Shorted fractal Sierpinski monopole antenna

This paper describes novel configurations of shorted fractal Sierpinski gasket antenna. The antenna uses half the structure of a conventional Sierpinski gasket antenna and is folded over to be parallel to the ground plane, to form an element similar to that of the inverted L antenna. A quasi log periodic resonance behavior is obtained with a shorting pin placed at the far end of the antenna. Several configurations are shown and a design using two shorting pins which improves the bandwidth at the fundamental band is also demonstrated.     

Semi-blind channel estimation and PAR reduction for MIMO-OFDM system with multiple antennas

A combining of MIMO signal processing with OFDM is regarded as a promising solution of enhancing the performance of next generation wireless system. Therefore, in this paper, an OFDM-based wireless system employing layered space-time architecture is considered for a high-rate transmission. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in MIMO-OFDM system. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be executed based on semi-blind processing in the case of more than two transmitting antennas. And also we evaluate the PAR performance in the MIMO-OFDM system using the SLM and PTS approaches. The investigated SLM and PTS schemes for MIMO-OFDM signals select the transmitted sequence with lowest average PAR over all transmitting antennas and retrieve the side information very accurately at the expense of a slight degradation of the PAR performance. The low probability of false side information can improve the overall detection performance of the MIMO-OFDM system with erroneous side information compared to the ordinary SLM and PTS approaches, respectively. Also, we provide closed form of the average BER performance in MIMO-OFDM system using analytic approach.     

Low-density parity check codes for partial response channels

The goals of this article are twofold: (1) to provide a brief tutorial of the application of low-density parity check (LDPC) codes for partial response (PR) channels under the framework of turbo equalization and (2) to highlight the use of structured LDPC codes in PR systems. We begin by introducing LDPC codes, their graph representations and associated sum-product decoding algorithm, followed by describing the general framework of iterative equalization and decoding approach to combat ISI. We then present explicit constructions of structured LDPC codes, which facilitate efficient implementation of encoding and decoding and show simulation results.     

Nonlinearity in power-current Characteristics of narrow-pulse-driven AlGaInP laser diodes

In this paper, a simple yet effective model is developed to analyze the nonlinearity in power-current characteristics, also known as "kinks", observed in AlGaInP selectively-buried-ridge (SBR) laser diodes driven by narrow pulses (/spl sim/10/sup -7/s). The model takes the temperature-induced waveguide as well as the carrier distribution into account, and the simulation results show good agreement with the experiments. The main factors influencing the kink behavior of SBR lasers are investigated based on this model, and it is believed to be of great help for the optimization AlGaInP laser structure for high-power applications.     

同步仿生机械臂设计

本设计利用安装在人手臂部的加速度传感器采集运动信号,单片机智能运算后发出控制指令,实现机械臂与人臂的同步运动。系统将在采集传感器的输出模拟量经过单片机的处理产生PWM波,使用PWM波驱动舵机实现准确定位,使机械臂实现三自由度的运动。而且还可通过编程和仿生来完成各种预期的作业任务,在构造和性能上兼有人和机器各自的优点,体现了人的智能和适应性。     

4G移动通信终端数据吞吐量测试研究

4G移动通信终端的数据吞吐量测试是验证终端数据吞吐量是否能够达到标准要求的方法,对保障用户的高速接入有重要意义.介绍了3种主要的数据吞吐量测试方法:仪表测试、室内网络测试和外场测试;从测试环境可控性、测试效率、问题复现定位、贴近用户体验等方面,比较了当前主要测试方法之间的优劣,并展望了未来的发展趋势.     

网络教学平台在教学中的应用初探

虽然我们已经迈进二十一世纪有十几年了,科学技术的发展也是日新月异,但是在实际的教学过程中,新的技术在教学中的应用并不广泛、全面。本文以高校计算机基础教学课程为例,分析在新技术支持下的网络教学平台在教学中的初步应用。     

Ag Nanowire Reinforced Highly Stretchable Conductive Fibers for Wearable Electronics

Stretchable conductive fibers have received significant attention due to their possibility of being utilized in wearable and foldable electronics. Here, highly stretchable conductive fiber composed of silver nanowires (AgNWs) and silver nanoparticles (AgNPs) embedded in a styrene–butadiene–styrene (SBS) elastomeric matrix is fabricated. An AgNW‐embedded SBS fiber is fabricated by a simple wet spinning method. Then, the AgNPs are formed on both the surface and inner region of the AgNW‐embedded fiber via repeated cycles of silver precursor absorption and reduction processes. The AgNW‐embedded conductive fiber exhibits superior initial electrical conductivity (σ₀ = 2450 S cm^?1) and elongation at break (900% strain) due to the high weight percentage of the conductive fillers and the use of a highly stretchable SBS elastomer matrix. During the stretching, the embedded AgNWs act as conducting bridges between AgNPs, resulting in the preservation of electrical conductivity under high strain (the rate of conductivity degradation, σ/σ₀ = 4.4% at 100% strain). The AgNW‐embedded conductive fibers show the strain‐sensing behavior with a broad range of applied tensile strain. The AgNW reinforced highly stretchable conductive fibers can be embedded into a smart glove for detecting sign language by integrating five composite fibers in the glove, which can successfully perceive human motions.     

Smart Hybrids of Zn2GeO4 Nanoparticles and Ultrathin g‐C3N4 Layers: Synergistic Lithium Storage and Excellent Electrochemical Performance

Smart hybrids of Zn₂GeO₄ nanoparticles and ultrathin g‐C₃N₄ layers (Zn₂GeO₄/g‐C₃N₄ hybrids) are realized by a facile solution approach, where g‐C₃N₄ layers act as an effective substrate for the nucleation and subsequent in situ growth of Zn₂GeO₄ nanoparticles. A synergistic effect is demonstrated on the two building blocks of Zn₂GeO₄/g‐C₃N₄ hybrids for lithium storage: Zn₂GeO₄ nanoparticles contribute high capacity and serve as spacers to isolate the ultrathin g‐C₃N₄ layers from restacking, resulting in expanded interlayer and exposed vacancies with doubly bonded nitrogen for extra Li‐ion storage and diffusion pathway; 2D g‐C₃N₄ layers, in turn, minimize the strain of particles expansion and prevent the formation of unstable solid electrolyte interphase, leading to highly reversible lithium storage. Benefiting from the remarkable synergy, the Zn₂GeO₄/g‐C₃N₄ hybrids exhibit highly reversible capacity of 1370 mA h g^?1 at 200 mA g^?1 after 140 cycles and excellent rate capability of 950 mA h g^?1 at 2000 mA g^?1. The synergistic effect originating from the hybrids brings out excellent electrochemical performance, and thus casts new light on the development of high‐energy and high‐power anode materials.     

含硼炸药的能量输出特性研究

为了有效提高炸药的爆轰能量,基于硼粉具有约2倍于铝粉的体积热值和质量热值的特点,进行了含硼金属化炸药的水下和空中爆炸能量输出特性测试,研究了硼粉的加入对含铝金属化炸药能量大小及输出结构的影响.试验结果表明,硼粉在爆轰过程中的能量释放主要用来提高水下气泡能和空爆火球的持续时间.