427 research outputs found

    On the complex stellar populations of ancient stellar systems

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    Het bestuderen van oeroude sterren in hedendaagse, nabije sterrenstelsels om hun geschiedenis te reconstrueren valt onder de noemer van stellaire archeologie. In de afgelopen jaren hebben nauwkeurige observaties onthuld dat veel oude sterrensystemen in de buurt van de Melkweg complexer zijn dan daarvoor was aangenomen. Deze complexiteiten vormen een uitdaging voor de formatiescenario’s van sterpopulaties in het jonge Universum. In mijn PhD proefschrift presenteer ik werk dat is gericht om nauwkeuriger de eigenschappen van sterpopulaties te karakteriseren in nabije stersystemen. Het meeste van mijn werk is gefocust op de afleiding van de snelheid waarmee sterrenstelsels nieuwe sterren vormen in hun levenscyclus. Dit geheel heet sterformatie geschiedenis en kan worden afgeleid uit het meten van de eigenschappen van de, zwakke en moeilijk te observeren, waterstof-brandende sterren in sterrenstelsels. Ik onderzoek het gebruik van de veel helderdere helium-brandende sterren om de meting van de sterformatie geschiedenis te verfijnen, en om een gedetailleerder beeld over het ontstaan van sterrenstelsels in oude tijdperken te geven. Ik bestudeer ook M13, een oude stercluster in ons eigen sterrenstelsel, door data te gebruiken van een kleine telescoop op de grond om chemische inhomogeniteiten te traceren in verschillende regio van de cluster. De werktuigen die ik heb ontwikkeld en gevalideerd in dit proefschrift zullen toelaten om onze studie van oude sterpopulaties uit te breiden naar een veel groter aantal van stersystemen en zodoende onze kennis over sterformatie in vroege tijdperken te verfijnen

    Software-Based Self-Test of Set-Associative Cache Memories

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    Embedded microprocessor cache memories suffer from limited observability and controllability creating problems during in-system tests. This paper presents a procedure to transform traditional march tests into software-based self-test programs for set-associative cache memories with LRU replacement. Among all the different cache blocks in a microprocessor, testing instruction caches represents a major challenge due to limitations in two areas: 1) test patterns which must be composed of valid instruction opcodes and 2) test result observability: the results can only be observed through the results of executed instructions. For these reasons, the proposed methodology will concentrate on the implementation of test programs for instruction caches. The main contribution of this work lies in the possibility of applying state-of-the-art memory test algorithms to embedded cache memories without introducing any hardware or performance overheads and guaranteeing the detection of typical faults arising in nanometer CMOS technologie

    Influence of parasitic capacitance variations on 65 nm and 32 nm predictive technology model SRAM core-cells

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    The continuous improving of CMOS technology allows the realization of digital circuits and in particular static random access memories that, compared with previous technologies, contain an impressive number of transistors. The use of new production processes introduces a set of parasitic effects that gain more and more importance with the scaling down of the technology. In particular, even small variations of parasitic capacitances in CMOS devices are expected to become an additional source of faulty behaviors in future technologies. This paper analyzes and compares the effect of parasitic capacitance variations in a SRAM memory circuit realized with 65 nm and 32 nm predictive technology model

    ReDO: Cross-Layer Multi-Objective Design-Exploration Framework for Efficient Soft Error Resilient Systems

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    Designing soft errors resilient systems is a complex engineering task, which nowadays follows a cross-layer approach. It requires a careful planning for different fault-tolerance mechanisms at different system's layers: starting from the technology up to the software domain. While these design decisions have a positive effect on the reliability of the system, they usually have a detrimental effect on its size, power consumption, performance and cost. Design space exploration for cross-layer reliability is therefore a multi-objective search problem in which reliability must be traded-off with other design dimensions. This paper proposes a cross-layer multi-objective design space exploration algorithm developed to help designers when building soft error resilient electronic systems. The algorithm exploits a system-level Bayesian reliability estimation model to analyze the effect of different cross-layer combinations of protection mechanisms on the reliability of the full system. A new heuristic based on the extremal optimization theory is used to efficiently explore the design space. An extended set of simulations shows the capability of this framework when applied both to benchmark applications and realistic systems, providing optimized systems that outperform those obtained by applying state-of-the-art cross-layer reliability techniques

    GPU acceleration for statistical gene classification

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    The use of Bioinformatic tools in routine clinical diagnostics is still facing a number of issues. The more complex and advanced bioinformatic tools become, the more performance is required by the computing platforms. Unfortunately, the cost of parallel computing platforms is usually prohibitive for both public and small private medical practices. This paper presents a successful experience in using the parallel processing capabilities of Graphical Processing Units (GPU) to speed up bioinformatic tasks such as statistical classification of gene expression profiles. The results show that using open source CUDA programming libraries allows to obtain a significant increase in performances and therefore to shorten the gap between advanced bioinformatic tools and real medical practic

    Gene Expression vs. Network Attractors

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    Microarrays, RNA-Seq, and Gene Regulatory Networks (GRNs) are common tools used to study the regulatory mechanisms mediating the expression of the genes involved in the biological processes of a cell. Whereas microarrays and RNA-Seq provide a snapshot of the average expression of a set of genes of a population of cells, GRNs are used to model the dynamics of the regulatory dependencies among a subset of genes believed to be the main actors in a biological process. In this paper we discuss the possibility of correlating a GRN dynamics with a gene expression profile extracted from one or more wet-lab expression experiments. This is more a position paper to promote discussion than a research paper with final results

    Using ER Models for Microprocessor Functional Test Coverage Evaluation

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    Test coverage evaluation is one of the most critical issues in microprocessor software-based testing. Whenever the test is developed in the absence of a structural model of the microprocessor, the evaluation of the final test coverage may become a major issue. In this paper, we present a microprocessor modeling technique based on entity-relationship diagrams allowing the definition and the computation of custom coverage functions. The proposed model is very flexible and particularly effective when a structural model of the microprocessor is not availabl

    A Systematic Approach for Evaluating Satellite Communications Systems

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    The aerospace environment imposes straight opera- tive conditions so every electronic system usually needs to be validated for these. The same way, communica- tion systems need to be evaluated before their intro- duction in aerospace applications. In the paper we present a new methodology for the evaluation of com- munication systems in space applications. The meth- odology aims, by abstraction, at identifying all the critical aspects for the evaluation and at defining a standard and reusable framework in order to be appli- cable to any Communication Systems. The methodol- ogy has been applied for the evaluation of three Data Bus for satellite communications: 1553, 1-Wire and Profibus DP RS 485 based systems have been analyzed and evaluate

    GPU cards as a low cost solution for efficient and fast classification of high dimensional gene expression datasets

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    The days when bioinformatics tools will be so reliable to become a standard aid in routine clinical diagnostics are getting very close. However, it is important to remember that the more complex and advanced bioinformatics tools become, the more performances are required by the computing platforms. Unfortunately, the cost of High Performance Computing (HPC) platforms is still prohibitive for both public and private medical practices. Therefore, to promote and facilitate the use of bioinformatics tools it is important to identify low-cost parallel computing solutions. This paper presents a successful experience in using the parallel processing capabilities of Graphical Processing Units (GPU) to speed up classification of gene expression profiles. Results show that using open source CUDA programming libraries allows to obtain a significant increase in performances and therefore to shorten the gap between advanced bioinformatics tools and real medical practic

    On the complex stellar populations of ancient stellar systems

    Get PDF
    Het bestuderen van oeroude sterren in hedendaagse, nabije sterrenstelsels om hun geschiedenis te reconstrueren valt onder de noemer van stellaire archeologie. In de afgelopen jaren hebben nauwkeurige observaties onthuld dat veel oude sterrensystemen in de buurt van de Melkweg complexer zijn dan daarvoor was aangenomen. Deze complexiteiten vormen een uitdaging voor de formatiescenario’s van sterpopulaties in het jonge Universum. In mijn PhD proefschrift presenteer ik werk dat is gericht om nauwkeuriger de eigenschappen van sterpopulaties te karakteriseren in nabije stersystemen. Het meeste van mijn werk is gefocust op de afleiding van de snelheid waarmee sterrenstelsels nieuwe sterren vormen in hun levenscyclus. Dit geheel heet sterformatie geschiedenis en kan worden afgeleid uit het meten van de eigenschappen van de, zwakke en moeilijk te observeren, waterstof-brandende sterren in sterrenstelsels. Ik onderzoek het gebruik van de veel helderdere helium-brandende sterren om de meting van de sterformatie geschiedenis te verfijnen, en om een gedetailleerder beeld over het ontstaan van sterrenstelsels in oude tijdperken te geven. Ik bestudeer ook M13, een oude stercluster in ons eigen sterrenstelsel, door data te gebruiken van een kleine telescoop op de grond om chemische inhomogeniteiten te traceren in verschillende regio van de cluster. De werktuigen die ik heb ontwikkeld en gevalideerd in dit proefschrift zullen toelaten om onze studie van oude sterpopulaties uit te breiden naar een veel groter aantal van stersystemen en zodoende onze kennis over sterformatie in vroege tijdperken te verfijnen
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