Signal distortion in the electrocardiogram due to inadequate phase response

Electrocardiographic monitoring is used for arrhythmia analysis and for the detection of myocardial pathology, especially ischaemia and infarction, when waveform distortion must be minimized if reliable results are to be obtained. ST segment distortion has been noted to occur with ambulatory recorders and some electrocardiographs.     

Changes and additions to meteor-bust phase stability analyses

Limitations are discussed of continuous wave phase stability tests on meteor trail forward scatter channels. Results of pulse tests are given. Extensive phase stability tests results are presented. The stability and propagation delay times of signals that did not fit a classical meteor trail reflection model are shown.     

Stress analyses of high spatial resolution on TSV and BEoL structures

Knowledge and control of local stress development in Back-End-of-Line (BEoL) stacks and nearby Through Silicon Vias (TSVs) in advanced 3D integrated devices is a key to their thermo-mechanical reliability. The paper presents a combined simulation/measurement approach to evaluate stresses generated in the result of the TSV and BEoL stack manufacturing and 3D bonding processes. Stress measurement methods of high spatial resolution capability (microRaman and Focused Ion Beam (FIB) based stress release techniques) are used to obtain stress data from real components as manufactured. Finite Element Analysis (FEA) allows a more accurate interpretation of measurements results as well as a subsequent comprehensive analysis of failure behaviour. The paper gives an introduction to the applied local stress measurement on advanced multi-layer systems and 3D integration components referring to the state-of-art capabilities and limitations. The need of experimental stress data generation is illustrated on FEA examples. Illustration is given for FEA applications on 3D IC integration components currently lacking appropriate residual stress input for an assumed initial state.     

Temporal/spatial fiber-optic CDMA systems with post- and pre-optical amplification

We present a thorough analysis based on photon-counting techniques on temporal/spatial fiber-optic code-division multiple-access systems incorporating both post- and pre-optical amplifiers. In this analysis, we consider the effect of shot noise, thermal noise, and source extinction on system bit-error rate. Our results can be used to estimate the maximum tolerable amount of quantum fluctuations in the received signal.     

Temporal reshaping of optical pulses using quadratic spatialsoliton generation and spatial filtering

We perform a temporal reshaping of laser pulses by means of quadratic spatial soliton excitation combined with a spatial filtering of the output beam. We demonstrate that the device presents a behavior similar to the one of a saturable absorber, and numerically investigate the parameters giving optimum temporal filtering     

通信保障组织效能测度探索空间构造

针对通信保障组织效能测度缺少探索空间构造而导致探索因子分析混乱的问题,提出一种新的探索空间构造方法。对最底层探索因子的属性取预估值,之后离散化该层次,并对每个探索因子取多个水平值,反复迭代,逐层完成探索空间的构造。该方法能够迅速、自动生成探索空间,极大缩短了效能测度时间,同时提高了效能测度的准确性,为探索因子分析提供了清晰的思路。     

注入锁定铜蒸气激光器的时空、能量以及偏振特性

采用P分量的偏振光注入到平行平面腔的铜蒸气激光器中,结果表明,与未加注入光时的振荡器比较,注入锁定铜蒸气激光器的输出功率提高了43％,P分量的偏振度从0.30提高到0.78,脉宽由36ns加宽到48ns,输出光的发散角显著改善,由7.8mrad降到1.1mrad,与注入光束基本相同。     

Temporal and spatial sampling influence on the estimates ofsuperimposed narrowband signals: when less can mean more

This paper addresses the influence that the sampling locations have on the estimated frequencies of superimposed sinusoids. This problem has application in harmonic time-series analysis or direction-finding phased-array systems. Generalized mathematical bounds are developed in terms that are independent of the array locations and have an intuitively appealing physical interpretation. They establish the influence of the sampling locations on the variance of the frequency estimate and the limit at which two sources can be resolved using signal subspace estimators. For the resolution criteria, an expression dominated by the fourth central moment of the sensor locations expresses the resolving ability of the sensing array, irrespective of the array aperture or number of sensors. Increasing the fourth central moment increases an array's resolution ability. The commonly accepted notion that resolution necessarily depends on the array aperture is misleading and, indeed, that fewer snapshots from a reduced aperture array can outperform a larger array of more elements. For the estimator variance criteria, it is found that the product of the number of sensors and the second central moment (array variance) characterizes the estimator variance lower bound. The metrics developed demonstrate that the sampling topology is itself an important factor in determining the performance of the sampling system (and not the covariance lags sampled or the aperture spanned). Simulations are used to describe the results     

Al-Cu-Fe系初生准晶相凝固过程的电子显微分析

采用包括金相（OM）,粉末X射线衍射（XRD）,扫描电子显微镜（SEM）观察和透射电子显微（TEM）分析等方法,研究了铸态Al592.Cu36.8Fe3.0Si1.0合金（700℃保温2．5h后水淬）的显微组织及相组成。发现铸锭中存在4种相：准晶I相,τ3相（或φ相）,θ－Al2Cu相和η－AlCu相,凝固过程可描述为：初生晶是准晶Ⅰ相;在保温过程中发生包晶或共晶反应（L＋i→τ3(或φ）或L→τ3（或φ）＋i)形成的τ3相（或φ相）,呈微畴结构;而剩余液体水淬形成θ－Al2Cu相和η－AlCu 相。     

On the theory of the electrocardiogram

The biophysical basis for understanding the electrocardiogram is set forth. Bioelectric sources arise from electrical activity in the heart at the cellular level. The relation of these sources, which can be formally represented as impressed currents, to potentials involves solution of the volume conductor problem. This solution is based on Green's theorem. Sources are related to the transmembrane action potential through a bidomain model of heart muscle. Microscopic and macroscopic aspects of the bidomain model are developed. Various transformations of the source are considered, including multipoles, multiple dipoles, and replacement of the volume distribution with distributions on the heart surface. Time integrals of the waveform are related to excitation time and action potential duration. The theoretical results form the basis of a computer model of the electrocardiogram that relates skin potentials to the spatial and temporal distribution of action potentials in the heart     

Transient analysis of ferrite twin-toroid phase shifter by spatial network method

The transient characteristics of electromagnetic fields caused by changing the direction of remanent magnetisation in a twin-toroid phase shifter is simulated by the spatial network method. The time responses of the field and its instantaneous distributions are presented.<>     

Transfer of pump spatial variations to Stokes phase in Raman amplifiers

Many applications of forward Raman amplifiers require that transverse spatial amplitude and phase aberrations in the pump beam not be transferred to the phase of the amplified Stokes signal. Detailed one-dimensional depleted-pump calculation are given for two mechanisms that transfer pump aberrations to the Stokes phase. The first is multilongitudinal mode pump fluctuations that vary faster than the coherence time of the Raman transition. The second is saturated dispersion combined with a detuning either due to Raman operation off of line-center or due to the dynamic Stark effect.     

Mitigation of transmit correlation for TIMO spatial multiplexing through phase rotation

In MIMO wireless communications, spatial multiplexing can be employed to achieve a high data rate. However, its performance can be degraded by spatial correlation between the transmit antennae. Hence, a simple closed-form linear precoder is proposed to improve performance when two transmit antennae are exploited at the transmitter. The proposed precoder rotates the constellation by a certain phase angle, which can be easily obtained from the correlation matrix of the channel. The simulation results show that the proposed algorithm can achieve near- optimal performance with remarkably reduced computational complexity due to the closed-form solution.     

Polarization and spatial information recovery by modal dispersaland phase conjugation: properties and applications

Recent theoretical and experimental studies of polarization and spatial information recovery by modal dispersal and phase-conjugation are discussed. The fidelity of this phase-conjugation process as a function of input-beam launching conditions is discussed. Several new applications of the scheme which involve correction of nonreciprocal polarization distortions, correction of lossy amplitude distortions, phase-conjugate multimode fiber-optic interferometers and gyros, temporal data channeling between beams, and all-optical beam thresholding are described     

A measurement system and analysis procedure for determining the spatial phase structure function of ionospherically reflected waves

A 40-km sparse high-frequency (HF) receiving array is described which was used to measure the instantaneous phase at eight sites within the array of a pulsed 9-MHz transmission from Boulder, CO, to the Philadelphia, PA, area. The experimental program was designed to produce data on the statistical properties of the phase-front of a wave after passage through the ionosphere for the purpose of assessing the design problems of an array large enough to focus a 1-km cross-section beam at transoceanic distance (array size the order of 100 km). The problem of the effect of phase-front fluctuations due to turbulence induced scattering and internal ionospheric waves is formulated. The adaptive beamforming and scanning program of the Valley Forge Research Center, University of Pennsylvania, Philadelphia, is expected to yield solutions to this problem through self-cohering procedures. The nature of the desired measurements and a measuring system for accomplishing the task are also described.     

The evolutions of the spectrum and spatial coherence of laser radiation in resonators with hard apertures and phase modulation

The evolutions of the spectrum and spatial-coherence of light in optical resonators are investigated theoretically in detail on the basis of coherence theory in the space-frequency domain. The initial light in the resonator is assumed to be polychromatic and spatially incoherent with a certain spectral width. By considering the effects of the edge diffraction and phase modulation, the evolutions of the spectrum and coherence are clearly demonstrated for different types of resonator. The results show that the spectral evolution is affected not only by the g-factor of the resonator (the type of resonator), but also by the edge diffraction and phase modulation. We introduce a new parameter, called the global degree of spatial coherence, to characterize the spatial coherence on each mirror. The spatial-coherence evolution is also affected by g-factor of the resonator, edge diffraction, and phase modulation. The physical mechanism of these phenomena is explained and discussed.     

基于液晶空间光调制器相位调制的波面转换

本文介绍了一种基于液晶空间光调制器（LCSLM）相位调制特性的波面转换方法,可将入射光变换成任意波面。测量了液晶空间光调制器相位调制特性,得到相位和灰度的对应关系;分别以几何理论和G-S算法为基础计算出衍射光学元件（DOE）的表面相位分布;将DOE表面的相位分布转换为灰度分布显示在LCSLM上,使得LCSLM具有波面实时转换功能;并以高斯激光为入射光对其进行波面转换实验,实验结果证明了设计方法的准确性及可行性。     

Modelling of binary phase modulation in surface stabilized ferroelectric liquid crystal spatial light modulators

Modelling of binary phase modulation is required for optimal performance of ferroelectric liquid crystals (FLC) on silicon SLMs when used in coherent optical systems. This paper presents a modelling technique by which an HSpice model can be provided for characterization of phase modulation properties for designing FLC-on-silicon SLMs. The simulation and experimental measurements of phase modulation are described. For the theoretical model simulation, FLC parameter measurements are described. We experimentally verify the modelled prediction of phase modulation by investigating reflective FLC test cells. We have shown reasonable agreement within 9% between the measured and simulated values of phase modulation.     

Rejection of the maternal electrocardiogram in the electrohysterogram signal

The electrohysterogram (EHG) signal is mainly corrupted by the mother's electrocardiogram (ECG), which remains present despite analog filtering during acquisition. Wavelets are a powerful denoising tool and have already proved their efficiency on the EHG. In this paper, we propose a new method that employs the redundant wavelet packet transform. We first study wavelet packet coefficient histograms and propose an algorithm to automatically detect the histogram mode number. Using a new criterion, we compute a best basis adapted to the denoising. After EHG wavelet packet coefficient thresholding in the selected basis, the inverse transform is applied. The ECG seems to be very efficiently removed.