Singularity detection of the rabbit electrocardiogram: An evolutionary spectral method

The time–frequency characteristics of the spectral density of non-stationary signals (NSS) in the neighborhood of an instant time point can be determined using the evolutionary spectral analysis. An experimental rabbit model involving ligation of the left anterior descending coronary artery to simulate the physiology of early phase myocardial ischemia (EPMI) has been previously described. Clinically, EPMI derived from left coronary artery stenosis is the main symptom of coronary heart diseases including acute myocardial infarction. Here, we propose a new algorithm for estimating the evolutionary spectral density functions, which is an effective approach to determine the instantaneous frequency spectra (IFS) of NSS under the uncertainty principle in the time–frequency domain. The localization singularity information in the data recorded from a living system could be detected by means of the IFS. Electrocardiogram (ECG) data recorded from experimental rabbits were analyzed with the new algorithm. Results showed that the Q’s value of the evolutionary spectral quality number of the QRS-complex data was the characteristic parameter of ECG, and there was a matched connection between the time–frequency characteristics of QRS-complex data and the myocardial ischemia symptoms of the rabbits. These results provide valuable information regarding features of the EPMI for use in clinical diagnoses.     

Limit of Julia sets forz d +c

The limit behavior of Julia set J(fd,c) for polynomials fd,c(z) = zd + c is considered. That { J( fd,c) } d≥2 converges to the unit circle S1 in Hausdorff metric for some fixed parameter c is proved and some examples showing { J( fd,C) } d≥2 has no limit are given.     

线性交换子的加权估计

 多线性交换子T_b(f)(x)=∫_Rⁿ∏_i=1^m(b_i(x)-b_i(y))k(x,y)f(y)dy在L^p(Rⁿ)(1K是一个标准的Calderón-Zygmund核.主要研究交换子Mf(x)=sup_x∈Q∫_Q|f(y)|dy,其中f∈L_loc(Rⁿ),x∈Rⁿ,Q是任何包含x的方体,并用Sharp极大估计得到了该多线性交换子在Herz空间的一个加权有界性.     

应用正交试验法的RHT模型参数敏感性研究

基于RHT模型的理论分析,选出A、N、B、M、B_Q、f_s/f_c、T_ten、D₁和E_f,min 9个参数作为正交试验分析参数,研究RHT模型中参数的敏感性.运用Autodyn程序对弹丸侵彻混凝土过程进行数值分析,确定了不同参数、不同水平值下弹丸的侵彻深度.采用极差分析法对参数的敏感程度进行量化分析,得出9个参数的敏感性排序为B > E_f,min > T_ten > f_s/f_c > N > M > D₁ > B_Q > A.结合3组典型数值试验损伤云图和侵彻深度的对比分析,认为参数B、E_f,min和T_ten对数值模拟试验结果的影响极大,应采取可靠的技术手段准确确定其取值.      

A high-Tc dc-SQUID-based single-channel MCG and its performance

A single-channel high-Tc dc-SQUID magnetometer and gradiometer have been developed to record the magnetic field component perpendicular to the human chest generated by heart-beat. Magnetocardiogram (MCG) measurements have been carried out inside a magnetically shielded room. By sequentially adjusting a non-magnetic patient table with 5 cm pitch in X and Y directions, the field signals on a rectangle grid 5 × 5 over the chest area were registered in real time trace point by point with a typical dwell time over 30 cardiocycles each. Utilizing standard electrocardiogram (ECG) recordings as timing reference measured simultaneously with the MCG signals, the MCG data were then averaged and combined to form magnetic field patterns every 10 ms or so. Both the current dipole, which is parallel to MCG measuring plane and produces the vertical magnetic field, and its depth were determined as a function of time in a standard way. We have compared the MCG of healthy hearts with that of a heart with right bundle branch block. Significant differences between their MCGs have been observed.     

Higher order moment spectra time-frequency analysis of the geophysical signal

On the basis of an introduction of the Wigner Higher-Order spectra (WHOS) and a general class of time-frequency higher-order moment spectra, the geophysical signal was analyzed using the higher order time-frequency distributions (TFD). Simulation results obtained in this paper show that the higher-order TFD (Wigner Bispectrum, Wigner Trispectrum and Choi-Williams Trispectrum) have much better Time-Frequency Concentration than the second-order TFD, and the reduced interference higher-order TFD such as CWT can effectively reduce the cross-term in multicomponent signals and simultaneously obtain high time-frequency concentration. Foundation item; Supported by the National Natural Science Foundation of China (49904010) Biography: Liu Xiang-hong (1977-), female, Master candidate, research interest: modern signal processing.     

二苯环丙烷衍生物的晶体结构与分子结构

用Ｘ射线单晶衍射法测定二苯环丙烷衍生物Ｃ１６Ｈ１２ＮＣｌ晶体结构和分子结构,晶体属正交晶系空间群Ｐｚ１ｚ１ｚ１,晶胞参数ａ＝０．７６８１７（３）ｎｍ,ｂ＝１．１６３０７（４）ｎｍ,ｃ＝１．４２０５７（５）ｎｍ,ｖ＝１．２６９２（７）ｎｍ３,Ｚ＝４．Ｄｅ＝１．３２８ｇｃｍ－３,Ｒ＝０．０４７,ＲＷ＝０．０５０。并讨论了分子结构。     

High temperature superconducting (HTS) C-band oscillator with phase noise of −134 dBc/Hz

A high Q HTS cavity resonator with resonating frequency f₀= 5.624 GHz was fabricated using high quality HTS film and high purity sapphire. The unloaded quality factor of the HTS resonator was as high as Q _u= 1.09xl0⁶ at the nitrogen temperature, 77 K. A HTS local oscillator combining the high Q cavity resonator with a C-band low noise GaAs HEMT amplifier was then designed and constructed. The phase noise of the oscillator, measured by a HP 3048A noise measurement system, is ?134 dBc/Hz at 10 kHz offset when the temperature is 77 K. This result is close to the best level reported by other groups in the world.     

一类解析Toeplitz算子的约化子空间与群的特征

设A_r为复平面中的圆环{z:r|z|1},L_a~2(A_r)为A_r上的Bergman空间.从局部逆的代数结构的新视角研究解析Toeplitz算子的约化子空间.首先证明L_a~2(A_r)上Toeplitz算子T_(z~N)的交换子的表示,再次证明zN的全体局部逆组成的集合在复合映射下是循环群,最后证明了循环群的特征与Toeplitz算子T_(z~N)的极小约化子空间是一一对应的.     

Synthesis and characterization of spinel Li_(1.05)Cr_(0.1)Mn_(1.9)O_(4-z)F_z as cathode materials for lithium-ion batteries

Samples with the nominal stoichiometry Li_1.05Cr_0.1Mn_1.9O_4−z F _z (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd3m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li_1.05Cr_0.1Mn_1.9O₄ spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li_1.05Cr_0.1Mn_1.9O_4−z F _z samples deliver relatively low capacity and poor cycling properties at 55°C.     

SL（2，Qp）中的非初等离散子群的代数收敛性

在Kleinian群中，研究离散群的代数收敛性是一个重要的问题，群列的代数收敛性与流形的形变以及极限集的Hausdorff维数的收敛性有密切关系.随着非阿基米德域上的李群和非阿基米德域上的动力系统的发展，讨论非阿基米德域上的离散群的代数收敛性就是一个重要的问题.这篇文章讨论了PSL（2,Q_p）中由r个元素生成的非初等离散群的代数收敛性，利用PSL（2,Q_p）中关于子群的非阿基米德Jorgensen不等式，以及群双曲Berkovich空间上的双曲等距性，证明了非初等群列代数收敛到非初等群列上.     

用叠加谱比法研究四川地区Lg尾波Q值的区域性变化

 运用单台叠加谱比法,分析了成都台网4个台站的29个地震记录的垂直分量,反演得出与各射线路径相对应的Lg尾波的Q₀值.结果表明:Q₀值的分布特征与构造活动性密切相关.在构造活动剧烈的龙门山断裂、鲜水河断裂和安宁河断裂,尤其是在这三大断裂的交汇处,Q₀值呈现出相当低的值,约在150～210的范围内.在四川盆地的大部分地区,随着构造活动的减弱,Q₀值有所抬升,约为240～270.在四川盆地的东部,Q₀值可达300.在离开断裂区的四川北部,Q₀值在250～300的范围内变化.     

Studies on the behaviors of PbSO4/Pb and PbO2/PbSO4 electrodes prepared from lead carbonate by powder microelectrode technique

The behaviors of PbSO₄/Pb and PbO₂/PbSO₄ electrode prepared from PbCO₃ have been examined using powder microelectrode(PME) technique and cyclic voltammetry(CV). Firstly, PMEs packed with PbCO₃ transformed into PbSO₄ PME in 1.0 mol/L H₂SO₄ solution at 30 °C, and then the PbSO₄ in the PMEs were formed to Pb or PbO₂ using an unsymmetrical signal (Q _a/Q _c for PbSO₄/Pb electrode andQ _c/Q _a for PbO₂/PbSO₄ electrode being 0.1–0.3) in 2.5 mol/L H₂SO₄ solution. The results show that the CV characteristic of either PbSO₄/Pb or PbO₂/PhSO₄ PME prepared from PbCO₂ are as good as that of both electrodes made from lead oxide powder produced by ball mill. Foundation item: Supported by the National Natural Science of China(29677013) and Chenguang Foundation of Wuhan Municipal Science and Technology Commission(20005004022) Biography: Dai Zhong-xu(1968-), male, Lecturer, Ph. D. candidate, research direction: electrochemistry.     

Instability of relativistic electron beam with strong magnetic field

Stability criteria for a weak relativistic beam-plasma interaction in a strong magnetic field are found. Two beam modes occur,ω≈k _zC andω≈k _zC-ω_c. The dispersion equation of electrostatic two-stream is exactly solved with analytical method.     

时频域波前检测方法抗振性能研究

针对用于现场测试的移相干涉测量系统对振动的高度敏感而过于复杂的问题,提出一种可用于现场测试的小型化、抗振动的时频域波前检测方法.采集一系列连续移相的干涉图,通过对干涉图中各点时序光强序列的频谱进行宽带滤波获取相位统计信息.线性拟合相位统计信息后,对随机噪声的影响进行了多次取平均,将环境振动、移相非线性等非随机性扰动的影响归结为一个与像素坐标无关的值,实现了抗扰动的目的.仿真实验统计了λ/100波长精度要求下最大可承受振动的幅频积及其变化规律.研究结果验证了本方法的可行性,并为本方法在小型化移相干涉仪中的应用提供了依据.     

非平稳随机激励下悬架系统动态频域分布研究

车辆在变速行驶状态下所受路面激励是非平稳随机过程;针对此状态下悬架系统动力学响应在时域和频域分布问题,基于车速参数通过线性时变系统法建立车辆所受路面激励模型。提出"动态频域"概念,建立1/4悬架系统模型。利用精细积分法研究车速变化导致的车身振动响应峰值频带变化特性,揭示非平稳随机激励下系统响应动态频域分布规律。研究可为非平稳随机振动变频域控制与应用提供理论参考,并为提高车辆在复杂行驶工况下的运行品质提供一种新的思路。     

基于广义S变换的信号提取与抑噪

S变换结合了短时傅里叶变换和小波变换的优点,是非平稳信号时频分析的有力工具.为了提高S变换在应用中的实用性和灵活性,该文将S变换改造成时频分辨率可调的广义S变换.广义S变换具有多分辨率特性,利用其高质量的时频分布,在时频域中设计了两种时频滤波器.前者用来实现非平稳信号中特定信号分量的提取,也可滤除处于特定时频平面中的噪声;后者直接应用广义S变换的时频谱实现,用于含高斯白噪声信号的滤波,达到了突出有效信号和压制噪声的效果.几种信号模型的仿真试验显示了它们在信号提取和抑制噪声中应用的有效性.     

HRP标记的二抗检测heme结合蛋白造成假阳性问题的探讨

为了验证对辣根过氧化物酶(horseradish peroxidase, HRP)作为二抗标记物在检测heme结合蛋白时产生假阳性问题的推测,以菠菜细胞色素b_6f复合体(Cyt b_6f)和铁氧还蛋白-NADP~+氧化还原酶(FNR)为检测对象(前者含有heme结合蛋白Cyt f,后者不含heme基团),采用菠菜FNR一抗、HRP和碱性磷酸酶(alkaline phosphatase,ALP)标记的二抗,设计对比实验。结果表明,在使用HRP标记的二抗体系中,Cyt f不经一抗和二抗孵育即可显色,这是明显的假阳性;而在ALP标记的二抗体系中,Cyt f条带不显色,只有FNR条带显色。在western blot实验中,如果被检测蛋白为heme结合蛋白或者混有少量heme结合蛋白,应避免采用HRP标记的二抗,建议使用ALP标记的二抗或者其他二抗产品;heme结合蛋白具有类似HRP的氧化还原酶活性,其本身可以和显色液反应,从而产生假阳性,干扰对实验结果的判断。     

Riemann Boundary Value Problem with Square Roots on an Open Arc

The Riemann boundary value problem with square roots in class h0 when the jumping curve is an open arc in the complex plane is considered. It is solved by reducing it to a classical Riemann boundary value problem so that its solutions are obtained in closed form. In certain cases, some auxiliary function ω（z）is introduced. With different choices of ω（z）＇s, some interesting examples are illustrated.     

基于正弦模型的语音识别时频特征

为改善语音识别系统的性能,采用时频分布参数来描述语音特征。由于时频分布参数考虑到语音信号内在的非平稳特性,因此能够更准确地描述语音信号的时频特性。对基于正弦模型的多种时频参数(能量谱和幅度加权瞬时频谱)进行了比较,并在基于隐马尔可夫模型的连接词语音识别系统中进行了实验仿真。结果表明,单独采用时频分布参数作为ASR的前端特征并不能改善识别率;而采用标准ASR特征和能量谱时频特征的联合前端特征,可以有效地改善语音识别系统的识别效果。