基于WiFi的无线语音接收终端设计

针对目前的语音调度系统存在实时性差、需要布设大量电缆等问题,设计了一种基于WiFi的无线语音接收终端。该语音接收终端工作时,无线收发模块GS1011接收来自无线网络的数据帧,STM32微控制器以中断方式将接收到的数据放入环形缓存区中,当环形缓存区数据大于播放阈值,STM32微控制器从环形缓存区中读取语音数据并通过音频编解码模块VS1053解码播放。同时,该语音接收终端采用RTP协议结合环形缓存及动态调整语音回放速率的措施来消除网络抖动现象。测试结果表明,该语音接收终端响应时间不到1s,语音信号稳定,消除了网络抖动带来的影响。     

LD3320的嵌入式语音识别系统的应用

语音交互系统是比较人性化的人机操作界面,它需要语音识别系统的支持。LD3320就是这样一款语音识别芯片。介绍了该芯片的工作原理及应用,给出了LD3320与微处理器的硬件接口电路及软件程序。随着高档MCU的不断出现,以MCU为核心的嵌入式语音交互系统会有非常好的应用前景。     

基于滤波的SAR影像去噪方法分析

根据SAR(Synthetic Aperture Radar)影像相干噪声的特点,对现在广泛应用的各种抑制噪声的滤波方法如均值滤波、Frost滤波、增强型Lee滤波、Lee滤波、中值滤波等进行分析,并提出适合本研究区影像的基于小波变换的分量滤波处理去噪方法,利用均值、标准差、平滑指数、PM值、信息熵和平均梯度等评价指标对各种滤波去噪后的影像质量进行评价,并对去噪效果进行对比分析,证明本文所采用的滤波方法对SAR影像噪声有很好的抑制作用,并且较好的保存了图像纹理信息。     

Directions for improving manual fire suppression using a physically based computer simulation

The Swedish Fire Research Board and the U.S. Federal Emergency Management Agency are sponsoring a project to further the understanding of the basic mechanisms involved, as well as to support the development of standards for and to seek ways of improving the performance of portable fire suppression systems used by fire departments.This paper describes a physically based computer model developed to simulate one aspect of the problem: the manual suppression of postflashover fires. This includes: (1) an overview of the physical basis behind the model; (2) a comparison of model predictions with available experimental data, and (3) an analysis of fire suppression effectiveness using the model.The analysis concludes that, when direct access and extinguishment of the burning fuel is not possible, improved fire control occurs with water sprays having a Rosin-Rammler distribution of droplet sizes with volume-median-drop diameters in the 0.15 to 0.35 mm range. This agrees with available experimental data. It is also shown that fire fighting venting and standoff distance requirements may lead to more severe fires requiring more water for control; although venting and water spray induced air/gas flow also serve to channel hot steam and gases away from the fire fighter adding to his safety. The analysis also shows that allowing higher gas and surface temperatures at fire control through improved fire fighter protective clothing and equipment design reduces water flow rate requirements. Additional experimental work is recommended before all these conclusions are considered definitive. Reference: L. M. Pietrzak and G. A. Johanson, Directions for Improving Manual Fire Suppression Using a Physically Based Computer Simulation,Fire Technology, Vol. 22, No. 3, August, 1986, p. 184.     

电能变换领域中随机脉宽调制技术研究概况及展望

相较于传统的脉宽调制技术,随机脉宽调制具备有效的谐波频谱分散能力,从而实现机电负载噪声的削弱。随机脉宽调制技术包括起步的随机开关调制、后续的随机脉冲位置与随机开关频率等3个基本方法。随着电力电子技术的整体发展,随机脉宽调制已从传统的载波调制逐渐拓展到空间矢量调制之中,应用范围日趋广泛,谐波频谱分散与功率谱峰值抑制的效果不断提升。同时,新的优化方案不断被提出,对谐波频谱及功率谱的分散效果亦在不断提高。梳理了随机脉宽调制的研究历程,总结了数种典型的随机脉宽调制的基本原理,并对未来随机脉宽调制的研究方向作出展望,为随机脉宽调制技术的深入研究提供参考。     

Effect of Bio-Based Cobalt Alginate on the Fire Safety and Mechanical Properties for Epoxy Resin

There is a growing demand to develop epoxy resins (EP) with smoke suppression as well as satisfactory flame retardancy. Herein, bio-based cobalt alginate is successfully fabricated and incorporated into EP to prepare EP/Cobalt Alginate composites with better fire safety performance. The addition of cobalt alginate reduces the thermal-decomposition rate, temperature at maximum weight-loss rate of EP, whereas obviously improves the thermal stabilities at a higher temperature range. Furthermore, the addition of cobalt alginate substantially reduces the fire hazard of EP, resulting in 56.2% reduction in peak heat release rate, as well as 17.8% and 56.3% reduction in total smoke production and peak smoke production rate, respectively, compared with EP matrix. Moreover, the presence of cobalt alginate increases smoke-suppressant properties, according to the smoke density test. Additionally, the incorporation of cobalt alginate has no obviously destructive effect on the mechanical properties of EP, while EP/Cobalt Alginate-3 exhibits a 27.0% improvement in impact strength. In prospective, this study may provide a significant method for producing eco-friendly flame retardant EP.     

基于多变量解耦控制的配电网单相接地故障集成化柔性消弧方法

随着静止无功补偿装置、柔性消弧装置、大功率逆变器等电力电子装备应用逐渐增多,配电网柔性化加快发展,但已有电力电子装备存在功能单一、成本高等问题.基于直流侧并接储能元件的直挂式级联H桥变流器,将多变量解耦控制方法与电流消弧方法相结合,实现柔性电力电子装备输出电流在dq0坐标系下的独立调节,使单套柔性电力电子装备同时集成配电网有功功率、无功功率双向流动控制,以及单相接地故障柔性消弧功能,有效提高电力电子装备的利用效率.理论分析以及功率控制和单相接地故障消弧建模仿真结果验证了所提方法的可行性.     

液压伺服系统常用的干扰抑制方法

本文介绍了目前常见的抑制干扰的几种方法，分析了它们各自的特点和适用范围，为合理选择不同抑制干扰的方法提出了一些参考意见。     

防腐保温业务任重道远、大有可为

阐述了国内石油工业的现状与未来，对中国石油工程建设协会防腐保温技术专业委员会的工作提出了要求和建议。     

Grinding-hardening with liquid nitrogen: Mechanisms and technology

This paper studies an innovative development of a steel grinding–hardening technology using an inert cryogen—liquid nitrogen. It was found that phase transformations took place during grinding with the application of liquid nitrogen and resulted in hardened surface layer in a ground component. The layer had a fine laths martensite structure which gave rise to a remarkably high hardness. It was also shown that the treatment can produce superior surface integrity, with compressive surface residual stresses and without surface oxidation. Due to the inert nature of the liquid nitrogen, the grinding process becomes environmentally conscious.