Abstract:Spatial database is the core of GIS. First，we introduce the basic concepts of spatial database，and then analyze SDE，a spatial database which can integrate spatial data and attribute data. Currently proposed spatial information model can be divided into field-based model and object-based model. Each model has its advantages and limitations. Since both models are needed in application，we thus propose our object-oriented model，which integrates field-based and object-based model.

Abstract:Temperature drifts and time-varying drifts are primary factors of error of electronic analytical balance. It is important to compensate for the drifts. This paper introduces the working principle of electronic analytical balance, analyses the mechanism of the temperature drifts and time-varying drifts, presents a series of measures to compensate automatically for the drifts, and gives the auto-compensation methods of sensor, hardware and software. Practical application shows that the auto-compensation methods are feasible.

Abstract:From the angle of a beam-forming, the cross-range focusing principle of the synthetic-aperture radar based on nonsinusoidal waves is studied. The expressions of antenna pattern for both rectangular signal and Gaussian signal are presented. Compared with the conventional narrow bandwidth SAR whose cross-rang resolution is determined by the carrier frequency, the cross-range resolution of the nonsinusoidal SAR is affected by the signal bandwidth.

Abstract:The principle of distributed arithmetic and its implementation in LUT-based FPGA are introduced. The difference in area cost and performance between serial distributed arithmetic and parallel distributed arithmetic is also described.

Abstract:With the development of the mobile communication, the CDMA techniques has attracted more and more attention. To reduce interference, M-ary orthogonal signaling is employed. In this paper, the performance of the DS-CDMA system with M-ary orthogonal signaling is analyzed in terms of the bit error probability by analysing the statistics of the received baseband signal. .

Abstract:A new two-level scheme of access control based on a single-code CDMA system supporting multiclass traffic is proposed. By means of this scheme, the users of real-time traffic transmit their packets without incurring further delay once admitted to the system but the access of nonreal-time data users is regulated at both call level and burst level. Thus, the latter may fully utilize the residual channels without degrading the QoS of the former.

Abstract:The model and simulation of low grazing angle sea clutter is introduced. According to the actual background, some approximate models of sea clutter have been modified. Simulation schemes are presented in detail for incoherent and coherent radar signal processing respectively. Some key problems encountered in the simulation are emphasized, and a software of simulation is realized in Visual C+ +. The results of simulation show the applicability and effectiveness of the model and the simulation scheme.

Abstract:Task matching and scheduling by genetic-algorithm-based approaches have been attractive problems. Standard genetic operators are not always suitable for task matching and scheduling based on permutation representation. Genetic operators are important for genetic algorithms. Three genetic operators are proposed: improved crossover(IMCX), internal crossover(INCX), and migration which transfers a task from a processor to another within a schedule as a kind of mutation. Simulation results and analysis show that these genetic operators are effective for task matching and scheduling.

Abstract:It is a difficult task to parallelize the existing sequential algorithm. A distributed parallelized algorithm is described by means of static data distribution after researching into the sequential algorithm of the global atmospheric data objective analysis system. We have achieved the parallelization by extracting the analysis boxes and model grid point latitude rows with leaped step and distributing data to different processors. The parallelization algorithm has a good load balance, a highly parallelization efficiency and a lower parallelization cost. Good scalability can be got from the algorithm.

Abstract:A quadrilateral axisymmetric element with rotating degree of freedom at the vertex nodes is derived. For improving the precision of the element, decreasing the sensitivity of element geometry and applying it to nearly incompressible materials, three nonconforming displacement functions and a “bubble” function are selected as the intemal freedom of the element. The results of the numerical examples show that the performance of the new element is fine.

Abstract:Molecular dynamics method is employed for studying the scattering of xenon atom from the platinum surface. After constructing the reasonable gas-surface interaction potential energy function, the stochastic classic trajectory method is adopted to solve the motion equation of both gas atom and solid atoms, then the trajectory and velocity of gas atom can be obtained. The results show that the scattering angle distribution differs from that of Maxwellian model while the speed coincides with the half-space Maxwellian distribution.

Abstract:Based on the nominal reentry trajectory, this paper presents the optimal feedback-gain-coefficients(FGCs) of the reentry longitudinal guidance for the return module1 First of all, the longitudinal planar motion equations are modeled. Secondly, corresponding to the longitudinal guidance law the perturbation differential equations are derived. Finally, according to the Pontryagin minimum principle, the optimal FGCs are given by solving the Riccati equation. Considering the practical feasibility, the varying gain coefficients are approximated to constant ones or gradual constant ones to form the sub-optimal FGCs. And the satisfactory guidance results are achieved.

Abstract:The aerodynamic model of variable wind field is established, the aerodynamic effect of wind gradients is discussed. The flight path of meteorological rocket in the variable wind field and ballistic wind field is numerical simulated. The calculation results show that the model is reasonable and the results are consistent with those of really flight.

Abstract:According to the demand of plume spectral diagnostic for liquid propellant rocket engines, a radiative transport theory for high temperature gas is developed. The result of simulation for several main atoms of the engine materials in the plume is presented. Different spectrums under different gratings are also compared and discussed.

Abstract:Si₃N₄ powders have been pre-treated by shock activating and hot-pressed into Si₃N₄ ceramics. Three kinds of shock pressure, and three different sintering temperatures are used in the experiments, SEM, TEM and X-ray Diffraction have been used to analysis the structure of the Si₃N₄ powders and ceramics. The properties of Si₃N₄ ceramic have been tested. The results show that shock activation give positive action to the densification of Si₃N₄ powder and the increase of properties of the Si₃N₄ ceramics; the ceramic parts shocked under 40 GPa and sintered under 1800℃ have the best properties. The bend strength reaches 1107.2 MPa, at the same time, the fracture toughness reaches 12. 20MPa.m^1/2.

Abstract:Abundant-BaCO₃-YBCO superconductor is illuminated by laser(CW-CO₂ laser, CW-YAG and plused-YAG laser). The influence of laser on supconducting critical electric current density Jc is studied.

Abstract:In this paper，we try to change the material composition and renovate preparation technigues in order to improve critical electric current density（Jc）of high temperature superconductor. Based on 10g 123 phase normal proportion，BaCO₃ from 5mg to 10mg are added respectively. AII sampIes are prepared by solid state reaction method. From the superconductor transit temperature（Tc），transit width ΔT，critical electric current density Jc，SEM and XRD chart，we can draw the conclusion that Tc of abundant 123 phase samples is above 90K（ΔT=1～3K）；20mg BaCO₃ is propitious to growth of 123 phase；some abundant BaCO₃ help to improve Jc.

Abstract:A new approach producing strong pulsed IR is studied theoretically and experimentally. Cylindrically imploding shock waves have been generated by use of strong impulse current making thin copper wires explode. Cylindrically imploding shock waves can make Argon ionized produce plasma and excite strong pulsed IR. The study indicates that strong pulsed IR of MW power and 10μs FWHM can be gained by using this approach.

Abstract:To make the simulation result much more actual and credible, a simulation based on the actual circumstance was proposed. The cycles that must be considered in the simulation were introduced and the data-flow in the right function calculation was given Finally two kinds of simulation design and result conduct method were given. The six dimensional simulation method introduced by this paper may be useful for the design of missile, rockets or spacecraft.

Abstract:The reliability for stress-strength models is analyzed when the stress and strength follow normal, exponential and Weibull distributions respectively. The discussions focus on Bayesian analysis adopting noninformative priors. The results of simulation show that the conclusion under noninformative priors can be explained according to the frequentist view.

Abstract:Stochastic soft real-time systems distinguish themselves from hard real-time systems in that there is no demand for every job in a task to meet its deadline. For these systems, provided that job deadline missing rate is below some threshold, total performance is acceptable. For a fixed- priority preemptive scheduled soft real-time system, we present probabilistic time demand analysis technique by which a lower bound on the probability that a job in a periodic task meets its deadline is estimated. We have also performed a simulation study of an example system and check the tightness of the lower bound. The simulation results shows PTDA has a high speed and an error below 10%. It can provide important reference for the design of soft real-time application.

Abstract:In this paper, the fundamental principle of precision displacement measurement with a doubly blazed grating is analyzed in detail by means of Fourier Optics. The mathematical expressions about the amplitude and the intensity of diffracted light are derived, and the measurement formula is presented. At the same time it is indicated that moire fringes are nearly perfect two-beam interference fringes with superb contrast. These conclusions are consistent with the theoretical and experimental results given by Post D, and helpful to further development of the measurement principle.

Abstract:Based on the study of the new requirements of the precision and ultraprecision machine technique for the error separation technique of straightness measurement, this paper analyzes quantificationally the error introduced into the time domain and frequency domain EST results by the misalignment of sensors, the neglect of yaw angle in sequential two-point method and the difference of drifting of these sensors. This paper also describes quantificationally the magnifying ability for measurement errors of the factors W(k) in frequency domain EST methods. Some measures were taken to reduce this influence. The conclusion that sequential two-point method is the best fit method for straightness measurement was arrived at the end of this paper.

Abstract:One of the NIU's primary functions is coordinate system conversion in order to provides us the ability to connect different areas simulators to DIS. This paper introduces the standard of coordinates on DIS and the other relative coordinates, and establishes the coordinate transformation among the different coordinate systems. The orientation representations in different coordinate system and the orientation transformation are also discussed. At the same time, the algorithms have been realized with C+ + in our NIU.

Abstract:AVL system is a successful application of the integration of GIS and GPS.When GPS data is displayed on a GIS map, logically the vehicle point should be displayed on the roads. But because of the effect of errors, there are warps between the true vehicle point and the displayed point on the map. It is badly necessary to correct these warps. An algorithm named Linear Abstractin Algorithm ( LAA) was put forward. It was realized through Visual Basic and Maplnfo's OLE Automation technology. Experimental result shows that LAA has correspondingly perfect precision, and the shortcoming of the algorithm is also pointed out.

Abstract:Bounadary-scan technology is being accepted by most engineers as a design-for-Testability technique and plays an important role in the test and fault diagnosis of electonical devices. In this paper, a boundary-scan prototype tester is introduced. Some problems in developing its software system are emphasized.

Abstract:The research of DSS visualized fast integration environment is the key to DSS。The paper studied the technologies of DSS visual fast integration and its implementation. It emphasizes the introduction to the DSS visualized fast integration system-Visual DSSBuilder, developed by the authors, and the introduction to the essential issues resolved in the development progress.