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51.
Heidelberger P. Nicol D.M. 《Parallel and Distributed Systems, IEEE Transactions on》1993,4(8):906-921
The authors describe parallel algorithms for simulating certain continuous time Markov chains, such as those arising in queueing network models of distributed computing systems or communications systems. The algorithms are based on the technique of uniformization. Two variations of a conservative parallel simulation algorithm are presented. In each algorithm, a relatively short presimulation is performed to identify those times, and only those times, at which the simulation algorithm requires processor pairs to synchronize. Speedup studies of the algorithms, performed on a 16-node Intel iPSC/2 hypercube, are presented and discussed 相似文献
52.
53.
FIPA — Towards a Standard for Software Agents 总被引:1,自引:0,他引:1
Software agent technology will have a significant impact on the shape of the global information society in the next millennium. This branch of systems engineering is rapidly becoming a viable and exploitable technology where BT is well placed as both a potential user and provider of agent-based services and products.The highly interactive nature of multi-agent systems points to the need for consensus on agent interfaces in order to support interoperability between different agent systems. The completion and adoption of such a standard is a prerequisite to the commercialisation and successful exploitation of agent technology.This paper describes FIPA (Foundation for Intelligent Physical Agents) and its organisation. It provides an overview and guide to the FIPA97 specification. It discusses how FIPA relates to other agent standards activities and concludes with FIPA's plans for 1998. 相似文献
54.
G.W. Chantry J.W. Fleming Elisabeth A. Nicol H.A. Willis M.E.A. Cudby F.J. Boerio 《Polymer》1974,15(2):69-73
The far infra-red spectrum of highly crystalline polytetrafluoroethylene has been shown to contain a new band near 33cm?1, the band at 55cm?1 has been shown to be a close doublet and two further bands at 291 and 308cm?1 have been observed. These results strongly support the conclusions of Boerio and Koenig from Raman observations that the unit cell contains at least two molecular segments. 相似文献
55.
N Kraus T McGee J Ferre JA Hoeppner T Carrell A Sharma T Nicol 《Canadian Metallurgical Quarterly》1993,14(4):223-234
The subject of this case report is an 18-year-old woman with grossly abnormal auditory brain stem response (ABR), normal peripheral hearing, and specific behavioral auditory processing deficits. Auditory middle latency responses (MLRs) and cortical potentials N1, P2, and P300 were intact. The mismatch negativity (MMN) was normal in response to certain synthesized speech stimuli and impaired to others--consistent with her behavioral discrimination of these stimuli. Behavioral tests of auditory processing were consistent with auditory brain stem dysfunction. A neuropsychological evaluation revealed normal intellectual and academic performance. The subject was in her first year of college at the time of the evaluation. This case study is important because: (1) Although there have been several reports of absent/abnormal ABR with preserved peripheral hearing and deficits in auditory processing, little is known about the specific nature of the auditory deficits experienced by these individuals. Such information may be valuable to the clinical management of patients with this constellation of findings. (2) Of interest is the information that the mismatch negativity (MMN) cortical event-related potential can bring to the evaluation of patients with auditory processing deficits. The MMN reflects central auditory processing of small acoustic differences and may provide an objective measure of auditory discrimination. (3) From a theorectical standpoint, a patient with neural deficits affecting specific components of the auditory pathway provides insight into the relationship between evoked potentials and physiological mechanisms of auditory processing. How do various components of the auditory pathway contribute to speech discrimination? How might evoked potentials reflect the processes underlying the neural coding of specific features of speech stimuli such as timing and spectral cues? 相似文献
56.
Steroid actions on the vascular wall have been thought to depend on direct, genomic mechanisms being characterized by a considerable delay and on secondary events, including changes of coagulation, plasma lipids, and renal electrolyte and volume regulation. Recently, rapid effects of steroids on the vascular wall have been reported being clearly incompatible with the classical theory of genomic steroid action. As these effects occur in classical target tissues for genomic steroid action, and modulation of intracellular signaling has been shown to influence genomic steroid action, a two-step model of steroid action was developed integrating both genomic and nongenomic aspects and their possible interaction. This review summarizes recent studies on both types of direct, vascular steroid actions, the swift and the sluggish ones, and discusses the role of these actions in regulation of circulatory homeostasis and their potential therapeutic implications. 相似文献
57.
58.
S. A. Allison L. A. Goold M. J. Nicol A. Granville 《Metallurgical and Materials Transactions B》1972,3(10):2613-2618
The surface reaction products formed when sulfide minerals react with xanthates were analyzed by spectrophotometric methods.
These products were found to be predominantly either metal xanthate or dixanthogen, depending on the particular sulfide mineral.
Dixanthogen is formed on those minerals that, in a solution of xanthate, assume a rest potential greater than the equilibrium
potential for the reduction of dixanthogen or xanthate. 相似文献
59.
von Ellenrieder N Muravchik CH Nehorai A 《IEEE transactions on bio-medical engineering》2005,52(7):1210-1217
We present a formulation for the magnetoencephalography (MEG) forward problem with a layered head model. Traditionally the magnetic field is computed based on the electric potential on the interfaces between the layers. We propose to express the effect of the volumetric currents in terms of an equivalent surface current density on each interface, and obtain the magnetic field based on them. The boundary elements method is used to compute the equivalent current density and the magnetic field for a realistic head geometry. We present numerical results showing that the MEG forward problem is solved correctly with this formulation, and compare it with the performance of the traditional formulation. We conclude that the traditional formulation generally performs better, but still the new formulation is useful in certain situations. 相似文献
60.
The examination of the 250–350 cm?1 region of the infra-red spectrum of polytetrafluoroethylene (PTFE) has been extended by studies of thermally degraded and sintered material. We conclude that a band at 277 cm?1 does not arise from a true mode of the crystal but has its origin in regions where the chain has a bent conformation. Our previous speculation that bands at 292 cm?1 and 3121 cm?1 (Raman active only, for the isolated chain) acquire their weak activity in the infra-red through conformational disorder is confirmed. It is likely that the conformational disorder in question arises from chain folding in the polymer crystal. 相似文献