Showing papers by "Xidian University published in 1991"
16 Jun 1991
TL;DR: The objective of this paper is to extend the Otsu method to the 2-dimensional histogram and find that the proposed method performs much better when the images are corrupted by noise.
Abstract: One of the most useful thresholding techniques using gray-level histogram of an image is the Otsu method. The objective of this paper is to extend it to the 2-dimensional histogram. The 2-dimensional Otsu method utilizes the gray-level information of each pixel and its spatial correlation information within the neighborhood. This method was compared with the 1-dimensional Otsu method. It was found that the proposed method performs much better when the images are corrupted by noise. >
164 citations
TL;DR: In this article, a quantitative theory model for the H/sub FE/ drift has been developed and explains the h/sub SE/ drift behavior in the tests, and both are caused by the modulation of the oxide traps near the Si-SiO/sub 2/ interface to Si surface recombination.
Abstract: Accelerated life tests with high-temperature storage and electric aging for n/sup +/-p-n silicon planar transistors were carried out. Current gain h/sub FE/ increases monotonously with time during the tests, and the h/sub FE/ drift is correlated with initial measured 1/f noise in the transistors, i.e. the drift amount significantly increases with the increase of noise level. The correlation coefficient of relative drift Delta h/sub FE//h/sub FE/ and 1/f noise spectral density S/sub iB/(f) is far larger than that of Delta h/sub FE//h/sub FE/ and initial DC parameters of the transistors. A quantitative theory model for the h/sub FE/ drift has been developed and explains the h/sub FE/ drift behavior in the tests, which suggests that the h/sub FE/ drift and 1/f noise can be attributed to the same physical origin, and both are caused by the modulation of the oxide traps near the Si-SiO/sub 2/ interface to Si surface recombination. 1/f noise measurement, therefore, may be used as a fast and nondestructive means to predict the long-term instability in bipolar transistors. >
16 citations
TL;DR: By using the Werner-Kramer-Brillouin method to solve for the field inside the medium in half-space, a simple scheme of a profile inversion from the reflection data is obtained for a weakly pure conducting medium as mentioned in this paper.
Abstract: By using the Werner-Kramer-Brillouin method to solve for the field inside the medium in half-space, a simple scheme of a profile inversion from the reflection data is obtained for a weakly pure conducting medium. Some examples show the applicability of this scheme. >
13 citations
TL;DR: In this article, expressions for predicting the elasticity modulus of the materials reinforced by the second-phase grains, which may be referred to as the granular composite for the sake of simplicity, are developed based on the solution of the overmatching problem in elastic mechanics.
Abstract: In the present study, expressions for predicting the elasticity modulus of the materials reinforced by the second-phase grains, which may be referred to as the granular composite for the sake of simplicity, are developed based on the solution of the overmatching problem in elastic mechanics. Taking the voids or defects in materials as the second phase with zero elasticity modulus, one can easily obtain the expressions for predicting the elasticity modulus and the threshold of the elastic percolation failure of materials containing voids. The values of the elasticity modulus of the granular composite and the materials containing random voids and the values of the threshold for the elastic percolation failure of the materials with voids predicted by using the above-mentioned expressions are in good agreement with results given in available literature.
8 citations
TL;DR: In this article, a simple expression that is reminiscent of those used by other in void growth prediction is obtained for metal products that undergo plastic deformation, and limits are established in accordance with the onset of macrocracking.
7 citations
TL;DR: The Rao-Nam's6 private-key algebraic-code encryption scheme is modified, and a new scheme is presented which can be used to authenticate and encrypt message simultaneously, while the new scheme has the same security.
Abstract: We modify the Rao-Nam's6 private-key algebraic-code encryption scheme, and present a new scheme which can be used to authenticate and encrypt message simultaneously, while the new scheme has the same security. computational load, and efficiency as Rao-Nam scheme.
4 citations
TL;DR: In this article, the problem of bearing estimation of coherent signal impinging on an array of arbitrary geometry is studied and two approaches are developed, the first one synthesizes the observed array data into the outputs of a linear uniform array and then processes them via conventional techniques such as spatial smoothing etc.
Abstract: The problem of bearing estimation of coherent signal impinging on an array of arbitrary geometry is studied. Both approaches are developed, the first one synthesizes the observed array data into the outputs of a linear uniform array and then processes them via conventional techniques such as spatial smoothing etc. The second approach is based on the invariant subspace rotation operation which is equivalent to the, translational displacement of the array, linearly independent signal vectors are obtained thereby to span perfectly the signal subspace. As compared with the conventional processing techniques, the approach based on invariant subspace rotation does not lead to an effective decrease in aperture size and therefore a decrease in resolution capability. The computer simulations are conducted to demonstrate the effectiveness of the presented approaches.
3 citations
TL;DR: In this article, a three-dimensional analysis of internal flaws occurring in the welded seams of pressure vessels was carried out to determine the real location of the defect in the pressure vessel.
3 citations
TL;DR: In this article, the backscattering of an optical wave from arbitrary convex dielectric objects with rough surfaces is investigated and the formulas for calculating the cross section of both coherent and incoherent fields are obtained.
Abstract: The backscattering of an optical wave from arbitrary convex dielectric objects with rough surfaces is investigated and the formulas for calculating the backscattering cross section of both coherent and incoherent fields are obtained. In the infrared waveband, the influence of the geometry, permittivity, and statistic characteristic of the rough surface on backscattering cross section is analyzed, making use of rough ellipsoids as examples.
3 citations
TL;DR: In this paper, chaotic iterative least fixed point computations of multidimensional functions on partially ordered sets are investigated, representative functions are devised to describe these computation processes, and based on this representation, a necessary and sufficient condition judging the convergence of all these computations is given.
Abstract: Iterative methods for computing fixed points of functions could usually be accommodated with some kinds of chaotic mechanisms for decreasing computational complexity. In this paper, chaotic iterative least fixed point computations of multidimensional functions on partially ordered sets are investigated, representative functions are devised to describe these computation processes, and based on this representation, a necessary and sufficient condition judging the convergence of all these computations is given.
3 citations
01 Dec 1991
TL;DR: It is demonstrated that the inputs to the neurons of Hopfield continuous-variable neural network are bounded, which is useful for designing the realisable analogue electrical circuits of this kind of neural system.
Abstract: It is demonstrated that the inputs to the neurons of Hopfield continuous-variable neural network are bounded, which is useful for designing the realisable analogue electrical circuits of this kind of neural system.
TL;DR: It is pointed out, by analysing the computational complexity of this system, that this system is insecure nomatter how the system parameters are chosen and no matter how the Dickson polynomials are calculated.
Abstract: Yang Yi-Xian 1 presented a public-key distribution system based on Dickson polynomials. Varadharajan commented on it 2 and showed that the choice of parameters of such a system is quite significant in its design. In this Letter, it is pointed out, by analysing the computational complexity of this system, that this system is insecure no matter how the system parameters are chosen and no matter how the Dickson polynomials are calculated
16 Jun 1991
TL;DR: In this paper, the assumption of H.B. Atabek (1961) is applied to the Navier-Stokes equation to solve the problem of two-dimensional unsteady flow in the cochlea of the auditory system.
Abstract: The assumption of H.B. Atabek (1961) is applied to the Navier-Stokes equation to solve the problem of two-dimensional unsteady flow in the cochlea of the auditory system. The pressure gradient distribution for cochlear fluid is obtained and then used to develop a new mathematical model for the auditory system. By sampling the space coordinate along the basilar membrane, the partial differential equation is changed into a set of ordinary differential equations which can be solved in the time domain. The transfer function of the auditory model is finally derived using a recurrent method. >
16 Jun 1991
TL;DR: In this article, the nonlinear dynamics and connective stabilities of neural network dynamical systems (which include delay-time) under structural perturbations are studied by differential inequalities and vector Lyapunov functions.
Abstract: In this paper the nonlinear dynamics and connective stabilities of neural network dynamical systems (which include delay-time) under structural perturbations are studied by differential inequalities and vector Lyapunov functions. The criteria of uniformly connective stability of neural network dynamical systems are established. >
01 Jul 1991-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: Deep levels, capture cross section, and defect densities of BF2+-implanted n-type silicon shallow p+ n junctions with an energy of 45 keV and doses of 1 × 1014, 2 × 1015 and 5 × 10 s were measured by the deep level transient spectroscopy (DLTS) technique as mentioned in this paper.
Abstract: Deep levels, capture cross section, and defect densities of BF2+-implanted n-type silicon shallow p+ n junctions with an energy of 45 keV and doses of 1 × 1014, 2 × 1015 and 5 × 1015 cm−2 after rapid thermal annealing (RTA) at 900–1200 °C for 5–10 s were measured by the deep level transient spectroscopy (DLTS) technique. The reverse leakage current was measured by an FJ-356 electrometer. The study shows that both the thermally generated vacancies “frozen” in the crystal and the residual damage after RTA will result in deep levels. Therefore, if the temperature and time of RTA are optimized under given implanted conditions, the influence of deep level defects on reverse leakage current can be avoided and shallow p+n junctions with good quality can be fabricated.
TL;DR: In this article, the method and procedure of realizing parameter statistical correlation analysis of bipolar analog ICs are given, and the statistical model of parameter are constructed with double parameters (B F, Rs).
Abstract: The method and procedure of realizing parameter statistical correlation analysis of bipolar analog IC’s are given, and the statistical model of parameter are constructed with double parameters (B F, Rs). Based on the comparison and analysis of the circuit characteristics, it is shown that the method can be used for analysis and design of bipolar IC’s.
11 Jun 1991
TL;DR: The sensitivity, semisensitivity, trail sensitivity, and nth-order zero sensitivity of neural networks are investigated and the sensitivity analysis approach of nonlinear neural network systems is established.
Abstract: The sensitivity, semisensitivity, trail sensitivity, and nth-order zero sensitivity of neural networks are investigated. The sensitivity analysis approach of nonlinear neural network systems is established. As an example, the sensitivities of the Hopfield neural network model are studied. >
TL;DR: A very simple and fast attack with continued fractions is given, which can completely break the Okamoto cryptosystems.
Abstract: The Okamoto cryptosystems1 have drawn attention for their properties of fast encryption and decryption. A probabilistic attack based on the L3 algorithm was proposed by Vallee et at. Other attacks have also been proposed. In the letter, a very simple and fast attack with continued fractions is given, which can completely break the Okamoto cryptosystems.
16 Jun 1991
TL;DR: In this article, a separable approach based on multiple uniform linear arrays for two-dimensional (2D) high-resolution direction-of-arrival (DOA) estimation is presented.
Abstract: In this paper, the authors present a novel separable approach based on multiple uniform linear arrays for two-dimensional(2-D) high-resolution direction-of-arrival (DOA) estimation. The 2-D DOA estimation is performed by the 1-D orthogonal processing over each linear array's measurements simultaneously. The new approach proposed is highly parallel, and the so-called 'frequency annexation' phenomenon has no effect on its application. Simulation results are provided to illustrate the effectiveness of the new approach. >
16 Jun 1991
TL;DR: In this paper, a Fourier transform pair of a staggered autocorrelation function and its power spectral density (PSD) is presented, and some properties of the staggered PSD are described.
Abstract: Presents a Fourier transform pair of a staggered autocorrelation function and its power spectral density (PSD) and describes some properties of the staggered PSD. Based on four types of spectrum estimation with uniform periods (BT, LP, ML, LSR) and the staggered PSD, this paper also proposes the corresponding types of spectrum estimation with stagger periods, discusses their performances, and gives some application examples. >
01 Jan 1991
TL;DR: In this paper, the percolation process in high Tc superconductor Ba x Y 1-x Cu 3-y system is fully studied by site-bond model in the present paper.
Abstract: The percolation process in high Tc superconductor Ba x Y 1-x Cu 3-y system is fully studied by site—bond percolation model in the present paper. It is shown that, there are two superconductivity phases in this system. The first one is the well—known Ba 2 YCu 3 O 9-δ with the initial turn temperature 100K, and the second is the phase containing more YCuO and less Ba with the initial turn temperature 60K. Furthermore, It is found that the effective methods to increase the critical current density and the zero resistance temperature are as follows, 1, decreasing the average junction resistance of normal state; 2, increasing the fraction of superconductor phase; 3, increasing the initial turn temperature Tco.
TL;DR: In this paper, the authors used the concept of surface theory in classical differential geometry to obtain relations of field magnitudes at two points along a flux line in the electrostatic field heuristically.
01 Oct 1991
TL;DR: Some measurement indexes on the security of stream ciphers derived from some spectrum-techniques-based cryptanalyses are summarized, and some results on the stability theory of streamciphers obtained by using spectral techniques are presented.
Abstract: Summarizes some spectrum-techniques-based analyses of some stream ciphers. The correlation analyses of some stream ciphers are discussed, and two BAA approaches to the cryptanalysis of some stream ciphers are presented. Some measurement indexes on the security of stream ciphers derived from some spectrum-techniques-based cryptanalyses are summarized. These indexes include the correlation-immune order of the combining functions of some binary additive stream ciphers, weight complexity, sphere complexity, variable-complexity distance, fixed-complexity distance, and weight period as well as sphere period of key streams. Some results on the stability theory of stream ciphers obtained by using spectral techniques are presented. >
24 Jun 1991
16 Jun 1991
TL;DR: Experimental results show that this system can realize real-time target recognition and location and there are three parts in the system: real- time online segmentation and labelling circuit; parallel feature extraction circuit and main board based on TMS32020 digital signal processor.
Abstract: The authors present an air-to-air real-time target recognition and location system. There are three parts in the system: real-time online segmentation and labelling circuit; parallel feature extraction circuit and main board based on TMS32020 digital signal processor. Experimental results show that this system can realize real-time target recognition and location. >
28 Oct 1991
TL;DR: The authors show both analytically and by simulation that the proposed networks are guaranteed to provide results arbitrarily close to the correct values of these problems within RC time constants on the order of hundreds of nanoseconds.
Abstract: The authors propose neural networks to compute the weights of adaptive filters and to solve deconvolution problems. They show both analytically and by simulation that the proposed networks are guaranteed to provide results arbitrarily close to the correct values of these problems within RC time constants on the order of hundreds of nanoseconds. The proposed neural networks can provide the optimum weights under the least-square criterion during an elapsed time of only a few characteristic time constants of the circuit. >
TL;DR: Based on the Volterra-series and nonlinear transfer function theories, a new approach to analyze the nonlinear properties of the cochlea is proposed in this article, where an analytic solution in the frequency domain, which may be made arbitrarily close to the true one, can be obtained with this approach.
16 Jun 1991
TL;DR: A random search algorithm called 2-D genetic optimizer algorithm (2-D GOA) is developed and an application of this algorithm in sequence image coding is given.
Abstract: Searching a global optimum point in a multimodal performance surface is unavoidable in many DSP applications and, in these cases, the algorithms based on gradient estimation such as the method of steepest decent are unsuitable To overcome this problem, a random search algorithm called 2-D genetic optimizer algorithm (2-D GOA) is developed in this paper In addition, to illustrate the advantage of 2-D GOA, an application of this algorithm in sequence image coding is given also >
16 Jun 1991
TL;DR: In this paper, the optimal problems of CMOS gate circuits are given and the model of a mixed integer programming of the maximum stage number for CMOS inverter chain is obtained under the conditions of some constrains.
Abstract: In this paper, the optimal problems of CMOS gate circuits are given and the model of a mixed integer programming of the maximum stage number for CMOS inverter chain is obtained under the conditions of some constrains. A design method and procedure of the mixed integer programming are suggested based on a continuous mathematical optimization approach. An example of actual simulation for CMOS chain is given. >
16 Jun 1991
TL;DR: Two types of canonical circuit models of dynamic system in KCL form and KVL form are presented and a novel method for synthesising linear and nonlinear high-order dependent sources is presented.
Abstract: Two types of canonical circuit models of dynamic system are presented in this paper: KCL form and KVL form. A novel method for synthesising linear and nonlinear high-order dependent sources is also presented. The canonical circuit models can be used to computer simulating all linear or nonlinear differential equation systems. Via the models and using general circuit simulation program SPICE one can find the output variable and all state variables in a system simultaneously. Using the canonical model, the authors have given the simulation results of two practical control systems. >