独立分量分析及其在诱发电位提取中的应用

独立分量分析能够在各信号频率混迭的情况下,从它们的线性混合信号中有效分离出原始信号,这为微弱电生理信号的提取提供了途径,受到生物信号处理研究人员的关注.作者研究分析了独立分量分析模型和一种基于负熵判据的定点快速ICA算法的实现,并将该算法运用于仿真诱发电位的提取中,从观测信号(混合信号)中有效地提取出视觉诱发电位.     

煤油裂解产物/空气与煤油/空气在宽温度范围内点火延迟的对比研究

Kerosene is an ideal endothermic hydrocarbon. Its pyrolysis plays a significant role in the thermal protection for high-speed aircraft. Before it reacts, kerosene experiences thermal decomposition in the heat exchanger and produces cracked products. Thus, to use cracked kerosene instead of pure kerosene, knowledge of their ignition properties is needed. In this study, ignition delay times of cracked kerosene/air and kerosene/air were measured in a heated shock tube at temperatures of 657–1333 K, an equivalence ratio of 1.0, and pressures of 1.01 × 10⁵–10.10 × 10⁵ Pa. Ignition delay time was defined as the time interval between the arrival of the reflected shock and the occurrence of the steepest rise of excited-state CH species (CH*) emission at the sidewall measurement location. Pure helium was used as the driver gas for high-temperature measurements in which test times needed to be shorter than 1.5 ms, and tailored mixtures of He/Ar were used when test times could reach up to 15 ms. Arrhenius-type formulas for the relationship between ignition delay time and ignition conditions (temperature and pressure) were obtained by correlating the measured high-temperature data of both fuels. The results reveal that the ignition delay times of both fuels are close, and an increase in the pressure or temperature causes a decrease in the ignition delay time in the high-temperature region (> 1000 K). Both fuels exhibit similar high-temperature ignition delay properties, because they have close pressure exponents (cracked kerosene: τ_ign∝P^-0.85; kerosene:τ_ign∝P^-0.83) and global activation energies (cracked kerosene: E_a = 143.37 kJ·mol^-1; kerosene: E_a = 144.29 kJ·mol^-1). However, in the low-temperature region (< 1000 K), ignition delay characteristics are quite different. For cracked kerosene/air, while the decrease in the temperature still results in an increase in the ignition delay time, the negative temperature coefficient (NTC) of ignition delay does not occur, and the low-temperature ignition data still can be correlated by an Arrhenius-type formula with a much smaller global activation energy compared to that at high temperatures. However, for kerosene/air, this NTC phenomenon was observed, and the Arrhenius-type formula fails to correlate its low-temperature ignition data. At temperatures ranging from 830 to 1000 K, the cracked kerosene ignites faster than the kerosene; at temperatures below 830 K, kerosene ignition delay times become much shorter than those of cracked kerosene. Surrogates for cracked kerosene and kerosene are proposed based on the H/C ratio and average molecular weight in order to simulate ignition delay times for cracked kerosene/air and kerosene/air. The simulation results are in fairly good agreement with current experimental data for the two fuels at high temperatures (> 1000 K). However, in the low-temperature NTC region, the results are in very good agreement with kerosene ignition delay data but disagree with cracked kerosene ignition delay data. The comparison between experimental data and model predictions indicates that refinement of the reaction mechanisms for cracked kerosene and kerosene is needed. These test results are helpful to understand ignition properties of cracked kerosene in developing regenerative cooling technology for high-speed aircraft.     

2D NMR对金钱松皮中的一个三萜皂苷进行结构解析

通过核磁共振谱并结合文献对一个三萜皂苷dammar-24(25)-ene-3β, 6α, 12β, 20 (S)-tetraol-20-O-β-D- pyranoglucoside 进行结构解析. 通过2D NMR(1H-1H COSY、HMQC、HMBC)对其进行了NMR全归属.     

手机导光板熔合微光学阵列研究

为了研究手机侧发光背光模组,理论分析并模拟了在导光板表面直接熔合微光学结构的手机背光系统.结果表明,熔合微光学结构后,手机背光系统的出射光场发生变化,使得部分光线在偏离视场中心55°的方向上会聚,为设计新型集成手机微光学导光板奠定基础.     

ICP-AES测定金合金中钆和铍含量

通过ICP-AES测定金合金中Gd和Be量各种相关因素的试验研究,建立了一个准确可靠的测定方法以替代原国标方法,适用于AuAgCuMnGd、AuAgCuGd、AuNiGd、AuBe合金中钆、铍量的测定,测定含量范围为:0.2%-2%.方法加标回收率:Gd为95.58%-99.98%,Be为96.11%-103.33%.方法测定精密度结果:Gd为1.02%.Be为4.05%.     

清除血浆中LDL用生物活性短肽SDE的合成研究

高脂血症是引起心脑血管疾病的主要原因之一。Ser-Asp-Glu 三肽(SDE)在对血浆中低密度脂蛋白(LDL)的识别及特异性吸附起关键性作用。本实验采用 DCC/HOBt 液相法,合成三肽(SDE)。重点研究反应温度、反应时间和原料配比对 SDE 产率的影响。结果表明本实验成功合成出SDE 三肽。     

适应与超越:大学战略规划与办学环境之互动——读乔治·凯勒《大学战略与规划:美国高等教育管理革命》有感

乔治·凯勒撰写的《大学战略与规划:美国高等教育管理革命》是一本倡导现代大学运用战略规划手段治校的代表著作,其中大学战略规划与办学环境的互动关系是贯穿全书的一条基本线索。办学环境由封闭走向开放的变化使得战略管理被大学主动引入以应对生存危机。聚焦外部办学环境是大学战略规划的基本特征之一,强调战略规划的着眼点在于使学校与不断变化的外部环境协调一致。大学制定战略规划需要进行外部环境分析,包括关注环境变化趋势带来的挑战与机遇,市场取向、认识和趋势,以及竞争形势带来的挑战和机遇三个因素。科学制定战略规划既可帮助大学从被动应付外部环境的激烈竞争和压力转变为主动适应环境变化以求得生存,还可帮助大学认清发展形势,超越环境制约,在环境变化中谋得发展。我国大学应该分析外部办学环境的具体影响,进而制定相应的战略规划,抓住机遇获得发展。     

三相异步电动机三种起动方式的比较研究

研究了三相异步电动机直接起动、定子串电阻起动以及软起动三种起动方式的工作原理,从理论上分析了它们各自起动电流和转速的工作特性,接着在MATLAB/SIMULINK中对这三种起动方式进行了建模与仿真.最后通过对仿真结果的比较分析可知,相比较直接起动和定子串电阻起动方式,软起动能够明显减小起动电流,而且在转速方面,软起动使转速变化更加平缓.     

有机物种类对恒电位电解法测定COD值准确性的影响

以β-PbO2/石墨电极为工作电极,在支持电解溶液中加入一定量待测有机物,在低于析氧电位下进行恒电位电解时,因电极表面吸附态羟基自由基的消耗速率受电解质溶液中有机物分子向电极表面的扩散过程控制,表现为阳极电流强度的增加值(ΔI)与有机物质量浓度ρ之间呈线性关系。本文研究了多种待测有机物的ΔI与ρ的线性关系,发现由于有机物种类不同造成羟基自由基消耗速率不同,因而线性比例系数有所不同。实验结果表明在测定混合水样的化学需氧量(COD)值时,应采用与待测水样具有相似有机物混合比例的标准溶液制作工作曲线,以减少测量误差。