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961.
962.
Y. Pan 《Optics & Laser Technology》1994,26(4)
Processor arrays with an optical bus are introduced for parallel computation in this paper. We use the order statistics problem as an example to demonstrate how to design efficient parallel algorithms on such systems. Besides proposing a new algorithm on the model, some basic data movement operations involved in the algorithm are discussed. We believe that these operations can be used to design other parallel algorithms on the same model. Time analysis indicates that order statistics can be done more efficiently on a linear array with a pipelined optical bus than with an electronic bus. The initial results are promising, and the author believes that optical buses may emerge as a powerful communication mechanism for connecting large parallel computer systems in the near future. 相似文献
963.
大气光通信中大气闪烁时间平滑效应研究 总被引:4,自引:1,他引:3
利用大气闪烁的时间平滑效应,增加光电探测器曝光时间是克服大气闪烁对大气光通信的瞄准、捕获、跟踪链路影响的有效途径之一.基于科尔莫戈罗夫谱,导出了弱湍流起伏区无限平面波和球面波的大气闪烁时间平滑因子的一般表达式,并且用几何光学近似得到了在大孔径和小孔径接收情况下的时间平滑因子近似表达式.在孔径远大于菲涅耳区尺度时,平面波和球面波的时间平滑因子的近似表达式与精确表达式的误差分别小于6%和3%.分析结果表明,孔径越小,时间平滑效应越显著,并且菲涅耳区尺度对时间平滑效应影响的程度也随着孔径的增加而减弱. 相似文献
964.
Experimental long-distance decoy-state quantum key distribution based on polarization encoding 总被引:1,自引:0,他引:1
Peng CZ Zhang J Yang D Gao WB Ma HX Yin H Zeng HP Yang T Wang XB Pan JW 《Physical review letters》2007,98(1):010505
We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 102 km. Further, we simplify the experimental setup and use only one detector to implement the one-way decoy-state QKD over 75 km, with the advantage to overcome the security loopholes due to the efficiency mismatch of detectors. Our experimental implementation can really offer the unconditionally secure final keys. We use 3 different intensities of 0, 0.2, and 0.6 for the light sources in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation. 相似文献
965.
Some new sixth-order compact finite difference schemes for Poisson/Helmholtz equations on rectangular domains in both two- and three-dimensions are
developed and analyzed. Different from a few sixth-order compact finite difference
schemes in the literature, the finite difference and weight coefficients of the new
methods have analytic simple expressions. One of the new ideas is to use a weighted
combination of the source term at staggered grid points which is important for grid
points near the boundary and avoids partial derivatives of the source term. Furthermore, the new compact schemes are exact for 2D and 3D Poisson equations if the
solution is a polynomial less than or equal to 6. The coefficient matrices of the new
schemes are $M$-matrices for Helmholtz equations with wave number $K≤0,$ which
guarantee the discrete maximum principle and lead to the convergence of the new
sixth-order compact schemes. Numerical examples in both 2D and 3D are presented
to verify the effectiveness of the proposed schemes. 相似文献
966.
967.
岩土类介质在承受荷载时,不仅产生弹塑性变形,还伴随着渗流和固结,是一个关于时间的动态过程。本文建立起处理该问题的参变量变分原理以及相应的有限元方法,这样将原问题化为求解带约束条件(本构状态方程)的二次规划问题.文中讨论了单元的选取形式及具体的实施过程,还给出了一个实例. 相似文献
968.
SOIL AGGREGATE AND ITS RESPONSE TO LAND MANAGEMENT PRACTICES 总被引:17,自引:0,他引:17
Chaofu Wei Ming Gao Jingan Shao Deti Xie Genxing Pan 《中国颗粒学报》2006,4(5):211-219
This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that cohere to each other more strongly than other surrounding particles. The mechanism of soil particle aggregation may be expressed by a hierarchical model, which is based upon the hypothesis that macroaggregates (〉250μm) are collections of smaller microaggregates (〈250μm) held together with organic binding agents. Primary particles form microaggregates and then macroaggregates. Carbon (C)-rich young plant residues form and stabilize macroaggregates, whereas old organic C is occluded in the microaggregates. The interaction of aggregate dynamics with soil organic carbon (SOC) is complex and embraces a range of spatial and temporal processes within macroaggregates and microaggregates. The nature and properties of aggregates are determined by the quantity and quality of coarse residues and humic compounds and by the degree of their interaction with soil particles. The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and land management practices. Land management practices, including tillage methods, residue management, amendments, and soil fertility management, enhance soil aggregation. However, there is still much uncertainty in the dynamics of organic matter in macroaggregation and microaggregation, and research is still needed to understand further the mechanisms of aggregate formation and its responses to human activities. 相似文献
969.
970.
ADAPTIVE MESHLESS METHOD BASED ON LOCAL FIT TECHNOLOGY 总被引:1,自引:0,他引:1
LouLuliang ZengPan 《Acta Mechanica Solida Sinica》2005,18(2):164-172
An h-adaptive meshless method is proposed in this paper. The error estimation is based on local fit technology, usually confined to Voronoi Cells. The error is achieved by comparison of the computational results with smoothed ones, which are projected with Taylor series. Voronoi Cells are introduced not only for integration of potential energy but also for guidance of refinement.New nodes are placed within those cells with high estimated error. At the end of the paper, two numerical examples with severe stress gradient are analyzed. Through adaptive analysis accurate results are obtained at critical subdomains, which validates the efficiency of the method. 相似文献