Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Parallel Architectures for Planetary Exploration Requirements (PAPER)

The Parallel Architectures for Planetary Exploration Requirements (PAPER) project is essentially research oriented towards technology insertion issues for NASA's unmanned planetary probes. It was initiated to complement and augment the long-term efforts for space exploration with particular reference to NASA/LaRC's (NASA Langley Research Center) research needs for planetary exploration missions of the mid and late 1990s. The requirements for space missions as given in the somewhat dated Advanced Information Processing Systems (AIPS) requirements document are contrasted with the new requirements from JPL/Caltech involving sensor data capture and scene analysis. It is shown that more stringent requirements have arisen as a result of technological advancements. Two possible architectures, the AIPS Proof of Concept (POC) configuration and the MAX Fault-tolerant dataflow multiprocessor, were evaluated. The main observation was that the AIPS design is biased towards fault tolerance and may not be an ideal architecture for planetary and deep space probes due to high cost and complexity. The MAX concepts appears to be a promising candidate, except that more detailed information is required. The feasibility for adding neural computation capability to this architecture needs to be studied. Key impact issues for architectural design of computing systems meant for planetary missions were also identified

MACHS: Mitigating the Achilles Heel of the Cloud through High Availability and Performance-aware Solutions

Cloud computing is continuously growing as a business model for hosting information and communication technology applications. However, many concerns arise regarding the quality of service (QoS) offered by the cloud. One major challenge is the high availability (HA) of cloud-based applications. The key to achieving availability requirements is to develop an approach that is immune to cloud failures while minimizing the service level agreement (SLA) violations. To this end, this thesis addresses the HA of cloud-based applications from different perspectives. First, the thesis proposes a component’s HA-ware scheduler (CHASE) to manage the deployments of carrier-grade cloud applications while maximizing their HA and satisfying the QoS requirements. Second, a Stochastic Petri Net (SPN) model is proposed to capture the stochastic characteristics of cloud services and quantify the expected availability offered by an application deployment. The SPN model is then associated with an extensible policy-driven cloud scoring system that integrates other cloud challenges (i.e. green and cost concerns) with HA objectives. The proposed HA-aware solutions are extended to include a live virtual machine migration model that provides a trade-off between the migration time and the downtime while maintaining HA objective. Furthermore, the thesis proposes a generic input template for cloud simulators, GITS, to facilitate the creation of cloud scenarios while ensuring reusability, simplicity, and portability. Finally, an availability-aware CloudSim extension, ACE, is proposed. ACE extends CloudSim simulator with failure injection, computational paths, repair, failover, load balancing, and other availability-based modules

Knowledge representation into Ada parallel processing

The Knowledge Representation into Ada Parallel Processing project is a joint NASA and Air Force funded project to demonstrate the execution of intelligent systems in Ada on the Charles Stark Draper Laboratory fault-tolerant parallel processor (FTPP). Two applications were demonstrated - a portion of the adaptive tactical navigator and a real time controller. Both systems are implemented as Activation Framework Objects on the Activation Framework intelligent scheduling mechanism developed by Worcester Polytechnic Institute. The implementations, results of performance analyses showing speedup due to parallelism and initial efficiency improvements are detailed and further areas for performance improvements are suggested

Scheduling Algorithms for Cloud: A Survey and Analysis

Cloud Computing is a fast growing computing paradigm due to the vast benefits it provides to the users. Scheduling becomes one of the key aspects due to the pay-as-you-go nature of the Cloud. The factors affecting the technique of scheduling applied change with change in scenarios. For instance for scheduling in hybrid clouds the data transfer speed has to be taken into consideration whereas for mobile environments scheduling becomes dependent on context change. Moreover scheduling can be improvised on many fronts such as energy efficiency, cost minimization, Maximization of resource utilization, etc. This paper surveys scheduling techniques in various Cloud Computing scenarios and sites the most efficient scheduling technique available for a particular set of user needs by comparing various techniques and the problems they address

Tõrkeid taluv võrk, mis baseerub Linux süsteemil ja kasutab vana riistvara

Networking at enterprise level is fast, reliable,fault-tolerant, expensive and usually includes a vendor lock-in. This thesis tries to take the good qualities of the enterprise level networking and remove the negative side effects. One possible way to solve the problem is to create a networking solution that uses obsolete hardware and free software to neglect the negative properties of enterprise networking. This kind of solution can be achieved without any need for more system administration knowledge or know-how. Moreover, the thesis conducts an analysis of the previous work done by other people on fault tolerance in networking and offers the author’s own solution implementation. The main result of this thesis is a low-cost solution to Internet service provider and router failover. The tests that were carried out show that it is possible to create a network that, even in the case of ISP and/or router failure, can continue functioning at full speed without significant delays and without disrupting the presently occurring data transmission. The thesis’s work uses computer hardware that has been announced old by its previous owners and software that is open source and readily deployable with a little skill. From a theoretical point of view it should be acknowledged that the author understands that software routing is not as good as hardware routing, however the overall idea was to offer a solution which could theoretically perform as similar as possible to the hardware routing