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121.
We present a technique to estimate the arrival rate from delay measurements, acquired using single-packet probing. With practical applications in mind, we investigate a lower bound on the value of probe separation, to obtain a satisfactory estimate in a fixed amount of time. This leads to a problem: how long does it take for an M/D/1 queue to converge to its steady state as a function of the load? We examine this problem using three independent approaches: the time until the autocovariance of the transient workload process becomes negligible; the time it takes for the first transient moment of the workload process to get close to its stationary limit; and the convergence rate of the transient workload distribution to stationarity. These approaches yield different, yet strikingly similar results. We conclude with a recommendation for the probe separation threshold, and a practical approach to obtaining an arrival rate estimate using single-packet probing. 相似文献
122.
This article was prompted by the thoughtful commentaries of Norton, Tzur, and Dreyfus. Their commentaries pointed out important ideas that were left implicit or only partially explained. The clarifications made here include how the Learning Through Activity (LTA) research program differs from related research programs, the relation of the LTA theoretical framework to scheme theory, our choice to not employ the construct of perturbation in explaining learning, and the structure of hypothetical learning trajectories. In addition, I discuss a type of mathematical concept that we have not discussed previously. 相似文献
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In an effort to achieve fast and effective tank segmentation of infrared images under complex background for the homing anti-tank missile, the threshold of the maximum between-class variance method (i.e., the Otsu method) is experimentally analyzed, and the working mechanism of the Otsu method is revealed. Subsequently, a fast and effective method for tank segmentation under complex background is proposed based on the Otsu method by constraining the image background pixels and gray levels. Firstly, with the prior information of the tank, derive the equation to calculate the number of pixels of tank according to optical imaging principle, and then use the calculated tank size to constrain the image background pixels. Secondly, employ the golden section to restrict the background gray levels. Finally, use the Otsu method to implement the segmentation of the tank. Experimental results demonstrate that the proposed method can get as an ideal result as the manual segmentation with less running time. 相似文献
125.
解高维热传导方程的一族高精度的显式差分格式 总被引:12,自引:0,他引:12
孙鸿烈 《高校应用数学学报(A辑)》1999,14(4):427-432
本文构造出针对三维和四维热传导方程的一族高精度的显格式,其截断误差阶达到O(τ^2+h^4),并给出了稳定性条件,通过数值实例,验证了此方法较周顺兴(1980年)的结果提高二位以上有效数字。 相似文献
126.
A. G. Soldatos K. G. Arvanitis E. C. Zacharenakis 《Archive of Applied Mechanics (Ingenieur Archiv)》2002,72(2-3):147-159
Summary Active control schemes are used for the protection of base-isolated and seismically excited buildings. The desired control
objective is to keep the whole structure arbitrarily close to its initial configuration prior to the earthquake. The proposed
methods require control force application only at the base of the structure. The controllers developed may depend on information
obtained from all the floors or just the first (base) floor alone.
Received 13 September 2000; accepted for publication 26 June 2001
RID="
ID=" Dedicated to the memory of Professor P.D. Panagiotopoulos with our warmest prayers.
RID="
ID=" The first author wishes to thank Prof. G. Leitmann and Prof. E. Papadopoulos for the numerous helpful discussions. The
same author is supported in part by the Institute of Communication and Computer Systems, NTUA, under the program Archimedes
65/1017. 相似文献
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128.
采用矢量场模型,对具有诱人应用前景的圆柱形垂直腔面发射半导体激光器(VCSEL)的模式阈值增益进行了数值模拟;为减弱金属圆柱的反射以使理论计算更接近实际,采用两种方案,将外加金属包壳视为非理想导体,或在此基础上,将金属包壳与激光器主体结构隔开. 从模式的阈值增益与顶Bragg反射镜层周期数的关系方面,与理想金属外包壳情况进行了比较. 结果表明,高阶贝塞耳函数模式的阈值增益变化规律基本相同,而0阶贝塞耳函数模式的阈值增益变化规律相差较大. 相似文献
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130.