多点时序MCG数据的处理和利用

在简易磁屏蔽室中,用单通道的高温超导 rf SQUID梯度计构成心磁图(MCG)测量系统,依照MCG测定部位的约定,测得数例成人胸前多点MCG.不计心动周期随时间的变化,用数据分析软件对这些MCG数据进行分析处理, 得到包括了空间信息、可直观展示心脏电磁活动的二维心磁图谱(例如等磁图、时序等磁图、电流箭头图和时序电流箭头图等).     

等效电流偶极子(ECD)模型在MCG场源定位中的应用

等效电流偶极子(ECD)模型具有简要明确性，已经在心磁图(MCG)的逆问题中，如确定WPW综合症、心脏异常搏动根源、心律失常等方面，得到广泛应用．在多通道体表电势图(BSPM)的测量中也应用ECD．本文讨论用ECD的定位方法，临床研究仿真对ECD获得结果的描述，造影与动物研究和体导体模型的影响．     

用于心磁图测量的基于高温超导量子干涉仪磁强计的有源补偿

我们建立了一套基于高温超导量子干涉仪(SQUID)的可靠的、经济型的单通道心磁图(MCG)系统,该系统在一个简易的磁屏蔽室(MSR)中运行.实验结果表明,对于消除心磁测量中的环境噪声,简易磁屏蔽室和有源补偿相结合是一个很合适的方案,这种方案对心磁图的普及有实际的帮助.同时,本文给出了一个有源补偿的简单模型,并将计算结果与实验数据进行了比较.     

基于心磁信号的心脏电流偶极子阵列成像及相关性质的研究

超导量子干涉器（SQUID）能探测到微弱的心脏磁场信号. 通过对所得的心磁信号进行分析,可为许多心脏疾病的诊断提供依据. 利用心磁信号,采用极小范数最小二乘法（MNLS）对心脏的电流偶极子阵列进行重建,从而实现了对心脏内部等效电流源的成像. 在使用MNLS进行电流偶极子阵列反演重建的过程中,反演所需的心磁信号,分别由单电流偶极子和电流多极子作为激发源模拟得到,以及由SQUID实际测量得到. 同时,对不同心磁信号反演得到的电流偶极子的分布规律进行了分析. 此外,还给模拟的人体外心磁信号施加了均匀噪声和随机噪声,研究不同信噪比的均匀噪声和随机噪声对电流偶极子阵列重建的影响.     

基于心磁信号的心脏电流偶极子阵列成像及相关性质的研究

超导量子干涉器（SQUID）能探测到微弱的心脏磁场信号. 通过对所得的心磁信号进行分析,可为许多心脏疾病的诊断提供依据. 利用心磁信号,采用极小范数最小二乘法（MNLS）对心脏的电流偶极子阵列进行重建,从而实现了对心脏内部等效电流源的成像. 在使用MNLS进行电流偶极子阵列反演重建的过程中,反演所需的心磁信号,分别由单电流偶极子和电流多极子作为激发源模拟得到,以及由SQUID实际测量得到. 同时,对不同心磁信号反演得到的电流偶极子的分布规律进行了分析. 此外,还给模拟的人体外心磁信号施加了均匀噪声和随机噪声,研究不同信噪比的均匀噪声和随机噪声对电流偶极子阵列重建的影响. 关键词： 心磁信号 超导量子干涉器 电流偶极子阵列重建 极小范数最小二乘法     

射频SQUID心磁图数据自适应滤波研究

研究了滤除50Hz工频干扰的几种自适应算法，并应用于射频超导量子干涉仪（SQUID）心 磁图仪采集的心磁数据50Hz滤波中.对算法的性能进行了计算机仿真比较.结果表明，带50 Hz干扰的SQUID心磁信号通过自适应噪声对消法，干扰得到了很好的抑制. 关键词： SQUID 心磁图 自适应滤波 噪声消除     

实用高温超导MCG系统研究

本文研究了一种自建的低成本简易磁屏蔽室及其操控条件，提出了能被高温超导rf SQUID仪器所接受的简易磁屏蔽室，并且运用由该磁屏蔽室和rf SQUID梯度计所构成的组合系统测量了微弱的生物磁信号．研究结果表明，该磁屏蔽室能够有效降低电磁干扰，确保SQUID长时稳定工作，基于该磁屏蔽室的复合MCG测量系统具备捕捉微弱生物磁信号的能力，且所得信号具有可接受的信噪比．这将使得开发一种低造价的实用高温超导MCG测量系统成为现实．     

基于贪婪稀疏方法的心脏磁场源重构

心脏磁场源重构, 即通过人体胸腔表面的磁场阵列测量信号反演产生该磁场的电流源分布, 是一种无创地研究心脏电活动的方法. 本文用线性化方程描述测量磁场与心脏内部电流源的关系, 并通过一种贪婪优化的方法得到了源重构的稀疏解. 通过近似正交化过程和改变迭代算法中原子的选择方式, 降低了优化算法的复杂度, 可在保证源重构精度的情况下, 快速搜索源空间中强度比较大的位置. 文中通过一组正常人的心磁测量数据, 说明了源重构方法的有效性. 这组数据的研究结果表明, 强度大于65%的重构电流源的空间移动轨迹与心脏除极和复极电活动的传导过程基本符合. 其QRS 和ST-T 段的实测心磁图与重构电流源产生的磁场图的平均拟合优度分别为99.36%和99.78%. 关键词： 心磁图 逆问题 稀疏解 正交匹配追踪     

多腔体心脏磁场模型的研究与应用

利用核磁共振图像(MRI)中提取的人体和心脏边界,根据边界元方法(BEM)建立了一个考虑左、右心房和心室的多腔体心脏磁场模型.分析了用该模型得到的36通道心脏磁场数据和特定时刻的磁场图.并在此基础上,研究了完全性右束支传导阻滞(CRBBB)和完全性左束支传导阻滞(CLBBB)病人ST-T段的心脏电活动.结果显示,用移动单电流偶极子模拟的单束支电兴奋传导所产生的磁场图与用超导量子干涉器(SQUID)测量的CRBBB/CLBBB病人数据绘制的心脏复极时的心磁图(MCG)十分相似.结果表明,该多腔体心脏BEM模型可用于CLBBB/CRBBB病人心脏磁场逆问题的研究.此外,文中给出了两个评价指标:测量平面上多腔体与单腔体的心脏磁场强度极大值之比,以及两种模型的36个测量点上磁场强度均方根之比.分析表明,多腔体心脏模型更贴近人体心脏的实际情况.该模型中心脏组织电导率参数的取值,以及等效电流偶极子的位置和个数决定了磁场的强度和分布.     

利用单通道高温超导磁梯度计获取心磁地图

根据自己研制的单通道高温超导rfSQUID磁梯度计在人体胸前测得的高信噪比的心磁信号,通过线性插值和高阶拟合,获得了人体心脏的一系列时序等强磁场地图,为高温超导SQUID磁强计、梯度计的心磁测量用于心脏病早期诊断和病理研究的进一步开展提供了思路和方向.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.