Correction to “regional head tissue conductivity estimationfor improved EEG analysis”

Two equations in the Appendix of the title paper (see T.C. Ferree et al., ibid., vol. 47, p. 1584-92, 2000) included typographical errors. They should be replaced by the corrected equations given here. The errors were merely typographical. The authors have verified that the equations used to generate the numerical results in the original paper were implemented correctly. Consequently, the conclusions of the original paper are still equally valid. These corrections affect only readers wishing to reproduce the authors' results. The authors sincerely thank A. Liston for pointing out the errors. They apologize for any inconvenience     

Sample-based classification procedures related to empiric distributions

We present new classes of binary codes that are constructed on the basis of concatenated codes and product codes. We discuss the random-error-correction capabilities of these codes. Some examples of the codes for the correction of random errors are given which have at least as many codewords as the best codes previously known (to the authors) with the same minimum distance and same number of check symbols. The burst-error-correction capabilities of the codes are also discussed. Several examples of the codes for the correction of both random errors and burst errors are given. A decoding algorithm for the codes is also described.     

New classes of binary codes constructed on the basis of concatenated codes and product codes

We present new classes of binary codes that are constructed on the basis of concatenated codes and product codes. We discuss the random-error-correction capabilities of these codes. Some examples of the codes for the correction of random errors are given which have at least as many codewords as the best codes previously known (to the authors) with the same minimum distance and same number of check symbols. The burst-error-correction capabilities of the codes are also discussed. Several examples of the codes for the correction of both random errors and burst errors are given. A decoding algorithm for the codes is also described.     

Reconsideration of "A Fast Computational Algorithm for the Discrete Cosine Transform"

Some corrections are made for the original paper "A fast computational algorithm for the discrete cosine transform," 1 which contains some errors of indexes and of multiplication factors.     

Analysis of Digital Errors in Nonlinear PCM Systems

The effect of digital errors in linear pulse code modulation (PCM) systems has been considered by several authors for channels with independent errors. In this paper we present a general approach of analyzing digital errors in linear and nonlinear PCM systems with arbitrary channels. The examples given in this paper cover the different standard nonlinear PCM systems and independent channel errors. The technique used for the analysis leads to the conclusion that there are PCM codes less sensitive to digital errors than the standard binary folded PCM code. An example of such a PCM code is given in this paper.     

Comments on “A one volt four-quadrant analog current modemultiplier cell” [with reply]

For original paper see C. Chan, H. Ling and O. Choy, ibid., vol.30, no.9, pp.1018-19 (1995). The goal of the original paper was to develop a novel FM demodulator based on a Gilbert multiplier that can operate with a single 1.2 V battery. In this Comment the author suggests that the original paper contained some errors and that the cell developed was not at all novel and is actually very well known. A reply by the original authors is included     

ON MARKOV RANDOM FIELD MODELS FOR SEGMENTATION OF NOISY IMAGES

Markov random field(MRF) models for segmentation of noisy images are discussed. According to the maximum a posteriori criterion, a configuration of an image field is regarded as an optimal estimate of the original scene when its energy is minimized. However, the minimum energy configuration does not correspond to the scene on edges of a given image, which results in errors of segmentation. Improvements of the model are made and a relaxation algorithm based on the improved model is presented using the edge information obtained by a coarse-to-fine procedure. Some examples are presented to illustrate the applicability of the algorithm to segmentation of noisy images.     

Comments on “Improvement in calculation of some surfaceintegrals: application to junction characterization in cavity filterdesign” [and reply]

The original authors claim to have developed a rigorous method allowing the reduction of a surface integral to a contour integral with application to mode-matching analysis of waveguide junctions. The authors have applied the method to analyze the transition from circular waveguide to rectangular waveguide. This same method has been previously derived in its general form. Some preliminary results on the discontinuity between ridged and rectangular waveguide have been presented. The only original contribution recognized is therefore the application to the analysis of coupling between circular cavities through rectangular irises. The original authors give their reply     

LDPC码的不可检测译码错误分析

纠错性能良好的LDPC码同时具有良好的检错性能。本文介绍了LDPC码的不可检测译码错误概率上限，讨论了不可检测译码错误与码参数的关系，提出对于特定构造的LDPC码，在基于AWGN信道传输和置信传播迭代译码时，可以应用迭代过程中连续消息的密度进化来分析不可检测译码错误概率，并给出了一些短码长高码率情况下的仿真结果。     

Technologies for local-access fibering

The authors describe passive optical networks (PON), optical wavelength allocation, device and system technologies. Some examples of PON systems are given including SDM, WDM, FDM, and TCM. The authors go on to discuss optical modules LSI and optical amplifiers. The paper concludes with a discussion of upgrading PONs     

一种基于微分思想的图象变形算法研究与实现

图象变形是图象处理中的基本问题,不仅要求图象变形效果好,而且要求变形算法效率高.目前已有的变形算法,大多采用基于象素点的填充方法,这种方法有比较明显的缺点:(1)当变形的图象区域是一个非规则区域时,图象变形处理所花费的时间增加,即算法的时间复杂度加大,效率低;(2)在对象素点作映射变换时,可能出现变形后的图象区域中一个象素点对应变形前的图象区域中多个象素点,因此造成取舍困难,甚至造成取舍错误.为解决这一问题,本文提出了一种基于微分思想的图象变形算法,该算法先将复杂的变形区域划分为一系列子区域,再将每个子区域划分为多个小矩形,将对应的小矩形按照标准矩形填充算法进行快速填充,由此实现图象变形.实验结果表明,该算法实现简单,计算速度快,填充效果好,并已成功地应用于笔者开发的基于真实照片的人脸整形与美容图象处理系统中.     

Use of cancellation techniques in the measurement of atmospheric crosspolarisation

Some of the errors implicit in atmospheric crosspolarisation-measurement systems are given, together with their limitations on the accuracy of the resultant measurements. A cancellation technique is described that allows the `clear-weather? performance of measurement links to be considerably improved. The limitations due to rainfall of such a cancellation system on the accuracy of crosspolarisation measurements are investigated, and the system is shown to be preferable to a conventional one.     

Comments on `The impact of NRZ data asymmetry on the performance ofa space telemetry system' by T.M. Nguyen

The commenters point out an error in the continuous power density spectrum given by the terms indicated in the above-titled paper (see ibid., vol.33, no.4, p.343-50, 1991). The continuous component of the spectrum computed directly from an equation given in the paper is shown and differs substantially from that shown in the original figure. Some repercussions as regards other results in the paper are indicated     

Comment on "Annealing behavior of a proton irradiated Al/sub x/Ga/sub 1-x/N/GaN high electron mobility transistors grown by MBE"

For original paper see S.J.Cai et al., ibid., vol.47, p.304-307 (2000). The paper by Cai et al. is the first article referring to radiation effects of Al/sub x/Ga/sub 1-x/N/GaN high electron mobility transistors published in this journal. In the paper, authors made use of the shifts of the decomposed three GaN Raman phonon modes E2 to analyze and explain the irradiation effects on GaN. However, we feel that incorrect assignment has been made to the decomposed E2 peaks in GaN and there are obvious errors in citing literature regarding Raman scattering shift rules that warrant comments.     

基于FEC的误插入控制

本文讨论了采用前向差错控制（ＰＥＣ）技术进行ＡＴＭ网上信元误插入控制的可能性，重点研究了ＡＡＬ１用于信元丢失和比特误码控制的编码方法。提出并分析了四种误插入控制算法。指出传统的ＲＳ码很难在误插入控制中充分发挥码的能力，因此建议了一类略为修正的首尾非零非线性码。研究表明这类码能充分发挥码的潜力，与原始ＲＳ码比较，有好得多的误插入控制性能。     

利用IDFT技术实现天线的时域近场测量

本文提出了一种利用离散付立叶反变换(IDFT)技术完成天线的时域近场测量的方法.首先依据付立叶变换理论论证了这种方法的可行性,用典型算例证明了该方法的有效性和正确性,同时对实现这种测试方法可能引入的误差进行了分析,随后提出了应用该方法完成测试时关键技术参数确定的原则,讨论了用该方法测试所获得的实验结果,得出了结论.     

Performance of a frequency-hopped differentially modulated spread-spectrum receiver in a Rayleigh fading channel

The performance of a spread-spectrum receiver previously described by the authors is analyzed in detail. Performance curves are given for a wide range of mobile radio channel conditions, including multipath distortion and correlated fading. The use of optimal filters to combat the former and space diversity to combat the latter are investigated. Some errors in the authors' earlier papers are corrected. The form of space diversity suggested has the unusual feature that it can be employed at the fixed station site only and provide diversity in both communication paths, i.e., to and from the mobile. Degradation due to fading and other aberrations is shown to be in the range 3-6 dB for typical mobile channel conditions. In a nonfading channel the receiver is suboptimum by about 3 dB.     

任意形状散射体模型的建立和修正

文中提供了一种对任意形状导体散射体的原始数据进行分析修正,并最终形成可计算模型的方法。散射体的几何数据,通常包括重叠、空洞和相交等错误,它们必须在计算前予以修正。该文在AutoCAD环境,及其二次开发工具支持下,完成了自动检测,半自动地数据修正,最终得到了可计算的表面或实体模型。给出了计算实例以说明该方法的有效性。     

基于波束输出的高分辨定向方法及性能分析

本文提出一种基于波束输出的高分辨定向方法。这种方法利用子阵形成子波束,并把该子阵看做为一个等效阵元。然后对多个等效阵元构成的新阵列利用目前典型的高分辨算法进行定向。我们对均匀线列阵进行了计算机仿真实验和水池高分辨阵列处理实验,研究结果表明,这样做可以获得性能上的较大提高。一方面,可提高原高分辨定向算法的估计精度、分辨概率并降低运算时间;另一方面,由于各个等效阵元的输出是由多个实际阵元输出加权平均得来的,因此基于等效阵元构成阵列的高分辨定向算法对各种阵列误差(如阵元位置误差、阵元指向性的不一致等)变得不十分敏感,从而有利于抑制阵列误差对高分辨定向算法的影响,对工程应用具有较强的适应性。文中对各种情况进行了较详细的统计性能分析与比较。