Speech transmission using rate-compatible trellis codes andembedded source coding

This paper presents bandwidth-efficient speech transmission systems using rate-compatible channel coders and variable bitrate embedded source coders. Rate-compatible punctured convolutional codes (RCPC) are often used to provide unequal error protection (UEP) via progressive bit puncturing. RCPC codes are well suited for constellations for which Euclidean and Hamming distances are equivalent (BPSK and 4-PSK). This paper introduces rate-compatible punctured trellis codes (RCPT) where rate compatibility and UEP are provided via progressive puncturing of symbols in a trellis. RCPT codes constitute a special class of codes designed to maximize residual Euclidean distances (RED) after symbol puncturing. They can be designed for any constellation, allowing for higher throughput than when restricted to using 4-PSK. We apply RCPC and RCPT to two embedded source coders: a perceptual subband coder and the ITU embedded ADPCM G.727 standard. Different operating modes with distinct source/channel bit allocation and UEP are defined. Each mode is optimal for a certain range of AWGN channel SNRs. Performance results using an 8-PSK constellation clearly illustrate the wide range of channel conditions at which the adaptive scheme using RCPT can operate. For an 8-PSK constellation, RCPT codes are compared to RCPC with bit interleaved coded modulation codes (RCPC-BICM). We also compare performance to RCPC codes used with a 4-PSK constellation     

基于全景虚拟现实技术的科普系统

本文设计了基于全景虚拟现实技术的科普系统架构及功能框架.主要针对现实中的科普植物对象进3D建模,并进行三维全景展示,实现一个基于Web3D的科普系统.     

Electrochemical behavior of microbiologically influenced corrosion on Fe3A1 in marine environment

the passivating film of the inner layer was absolutely destroyed by microbial metabolic products.     

大流量空气分布器动力性能试验台的设计与研制

设计并研制成功了国内可测风量最大的空气分布器动力性能试验台，其系统误差不大于２％，为科研和教学打下了良好的基础。     

新型Bi2O3/石英柱粒子电极对甲基橙的降解研究

通过浸渍焙烧法制备了Bi2O3/石英柱粒子电极,分别采用了扫描电子显微镜、能量色散X射线能谱和X射线衍射等表征手段对粒子电极的形貌、晶相和组成进行了表征。通过对甲基橙的降解,证明了粒子电极的电催化活性并优化了粒子电极反应参数。结果表明,氧化铋成功地负载在石英柱表面,且表明了三斜相的氧化铋具有良好的电催化性能;在电解电压为9V,粒子投加量为15g,初始质量浓度为200mg/L,电解质浓度为1g/L,曝气量为8L/min,处理120min后,对甲基橙的去除率可以达到95%,能耗为7.8kWh/kg(以COD计),明显优于二维电极体系,且经过5次重复使用后,粒子电极依然具有良好的电催化性能。     

基于MATLAB的平衡式复合齿轮泵的多目标优化

以平衡式复合齿轮泵体积最小、流量脉动最小为目标函数,建立数学模型。运用MATLAB优化工具箱对相关参数进行多目标优化。采用优化工具箱中的fgoalattain函数编写程序,并进行计算机求解,使其在满足约束条件下复合齿轮泵的体积和流量脉动最小。     

Emerging Synthetic Methods and Applications of MOF-Based Gels in Supercapacitors,Water Treatment,Catalysis, Adsorption,and Energy Storage

Metal–organic frameworks (MOFs), which are synthesized through the self-assembly of organic ligands and inorganic metals, have drawn considerable research interest owing to their unique properties and attractive structures. Many studies on various MOF derivatives, such as MOFs and cellulose aerogels, hydrogel composite materials, and bimetallic-centered MOF materials, have provided the potential for wide application of MOFs. However, MOFs mostly exist in the form of powder particles, which are difficult to form. In addition, MOFs have problems with structural instability. MOF-based gels can overcome this problem. MOF-based gels also have significant advantages in secondary processing. In this review, synthetic methods for MOF-based gels, particularly the synergistic effect with other materials, are introduced. The applications of MOF-based hydrogels and aerogels in supercapacitors, water treatment, catalysis, adsorption, and energy storage are also discussed.     

木棉及其混合纤维非织造材料吸声预测模型

以Allard模型为基础,采用等效流体的方法,拟建立一个能够准确描述木棉及其混合纤维非织造材料吸声行为的吸声模型。该模型结合木棉纤维的大中空结构,考虑了材料的热传导效应及纤维框架的柔软性。使用新建立的吸声模型及Allard模型分别对4种不同结构的木棉纤维非织造材料的吸声系数及比表面阻抗进行了计算,并将计算值与实验样品的测量值进行比较。结果表明:新模型的计算结果更接近实验值,说明新模型更适用于木棉及其混合纤维非织造材料吸声性能的预测,为工业产品的设计提供了理论参考。     

国产聚乙烯醇类分散剂在悬浮法PVC生产中的应用

通过对比目前使用的3种进口聚乙烯醇分散剂(A、B、C)和3种国产聚乙烯醇分散剂(1、2、3)的各项性能,分析了分散剂产品差异的原因,研究了不同国产分散剂替代进口分散剂对悬浮法高聚合度PVC树脂生产工艺参数和产品性能的影响.结果表明:①分散剂1与其他分散剂混合使用效果较好,单独使用分散剂1与同类进口分散剂相比有明显差距;...