Despite signiicant improvements in network interfaces and software messaging layers, software communication overhead still dominates the hardware routing cost in most parallel systems. In this study, we identify the sources of this overhead by relating user communication services to particular network hardware features. Based on a detailed analysis of the active messages layer on the CM-5, we a...

Local-area networks based on high-bandwidth packet-switching technology, such as ATM, show a tremendous promise in reducing communication latencies and overheads. However, the lack of ow-control and reliable delivery in ATM networks requires the higher protocol layers to deal with cell loss or corruption. While it is possible to use TCP-based communications over ATM, the protocol mismatch resul...

Seeing the many examples in the literature of causality violations based on faster-than-light (FTL) signals one naturally thinks that FTL motion leads inevitably to the possibility of time travel. We show that this logical inference is invalid by demonstrating a model, based on (3+1)-dimensional Minkowski spacetime, in which FTL motion is permitted (in every direction without any limitation on ...

In this paper we propose two languages, called Future Temporal Logic (FTL) and Past Temporal Logic (PTL), for specifying temporal triggers. Some examples of trigger conditions that can be speciied in our language are the following: \The value of a certain attribute increases by more than 10% in ten minutes", "A tuple that satisses a certain predicate is added to the database at least 10 minutes...

شرایط افروزش و اشتعال سوخت‌های گداخت هسته‌ای در حضور ناخالص­‌ها، یکی از موارد مهمی است که طراحی قرص‌های سوخت باید مورد توجه قرار گیرد. این مقاله اثر ناخالصی هسته سنگین طلا بر کلیه فرایندهای احتراق پلاسمای غیرتعادلی دوتریم- تریتیم مدل چهار دمایی آن شکل تابع توزیع انرژی رفتار فوتون‌ها تأثیر می‌گذارد بررسی گرفته است. مطالعه شامل اثرات منفی سوخت، طول زمان تشکیل لکه داغ نتایج محاسبات عددی به­ دست آم...