MISO系统中上下行链路对偶性研究

TDD系统中,利用上下行链路的对偶性可以将非凸的下行优化问题转换到上行链路,从而极大简化问题的分析和数值求解。上下行链路在波束成形和容量域两方面都存在对偶性。本文在统一的系统模型下,针对总功率约束和每天线功率约束两种情况,利用拉格朗日对偶法分别对波束成形对偶、容量域对偶做了推导、分析。此外,用凸优化软件包CVX简化了问题的建模。分析表明,上下行对偶等价于拉格朗日对偶,对偶问题可更一般地表示为极大极小问题。针对每天线功率约束下的波束成形问题,用迭代法和内点法分别对其进行了MATLAB仿真。仿真结果表明,非凸的下行优化问题可以利用对偶性转化为上行链路中的凸优化问题,从而得以解决。     

Using minimal cuts to optimize network reliability for a stochastic computer network subject to assignment budget

In our modern society, information and data are usually transmitted through a computer network. Since the computer network's reliability has a great impact on the quality of data transmission, many organizations devote to evaluating or improving network reliability, especially for network reliability optimization. This study focuses on such a confronted problem that is to find the optimal transmission line assignment to the computer network such that network reliability is maximized subject to the budget constraint. Each transmission line owns several states due to failure, maintenance, etc., and thus the computer network associated with any transmission line assignment is called a stochastic computer network. Network reliability is the probability that the computer network can transmit the specified units of data successfully. Because the discussed problem is NP-hard, an optimization algorithm that integrates the genetic algorithm, minimal cuts and Recursive Sum of Disjoint Products is proposed. Experimental results illustrate the solution procedure and show that the proposed algorithm can be executed in a reasonable time.     

Nanostructural ZnO based coplanar gas sensor arrays from the injection of metal chloride solutions: Device processing, gas-sensing properties and selectivity in liquors applications

A new coplanar gas sensor array of ZnO was fabricated by injecting different volumes of 0.01 mol/L AlCl₃, CuCl₂, SnCl₄, TiCl₄, PdCl₂ and WCl₆ solutions and post treatment to improve the selectivity in liquor. The new four-sensor array was optimized by maximizing Sum of Euclidean distances (SED) of the gases of liquor. The morphology of films was characterized by field-emission scanning electron microscopy (FESEM). The results showed that ZnO nanostructures were formed on the surface of films after the injecting process. Nanowires, 100 nm in diameter and 3 μm in length, were found when the solutions included AlCl₃, CuCl₂, SnCl₄ and PdCl₂. However, when the injecting solution was TiCl₄, nanotowers with 500 nm in diameter and 4 μm in length appeared. No new structures appeared when the WCl₆ solution was injected. The results of testing gases of liquor revealed that the injecting process could improve the response of the sensors array effectively. Through calculating the value of the SED, the best array was confirmed whose SED value would be three times the worst one.     

不交和公式及其在网络可靠度计算中的应用

提出了不交和公式及其在网络可靠度计算中的应用,和传统的算法相比,该算法操作简便,易于实现,计算复杂度小的点,从而适合于大型网络可靠度的计算。     

Polymer-Silane Interactions Probed by Sum Frequency Generation Vibrational Spectroscopy

Gaining an understanding of the molecular mechanisms of adhesion to polymeric materials is crucial for the design of better adhesives and adhesion promoters. Silane coupling agents are widely used as polymer-polymer adhesion promoters. However, a molecular level understanding of how silanes enhance adhesion between solid polymeric surfaces is largely unknown. Here we exploit the extreme surface sensitivity of sum frequency generation (SFG) vibrational spectroscopy to probe various interactions at buried interfaces between polymers and silanes in situ. It has been elucidated that silanes can adopt various conformations at the interfaces with different polymers depending on the chemical groups that comprise the silane and the surface-presenting groups on the polymer. Some silanes have been found to diffuse into certain polymers, and SFG has been used to monitor the moving polymer/silane interface and deduce the diffusion coefficient. Hydrogen bonding between polymer surface carbonyl groups and silane amino groups has also been detected. Finally we demonstrate that SFG can probe the buried interface between a polymer and a cured silicone elastomer, and the segregation of silane adhesion promoting molecules to the polymer/elastomer interface can be detected.     

关于网络的终端可靠度的新算法

类比Ｄｏｄｔｓｏｎ与Ｇｏｂｉｅｎ［１］提出的算法,给出网络的终端可靠度的一种新算法,提出了Ｒｓ－ｔ的选边原则,使得算法过程中产生的项在遇到含有道路或割集时,则停止生长,而继续其它的分支,不必枚举出所有道路或割集,使得Ｒｓ－ｔ的表达式中的项数和过程中产生的项数减少,表达式更加紧凑,运算更快。通过对计算结果的比较,可以看到本文算法对较大的网络有着很大意义。     

清梳加工过程对杂质数量的影响

借助于乌斯特纤维测试系统，对立达清梳系统和国产清梳系统的半制品杂质数量进行了试验。揭示了棉纺清梳加工过程中杂质数量的演变规律。证实在生产中立达清梳设备除杂分工与国产设备确有显著区别。发现粗梳纱的单纱强力与生条含杂粒数显著相关。讨论了C4型梳棉机锡林速度、刺辊速度、输出速度与生条含杂粒数的关系。指出立达精梳系统的Mono型轴流开棉机、Aerofeed型给棉机和国产系统的A092AST型棉箱给棉机对半制品杂质含量的影响进一步研究。     

公差分析中的统计公差方法综述

公差分析是公差设计中的重要问题,公差分析方法分为极值法和统计公差方法两类,其中大多数方法是以概率统计原理为基础的统计公差方法。本文介绍了常用的公差分析方法,包括极值法、方和根法、修正的方和根法、蒙特卡洛模拟法、田口试验法和卷积方法等,并对这些方法进行了比较,阐述了统计公差方法的适用性。     

只利用一种模拟加权的子阵级和差波束旁瓣抑制方法

对于采用单脉冲技术的子阵级相控阵雷达系统,需要同时对和、差波束的旁瓣进行抑制。该文研究阵元级只用一种模拟加权,同时结合子阵级数字加权的和、差波束旁瓣抑制方法。通过构造阵列的和、差输出通道,并对假想的位于和、差波束整个旁瓣区域内的干扰进行最优自适应滤波来确定模拟加权。为改善旁瓣抑制效果,子阵级进一步采用数字加权,以逼近常规的Taylor和Bayliss加权。该方法有效地降低了硬件成本与复杂性,并充分利用了数字处理的灵活性。本文纠正了有关文献中求解模拟加权表达式中的错误,并给出了正确形式。仿真结果证明了所提出方法的有效性。     

改进的基于统计学的滑动窗口无参数的累积和算法

为解决IEEE802.15.4无线传感器网络(WSN)中节点自私行为的检测问题,将最低检测延迟作为决策目标,提出了一种改进的基于统计学的滑动窗口无参数的累积和(SWN-CUSUM)算法。算法通过跟踪来自数据包两次成功传输之间的延迟特征序列,以此来判断无线传感器网络中的节点是否存在自私行为。最后通过NS2仿真工具验证算法的有效性。研究结果表明：改进的算法不仅弱化了阈值对算法性能的影响,还缩小了用于检测自私行为的滑动窗口大小,同时所提算法相对于原SWN-CUSUM算法在计算量及检测延迟上均有改善,证明改进的算法可以有效、快速地检测IEEE802.15.4无线传感器网络中的节点自私行为。