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Showing papers by "National University of Defense Technology published in 2001"


Journal ArticleDOI
TL;DR: A two-dimensional (2-D) integer discrete cosine transform is proposed, which needs only integer operations and shifts and is nonseparable and requires a far fewer number of operations than that used by the corresponding row-column 2-D integer discrete Cosine transform.
Abstract: A method is proposed to factor the type-II discrete cosine transform (DCT-II) into lifting steps and additions. After approximating the lifting matrices, we get a new type-II integer discrete cosine transform (IntDCT-II) that is float-point multiplication free. Based on the relationships among the various types of DCTs, we can generally factor any DCTs into lifting steps and additions and then get four types of integer DCTs, which need no float-point multiplications. By combining the polynomial transform and the one-dimensional (1-D) integer cosine transform, a two-dimensional (2-D) integer discrete cosine transform is proposed. The proposed transform needs only integer operations and shifts. Furthermore, it is nonseparable and requires a far fewer number of operations than that used by the corresponding row-column 2-D integer discrete cosine transform.

83 citations


Journal ArticleDOI
TL;DR: In this article, an inexpensive method to prepare the pure mullite whiskers from natural topaz has been introduced, and XRD and SEM were used to analyse the structure and morphology of the whiskers.

48 citations


Proceedings ArticleDOI
07 Oct 2001
TL;DR: In this paper, a new symmetric biorthogonal 9/7-tap wavelet called LS97 was proposed based on a lifting scheme and the construction theorem of BER wavelets.
Abstract: Based on a lifting scheme and the construction theorem of biorthogonal wavelets, we propose a new symmetric biorthogonal 9/7-tap wavelet called LS97. Compared to Cohen-Daubechies-Feauveau 9/7-tap (CDF 9/7-tap) wavelet adopted by JPEG2000, when the new wavelet is applied to image coding, the compression performance is exactly the same as that of the CDF 9/7-tap wavelet, while computational complexity is reduced remarkably.

45 citations


Journal ArticleDOI
TL;DR: In this paper, a novel coplanar waveguide with photonic bandgap structure is proposed and is implemented by etching holes in the ground plane with an open connected with the gap between strip line and ground plane.
Abstract: A novel coplanar waveguide with photonic bandgap structure is proposed and is implemented by etching holes in the ground plane with an open connected with the gap between strip line and ground plane. Simulation and measurement results show the existence of a bandgap.

41 citations


Journal ArticleDOI
TL;DR: The theoretical result reproduces all structures shown in the experiment, whereas some of the structures near the higher energy edge did not show up in some other opacity models not attributed to the detailed treatment of the photoionization process.
Abstract: An extensive configuration interaction (CI) scheme and the R-matrix method are combined to calculate the radiative opacity for laser-produced aluminum plasma in local thermodynamic equilibrium using the detailed-term-accounting (DTA) approximation. The CI scheme is used to obtain the absorption oscillator strengths of the electric dipole allowed transitions for evaluating the bound-bound absorption cross sections, and the R-matrix method is used to obtain the bound-free absorption (photoionization) cross sections. For an aluminum plasma at a temperature of 20 eV and the density of $0.01 \mathrm{g}/{\mathrm{cm}}^{3},$ the Rosseland and Planck mean opacities are calculated to be 4184 and $24891 {\mathrm{cm}}^{2}/\mathrm{g},$ respectively, by integrating the spectrally resolved opacities with Rosseland and Planck weighting functions. The two mean opacities are also obtained by using the average atom model, and they are 22520 and $30402 {\mathrm{cm}}^{2}/\mathrm{g},$ respectively. The optical transmission from the photon energy of 70--250 eV, which was experimentally measured by Winhart et al. [G. Winhart et al. Phys. Rev. E 53, R1332 (1996)], is also calculated. Generally good agreement is found between our DTA and experimental transmission. Our theoretical result reproduces all structures shown in the experiment, whereas some of the structures near the higher energy edge did not show up in some other opacity models. These structures are attributed to the detailed treatment of the photoionization process.

33 citations


Journal ArticleDOI
TL;DR: In this article, a formation of organic-inorganic hybrid precursor, polyvinyl butyral (PVB)/alumina sol, was investigated to make high quality coating on carbon fiber.

20 citations


Journal ArticleDOI
TL;DR: In this article, the authors used surface waveform inversion with an equal block (2°×2°) discretization to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper mantle.
Abstract: We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). It partitions the large-scale optimization problem into a number of independent small-scale problems. We adopted surface waveform inversion with an equal block (2°×2°) discretization in order to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper-mantle. The resolution of all these anomalies has been established with “check-board” resolution tests. These results show significant difference in velocity, lithosphere and asthenosphere structure between South China Sea and its adjacent regions.

20 citations


Proceedings ArticleDOI
25 Oct 2001
TL;DR: A color correction technique that constructs a mapping from the registered overlapped regions based on a color histogram is proposed that can efficiently correct the color difference between the two overlapping images.
Abstract: Colors need to be corrected to minimize the discrepancy in the appearance of adjacent images such as in the applications of panoramic images. In this paper, we proposed a color correction technique that constructs a mapping from the registered overlapped regions based on a color histogram. Since the color histogram can reflect the overall color distribution, experiments prove that it can efficiently correct the color difference between the two overlapping images.

17 citations


Journal ArticleDOI
01 Oct 2001
TL;DR: In this article, a novel passive location method was introduced with phase difference and phase difference rate measurements with the interferometer mounted on a moving observer, which showed a significantly improved performance compared with the traditional method.
Abstract: The interferometer is the traditional instrument used to find the direction of an emitter by measuring the phase difference of arrival of its RF emissions. Bearings-only motion analysis indicates that an observer with these direction measurements can locate the position of the emitter in a period of time. A novel passive location method is introduced with phase difference and phase difference rate measurements with the interferometer mounted on a moving observer. The accuracy of a passive location system with these measurements is analysed. The results show a significantly improved performance compared with the traditional method.

17 citations


Journal ArticleDOI
TL;DR: In this article, the microstructures of a 1D-C f /SiC composite, prepared by polymeric precursor pyrolysis and hot pressing, with polycarbosilane (PCS) as precursor and AlN-Y 2 O 3 as sintering additives, were investigated by using XRD, HRTEM, and SEM.

13 citations


Journal ArticleDOI
TL;DR: In this paper, a stiffness-based life-signal prognostic model of a bearing system based on vibration response analysis and damage mechanics is proposed to predict the failure lifetime of bearing systems.
Abstract: Bearing failure is one of the foremost causes of breakdown in rotating machinery. In this paper, a stiffness-based life-signal prognostic model of a bearing system based on vibration response analysis and damage mechanics is proposed. When a bearing system is simplified as a Single-DOF vibration system, the natural frequency of the system is proportional to the system stiffness, and the amplitude of acceleration response at the natural frequency is opposite to the system stiffness. Meanwhile, for the rules of damage mechanics, the relationship among failure lifetime, running time and variations of stiffness of a bearing system can be established. With the combination of above two relationships, the natural frequency and the amplitude of acceleration response at the natural frequency are related to the running time and failure life-time. Thus, the failure lifetime of a bearing system can be predicted via vibration signals from an accelerometer, which is attached to the bearing housing. The resulting model ...

Proceedings ArticleDOI
21 May 2001
TL;DR: This paper proposes a new method to control the compliant motion of robot manipulator: the position/force control with self-adjusting select-matrix, which has the advantage of accurate hybrid control results, as well as the disadvantage of impedance control for not using the explicit switch between the force control mode and position control mode.
Abstract: In order to do the complex contact task, the robot manipulator must have the force control ability. In this paper, we propose a new method to control the compliant motion of robot manipulator: the position/force control with self-adjusting select-matrix. This method not only uses force information in feedback loop, but also uses it in the select matrix, to let controller automatic switch between the force control mode and position control mode. Thus, this method has the advantage of accurate hybrid control results, as well as the advantage of impedance control for not using the explicit switch between the force control mode and position control mode. Experimental results verify the theory and confirm the effectiveness of the method.

Journal ArticleDOI
TL;DR: In this paper, the spectral resolved opacities of high-power laser-produced plasmas in local thermodynamic equilibrium (LTE) were calculated at the temperatures and densities of 40 eV and 0.0135 g/cm3.
Abstract: The detailed term accounting (DTA) approximation for the line absorption and the average atom (AA) model for bound-free and free-free absorption are used to calculate the radiative opacity of high-power laser-produced plasmas in local thermodynamic equilibrium (LTE). The spectral resolved opacities of Al plasmas are calculated at the temperatures and densities of 40 eV and 0.0135 g/cm3, and 58 eV and 0.02 g/cm3. Rosseland and Planck mean opacities are obtained by integrating the spectral resolved opacities with Rosseland and Planck weighting functions. The results show that the Rosseland mean opacity is very sensitive to the detailed profile. Radiative opacities under the same plasma conditions are also obtained by using a completely pure AA model. The results from the DTA and pure AA models are then compared.

01 Jan 2001
TL;DR: The experimental results have shown that the proposed method can simplify the adjustment of the system structure, shorten the time needed for system re training, and thus improve the system training efficiency.
Abstract: In this paper,a neural network group is defined for BP NN based classification systems.Then an adaptive algorithm for system growth is brought out,with which the system structure can be adjusted adaptively when new target class is added to the system.The experimental results have shown that when adding a new target class,the proposed method can simplify the adjustment of the system structure,shorten the time needed for system re training,and thus improve the system training efficiency.


Journal ArticleDOI
TL;DR: In this article, polycarbosilane (PCS) was modified by adding 1 wt% polyborazine and subsequent heat treatment at 70-400 °C for 10 h.
Abstract: Polycarbosilane (PCS) was modified by addition of 1 wt% polyborazine and subsequent heat treatment at 70-400 °C. The modified PCS exhibited highly improved ceramic yield from original 63% to 78% by heating at 70 °C for 10 h. The molecular weight of the PCS modified at higher temperatures markedly increased, then was rendered infusible but soluble PCS in organic solvent on heating at 300 °C. H-NMR indicated that original PCS was enhanced by dehydrocoupling reaction between Si-H groups. Solution of the modified PCS was hand-drawn to fibers, followed by direct pyrolysis up to 1,400 °C without air-curing step to convert into oxygen-free SiC fibers. The morphology and crystalline phase were determined by SEM and XRD analysis, respectively.

Book ChapterDOI
24 Oct 2001
TL;DR: After reviewing some statistical models which have been proposed to better characterize the DCT coefficients of images, a new blind watermark detector is deduced -- sign correlation detector (SCD) based on the Laplacian distribution model.
Abstract: Digital watermarking is a key technique for protecting intellectual property of digital media. Due to the ability to detect watermark without the original image, blind watermarking is very useful if there are too many images to be authenticated. In this paper, we pose the difference on mathematical models between private watermark detection and blind watermark detection, and then point out the limitation of linear correlation detector (LCD). After reviewing some statistical models which have been proposed to better characterize the DCT coefficients of images, we deduce a new blind watermark detector -- sign correlation detector (SCD) based on the Laplacian distribution model. Computing result of asymptotic relative efficiency demonstrates the effectiveness of the detector. A series of experiments show its robustness.

01 Jan 2001
TL;DR: Within the framework of Dempster Shafer theory of evidence, a combination rule based on proportional belief assignment is presented in order to solve conflict evidence combination in identification fusion and is superior to the existing approaches in terms of robustness via several simulations.
Abstract: Within the framework of Dempster Shafer theory of evidence,a combination rule based on proportional belief assignment is presented in order to solve conflict evidence combination in identification fusion.The order of combination is defined based on comparability.Comparison of our method with the existing algorithms demonstrates that our algorithm is superior to the existing approaches in terms of robustness via several simulations.

Journal ArticleDOI
01 Feb 2001
TL;DR: The paper shows that the type-II r-dimensional discrete cosine transform (rD-DCT-II) can be converted into a series of one-dimensional reduced DCT-IIs by using the polynomial transform, which has a significantly reduced number of multiplications compared to that needed by the row–column method.
Abstract: The paper shows that the type-II r-dimensional discrete cosine transform (rD-DCT-II) of size ql1×ql2×· · ·×qlr, where r>1 and q is an odd prime number, can be converted into a series of one-dimensional reduced DCT-IIs by using the polynomial transform. The number of multiplications for computing an rD-DCT-II is significantly reduced compared to that needed by the row–column method. The total number of arithmetic operations (additions plus multiplications) needed by the proposed algorithm is also reduced substantially. In addition to the capability of dealing with different dimensional sizes, the proposed algorithm also has a simple computational structure because it requires only the 1D-DCT-II and the polynomial transform.

Journal ArticleDOI
TL;DR: In this paper, an approximation equation for the pressure p and temperature T dependence of thermal conductivity K for nonmetal crystals is developed, where the common used empirical equations K T = A 1 + B 1 p and K p = A 2 + B 2 / T at low pressures and low temperatures, respectively, are deduced from the equation, where A 1, B 1, A 2 and B 2 are empirical constants and the subscripts T and p refer to isothermal and isobaric processes, respectively.

Journal ArticleDOI
TL;DR: In this paper, the photoionization cross sections of N-like Al VII were calculated from the first ionization threshold to 140 Ry using the R-matrix method and the detailed structure and resonances of the cross sections across the L-shell and K-shell thresholds were described.
Abstract: The photoionization cross sections of N-like Al VII are calculated from the first ionization threshold to 140 Ry using the R-matrix method. 14 target states (including 4 K-shell excited states) of Al VIII are included in the close-coupling calculation. The detailed structure and resonances of the cross sections across the L-shell and K-shell thresholds is described. The resonance energies and widths of some of the autoionization states are determined by analyzing the resonance structures. The results show that the autoionization width of the K-shell excited state of a $1s$ electron being excited into $2p$ orbital is the largest among all of the autoionization states. It is also larger than Doppler and Stark widths under a typical plasma condition. This result shows that the autoionization widths will have essential influence in simulating the x-ray transmission spectrum of Al plasma.

Journal ArticleDOI
TL;DR: A verifier of UML Statecharts is developed by using the model checker SMV to transform a system model in UML statecharts to one in SMV input language via an intermediate language and then to verify the system properties specified in CTL by invoking SMV.
Abstract: Formal verification has been widely needed in the development of safety critical systems. In order to introduce the design verification activity in UML developing process, we have developed a verifier of UML Statecharts by using the model checker SMV. The approach is to transform a system model in UML Statecharts to one in SMV input language via an intermediate language and then to verify the system properties specified in CTL by invoking SMV. The current experiences, including the formal verification of a simplified directory based cache coherence protocol in UML Statecharts, show that automatic verification can be integrated as a new step of the software process nicely.

Journal ArticleDOI
TL;DR: This paper first presents a fastW-transform (FWT) algorithm for computing one-dimensional cyclic and skew-cyclic convolutions, and by using this FWT in conjunction with the fast polynomial transform (FPT), an efficient algorithm is proposed for calculating the 2D cyclic convolution (2D CC).
Abstract: This paper first presents a fastW-transform (FWT) algorithm for computing one-dimensional cyclic and skew-cyclic convolutions. By using this FWT in conjunction with the fast polynomial transform (FPT), an efficient algorithm is then proposed for calculating the two-dimensional cyclic convolution (2D CC). Compared to the conventional row-column 2D discrete Fourier transform algorithm or the FPT Fast Fourier transform algorithm for 2D CC, the proposed algorithm achieves 65% or 40% savings in the number of multiplications, respectively. The number of additions required is also reduced considerably.

Journal ArticleDOI
TL;DR: The Chebyshev method provides a quick, accurate and direct estimation of two prime parameters in sediment transport dynamics.

Proceedings ArticleDOI
15 Oct 2001
TL;DR: In this paper, a coherent scattering model is presented to depict the polarization scattering process of chaff cloud in outer space instead of the traditional non-coherent model, which is used to meet the increasing need of modern ballistic missile countermeasure.
Abstract: To meet the increasing need of modern ballistic missile countermeasure, it becomes more and more important to study chaff cloud's scattering characteristics in outer space more accurately. A coherent scattering model is presented to depict the polarization scattering process of chaff cloud in outer space instead of the traditional noncoherent model. Chaff cloud's polarization scattering matrix and RCS formulae are derived. These formulae reflect the fluctuation law of chaff cloud's RCS due to the variation of cloud's spatial distribution.

01 Jan 2001
TL;DR: A collaborative design methodology based on CVP is presented, which can flexiblely and comprehensively support collaborative design and fully test and verify the product's function and performance before its really design, manufacture and application.
Abstract: :Collaborative virtual prototyping (CVP) is the approach and technique used by multi-displinary experts to build and apply virtual prototype in a distributed environment. This paper analyzes the relationship between CVP and collaborative design, and presents a collaborative design methodology based on CVP, which can flexiblely and comprehensively support collaborative design. The methodology can fully test and verify the product's function and performance before its really design, manufacture and application. The paper also presents CVP modeling method and heterogeneous simulation method, and presents the architecture of the CVP based collaborative design environment.

Journal Article
TL;DR: In this article, a model is established and weight functions are given for robust batch processor in satellite precision orbit determination, which can give the best estimation results from normal observations by making full use of effective observations, finding limitations of useable observations and eliminating deleterious gross errors.
Abstract: In this paper, a model is established and weight functions are given for robust batch processor in satellite precision orbit determination. The effects no robustuess weight functions. It is shown that the robust batch processor can give the best esti mate results from normal observations by making full use of effective observations, finding limitations of useable observations and eliminating deleterious gross errors. The robust computations steps are also given. Finally, satellite laser ranging (SLR) data of satellite Lageos were processed, the satellite orbit estimated from the robust estimation is more stable than that from least square estimation and this verifies the good robustness of robust batch processor in practice.

Journal Article
TL;DR: In this article, a non iterative method using rational polynomials approximation is introduced and through the compare with heikkinen, improved Bowring and Ozone methods is proved to be a very fast procedure as well as a method having an averageaccuracy of no more than 1 mm below 50 km.
Abstract: The computing of latitude is the key of geodetic coordinate transformation from geocentric coordinate which conventionally uses iterative methods and results in low efficiency and is hard to cope with most real time occasions. Inthis paper, a non iterative method using rational polynomials approximation is introduced and through the compare with heikkinen,improved Bowring and Ozone methods is proved to be a very fast procedure as well as a method having an averageaccuracy of no more than 1 mm below 50 km.

Journal Article
TL;DR: In this paper, the present situation of the research on the RIM FOS (reflective intensity modulated fiber optic sensor) is summarized and some key problems those limit the application of RIMFOS are proposed and approaches to solve them are also put forward.
Abstract: The present situation of the research on the RIM FOS (reflective intensity modulated fiber optic sensor) is summarized. Some key problems those limit the application of RIM FOS are proposed and approaches to solve them are also put forward.

Proceedings ArticleDOI
26 Nov 2001
TL;DR: This method bases on multi-level threshold decision-making and sliding trajectory confidence testing technology, which resolves the contrary requirement of real-time processing, large date throughput, high detection capability in small moving target detection in IR image sequences.
Abstract: This paper describes a new method of small target detection according to the features of small moving targets. This method bases on multi-level threshold decision-making and sliding trajectory confidence testing technology. Energy accumulating, multi-level thresholding, trajectory searching and matching, and trajectory confidence testing are combined in this method. The detection resolves the contrary requirement of real-time processing, large date throughput, high detection capability in small moving target detection in IR image sequences. Experiments have been conducted, the results show that the algorithm has advantages of high detection probability, simple structure, and excellent real time performance.