Comments on `A stable procedure to calculate the transientscattering by conducting surfaces of arbitrary shape' [and reply]

Lengthy comments are offered on some remarks made in the paper by D.A. Vechinski and S.M. Rao (see ibid., vol.40, no.6, p.661-5, June 1992) regarding the solution procedure described by B.P. Rynne (1991). Vechinski and Rao offer arguments in rebuttal     

How fast can radio messages be transmitted?

In 1991, experiments were reported by Ishii and Giakos which led the authors of those papers to the conclusion that radio messages can be transmitted faster than light. Such an idea is an apparent contradiction to the theory of relativity, and has provoked rebuttals, e.g. from Tichy-Racs (1992) and Marks (1992). The experimental evidence which followed, showed that an RF-pulse signal cannot travel faster than light. A paper by Stephan (see IEEE Antennas and Propagation Magazine, vol.35, no.3, p.13, 1993) has revealed that the controversy has not yet been resolved. This article should clarify how a misinterpretation of the observation could be understood as transmission faster than light     

Nonlinear differential equation for the reflection coefficient of apure conducting medium and its novel inverse scattering solution

A nonlinear differential equation for the reflection coefficient of a pure conducting medium is derived by using a microwave networking technique, which can be approximately solved by a nonlinear renormalization method. From the renormalization solution of the reflection coefficient, a novel inverse scattering formula to the conductivity profile is further investigated in the closed form. Reconstruction examples show that the novel formula is more accurate than the results in D.B. Ge et al. (1991) and T.J. Cui et al. (1992)     

A note on “The Backus-Gilbert inversion method and theprocessing of sampled data”

We show a sequence of interpolation formulas for the Backus-Gilbert (BG), published in 1967, method with δ-function kernels and penalty functions J(t, t')=(t-t')^2k for integers X>0. We show that the interpolation in the limit sense of X→∞ is the Haar representation The interpolation formulas are generalizations of the one obtained by Caccin et al.(see ibid., vol.40, no.11, p.2823, 1992). We investigate the possibility of the BG method with δ-function kernels so that it is exactly the same as the Shannon sampling formula. We also examined the possibility of the exact reconstruction by the BG method for bandlimited signals     

The use of ERS-1 SAR data in snow melt monitoring

ERS-1 SAR data, airborne data and in situ snow data were acquired for the Sodankyla test site in northern Finland for the winters of 1991-1992 and 1992-1993. The test area consists of sparsely forested areas (pine, mixed forests, and mires) and open areas (bogs, lakes, clear-cut areas, and urban area). A set of multitemporal ERS-1 SAR images covering the two winters have been analyzed and the results have been compared with in situ surveys and a digital land-use map. The results indicate that even in the presence of forest canopies (1) wet snow can be distinguished from other soil/snow conditions (dry snow and bare ground), and (2) snow melt maps can be derived from SAR images. Snow-melt maps indicate areas fully covered with wet snow, partly melted areas and snow-free areas     

Comments on “Shielding effectiveness of conductivepolymers”

The authors comment that K. Naishadham (see ibid., vol.34, no.1, p.47-50, 1992) calculated the plane-wave shielding effectiveness of conductive polymers as a function of frequency. As indicated, a comparison to the measured result of the DC conductivity indicates that the microwave conductivity at room temperature is within a small percentage of the DC result, and therefore can be used for a wide frequency range. The conductivity of the polymers is given by σ=2πf₀ϵ₀ϵ" and is assumed invariant for all frequencies. Based on the invariability of polymers' conductivity for all frequencies, they calculated the shielding effectiveness of the polymers. Discrepancies are found by comparing these figures to those of Naishadham. It is concluded that shielding effectiveness calculated by Naishadham was done under the assumption of frequency-invariant ϵ" instead of σ     

Technology 1993-transportation

Developments and events during 1992 are reviewed. The drive toward intelligent vehicle-highway systems was given an extra push by the Intermodal Surface Transportation and Efficiency Act, which was signed into US law in December 1991. The demand for zero emissions has revived work on electric vehicles. In spite of high installation costs, high-speed rail projects moved ahead, and nonstop air-traffic communications is planned. Japan tested a ship propelled by magnetohydrodynamic (MHD) thrusters akin to the `caterpillar drive' used by the superquiet submarine in The Hunt For Red October     

Comments on “Multiphase systolic algorithms for spectraldecomposition” [and reply]

Comments that the paper by Liu and Yao (see ibid., vol.40, no.1, p.190, 1992) presented an efficient algorithm for spectral decomposition, but the parallel algorithm and architecture for the Hessenberg reduction has a problem. The matrix obtained from the unitary similarity transformation is not necessarily a Hessenberg matrix. The authors reply that the Hessenberg reduction described is not in the Hessenberg form. Only the first column is in its proper form. There are many ways to overcome such a problem. One simple way is to use the multiphase rectangular systolic array     

Comments on “Statistical and spatial properties of forestclutter measured with polarimetric synthetic aperture radar”

For original paper see ibid., vol.30, no.3, p.578-88 (1992). Sheen and Johnston have derived a theoretical expression for the intensity autocorrelation function of a synthetic aperture radar (SAR) image based on the product model for SAR clutter. This derivation is valid under the assumption that the instrument function width is narrow relative to the width of the texture autocorrelation function. This communication draws attention to a more general derivation of the intensity autocorrelation function, given by Oliver, which does not require this assumption     

Reply to “Comments on the optimum CMOS tapered bufferproblem”

For original article see ibid., vol 27, p. 118-9 (1992). For comments on original paper see ibid., vol29, no. 2, p155-8 (1994). The optimum tapered buffer has been extensively discussed in the literature. In this correspondence a general model is derived and it is shown that previously reported models are specific cases of the general model presented here     

Recent propagation studies in Japan

Reviews activities in the field of propagation research, in the 1990s, in Japan. The authors focus only on propagation studies related to radio communications; activities in the field of remote sensing are outside the scope of this review. Since Kagoshima and Shiokawa (1992) included a short review of research activities in this field, in the period from 1989 to 1991, the emphasis of the present review is placed on activities after this period. The list of references consists of only papers written in English, which have appeared in international journals or published proceedings of international conferences. Reflecting the activities of various fields of propagation research in Japan, two-thirds of the review is devoted to propagation studies related to mobile communications, including land-mobile, mobile-satellite, and indoor communications. The rest of the review covers other basic studies, related to propagation through the atmosphere and precipitation     

MPEG: a technological basis for multimedia applications

The Moving Picture Experts Group was established in 1988 in the framework of the Joint ISO/IEC Technical Committee (JTC 1) on Information Technology. They were given the mandate to develop standards for coded representation of moving pictures, associated audio, and their combination when used for storage and retrieval on digital storage media (DSM). In April 1990 they became Working Group 11 of JTC 1/SC 2, then in November 1991, WG 11 of JTC 1/SC 29. The three original work items of the group-coding up to 1.5, 10, and 40 Mbps-were nicknamed MPEG-1, -2 and -3, respectively. The group dropped the MPEG3 work item in July 1992 when it became apparent that the functionalities supported by the MPEG-2 requirements made it redundant. The current MPEG-4 work item, first proposed in May 1991 and approved in July 1993, targets audiovisual coding at very low bit-rates     

Piezoelectric actuated multiple channels optical switch

In this article, a novel multi-channel optical switch that is composed of a Y-shaped micromirror with two symmetrically reflective surfaces, a fixed pivot for mounting the micromirror, and a piezoelectric actuator to actuate the micromirror, is proposed. Working principle of this novel device is that the switching displacement of the reflective beam of light can be linearly controlled by the displacement of the piezoelectric actuator. Accordingly, the 1×N switching task can be easily achieved. To realize the proposed concept, UV-LIGA technique was implemented to fabricate the components. Multiple-switching concept was demonstrated through experiments. Efficiency of the proposed optical switch was investigated by computer simulations. Optical efficiency of the proposed device can be optimized if its dimensions are adequately designed. Gou-Jen Wang received the B.S. degree on 1981 from National Taiwan University and the M.S. and Ph.D. degrees on 1986 and 1991 from the University of California, Los Angeles, all in Mechanical Engineering. Following graduation, he joined the Dowty Aerospace Los Angeles as a system engineer from 1991 to 1992. Dr. Wang joined the Mechanical Engineering Department at the National Chung-Hsing University, Taiwan on 1992 as an Associate Professor and has become a Professor on 1999. Since 2003, he has been the Division Director of Curriculum of the Center of Nanoscience and Nanotechnology. His research interests are MEMS, Biomedical Micro/Nano devices, Nano fabrication. Hong-Ru Liu received the B.S. and M.S. degrees on 2002 and 2004 from the National Chung-Hsing University, both in Mechanical Engineering.     

Comments on “The Cramer-Rao lower bounds for signals withconstant amplitude and polynomial phase”

For original paper see IEEE Trans. Signal Processing, vol.39, p.749-52 (March 1991). Different expressions for the Cramer-Rao lower bounds (CRLBs) of constant amplitude polynomial phase signals embedded in white Gaussian noise appear in the literature. The present paper revisits the derivation of the bounds reported by Peleg and Porat (1991) and indicates that the resulting expressions depend on the interval over which the signal is defined. The proper choice of the interval is the one that centers the signal around zero and results in the minimum lower bounds     

红外热像图在阴囊部疾病诊断上的应用（附45例小结）

应用ＨＷＸ型红外热像仪对４２例阴囊内疾病及３例阴茎病施行热图检查，诊断符合率达到８６％。表明热图诊断对鉴别阴囊良、恶性病变，精索静脉曲张及不育症等有一定参考价值。     

Implications of mobile cellular CDMA

The results of four extensive field tests of code division multiple access (CDMA) cellular technology performed between November 1991 and September 1992 are presented. These tests include: validation system field tests conducted in San Diego, California, operating over five cell sites, comprising a total of eight sectors, and involving up to 70 mobile units, plus simulated other user and other base station interference; tests in Munster, Germany, the configuration of which consisted of two cell sites and two mobiles plus 20 simulated other users operating in the 1700-MHz band; tests in Geneva, Switzerland, the same as in Munster, but operated in the 800-900-MHz band, with cells located at GSM base station sites; and a field test conducted in Washington, DC, operating on two-sectored cell sites involving seven mobile units, plus simulated other user and other base station interference     

Research on the measurement of the price change of telecom services in China

1 Introduction The telecom service price (TSP) is the focus of benefit of distribution between telecom enterprises and customers. With the opening of the telecom service market and the increasing competition, the changes in the TSP became more frequent, e…     

Correction to “Estimating two-dimensional frequencies bymatrix enhancement and matrix pencil”

The authors describe an amendment to the paper by Hua (IEEE Trans. Signal Processing, vol.40. no.9, p.2267-80, 1992). The amendment is to the tables where a numerical error was caused by a bug in the noise generation subprogram. The error was not major enough to alter any conclusion drawn. Specifically, the patterns shown in Figs. 1-8 of the original paper are actually the same as the correct ones, but the biases and deviations shown in Tables I and II should be replaced by those given in the present correction     

Comment on “Text compression as rule-based patternrecognition”; “Text compression using rule basedencoder”

The original authors have designed rule based compression algorithms (RBE) and compared them with the well known Lempel Ziv family of algorithms (LZ) [1992/1993]. They concluded that their algorithms are superior to LZs (from 50 to 230% better). This comparison is unfair. The reasons for this conclusion are given