CO分子在Rh低指数面及(331)台阶面上的吸附

应用原子和表面簇合物相互作用的5参数Morse势方法(简称5-MP)及推广的LEPS势对CO-Rh低指数表面体系及(331)台阶面体系进行了系统、全面的研究, 并获得了全部临界点特性. 提出了分子吸附态振动指纹的概念. 理论计算及振动指纹分析表明, 在Rh低指数面及(331)台阶面上的吸附存在共性：随着覆盖度的增加, CO分子先后垂直吸附于顶位、桥位, 且顶位为稳定吸附位, 桥位次之. 在(100)面上, CO分子在顶位、桥位分别获得了2009, 1946 cm^-1的本征振动, 二者之间的结合能之差为0.09 eV; (110)面上, CO分子则分别获得2019, 1961 cm^-1的本征振动; (111)面上, CO分子分别在顶位、桥位、洞位产生了2000, 1912, 1894 cm^-1的振动频率, 三者的结合能依次下降, 顶位、桥位之间的结合能差为0.03 eV; (331)面上, CO分子吸附于(110)台面及(111)台阶面上的顶位以及两等价顶位间的桥位, 分别获得2018, 1987 cm^-1; 1969, 1927 cm^-1的本征振动.     

数据挖掘技术在语音识别中的应用

通过数据挖掘技术实现对语音来源的识别,从而完成对说话人身份的认证以及操作权限的分配,具有非常重要的理论和实际意义。主要针对相同和不同语音内容两个类别的说话人语音识别进行了研究。通过在说话人识别领域广泛应用的梅尔频率倒谱系数进行语音的特征提取,并结合动态时间规整算法进行模式匹配分类。特别地,在不同的语音内容识别探究中,在采用动态时间规整算法前,结合了K-means++算法以及主成分分析算法来对梅尔频率倒谱系数矩阵进行降维和聚类,以保证待匹配模板的维度相近或相同。结果表明,在相同语音内容的识别过程中,选择合适的阈值可以获得较好的识别效果。     

Effects of cutoff thresholds for minor allele frequencies on HapMap resolution: A real dataset-based evaluation of the Chinese Han and Tibetan populations

Genomic variation is the genetic basis of phenotypic diversity among individuals, including variation in disease susceptibility and drug response. The greatest promise of the International HapMap is to provide roadmaps for identifying genetic variants predisposing to complex diseases. Single nucleotide polymorphism （SNP） is the fundamental element of the HapMap. Allele frequency of SNPs is one of the major factors affecting the resulting HapMap, being the factor upon which linkage disequilibrium （LD） is calculated, haplotypes are constructed, and tagging SNPs （tagSNPs） are selected. The cutoff thresholds for the frequency of minor alleles used in the making of the map therefore have profound effects on the resolution of that map. To date most researchers have adopted their own cutoff thresh- olds, and there has been little real dataset-based evaluation of the effects of different cutoff thresholds on HapMap resolution. In an attempt to assess the implications of different cutoff values, we analyzed our own data for the centromeric genes on Chromosome 15 in Chinese Han and Tibetan populations, with respect to minor allele frequency cutoff values of 〉0.01 （0.01 group）, 〉0.05 （0.05 group）, and 〉0.10 （0.10 group）, and constructed HapMaps from each of the datasets. The resolution, study power and cost-effectiveness for each of the maps were compared. Our results show that the 0.01 threshold provides the greatest power （P= 0.019 in Han and P= 0.029 in Tibetan for 0.01 vs. 0.05 threshold） and de- tects most population-specific haploypes （P= 0.012 for 0.01 vs. 0.05 threshold）. However, in the regions studied, the 0.05 cutoff threshold did not significantly increase power above the 0.10 threshold （P = 0.191 in Han; 1.000 in Tibetans）, and did not improve resolution over the 0.10 value for population- specific haplotypes （P= 0.592） neither. Furthermore the 0.05 and 0.10 values produced the same figures for tagging efficiency, LD block number, LD length, study power and cost-savings in the Tibetan population. These results suggest that a lower cutoff value is more appropriate for studies in which population-specific haplotypes are crucial, and that the most appropriate cutoff value may differ between populations. Due to the limited genes studied in this project more studies should be conducted to further address this important issue.     

Adaptive compensating method for Doppler frequency shift using LMS and phase estimation

The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the phase offsets due to frequency shift are linear. Based on this premise, the  compensation processes are: firstly, the phase offsets between the base band neighbor-symbols after clock recovery are unbiasedly estimated among the reference symbols; then, the receiving signals symbols are adjusted by the phase estimation value; finally, the phase offsets after adjusting are compensated by the least mean squares (LMS) algorithm. In order to express the compensation processes and ability clearly, the quadrature phase shift keying (QPSK) modulation signals are regarded as examples for Matlab simulation. BER simulations are carried out using the Monte-Carlo method. The learning curves are obtained to study the algorithm’s convergence ability. The constellation figures are also simulated to observe the compensation results directly.     

戈壁下垫面空气动力学参数确定的再研究

提出一种确定地表粗糙度z₀的方法。该方法仅需利用精细风廓线资料进行计算,误差较小,尤其适用于近中性层结观测较困难的情况。根据2006年夏季河西走廊戈壁地区的大气边界层观测资料,利用该方法确定的z₀为0.60mm左右,和前人方法计算结果0.78mm接近,证实了此方法和z₀数值的可靠性和可信度。此外,由于不同测量高度代表不同区域尺度上的特征,地表粗糙度的确定还应考虑风廓线的观测高度及分布状态。     

具有带阻特性的新型超宽带天线的设计

设计了一种具有带阻特性的超宽带天线,工作频带为2.4～12.4 GHz．为了避免与常用频段信号之间的干扰,采用在馈线终端开U型槽的方法实现了对WLAN（5.15～5.35 GHz,5.725～5.825 GHz）频率范围的阻隔,阻隔频段为5～6 GHz（VSWR＞2）．使用MoM数值计算对结构进行仿真,并与实测VSWR值比较,结果基本一致．仿真结果表明,相对原天线的VSWR曲线,除阻带5～6 GHz范围外,其余频段两者基本吻合,说明U型槽对于天线的作用具有独立性．     

基于液体静压支承转台的动力学分析与数值模拟

根据实际工程中的液体静压支承系统,将油膜力简化为弹簧支承,建立了工作转台的有限元模型,对工作转台的动力学特性进行了分析。通过数值模拟,研究了单个油腔供油量相同和总供油量不变两种状况下,油腔数目对液体静压支承工作转台振动频率的影响。保持各个油腔供油量相同,在一定的供油范围内,不同油腔数目的液体静压支承工作转台的振动频率随着油腔数目和单个油腔供油量的增大而增大,且这种增大是非线性的。保持总供油量不变,且油腔数目较多(大于6)时,可以不考虑油腔数目对工作转台低阶振动频率的影响。这对进一步研究液体静压支承系统整体的动力学特性提供了一定的理论依据。     

水平填充床中纤维质燃料正向阴燃数值模拟研究

根据多孔燃料三步反应动力学过程,建立了2D非稳态纤维质材料填充床阴燃的数学模型.阴燃的化学动力过程包括燃料热解、燃料放热氧化及焦炭的放热氧化.该模型既考虑了固-气之间的热交换,也考虑到气体在多孔介质内的扩散系数变化.数值模拟了来流速度对阴燃速度及平均最高温度的影响,结果表明:阴燃传播速度与来流速度基本上呈线性关系,来流速度对阴燃最高温度影响不大.同时也模拟了燃料阴燃过程中气体组分(O2、CO、CO2及H2O)的变化.通过改变3个反应指前频率因子发现:增大A2(燃料氧化频率因子)会加速阴燃,增大A1(燃料热解频率因子)和A3(焦炭氧化频率因子)均会减小燃料阴燃传播速度.     

软件化多频地波雷达频率合成器设计

针对高频地波雷达海洋动力学参数多频探测的技术特点,提出了一种基于波形库的软件化多频地波雷达频率合成器实现方案,可以同时和分时产生多路脉内线性调频信号,各路信号形式、频率、初相、幅度等都独立可控,解决了雷达波形种类、幅相控制、捷变时间受限等问题,较大提高雷达系统性能;给出系统的硬软件实现方案.测试结果表明,该数字频率源的相位噪声在偏离载波1 kHz处达-112 dBc/Hz,满足高频地波雷达进行长时间相干积累对频率源稳定性的要求.     

降低WSN目标失跟率的自适应采样频率方法

针对无线传感器网络(WSN)固定采样频率下机动性目标失跟率较高的问题,分析了机动性目标失跟的机理,建立了表征失跟率、采样频率、目标速率关系的数学模型,提出了降低目标失跟率的自适应采样频率方法,并对速度大小、方向变化的机动性目标跟踪问题进行仿真实验.结果表明,与固定采样频率方法相比,采样间隔距离参量d恒取不同值时自适应采样频率方法的失跟率平均降低了3.3%~6.0%;当d恒等于50m时,失跟率平均降低6.0%,网络能耗降低13.1%.