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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Electromagnetic imaging of active fault zones /

Bedrosian, Paul Andrew, January 2002 (has links)
Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 144-159).
102

Late Pleistocene kinematics of the central San Jacinto fault zone, southern California /

Ryter, Derek. January 2002 (has links)
Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 131-137). Also available for download via the World Wide Web; free to University of Oregon users.
103

Distribution fault location using short-circuit fault current profile approach

Das, Swagata 09 July 2012 (has links)
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
104

Low-cost assertion-based fault tolerance in hardware and software

Vemu, Ramtilak, 1981- 10 October 2012 (has links)
In the recent past, there has been an increasing demand for low-cost safety critical applications. Custom-off-the-shelf (COTS) processors are preferred for usage in these applications due to their low cost. The reliability provided by these processors, however, is not sufficient to meet the safety requirements of these applications. Furthermore, due to the trends followed by the processor industry to enhance the performance of processors, the reliability provided by these processors is projected to decrease in the future. Traditional techniques for enhancing the reliability of computer systems are not viable for these applications due to the high overheads (and hence cost) incurred by them. This thesis describes fault tolerance techniques tailored for these applications, adhering to the tight overhead constraints in the area, memory, and performance dimensions. Techniques at both the hardware level (to be used by the processor manufacturers) and the software level (to be used by the application developers) are presented. At the hardware level, this thesis presents a technique for detecting faults in the processor control logic, for which techniques proposed previously incur very high overheads. Rather than detect all modeled faults, the technique protects against a subset of faults such that the best possible overall protection is achieved while incurring only permissible overheads. This subset of faults is selected depending on the probability of each individual fault causing damage to the architectural state of the processor and the overhead incurred in protecting against the fault. The technique is validated on control logic modules of an industrial processor. At the software level, this thesis concentrates on a category of errors called control flow errors. We describe an error detection technique which incurs lower overheads than any of the previously proposed techniques while at the same time detecting more errors than all of them. Even these low overheads may be too restrictive for some applications. For such applications, we present a technique for providing the best error detection capability possible at the overheads allowed. Once an error is detected, error recovery actions need to be performed. In this thesis, we present an error correction technique which automatically performs error recovery with a very low latency. The technique reuses the information available from the error detection technique to perform the recovery and hence, does not incur any additional performance penalty. All the techniques proposed at the software level have been integrated with GCC, a commonly used software compiler. This permits the fault tolerance to be incorporated into the application automatically as part of the compilation process itself. Evaluations are performed on SPEC and MiBench benchmark programs using an in-house software error injection framework. / text
105

Fault detection and precedent-free localization in thermal-fluid systems

Carpenter, Katherine Patricia 16 February 2011 (has links)
This thesis presents a method for fault detection and precedent-free isolation for two types of channel flow systems, which were modeled with the finite element method. Unlike previous fault detection methods, this method requires no a priori knowledge or training pertaining to any particular fault. The basis for anomaly detection was the model of normal behavior obtained using the recently introduced Growing Structure Multiple Model System (GSMMS). Anomalous behavior is then detected as statistically significant departures of the current modeling residuals away from the modeling residuals corresponding to the normal system behavior. Distributed anomaly detection facilitated by multiple anomaly detectors monitoring various parts of the thermal-fluid system enabled localization of anomalous partitions of the system without the need to train classifiers to recognize an underlying fault. / text
106

Fault monitoring in hydraulic systems using unscented Kalman filter

Sepasi, Mohammad 05 1900 (has links)
Condition monitoring of hydraulic systems is an area that has grown substantially in the last few decades. This thesis presents a scheme that automatically generates the fault symptoms by on-line processing of raw sensor data from a real test rig. The main purposes of implementing condition monitoring in hydraulic systems are to increase productivity, decrease maintenance costs and increase safety. Since such systems are widely used in industry and becoming more complex in function, reliability of the systems must be supported by an efficient monitoring and maintenance scheme. This work proposes an accurate state space model together with a novel model-based fault diagnosis methodology. The test rig has been fabricated in the Process Automation and Robotics Laboratory at UBC. First, a state space model of the system is derived. The parameters of the model are obtained through either experiments or direct measurements and manufacturer specifications. To validate the model, the simulated and measured states are compared. The results show that under normal operating conditions the simulation program and real system produce similar state trajectories. For the validated model, a condition monitoring scheme based on the Unscented Kalman Filter (UKF) is developed. In simulations, both measurement and process noises are considered. The results show that the algorithm estimates the iii system states with acceptable residual errors. Therefore, the structure is verified to be employed as the fault diagnosis scheme. Five types of faults are investigated in this thesis: loss of load, dynamic friction load, the internal leakage between the two hydraulic cylinder chambers, and the external leakage at either side of the actuator. Also, for each leakage scenario, three levels of leakage are investigated in the tests. The developed UKF-based fault monitoring scheme is tested on the practical system while different fault scenarios are singly introduced to the system. A sinusoidal reference signal is used for the actuator displacement. To diagnose the occurred fault in real time, three criteria, namely residual moving average of the errors, chamber pressures, and actuator characteristics, are considered. Based on the presented experimental results and discussions, the proposed scheme can accurately diagnose the occurred faults.
107

Line fault location in emerging HVDC transmission systems

Nanayakkara, Obada Mudalige Kasun Kavinda 11 April 2014 (has links)
The current technology used for location of permanent faults in high voltage direct current (HVDC) transmission lines and cables is based on the travelling-wave principle. This technology has served well for the conventional point-to-point HVDC systems, but is inadequate to handle emerging HVDC transmission configurations such as schemes with very long overhead lines or cables, schemes with a combination of cable and overhead line segments, and multi-terminal HVDC (MTHVDC) schemes. This research investigated accurate and economical ways to locate the faults on dc transmission lines in the aforementioned emerging HVDC transmission configurations. The accuracy of travelling-wave based fault location methods is highly dependent on the accuracy of measuring the time of arrival of the fault generated travelling waves. Investigations showed that post-processing of detection signals such as the line terminal voltages or surge capacitor currents with continuous wavelet transform yields consistent and accurate fault location results. This method was applied for fault location in HVDC systems with extra-long overhead lines and cables using only the terminal measurements. Simulation results verified the effectiveness of this method in locating the faults in a 2400 km long overhead line and a 300 km long underground cable. A new algorithm was proposed to locate the faults in a two-terminal HVDC system consisting of multiple segments of overhead lines and cables, using only the terminal measurements. Application of the proposed algorithm was analysed through detailed simulations. Correct performance was verified under various scenarios. A new algorithm was developed for locating the faults in a star-connected MTHVDC network. This algorithm is also required only the terminal measurements. Its effectiveness was verified through detailed simulations. Finally, a novel measurement scheme for detection of travelling-wave arrival times was proposed. A prototype of this measurement scheme which uses a Rogowski coil to measure the transient currents through the surge capacitors at the line terminals was implemented. Its effectiveness was validated through field tests in a real HVDC transmission system. The proposed measurement scheme could capture significantly clean signals in an actual substation environment, confirming the practicability of implementing the proposed new algorithms.
108

Automated fault localization a statistical predicate analysis approach /

Hu, Peifeng. January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.
109

The initiation and evolution of ignimbrite faults, Gran Canaria, Spain

Soden, Aisling Mary. January 2008 (has links)
Thesis (Ph.D.) - University of Glasgow, 2008. / Ph.D. thesis submitted to the Department of Geographical and Earth Sciences, Faculty of Physical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.
110

Mean kinematic vorticity of retrograde mylonite in the Brevard fault zone, South Carolina

Tu, Ching, January 2009 (has links) (PDF)
Thesis (M.S.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Nov. 4, 2009). Thesis advisors: Robert D. Hatcher, Micah J. Jessup. Vita. Includes bibliographical references.

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