Abstract:The recession process of C/C nozzle of liquid propellant rocket engine is studied. The analytical model consists of both solid-phase and gas-phase conservation equations. The gas-phase turbulent reactive flow of boundary layer is analyzed with the Favre-averaged equations to account for variable density effects. The unsteady heat conduction equation is used to obtain the temperature distribution of the nozzle wall with the numerical computation. The effects of mixture ratio, film cooling, chamber pressure and the density of the nozzle material on the recession rate are discussed.

Abstract:The existing finite element model is suitable only for low frequency range and not precise because to its first order resonant frequency is much lower than that of one-dimension model when its element number is 1 and 2. A modified small element-number finite element model is pressented here, it equates its first order resonant frequency to that of one-dimension model by modifying the shunt admittance of the pipes when the element number n=1 and n=2, therefore increases its usage frequency range and computation precision greatly. Corroboration of our model's modified effectiveness is given by the simulated results of the water hammer of a single pipe after valve closure. When n=2, the calculated results obtained by using the existing finite element model deviate from those obtained by using one-dimension model obviously , but the calculated results by using the modified finite element model agree well with these by using one-dimension model.

Abstract:A pump-fed liquid rocket engine (LRE) is used as an object of study in this paper. By applying the stochastic simulation method, test data are used to verify the mathematical model of static characteristics of LRE. Not only are the actual measurement error range of the external interfering factors and the actual variation range of the internal interfering factors considered, but also the actual measurement error range of the engine parameters is considered during the model verification. The results of the model verification show that the mathematical model of static characteristics of LRE is accurate and the calculation methods employed are proper.

Abstract:This paper proposes a definition for the fuzzy entropy of clustered result , i. e. , the fuzziness measure of a fuzzy set, and based on this definition, the definition for a measure of the distribution divergence of the sampled data vectors is also given in this paper for the first time. The divergence definition offers an ideal and objective criterion about whether there exist heavily interfered data vectors in the sliding data window for the Adaptive Windowing Filter. Thus, the noise discrimination ability has been much improved, and this increases the robustness of the fault detection algorithm to the strong noises and the sensitivity to subtle fault transients. In addition, the directional similarity between the two clustered centroid vectors (corresponding to the sliding data window) has been employed to detect faults and distinguish the intermittent faults from the failure. The practical testing data with strong noises have been used to verify its efficiency and objectivity in the fault detection and discrimination from the noised data vectors.

Abstract:With the research on the next generation reusable launching vehicle, especially with the consideration of SSTO, more and more new technology ies under development. The tripropellant combustion is one of them. In this paper a thermal-dynamic model is developed and the theoretic performance of the tripropellant propulsion system is calculated and analyzed. The difference between performance of tripropellant and dual propellant system is discussed, and possibility of tripropellant system is valued.

Abstract:Grid generation is very important to the numerical calculation of fluid flow. Many methods available can be used to achieve the target, but in this paper, only the method of Poisson equations was discussed. In addition to the traditional forms of source terms recommended by Thompson, a new one deduced by the authors was used in the calculation, and the comparison between the two forms gives several valuable conclusions.

Abstract:The three-dimension motion of a parachute and payload system is studied. Both the parachute and payload are assumed to have six degrees of freedom. They are coupled by a riser. The nonlinear differential equations of motion for a parachute-payload system are developed, which model the parachute suspension lines and the riser as inelastic elements. The resulting math model is then applied to analyze the dynamic performance of a drogue parachute recovery system. The simulation results are presented.

Abstract:In this paper, a virtual machining process which can simulate the real process is advanced and established, so the problems in the machining process can be predicted, evaluated and solved before cutting pars. Its structure, modelling technology and simulation process are also described.

Abstract:In the analysis of reliability, the system structure function is useful in two aspects. On one hand, it is used to calculate the system reliability. On the other hand, it is used to analyze the system structure properties. In this paper, the difference of structure function is constructed, and then the later aspect is studied in three respects: system structure stability、system state absorbability and structure importance.

Abstract:According to the working principles of electric valves and sampling theorem, with the introduction of an equivalent circuit DXQ-1, the dynamic characteristics of electric valves in rocket propulsion system are simulated and the test technique is provided in this paper. The important circuit parameters are analyzed. Some theoretical results are also given.

Abstract:In this paper, a technique of testing the hot fracture toughness K_Ie of surface cracks is recommended. With the help of the technique, the test sample is heated, the temperature is controlled and the (p-V) curve of the force p versus the open displacement V of a crack mouth is drawn automatically. The test accuracy is very high.

Abstract:After summarizing some difficulties of large processing-angle UWB-SAR imagery briefly, the wavenumber domain algorithm (Ω-K algorithm) is used for UWB-SAR imagery in this paper. Then the theory of Ω-K algorithm is described and the problems like Stolt Interpolating are analyzed in detail. Eventually, numerical experiments on simulated echo model are presented. All results show that this algorithm has good focusing capabilities.

Abstract:Typical method of target detection is Bayesian method which is usually applied to threshold detection. In this paper, we discuss a method for simultaneous target detection and tracking based on Hough Transformation by means of incoherent integration. As to the situation of return signals with different signal to noise ratio (SNR), we discuss two forms of incoherent integration, direct integration and binary integration. Binary integration has its unique advantage in weak target detection. Theoretical performance analysis is also presented in the paper.

Abstract:A new buffer-control policy for DCT-based intrafield video coder is presented. It selects quantization parameter based on the number of three kinds of blocks in a picture and the rate-quantization models (R-Q model) for three kinds of blocks. It adapted to the scene changes through re-encoding the picture and adjusting the R-Q model. A simple and effective criterion is presented to classify the blocks, the classifying result based on it is close to the result gotten through quantizing the bits needed to code a block into three levels. This method can be applied to some other coding techniques such as H.261; MPEG, extra computations are modest. Simulation results show that this buffer control policy can control the output bit rate steadily even at scene changes.

Abstract:The formal grey temporal security policy specification language (GTSL) which is designed by us is presented in this paper. The theory basis of GTSL is the theory of grey system and that of LOTOS, the language of temporal ordering specification. Due to the improvement and originality of techniques on the ability of integrity specification, the building and expression of the procedure of integrity verification, the testing of resonability on separation of duty, etc. , GTSL becomes practical specification languages for integrity security policy.

Abstract:In this paper, an analysis of the necessity to introduce classical function approximation theory and methods into the research of ANN is presented with a brief introduction of its contents. Then, the main results about the approximation capability of MLP network and the basic analysis methods are detailed from the two aspects of classical function appoximantion and statistical analysis. The approximation capability of RBF ntework is analyzed under the view of Regularity Theory, and the difference of the best approximation property between the RBF and MLP network is revealed.

Abstract:In this paper, the history and development of quantum computation and quantum computer are reviewed. We explain that in what sense the quantum computer were shown to be more powerful than classical computer, introduce the network model and physics principle of the quantum computer and the difficulty in realization of the quantum computer.

Abstract:This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator (DMWCG), which is investigated with particle simulation method. It is showed that the DMWCG can operate in a lower diode-voltage range with much higher radiation efficiency as compared with the usual Multiwave Cerenkov Generator(MWCG). This result shows a possible way for the application of the DMWCG into such a field as high power microwave generation with Explosive Magnetic Compression. Also showed through the simulation are both the downshift of the microwave frequency in the presence of the liner and the existence of the optima for the permittivity of the liner as well as for the magnitude of the guiding magnetic field.

Abstract:In this paper, the time-dependent Fokker-Planck equation of α particle angular density distribution function in one-dimensional spherical symmetric D-T plasma is seperated to two equations relevant to velocity and ordinates when discreted in time domain. The velocity variable in these two equations is treated by multigroup method, while the ordinate variables are treated by finite element method, thus two finite element equations are obtained. By couple calculation of these two equations, the variation of α particle angular distribution function vs time is calculated numerically. Based on these results, the time and space distribution of energy deposition rates of αparticles to ions and electrons in plasma are calculated respectively, and the total energy deposition rate of αparticles to background plasma is also obtained.

Abstract:According to molecular formula YBa₂Cu_2.7Ag_0.3O_7-δ(YBCAO), we have prepared bulk superconducting samples by solid state reaction method. In order to investigate the effect of Ag₂O addition on the property of YBCO, the measurment of the temperature dependance of resistance, XRD and SEM have been used respectively. The results show that the grains become smaller and the superconducting stability is strengthened. In this paper, the results are discussed.

Abstract:After describing the principle of coherent Raman phonon occuration, the photo-produced stress distribution in detectors is estimated in some special conditions. A strong shock stress whth duratoin 10ns, amplitude 40.2 Kg/cm₂ may be produced on the surface of detectors, using two commercial YAG dye pulse lasers supplied only with 10KW source. The latent effects of some practical nonideal reasons on the photo-produced stress are analysed and discussed. The realizatoin is also reached that the energy expending of the damage effect resulting from the coherent Raman phonons is less than that of the same effect resulting from thermal effects.

Abstract:In this paper, the probability distribution of the integral random functional of the gerneralized birth and death processes is discussed, while their Laplace transform proper difference equation and their solution are offered.

Abstract:The definition of stable normal ring is presented. The decomposition of normal ring is extended. Throrgh the result, we have obtained simple proof of the property of regular local ring. We also give a researching method for regular ring.

Abstract:With the Fermat numbers F₇ and F₉ being factored into primes, a new algorithm, the number field sieve, is given, which was proposed by Pollard. Manasse and Pollard investigate this algorithm thoroughly, and develop it from the special number field sieve (SNFS) to the general number field sieve (GNFS). In this paper, we describe the new algorithm and explain the NFS implementation.

Abstract:In this paper problems which exist in 4-node isoparametric element and the methods of improving the accuracy are summerized. The authors give brief review to these methods and discuss the approach to developing high accuracy element.