基于多维度开展4Ｇ无线网络投资效益评估的探讨

本文结合4G网络建设的实际情况,简要介绍了4G基站投资效益评估的方法,并从多个维度分析了基站建设的百元固定资产收入情况,用于指导后续4G网络建设,实现精准建网,提高投资效益。此外,本文讨论的方法对于运营商开展4G网络的规划和优化也有重要的参考意义。     

Nanoconfined (Bio)Catalysts as Efficient Glucose‐Responsive Nanoreactors

Herein, the design, synthesis, and characterization of bifunctional hybrid nanoreactors used for concurrent one‐pot chemoenzymatic reactions are shown. In the design, the enzyme, glucose oxidase, is wrapped with a peroxidase‐mimetic catalytic polymer. Hemin, the organic catalyst, is linked to the flexible polymeric scaffold through coordination to the imidazole groups that hang out the network. This spatial arrangement, which works as a metabolic channel, is optimized for cooperative chemoenzymatic reactions in which the enzyme catalyzes first. A deep characterization of the integrated nanoreactors demonstrates that the confinement of two distinct catalytic sites in the nanospace is very effective in one‐pot reactions. Moreover, besides its role as scaffold material, the polymeric mantel protects both the biocatalyst and the chemical catalyst from degradation and inactivation in the presence of organic solvents. Furthermore, the polymeric environment of the nanoreactors can be tailored in order to trigger the assembly of those into highly active heterogeneous hybrid catalysts. Finally, the new nanoreactors are applied to the efficient degradation of organic aromatic compounds using glucose as the only fuel.     

Analysis and enhancement of multi‐channel MAC protocol for ad hoc networks

In this paper, an analytical model is proposed to calculate the network throughput of dedicated control channel protocols that are designed to schedule multiple packets to be transmitted on different data channels simultaneously. Based on the analytical model, a scheme by tuning the initial contention window size is proposed to maximize the network throughput. We also present a novel multi‐channel MAC protocol for single‐hop scenario. Simulation results show that the proposed model is capable of modeling the behaviors of dedicated control channel protocols accurately. Furthermore, the proposed scheme can reduce the cost of collisions and enhance the network throughput up to 22% for 1 kB packet size and 80 nodes. Compared with other dedicated control channel protocols, the proposed protocol can schedule more control packets and use multiple channels more efficiently. Copyright © 2010 John Wiley & Sons, Ltd.     

简并多光子过程中两能级原子的动力学性质

两能级原子置于外部环境（热库）时,研究两能级原子与热辐射场的多光子相互作用,分析原子的动力学性质,求出多光子过程中原子约化密度算符非对角元。如果将两级级原子视为量子计算中的量子位,原子约化密度算符非对角元的时间演化能反映量子位消相干规律。     

机载雷达试飞中的多传感器融合技术

在机载雷达的试飞中 ,如何对雷达操作进行正确的引导会直接影响试飞的效果 ,本文提出了利用机上惯导、GPS、微波测距机等多种传感器融合技术 ,较好地解决了机载雷达科研试飞中对作用距离的评估、雷达操作的引导和显示等关键问题 ,取得了良好效果     

Exclusive or Sum of Complex Terms expressions minimization

This paper demonstrates both theoretically, through theorem proofs, and experimentally, that existing minimization algorithms for ESOP (Exclusive or Sum Of Products) expressions can be successfully used for minimizing ESCT (Exclusive or Sum of Complex Terms) expressions as well. ESCT expressions are more general than ESOP ones and being reversible are very useful for logic design and for quantum circuits. The field of ESOP minimization has received considerable attention along the years and a great number of research works can be found in the literature, in contrast to the ESCT minimization problem with much fewer works addressing it. The open problems of finding exact ESCT expressions for completely specified functions of more than six variables as well as the problem of finding exact ESCT expressions for incompletely specified functions are solved here based on ESOP principles, for the first time.     

Combined code reuse scheme with two‐dimensional OVSF codes assignment algorithm for uplink multi‐user/multi‐rate block spread multi‐cellular CDMA

The two‐dimensional (2D) block spread code division multiple access (CDMA) can avoid the uplink multiple‐access interference with low‐complexity single‐user detection in a slow fading channel and, therefore, is very attractive. In the 2D spreading, orthogonal variable spreading factor (OVSF) is used for spreading; an important problem is how to efficiently assign the limited resource of OVSF codes to users with different data rates, while meeting the requirement of quality of service in a multi‐cell environment. In this paper, it is shown that the code reuse can improve the code reuse efficiency and the proposed code reuse scheme combined with code assignment algorithm can allow flexible multi‐rate uplink transmission. The computer simulation confirms that the proposed code assignment algorithm improves the code reuse efficiency while achieving lower blocking probability than traditional CDMA. Copyright © 2012 John Wiley & Sons, Ltd.     

Porous waveguide facilitated low divergence quantum cascade laser

A quantum cascade laser with a porous waveguide structure emitting at 4.5μm is reported.A branchlike porous structure filled with metal material was fabricated on both sides of the laser ridge by an electrochemical etching process.In contrast to the common ridge waveguide laser,devices with a porous structure give rather better beam quality.Utilizing this porous structure as a high-order mode absorber,the device exhibited fundamental transverse mode emission with a nearly diffraction limited far-field beam divergence angle of 4.9°.     

Cryptanalysis of Hsiang‐Shih's authentication scheme for multi‐server architecture

From user point of view, password‐based remote user authentication technique is one of the most convenient and easy‐to‐use mechanisms to provide necessary security on system access. As the number of computer crimes in modern cyberspace has increased dramatically, the robustness of password‐based authentication schemes has been investigated by industries and organizations in recent years. In this paper, a well‐designed password‐based authentication protocol for multi‐server communication environment, introduced by Hsiang and Shih, is evaluated. Our security analysis indicates that their scheme is insecure against session key disclosure, server spoofing attack, and replay attack and behavior denial. Copyright © 2010 John Wiley & Sons, Ltd.     

智能天线系统中上行多用户相干信号的分离与DOA估计方法研究

本文研究了平主道中的窨特征估计问题。提出了一种工于循环累量的多用户空间牲针该算法用于智能天线中的ＳＤＭＡ实现。该算法构造了循环累量域四,通过对空间特征循环矩阵的特征分解可以得到用户信号的空间特征估计。并以此为基础,设计了用于上行多波束成形的窨滤波器组实现了上行多用户信号的分离,利用空间滤波器的空间频率响应确定共信道多用户信号的ＤＯＡ《