On the optimum design of unitary cyclic group space-time codes

In this letter, based on the exact pairwise-error probability, we derive the union bound on the symbol-error probability (SEP) of the differential unitary space-time (DUST) modulation employing group codes. Instead of using the rank-and-determinant or Euclidean distance criteria, we optimize the cyclic group codes such that the union bound on the SEP is minimized for a predetermined scenario, taking into account the number of transmit and receive antennas and the operating signal-to-noise ratio (SNR). Our simulation results show that for a wide range of SNRs, the codes with the minimum union bound for a particular SNR outperform the codes designed based on rank-and-determinant or Euclidean distance criteria.     

60Co辐照预处理对苹果片脱水特性和品质的影响

进行了不同辐照剂量、热风温度、切片厚度对苹果脱水速率及品质的影响试验,结果表明该三因子影响苹果片的脱水速率和外观质量.辐照剂量增加,热风温度增高,脱水速率高,VC含量和复水比下降.辐照剂量、热风温度、切片厚度三因素对脱水速率和干制品的外观质量、VC含量、复水比等四指标大都呈显著影响.     

Structure evolution of conductive polymer composites revealed by solvent vapor induced time-dependent percolation

The authors of this paper synthesized a series of amphiphilic triblock copolymers of polystyrene-b-poly(ethylene glycol)-b-polystyrene (PS-PEG-PS) having different PEG/PS ratios with nearly identical molecular weights of the entire copolymers. The interfacial interactions in the composites consisting of carbon black and the copolymers can thus be tailored. When these conducting composites are exposed to certain solvent vapors, their electrical resistances greatly increase, showing the gas sensitivity. The present work indicated that this switching behavior is controlled by the structural relaxation of the composites because matrix swelling acts as the main mechanism. The response time has been correlated with absolute temperature by Arrhenius equation, and the estimated activation energy reflects mobility of the fillers involved in the solvent induced expansion of the surrounding polymer. Therefore, by using the gas sensibility of the conductive composites, the structure evolution of the composite materials in solid state and the effect of filler/matrix interfacial interaction on the relaxation property of the matrix polymer has been inspected. It was found that lower activation energy represents stronger interfacial interaction in case good solvent of the matrix was used for the test.     

铬盐清洁生产工艺中铝的脱除

分析了K2Cr2O7清洁生产工艺中Al(Ⅲ）-K2CrO4-K2Cr2O7-H2O体系的离子平衡，推导出25℃时混合溶液中[Al(Ⅲ）]和[H^ ],[Cr2O7^2-]/[CrO4^2-]之间的对应关系。并由实验测定验证了这一关系。提出了通过调整K2CrO4碳酸化反应转化率来降低体系中Al(Ⅲ）杂质含量的新方法。工业试验已证明了其可行性。     

单片机系统的动态加密技术

单片机系统产品的加密和解密技术永远是一个矛盾的统一体。然而 ,为了更好的保护好自己的单片机技术成果和知识产权 ,加大解密成本 ,研究新型加密技术仍是保护成果的主要手段之一。文中在讨论了传统的单片机系统加密和解密技术的基础上 ,提出一种实用而有效的动态加密技术的实现方案。     

电子仪器发展趋势

本文在回顾了电子仪器近百年发展的历史的基础上,对国际电子仪器制造商、电子仪器行业及电子仪器本身的发展趋势,以及我国电子仪器的发展情况进行了分析归纳和总结.     

ASP+ADO实现医院门诊在线查询

ASP技术由于其方便 ,灵活及可扩充性等特点和简明、高效的技术优势 ,在Web数据库的开发中获得了广泛的应用。简述了开发Web数据库的重要性 ,介绍了ASP技术的特点及其数据库访问原理 ,ADO对象。实例介绍了ASP实现医院门诊在线查询的方法     

Highly Cooperative Tetrametallic Ruthenium-mu-Oxo-mu-Hydroxo Catalyst for the Alcohol Oxidation Reaction

The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy(3))(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} (1) was synthesized in two steps from the monomeric complex (PCy(3))(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern towards primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C(6)H(4)CH(2)OH (rho = -0.45) and p-X-C(6)H(4)CH(OH)CH(3) (rho = +0.22) (X = OMe, CH(3), H, Cl, CF(3)). Both a sigmoidal curve from the plot of initial rate vs [PhCH(OH)CH(3)] (K(0.5) = 0.34 M; Hill coefficient, n = 4.2+/-0.1) and the phosphine inhibition kinetics revealed the highly cooperative nature of the complex for the oxidation of secondary alcohols.