Calculation of the Steady State Waiting Time Distribution in GI/PH/c and MAP/PH/c Queues

We consider the waiting time (delay) W in a FCFS c-server queue with arrivals which are either renewal or governed by Neuts' Markovian arrival process, and (possibly heterogeneous) service time distributions of general phase-type F _i , with m _i phases for the ith server. The distribution of W is then again phase-type, with m ₁m _c phases for the general heterogeneous renewal case and phases for the homogeneous case F _i =F, m _i =m. We derive the phase-type representation in a form which is explicit up to the solution of a matrix fixed point problem; the key new ingredient is a careful study of the not-all-busy period where some or all servers are idle. Numerical examples are presented as well.     

Drawing and extrusion of semi-crystalline polymers

This review treats mainly the initial transformation of the starting unoriented lamellar material into the final oriented microfibrillar structure and its drawing. If the starting material has partially oriented shish-kebab structure the drawing is a combination of transformation of lamellae into the microfibrils and the drawing of microfibrils. The review article is based on the literature from the last ten years and relys heavily on recent reviewing [1–3]. Older articles are only included if they have contributed to the basic ideas and experiments of drawing.     

双周期不等长刚性线Ⅲ型应力奇异因子的精确解

研究了含双周期刚性线夹杂复合材料的反平面剪切问题,其基本胞元含有四条不等长刚性线。运用复变函数方法,获得该问题严格的闭合解,得到了复合材料体内应力场的分布表达式,并在此基础上给出了刚性线尖端III型应力奇异因子的精确公式。数值算例显示了刚性线分布特征对材料细观应力场的影响,特别是短刚性线对主刚性线尖端应力场的屏蔽与放大作用。由本文解答的特殊情形,可以直接导出近年来其他学者获得的结果和一系列有意义的新结果。     

Quantitative analysis of periodic antiphase boundaries by lattice image simulations

Periodic antiphase boundaries in the intermetallic compound Cu₃Pd have been studied by high resolution electron microscopy and image simulation. The intensity profiles across the boundary were recorded and the thickness of the boundary compared to the values deduced from X-ray and neutron diffraction data. It is shown that electron microscopy always minimizes the thickness of the boundary. The possible factors for this discrepancy are analysed and discussed.     

Markov-modulated queueing systems

Markov-modulated queueing systems are those in which the primary arrival and service mechanisms are influenced by changes of phase in a secondary Markov process. This influence may be external or internal, and may represent factors such as changes in environment or service interruptions. An important example of such a model arises in packet switching, where the calls generating packets are identified as customers being served at an infinite server system. In this paper we first survey a number of different models for Markov-modulated queueing systems. We then analyze a model in which the workload process and the secondary process together constitute a Markov compound Poisson process. We derive the properties of the waiting time, idle time and busy period, using techniques based on infinitesimal generators. This model was first investigated by G.J.K. Regterschot and J.H.A. de Smit using Wiener-Hopf techniques, their primary interest being the queue-length and waiting time.     

用振动法测量气体的定熵指数

本文介绍了一种简单的利用简谐振动现象测量气体的定熵指数的方法。     

Ultra-low frequency passive vertical vibration isolation system

An ultra-low frequency passive vertical vibration isolator is constructed by mounting a couple of additional masses on the crank-arms of the torsion spring. The theoretical analysis and experimental results show that the system with additional masses can achieve better vertical vibration isolation and longer resonant period. Measured displacement response of the test mass under seismic excitation reaches 3 x 10^{-12 m/√ Hz} around 10 Hz, and the isolation ratio comes to about 60 dB attenuation at 6 Hz, which is about 30 dB lower than that of the system without additional masses. Project supported by the National Natural Science Foundation of China (Grant Nos. 19425008, 49674246 and 59678032).     

BL Lac天体S5 0716+714的光变周期特性研究

从大量文献资料中, 收集了BL Lac天体S5 0716+714光学B，V，R，I波段的有效观测数据点共16818个， 获得了从1994年至2006年的长期光变曲线，光变曲线表明S5 0716+714天体存在完整的非正弦变化并且它的活动非常剧烈. 用功率谱方法分析了S5 0716+714天体的光变周期, 结果表明S5 0716+714天体存在的长光变周期为1.1年，Raiteri等人发现的3.3年周期可能是1.1年周期的叠合. 预期在2007年2月应该为S5 0716+714天体的再次爆发期. 关键词： BL Lac天体S5 0716+714 光变周期 功率谱方法