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RISS 인기검색어
- 검색키워드
- 저자 : Singh, Kulwinder (검색결과 390 건)
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Querying Patterns in High-Dimensional Heterogenous Datasets
Singh, Vishwakarma University of California, Santa Barbara 2012 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
The recent technological advancements have led to the availability of a plethora of heterogenous datasets, e.g., images tagged with geo-location and descriptive keywords. An object in these datasets is described by a set of high-dimensional feature vectors. For example, a keyword-tagged image is represented by a color-histogram and a word-histogram. Analyzing these datasets gives better insights into the processes generating the datasets, opens new frontiers of scientific research, and fuels development of life-changing products. An effective mechanism for exploring these heterogenous datasets is querying. One such kind of query is a pattern query. Given a heterogenous dataset and a query, the task here is to find a set of objects which are constrained by a relationship and satisfy the query. For example, given a dataset of keyword-tagged objects, a useful pattern query is to find a set of similar objects that contains a given set of keywords. Querying patterns in high-dimensional heterogenous datasets brings about a new set of computational challenges. High performance algorithms to efficiently and accurately query patterns are presented in this thesis. First, a scalable algorithm, SIMP, is described for accurately querying near neighbors in a high-dimensional dataset. SIMP significantly outperforms the state-of-the-art techniques. Next, a novel algorithm, ProMiSH, is proposed for efficiently querying patterns by keywords. ProMiSH has a speed-up of more than four orders over the state-of-the-art techniques. Then, an algorithm, QUIP, is described for querying patterns by example in a spatial dataset, e.g., geographical maps. QUIP offers an improvement of 87% in running time over the baseline approach. Next, an algorithm for querying patterns by example in a temporal dataset is described. It specifically solves the problem of finding duplicate videos. The proposed algorithm yields a practical query time for video duplicate detection. Finally, a scalable method to compute statistical significance of results of a multi-object query is discussed. Statistical significance or p-value provides a more useful criterion for ranking the results of a query.
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(A) study on the design and application of pump-turbine system for ocean renewable ESS
Singh, Patrick Mark Mokpo National University 2018 국내박사
In Korea, the performance of some pumped storage plants that were constructed since 1980s have become unsatisfactory after long periods of operation. Redesign of the pump-turbine impeller for these plants has become necessary. Currently, the design technology of pump-turbine is monopolized by foreign companies and there is a lack of development of independent design ability in Korea. The first part of this study is an attempt to design a pump-turbine impeller that will contribute to the development of pump-turbines in Korea. The study has focused on initial designs of two types of hydraulic designs. The first design is by the selection of the discharge speed constant from centrifugal pump design and the second design is by the selection of the gradient of discharge variation to the gradient of head variation. The study shows that the second design method is better suited for obtaining a good initial design. However, these are not complete designs, so assumptions have been made to complete the design process. Some important factors have been highlighted for an initial design. Additionally, actual dimensions of the pump-turbines are not publicly available. Moreover, small hydro is also a valuable source of energy for remote area power generation. Pump-turbines are one of the most efficient ways to make and utilize the hydro energy. The second part of the study focuses on the design of a pump-turbine model using CFD and experiments conducted for performance prediction, validation and cavitation investigation. The pump-turbine system is installed using an existing Francis turbine experiment model facility, so the overall casing and draft tube dimensions of the pump-turbine are the same as the existing Francis turbine. Only the dimensions of the stay vanes, guide vanes and impeller are different. Several impeller designs were investigated to match the design requirements of the model test facility. The performance and internal flow characteristics of the initial and final designs are compared, and the best design is suggested for manufacturing for testing in the model test facility. The CFD and experiment results in both modes achieves 85% in hydraulic efficiency. A method of J-groove is applied to the draft tube to suppress the unsteady flow that occurs in turbine mode. Satisfactory results have been obtained that show the J-Groove is effective in suppressing cavitation. A deeper study of pressure pulsations has also been conducted. The third part of the study proposes an application of small sized pumped storage system that can be beneficial on islands or other remote locations that have access to other renewable energies to develop into a hybrid system. Korea has a myriad of islands in the south-western coast that extensively rely on diesel generators for power production, which increases cost and environmental pollution. The small hydro pump-turbine system for ocean renewable energy storage system is a kind of hybrid system that can reduce the usage of diesel generators and contribute to the environment in a positive manner by helping to reduce carbon emissions. The study focuses on the facility capacity calculation and beneficial cost for economic feasibility; and then concentrates on the initial hydraulic design and numerical analysis of a 30 kW-class pump-turbine system for energy independent islands in Korea. The purpose of the study is to propose an ocean renewable energy storage system using a small pump-turbine system working with seawater. A 30kW-class pump-turbine does not require a large head; approximately 30m is sufficient for the design and test facility. Several other renewable energy systems like wind turbines, tidal turbines, wave energy converters and solar energy could be used to make a hybrid system with the pump-turbine. The initial design achieved more than 85% efficiency in both pump and turbine modes. In the future, further optimizations of the impeller blade shape, number of guide vane and stay vanes could improve the overall efficiency of the system.
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