Spectral analysis of periodic fluctuations in electrocardiographicrepolarization

Repolarization alternans (RPA) indicates alternate-beat fluctuations in the temporal or spatial characteristics of the electrocardiogram (ECG) STU segment which may represent dispersion in repolarization. Spectral decomposition has revealed microvolt-level RPA which has been found to correlate with ventricular tachycardia (VT) and fibrillation, and is increasingly being used for clinical risk stratification. However, while interruptions in periodicity are known to affect spectral decomposition, their quantitative impact on RPA and its clinical utility have been poorly described. The authors therefore studied the effect of variable alignment, extrasystoles, dissimilar beats and beat exclusion on RPA magnitude in simulations and on the sensitivity and specificity of RPA for VT in a pilot clinical study, RPA magnitude was exquisitely sensitive to QRS alignment such that ±1 ms random beat misalignment reduced it by 68% in simulations. Correspondingly, suboptimal QRS alignment in clinical ECG's caused the sensitivity of RPA for inducible VT to fall from 93% to as low as 63%; while JT alignment was also less effective for RPA recovery. As an experiment in minimizing morphometric irregularities in clinical ECG's, the authors found that RPA magnitude actually fell when replacing either measurably dissimilar or ectopic beats with more representative beats. In addition, inserting or deleting beats also reduced RPA magnitude in clinical sequences and simulations. These statistical analyses suggest that the precision of beat alignment and interruptions to ECG periodicity, which may occur physiologically, may greatly reduce the clinical utility of RPA for VT. Dynamic alterations in RPA in response to sequence irregularities require further study before RPA may be optimally applied to screen for ventricular arrhythmias     

Endocardial detection of repolarization alternans

Repolarization alternans (RPA) is prognostic of sudden cardiac death and is thought to be mechanistically linked to the initiation of ventricular tachyarrhythmias. Thus, implantable cardiac device detection of RPA may be therapeutically valuable. Because alternans detection is currently limited to surface electrocardiograms, we investigated whether RPA could be measured using a single right-ventricular endocardial lead in humans. Such a location was chosen because it is consistent with the requirements for long-term implantable-device implementation. During diagnostic electrophysiological testing, 28 patients (23 male, 5 female; 61 +/- 15 years) were evaluated for surface T-wave alternans (TWA; the current "gold standard" for RPA detection) and endocardial RPA during 5 min of 550-ms right-atrial pacing. Power spectral analysis indicated that 11/28 patients had both surface TWA and endocardial RPA, 9/28 patients had neither, and 8/28 patients had discordant results (71% concordance; p = 0.02). Importantly, unlike surface TWA, endocardial RPA was detectable on a beat-to-beat basis. Given the putative mechanistic link between RPA and ventricular arrhythmias, beat-to-beat endocardial RPA detection might be of diagnostic or therapeutic utility.     

Detection of repolarization alternans with an implantable cardioverter defibrillator lead in a porcine model

Mechanistic links have been suggested between repolarization alternans (RPA) and the onset of ventricular tachycardia (VT) and/or fibrillation. Endocardial detection of RPA may, therefore, be an important step in future device-based treatments of arrhythmias. Here, we investigate if RPA could be detected during acute ischemia using an implantable cardioverter defibrillator (ICD) lead (tip to distal coil) located in the right ventricular apex. In 18 pigs, the right coronary (n = 10) or left anterior descending coronary (n = 8) artery was occluded for 10 min using a balloon catheter, followed by reperfusion for 30 min, and re-occlusion for 30 min. RPA magnitude, computed using the modified moving average (MMA) method, showed a sharp increase in all 18 animals, from a mean baseline level of 1.9 +/- 1.3 mV to 3.0 +/- 1.3 mV during first occlusion (p < 0.001). RPA magnitude showed a prominent increase in 10 animals during re-occlusion, from a mean baseline level of 1.7 +/- 1.0 mV to 3.3 +/- 1.5 mV (p < 0.001). The protocol was terminated during the first two stages of occlusion and reperfusion for the remaining 8 animals due to the occurrence of ventricular fibrillation (VF). These results confirm that RPA increases under ischemic conditions and that it is possible to detect and track RPA dynamics with an ICD lead that is positioned in a clinically realistic location. Such an approach may be useful in formulating improved arrhythmia detection and control algorithms.     

RPA: a flexible scheduling algorithm for input buffered switches

This paper presents and evaluates a quasi-optimal scheduling algorithm for input buffered cell-based switches, named reservation with preemption and acknowledgment (RPA). RPA is based on reservation rounds where the switch input ports indicate their most urgent data transfer needs, possibly overwriting less urgent requests by other input ports, and an acknowledgment round to allow input ports to determine what data they can actually transfer toward the desired switch output port. RPA must be executed during every cell time to determine which cells can be transferred during the following cell time. RPA is shown to be as simple as the simplest proposals of input queuing scheduling, efficient in the sense that no admissible traffic pattern was found under which RPA shows throughput limitations, and flexible, allowing the support of packet-mode operations and different traffic classes with either strict priority discipline or bandwidth guarantee requirements. The effectiveness of RPA is assessed with detailed simulations in uniform as well as unbalanced traffic conditions and its performance is compared with output queuing switches and the optimal maximum weighted matching (MWM) algorithm for input-buffered switches. A bound on the performance difference between the heuristic weight matching adopted in RPA and MWM is analytically computed     

The recursive pyramid algorithm for the discrete wavelet transform

The recursive pyramid algorithm (RPA) is a reformulation of the classical pyramid algorithm (PA) for computing the discrete wavelet transform (DWT). The RPA computes the N-point DWT in real time (running DWT) using just L(log N-1) words of storage, as compared with O(N) words required by the PA. L is the length of the wavelet filter. The RPA is combined with the short-length FIR filter algorithms to reduce the number of multiplications and additions     

The Plasma Instrument for AMPTE IRM

The AMPTE IRM plasma instrument package consists of three sensors. Two of them measure complete 3-D velocity-distribution functions of ions and electrons every spacecraft revolution (i.e., 4.35 s). The third sensor is a retarding potential analyzer (RPA) for low-energy electron measurements. The 3-D measurements consist of countrates at 30 energies and 128 angles evenly distributed over the 4xr solid-angle sphere. The energy range is 15 eV-30 keV for electrons and 20 eV/q-40 keV/q for ions. The RPA extends the electron measurements to lower energies. Three microcomputers within the experinent perform extensive on-board data-processing functions. Two of them compute the moments (density, velocity, temperature tensor, and heat flux vector) of the distribution functions of ions and electrons in real time. The third compresses the RPA data and computes an indication for the spacecraft potential.     

智能语音交互与RPA技术在网络运维监控中的应用与研究

目前,各网络运营商在网络监控维护领域,仍有很多工作依靠人工完成,如动环指标查询、传输故障恢复确认等,任务简单频次高,且人工成本较高。随着AI人工智能技术日趋成熟,将智能语音交互与RPA技术相结合,探索其在网络运维监控方面的应用成为其未来发展趋势。其整体依托于智能语音识别、语音合成、语义理解、RPA自动化等AI能力,通过对运维人员来电意图的识别和分析,将查询意图转化为RPA可执行指令,最后由RPA无侵入式的模式自动完成具体任务。     

基于RPA的智慧办公协同平台框架设计研究

随着数字经济的快速发展，人工智能的浪潮掀起，协同办公系统带来的自动化受到了世界各国的普遍重视，企业对在线办公提出了便捷、效率、安全等新需求。文中设计并实现了一个基于RPA的协同智慧办公平台框架，探讨了RPA技术对协同管理的支撑，通过挖掘企业日常办公系统中典型的重复劳动场景，将自动化机器人作为企业的虚拟劳动力，开展RPA在典型场景中的应用，从而有效提高了在线办公的质量。文中还分析了RPA在平台框架设计与应用中的难点问题及应用优势，希望能为推进协同办公智能化、信息化建设提供一定的参考。     

Submillimeter wave communication versus millimeter wave communication

This paper studies the performance of a submillimeter wave antenna operating between frequencies 0.1 THz and 10 THz with a 4-cyano-4-pentylbiphenyl [5CB] substrate. Since the size and shape of the antenna impact its gain/directivity, resonant frequency, bandwidth, and efficiency, the two antenna types considered in this paper are: (a) Rectangular Patch Antenna (RPA), and (b) Cylindrical Dielectric Resonator Antenna (CDRA). Here a submillimeter wave antenna is compared with a millimeter wave (a few GHz to 100 GHz) antenna. These popular mm-wave antennas are chosen for the submillimeter wave antenna in order to understand changes in their performance as the result of changes in their geometrical shape. FEldberechnung bei Korpern mit beliebiger Oberflache (FEKO) software is used for the design and calculation of the Three-Dimensional (3D) ElectroMagnetic (EM) patterns. This paper also concentrates on the design and analysis of a massive submillimeter wave Multiple-Input Multiple-Output (MIMO) (8 by 8) RPA and CDRA.     

交换关联对半导体超晶格等离激元色散关系的影响

本文用优化的局域密度泛函近似所给出的介电矩阵计算了GaAs-Al_xGa_(1-x)As超晶格中等离激元色散关系,得到了对无规相近似的重要修正.     

The dielectric response function of systems with reduced dimensionality

The dielectric response function of the electron gas in a system with reduced dimensionality within the RPA and the Hubbard approximation, are given by using a linear response theory in which the conditions of a multisubband spectrum and finite spatial localization of the wavefunction in one, two or three dimensions, proper of such systems, are taken into account. The final expressions for the dielectric response function is given in each case and its general properties are analyzed. These results are applied to the calculations of the intrasubband and the intersubband polarizabilities in a quantum well (QW) and a quantum well wire (QWW). For the QW, the analysis of plasmons in a semiconductor based and a metal-based QW are given and compared with other theoretical calculations. In the metallic QW, exchange provokes the stabilization of the modes with respect to the RPA plasmons. For the QWW, the exchange modifies the polarizability in both the intrasubband and the intersubband transitions. The main arguments to perform the analysis to achieve the dielectric response function for the quantum dot (QD) in the above both approximations and for the Singwi-Tosi-Lang-Sjölander (STLS) approximation (which takes account of exchange and correlation) for the QD, the QW and the QWW are outlined.     

基于RCSIMD的8192点FFT并行算法研究

文中提出了一种基于RCSIMD体系结构的8192点FFT的并行算法.该并行算法将8192数据分成连续64块,每块128个连续数据(存储在可重构处理元的局部存储器),采用RCSIMD可重构处理阵列完成块倒位序变换,块内只进行逻辑上的倒位序变换(倒位序过程隐含在配置数据中).这种数据存储和倒位序处理方法可以充分利用处理阵列通信网络和处理单元的能力.     

离散小波变换的VLSI实现

离散小波变换已广泛应用于信号处理中。然而,实时小波变换需要大量运算,因此,专用小波变换芯片的设计已成为信号处理中的关键技术。文章提出了一种小波变换递归金字塔算法的VLSI结构,采用一组输入延迟单元和一个控制单元,用一组并行滤波器完成了小波变换。编写了相应的Verilog HDL模块,并进行了仿真和逻辑综合。     

A Programmable Parallel VLSI Architecture for 2-D Discrete Wavelet Transform

Many VLSI architectures for computing the discrete wavelet transform (DWT) were presented, but the parallel input data sequence and the programmability of the 2-D DWT were rarely mentioned. In this paper, we present a parallel-processing VLSI architecture to compute the programmable 2-D DWT, including various wavelet filter lengths and various wavelet transform levels. The proposed architecture is very regular and easy for extension. To eliminate high frequency components, the pixel values outside the boundary of the image are mirror-extended as the symmetric wavelet transform (SWT) and the mirror-extension is realized via the routing network. Owing to the property of the parallel processing, we adopt the row-based recursive pyramid algorithm (RPA), similar to 1-D RPA, as the data scheduling. This design has been implemented and fabricated in a 0.35 m 1P4M CMOS technology and the working frequency is 50 MHz. The chip size is about 5200 m × 2500 m. For a 256 × 256 image, the chip can perform 30 frames per second with the filter length varying from 2 to 20 and with various levels. The proposed architecture is suitable for real-time applications such as JPEG 2000.     

Exchange effects in the screening of a phonon mode in a semiconductor quantum well

We study the screening of the first two polar optical phonon modes in a QW using the rigid wall case. The screened potential was calculated by employing nonlocal dielectric functions obtained in multisubband extensions of (a) the RPA and (b) the Hubbard (H) approximations. The purpose of the calculations is to study the influence of the design parameters, such as the well width and the change in carrier population, in the above mentioned different approximations. The QW is modelled by an infinite potential well and also by the selfconsistent Hartree approximation to consider the modulation doped QW. The main design parameter is found to be the carrier population. Furthermore, it is found that the selfconsistent re-shaping of the electronic potential well—and hence the carrier distribution—affects the resulting screened potential significantly.     

Pioneer Venus Orbiter Planar Retarding Potential Analyzer Plasma Experiment

The retarding potential analyzer (RPA) on the Pioneer Venus Orbiter Mission measures most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. Several functions not previously used in RPA's were developed and incorporated into this instrument to accomplish these measurements on a spinning spacecraft with a small bit rate. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection.     

Ant Colony Optimization Based Sub-channel Allocation Algorithm for Small Cell HetNets

Two-tier heterogeneous networks (HetNets) composed of a conventional macrocellular network and small cell networks (SCNs) have been proposed in the literature with the aim to extend indoor coverage and realize efficient radio resource usage. As SCN shares the same frequency band with the underlying macrocell, the cross tier interference needs to be mitigated since the inter-SCN and cross tier interference at the SCN boundary may result in undesirable network performance degradation. In this paper, we propose an intelligent physical resource block (PRB) allocation as a solution to mitigate the downlink intra-SCN interference as well as the inter-tier interference in OFDM-based systems. The allocation of the PRBs to the network users is formulated as a graph coloring problem, and solved using an ant colony optimization (ACO)-based approach. Simulation results are provided, showing that our ACO-based algorithm outperforms the Received Power-based Allocation (RPA) and Received SINR-based Allocation (RSA) algorithms in terms of average SINR experienced by network users, outage probability, and number of required PRBs.     

A Distributed and Collaborative Intrusion Detection Architecture for Wireless Mesh Networks

Wireless Mesh Network (WMN) is an emerging heterogeneous network architecture that is growing in importance among traditional wireless communication systems as a cost-effective way of providing Internet services. However, WMNs are particularly vulnerable to malicious nodes given their inherent attributes such as decentralized infrastructure and high dependence of node cooperation. We then propose a distributed and Collaborative Intrusion Detection System (CIDS) architecture for detecting insider attacks at real-time, which comprises: i) a Routing Protocol Analyzer (RPA) to analyze the collected routing traffic and generate respective Routing Events; ii) a Distributed Intrusion Detection Engine (DIDE) that treats the Routing Events by applying Routing Constraints and calculate related Misbehaving Metrics; iii) a Cooperative Consensus Mechanism (CCM) to check the Misbehaving Metrics using a proposed threshold scheme and to track down the source of intrusion. The entire CIDS solution is implemented in a virtualized mesh network platform. The experimental results show the proposed CIDS architecture efficiently detects message fabrication attacks with good precision and low resource consumption.     

An integrated quasi-planar leaky-wave antenna

A new quasi-planar leaky-wave antenna is presented. It consists of microstrip line on one side of the substrate and uniplanar circuit on the other side placed in a partially opened waveguide. The leakage is produced by the excitation of the first higher order (odd) microstrip mode coupled electromagnetically through a slotline on the opposite side of the substrate. Theoretic results based on rigorous Green's impedance integral equation method show that the new microstrip-slotline-coupled leaky-wave antenna has a broadband tuning range via structure parameters and is insensitive to the microstrip line width variation. Measured relative power absorbed (RPA) results indicate that the useful frequency bandwidth agrees with that predicted by rigorous field theory. The measured antenna radiation patterns also agree very well with the approximate theoretic computations. The theory and experiments show that the proposed leaky-wave antenna can interface to feeding structure easily and directly. The new antenna may become a good candidate for microwave and millimeter-wave integrated antenna design