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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.
1

Improvements on Scientific System Analysis

Grupchev, Vladimir 01 January 2015 (has links)
Thanks to the advancement of the modern computer simulation systems, many scientific applications generate, and require manipulation of large volumes of data. Scientific exploration substantially relies on effective and accurate data analysis. The shear size of the generated data, however, imposes big challenges in the process of analyzing the system. In this dissertation we propose novel techniques as well as using some known designs in a novel way in order to improve scientific data analysis. We develop an efficient method to compute an analytical query called spatial distance histogram (SDH). Special heuristics are exploited to process SDH efficiently and accurately. We further develop a mathematical model to analyze the mechanism leading to errors. This gives rise to a new approximate algorithm with improved time/accuracy tradeoff. Known MS analysis systems follow a pull-based design, where the executed queries mandate the data needed on their part. Such a design introduces redundant and high I/O traffic as well as cpu/data latency. To remedy such issues, we design and implement a push-based system, which uses a sequential scan-based I/O framework that pushes the loaded data to a number of pre-programmed queries. The efficiency of the proposed system as well as the approximate SDH algorithms is backed by the results of extensive experiments on MS generated data.
2

SLA-Aware Adaptive Data Broadcasting in Wireless Environments

Popescu, Adrian Daniel 16 February 2010 (has links)
In mobile and wireless networks, data broadcasting for popular data items enables the efficient utilization of the limited wireless bandwidth. However, efficient data scheduling schemes are needed to fully exploit the benefits of data broadcasting. Towards this goal, several broadcast scheduling policies have been proposed. These existing schemes have mostly focused on either minimizing response time, or drop rate, when requests are associated with hard deadlines. The inherent inaccuracy of hard deadlines in a dynamic mobile environment motivated us to use Service Level Agreements (SLAs) where a user specifies the utility of data as a function of its arrival time. Moreover, SLAs provide the mobile user with an already familiar quality of service specification from wired environments. Hence, in this dissertation, we propose SAAB, an SLA-aware adaptive data broadcast scheduling policy for maximizing the system utility under SLA-based performance measures. To achieve this goal, SAAB considers both the characteristics of disseminated data objects as well as the SLAs associated with them. Additionally, SAAB automatically adjusts to the system workload conditions which enables it to constantly outperform existing broadcast scheduling policies.
3

SLA-Aware Adaptive Data Broadcasting in Wireless Environments

Popescu, Adrian Daniel 16 February 2010 (has links)
In mobile and wireless networks, data broadcasting for popular data items enables the efficient utilization of the limited wireless bandwidth. However, efficient data scheduling schemes are needed to fully exploit the benefits of data broadcasting. Towards this goal, several broadcast scheduling policies have been proposed. These existing schemes have mostly focused on either minimizing response time, or drop rate, when requests are associated with hard deadlines. The inherent inaccuracy of hard deadlines in a dynamic mobile environment motivated us to use Service Level Agreements (SLAs) where a user specifies the utility of data as a function of its arrival time. Moreover, SLAs provide the mobile user with an already familiar quality of service specification from wired environments. Hence, in this dissertation, we propose SAAB, an SLA-aware adaptive data broadcast scheduling policy for maximizing the system utility under SLA-based performance measures. To achieve this goal, SAAB considers both the characteristics of disseminated data objects as well as the SLAs associated with them. Additionally, SAAB automatically adjusts to the system workload conditions which enables it to constantly outperform existing broadcast scheduling policies.

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