Abstract:The spectrum analysis and sine wave curve fitting are the most common methods used for ADC dynamic performance tests. But if the SNR of signal source is lower than ADC system, there will be a bigger deviation in the test result. A new method is proposed to test dynamic performance. This method can eliminate the influence of signal source, through which the dynamic performance of high-resolution ADC can be tested with a conventional signal source. The simulation proves the validity of this method. Finally, the test result of an ADC system is given.

Abstract:The technology of the radar discriminating ballistic missile is analyzed so as to evaluate the discrimination capability of ground-based radars in the US National Missile Defense (NMD). According to the characteristics of the ballistic target clusters during the mid-course and re-entry phase, an integrative discrimination strategy for the missile defense system is developed which involves the structure, stance and re-entry characteristics of the target, and each discrimination measure is followed by technical evaluation.

Abstract:The virtual memory is a staple in modern processor system. In virtual addressing scheme, the translation from virtual address to physical address is one of the highest frequency core service in the pipe line, and tends to be on the critical path determining the clock cycle of the processor. In order to speed up the address translation, the most modern processors have designed a hardware unit called translation look-aside buffer(TLB). Based on analyzing the traditional address mapping mechanism of TLB, this paper has put forward the regions and Cache line tag pre-validation to optimize the translation, and removed the TLB delay bottleneck in the whole memory access.

Abstract:In heterogeneous data sources integration systems, there can be many special limited access patterns to access interface of data sources, i.e., binding patterns impose a restriction that one or more input attributes must have a binding, and also restrict the output attributes that are projected. Constrained by the expressiveness of the access interface, users often have difficulty in articulating a precise query over the data sources. In this paper, we propose a data model for data sources' capability object integration (COIM) to capture a rich variety of query-processing capabilities and present algebra to compute the set of mediator-supported queries based on the capability limitations of the sources they integrate. By computing mediator query capabilities and representing them in the same way as those of data sources, we enable mediators to be used by other mediators as well as other applications, and we also make it easier for end users to know in advance which mediator queries are feasible.

Abstract:A mean period based approach for fingerprint classification is presented. It computes the mean period of every fingerprint and sorts fingerprints according to their mean periods. This approach speeds up the searching of the fingerprint database efficiently. And perfect performance is possible if combining this method with the traditional fingerprint classification.

Abstract:The design and implementation of a maltitask controlling and measuring system for the testing of rocket engines are presented. The system is developed under Windows2000,based on the network technology. The architectures of hardware and software of the system are described in detail .The system is implemented and its function is verified by the testings of engines.

Abstract:The paper introduces the configuration, function, principles and main technical index of the satellite-based direct sequence spread spectrum/phase modulation(DS/PM)dual-mode transponder. An accurate demodulation phase method is presented in PM mode. Obviously the processing precision in PM mode is improved and the capturing bandwidth widened by this means. Some key means are also developed such as capturing the initial phase of Pseudo Noise Code in spread-spectrum mode in the environment of dynamic changes and low SNR, and synchronizing the carrier wave with large Doppler frequency shift. All these ideas and methods are very valuable in developing space technology.

Abstract:Through the mechanism called lateral inhibitory existing among the visual neurons, visual information can be selectively detected. Simulating this mechanism among visual cellars through a mathematical method, a shunting inhibitory retinal cellular neural networks(SIRCNN) model based on early vision is provided. The stability analysis of its dynamics and the equivalent circuit diagram are presented and a method of detecting edges based on this model is provided. From the test result, such a method based on the biological visual mechanisms can efficiently enhance and detect edges . Because the cellular neural networks are uniquely suitable for the high-speed parallel computation and easy to implement in hardware, this model has more potential in real-time image processing.

Abstract:MFCC can express speech spectrum more accurately at low frequency, so MFCC is a good method to express the spectral envelope in voice conversion; A new and efficient algorithm for MFCC is proposed. At first, the staircase envelope is obtained through harmonic extraction, then the staircase envelope is transformed by Mel frequency scale, at last the MFCC coefficients are extracted by cosine transformation. The algorithm can be realized easily, and the result is good.

Abstract:3D structure from aerial image sequence is acquiring much attention in aerial photogrammetry. A novel method based on factorization and bundle adjustment，as well as its principle and implementation is presented. Being the bridge between factorization and bundle adjustment, the notion “R-T”mode based collinearity equation is clarified as well as its linearization equations. Synthetic and real image test show the new method gives an accurate and robust result, and it can be applied to aerial surveying and mapping, virtual reality and military reconnaissance, etc.

Abstract:The traditional image edge detectors can only get multiple-pixel-wide edges usually, thus it is difficult to operate by post-processing methods. The paper presents a novel edge thinning algorithm named as connectivity preserved edge thinning algorithm, which combines the detecting strategy of the connectivity critical point with the estimating method of the edge direction. It can preserve the origin edge information such as connection and direction. Moreover, it gets ideal or acceptable single-pixel-wide edges with lower computing cost.

Abstract:The hindrance which currently precludes the use of Cf/SiC composites is the oxidation of carbon fiber at the temperature higher than 400℃.Therefore,it is necessary to develop coatings capable of protecting Cf/SiC components from oxidation.This coatings consist of three layers,a CVD-SiC bonding layer,a self-sealing active layer by forming glassy phases on exposure to oxygen,and a CVD-SiC erosion resistant layer.Oxidation tests was carried out.The results indicated that the samples with only CVD-SiC coating have much mass loss,and the samples with three layers of coatings including a self-sealing active layer have little mass loss from the temperature of 800℃ to 1200℃.Samples with self-sealing active layer which underwent an oxidation test at 1000℃ in the atmosphere for 288hr suffered only 2.3% mass loss and a residual strength of 452.9MPa.At the same time,CVD-SiC shows various appearance after oxidation at 800℃,1000℃,and 1200℃.The surface formed at 1200℃ has some liquid phase characteristics.

Abstract:The polycarbosilane (PCS), the precursor of SiC fiber, was synthesized at the high temperature and under high pressure by thermal decomposition of liquid polysilane (LPS) which was obtained by thermal decomposition of polydimethylsilane (PDMS). The influence of synthesis conditions on final pressure at the room temperature, Si-H bond content, PCS yield, softening point, the molecular weight and distributions, and spinnability were investigated. The results showed that the molecular weight and softening point of PCS increased while the reaction temperature increased. The spinnability of PCS, however, decreased gradually. Suitable reaction time for the synthesis of PCS from LPS in autoclave should be 3 to 4 hours at 460℃, or 6 to 7 hours at 450℃. The as-synthesized PCS, in which the high molecular weight content was about 5～10wt% with softening point about 210 to 230℃, Si-H bond content more than 0.9, and good spinnability, was the suitable precursor for the preparation of SiC fiber.

Abstract:By the improved suspending drop instrument, the surface tension of precursor polycarbosilane(PCS)is measured besides the influence mechanism of surface tension on the profile-degree of trilobal section PCS fiber is discussed. Through research by SEM, we discovered that the surface tension influences greatly on the formation of the profile-degree of trilobal section PCS fiber，the competitive action between it and the agglutination resistance decides the size of the profile-degree of trilobal section PCS fiber. We also discovered that the relation between the surface tension of PCS and the temperature is basically linear.The higher the temperature，the smaller the surface tension of PCS.

Abstract:By choosing the proper time difference, the algorithmic instability of O(2,4) finite difference time domain (FDTD) method is got rid of in dealing with the crucial distinction of density and elastic constants on interfaces. Using the improved staggered grid FDTD method, we calculated the Г-Х directional band gap of the two-dimensional phononic crystal, which was composed of rectangular arrays of ? 28.5mm steel tubes with lattice constant of 103mm. Calculated results were compared with the measured ones, and both results coincided well.

Abstract:The band gaps of the two-dimensional phononic crystal composed of square array of cylinders in air are analyzed by the plane-wave expansion (PWE) method. The numerical result shows that the band gaps are independent of the physical parameter of the scatter if the acoustic impedance of the scatter is much greater than that of the matrix. So the band gaps are determined by the radius of the cylinders and the lattice constant. It doesn't matter whether the cylinders are hollow or not.

Abstract:The laser induced iodine fluorescence(LIIF) is an advanced technology to visualize the flowfield. To get the precision of using this method to investigate the mixed performance of the nozzle in chemical lasers, the cold flowfield of HYLTE nozzle in CW DF/HF chemical laser is simulated. The flowfield which uses the mixed gas made up of helium and iodine as the oxidant, the helium gas used as fuel is measured. The distribution of the mole fraction of the F atom in the first flowfield and the I₂ molecular in the second flowfield are compared. When the mass fraction of iodine molecular in the He-I₂ mixed gas is about 54%, using LIIF to measure the mixed mechanism of HTLTE nozzle in DF/HF chemical laser is more precise.

Abstract:By power ultrasonic, nano silicon dioxide particles were dispersed into polyaryl-polymethylene-isocryanate(PAPI)and rigid polyurethane foams reinforced by nano SiO₂ were prepared by polymerization PAPI with polyether polyol. SEM was employed to observe the structures of SiO₂ filled polyurethane foam and showed that nano SiO₂ particles had been dispersed uniformly in foam. Results of mechanic test show that nano SiO₂ particles in low loading fraction can increase the compressed strength and impact strength of the rigid polyurethane foam. But the addition of nano SiO₂ conduces to the rapid accretion of viscosity of PAPI, which makes the foam reaction difficult to set in and the impact strength decreases with the addition of 7% nano SiO₂.

Abstract:The IR thermal-imaging equipment is used to test the obscure effect of smoke screens. Based on the experimental data, different qualitative-evaluation methods for the IR-jamming effects are discussed. Different influential factors,such as the temperature of the target，the screen display of the IR-imaging equipment and the artificial factor are analyzed.

Abstract:A new spherical gear mechanism is intruduced. Surface formule of the new mechanism is deduced. This paper first deduces the general formules of involute, and transfoming these formulas by rotation matraix, the surface formule of the new spherical gear has been found. Based on the theory of double degree freedom, the action formule of the two spherical gears is deduced, and futhermore, the surface formule of the conjugate teeth profiles is deduced as well. The results proves that the conjugate teeth profile of the ringed involute spherical gear is also the profile of the ringed involute spherical gear.

Abstract:The ideal condition of the absolute stability for the discrete system is given, which depends on whether there is positive solution for constrained matrix inequality. Based on constrained matrix inequality, the controller can be constructed to stabilize one kind of nonlinear system. A design is given to illustrate the main conclusion.

Abstract:The generalized hidden Markov model (GHMM) is an important model for computational gene finding. Compared with the traditional hidden Markov model (HMM), GHMM needn't the assumption that the length of each state is geometrical distribution, while it is necessary for HMM. This property is appropriate for computational gene finding. The demerit of GHMM is its high computational complexity, which hinders it from being used practically. According to the characteristic of gene's structure, a novel simplified algorithm is proposed without any additional assumptions, and its computational complexity is linear with the length of sequence. The testing result for biological data demonstrates that the simplified algorithm is effective.

Abstract:Based on the magnetic suspension and balance system (MSBS), this paper mainly studies the problem of designing the position and attitude measurement subsystem of MSBS by CCD array sensors, and other relevant problems including sensors configuration, signal transformation, auto-measurement principle and flow. 5 CCD array sensors divided into two groups are used to measure the 5-degree freedom position and attitude of the model suspending in MSBS, and the multilevel inertial element circuits connected in series are used to transform the pulse width signal into voltage level signal. The position and attitude measurement subsystem of MSBS inputs its measurement signal to control loop and calibration & measurement loop of MSBS respectively. This paper introduces the configuration of 5 CCD array sensors and its measurement principle in detail. Then, the problem of the signal transformation using the multilevel inertial element circuits is discussed, and the theoretical analysis and simulation are presented. Finally, the mathematic principle and auto-measuring flow of achieving the position and attitude of the model suspending in MSBS by CCD array output signal are discussed.

Abstract:Using DCPM-FGA Direct comparison-proportional method and Fuzzy genetic algorithm to train the parameters of HMM is a very good idea. Different simulations are made for different codebook sizes. The results of simulations show that when the codebook size is bigger, the DCPM-FGA is better than B-W algorithm, otherwise, it has almost the same performance with the above algorithms.