EPON_EOC统一网管拓扑发现功能的设计和实现

针对目前大部分以太网无源光网络(EPON)与以太数据通过同轴电缆传输(EOC)设备都是使用相对独立的网管方式,在研究EPON_EOC系统结构与特点的基础上,提出了一种可以实现EPON和EOC设备统一管理的方案,并进行了EPON与EOC设备的拓扑发现功能的设计与系统实现.实际测试结果表明,该方案能较好地实现EPON_EO...     

SGDBR型激光器的波长自动控制系统

根据取样光栅分布布拉格反射器(SGDBR)型激光器的波长调谐原理,设计出用于SGDBR型激光器的波长自动控制系统.利用该系统对自行研制的SGDBR型激光器进行了准确、快速的波长扫描,为器件的动态性能研究奠定了测试基础.     

激光诱导银纳米颗粒薄膜和微结构

利用可见激光诱导化学沉积方法在玻璃基底上制备纳米银薄膜和微结构。玻璃样品池中装满柠檬酸钠和硝酸银的混合透明溶液,当一束可见连续激光正入射样品池一段时间后,在辐照区域的玻璃内壁上便可以形成一层光亮的银膜。银膜沉积的速度受到激光功率密度、激光波长、辐照时间以及混合溶液的浓度等条件的影响。利用X射线衍射、原子力显微镜和拉曼光谱仪等手段对制备的薄膜的成分、表面形貌和拉曼活性等性质进行了表征和分析。利用此方法制备的银膜具有良好的表面增强拉曼散射活性。同时,利用双光束干涉的方法在玻璃基底上诱导出不同周期的银纳米颗粒光栅。     

一种抗频偏的时间精同步方法及性能分析

该文导出了互相关时间精同步的性能随频率偏移和信噪比变化的表达式,并提出一种受频偏影响较小的精同步方法。该文对同步性能表达式进行分析,得到在某一频偏下同步序列长度的上限值。新方法将同步序列分段,每段和接收信号分别作互相关,将各段的相关值延时相加作为同步的度量。通过仿真将新方法和其它时间同步方法进行了对比。仿真结果表明,新方法可以大大提高系统抗频偏的能力。     

Thermoelectric Performance of Poly(3,4-Ethylenedioxy-thiophene)/Poly(Styrenesulfonate) Pellets and Films

The thermoelectric performance of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) pellets and free-standing PEDOT/PSS films, prepared from PEDOT/PSS solution containing the additives dimethyl sulfoxide or ethylene glycol, have been systematically investigated. It has been found that the electrical conductivity of free-standing PEDOT/PSS films is invariably much higher than that of PEDOT/PSS pellets, while there is no distinct change in the Seebeck coefficient. The highest electrical conductivity of a free-standing PEDOT/PSS film can be up to 300 S cm⁻¹, five to six times higher than that of PEDOT/PSS pellets (55 S cm⁻¹). The thermal conductivity was measured over a wide temperature range, indicating that PEDOT/PSS has extremely low thermal conductivity. The figure of merit (ZT) of free-standing PEDOT/PSS films with good environmental stability can be up to 10⁻², an order of magnitude higher than that of pressed PEDOT/PSS pellets (10⁻³).     

Low Thermal Conductivity and Enhanced Thermoelectric Performance in In and Lu Double-Filled CoSb<Subscript>3</Subscript> Skutterudites

The thermoelectric properties of indium (In) and lutetium (Lu) double-filled skutterudites In _x Lu _y Co₄Sb₁₂ prepared by high-pressure synthesis were investigated in detail from 4 K to 365 K. Our results indicate that In and Lu double filling can remarkably reduce the thermal conductivity, and substantially improve the thermoelectric performance. A thermoelectric figure of merit of ZT = 0.27 for In_0.13Lu_0.05Co_4.02Sb₁₂ was achieved at 365 K, being larger by one order of magnitude than that for CoSb₃. It is thought that the large difference in resonance frequencies of the In and Lu elements broadens the range of normal phonon scattering in the multifilled skutterudites, helping to achieve an even lower lattice thermal conductivity. This investigation suggests that an effective way to improve the thermoelectric performance of skutterudite materials is to use In and Lu double filling.     

Analysis of two dimensions sparse multicylinder scattering problem using DD-FDTD method

An algorithm of two-dimensional (2-D) domain decomposition finite-difference time-domain (DD-FDTD) using in sparse multicylinders scattering problem is proposed in this paper. The idea of domain decomposition is introduced to divide the sparse problem domain into several subdomains. All of subdomains are connected by means of the 2-D time domain Green's function. As a result, a great deal of meshes memory between cylinders is removed, especially when the distances between cylinders become large. Furthermore, the coupling between cylinders can be regarded as the equivalent cylindrical wave irradiations. The incident signals of the equivalent cylindrical waves are expressed as cylindrical wave input field array (CWIFA) according to Huygens principle. Then the calculation time is significantly reduced. The near-field to far-field transformation is used to obtain the equivalent cylindrical wave; as a result, the calculation time can be reduced further. The new method has been demonstrated in 2-D multicylinders scattering problem. Numerical results are in good agreement with the results obtained using classical FDTD method and moment of methods (MM).     

Cross‐Layer Resource Allocation Scheme for WLANs with Multipacket Reception

Tailored for wireless local area networks, the present paper proposes a cross‐layer resource allocation scheme for multiple‐input multiple‐output orthogonal frequency‐division multiplexing systems. Our cross‐layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.     

磁控溅射Ge/Si多层膜X射线低角衍射界面结构分析

本文对磁控溅射不同结构的Ｇｅ／Ｓｉ多层膜样品进行了Ｘ射线衍射的测试和分析,并进一步采用有过渡层的光学多层膜衍射模型对衍射谱进行了拟合;获得了扩散层厚度和分层厚度等多层膜的结构参数,定性讨论了多层膜中互扩散与分层厚度铁关系。计算结果与实验结果符合较好。     

深入教育改革探索培养创新人才的新思路

为培养适应２１世纪飞速发展的科技竞争需要的优秀人才,我们对现有培养模式所进行的教育改革中,作了一些尝试。吸取ＭＩＴ等国外著名大学的成功办学经验,总结我院在原有教改试点班工作中所取得的成绩,组建了ＭＩＴ电子信息试点班,并以此为突破口．寻求培养宽厚型创新人才的新思路,形成以信息为主线涉及多个学科基础理论的课程体系,带动面上教学。并论述了设立ＭＩＴ电子信息试点班的必要性和可能性,介绍了该试点班的培养目标和培养特色。