Software Transactional Memory is a concurrency control technique gaining increasing popularity, as it provides high-level concurrency control constructs and eases the development of highly multi-threaded applications. But this easiness comes at the expense of restricting the operations that can be executed within a memory transaction, and operations such as terminal and file I/O are either not allowed or incur in serious performance penalties. Database I/O is another example of operations that usually are not allowed within a memory transaction. This paper proposes to combine memory and database transactions in a single unified model, benefiting from the ACID properties of the database transactions and from the speed of main memory data processing. The new unified model covers, without differentiating, both memory and database operations. Thus, the users are allowed to freely intertwine memory and database accesses within the same transaction, knowing that the memory and database contents will always remain consistent and that the transaction will atomically abort or commit the operations in both memory and database. This approach allows to increase the granularity of the in-memory atomic actions and hence, simplifies the reasoning about them.

Transactional memory is a new trend in concurrency control that was boosted by the advent of multi-core processors and the near to come many-core processors. It promises the performance of finer grain with the simplicity of coarse grain threading. However, there is a clear absence of software development tools oriented to the transactional memory programming model, which is confirmed by the very small number of related scientific works published until now. This paper describes ongoing work. We propose a very low overhead monitoring framework, developed specifically for monitoring TM computations, that collects the transactional events into a single log file, sorted in a global order. This framework is then used by a visualization tool to display different types of charts from two categories: statistical charts and thread-time space diagrams. These last diagrams are interactive, allowing to identify conflicting transactions. We use the visualization tool to analyse the behavior of two different, but similar, testing applications, illustrating how it can be used to better understand the behavior of these transactional memory applications.

Software Transactional Memory is a concurrency control technique gaining increasing popularity, as it provides high-level concurrency control constructs and eases the development of highly multi-threaded applications. But this easiness comes at the expense of restricting the operations that can be executed within a memory transaction, and operations such as terminal and file I/O are either not allowed or incur in serious performance penalties. Database I/O is another example of operations that usually are not allowed within a memory transaction. This paper proposes to combine memory and database transactions in a single unified model, benefiting from the ACID properties of the database transactions and from the speed of main memory data processing. The new unified model covers, without differentiating, both memory and database operations. Thus, the users are allowed to freely intertwine memory and database accesses within the same transaction, knowing that the memory and database contents will always remain consistent and that the transaction will atomically abort or commit the operations in both memory and database. This approach allows to increase the granularity of the in-memory atomic actions and hence, simplifies the reasoning about them.

In this paper a discrete-variable optimization methodology for the automatic design of CMOS integrated spiral inductors is introduced. The use of discrete variable optimization procedure offers the designer the possibility for exploring the design space exclusively in those points available for the technology under use. Further user-defined constraints between layout parameters may also be incorporated as a way of taking into account design heuristics. A comparison between using discrete-variable optimization and a continuous optimization procedure followed by a discretization of the results is presented, where the benefits of the proposed methodology are presented. An application using the proposed methodology was developed in Matlab and the optimization toolbox is used. For the sake of simplicity the pi-model has been used for characterizing the inductor. The validity of the design results is checked against circuit simulation with ASITIC.

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As organizações são concebidas com o enfoque principal na eficiência. As práticas de gestão que adoptam pressupõem, regra geral, a estabilidade do ambiente onde estão inseridas. Por isso, as organizações ficam vulneráveis aos distúrbios a que são sujeitas, e cuja frequência é cada vez maior, o que condiciona a sua eficiência, o seu nível de produtividade e, consequentemente, a sua competitividade. Porque existe uma relação de interdependência mais ou menos definida entre as organizações, a ocorrência de um distúrbio numa delas pode afectar todas as que dela dependem. É, por isso, fundamental que as organizações sejam mais resilientes, isto é, sejam capazes de reagir a um distúrbio inesperado, regressando rapidamente ao estado original ou a um melhor, após a cessação do distúrbio. Neste sentido, uma das acções que pode ser tomada é a definição de planos de mitigação e/ou de contingência. A adequação de planos, de mitigação e/ou de contingência, a implementar quando uma organização está perante um distúrbio, sendo por natureza uma actividade pró-activa, pressupõe a identificação dos distúrbios a que a organização pode ficar sujeita. Atendendo a que os distúrbios podem ter características muito diferentes, no que concerne à frequência de ocorrência, efeito crítico, nível de previsibilidade, área afectada na organização e duração, e podem, ainda, ter origem em fontes diversas, internas ou externas à organização produzidas pelo Homem ou pela Natureza, é fundamental que existam modelos que permitam a sua caracterização e a quantificação do grau de severidade das suas consequências para a organização onde incidem. É possível identificar na bibliografia modelos cujo desenvolvimento está associado aos distúrbios. Contudo, o âmbito em que são desenvolvidos é muito diverso. Nenhum deles, porém, permite caracterizar os distúrbios. O principal objectivo deste artigo é apresentar um modelo conceptual que permita caracterizar os distúrbios e avaliar a severidade dos seus efeitos para a organização onde incidem.

This paper addresses an implementation of the upper bound limit analysis theorem using a parallel mixed finite element formulation. The intrinsic characteristics of the adopted upper bound formulation proved to be suitable to adapt it to an efficient parallelization scheme. In order to illustrate the computational power provided by the new parallel processing method, accurate upper bound collapse load estimates, for 3D problems, are produced using a cluster of common PC machines.

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Complex impedance measurements were used to analyze the influence of ultraviolet and ozone gas on the electronic behaviour of ZnO films grown by rf magnetron sputtering. The data show that UV exposure strongly increases the ac conductivity of the film at very low frequencies, and that after ozone exposure it recovers the original value. At high frequencies, however, UV-light exposure it does not change the conductivity but the ozone acts in the sense to decrease it. Two distinct mechanisms, related to two relaxation time distributions are clearly observed: they are superimposed in the virgin sample, but they split forming two semicircles in the z″(f) - z′(f) diagrams when the samples are treated with UV and/or ozone gas. A combination of the bruggeman effective medium approximation (BEMA) with the random free energy barrier model is used to fit the data and to explain the ac conductivity variation phenomena observed. © 2006 Elsevier B.V. All rights reserved.

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