Showing papers by "Beijing University of Posts and Telecommunications published in 1994"
TL;DR: In this article, a method for the closed-form forward displacement analysis (FDA) of the Stewart platform mechanism (SPM) with coplanar ball-joints is presented.
88 citations
TL;DR: It is proven in this paper that the (5, 2, 2) code, (6,2, 3) code and (8, 2-4) code are the only proper error-detecting codes in the (n, 2), m) nonlinear constant weight codes for n/spl ges/5, in the sense that their UEP is increased monotonically with the channel error rate p.
Abstract: The undetected error probability (UEP) of binary (n, 2/spl delta/, m) nonlinear constant weight codes over the binary symmetric channel (BSC) is investigated, where n is the blocklength, m is the weight of codeword and 2/spl delta/ is the minimum distance of the codes. The distance distribution of the (n, 2, m) nonlinear constant weight codes is evaluated. It is proven in this paper that the (5, 2, 2) code, (5, 2, 3) code, (6, 2, 3) code, (7, 2, 4) code, (7, 2, 3) code and (8, 2, 4) code are the only proper error-detecting codes in the (n, 2, m) nonlinear constant weight codes for n/spl ges/5, in the sense that their UEP is increased monotonically with the channel error rate p, of course all these proper codes are m-out-of-n codes. Furthermore, it is conjectured that except for the cases of n/spl les/4/spl delta/, there are no proper error-detecting binary (n, 2/spl delta/, m) nonlinear constant weight codes, for n>8 and /spl deltaspl ges/1. >
16 citations
TL;DR: Examples show that interpolation using the GWT is more accurate than interpolation schemes using other fast discrete sinusoidal transforms.
13 citations
TL;DR: In this paper, the forward displacement analysis of a kind of special platform manipulator mechanisms is presented, where there is a joint center on each vertex of two triangle platforms called base and top, and the other joint centers are on the edges of these triangles.
13 citations
17 Oct 1994
TL;DR: In this paper, the effect of corrosion inhibition, wear resistance and reducing the failure caused by insulated particulates are studied and described by means of micro-observation techniques, the mechanism of static coverage, dynamic coverage as well as floating and moving ability of the particles are discussed.
Abstract: Lubricants are widely used in electronic connector applications. Mainly it is for increasing reliability and reducing the cost of electric contacts. However, from the user's point of view, proper application and the mechanism of the lubrication effect of the lubricants are still not fully understood. By means of micro-observation techniques, the effect of corrosion inhibition, wear resistance and reducing the failure caused by insulated particulates are studied and described in this paper. The mechanism of static coverage, dynamic coverage as well as floating and moving ability of the particles are discussed. The effect of important parameters such as contact angle, surface tension, contact angle ratio and adhesion are also introduced. This paper is expected to be helpful to both lubricant users and manufacturers.
11 citations
TL;DR: In this paper, the effect of frequency-guiding filters on soliton collisions in wavelength-division multiplexing systems with lumped amplifiers and periodically varying dispersion has been investigated.
Abstract: The effect of frequency-guiding filters on soliton collisions in wavelength-division multiplexing systems with lumped amplifiers and periodically varying dispersion has been investigated. The evolution equations for the soliton frequency shift and time shift are derived. The numerical results indicate that the filters make the frequency shift resulting from soliton collision tend toward zero; thus the system performance is improved considerably.
3 citations
TL;DR: The probability distribution of random signals on the circuit nodes is analyzed, and it is proved that controllability is in normal distribution, and the unbiasing estimation of the fault detection probability can be obtained.
Abstract: A new approach to calculate fault detection probabilities is presented. Fault-free simulation is used in the approach. The quantities of controllability and observability are defined as probabilities of controlling and observing the nodes in the circuit. The probability distribution of random signals on the circuit nodes is analyzed, and it is proved that controllability is in normal distribution. Thus the unbiasing estimation of the fault detection probability can be obtained. According to the concept of observability, we deal with the fan-out nodes. The fault coverages for actual circuits obtained from this approach agree favorably with the fault simulation results.
2 citations
26 Jun 1994
TL;DR: Two new methods to solve two problems to produce fuzzy control rules using unsupervised competitive learning by partitioning the universe of discourse of the fuzzy variables in the rules according to the clustering results.
Abstract: Bart Kosko (1990) has proposed a method to produce fuzzy control rules using unsupervised competitive learning (UCL). But experiments show that some problems are waiting for further study. This paper discusses two of those problems. (1) How to partition the universe of discourse of the fuzzy variables in the rules. (2) How to determine the rules according to the clustering results. This paper presents two new methods to solve these two problems. Their effectiveness was proved by the simulation results from an inverted pendulum system. >
2 citations
TL;DR: In this paper, a two-step method for fabricating mini-aperture on-axis holographic lenses with high numerical apertures is presented, where the first step is to record a bifocus off-axis master holographic lens using a plane wave and a divergent spherical wave.
Abstract: A two-step method for fabricating miniaperture on-axis holographic lenses with high numerical apertures is presented. The first step is to record a bifocus off-axis master holographic lens using a plane wave and a divergent spherical wave. The second step is to record the miniaperture on-axis holographic lens using the conjugate reconstructed wave of the master holographic lens. A holographic lens array is made in our experiments in which the numerical aperture of each lens in the array reached 0.31.
2 citations
TL;DR: In this paper, the authors analyzed the electromagnetic characteristics of the sphere-TEM mode in a rectangular top horn offset coaxial transmission line (RTHOCT) by spherical wave and independent mode propagation theory.
Abstract: We analyze electromagnetic characteristics of the sphere-TEM mode (S-TEM) in a rectangular top horn offset coaxial transmission line (RTHOCT) by spherical wave and independent mode propagation theory. In our analysis, the boundary integral equation technique and multi-local expansion method (MILEM) are applied. The computational practice shows that MILEM can accelerate the convergence of the computational procedure to the EM problems with complex boundaries and multi-singular points. The error of the normalized electric potential along the boundary of RTHOCT is less than 10/sup -3/ in most parts and 10/sup -2/ in the other parts. The numerical results of the electric fields demonstrate a volume with an uniform electric field in RTHOCT. The volume is changeable through careful optimum design. The existence of the volume is a basic factor in using RTHOCT to manufacture a GTEM cell. >
2 citations
TL;DR: A novel approach to fast initializing digital subscriber loop (DLS) echo cancellers using full-duplex transmitted training sequences that can simultaneously estimate the impulse responses of the echo paths of both ends rather than estimate them separately.
Abstract: In this paper, we propose a novel approach to fast initializing digital subscriber loop (DLS) echo cancellers using full-duplex transmitted training sequences. The important difference between our method and the previous half-duplex fast training schemes is that we can simultaneously estimate the impulse responses of the echo paths of both ends rather than estimate them separately. Therefore, the initialization time is greatly reduced. The effects of the noise and symbol rate offset between two ends are examined in terms of both mean-square error (MSE) and signal to noise ratio (SNR), and the results show that the new algorithm is robust in the presence of noise and symbol rate offset. >
05 May 1994
17 Oct 1994
TL;DR: In this paper, the failure of vacuum reeds mainly appears as the switch is off but the current is still retained, which is the result of "explosion" or "volcanos" on the contact surfaces.
Abstract: The failure of vacuum reeds mainly appears as the switch is off but the current is still retained. People used to call it "adhesion" of the contacts. For new type of reeds, a thick layer of tungsten is plated on the blade surface for improving the operation life. Experimental results show that tungsten plating can greatly increase the operation life. However, failure of the reeds are still found. Micro-investigation of the failed reeds shows that "volcanos" or craters are observed on the contact surfaces which is the result of "explosion". It is reasonable to deduce that when arcing is formed at the contact surface, temperature may rise rapidly to very high rating. If the temperature on the tungsten plating is high beyond its softening point (1000/spl deg/C), the surface hardness is reduced. When the temperature of the blade underneath the tungsten plating increased above its melting point, the expansion of the iron alloy, and the vapor pressure may form an extremely high force upward to extrude through the plating. Metal vapor concentrated between cathode and anode may cause the retention of electric current. Cracks seem to have no responsibility for the failure.
05 Aug 1994
TL;DR: In this article, a novel method for implementing the perfect shuffle with the aid of a Dammann Grating (DG) is proposed, which can achieve higher diffraction efficiency than using a holographic element.
Abstract: A novel method for implementing the perfect shuffle (PS) with the aid of a Dammann Grating (DG) is proposed. For DG is a binary phase grating, the PS can be achieved with higher diffraction efficiency than using a holographic element. Shifting the DG properly in the system, the PS with various interchannel spacings and various numbers of channels can be achieved easily. The system's properties including efficiency, space-bandwidth product are discussed. The experimental results are given.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
30 May 1994
TL;DR: This paper discusses the basic theory of the probabilistic function of a multiple branch hidden Markov model (MBHMM) for the purposes of automatic speech recognition, and shows that MBHMM outperforms the conventional ones.
Abstract: In this paper we discuss the basic theory of the probabilistic function of a multiple branch hidden Markov model (MBHMM) for the purposes of automatic speech recognition. Since it has multiple transition branches between two states, the new model can hold much more spectral information in the speech signal than the basic ones, which have only one transition branch between the states. The evaluation, decoding, and training algorithms associated with MBHMM are also derived. The resulting recognizer is tested on a vocabulary of ten Chinese digits over 28 speakers. The recognition results show that MBHMM outperforms the conventional ones. >
TL;DR: A fast and efficient method for measuring high-order Volterra kernels along axes is given, using the DC component with the input signals.
Abstract: A fast and efficient method for measuring high-order Volterra kernels along axes is given. This is a sequel of the authors’ former paper(1990). Using the conclusions of those papers mentioned above, and combining the DC component with the input signals, the high-order kernels of nonlinear systemH2(jw, 0),H3(jw, 0, 0),H3(jw1,jw2, 0) can be measured at many points.
14 Nov 1994
TL;DR: In this paper, the generation of high bit rate soliton pulse trains in a step-like dispersion profiled fiber is analyzed and the influence of various parameters such as the number of segments, the segment length and the initial condition of the source on the quality of the generated soliton is investigated.
Abstract: The generation of high bit rate soliton pulse trains in a step-like dispersion profiled fiber is analyzed. The influence of the various parameters such as the number of segments, the segment length and the initial condition of the source on the quality of the generated soliton are investigated. >
05 Dec 1994
TL;DR: The systematic design method for coded modulation on the fading channel is summarized, which can construct coded modulation systems to give optimum asymptotic performance on the fades channel.
Abstract: A brief survey of recent developments in combined channel coding and digital modulation (in short coded modulation) for Rayleigh fading channels is presented. Theoretical guidance for design and identification of the most important system parameters are given. Two constructive schemes that are suited for the fading channel are discussed. The systematic design method for coded modulation on the fading channel is summarized, which can construct coded modulation systems to give optimum asymptotic performance on the fading channel. Some proposed schemes are compared according to the design method.
13 Apr 1994
TL;DR: This paper proposes a homotopy recursive backpropagation (BP) algorithm, which introduces the Homotopy continuation method to the multilayer feedforward neural network so as to provide the global convergence and faster convergence speed than conventional BP algorithm for the feed forward neural network.
Abstract: This paper proposes a homotopy recursive backpropagation (BP) algorithm, which introduces the homotopy continuation method to the multilayer feedforward neural network so as to provide the global convergence and faster convergence speed than conventional BP algorithm for the feedforward neural network. >
13 Apr 1994
TL;DR: In this article, the bispectrum and tricepstrum of system output is set up, and a LS algorithm is presented for estimating the parameters of a FIR system.
Abstract: The relation between the bispectrum and tricepstrum of system output is set up in the paper. From the relation, the authors present a LS algorithm for estimating the parameters of a FIR system. The simulation results demonstrate that the algorithm has a better performance than the GM algorithm (Giannakis and Mendel, 1989) in the case of Gaussian noise. >
05 Aug 1994
TL;DR: In this paper, it has been observed that Er 3+ -doped fiber laser can be self-mode-locked and self-Q-switched simultaneously without any additional intracavity components.
Abstract: It has been observed that Er 3+ -doped fiber lasers, under certain conditions, can be self-mode-locked and self-Q-switched simultaneously without any additional intracavity components. An experimental investigation into such phenomena has been conducted with various fiber lasers. A self-mode-locked pulse width shorter than 500 ps (the limit of our measurement capability) has been obtained within the self-Q-switched pulse at 8 kHz repetition rate and with 500 mW peak power. The fiber design and laser performance are presented. The mechanism of operation and the potential applications are discussed.
TL;DR: The general solution to the Einstein-Maxwell equations in higher dimensions corresponding to electromagnetic fields of case (ii) withF====== it.............. =F¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ it====== it76561 =F¯¯¯¯ iz� iz76561, which covers all even-dimensional spacetimes as well as a subcase of odd-dimensional Spacetimes was given in this paper.
Abstract: Electromagnetic fields yielding plane symmetric metrics in higher-dimensional spacetimes are exhausted and classified It is shown that these EM fields must fall into one of the following two cases: (i)F
it
=F
iz
=0,i=1,,n; (ii)Ftz=0 We give the general solution to the Einstein-Maxwell equations in higher dimensions corresponding to electromagnetic fields of case (ii) withF
it
=F
iz
, which covers all even-dimensional spacetimes as well as a subcase of odd-dimensional spacetimes
13 Apr 1994
TL;DR: In this article, it is shown that the higher the quality of the solution of the TSP problem, the more parts it contains in the subspace with bigger eigenvalues of the connection matrix.
Abstract: In this article, it is shown that the higher the quality of the solution of the TSP problem, the more parts it contains in the subspace with bigger eigenvalues of the connection matrix. So, by choosing the proper parameters, a high quality solution can also be found. >
31 Oct 1994
TL;DR: In this paper, the bit error rate of a soliton transmission system with periodic amplifiers and filters is calculated and an optimal design example is given, where a filter is placed after each amplifier to reduce the interaction between pulses and the effect of ASE.
Abstract: In this paper, we first calculate the bit-error-rate of a soliton transmission system with periodic amplifiers and filters, and then give an optimal design example. The method of optimal design is a new concept which is different from previous methods. In our system, we place a filter after each amplifier to reduce the interaction between pulses and the effect of ASE noise. From the analysis of our results, we can see the effectiveness of the filter in improving the performance of the long-haul soliton communication system.
20 Jan 1994
TL;DR: A scheme for implementing 4 X 4 2-D perfect shuffle by using HOEs with photopolymers is described in this paper.
Abstract: A scheme for implementing 4 X 4 2-D perfect shuffle by using HOEs with photopolymers is described in this paper.