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Resultados filtrados por Publicador: Rochester Instituto de Tecnologia

Energy-aware replica selection for data-intensive services in cloud

Li, Bo
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
45.66%
With the increasing energy cost in data centers, an energy efficient approach to provide data intensive services in the cloud is highly in demand. This thesis solves the energy cost reduction problem of data centers by formulating an energy-aware replica selection problem in order to guide the distribution of workload among data centers. The current popular centralized replica selection approaches address such problems but they lack scalability and are vulnerable to a crash of the central coordinator. Also, they do not take total data center energy cost as the primary optimization target. We propose a simple decentralized replica selection system implemented with two distributed optimization algorithms (consensus-based distributed projected subgradient method and Lagrangian dual decomposition method) to work with clients as a decentralized coordinator. We also compare our energy-aware replica selection approach with the replica selection where a round-robin algorithm is implemented. A prototype of the decentralized replica selection system is designed and developed to collect energy consumption information of data centers. The results show that in the best case scenario of our experiments, the total energy cost using the Lagrangian dual decomposition method is 17.8% less than a baseline round-robin method and 15.3% less than consensus-based distributed projected subgradient method. Also...

Development of deterministic collision-avoidance algorithms for routing automated guided vehicles

Pai, Arun S.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
35.75%
A manufacturing job spends a small portion of its total flow time being processed on machines, and during the remaining time, either it is in a queue or being transported from one work center to another. In a fully automated material-handling environment, automated guided vehicles (AGV) perform the function of transporting the jobs between workstations, and high operational costs are involved in these material-handling activities. Consequently, the AGV route schedule dictates subsequent work-center scheduling. For an AGV job transportation schedule to be effective, the issue of collisions amongst AGV during travel needs to be addressed. Such collisions cause stalemate situations that potentially disrupt the flow of materials in the job shop, adding to the non-value time of job processing, and thus, increase the material handling and inventory holding costs. The current research goal was to develop a methodology that could effectively and efficiently derive optimal AGV routes for a given set of transportation requests, considering the issue of collisions amongst AGV during travel. As part of the solution approach in the proposed work, an integer linear program was formulated in Phase I with the capability of optimally predicting the AGV routes for a deterministic set of transportation requests. Collision avoidance constraints were developed in this model. The model was programmed using OPL / Visual Basic...

Color in scientific visualization: Perception and image-based data display

Zhang, Hongqin
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
Português
Relevância na Pesquisa
45.65%
Visualization is the transformation of information into a visual display that enhances users understanding and interpretation of the data. This thesis project has investigated the use of color and human vision modeling for visualization of image-based scientific data. Two preliminary psychophysical experiments were first conducted on uniform color patches to analyze the perception and understanding of different color attributes, which provided psychophysical evidence and guidance for the choice of color space/attributes for color encoding. Perceptual color scales were then designed for univariate and bivariate image data display and their effectiveness was evaluated through three psychophysical experiments. Some general guidelines were derived for effective color scales design. Extending to high-dimensional data, two visualization techniques were developed for hyperspectral imagery. The first approach takes advantage of the underlying relationships between PCA/ICA of hyperspectral images and the human opponent color model, and maps the first three PCs or ICs to several opponent color spaces including CIELAB, HSV, YCbCr, and YUV. The gray world assumption was adopted to automatically set the mapping origins. The rendered images are well color balanced and can offer a first look capability or initial classification for a wide variety of spectral scenes. The second approach combines a true color image and a PCA image based on a biologically inspired visual attention model that simulates the center-surround structure of visual receptive fields as the difference between fine and coarse scales. The model was extended to take into account human contrast sensitivity and include high-level information such as the second order statistical structure in the form of local variance map...