104 research outputs found

    Balancing Power Consumption in Multiprocessor Systems

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    Actions usually taken to prevent processors from overheating, such as decreasing the frequency or stopping the execution flow, also degrade performance. Multiprocessor systems, however, offer the possibility of moving the task that caused a CPU to overheat away to some other, cooler CPU, so throttling becomes only a last resort taken if all of a system\u27s processors are hot. Additionally, the scheduler can take advantage of the energy characteristics of individual tasks, and distribute hot tasks as well as cool tasks evenly among all CPUs. This work presents a mechanism for determining the energy characteristics of tasks by means of event monitoring counters, and an energy-aware scheduling policy that strives to assign tasks to CPUs in a way that avoids overheating individual CPUs. Our evaluations show that the benefit of avoiding throttling outweighs the overhead of additional task migrations, and that energy-aware scheduling in many cases increases the system\u27s throughput

    Structural heterogeneities in starch hydrogels

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    Hydrogels have a complex, heterogeneous structure and organisation, making them promising candidates for advanced structural and cosmetics applications. Starch is an attractive material for producing hydrogels due to its low cost and biocompatibility, but the structural dynamics of polymer chains within starch hydrogels are not well understood, limiting their development and utilisation. We employed a range of NMR methodologies (CPSP/MAS, HR-MAS, HPDEC and WPT-CP) to probe the molecular mobility and water dynamics within starch hydrogels featuring a wide range of physical properties. The insights from these methods were related to bulk rheological, thermal (DSC) and crystalline (PXRD) properties. We have reported for the first time the presence of highly dynamic starch chains, behaving as solvated moieties existing in the liquid component of hydrogel systems. We have correlated the chains’ degree of structural mobility with macroscopic properties of the bulk systems, providing new insights into the structure-function relationships governing hydrogel assemblies

    Operating system support for simultaneous multithreaded processors

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    Simultaneous multithreaded (SMT) processors are able to execute multiple application threads in parallel in order to improve the utilisation of the processor’s execution resources. The improved utilisation provides a higher processor-wide throughput at the expense of the performance of each individual thread. Simultaneous multithreading has recently been incorporated into the Intel Pentium 4 processor family as “Hyper-Threading”. While there is already basic support for it in popular operating systems, that support does not take advantage of any knowledge about the characteristics of SMT, and therefore does not fully exploit the processor. SMT presents a number of challenges to operating system designers. The threads ’ dynamic sharing of processor resources means that there are complex performance interactions between threads. These interactions are often unknown, poorly understood, or hard to avoid. As a result such interactions tend to be ignored leading to a lower processor throughput. In this dissertation I start by describing simultaneous multithreading and the hardware implementations of it. I discuss areas of operating system support that are either necessary or desirable. I present a detailed study of a real SMT processor, the Intel Hyper-Threaded Pentium 4, an

    Phosphonodithioformiates et derives: etude de leur reactivite; applications synthetiques et biologiques

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    SIGLEINIST T 76588 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
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