Showing papers by "National University of Defense Technology published in 1999"
TL;DR: In this article, an optimized digital speckle correlation algorithm, named big-window correlation, is proposed to iterate strain directly, which can improve the sensitivity and accuracy of the displacement gradient measurement with this method.
Abstract: In this paper, an optimized digital speckle correlation algorithm, named big-window correlation, is proposed to iterate strain directly. Verified by some experiments, the sensitivity and accuracy of the displacement gradient measurement with this method can be improved greatly. Finally, this method was applied to the measurement of the compression strain for polyurethane foam plastics materials. Then the material properties, such as the module of elasticity and the Poisson ratio, with different mass densities were obtained.
74 citations
TL;DR: In this paper, a parametric algorithm that gradually applies the RELAX algorithm and results in greatly improved computational efficiency and stability is presented, which is similar to the one presented in this paper.
Abstract: Parametric methods of radio frequency interference (RFI) suppression in ultra-wideband synthetic aperture radar (UWB-SAR) often outperform their non-parametric counterparts at the expense of computational complexity. The authors present a parametric algorithm that gradually applies the RELAX algorithm and results in greatly improved computational efficiency and stability.
39 citations
TL;DR: In this article, it is shown that the direct integration method is very efficient for the search of the cases of integrability of the three-dimensional Lotka-Volterra system.
14 citations
TL;DR: The reduced parameter model (RPM) of trajectory parameter (TP), system error and random error are presented, the RPM on trajectory tracking data (TTD) is obtained, a weighted method on measuring elements (ME) is studied and criteria on selection of ME based on residual and accuracy estimation are put forward.
Abstract: The data fusion in tracking the same trajectory by multi-measurement unit (MMU) is considered. Firstly, the reduced parameter model (RPM) of trajectory parameter (TP), system error and random error are presented, and then the RPM on trajectory tracking data (TTD) is obtained, a weighted method on measuring elements (ME) is studied and criteria on selection of ME based on residual and accuracy estimation are put forward. According to RPM, the problem about selection of ME and self-calibration of TTD is thoroughly investigated. The method improves data accuracy in trajectory tracking obviously and gives accuracy evaluation of trajectory tracking system simultaneously.
14 citations
TL;DR: A new polynomial transform algorithm for the MDDWT is obtained that needs no operations on complex data and the number of multiplications for computing an r-dimensional DWT is only 1 times that of the commonly used row-column method.
Abstract: The multidimensional (MD) polynomial transform is used to convert the MD W transform (MDDWT) into a series of one-dimensional (1-D) W transforms (DWTs). Thus, a new polynomial transform algorithm for the MDDWT is obtained. The algorithm needs no operations on complex data. The number of multiplications for computing an r-dimensional DWT is only 1 times that of the commonly used row-column method. The number of additions is also reduced considerably.
13 citations
TL;DR: In this paper, an exact solution for the relativistic equation of motion of a charged particle driven by a circularly polarized electromagnetic wave and a constant magnetic field was found for certain initial conditions.
Abstract: An exact solution is found for the relativistic equation of motion of a charged particle driven by a circularly polarized electromagnetic wave and a constant magnetic field. The explicit expressions of particle position and velocity are obtained for certain initial conditions. The results are of interest to the interaction of the high-power laser with the magnetized plasma, electromagnetically pumped free-electron laser with a guide magnetic field, propagation of electromagnetic wave signals through a re-entry plasma sheath in the presence of a strong magnetic field, and magnetic confinement plasmas.
12 citations
TL;DR: In this article, a new method was developed for three-dimensional stress analysis of laminated piezoelectric cylindrical shells with simple support, which can be subjected to various applied loadings, including distributed body force, inner and outer surface traction and potential.
Abstract: A new method is developed for three-dimensional stress analysis of laminated piezoelectric cylindrical shell with simple support. The shell can be subjected to various applied loadings, including distributed body force, inner and outer surface traction and potential. Each layer of the shell can be piezoelectric or elastic/dielectric, with perfect bonding assumed between each interface. The governing equations are solved by the state-space technique. Numerical results are presented to show the sensing and actuating effects of three-layered piezoelectric cylindrical shell.
6 citations
6 citations
01 Oct 1999
TL;DR: A prototype system providing awareness and collaborations in a virtual environment by using the visual object extracting, multiple cameras and cornpositing of the natural and virtual scenes to maintain awareness such as the proper eye contact in a teleconferecing system.
Abstract: In this paper, a prototype system providing awareness and collaborations in a virtual environment is introduced. The system fi.rlfills the idea by using the visual object extracting, multiple cameras and cornpositing of the natural and virtual scenes. The result is that the awareness such as the proper eye contact is maintained in a teleconferecing system.
6 citations
TL;DR: A recognition model for occasion system error is constructed, a principle for preventing pollution by occasion system errors is presented, and the proposed method for fusion method is presented.
Abstract: The multiple station method is important in missile and space tracking system. A fusion method is presented. Based on the theory of multiple tracking, and starting with the investigation of precision of location by a single station, a recognition model for occasion system error is constructed, and a principle for preventing pollution by occasion system error is presented. Theoretical analysis and simulation results prove the proposed method correct.
5 citations
TL;DR: In this paper, a semi-analytic method is presented for the analysis of transient response of one-dimensional distributed parameter systems, replacing time differentials by finite difference, the governing partial differential equations are reduced to difference-differential equations.
TL;DR: In this paper, a Si 3 N 4 ceramic has been fabricated by means of shock-activating and hot-press sintering, and two kinds of shock pressure, i.e., 15.7 and 25.6 Gpa, were used in the experiments.
TL;DR: In this paper, the impact broadening and shift of the lithium resonance line 2s2S - 2p2P was calculated by using R-matrix method. But the largest discrepancy of 30 percent for the broadening width was found from a semiclassical calculation.
Abstract: Electron collision with lithium atoms is calculated by using R-matrix method. The scattering parameters are applied in the determination of the electron impact broadening and shift of the lithium resonance line 2s2S - 2p2P. The width and shift are obtained based on the impact approximation. A largest discrepancy of 30 percent for the broadening width is found from a semiclassical calculation.
20 Jun 1999
08 Sep 1999
TL;DR: In this article, the authors analyzed how and to what degree the scattering and diffraction effects will disturb the charge-coupled devices (CCD) camera and the results of experiments were given as well.
Abstract: When the laser beam is out of the field of view (FOV) of charge-coupled devices (CCD) camera, part of the laser energy will also reach on the photoactive area because of the scattering and diffraction effects. If the intensity is high enough, CCD will be in saturation. How and to what degree the scattering and diffraction effects will disturb the CCD is analyzed. The results of experiments are given as well. Considering the contribution of the laser out of the FOV, the disturbing range will be enlarged. Estimation has been done.
TL;DR: According to the method, the searching schedule of the association events between two layers can be recursive and with independence, so it can also be implemented in parallel structure.
Abstract: Joint Probabilistic Data Association (JPDA) is a very fine optimal multitarget tracking and association algorithm in clutter. However, the calculation explosion effect in computation of association probabilities has been a difficulty. This paper will discuss a method based on layered searching construction of association hypothesis events. According to the method, the searching schedule of the association events between two layers can be recursive and with independence, so it can also be implemented in parallel structure. Comparative analysis of the method with relative methods in other references and corresponding computer simulation tests and results are also given in the paper.
09 Mar 1999
TL;DR: Experimental results show that this multi-scale wavelet-based non-parametric algorithm for detecting and locating corners in 2D images has high precision and stability of the corner detection and location.
Abstract: A multi-scale wavelet-based non-parametric algorithm for detecting and locating corners in 2D images is proposed. First using zero-crossing-based 2D edge detector we can get the edge elements, after edge linking and give each planar curve its orientation space representation we can get the orientation curves. Based on the multi-scale wavelet transform of the orientation curves we can utilize the information of local maximum positions to detect and locate the corners. Experimental results with some synthetic and real images show that this algorithm has high precision and stability of the corner detection and location.
TL;DR: Algorithms for checking strong/weak early bisimulation, equivalences and observation congruence are presented together with their correctness proofs and two theorems ensuring the elimination of τ-cycles and τ-edges are presented.
Abstract: Symbolic transition graph is proposed as an intuitive and compact semantic model for the π-calculus processes. Various versions (strong/weak, ground/symbolic) of early operational semantics are given to such graphs. Based on them the corresponding versions of early bisimulation equivalences and observation congruence are defined. The notions of symbolic observation graph and symbolic congruence graph are also introduced, and followed by two theorems ensuring the elimination of τ-cycles and τ-edges. Finally algorithms for checking strong/weak early bisimulation, equivalences and observation congruence are presented together with their correctness proofs. These results fuse and generalize the strong bisimulation checking algorithm for value-passing processes and the verification technique for weak bisimulation of pure-CCS to the finite control π-calculus.
Journal Article•
TL;DR: A new managing method is introduced that can properly refresh and record the memorization information in time by dividing and addressing the whole FIFO into frames and the start point of signal is properly gotten through computing in microprocessor.
Abstract: In order to solve the problems resulting from utilizing FIFO as cache in a high speed data acquisition system, this paper introduces a new managing method. It can properly refresh and record the memorization information in time by dividing and addressing the whole FIFO into frames. By means of setting up the frame interrupt signal, signal automatic triggering and caching length can be controlled easily and correctly. And the start point of signal is properly gotten through computing in microprocessor. The principle of FIFO operating in data acquisition is firstly described, then the principle and operating procedure of this method is systematically introduced.
TL;DR: In this paper, a dielectric-lined multiwave Cerenkov generator (DMWCG) was investigated with a two and one half dimensional electromagnetic relativistic Particle-in-Cell (PIC) simulation code.
Abstract: This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator(DMWCG) producing high power millimeter waves, which is investigated with a two and one half dimensional(\(2\frac{1}{2}{\text{D}}\)) electromagnetic relativistic Particle-in-Cell(PIC) simulation code. It is showed that the DMWCG can operate in a lower diode-voltage regime with much higher radiation efficiency as compared with the usual Multiwave Cerenkov Generator(MWCG). The simulation work indicates both the downshift of the wave frequency in the presence of the dielectric liner and the existence of the optima for the permittivity of the liner as well as for the magnitude of the guiding magnetic field. The required intensity of the guiding field is reduced with the introducing of the liner. The radiation is generated at the dominant frequency of 31.5GHz. The power level of 1.5GW is achieved, with radiation efficiency up to 15%. The features of parameter dependency are presented. And reasonable explanation is put forward. In addition, the enhanced propagation of the electron beam is studied in the presence of the dielectric liner.
TL;DR: In this paper, a universal refutation method is proposed and its soundness and completeness are proved by means of the universal unifying principle and it can be applied directly to any finite set of wffs without preprocessing the wFFs at all so that the refutation procedure is more natural.
Abstract: Refutation methods based on the resolution principle are generally applied to a (finite) set of sentences, which must have a series of pre-transformations (prenex normalization, Skolemization and conjunction normalization) before starting the refutation. In this paper, the authors first generalize the concept to abstract consistency class to the most general form—universal abstract consistency class, and prove its universal unifying principle. Then, based on theR-refutation, a universal refutation method is proposed and its soundness and completeness are proved by means of the universal unifying principle. This method can be applied directly to any finite set of wffs without preprocessing the wffs at all so that the refutation procedure is more natural.
TL;DR: In this article, the transient signal processing techniques for air target detection of ultra wide band (UWB)/impulse radar (IR) were discussed, and the results of these experiments verified the signal processing method efficiency.
Abstract: With reference to the air target detection of ultra-wide band (UWB)/impulse radar(IR), the transient signal processing techniques was discussed. In weak UWB signal detection, the wavelet transforms and high order spectrum estimation techniques were preferred. In target characteristic analysis, a time domain bispectrum estimation algorithm was used to analyze the target impulse response, which could estimate accurately local scattering distribution of complex target. A free field IR experimental system installed in an anechoic chamber was used. With this system, experiments to several target models were made. The results of these experiments verified the signal processing method efficiency.
01 Nov 1999
TL;DR: From the point of view of space-time adaptive processing (STAP), the clutter suppression principle and realization of multiple phase center-multiple delay taps displaced phase center antenna (DPCA) techniques for airborne radar are researched.
Abstract: From the point of view of space-time adaptive processing (STAP), the clutter suppression principle and realization of multiple phase center-multiple delay taps displaced phase center antenna (DPCA) techniques for airborne radar are researched in this paper. When the DPCA condition is not satisfied with different pulse repetition frequency (PRF), the clutter suppression performance of DPCA is analyzed. Meanwhile, the internal relation between the modern DPCA techniques and STAP is also investigated.
27 Jul 1999
TL;DR: The built-in-test (BIT) design of electric vehicles, driven by an AC motor, requires high-reliability and easy repairability and is used in the authors' system.
Abstract: This paper describes the built-in-test (BIT) design of electric vehicles. An electric vehicle, driven by an AC motor, requires high-reliability and easy repairability. BIT design, is therefore used in the authors' system. As for the electric vehicle, BIT before task, BIT in task, and BIT for repairs are adopted. The hardware and software of the system are so designed as to meet the test requirements.
TL;DR: In this article, a robust model reference adaptive controller based on variable-structure strategy is designed for a class of nonlinear systems with uncertain parameters and bounded external disturbances, without a priori knowledge of bounded disturbance, both the unknown system parameters and the upper bound of external disturbance are estimated by the design of adaptive law to ensure the accessibility of sliding mode and the global stability of the closed-loop system.
Journal Article•
TL;DR: In this paper, the exact analytical solution of rope under selfgravity is derived, on the basis of the accurate relation between strain and displacement, the equilibrium equations for absolute flexible bar with large deformation.
Abstract: On the basis of the accurate relation between strain and displacement, the equilibrium equations for absolute flexible bar with large deformation, the exact analytical solution of rope under selfgravity is derived in this paper. FOr example, the electric cable is analyzed and discussed.
16 Nov 1999
TL;DR: In this article, a backward fault partitioning approach based on output fan-in cones (BFPOC) is presented which combines the relevant fault identification and shortest path sensitization.
Abstract: Firstly we propose a theoretical method to increase the speed-up ratio in parallel test generation based on fault partitioning. Based on this method, a new fault partitioning approach-Backward Fault Partitioning based on Output fan-in Cones (BFPOC)-is presented which combines the relevant fault identification and shortest path sensitization. In addition, BFPOC is compared via experiments with the approach of Toward Fault Partitioning based on Input fan-out Cones (TFPIC) proposed by Bannerjee (1994) and the widely used method-Equal Distance Partitioning of Fault Sequence (EDPFS) respectively. The results show that in a large-scale parallel processing environment, BFPOC can obtain higher speed-up ratio than the other two approaches.
01 Nov 1999
TL;DR: In this paper, the physical and mathematical models of covered targets have been proposed and the simulation results of the FDTD using anisotropic perfectly matched layer (PML) boundary conditions are given.
Abstract: The research into transient scattering by covered targets has been developed recently In this paper, the physical and mathematical models of covered targets have been proposed and the simulation results of the FDTD using anisotropic perfectly matched layer (PML) boundary conditions are given We analyzed its scattering
22 Jul 1999
TL;DR: The preliminary research on machine-leaning system used for ALV is introduced, which is a kind of online machine- leaning system without teacher and a method of fusing human intelligence into machine intelligence.
Abstract: The control of Autonomous Land Vehicle (ALV) is a kind of typical nonlinear control. Because the state of traffic and road are complex, so the control of ALV is complex and uncertain. Especially if the ALV runs in normal state of traffic, the control of ALV is becoming more complex and difficult. A good idea is that to let the control system of ALV to simulate human driver and develop a machine-leaning system in the control system of ALV. So that as the control system of ALV is driving ALV along road, the control system can learn from the experience of human driver according to the state of traffic and road. In other words, the control system of ALV is able to become more and more 'clever.' Of course it is a challenging and very difficult task. This paper analyzes the principle of machine-leaning system used for ALV and discusses the engineering method of developing a machine- leaning system used for ALV, when the ALV runs along highway in normal traffic. This paper advances the administrative levels of machine-leaning system and a method of fusing human intelligence into machine intelligence. This paper introduces our preliminary research on machine-leaning system used for ALV also, which is a kind of online machine-leaning system without teacher.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.