最新刊期
卷 31 ， 期 3 ， 2003
- 摘要：Symmetry is a powerful tool to reduce the number of degrees of freedom of a problem.But calculating the symmetry of a high-dimensional system would be very difficult since the total number of transformations increases dramatically with the dimension of the system,which places many restrictions on the application of the symmetry method.A novel approach based on genetic algorithms is proposed to search for the permutation symmetries of the weight matrix of full-connected neural networks within the symmetry group Sn.Searching results for several different dimensional matrixes are given and compared to that of the ergodic searching method.It turns out that the searching method based on genetic algorithms can find the majority of symmetric permutations of the matrix within a short time,which makes it possible to study and design of the high-dimensional neural networks by the symmetry tool.关键词：neural networks;symmetric permutation;genetic algorithms;weight matrix2|1149|0更新时间：2025-07-16
- 摘要：The near field scattering of the complex metal structures in the vicinity of an antenna array will cause serious distortion of the antenna array pattern.A scheme utilizing the broadened first-order Bragg lines to compensate the distortion of the antenna array pattern is presented and the Total-Least-Square (TLS) technique used to estimate the element error-response pattern is described.The result of simulation to the error-response pattern of the antenna array shows that the TLS method is available and optimal in the estimation of the antenna array pattern in HF ship-born over-the-horizon radar environment.关键词：sea-clutter;antenna pattern;error response2|923|1更新时间：2025-07-16
- 摘要：The constant modulus algorithm(CMA) is suffered from the complex iteration computation and the analytical CMA (ACMA)is limited with resolvable source number.After analyzing the ACMA,a space-time ACMA is proposed to achieve blind source separation in CDMA smart antenna systems.By extending the traditional CMA only in time domain or in space domain to the space-time domain,the analytical solution is obtained with several joint approximate diagonalization of eigen-matrices,and converts the problem of solving the blind beamforming weigh to signal subspace.Numerical simulations illustrate that the proposed approach can overcome the limitation to the number of sources,and efficiently reduce the multiple access interference (MAI).关键词：space-time analytical CMA;smart antenna system;blind source separation;space-time signal processing2|979|0更新时间：2025-07-16
- 摘要：Too much time is needed for EMC analysis of complicated EM environment.To overcome this drawback,a parallel algorithm which combined UTD and MPI function is presented in this paper,and the radiation pattern of airborne antennas is analyzed with this method.Numerical results show that parallel UTD algorithm can drastically reduce the computing time.This method provides a solid foundation for complex EMC software on small computer system.关键词：parallel UTD algorithm;MPI;airborne antenna;radiation pattern2|1196|8更新时间：2025-07-16
- 摘要：The characteristic of the pass through resonance cavity is studied in this paper,which distinguishes itself from the traditional parallel connection resonance model.This paper also gives the Q equations of pass through resonance cavity,which is similar to the result obtained by perturbation method or complex frequency method.This process is the theoretical basis of measuring Q by half power points method in microwave engineering.关键词：parallel connection resonance model;pass-through resonance cavity;3dB-Q2|1497|2更新时间：2025-07-16
- 摘要：The high-power microwave devices filled with plasma have unique properties.One of the major problems associated with plasma-filled microwave sources is that ions from the plasma drift toward the gun regions of the tube.This bombardment is particularly dangerous for the gun,where high-energy ion impacts can damage the cathode surface and degrade its electron emission capabilities.One of the techniques investigated to mitigate this issue is to replace the material cathode with plasma cathode.A unique plasma cathode electron gun are investigated experimentally.The PCE-gun has been operated at pulser voltage up to 8kV,discharge current up to 140A,and pulse lengths up to 60 μs.关键词：electron gun;plasma;cathode;experimental study;electron beam2|1485|2更新时间：2025-07-16
- 摘要：To meet the new higher requirements from remote sensing development,radar altimeter is being extended to more challenging applications,such as land survey and sea ice survey.So,radar altimeter must be adaptive to complex environments and one of the keys is how to build a kind of robust tracking algorithm,which is quite different from those for ocean applications.In the context,as a basis of studying robust tracking algorithm,following general analysis of radar altimeter echo,OCOG algorithm will be introduced.Through theorelical analysis and emulation test,OCOG is justified to be an excellent robust tracking algorithm for radar altimeter,and its shortcomings is also discussed.Thus it may help the following advanced studies on robust radar altimeter tracking algorithm design.关键词：altimeter;robust;tracking;algorithm2|1313|4更新时间：2025-07-16
- 摘要：SAR obtains high azimuth resolution through synthetic aperture integration and high range resolution via pulse compression.Stepped-frequency waveform achieves large bandwidth by sequentially changing carrier frequency over pulses.In order to obtain high resolution in two dimensions,we try to apply stepped-frequency waveform to SAR system.First,the effect of radial velocity on synthetic range profile is discussed,then the return of stepped-frequency SAR is presented.Furthermore,the waveform design is discussed,and the method of SAR imaging is given.2|1931|4更新时间：2025-07-16
- 摘要：Theoretical analysis demonstrates that wideband signal can not be transmitted by using narrowband phased array in scenarios with large aperture and scan angle.Two wideband transmitting beamforming methods for phased radar based on the known waveform in the presence of large scan angle are proposed.The diagrams are given,and simulation results show the effectiveness of two methods.The novel methods employ digital processing in the time domain and are optimal.Compared with the beamforming method utilizing FIR filter consisting of tapped delay lines in the time domain and the beamforming technique with DFT in the frequency domain,the presented methods demand the smaller number of equipment and are easy to be implemented in engineering.关键词：large scan angle;wideband beamforming;phased array2|1541|10更新时间：2025-07-16
- 摘要：To improve the performance of tracking the objects in lower altitude or on the ground,a new algorithm for TMTP is provided in this paper,which uses more perfect information than the old ones.The architecture is introduced,some sub-algorithms are explained,and the approaches are discussed in detail.At the end,some items are analyzed which may affect the performance,and application result is given.关键词：TV objects tracking;image processing;algorithm2|950|0更新时间：2025-07-16
- 摘要：According to the time-varying circuit concept,signal and circuitry system theory,we establish a time-varying linear circuit model of two-diode sampler using Nose-To-Nose(NTN) calibration procedure in this paper,and derive expressions of kick-out pulse and the impulse response of the sampler in time domain,proving that kick-out pulse is a natural response of the sampling circuit in the NTN.A new data-processing method is presented to obtain the varying RC parameter from the kick-out pulses acquired for the determination of the impulse response of sampler of oscilloscope.The problem of diode junction capacitance effect on the NTN calibration can be solved.2|943|1更新时间：2025-07-16
- 摘要：A pixel-level multisensor image fusion algorithm based on false color is proposed and used to fuse two gray images.This method combines image fusion technique with color display technique and shows the detail differences between the gray fusion image and original images by different colors after obtaining a gray fusion image.There are three steps in this algorithm.First,a gray-level fusion image of two original images is obtained by the hybrid average and selection fusion technique.Then,two images showing differences between two original images and gray-level fusion image are generated.At last,these two images including differences and the gray-level fusion image are sent to R,G,B color channels respectively.Compared with the gray-level fusion image,the final color fusion image generated by this algorithm has more color variation,more details and the targets in it is easy to be recognized.关键词：pixel-level image fusion;gray fusion image;color fusion image;false color2|1562|6更新时间：2025-07-16
- 摘要：In this paper,the absorption of circularly polarized and the X-mode EM-wave by inhomogeneous magnetized plasmas is discussed,and the attenuations are calculated under different conditions.The results illustrate that the collisional absorption have a maximal value when the collision frequency is near the EM-wave frequency.Meanwhile,the absorption is very poor when the EM-wave frequency is small.The absorption is efficient with a high incident EM-wave frequency.We also find out that the magnetic fields have an influence upon the attenuations of EM-wave.For the right circularly polarized EM-wave,the peaks of the attenuation curves move to the low collision frequency,and the attenuations reduce when the magnetic field grows.For the left circularly polarized EM-wave,the peaks of the attenuation curves move to the high collision frequency,and the attenuations becomes large when the magnetic field reduces.And we find out that the effective frequency band width of absorption can be broadened under some conditions while the absorption of EM-wave have a maximum.This characteristic is remarkable when the EM-wave frequency is low.2|3773|16更新时间：2025-07-16
- 摘要：A congestion control model called Early Random Congestion Control Model(ERCCM)is proposed based on the analysis of Random Early Detection(RED) and the comparison of basic congestion control method in Transfer Control Protocol/Internet Protocol (TCP/IP) and Connection Oriented Transfer Protocol/Connectionless Network Protocol (COTP/CLNP).It is suitable for all kinds of networks with absolute threshold congestion control.A method called Random Early Marking (REM) is also presented for use in Aeronautical Telecommunication Network (ATN) based on the principle of ERCCM and RED.The REM simulation results show that it can apparently overcome the defect of the absolute threshold marking methods in ATN and improve the performance of the network.关键词：ATN;congestion control;CLNP;RED2|1145|0更新时间：2025-07-16
- 摘要：A refined frequency scaling algorithm for spaceborne spotlight synthetic aperture radar (SAR) imaging is presented.The algorithm can process dechirped raw data directly.Based on the squinted range equivalent model that is fitter for spaceborne geometrical relation than the broadside range model,the complete derivation of the algorithm is presented and the refined frequency scaling factors of each signal domain are given.The refined factors can process the secondary range compression more accurately and avoid that range bandwidth is aliased or shifted outside the processed bandwidth for squinted mode.The refined azimuth scaling factor can decease azimuth time expansion and improve efficiency of azimuth processing.Besides,in order to decrease very high pulse repetition frequency (PRF) and data rate of spaceborne spotlight SAR and alleviate the design difficulties of spaceborne system,a subaperture approach is introduced.The necessity and implementation of the subaperture approach are analyzed.Finally,the computer simulation shows the validity of the refined algorithm.关键词：SAR;radar imaging;frequency scaling algorithm;subaperture processing2|855|2更新时间：2025-07-16
- 摘要：Channel vector was estimated only by utilizing pilot channel in conventional 2-D RAKE receiver.The weights were further calculated to detect the symbol sequences in traffic channel.The estimation error will be large when the power of pilot is low.A novel algorithm was proposed in this paper.We employed pilot to get the initial channel vector in the first instance.Iterative least squares with projection algorithm was then used to estimate the channel and symbol sequences jointly.This algorithm is characterized by low computation complexity and rapid convergence rate.Computer simulation demonstrates that the algorithm has improved the system performance effectively compared with conventional 2-D RAKE receiver.关键词：2-D RAKE receiver;channel estimation;iterative least squares with projection2|685|0更新时间：2025-07-16
- 摘要：A secure electronic voting scheme based on anonymous communication channel is proposed by using group signature protocol and timed commitment protocol.The identity information of honest voters can be protected unconditionally while dishonest voters are sure to be traced by the trusted registration agent.We can also prove:Even the administrator and the counting agent conspire,the voting privacy and fairness can be realized simultaneously before the counting.Besides,we also solved the problems such as "vote collision","voter abstains from voting or quits midway" et al.关键词：electronic voting;group signature;timed commitment2|2133|10更新时间：2025-07-16
- 摘要：A multiwavelets-based code-division multiple-access (MW-CDMA) scheme is presented based on the application of recent results in multiwavelet filter,preprocessing and balancing to communications area.In MW-CDMA,at first,the received signal is decomposed into the components in the orthogonal wavelet spaces,and then the multiuser demodulation is implemented in each wavelet spaces.Theoretical analysis and experimental results show that MW-CDMA systems suppress multiple-access interference and ambient noise well.Moreover,the scheme gives a new guidline of thought to reduce the computation for demodulation.2|821|0更新时间：2025-07-16
- 摘要：A novel companding transform is proposed to reduce Peak-to-Average Power Ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals.This proposed technique can effectively reduce PAPR with low computational complexity.For practical applications,linear,nonlinear-symmetrical and nonlinear-quasi-symmetrical companding transform schemes are analyzed in terms of their companding effects,computational complexity,and improvement in BER performance in OFDM systems.It is shown by computer simulations that the proposed technique can outperform the conventional clipping-filtering scheme substantially.关键词：OFDM;PAPR;companding transform2|1783|7更新时间：2025-07-16
- 摘要：A new algorithm of text steganography is proposed.The main idea of the algorithm is to transform the text signal without redundancy into redundant signal.The text steganography is then implemented on the redundant signals.By using this algorithm,a secret text can be replaced by a pubilic text.The algorithm can survive from communication noise.关键词：text steganography;information hiding;redundancy2|1338|7更新时间：2025-07-16
- 摘要：Paralleling techniques play an important role to decrease circuits' frequency and to satisfy requirements of delay and power cost,and have wide applications in communication signal processing.For LRS,a universal (1,N) paralleling method is presented by discussions on the system state equation and the output equation.And the computing arithmetic is identical for arbitrary parallel number.And a novel method for (M,N) paralleling realization is also presented in some conditions.For NLRS,the definition is given at first,and the paralleling method of linearization matrix method is presented by linearizing states' transfer.For the non-linear shift register,a novel paralleling method called generalizing delay operator method is presented.2|932|4更新时间：2025-07-16
- 摘要：This paper firstly discusses the technique of stressed speech processing and its recent progress,and analyses the reasons for the degradation of recognition of speech under stress.Then the classification and the recognition methods of stressed speech are reviewed.Finally,the unsolved problems and the prospect in this field are pointed out.关键词：stressed speech;speech analysis;speech classification;robust speech recognition4|1737|2更新时间：2025-07-16
- 摘要：Supporting QoS is an important object in the next generation mobile Internet.However,enabling QoS in mobile environment is a tough venture.In this paper,we mainly discuss the various frameworks for QoS in next generation mobile Internet.We analyze the characteristics of each scheme and compare their performance.Finally,we point out the trend in this field and present some topics to be further studied.关键词：Quality of Service;integrated service;differentiated service;mobile internet2|1106|0更新时间：2025-07-16
- 摘要：A recursive total least lp-norm (RTLMP) algorithm is developed to recursively compute the total least lp-norm solution for adaptive finite impulse response(FIR) filters.Due to the existence of the non-Gaussian α-stable noise,the performance of signal processing algorithms designed under the Gaussian assumption may degrade seriously.In this paper,a new adaptive algorithm based on the classical power iteration is developed which can minimize the Lp norm of the error function.The performance of the algorithm is evaluated via simulations.It is shown that the new algorithm achieves superior convergence rate.关键词：alpha-stable noise;adaptive FIR filter;recursive total least lp-norm4|985|4更新时间：2025-07-16
- 摘要：The paper optimizes the pretreatment method of the matrix and the compositor method of the nods etc about the linear algebra equation group formed by full-implicit reservoir simulation and produce the best solution fitting for parallel on the base of deep reserch about iterative solution.At the base of optimized ORTHOMIN method,the two dimension two phase full-implicit model with muti-layers has been paralleled as coarse granularity.The calculating outcome of large scale reservoir simulation indicates that the paralleled muti-layer two dimension two phase model possesses upper parallel efficiency and meets the practical application demands of the oilfield.关键词：model;optimal;parallel;coarse granularity;parallel efficiency2|1430|0更新时间：2025-07-16
- 摘要：An on-line real-time tracking algorithm for radar image sequences is proposed.First,a GMM (Gaussian mixture model) is used to approximate values of a particular pixel of the radar image sequences,and parameters of the GMM are updated each time.Then,we use a simple heuristic to hypothesize which Gaussian of the mixture is most likely to be part of the adaptive background model.After the background model is established,pixel values that don't match the pixel's "background" Gaussians are grouped using connected components.Features of the targets such as center position,size,radial and angular velocities are also computed in the mean time.Finally,the connected components are tracked across frames using a Kalman filter-based tracker.The experimental result shows that the algorithm is robust in clutter and easy to implement on-line.关键词：track-while-scan;Gaussian mixture;connected component;kalman filter2|1247|1更新时间：2025-07-16
- 摘要：Two-pass spaceborne interferometric SAR is used to produce three-dimensional terrain map by estimating the unwrapped interferometric phase and transferring the phase into terrain height.Baseline is very important for spaceborne interferometric SAR system design and data processing.In this paper,spatial baseline in spaceborne interferometric SAR was analyzed in many aspects.The statistical correlation between two SAR images from different satellite passes was presented.Influences of baseline on range flat ground frequency and multilook processing were discussed.The equation to determine the optimal spatial baseline was deduced.Finally,the results of computer simulating were presented to testify the correction of analysis.关键词：baseline;spaceborne interferometric SAR;data processing;optimal;design2|1281|5更新时间：2025-07-16
- 摘要：An important problem in the field of radar signal processing which arouses people's attention widely is the detection and tracking dim moving targets in very low signal-to-noise ratio (SNR) environment.Track-Before-Detect (TBD) approaches are quite effective on the detection of dim targets,and the basic thought of this method is avoiding of the loss of CFAR by processing the raw data directly.An idea of detecting targets by combining CFAR with TBD methods is presented.In other words,low-threshold CFAR and process of ranking before TBD are added,and the conception of smoothness is introduced in order to get rid of false trails.Simulation results show this approach has small amount of computation,and achieves 2~3dB SNR gains comparable to those from other TBD algorithms.关键词：track-before-detect;dynamic programming algorithm;dim target detection4|2290|1更新时间：2025-07-16
- 摘要：Turbo codes with random interleavers are capable of achieving better error correcting performance than that obtained with structured interleavers at low SNR and the situation is in general the other way round at high SNR.To get better performance under the condition of various signal-to-noise ratios,this paper proposed a novel pseudo-random reverse block interleaver,which efficiently avoids the edge effect and combines the advantages of random interleavers and structured interleavers.Built in two proposed interleavers with different starting points,a novel Turbo encoder produced herein,capable of making Turbo codes obtains an increment in the minimum Hamming weight and consequently obtain a decrease at bit error rate.Simulation results show that the error-correcting performance of Turbo codes with it is superior to those obtained with other encoders on the whole when the short frame is transmitted.In particular,for clean channel,Turbo codes with the proposed encoder are capable of achieving much better error correcting performance than before.关键词：Turbo codes;constituent encoder;interleaver;burst error;bit error rate2|1042|0更新时间：2025-07-16
- 摘要：This paper presents our global approach to model Ultra Wideband (UWB) FOPEN (Foliage Penetration).In this approach,we consider plane wave scattering (in time domain) from the tree trunks above the soil.The time-domain scattering is computed via FDTD method,which is particularly well adapted to frequency-dependent soil.Then with a Fast Fourier Transform (FFT),the FDTD result is transformed to the frequency domain.Thus,we may have rich information for applicability to the FOPEN detection need.关键词：Foliage Penetration;FDTD;ultra-wide band2|1018|0更新时间：2025-07-16
- 摘要：There exist two regions in open guiding wave structures,bound region and radiation region,and the radiation region is divided into antenna region and reactive region.The transition from the bound region to the radiation region has been extensively studied,however,the definition of the transition for the antenna region and the reactive region is much more complicated due to simultaneous existence of the leaky effect and cutoff effect in the whole radiation region.How to give a reasonable definition for these two regions thus becomes an important problem in investigation on leaky wave phenomenon.We extend the traditional definition of the cutoff region by using the concept of complex effective dielectric constant,and propose a simple but efficient method to separate the two regions.Furthermore,the attenuation caused by the leaky and cutoff effect is determined in the cutoff region and the deduced expression reveals the phenomenon of large attenuation constant but with low radiation efficiency.关键词：radiation region;bound region;leaky effect;cutoff effect;leaky wave2|757|0更新时间：2025-07-16
- 摘要：The transverse radiation phenomenon of the NRD guide slot antenna is deeply studied.And an efficient method is presented to obtain the power angular density of the transverse radiation.The results presented are not only useful and helpful for the design of such slot antenna,but also is of essential significance in the investigation for the integrated circuit in which slots are used to couple energy between the elements in the circuit.It is of particular significance for investigation of suppressing the interference that comes from the transverse radiation.关键词：NRD guide;slot antenna;moment method;transverse radiation2|875|1更新时间：2025-07-16
- 摘要：A novel method for selecting projection vectors in the noise subspace of array covariance matrix is proposed with a view to improving the spectrum resolution of subspace-based DOA estimation algorithms,which is called LSP (Localized Subspace Projection).The new projection vector(s) obtained by LSP can depress the spectrum amplitude at the spatial location in close vicinity to sources' actual spatial positions while remaining the specular peaks on the source positions.The LSP algorithm has lower peaks location bias and SNR resolution threshold than MUSIC,while remains almost the same peaks location variance with MUSIC.Computer simulation results verify the theoretical performance analysis of the given LSP algorithm and demonstrate the effectiveness of LSP algorithm.关键词：direction of arrival estimation;localized subspace projection;high resolution2|1000|11更新时间：2025-07-16
- 摘要：According to typical Sommerfeld Hertz vector,the electromagnetic field expressions are derived when horizontal DC current element is located in air half-space and seawater half-space respectively.Based on the result,the induced electric field of vessel moving across geomagnetic field is derived on the basis of transient state continuity theory.Take one Japanese missile destroyer for example,the magnitude and spatial distribution characteristics of its induced electric field are analyzed.The result indicates that the magnitude of electric field is several millivolt per meter at about five meters from hull when the vessel sails at a velocity of 20kn.According to the analysis,the induced electric field of vessel moving across geomagnetic field can be measured for certainty and its spatial distribution has apparent characteristics.关键词：induced electric field;moving vessel;Hertz vector;geomagnetic field2|1295|5更新时间：2025-07-16
- 摘要：A new type of broad-wall directional coupler is developed.By eigenvalue approach and odd-and even-mode approach the relationship of the coupling value and the dimension of the coupling section and the phase relationship of the output ports are presented.Mode-matching theory is applied and any additional tuning elements are not needed.The experimental data demonstrate the good performance.关键词：odd-even mode analytical method;eigenvalue method;wide wall coupler4|1503|1更新时间：2025-07-16
- 摘要：A multi-platform angle-only tracking system combines the angular measurements from distributed networked sensors.This paper investigates the effect of communication bandwidth on track quality in a system which receives angle-only measurements from two networked radars installed on two moving platforms in order to estimate the full kinematic target state.The investigation is based on Cramer-Rao lower bound of the mean-square range error,and applies the extended Kalman filter (EKF) to track maneuvering target.关键词：radar;data fusion;cramer-rao bound;target tracking2|1268|6更新时间：2025-07-16
- 摘要：Certified mail protocol is fair exchange of a message M for a receipt.Fairness is the most important property in exchange.We modify existing signcryption system so that it can be used by certified mail protocols,and based on the system we propose new certified mail protocols to guarantee fairness and low computation cost.关键词：electronic commerce;fair exchange protocols;certified mail protocols;signcryption system2|985|1更新时间：2025-07-16
- 摘要：The fuzzy c-means algorithm (FCM) is one of widely used clustering algorithms.It is an open problem how to select an appropriate fuzziness index m when implementing the FCM.Some researchers have suggested that the best choice for m is probably in the interval based on their experimental results.In this paper,we discovered the theoretical connection between the validity of FCM algorithm as clustering algorithm and clustering validity,and pointed out that the weighting exponent m is not the optimal if it makes the FCM not to work properly as a clustering algorithm.According to this analysis,we carried on one experiment.The experimental result shows that the optimal weighting exponent in FCM algorithm could not always belong to the range .关键词：weighting exponent;clustering validity;FCM algorithm;partition entropy2|1935|11更新时间：2025-07-16
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