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121.
Kim Khoa Nguyen Mohamed Cheriet Mathieu Lemay Victor Reijs Andrew Mackarel Alin Pastrama 《Computer Networks》2012,56(10):2538-2550
Cloud computing services have recently become a ubiquitous service delivery model, covering a wide range of applications from personal file sharing to being an enterprise data warehouse. Building green data center networks providing cloud computing services is an emerging trend in the Information and Communication Technology (ICT) industry, because of Global Warming and the potential GHG emissions resulting from cloud services. As one of the first worldwide initiatives provisioning ICT services entirely based on renewable energy such as solar, wind and hydroelectricity across Canada and around the world, the GreenStar Network (GSN) was developed to dynamically transport user services to be processed in data centers built in proximity to green energy sources, reducing Greenhouse Gas (GHG) emissions of ICT equipments. Regarding the current approach, which focuses mainly in reducing energy consumption at the micro-level through energy efficiency improvements, the overall energy consumption will eventually increase due to the growing demand from new services and users, resulting in an increase in GHG emissions. Based on the cooperation between Mantychore FP7 and the GSN, our approach is, therefore, much broader and more appropriate because it focuses on GHG emission reductions at the macro-level. This article presents some outcomes of our implementation of such a network model, which spans multiple green nodes in Canada, Europe and the USA. The network provides cloud computing services based on dynamic provision of network slices through relocation of virtual data centers. 相似文献
122.
Garbage collection can be done in vector mode on supercomputers like the CRAY-2 and the Cyber 205. Both copying collection and mark-and-sweep can be expressed as breadth-first searches in which the queue can be processed in parallel. We have designed a copying garbage collector whose inner loop works entirely in vector mode. We give performance measurements of the algorithm as implemented for Lisp CONS cells on the Cyber 205. Vector-mode garbage collection performs up to nine times faster than scalar-mode collection-a worthwhile improvement.Supported in part by NSF Grants DCR-8603543 and CCR-8806121, and by a Digital Equipment Corp. Faculty Incentive Grant.Supported by the NSF Research Experiences for Undergraduates program. 相似文献
123.
LetR be a unidirectional asynchronous ring ofn identical processors each with a single input bit. Letf be any cyclic nonconstant function ofn boolean variables. Moran and Warmuth (1986) prove that anydeterministic algorithm that evaluatesf onR has communication complexity (n logn) bits. They also construct a family of cyclic nonconstant boolean functions that can be evaluated inO(n logn) bits by a deterministic algorithm.This contrasts with the following new results:
相似文献
1. | There exists a family of cyclic nonconstant boolean functions which can be evaluated with expected complexity bits by arandomized algorithm forR. |
2. | Anynondeterministic algorithm forR which evaluates any cyclic nonconstant function has communication complexity bits. |
124.
125.
Measurements are reported of the dielectric properties of two semiconducting glasses of composition SiO2 · Na2O with admixtures of Sb2O
5 and SnO2, covering a wide range of temperatures and a range of six decades of frequency 10–2 to 104 Hz. Both glasses show a gradual evolution of growing low frequency dispersion (LFD) with increasing temperature, with both the real and imaginary components of the complex susceptibility following a power law of the type
n–1, with n 1 at the lowest frequencies. There are also clear indications of reversible phase transitions taking place which manifest themselves by changes in the spectral shape of the dielectric response. 相似文献
126.
Several related algorithms are presented for computing logarithms in fieldsGF(p),p a prime. Heuristic arguments predict a running time of exp((1+o(1))
) for the initial precomputation phase that is needed for eachp, and much shorter running times for computing individual logarithms once the precomputation is done. The running time of the precomputation is roughly the same as that of the fastest known algorithms for factoring integers of size aboutp. The algorithms use the well known basic scheme of obtaining linear equations for logarithms of small primes and then solving them to obtain a database to be used for the computation of individual logarithms. The novel ingredients are new ways of obtaining linear equations and new methods of solving these linear equations by adaptations of sparse matrix methods from numerical analysis to the case of finite rings. While some of the new logarithm algorithms are adaptations of known integer factorization algorithms, others are new and can be adapted to yield integer factorization algorithms. 相似文献
127.
综合电焊机行业的开发、生产、维修等情况,可以得出我国直流手弧焊电源目前总的发展趋势是:旋转弧焊发电机的生产正在不断缩小,而晶闸管弧焊整流器的生产正在大幅度的增加。本文通过分析旋转弧焊发电机及晶闸管弧焊整流器的发展情况,认为从节能节材、提高我国电焊机行业技术水平等多种因素出发,我们应进一步努力,强化政策措施,在国内晶闸管弧焊整流器十余年研制和推广的基础上,在“八五”期间完成用ZX5系列晶闸管弧焊整流器全面替代落后的AX系列旋转弧焊发电机这一历史重任。 相似文献
128.
129.
<正> 在炼钢过程中,炉气中水汽是钢液中含氢的主要来源。就平炉而言,除了空气湿度和炼钢原材料带入炉中的水分以外,还有煤气燃烧生成的水汽。根据过去的研究结果,由于空气湿度直接或间接引起的水汽分压,一般波动于0.01—0.08个大气压之间,而煤气燃烧废气中的水汽分压则经常在0.1个大气压以上,有时甚至可以超过0.2 相似文献
130.
研究了具有一定韧度的高强度结构钢裂纹早期扩展阻力与材料的微观组织结构、应力状态、变形历史和应变特性之间的关系。结果表明:裂纹扩展阻力(指J_R阻力曲线中的J_i和dJ/da)主要决定于裂纹尖端的塑性约束程度和应力应变场中消耗的弹性能和塑性功。这与三轴应力状态函数σ_mσ~(1/2)有关。材料的流变曲线描述了形变过程中的变形历史和应变特性,有明显的阶段性,其中第Ⅱ阶段的变形历史和应变特性制约着裂纹的启裂过程,第Ⅲ阶段的变形历史和应变特性制约着裂纹的扩展过程。应变硬化率dσ/dε可以敏感地反映出材料内部的应力分布和微观断裂机制。 相似文献