Showing papers by "Xidian University published in 1995"
TL;DR: In this article, two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD), and the plasma enhanced CVD(PECVD), were investigated by x-ray diffraction and scanning electron microscopy; their gas sensing properties were also investigated.
Abstract: Haematite (α-Fe2O3) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe2O3 films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.
35 citations
20 Mar 1995
TL;DR: The experimental results show that the proposed genetic-based clustering algorithms have much higher probabilities of finding the global or near-global optimal solutions than the traditional algorithms.
Abstract: The traditional fuzzy objective-function-based clustering algorithms, the fuzzy c-means (FCM) algorithm and the FCM-type algorithms, are in essence local search techniques that search for the optimum by using a hill-climbing technique. Thus, they often fail in the search for global optimum. In this paper, we combine the genetic algorithms with traditional clustering algorithms to obtain a better clustering performance. Our experimental results show that the proposed genetic-based clustering algorithms have much higher probabilities of finding the global or near-global optimal solutions than the traditional algorithms. >
33 citations
01 Jan 1995
TL;DR: This chapter uses the Petri net (PN) model for FMS and introduces the concept of deadlock structure by using a state feedback restriction policy which prevents some enabled transitions from firing for avoiding the deadlocked system.
Abstract: Multiple products through a flexible manufacturing system (FMS) with limited resources can lead to deadlock situation In this chapter, we study the problem of deadlock avoidance by using the Petri net (PN) model for FMS and introducing the concept of deadlock structure The necessary and sufficient conditions to prevent deadlock are characterized We use a state feedback restriction policy which prevents some enabled transitions from firing for avoiding the deadlock in the system When the number of any key kind of resources is greater than 1, this policy is minimally restrictive and maximizes the resource usage We present the Petri net realization of these restriction policies The Petri net controlled by the policies may be used as the Petri net model for an FMS in which deadlock can never occur The restriction policies can be easily implemented Several examples are provided for illustration
31 citations
TL;DR: In this article, a novel approximation for inverting the permittivity profile of a one-dimensional inhomogeneous medium is derived by using an equivalent microwave networking technique, which is not only more general in the form, but suitable for both weak and strong-scattering conditions.
Abstract: In one-dimensional inverse scattering, the approximate formulas to reconstruct the permittivity profiles are very interesting because of their closed forms. Nevertheless, as the result of Born approximation, they are invalid under the strong-scattering conditions which restrict their applications. In this paper, a novel approximation for inverting the permittivity profile of a one-dimensional inhomogeneous medium is derived by using an equivalent microwave networking technique. Compared with the published formulas of Ladoucer and Jordan (1985), the novel approximation is not only more general in the form, but suitable for both weak-scattering and strong-scattering conditions. Reconstruction examples show that when the relative permittivity reaches 80, the novel formula is effective, which show the validity of this scheme. >
30 citations
TL;DR: The authors' results suggest that the weight-bounding term in PCA algorithms for extracting the first principal component could assume a class of forms.
Abstract: A dynamical system for computing the largest eigenpair of a given positive matrix is introduced. Certain qualitative properties of the proposed system are analyzed in detail. The authors' results suggest that the weight-bounding term in PCA algorithms for extracting the first principal component could assume a class of forms. >
30 citations
31 May 1995
TL;DR: In this paper, the characteristics of the greatest common factor frequency and "phase coincidence" detection technique are compared with the advantages of frequency standard comparison technique and comparison of two signals with the same nominal frequency can also be obtained in the frequency measurement of a wide frequency range.
Abstract: In recent years, a distinguishing feature of developments of precision frequency measurement techniques is highly precise measurement of wider frequency range. In this paper conventional frequency standard comparison techniques and corresponding wide frequency measurement techniques developed in recent years are compared. Based on the study of the characteristics of the greatest common factor frequency and "phase coincidence" detection technique, the advantages of frequency standard comparison technique and comparison of two signals with the same nominal frequency can also be obtained in the frequency measurement of a very wide frequency range. In the application of the new techniques, some special design methods are used. They are: 1) the method combined "phase coincidence" detection method with no dead time measurement method; 2) in the measurement of some special frequency signals, the uses of regular distribution of "phase coincidence" between two frequency signals; 3) the method with which the noise of measuring device and the noise of measured oscillator are divided in frequency characteristics; 4) for higher precision some analog circuits can be used instead of digital circuits. This paper also analyses the possibility that the new technique and instruments are used instead of conventional digital frequency meters.
25 citations
08 May 1995
TL;DR: In this paper, an efficient adaptive channel equalization method which can compensate the channel mismatch automatically by least squares theory is introduced. But, the receiver channel mismatch will give rise to much degradation of the performance for STAP.
Abstract: The space-time adaptive processing (STAP) can improve the performance of airborne early warning (AEW) radar. But, the receiver channel mismatch will give rise to much degradation of the performance for STAP. This paper introduces an efficient adaptive channel equalization method which can compensate the channel mismatch automatically by least squares theory. The effect of equalizer parameters on equalization performance is analysed in detail, and a sample of adaptive channel equalizer is given.
22 citations
TL;DR: In this paper, the properties of quasiconvex functions are discussed and relationships between them are discussed, and some properties of strictly quasico-vex and strongly quaso-vivomorphic functions are given.
Abstract: This paper gives some properties of quasiconvex, strictly quasiconvex, and strongly quasiconvex functions. Relationships between them are discussed.
15 citations
TL;DR: In this paper, a novel inverse scattering scheme was proposed to reconstruct simultaneously the permittivity and conductivity profiles, which is suitable for both continuous and discontinuous profiles, under both the weak scattering and strong scattering conditions.
Abstract: The formulation of reflection coefficients from an inhomogeneous lossy medium illuminated by TE and TM waves is approximately derived, in closed form, by using a microwave network method. From the formulation, a novel inverse scattering scheme to reconstruct simultaneously the permittivity and conductivity profiles, is proposed. This scheme is suitable for both continuous and discontinuous profiles, under both the weak scattering and strong scattering conditions. It has also been shown that when the conductivity of the medium equals zero, the reconstructed result of this scheme will reduce to the one formulated by Ladouceur and Jordan (1985). Numerical and closed-form reconstruction examples show the validity of the scheme. >
14 citations
27 Sep 1995
TL;DR: A new public-key user authentication protocol for mobile communication network is presented based on Harn, which overcomes the shortcomings of secret-key authentication protocol used in GSM and CT-2 systems, and has lower computational complexity and a higher security.
Abstract: A new public-key user authentication protocol for mobile communication network is presented based on Harn (see Electronics Letters, vol.30, no.5, p.396, 1994) proposed modified ElGa-mal signature system and Rabin cryptosystem. It overcomes the shortcomings of secret-key authentication protocol used in GSM and CT-2 systems, and a has lower computational complexity and a higher security.
12 citations
TL;DR: In this article, a useful theorem is obtained for a lossless multiport network from the unitary condition of scattering matrix, and is proven to be equivalent to the Unitary condition.
Abstract: A useful theorem is obtained for a lossless multiport network from the unitary condition of scattering matrix, and is proven to be equivalent to the unitary condition. Some illustrations are given to show how to apply the theorem to the analysis of the properties of a lossless n-port network. >
TL;DR: A modified short-time Fourier transform (MSTFT) is proposed, where the minimum entropy is adopted as a criterion to determine the width of the window, and variable-width windows to accommodate the signal's characteristics are used instead of constant- width windows.
Abstract: The short-time Fourier transform (STFT) is a typical time-frequency 2-D analysis method for nonstationary signals. Its applications in engineering are limited because of its fixed window, which results in low time-frequency resolution. To surmount this disadvantage, a modified short-time Fourier transform (MSTFT) is proposed. The minimum entropy is adopted as a criterion to determine the width of the window, and variable-width windows to accommodate the signal's characteristics are used instead of constant-width windows. Since it is difficult to find the optimal window width, wavelet packet transformation is utilized to find an approximate solution for it. This method is also applied to multi-target imaging for inverse synthetic aperture radar, and satisfactory results are achieved.
TL;DR: In this article, the Bloch wave and Green's function approaches are proposed to calculate the diffraction intensities of double-inelastically scattered high-energy electrons (i.e., the electrons that have been inelastically scattered twice as the result of exciting two distinct crystal states) within the framework of quantum mechanics.
Abstract: Dynamical theories are developed to calculate the diffraction intensities of double-inelastically scattered high-energy electrons (i.e. the electrons that have been inelastically scattered twice as the result of exciting two distinct crystal states) in crystals within the framework of quantum mechanics. These theories are needed to quantify the data of thermal diffusely scattered electron energy loss spectroscopy. The Bloch wave and Green's function approaches proposed here take into account the full dynamical diffraction effects of the electrons before and after each inelastic event. The Bloch wave theory gives a full three-dimensional description of double-inelastic scattering in crystals including higher-order Laue zone reflections, but it may not be convenient to calculate the intensity of high-angle thermal diffuse scattering of electrons because of the difficulty of including all of the possible multiphonon excitations. Green's function theory, as an alternative approach, is most suitable f...
TL;DR: This paper proves that there are no graphsG which are not self-complementary withG and $$\bar G$$ having the same chromatic polynomial when |V(G)| =p ≥ 8 andp ≡ 0, 1 (mod 4).
Abstract: In 1980, Akiyama and Harary proposed the following problem in the Proceedings-Fourth International Graph Theory Conference: “Are there any graphsG which are not self-complementary withG and
$$\bar G$$
having the same chromatic polynomial?”. The problem has been unsolved until now. This paper proves that there are no graphsG which are not self-complementary withG and
$$\bar G$$
having the same chromatic polynomial when |V(G)| =p < 8 orp = 2, 3 (mod 4), there must be a graphG which are not self-complementary withG and
$$\bar G$$
having the same chromatic polynomial when |V(G)| =p ≥ 8 andp ≡ 0, 1 (mod 4).
28 Aug 1995
TL;DR: The experimental results show that the proposed GA/FC learning algorithm has much higher probabilities of finding the global optimal solutions than either the winner-take-all or the fuzzy competition learning.
Abstract: Kohonen networks are well known for clustering analysis. Classical Kohonen networks for hard c-means clustering (trained by winner-take-all learning) have some severe drawbacks. Fuzzy Kohonen networks (FKCNN) for fuzzy c-means clustering are trained by fuzzy competition learning, and can get better clustering results than the classical Kohonen networks. However, both winner-take-all and fuzzy competition learning algorithms are in essence local search techniques that search for the optimum by using a hill-climbing technique. Thus, they often fail in the search for the global optimum. In this paper we combine genetic algorithms (GAs) with fuzzy competition learning to train the FKCNN. Our experimental results show that the proposed GA/FC learning algorithm has much higher probabilities of finding the global optimal solutions than either the winner-take-all or the fuzzy competition learning.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the optimal replacement of a discrete Markovian deteriorative system which is subject to random shocks from its environment is discussed, and the existence of optimal stationary policies which are extended control limit policies is proved.
08 May 1995
TL;DR: A new partial adaptive STP is described for practical real-time applications with highly tolerant ability in the presence of random array errors with large performance degradation.
Abstract: After analyzing the characteristics of clutter echoes received by a moving airborne radar, a general framework for partially adaptive space time processing (STP) is proposed. In order to reduce the complexity of STP without a large performance degradation, the authors describe a new partial adaptive STP for practical real-time applications with highly tolerant ability in the presence of random array errors.
TL;DR: An iterative algorithm that can accelerate the speed of convergence when calculating the cell loss probability is suggested and analyzed under conditions of discrete time cell arrival.
Abstract: One of the most important problems that must be solved in ATM networks is the priority cell discarding (PCD). A two priorities cell discarding method is suggested and analyzed under conditions of discrete time cell arrival. By introducing the? operator, an iterative algorithm that can accelerate the speed of convergence when calculating the cell loss probability is suggested. The effectiveness of the PCD in ATM networks is proved by the numeric results.
TL;DR: In this paper, the authors have simplified the sensor to a finite-length cylinder, and calculated the energy loss and temperature error of a thermometer transducer fiber-optic sensor placed in a microwave field.
Abstract: When a fiber-optic thermometer is placed in a microwave field to measure temperature, there will be energy loss due to electromagnetic interaction, which will certainly bring error in the measured temperature, within the sensor. In this article we have simplified the sensor to a finite-length cylinder, and calculated the energy loss and temperature error. In addition, the measurement error of temperature is studied for a practical thermometer transducer fiber-optic sensor placed in a microwave field. © 1995 John Wiley & Sons, Inc.
Journal Article•
TL;DR: The operating principles, working routines and configurations as well as the performances and problems of Symthetic Impulse and Aperture Radar are described more comprehensively in this paper.
Abstract: The operating principles,working routines and configurations as well as the performances and problems of Symthetic Impulse and Aperture Radar(SIAR)are described more comprehensively in this paper, especially from the point of view of the basic concepts of SIAR The characteristics of SIAR are highlighted as compared to conventional radars and phased array radars
TL;DR: The effects of the shape parameter α in the RBFN and the forgotten factor λ in RLSA on the results of the recognition of three kinds of kernel function such as Gaussian, triangle, double-exponential, at the same time, are discussed.
Abstract: This paper studies the problem applying Radial Basis Function Network(RBFN) which is trained by the Recursive Least Square Algorithm(RLSA) to the recognition of one dimensional images of radar targets. The equivalence between the RBFN and the estimate of Parzen window probabilistic density is proved. It is pointed out that the I/O functions in RBFN hidden units can be generalized to general Parzen window probabilistic kernel function or potential function, too. This paper discusses the effects of the shape parameter α in the RBFN and the forgotten factor λ in RLSA on the results of the recognition of three kinds of kernel function such as Gaussian, triangle, double-exponential, at the same time, also discusses the relationship between λ and the training time in the RBFN.
TL;DR: In this article, the authors give a numerical analysis for the electron tunneling in the double-barrier diode, where a tunneling matrix is introduced, and the formula of the transmission coefficient is established.
TL;DR: The mechanism to separate figures from background and presents a neural structure, called the diffusion-concentration network (DCN), a 2-D array of neurons with both the positive variable short-range and negative constant long-range lateral connections, that is, the diffusional signal, which spreads over the network.
TL;DR: In this article, a method of measurements and simulation for laser scattering in the geometric model is analyzed, where the geometric size of the object is only scaled down but the incident wavelength, material and configuration are keeping to not change.
Abstract: In this paper the electromagnetic similitudes for lossy and dispersive system are discussed. If both the geometric size of an object and incident wavelength are scaling-down simultaneously by analogy with microwave band, the inconsistencies exist for laser scattering in visible and near infrared bands. Another method of measurements and simulation for laser scattering in the geometric model is analyzed. That is, the geometric size of the object is only scaled down but the incident wavelength, material and configuration are keeping to not change. Although this way does not satisfy the principles of the electrodynamic similitude, it can overcome the electromagnetic inconsistencies for laser scattering. It is possible that the LRCS of the full-scale tested object are evaluated by those of the corresponding scaling-down model at identical frequency to establish theoretical models and data basis for LRCS of objects.
14 Nov 1995
TL;DR: The SRSB vocoder can encode Chinese speech of unlimited vocabulary at a bit rate of lower than 200 bps and reproduce speech with intelligibility of 95.2%.
Abstract: This paper introduces a speech recognition and synthesis based (SRSB) vocoder made by the authors, which has been judged by experts recently. The SRSB vocoder can encode Chinese speech of unlimited vocabulary at a bit rate of lower than 200 bps and reproduce speech with intelligibility of 95.2%. The vocoder consists of a real-time syllable recognizer to encode syllables based on composite hidden Markov modeling and a speech synthesizer to reproduce speech with syllable concatenation based on pitch-synchronous overlap-adding algorithm (PSOLA). It is capable of good prosodic modifications, since it can make use of prosodic parameters extracted from the input voice. Either terminal of it is implemented with an IBM-PC microcomputer equipped with a TMS320C30 DSP subsystem.
18 Jun 1995
TL;DR: In this paper, the radar cross section of an arbitrary flat plate of electrically large dimensions and coated with a radar absorbing material was analyzed by using the Maliuzhinets scattering solution of an impedance wedge and the concept of the equivalent edge current.
Abstract: Since the early 1980s, the electromagnetic stealth technique has been developed for reducing the radar cross section (RCS) of aircraft based on two principal methods. One is to cover the aircraft with a radar absorbing material (RAM), the other is to modify the aircraft shape. The scattering from an arbitrary flat plate of electrically large dimensions and coated with a RAM is analysed by using the Maliuzhinets scattering solution of an impedance wedge and the concept of the equivalent edge current. The RCS of several typical coated plates are computed and compared with the data from the method of physical optics.
TL;DR: In this paper, a theoretical model for calculating the thermal IR radiation of different backgrounds was developed, which consists of a system of steady-state energy budget equations describing the energy interaction which takes place within the underlying scene.
03 Jul 1995
TL;DR: The computer simulation shows that wavelet transform coding has a superior performance in terms of free block-effects as well as subjective quality, compared to other transform coding methods.
Abstract: This paper studies wavelet transform coding for image sequence compression, the proposed coding method includes displacement estimation in the transform domain, quantization of transform coefficient difference values and a scheme of variable length coding. The computer simulation shows that wavelet transform coding has a superior performance in terms of free block-effects as well as subjective quality, compared to other transform coding methods.
24 Oct 1995
TL;DR: In this article, it was shown from the accelerated life test and noise measurement that the failure of integrated operational amplifiers due to the drift of I/sub IB/ or I/ sub OS/ is strongly correlated with 1/f noise in the devices, and the drift is approximately proportional to the initial 1 /f noise current.
Abstract: It is shown from the accelerated life test and noise measurement that the failure of integrated operational amplifiers due to the drift of I/sub IB/ or I/sub OS/ is strongly correlated with 1/f noise in the devices, and the drift is approximately proportional to the initial 1/f noise current. 1/f noise measurement may therefore be applied as a fast and nondestructive tool to predict the long-term instability of operational amplifiers.
28 Aug 1995
TL;DR: This paper principally discusses the training problem of RBF classifiers which can be used for classification, using Genetic-based Gaussian kernel clustering method and fuzzy decision technique to complete this work.
Abstract: Radial basis function(RBF) neural networks have been used extensively in many applications for their simple ar-chitecture and fast learning. This paper principally discusses the training problem of RBF classifiers which canbe used for classification. For RBF classifiers, how to correctly initialize the number of network hidden nodes andtheir parameters is very important. Genetic-based Gaussian kernel clustering method and fuzzy decision techniqueare explored to complete this work. Then the network is trained further with back propagation learning algorithmin order to attain optimal performance. Results from the typical experiments are used to illustrate the pow and efficiency of the method. Keywords: radial basis function, neural networks, classifiers, training algorithms, clustering, fuzzy decision 1.INTRODUCTION RBF neural network is an important type of the multilayer feed-forward neural networks which have becomevery powerful tool in the domain of pattern recognition. It is a two-layer network whose output nodes form a linear