The avalanche of data from scientific instruments and the ensuing interest from geographically distributed users to analyze and interpret it accentuates the need for efficient data dissemination. An optimal data distribution scheme will find the delicate balance between conflicting requirements of minimizing transfer times, minimizing the impact on the network, and uniformly distributing load among participants. We identify several data distribution techniques, some successfully employed by today's peer-to-peer networks: staging, data partitioning, orthogonal bandwidth exploitation, and combinations of the above. We use simulations to explore the performance of these techniques in contexts similar to those used by today's data-centric scientific collaborations and derive several recommendations for efficient data dissemination. Our experimental results show that the peer-to-peer solutions that offer load balancing and good fault tolerance properties and have embedded participation incentives lead to unjustified costs in today's scientific data collaborations deployed on over-provisioned network cores. However, as user communities grow and these deployments scale, peer-to-peer data delivery mechanisms will likely outperform other techniques.

Electromigration in metal lines has re-emerged as a significant concern in modern VLSI circuits. The higher levels of temperature and the large number of EM checking strategies, have led to a situation where trying to guarantee EM reliability often leads to conservative designs that may not meet the area or performance specs. Due to their mostly-unidirectional currents, the problem is most significant in power grids. Thus, this work is aimed at reducing the pessimism in EM prediction. There are two sources for the pessimism: the use of the series model for EM checking, and the pessimistic assumptions about chip workload. Therefore, we propose an EM checking framework that allows users to specify conditions-of-use type constraints to capture realistic chip workload, and which includes the use of a novel mesh model for EM prediction in the grid, instead of the traditional series model.

The development of wide-area networks and the availability of powerful computers as low-cost commodity components are changing the face of computation. These progresses in technology make it possible to utilize geographically distributed resources in multiple owner domains to solve large-scale problems in science, engineering and commerce. Research on this topic has led to the emergence of Grid computing. To achieve the promising potentials of tremendous distributed resources in the Grid, effective and efficient scheduling algorithms are fundamentally important. However, scheduling problems are well known for their intractability, and many of instances are in fact NP-Complete. The situation becomes even more challenging in the Grid circumstances due to some unique characteristics of the Grid. Scheduling algorithms in traditional parallel and distributed systems, which usually run on homogeneous and dedicated resources, cannot work well in the new environments. This work focuses on workflow scheduling algorithms in the Grid scenario. New challenges are discussed, previous research in this realm is surveyed, and novel heuristic algorithms addressing the challenges are proposed and tested. The proposed algorithms contribute to the literature by taking the following factors into account when a schedule for a DAG-based workflow is produced: predictable performance fluctuation and non-deterministic performance model of Grid resources, the computation and data staging co-scheduling, the clustering characteristic of Grid resource distribution, and the ability to reschedule according to performance change after the initial schedule is made. The performance of proposed algorithms are tested and analyzed by simulation under different workflow and resource configurations. / Thesis (Ph.D, Computing) -- Queen's University, 2009-04-23 22:30:09.646

Resilience Engineering has evolved during the recent century and could be a good complement to the prevailing ideas concerning safety within the air traffic industry. The concept of Resilience Engineering stresses the fact that in order to keep up the high standard of safety, there must be greater attention directed to the importance of being proactive, and to implement measures before dangerous situations arises. The purpose of our work was to develop the Resilience Analysis Grid (RAG) to help LFV, the leading Air Navigation Service Provider in Sweden, to identify their ability to deal with disturbances and unexpected events. By testing our RAG on seven active air traffic controllers and operational managers, we were able to produce a final set of assertions, with a total number of 22 items, which LFV (or other similar organisations) can use as a foundation for future RAG studies. As a first attempt we also rated the answers which gave us an opportunity to produce a star diagram, showing the relationship between the areas covered by the RAG. During the interviews we discovered that resilience is already today in many aspects a big part of the everyday work and that the RAG method can therefore be applicable in the industry with some modification. However, there are certain areas within LFV that we believe there is room for improvements. We believe that the RAG could serve as a helpful tool in identifying these areas as well as assisting LFV in their striving to remain one of the safest organisations in the world.

Electromigration in metal lines has re-emerged as a significant concern in modern VLSI circuits. The higher levels of temperature and the large number of EM checking strategies, have led to a situation where trying to guarantee EM reliability often leads to conservative designs that may not meet the area or performance specs. Due to their mostly-unidirectional currents, the problem is most significant in power grids. Thus, this work is aimed at reducing the pessimism in EM prediction. There are two sources for the pessimism: the use of the series model for EM checking, and the pessimistic assumptions about chip workload. Therefore, we propose an EM checking framework that allows users to specify conditions-of-use type constraints to capture realistic chip workload, and which includes the use of a novel mesh model for EM prediction in the grid, instead of the traditional series model.

The thesis describes a development of simple and low engineering cost Single Cycle Controlled grid connected inverter. The voltage source current controlled inverter aims to support low voltage grid from small scale distributed power sources. Single Cycle Controller uses real time current to control PWM switching of the inverter. The controller forces output current to have the same phase as an ordered AC signal. The inverter supports the grid at unity power factor if the AC signal is taken directly from the grid. Use of a generated AC signal is proposed, which allows control over active and reactive current injection or absorption by the inverter. A new synchronized waveform generation method implementable in a microcontroller is proposed in the thesis. A number of Single Cycle Control switching strategies for the H-bridge converter are tested. A hybrid pulse width modulation switching strategy is used as it switches only one switch at high frequency at any time, which reduces switching losses in the bridge and allows easier implementation in hardware. The controller limitation near voltage zero crossing in boost mode is illustrated. Single Cycle Control faces results in current distortion near voltage zero crossings. Strategies to manage this are presented. The inverter is simulated in PSCAD and hardware prototype is built. The prototype results are presented for current injection into the grid at unity power factor.

Resilience Engineering has evolved during the recent century and could be a good complement to the prevailing ideas concerning safety within the air traffic industry. The concept of Resilience Engineering stresses the fact that in order to keep up the high standard of safety, there must be greater attention directed to the importance of being proactive, and to implement measures before dangerous situations arises. The purpose of our work was to develop the Resilience Analysis Grid (RAG) to help LFV, the leading Air Navigation Service Provider in Sweden, to identify their ability to deal with disturbances and unexpected events. By testing our RAG on seven active air traffic controllers and operational managers, we were able to produce a final set of assertions, with a total number of 22 items, which LFV (or other similar organisations) can use as a foundation for future RAG studies. As a first attempt we also rated the answers which gave us an opportunity to produce a star diagram, showing the relationship between the areas covered by the RAG. During the interviews we discovered that resilience is already today in many aspects a big part of the everyday work and that the RAG method can therefore be applicable in the industry with some modification. However, there are certain areas within LFV that we believe there is room for improvements. We believe that the RAG could serve as a helpful tool in identifying these areas as well as assisting LFV in their striving to remain one of the safest organisations in the world.

Smart grids seem to be the solution to use energy from renewable and intermittent energy sources in an efficient manner. There are many research projects around the world and two of them are Jeju Smart Grid Test-bed and Smart Grid Gotland. They have in common that they are both island-based projects and connected to the Powergrid on the mainland by HVDC-link. The purpose of this thesis is to compare the two projects and find out what challenges and strategies they have related to wind power integration. The objective of the two projects were somewhat different. Jeju Smart Grid Test-bedare the starting point for South Korea’s smart grid road map, where the objective ultimately is to construct a smart grid on a national scale in South Korea. For Smart Grid Gotland there are three main focus areas; electricity market, power quality and wind power integration. In this thesis focus is on wind power integration. Wind power integration in smart grids would benefit from energy storage technology connected to the wind power-park to even out the power output. Properties for a potential energy storage connected to Näsudden wind power park situated on the southern tip of Gotland has been investigated and the result is that such an energy storage would likely need to be big and expensive, but able to stabilize the power output.

Power grid voltage integrity verification requires checking if all the voltage drops on the grid are less than a certain threshold that guarantees proper circuit operation. This thesis addresses the problem of correcting the grid when some voltage drops exceed this threshold by making minor modifications to the existing design. The method uses current constraints that capture the uncertainty about the underlying circuit behavior to find the maximum voltage drop on the grid, and then to estimate the voltage drop as a function of the metal widths on the grid. It formulates a nonlinear optimization problem and finds the required change in widths that reduces the maximum voltage drop on the grid below the threshold while keeping the total area cost at a minimum.

Power grid voltage integrity verification requires checking if all the voltage drops on the grid are less than a certain threshold that guarantees proper circuit operation. This thesis addresses the problem of correcting the grid when some voltage drops exceed this threshold by making minor modifications to the existing design. The method uses current constraints that capture the uncertainty about the underlying circuit behavior to find the maximum voltage drop on the grid, and then to estimate the voltage drop as a function of the metal widths on the grid. It formulates a nonlinear optimization problem and finds the required change in widths that reduces the maximum voltage drop on the grid below the threshold while keeping the total area cost at a minimum.