Showing papers by "Xi'an Jiaotong University published in 2001"
TL;DR: A new amending algorithm, poly-item cosine window interpolation, which is based on the interpolating algorithm proposed by V. Jain and T Grandke is presented, which improves the accuracy of the FFT, so it can be applied to the precision analysis for electrical harmonics.
Abstract: The fast Fourier transform (FFT) cannot be directly used in the harmonic analysis of an electric power system because of its higher errors, especially the phase error. This paper discusses the leakage phenomenon of FFT and presents a new amending algorithm, poly-item cosine window interpolation, which is based on the interpolating algorithm proposed by V. Jain and T Grandke. This new algorithm improves the accuracy of the FFT, so it can be applied to the precision analysis for electrical harmonics. The simulation result shows that applying different windows has different effects on the accuracy, and the Blackman-Harris window has the highest accuracy.
270 citations
16 Dec 2001
TL;DR: In this paper, a pseudo-random bit generator based on a couple of chaotic systems called CCS-PRBG is presented, and detailed theoretical analyses show that it has perfect cryptographic properties, and can be used to construct stream ciphers with higher security than other chaotic systems.
Abstract: Chaotic cryptology is widely investigated recently. This paper reviews the progress in this area and points out some existent problems in digital chaotic ciphers. As a comprehensive solution to these problems, a novel pseudo-random bit generator based on a couple of chaotic systems called CCS-PRBG is presented. Detailed theoretical analyses show that it has perfect cryptographic properties, and can be used to construct stream ciphers with higher security than other chaotic ciphers. Some experiments are made for confirmation. Finally, several examples of stream ciphers based on digital CCS-PRBG are given, and their security is discussed.
248 citations
TL;DR: In this paper, the formation of AlN thin films successfully deposited on Si(111) substrates by using the direct current magnetron sputtering method was studied, and the effects of the sputtering pressure, sputtering power and distance from the target to the substrate on the preferential orientation of the AlN films were also studied.
228 citations
TL;DR: The existence of positive solutions for the three-point boundary value problem u″ + a(t)f(u)= 0, u(0)=0,u(1) − αu(ν)=b is established.
178 citations
TL;DR: In this article, a hybrid control approach for the series active power filter (APF) is proposed, where the reference signal of the compensation voltage needed by the series APF is obtained by detecting both source current and load voltage.
Abstract: The series active power filter (APF) is suitable for compensating a voltage type harmonics-producing load, whereas the control approach it adopts may directly influence its compensation characteristics. This paper first discusses the control approach of detecting source current in terms of the basic operation principle of a series APF, then developing a control approach of detecting load voltage. On the basis of these, a hybrid control approach is proposed. In this approach, the reference signal of the compensation voltage needed by the series APF is obtained by detecting both source current and load voltage. Thus, this approach has the advantages of the first and the second control approaches and, at the same time, it can overcome their respective drawbacks. For practical realization, the control methods of the PWM inverter in the series APF and for regulating its DC side voltage are discussed in detail. A prototype of the series APF is manufactured and corresponding experimental investigation is done. The results show that when the series APF, if adopting the hybrid control approach instead of the other two, compensates for the voltage type harmonics-producing load, its performance can be improved greatly.
168 citations
TL;DR: A novel approach for stability analysis of neural networks is developed with a new concept called nonlinear measure introduced to quantify stability of nonlinear systems in the way similar to the matrix measure for stability of linear systems.
Abstract: In this paper, a new concept called nonlinear measure is introduced to quantify stability of nonlinear systems in the way similar to the matrix measure for stability of linear systems. Based on the new concept, a novel approach for stability analysis of neural networks is developed. With this approach, a series of new sufficient conditions for global and local exponential stability of Hopfield type neural networks is presented, which generalizes those existing results. By means of the introduced nonlinear measure, the exponential convergence rate of the neural networks to stable equilibrium point is estimated, and, for local stability, the attraction region of the stable equilibrium point is characterized. The developed approach can be generalized to stability analysis of other general nonlinear systems.
145 citations
TL;DR: In this paper, the phase velocity equations of the Love wave propagation and the stress fields in the layered piezoelectric structure are obtained for electrical open and short cases on the free surface, respectively.
142 citations
TL;DR: In this paper, fractional pressure drops of single-phase water and steam-water two-phase flows were studied in a pressure range of 3.0-3.5 Mpa.
142 citations
07 Jul 2001
TL;DR: An example-based facial sketch system that automatically generates a sketch from an input image, by learning from example sketches drawn with a particular style by an artist, using a non-parametric sampling method and a flexible sketch model.
Abstract: In this paper, we present an example-based facial sketch system. Our system automatically generates a sketch from an input image, by learning from example sketches drawn with a particular style by an artist. There are two key elements in our system: a non-parametric sampling method and a flexible sketch model. Given an input image pixel and its neighborhood, the conditional distribution of a sketch point is computed by querying the examples and finding all similar neighborhoods. An "expected sketch image" is then drawn from the distribution to reflect the drawing style. Finally, facial sketches are obtained by incorporating the sketch model. Experimental results demonstrate the effectiveness of our techniques.
141 citations
TL;DR: Four modifications of a predator prey model to include an SIS or SIR parasitic infection are developed and analyzed and global stability results are proved.
140 citations
TL;DR: This Letter points out why the original chaotic encryption scheme is so vulnerable to the proposed four attacks, and presents an improved encryption scheme to obtain higher security.
TL;DR: It is concluded that CMSP may be used not only as a kind of packing material in bio-affinity chromatography, but also as a tool for studying the interactions between a drug and its receptor.
Abstract: A new cell membrane stationary phase (CMSP) consisting of porous silica coated with active cell membranes is presented for affinity chromatography. By immersing, silica into a suspension of cell membranes, the whole surface of silica was covered by the cell membranes due to the irreversible adsorption of silanol groups (Si−OH) on the silica surface and the self-fusion of the cell membranes. CMSP can be used directly as a chromatographic packing material without any additional chemical modification. The surface characteristics, enzymatic activity, and chromatographic behavior of CMSP were investigated. The results obtained from scanning electron microscope, surface energy spectrometer, enzyme assay, and liquid chromatography showed that the surface characteristics of CMSP were very different from that of normal and reversed stationary phases. CMSP was found to have the characteristics of both cell membrane activity and chromatographic separation. Moreover, CMSP, as a chiral stationary phase, could be used for the enantiomeric separation of (±) Bay-K8644. The capacity factor of some calcium antagonists on CMSP was found to have a good correlation with their pharmacological actions. It is concluded that CMSP may be used not only as a kind of packing material in bio-affinity chromatography, but also as a tool for studying the interactions between a drug and its receptor.
TL;DR: It is concluded that it is very important to consider the anisotropic property of the porcine heart valves in order to understand the failure mechanism of such valves in vivo.
TL;DR: This paper is concerned with filled function techniques for unconstrained global minimization of a continuous function of several variables that have either one or two adjustable parameters.
Abstract: This paper is concerned with filled function techniques for unconstrained global minimization of a continuous function of several variables. More general forms of filled functions are presented for smooth and non-smooth optimization problems. These functions have either one or two adjustable parameters. Conditions on functions and on the values of parameters are given so that the constructed functions have the desired properties of filled functions.
TL;DR: It was revealed that the dissolution and bond strength degradation of the coatings were much lower than those of the plasma-sprayed HA coatings and were free of an amorphous phase.
Abstract: Hydroxyapatite (HA) coatings on titanium alloy substrates were prepared by an alkaline treatment of electrodeposited precursors. The structure, residual stress, and bond strength of the coatings were investigated. Test results showed that the coatings processed in this study exhibited fairly low tensile residual stress, high crystallinity, and were free of an amorphous phase. The bond strength of the coatings increased with the decrease of current density in the range of 0.2-15 mA/cm(2), and reached 14 MPa at 0.2 mA/cm(2). Evaluation of the coatings was performed together with the evaluation of the plasma-sprayed HA coatings immersed in distilled water. It was revealed that the dissolution and bond strength degradation of the coatings were much lower than those of the plasma-sprayed HA coatings.
TL;DR: In this article, a new network structure is proposed in which internal water mains are utilized to simplify the piping network, as well as the operation and control of large plants involving many water-using processes, such as petrochemical or chemical complexes.
Abstract: A new network structure is proposed in which internal water mains are utilized. The structure simplifies the piping network, as well as the operation and control of large plants involving many water-using processes, such as petrochemical or chemical complexes. It is accompanied by a new design procedure to generate networks having internal water mains, limited to a single contaminant with water reuse permitted, involving mass balances only and simple strategies for water minimization. Emphasis is placed on positioning of the internal water mains to simplify the networks, with the first internal main usually positioned at the pinch concentration. Strategies to reduce water consumption, through the use of local pipes and outlet concentration shifts, are discussed.
TL;DR: Practice shows that this new method for identifying flow regimes of multiphase flow has the merits of high accuracy, fast response and automatic identification without artificial intervention etc.
TL;DR: In this article, the mechanical properties of single-walled carbon nanotubes (SWCNTs) were computed and simulated by using molecular dynamics (MD) in order to obtain the Young modulus and tensile strength of SWCNT.
TL;DR: In this article, the authors present the results of an experimental study that was carried out to determine turbulent friction and heat transfer characteristics of four spirally corrugated tubes, which have various geometrical parameters, with water and oil as the working fluids.
24 Oct 2001
TL;DR: An approach for automatically segmenting sequences of natural activities into atomic sections and clustering them and extracting lexicon from these discrete sequences by using an algorithm named COMPRESSIVE is presented.
Abstract: Recognition of human gestures is important for analysis and indexing of video. To recognize human gestures on video, generally a large number of training examples for each individual gesture must be collected. This is a labor-intensive and error-prone process and is only feasible for a limited set of gestures. In this paper, we present an approach for automatically segmenting sequences of natural activities into atomic sections and clustering them. Our work is inspired by natural language processing where words are extracted from long sentences. We extract primitive gestures from sequences of human motion. Our approach contains two steps. First, the sequences of human motion are segmented into atomic components and clustered using a Hidden Markov Model. Thus we can represent the original sequences by discrete symbols. Then we extract lexicon from these discrete sequences by using an algorithm named COMPRESSIVE. Experimental results on music conducting gestures demonstrate the effectiveness of our approach.
TL;DR: The analytic methods proposed in this paper can be essentially extended to a large number of PLCM-s, and will be valuable for the research on the performance of such maps in chaotic cryptography and pseudo-random coding.
Abstract: The applications of digital chaotic maps in discrete-time chaotic cryptography and pseudo-random coding are widely studied recently. However, the statistical properties of digital chaotic maps are rather different from the continuous ones, which impedes the theoretical analyses of the digital chaotic ciphers and pseudo-random coding. This paper detailedly investigates the statistical properties of a class of digital piecewise linear chaotic map (PLCM), and rigorously proves some useful results. Based on the proved results, we further discuss some notable problems in chaotic cryptography and pseudo-random coding employing digital PLCM-s. Since the analytic methods proposed in this paper can essentially extended to a large number of PLCM-s, they will be valuable for the research on the performance of such maps in chaotic cryptography and pseudo-random coding.
TL;DR: In this article, a combustion front quenching method was used for investigating the mechanism of self-propagating high-temperature synthesis of NiAl from Ni and Al powders.
TL;DR: In this paper, a layered composite structure has been developed by plasma nitriding and plasma-enhanced CVD in order to improve the adhesion behavior of TiN coatings deposited on H13 steel.
Abstract: In order to improve the adhesion behavior of TiN coatings deposited on H13 steel, a layered composite structure has been developed by plasma nitriding and plasma-enhanced CVD in the present studies. Effects of the nitriding process on the microstructure, adhesion and microhardness, as well as the residual stress of composite nitrided H13/TiN coatings were investigated. Experimental results showed that the adhesion of TiN coatings to substrate could be remarkably enhanced by an optimized plasma nitriding process conducted at a 25% flow ratio of N2/(H2+N2) for 1 h. The formation of a new compound layer during a nitriding process at a 50% flow ratio of N2/(H2+N2) deteriorates the adhesion of TiN coatings due to premature brittle fracture between the coating and the substrate. The surface hardness of nitrided H13/TiN coatings and compressive residual stress in the diffusion interlayer increase with increasing pre-nitriding time, but the adhesion of the coatings decreases to some extent.
TL;DR: In this article, the wear and abrasion behavior of particles on Ti-6Al-4V coated with diamond-like carbon (DLC) were appropriately simulated by fretting wear and nano-scratch test.
TL;DR: In this article, the local heat transfer and pressure drop characteristics of developing turbulent flows of air in three stationary ribbed square ducts have been investigated experimentally, and the results show that the divergent duct has the highest heat transfer performance, while the convergent has the lowest.
15 Nov 2001-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Tensile tests and symmetrical push-pull fatigue tests were carried out with samples of commercially pure titanium and Ti-5Al-2.5Sn at 293 and 77 K, respectively as mentioned in this paper.
Abstract: Tensile tests and symmetrical push–pull fatigue tests were carried out with samples of commercially pure titanium and Ti–5Al–2.5Sn at 293 and 77 K, respectively. The microstructures were examined in detail by transmission electron microscopy. Pure titanium shows higher strength and ductility, longer low-cycle fatigue life at 77 K than at 293 K. Fatigue life of Ti–5Al–2.5Sn alloy keeps almost same with temperature decreasing. Pure titanium exhibits complex cyclic hardening/softening behavior at room temperature, while cyclic hardening is observed at 77 K. Ti–5Al–2.5Sn alloy cyclically softens at 293 K irrespective of strain amplitudes, and shows approximate saturation stage in peak stress besides the initial softening at low strain amplitudes with temperature decreasing to 77 K. Slipping predominates in monotonic deformation of both pure titanium and Ti–5Al–2.5Sn alloy at 293 K, while in cyclic deformation both slipping and twinning take place. Twinning becomes the main deformation mode in pure titanium at 77 K, and for Ti–5Al–2.5Sn alloy, twinning was also observed to operate in deformation at 77 K. Three types of twinning, { 10 1 2 }, { 10 1 1 }, { 11 2 2 }, were identified in pure titanium and in Ti–5Al–2.5Sn alloy as well.
TL;DR: According to the adaptive noise canceling technology in signal processing, an adaptive detecting approach of harmonic current based on a neuron is presented and the realization scheme of an analog circuit of the APF system is discussed.
Abstract: There have been a number of harmonic current detecting methods for the active power filter (APF), including the filtration approach by fixed frequency filters, the composition method of the imaginary and the real power based on the instantaneous reactive power theory, etc. In this paper, firstly, according to the adaptive noise canceling technology in signal processing, an adaptive detecting approach of harmonic current based on a neuron is presented. Then, on the basis of the configuration and learning algorithm for the developed system, the realization scheme of an analog circuit of the system is discussed. Thirdly, using PSPICE software, computer simulation studies of the circuit are performed. Finally, experimental studies are carried out. The performance and feasibility of the approach are tested and verified by the simulation and experimental results.
TL;DR: In this paper, the effect of humidity on the friction and wear of these sulfur-deficient MoSx coatings with different crystallographic orientations was discussed, and the effect was shown to be independent of the crystal orientation of the coatings.
TL;DR: In this paper, a non-linear coupled lateral torsional vibration model of rotor-bearing-gear coupling system is developed based on the engagement conditions of gear couplings, and the authors show that the forces and moments acting on gear coupling due to the initial misalignment are from the inertia forces of the sleeve and the internal damping between the meshing teeth.
TL;DR: In this paper, the penetration depth of the Bleustein-Gulyaev (B-G) wave in a layered half-space with identical piezoelectric layer and substrate but in opposite polarization was investigated.