC probe is covered by shell and hard to disassemble. Thus, few people doing the research to analyze the structure of the RFEC probes. This research is based on two-dimensional axial-symmetry models and using Finite Element Method to simulate different structures or designs, such as the distance between exciter coils and detector coils, the amplitude and frequency of current in exciter coils, and even the material and size of shield. The simulation results show the influences of changing these important characteristics. Therefore, with these scenarios, the RFEC testing technology can be understood more completely and be improved the accuracy and reliability of the experiment by optimizing the sensibility of the RFEC probe.

Popularly used impedance-based methods need voltage and current waveform as well as line impedance per unit length to estimate distance to fault location. For a non-homogenous system with different line configuration, these methods assume that the system is homogenous and use the line impedance of the most frequently occurring line configuration. Load present in the system before fault is an important parameter which affects fault location accuracy. Impedance-based methods like Takagi and positive-sequence method assume that the load is lumped beyond the fault point which may not be true for a typical distribution system. As a result, accuracy of the impedance-based methods in estimating distance to fault is affected. Another short-coming of impedance-based methods are that they are unable to identify the branch in which the fault may be located. To minimize these errors, this thesis proposes a short-circuit fault current profile approach to complement impedance-based algorithms. In the short-circuit fault current profile approach, circuit model of the distribution feeder is used to place faults at every bus and the corresponding short-circuit fault current is plotted against reactance or distance to fault. When a fault occurs in the distribution feeder, fault current recorded by relay is extrapolated on the current profile to get location estimates. Since the circuit model is directly used in building the current profile, this approach takes into account load and non-uniform line impedance. Using the estimates from short-circuit fault current profile approach and impedance-based methods, the path on which the fault is located is identified. Next to improve fault location estimates, a median value of the estimates is computed. The median is a more robust estimate since it is not affected by outliers. The strategy developed above is tested using modified IEEE 34 Node Test Feeder and validated against field data provided by utilities. For the IEEE 34 Node Test Feeder, it is observed that the median estimate computed from impedance-based methods and the short-circuit fault current profile approach is very close to the actual fault location. Error in estimation is within 0.58 miles. It was also observed that if a 0.6 mile radius is built around the median estimate, the fault will lie within that range. Now the IEEE 34 Node Test Feeder represents a typical distribution feeder and has also been modeled to represent the worst case scenario, i.e. load current is around 51% of the fault current for the farthest bus. Hence the 0.6 mile radius around the median estimate will hold true for most distribution feeders and will be used when computing the fault range for field case events. For the field events, it was seen that the actual faults indeed lie within the 0.6 mile radius built around the median estimate and the path of the fault location has also been accurately estimated. For certain events, voltage waveform was not useful for analysis. In such situations, short-circuit fault current profile alone could be used to estimate fault location. Error in estimation is within 0.1 miles, provided the circuit model closely represents the distribution feeder. / text