Abstract:Numerical study of plug nozzle flow field and thrust characteristic was completed based on 3-D TLA NS equations with NND2M scheme. Calculations were performed under ideal, perfect gas assumptions. Turbulence was taken into account with a k-εturbulence model. The results show a significant performance increases at the sea level compared with the bell nozzle. They also show that NND2M scheme is fit for numerical simulation of complex jet flow.

Abstract:The full Navier-Stokes equations are adopted to describe the unsteady oscillating flow f ield over the sphere-cone. The formula of damping-in-pitch derivatives is presented under Etkin’s theory. The steady flow field is solved by the NND scheme in ADI form, and the unsteady flow field is solved by combining the four-stage Runge-Kutta scheme and implicit residual smoothing method. The numerical results are compared with experiment and ENT calculation. The tide of the derivatives varying along with the position of oscillation center is studied.

Abstract:Some space structures have critical vibration problems owing to their low stiffness and low damping. And some traditional displacement control methods are no longer suitable to the space structures because they are hard to install. A new way to solve this problem has been introduced. Both the dynamical strain equation and the strain control state equation have been developed. A cantilever beam has been taken as an example. Numerical simulation has been done. The results show us that the vibration strain control is of great significance.

Abstract:According to the conserration of flux on the zonal boundary, a zonal boundary scheme adapted to numerical simulation of hypersonic flowfield is derived for patched grid system. Based on this work, a multizonal numerical algorithm is developed for 2D/3D supersonic and hypersonic viscous complicated flowfield. Using this algorithm, the hypersonic blunt biconic viscous flowfield is numerically simulated with the angle of attack of 0^。and 4^。.

Abstract:This paper analyzes ill-conditioned Lagrange Equation of multibody system with three degree-of-freedom rotational joint and presents a mixed pseudo coordinate lagrange's method based on constraint replacement.

Abstract:The altitude characteristics and velocity characteristics of three types of solid ducted rocket, which are choked solid ramrocket with fixed mass flow rate of fuelrich gas generator, unchoked one and the one working under fixed mass ratio of air to fuel, were numerically studied. The results show that the performance of the unchoked ducted rocket is superior to that of the choked one. When the gas generator is loaded by fuel-rich propellant with high exponent, the unchoked ducted rocket can almost be worked under fixed mass flow ratio of air to fuel.

Abstract:An algorithm to approximate a planar NURBS curve by ellipse-arc and bi-ellipse-arc is presented. The piecewise ellipse-arc spline calculated by this algorithm is G¹ continuous, and shape preserving. Compared with the present arc-approximation, this algorithm does not need equation-solving, and enable an automatic choice of parameter increment responding to the given interpolation tolerance in calculation of the character points of ellipse-arc. The algorithm also has advantage in approximation error control, which can control the approximation error to an expected one. Compared with present line-approximation mode, this algorithm, which needs no extra time and space in calculation, is applicable to CNC environment. The algorithm is specially valuable in cavity and contour machining.

Abstract:The application of active fillers, Al, Cr, TiH₂ and Zr, in the preparation of polycarbosilane (PCS) derived ceramics was investigated. The results showed that the inclusion of active fillers could decrease the porosity of the green compacts effectively, increase ceramic yields of PCS by reacting with N₂, free carbon and/or gas volatile of PCS during pyrolysis to produce new compounds. It was found that Al and Cr could restrain the linear shrinkage of the green compact upon pyrolysis. While TiH₂ and Zr could not. The linear shrinkage got higher with increase of the volume ratio of TiH₂/PCS and Zr/PCS. It was also shown that the inclusion of Al and Zr could enhance the three-point bending strength of the resulted ceramics with the strength of 212MPa and 104MPa when the volume ratio of Al/PCS and Zr/PCS were 60% vol, respectively, which were accordingly 3.3 and 1.6 times of that of the resulted ceramic in which active filler was not included. The inclusion of TiH₂ and Cr, however, could not enhance the strength. So Al was thought as the best among the four fillers. The phase compositions of pyrolysis products were analyzed using X-ray diffraction( XRD). Fracture surfaces of specimens after three-point bending tests were examined on the scanning electron microscope(SEM).

Abstract:The effect of sintering temperatures on the interfaces and mechanical properties of the C_f/SiC composites was investigated. Owing to the poor sinterability as a result of low sintering temperature (l700℃), a very weakly bonded fiber/matrix interface was formed , which gave the composite poor mechanical property. On increasing sintering temperature to l800℃, a carbon-rich interface not only avoided the direct contact of the fibers with the matrix, but also made the fiber/matrix bonding desirable, so the composite achieved excellent mechanical properties. However, the composite sintered at l850℃ or higher temperature showed substantially degraded mechanical properties, which was mainly attributed to the improvement in the fiber/matrix interfacial bonding and deterioration in the properties of the fibers caused by the serious reaction between the fibers and the interphase.

Abstract:Ionic exchange membrane is treated and chemical modified. Then, the effect of treatment condition, chemical modification method and the voltage of electric fields on ionic exchange membrane separation efficiency of dioxide carbon are studied. The result shows that the dioxide carbon flux through ionic exchange membrane can be evidently increased by improving treatment condition, exerting electric fields with low voltage and adding hydrophilic materials into membrane.

Abstract:The charged particle beam tends to diverge and disperse when it propagates beyond the exit port of the accelerator owing to the mutually repulsive force exerted by the beam's similarly charged particles. The authors study the spreading of charged particle beams propagating in the vacuum of outer space in the effect of self-generated space charge force on the basis of the Lorentz Transformation of the Relativity Theory and Newtonian Mechanics, deduce a spread equation of propagation of charged particle beams, and present a method calculating the beam spreading radius. Then, the influences of the beam types, beam energy, beam current, initial radius and divergent angle on the beam propagation are discussed briefly. Finally, we point out that the electron beam with a high energy, weak current and big initial radius must be chosen as a weapon from a point of view of propagation technology. The results of the study are not only in agreement with open data now, but also provide a scientific basic for studying beam propagation technology .

Abstract:Real-time algorithms are given to generate 4-channel stereo sound for virtual battlefield. For the special case of 4-channel stereo sound, first we studied the speaker layout scheme of 4-channel stereo sound system. Based on the given speaker layout, we dealt with the attenuation of sound intensity and turned a mono sound into a stereo one. Then, a criterion for evaluating the effect of sound mixing is proposed. An algorithm based on this criterion is also given to mix sounds randomly in real-time. The algorithm has been successfully applied in one of our applications to realize a real-time 4-Channel Stereo Sound environment for virtual battlefield. The effect is quite good.

Abstract:Based on the research of AI involved in FDD and data approach, The paper has presented a new algorithm for formula discovery from a large amount of experimental data. And then we build up the system by using the algorithm based on space of operators. The basic rules of operators are simplified, and the other three rules: derivative rule, inaccuracy rule and end rule, are introduced, which extend the knowledge lib and make it easy to use the rules in lib. Through the above improvement more forms and complexity of functional formulas are found than BACON and FDD system. In the end, the simulation result is given.

Abstract:From the software fault-tolerance view, we introduce the group communication technology to the active replication technology, propose a new dynamically active replication protocol based on a coordinator. When the coordinator is crashed, the protocol can dynamically select a new coordinator process and ensure the state of all the backup service processes are consistent. The advantage of the protocol is the short response time and high efficiency.

Abstract:According to the features of the object-oriented database and its query, the stage -by-stage executing strategy and the data operation parallel executing algorithm are proposed. The theoretical analysis and simulation results show that they are efficient and practical.

Abstract:A novel fusion scheme is presented based on fuzzy sets, considering the problem of information loss resulting from local“hard” decision during the traditional decision-layer fusion process. The theoretical analysis and simulation results show that this method works better than traditional“K-rank”fusion rule, and the ROC curve approaches the optimum.

Abstract:A new scheme of orthogonal multicarrier CDMA based on wavelet packet functions is proposed. Transmitted data bits are serial to parallel converted to a number of parallel sub-channels. On each sub-channel each bit is spread by PN code. Each chip on different sub-channel modulate different wavelet packet functions. Good properties of wavelet packet functions ensure that the system can suppress multipath interference, inter-subchannel interference (ICI) and multiple access interference (MAI) effectively. The system performance is investigated for a multipath, slow Rayleigh fading channel. The performance advantages of the system over that based on DFT are demonstrated by both analytical and simulation methods.

Abstract:Two factors in the split-and-merge image region segmentation algorithm that lead to incorrect segmentation, the merge sequence and merge predication, were analyzed. The corresponding improvements were presented, and the improved algorithm was realized. The effectiveness of the improvements was testified by comparing the results of the improved algorithm with the results of the classic algorithm.

Abstract:The Demodulation of WBFM(Wide-Band Frequency Modulation)signal is a typical nonlinear processing in communication. This paper introduces a new method using DSP to demodulate the WBFM signal in the digital receiver.

Abstract:In 3D angle only target localization system, the model and algorithm are important to better estimate the performance. The own-plane NED inertial reference, the own-plane body reference, and the antenna reference are introduced to model the position estimation problem with airborne sensor. Then three state equalities and four filtering algorithms are compared by simulation for choosing the best one.

Abstract:We use the technology of MMX to realize the motion compensation algorithm of H.263 based on the analysis of motion compensation in the H.263 and the MMX instruction set.

Abstract:A new numerical integral algorithm is presented according to the idea of multiresolution sampling. Its precision is improved by the forcing function. It's easy to use in high-dimensions integral by tensor extending method. The results show that it is not only in good agreement with traditional Simpson algorithm but also more precise to appreciate the high-vibrating integral.

Abstract:A method for estimating the matching performance of TERCOM map under non-stationary terrain is proposed. First, the statistical property of measures of terrain matching algorithms is studied through difference process of terrain. The mean and variation of measures are expressed with regard to the moment of terrain difference. Then, the relationship between the statistical property of measures and the probability of partial searching acquisition is discussed. Estimation of TERCOM map performance with the moment of terrain difference and the probability of partial searching acquisition is proposed. Experimental results of real terrain show that the method herein is efficacious.

Abstract:In the research of terrain navigability, how to evaluate some terrain’s navigability is an important problem at all times when aircraft fly into the terrain in different directions. This paper sets up a mathematical narration (FBM) according to the terrain’s nature features. Through the analysis of the profile spectral moments and the surface spectral moments, a new measurement value of terrain feature—isotropy- coefficient is presented, which is based on the application of fractal geometry theory. This paper also derives the qualitative relation between matching probability of congruent terrain and different directions, which helps to improve the efficiency of navigability analysis.

Abstract:It is proposed that robust H_∞ sub-optimization control problem can be solved by solving two algebraic Riccati inequalities. We have also studied robust H_∞/H₂ mixed sub-optimization controller based on Algebraic Riccati Inequality. Moreover, an example of application is given to illustrate the main results.

Abstract:A new approach to real time detection of harmonic and reactive currents for single-phase circuit was proposed. It makes use of some characteristics of triangle functions，and calculates the amplitudes of the fundamental active and the reactive current components in distorted current. Then it separates them from the ac components by low-pass filters. Finally，the fundamental active and the reactive current components were obtained. The circuit configuration of the proposed approach is simple，its dynamic response speed is fast，and its detection precision is high. It can detect any current component in distorted current or the sum of the harmonic and the reactive currents. The simulation and the experimental studies illustrate the performance of the proposed approach.

Abstract:The computer relay protection facility takes on the role of judging the failure of electric power, at the same time it gives message to run personnel and communicates with other devices, so it must be a highly reliable measurement and control system with high performance. The paper analyses the composing of computer relay protection facility based on standard bus and mainly introduces the steps of improving the reliability of the system. The computer relay protection facility based on such a principle has been developed and applied to the Central China Electric Power System.