基于译码转发中继信道的对角正交设计极化空时分组码

构建了基于译码转发中继信道的对角正交设计极化空时分组码(STPBC),该种码可以通过极化天线进行满码率发射和接收.然后设计了码率为1、发射天线数为2和4的码字矩阵,最后与传统对角正交、传统准正交和极化准正交这3种无中继空时分组码(STBC)分别进行了仿真对比.结果表明:2个发射天线和1个接收天线情况下,当BER=10-3时,BPSK调制下STPBC的性能比无中继传统对角正交情况有3.5dB的增益,QPSK调制下有3dB的增益;4个发射天线和1个接收天线情况下,当BER=10-3时,BPSK调制下比上述3种情况分别有6.0,2.7和-1.5dB的增益,QPSK调制下分别有5.5,2.5和-2.5dB的增益;与无中继极化准正交STBC相比,在SNR较低的情况下所提分组码具有较好的性能.     

ZnO microsheet modified TiO<Subscript>2</Subscript> nanoparticle composite films for dye-sensitized solar cells

Randomly oriented ZnO microsheets were successfully self-assembled on TiO₂ nanoparticle (TN) film to act as the scattering layer via a cathodic electrodeposition process. The light scattering properties of ZnO microsheets were studied by UV-Vis spectrometer in the 400–800 nm wavelength range. It was found that ZnO microsheets exhibited excellent ability to scatter the incident light for ZnO microsheet-TiO₂ nanoparticle (ZT) composite films. The results showed that dye-sensitized solar cells (DSSCs) fabricated with ZT composite films showed higher short-circuit density (J_sc) and conversion efficiency than TN-based DSSCs, due to the light scattering properties of ZnO microsheets.     

Single photon response of superconducting nanowire single photon detector

Single photon detection is one of the key technologies for quantum key distribution in quantum communication. As a novel single photon detection technology, superconducting nanowire single photon detector (SNSPD) surpasses conventional semiconducting single photon detectors with high count rate and low dark count rate. In this article, we introduce SNSPD fabricated from NbN ultrathin superconducting film and lab-based SNSPD system. The characteristics of single photon response pulse of SNSPD are analyzed in detail. Also discussed is the relationship between waveform of single photon response and system bandwidth. Circuit model is made to analyze the performance of SNSPD. The simulation result agrees well with the experimental data. Those results are valuable for understanding the mechanism of SNSPD and building future SNSPD system for quantum communication.     

Geochemical characteristics of light hydrocarbons in natural gases from the Turpan-Hami Basin and identification of low-mature gas

Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources. Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas. Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses. The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane, high isoparaffin and low benzene. This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment. These features are consistent with the geological setting of the basin. Comparative studies of isoheptane, heptane, and the carbon isotopic compositions of methane in natural gases, and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams. The parent materials are of type III, and the maturation degree was in the low evolution stage. These are the fundamental characteristics of low-mature gas. Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China. It is likely that this resource will play an important role in future exploration and development of low-mature gas in China.     

谐波测量之初探

由于电力系统运行方式变化,用户设备运行工况不同,使谐波具有较大的随机性、波动性.应针对不同的测试对象确定相应的测试方案,文章对谐波测量进行了初步探索.     

基于"两型一化"变电站设计中的研究

变电站是电力系统中变换电压、接受和分配电能、控制电力的流向和调整电压的电力设施,在电力系统中的地位相当重要.文章对"两型一化"变电站110kV变电站工程设计的具体内容进行了分析.     

基于分数阶傅里叶变换的直扩通信快速线性调频干扰抑制

针对直接序列扩频系统中的线性调频干扰,将短时傅里叶变换和分数阶傅里叶变换相结合,提出了在短时傅里叶域进行线性调频干扰参数粗估计而在分数阶傅里叶域进行精确估计,并根据线性调频干扰在分数阶傅里叶域形成的脉冲位置和强度自适应选择消波区间达到抑制线性调频干扰的目的。仿真实验表明,所提出的干扰抑制方法在干信比JSR40情况下,对线性调频干扰有很好的抑制作用,位错误率BER性能可改善103倍。     

辉绿岩单轴及常规三轴压缩下力学特性试验研究

为了分析坚硬脆性岩石在单轴及常规三轴压缩条件下的强度和变形特性,通过在TAW-2000微机控制电液伺服试验机上对辉绿岩进行单轴及常规三轴压缩试验,主要分析辉绿岩在围压为1、3、5、10 MPa时基本物理力学参数的离散程度,其弹性模量的离散程度指标值较小,在0.27%～3.49%波动,能较好地表征辉绿岩的变形特性。试验结果表明:随着围压的增大,岩石峰值应变和残余应变均表现出显著的线性增长关系,可采用一次函数形式拟合,弹性模量、变形模量和泊松比均表现出较明显的非线性增长关系,可采用幂函数形式进行拟合,但并不会随着围压的增大而无限增大,而是趋于一个稳定值,这一规律为实际工程中不同地应力条件下准确选取弹性模量、泊松比等参数提供理论基础;随着围压的增大,岩石的峰值强度和残余强度均呈现出较显著的线性增长关系,可采用一次函数形式拟合,并计算出黏聚力和内摩擦角,为岩石工程设计时强度参数的选择提供参考依据。     

2-甲氧基萘用作锂离子电池过充保护添加剂

在1mol／LLiPF6／EC＋EMC（体积比1：1）电解液中,用恒流充放电池测试系统测试了2-甲氧基萘对磷酸铁锂电池电化学性能的影响,结果表明添加剂对电池容量特性基本没有影响．过充实验结果则表明添加5％的2．甲氧基萘表现出最优的磷酸铁锂电池的耐过充性能．     

上海65米射电望远镜

正上海65米射电望远镜是亚洲最大、全方位可转动的大型射电望远镜。该望远镜的建成,将促进我国射电天文观测与国际前沿的接轨,提升我国天文观测研究的国际地位,同时也将提升我国深空探测的定轨能力,为我国的嫦娥探月工程、火星探测,以及更遥远的深空探测提供精确定位和定轨的科技支撑。