Hollow Engineering to Co@N-Doped Carbon Nanocages via Synergistic Protecting-Etching Strategy for Ultrahigh Microwave Absorption

Rational manipulation of hollow structure with uniform heterojunctions is evolving as an effective approach to meet the lightweight and high-performance microwave absorption for metal-organic frameworks (MOFs) derived absorbers. Herein, a new and controlled synergistic protecting-etching strategy is proposed to construct shelled ZIF-67 rhombic dodecahedral cages using tannic acid under theoretical guidance, then hollow Co@N-doped carbon nanocages with uniform heterojunctions and hierarchical micro-meso-macropores are obtained via a pyrolysis process, which addresses the shortcomings of using sacrificing templates or corrosive agents. The outer Co@N-doped carbon shell, composed of highly dispersive core-shell heterojunctions, possesses micro-mesopores while the inner hollow macroporous cavity endows the absorbers with lightweight characteristics. Accordingly, the maximum reflection loss is −60.6 dB at 2.4 mm and the absorption bandwidth reaches 5.1 GHz at 1.9 mm with 10 wt% filler loading, exhibiting superior specific reflection loss compared with the vast majority of previous MOFs derived absorbers. Furthermore, this synergistic protecting-etching strategy provides inspiration for precisely creating a hollow void inside other MOFs crystals and broadens the desirable candidates for lightweight and high-efficient microwave absorbers.     

二阶压控电压源低通滤波器设计

本文详细介绍二阶压控电压源低通滤波器的设计方法,给出了其通用表达式。设计方法是根据所需转折频率,在1:2至1:10较宽的范围内灵活取两电容值,再计算出与灵活选取的电容准确匹配的电阻阻值。相对于查表法、图示法取值更具灵活性和实用性,由于不需要精确匹配成本较高的电容,此方法还具有成本较低的优势。用Multisim-10仿真软件对所设计的二阶压控电压源低通滤波器进行模拟仿真,结果表明与理论计算符合得很好。     

飞秒激光触发光电导天线产生太赫兹波的研究

研究了光电导天线产生太赫兹波的辐射特性,利用麦克斯韦方程及其边界条件,计算了近远场的电场强度;采用电磁波时域有限差分方法（FDTD）,在Matlab系统软件中,用C语言编写程序计算光电导偶极天线的辐射太赫兹波的空间电磁场分布,并在计算机上以伪彩色图形显示,这种电磁场的可视化结果为天线的设计和改进提供了直观的物理依据。     

大、中型地下车库智能寻车系统

为了提高停车场的服务水平,停车场智能管理系统是必不可少的.它已经在大部分停车场发挥着重要作用,在为人们停车带来方便的同时也具有良好的社会效益和经济效益.在大、中型地下车库中,车主返回停车场时,由于停车场太大或者地形不熟,车主容易找不到车,故提出了智能反向寻车系统.该系统可以帮助车主尽快找到车辆停放的区域,提高车主的满意...     

半行波半导体激光放大器超短光脉冲响应及开关特性的实验研究

本文对半行波半导体激光放大器的脉冲响应及开关特性进行了实验研究。脉宽为27ps,重复频率为1GHz的超短光脉冲串通过放大器后脉冲无展宽。当对放大器的注入电流进行调制时,放大器可起到高速光开关的作用。     

GaAs半导体掺杂浓度的电反射光谱的研究

在波长300～1 100nm范围内,对GaAs进行了电反射光谱的研究。建立了电反射光谱的测试系统,并对实验和理论作了详细分析。推导了某一固定波长电反射光谱与半导体表面掺杂浓度的理论关系。并利用电反射光谱的实验曲线计算了GaAs的表面掺杂浓度,所得结果与电化学C—V的测试结果一致,其精度为5％。     

Growth of GaAs1−xPx/GaAs and InAsxP1−x/InP strained quantum wells for optoelectronic devices by gas-source molecular beam epitaxy

In this paper we show that pseudomorphically strained heterostructures of InAs _x P_1−x /InP may be an alternative to lattice-matched heterostructures of In_1−x Ga _x As _y P_1−y /InP for optoelectronic applications. We first studied the group-V composition control in the gas-source molecular beam epitaxy (GSMBE) of the GaAs_1-x P _x /GaAs system. Then we studied GSMBE of strained InAs _x P_1−x /InP multiple quantum wells with the ternary well layer in the composition range 0.15 <x < 0.75. Structural and optical properties were characterized by high-resolution x-ray rocking curves, transmission electron microscopy, absorption and low-temperature photoluminescence measurements. High-quality multiple-quantum-well structures were obtained even for highly strained (up to 2.5%) samples. The achievement of sharp excitonic absorptions at 1.06, 1.3 and 1.55μm at room temperature from InAs _x P_1−x /InP quantum wells suggests the possibility of long-wavelength optoelectronic applications.     

Fast full search equivalent encoding algorithms for imagecompression using vector quantization

Three fast search routines to be used in the encoding phase of vector quantization (VQ) image compression systems are presented. These routines, which are based on geometric considerations, provide the same results as an exhaustive (or full) search. Examples show that the proposed algorithms need only 3-20% of the number of mathematical operations required by a full search and fewer than 50% of the operations required by recently proposed alternatives.     

Integrated physics-oriented statistical modeling, simulation, andoptimization [MESFETs]

Physics-based modeling of MESFETs is addressed from the point of view of efficient simulation, accurate behavior prediction and robust parameter extraction. A novel integration of a large-signal physics-based model into the harmonic balance equations for simulation of nonlinear circuits, involving an efficient Newton update, is presented and exploited in a gradient-based FAST (feasible adjoint sensitivity technique) circuit optimization technique. For yield-driven MMIC design a relevant physics-based statistical modeling methodology is presented. Quadratic approximation of responses and gradients suitable for yield optimization is discussed. The authors verify their theoretical contributions and exemplify their computational results using built-in and user-programmable modeling capabilities of the CAE systems OSA90/hope and HarPE. Results of device modeling using a field-theoretic nonlinear device simulator are reported     

Efficient algorithms for SS/TDMA scheduling

Efficient scheduling algorithms for the slot assignment problem in a satellite-switched time-division multiple-access (SS/TDMA) system are presented. This problem is translated into a modified open-shop scheduling problem, allowing the use of known optimal algorithms. Their complexity is expressed as a function of the following parameters: the number of nonzero entries in the demand matrix, the number of uplinks, and the number of downlinks. According to the values of these parameters, the algorithm with the lowest computational complexity can be adopted. Although the computational complexity of previously published algorithms is drastically reduced, simulation results show that the results are close to previously presented solutions in terms of the assignment duration and the number of switching matrices