An Integrated Analysis of the Physiological Effects of Space Flight: Executive Summary

A large array of models were applied in a unified manner to solve problems in space flight physiology. Mathematical simulation was used as an alternative way of looking at physiological systems and maximizing the yield from previous space flight experiments. A medical data analysis system was created which consist of an automated data base, a computerized biostatistical and data analysis system, and a set of simulation models of physiological systems. Five basic models were employed: (1) a pulsatile cardiovascular model; (2) a respiratory model; (3) a thermoregulatory model; (4) a circulatory, fluid, and electrolyte balance model; and (5) an erythropoiesis regulatory model. Algorithms were provided to perform routine statistical tests, multivariate analysis, nonlinear regression analysis, and autocorrelation analysis. Special purpose programs were prepared for rank correlation, factor analysis, and the integration of the metabolic balance data

Reliability and fault tolerance modelling of multiprocessor systems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Reliability evaluation by analytic modelling constitute an important issue of designing a reliable multiprocessor system. In this thesis, a model for reliability and fault tolerance analysis of the interconnection network is presented, based on graph theory. Reliability and fault tolerance are considered as deterministic and probabilistic measures of connectivity. Exact techniques for reliability evaluation fail for large multiprocessor systems because of the enormous computational resources required. Therefore, approximation techniques have to be used. Three approaches are proposed, the first by simplifying the symbolic expression of reliability; the other two by applying a hierarchical decomposition to the system. All these methods give results close to those obtained by exact techniques.Consejo Nacional de Ciencia y Tecnologia" (National Council for Science and Technology of Mexico) and "Instituto de Investigaciones Electricas" (Institute for Electrical Research

Modelação e Negociação de Flexibilidade em Comunidades de Energia Renovável

The progressive replacement of traditional generation resources with intermittent resources has reduced the available supply-side flexibility and increased the need to unlock flexibility on the demand-side. At the same time, the rising electricity consumption in residential buildings requires an analysis of the potential flexibility of the loads within them to contribute to the operation needs of electrical grids. Lastly, regulations governing self consumption have allowed end consumers to form energy communities based on local electricity markets. This is an additional incentive to define strategies for trading available flexibility at local level, in separate but simultaneously integrated structures within wholesale electricity markets. The proposed dissertation work focuses on studying the flexibility of energy production and consumption by prosumers within a Renewable Energy Community (REC). The objective is to investigate how residential flexibility can be determined, modeled, and aggregated for trading in a local market created for this purpose. The work to be developed will present a two-stage model that determines residential technical flexibility and establishes a local market only for its transaction. In the first stage, the optimal scheduling of domestic devices (flexible units or FUs) for each prosumer is determined, serving as a baseline for comparison, along with the technical limits of flexibility (maximum and minimum possible consumption profiles) for each FU. In the second stage, a market model is established only for flexibility exchanges. The technical flexibility determined in the first stage is offered to the Community Manager (CM) as flexibility offer, with an associated price. This entity acts as an aggregator and simultaneously as the operator of the local market. At this level, the Distribution System Operator (DSO) submits its flexibility requirements for the next day to the CM, who is responsible for executing the clearing process. The pricing of the flexibility offered by prosumers in the market is based on the base energy tariff they are subject to, which corresponds to the cost of their optimal scheduling obtained in the first stage, without considering this flexibility. Therefore, offering flexibility becomes an incentive to reduce prosumers energy costs or increase their utility, complementing their mere participation in energy markets. A case study based on a renewable energy community with a strong penetration of emerging technologies is used to validate and demonstrate the relevance of the proposed approach in terms of determining and activating residential FU flexibility. The obtained results show that participation in the local flexibility market leads to a reduction in prosumers energy costs, around 4.5%, in average. It can be an incentive for prosumers to join RECs that would not only have local energy trading structures but also mechanisms for negotiating and sharing flexibility. In addition, it was evidenced that the impact of electric vehicle chargers and battery energy storage systems on the total flexibility offered and accepted in the market is much greater than that the impact of other small loads studied. This not only constitutes an incentive for the study of the operational flexibility of these resources but also for investments in these emerging technologies.A substituição progressiva dos recursos de geração tradicionais por recursos intermitentes tem reduzido a flexibilidade disponível do lado da oferta e aumentado a necessidade de desbloqueá-la do lado da procura. Ao mesmo tempo, o aumento do consumo de eletricidade nos edifícios residenciais obriga a que seja analisada a flexibilidade potencial das cargas que o constituem, de modo a contribuir para as necessidades de operação das redes elétricas. Por último, a regulamentação do autoconsumo, tem permitido aos consumidores finais constituir comunidades energéticas baseadas em mercados locais de eletricidade. Isto torna ainda mais importante a definição de estratégias para comercializar a flexibilidade disponível a esse nível, em estruturas de mercado local separadas, mas simultaneamente integradas nos mercados grossistas de eletricidade. O trabalho proposto para dissertação assenta no estudo da flexibilidade da produção e consumo de energia por parte dos prosumidores de uma Comunidade de Energia Renovável. O objetivo é estudar como a flexibilidade residencial pode ser determinada, modelada e agregada de modo a ser transacionada num mercado local criado para esse fim. Assim, o trabalho a ser desenvolvido apresentará um modelo de dois estágios que determina a flexibilidade técnica residencial e cria um mercado local exclusivo para transaciona-la. Numa primeira fase, determina-se o escalonamento óptimo dos dispositivos domésticos (unidades flexíveis ou UF) de cada prosumidor, o que constitui uma baseline de comparação, bem como os limites técnicos de flexibilidade (perfis de consumo máximos e mínimos possíveis) de cada UF. Num segundo estágio, é estabelecido um modelo de mercado apenas para trocas de flexibilidade. A flexibilidade técnica determinada no primeiro estágio é disponibilizada ao Gestor de Comunidade (CM), enquanto oferta de flexibilidade, com um preço associado. Esta entidade desempenha as funções de agregador e simultaneamente de operador do mercado local. A este nível, o Operador do Sistema de Distribuição (ORD) submete os seus requisitos de flexibilidade, para o dia seguinte, ao CM, que é responsável pelo executar o clearing. A precificação da flexibilidade oferecida pelos prosumidores em mercado é feita com base no valor da tarifa base de energia a que estão sujeitos, que corresponde ao custo do seu escalonamento ótimo, obtido no primeiro estágio, que não considera essa mesma flexibilidade. Portanto, oferecer flexibilidade torna-se um incentivo para reduzir os custos energéticos dos prosumidores ou aumentar a sua utilidade, o que complementa a sua mera participação nos mercados de energia. Um caso de estudo baseado numa comunidade de energia com forte penetração de tecnologias emergentes é utilizado e valida a metodologia desenvolvida. Para além disso é evidenciada a relevância da abordagem proposta em termos de determinação e ativação da flexibilidade de UFs residenciais os impactos das mesmas no fecho de mercado. Os resultados evidenciam que participação no mercado local de flexibilidade induz uma redução dos custos energéticos dos prosumidores, na casa 4.5%, em média. O impacto dos carregadores de veículos elétricos e dos sistemas de armazenamento de energia em baterias na flexibilidade total oferecida e aceite em mercado é muito superior ao de outras pequenas cargas estudadas. Tudo isto pode vir a resultar num incentivo ao investimento nos recursos referidos, bem como à associação de prosumidores em comunidades de energia renovável, onde para além de estruturas locais de comercialização de energia, existam outras que permitam a negociação e partilha de flexibilidade

Framework for simulation of fault tolerant heterogeneous multiprocessor system-on-chip

Due to the ever growing requirement in high performance data computation, current Uniprocessor systems fall short of hand to meet critical real-time performance demands in (i) high throughput (ii) faster processing time (iii) low power consumption (iv) design cost and time-to-market factors and more importantly (v) fault tolerant processing. Shifting the design trend to MPSOCs is a work-around to meet these challenges. However, developing efficient fault tolerant task scheduling and mapping techniques requires optimized algorithms that consider the various scenarios in Multiprocessor environments. Several works have been done in the past few years which proposed simulation based frameworks for scheduling and mapping strategies that considered homogenous systems and error avoidance techniques. However, most of these works inadequately describe today\u27s MPSOC trend because they were focused on the network domain and didn\u27t consider heterogeneous systems with fault tolerant capabilities; In order to address these issues, this work proposes (i) a performance driven scheduling algorithm (PD SA) based on simulated annealing technique (ii) an optimized Homogenous-Workload-Distribution (HWD) Multiprocessor task mapping algorithm which considers the dynamic workload on processors and (iii) a dynamic Fault Tolerant (FT) scheduling/mapping algorithm to employ robust application processing system. The implementation was accompanied by a heterogeneous Multiprocessor system simulation framework developed in systemC/C++. The proposed framework reads user data, set the architecture, execute input task graph and finally generate performance variables. This framework alleviates previous work issues with respect to (i) architectural flexibility in number-of-processors, processor types and topology (ii) optimized scheduling and mapping strategies and (iii) fault-tolerant processing capability focusing more on the computational domain; A set of random as well as application specific STG benchmark suites were run on the simulator to evaluate and verify the performance of the proposed algorithms. The simulations were carried out for (i) scheduling policy evaluation (ii) fault tolerant evaluation (iii) topology evaluation (iv) Number of processor evaluation (v) Mapping policy evaluation and (vi) Processor Type evaluation. The results showed that PD scheduling algorithm showed marginally better performance than EDF with respect to utilization, Execution-Time and Power factors. The dynamic Fault Tolerant implementation showed to be a viable and efficient strategy to meet real-time constraints without posing significant system performance degradation. Torus topology gave better performance than Tile with respect to task completion time and power factors. Executing highly heterogeneous Tasks showed higher power consumption and execution time. Finally, increasing the number of processors showed a decrease in average Utilization but improved task completion time and power consumption; Based on the simulation results, the system designer can compare tradeoffs between a various design choices with respect to the performance requirement specifications. In general, designing an optimized Multiprocessor scheduling and mapping strategy with added fault tolerant capability will enable to develop efficient Multiprocessor systems which meet future performance goal requirements. This is the substance of this work

A Methodology to Support the Maintenance of Object -Oriented Systems Using Impact Analysis.

Object-Oriented (OO) systems are difficult to understand due to the complex nature of the relationships that object-orientation supports. Inheritance, polymorphism, encapsulation, information hiding, aggregation, and association combine to make maintenance of OO systems difficult. Due to the presence of these characteristics in OO systems, maintenance activities on OO systems often have unexpected or unseen effects on the system. These effects can ripple through system components, complicating maintenance and testing of the system. The ability to trace the effects of maintenance provides the maintainer with knowledge that assists in debugging and testing modified and affected components. In this research, we show that the architecture of an OO system provides an effective framework for determining the impact of system changes. We developed the Comparative Software Maintenance (CSM) methodology to support the maintenance of OO systems. Through this methodology, we model relationships and structures, analyze the models to determine components that change as a result of maintenance, and perform impact analysis to determine components that are candidates for re-testing as a result of maintenance activity. The methodology includes a new data model, called Extended Low-Level Software Architecture (ELLSA), that facilitates impact analysis. CSM locates potential side effects, ripple effects, and other effects of maintenance on class structures, methods, and objects. The comprehensive architecture model enables CSM to perform either predictive, pre-modification impact analysis or post-modification impact analysis. The improved impact analysis process found in the methodology determines impact of changes to the component level. We apply the results of impact analysis to determine component level testing requirements. CSM enhances program understanding through the use of ELLSA. It also provides assistance for capturing complex dependencies found in object-oriented code. The methodology is implemented in JFlex. The automation provided by JFlex makes the application of CSM feasible

Progressing problems from requirements to specifications in problem frames

One of the problems with current practice in software development is that often customer requirements are not well captured, understood and analysed, and there is no clear traceable path from customer requirements to software specifications. This often leads to a mismatch between what the customer needs and what the software developer understands the customer needs. In addition to capturing, understanding and analysing requirements, requirements engineering (RE) aims to provide methods to allow software development practitioners to derive software specifications from requirements. Although work exists towards this aim, the systematic derivation of specifications from requirements is still an open problem. This thesis provides practical techniques to implement the idea of problem progression as the basis for transforming requirements into specifications. The techniques allow us to progress a software problem towards identifying its solution by carefully investigating the problem context and re-expressing the requirement statement until a specification is reached. We develop two classes of progression techniques, one formal, based on Hoare’s Communicating Sequential Processes (CSP), and one semi-formal, based on a notion of causality between events. The case studies in this thesis provide some validation for the techniques we have developed