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2003 Vol. 25, No. 1
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2003, 25(1): 1-8.
Abstract:
The basic and major difficulty in Automatic Target Recognition(ATR) based on the Inverse Synthetic Aperture Radar (ISAR) image is to automatically understand the ISAR images. A method of understanding and processing ISAR image is presented, which is based on the time-frequency analysis algorithm - improved Adaptive Guassian Representation(AGR). By parameterizing the point-scattering and dispersive-scattering mechanisms exiting in the target ISAR image, the dispersive-scattering effect is removed to improve the image quality, and extract features of scattering centers on the target which is useful to ATR. The efficiency and feasibility of the method is confirmed by the test, based on the real data of airplane.
The basic and major difficulty in Automatic Target Recognition(ATR) based on the Inverse Synthetic Aperture Radar (ISAR) image is to automatically understand the ISAR images. A method of understanding and processing ISAR image is presented, which is based on the time-frequency analysis algorithm - improved Adaptive Guassian Representation(AGR). By parameterizing the point-scattering and dispersive-scattering mechanisms exiting in the target ISAR image, the dispersive-scattering effect is removed to improve the image quality, and extract features of scattering centers on the target which is useful to ATR. The efficiency and feasibility of the method is confirmed by the test, based on the real data of airplane.
2003, 25(1): 9-16.
Abstract:
Signal properties of spaceborne spotlight SAR. arc; discussed. Based on the analyses of a few .spotlight imaging algorithm, a modified chirp scaling algorithm for spaceborne spotlight SAR is proposed. Besides, a subaperture method is combined with the algorithm. In order to resolve high Pulse Repetition Frequency (PR.F) and the time-variant of Doppler center frequency, etc., the necessity and implementation approach of the subaperture method are analyzed thoroughly. The validity of the proposed method is tested by computer simulation.
Signal properties of spaceborne spotlight SAR. arc; discussed. Based on the analyses of a few .spotlight imaging algorithm, a modified chirp scaling algorithm for spaceborne spotlight SAR is proposed. Besides, a subaperture method is combined with the algorithm. In order to resolve high Pulse Repetition Frequency (PR.F) and the time-variant of Doppler center frequency, etc., the necessity and implementation approach of the subaperture method are analyzed thoroughly. The validity of the proposed method is tested by computer simulation.
2003, 25(1): 17-23.
Abstract:
In order to enhance the performance of OSSO, the Generalized Smallest Op-tion(GSO) of logic CFAR algorithm is proposed in this paper. For this CFAR. algorithms, it splits the reference window into two sub-windows and uses the linear combined order statis-tics to create two local noise power estimations, the smallest of them is used to set an adaptive threshold. How to select the weighted coefficient of the linear combined order statistics in the practical situation, several suggestions are given. In the special cases of GSO, QBWSO, TMSO, CMSO, OSSO and SO methods are deduced. The analytic results show that the detection per-formance of QBWSO and TMSO is superior to that of OSSO both in homogeneous background and in multiple target situation, the CFAR loss of QBWSO is slightly lower than that of TMSO in homogeneous background. In homogeneous background, the detection performance of SO is the best.
In order to enhance the performance of OSSO, the Generalized Smallest Op-tion(GSO) of logic CFAR algorithm is proposed in this paper. For this CFAR. algorithms, it splits the reference window into two sub-windows and uses the linear combined order statis-tics to create two local noise power estimations, the smallest of them is used to set an adaptive threshold. How to select the weighted coefficient of the linear combined order statistics in the practical situation, several suggestions are given. In the special cases of GSO, QBWSO, TMSO, CMSO, OSSO and SO methods are deduced. The analytic results show that the detection per-formance of QBWSO and TMSO is superior to that of OSSO both in homogeneous background and in multiple target situation, the CFAR loss of QBWSO is slightly lower than that of TMSO in homogeneous background. In homogeneous background, the detection performance of SO is the best.
2003, 25(1): 24-30.
Abstract:
To focus a synthetic-aperture radar image which suffers from phase errors, an autofocus algorithm, Contrast Optimization Autofocus Algorithm (COAA), is proposed. This algorithm is based on the optimization of the contrast function, which represents a measure of the focus degree of the image. The main steps of the COAA are described. Experimental results show that this algorithm is very efficient. The COAA has many advantages. The relative performances of COAA and another autofocus algorithm, MAPDRIFT autofocus algorithm, arc compared.
To focus a synthetic-aperture radar image which suffers from phase errors, an autofocus algorithm, Contrast Optimization Autofocus Algorithm (COAA), is proposed. This algorithm is based on the optimization of the contrast function, which represents a measure of the focus degree of the image. The main steps of the COAA are described. Experimental results show that this algorithm is very efficient. The COAA has many advantages. The relative performances of COAA and another autofocus algorithm, MAPDRIFT autofocus algorithm, arc compared.
2003, 25(1): 31-36.
Abstract:
In this paper, multi-object radar signals resolution is studied by using the weight reassignment method, which can easily be realized because of its fast algorithm and its simple structure. Although time- frequency distribution is not bilinear when the reassignment method is used, it exhibits some other good properties, especially its perfect localizing for chirp and impulse signals. Based on the linear frequency modulation model of radar signals,which are suit for using the reassignment method, real formation radar targets echo data is processed to obtain better radar multi-object classification. A number of experimental results are given to prove that the weight reassignment method can be used to improve time-frequency resolution and capability of restraining interference and noise.
In this paper, multi-object radar signals resolution is studied by using the weight reassignment method, which can easily be realized because of its fast algorithm and its simple structure. Although time- frequency distribution is not bilinear when the reassignment method is used, it exhibits some other good properties, especially its perfect localizing for chirp and impulse signals. Based on the linear frequency modulation model of radar signals,which are suit for using the reassignment method, real formation radar targets echo data is processed to obtain better radar multi-object classification. A number of experimental results are given to prove that the weight reassignment method can be used to improve time-frequency resolution and capability of restraining interference and noise.
2003, 25(1): 37-43.
Abstract:
Firstly, the characteristic of Duffing oscillator is studied, and based on the combination of Duffing oscillator with wavelet transform and neural network, a new detection method for low speed and small target over noise background is proposed. The simulation results show that the proposed method succeeds in detecting low speed target with low false alarm probability in low signal to noise ratio environment.
Firstly, the characteristic of Duffing oscillator is studied, and based on the combination of Duffing oscillator with wavelet transform and neural network, a new detection method for low speed and small target over noise background is proposed. The simulation results show that the proposed method succeeds in detecting low speed target with low false alarm probability in low signal to noise ratio environment.
2003, 25(1): 44-49.
Abstract:
A new algorithm is developed to merge a high-resolution panchromatic image and a low-resolution multi-spectral image based on the combination of multi-resolution wavelet, decomposition, evolutionary strategy and the IHS transform. The high-resolution panchromatic image is firstly decomposed to the wavelet planes, then the region is divided by the wavelet planes and the proposed merging algorithm is done by adding edge influence factor in different region. The proposed method is compared with the IHS and the MWD methods. The results of the comparison show the proposed merger performing the best in combining and preserving spectral-spatial information for the test images.
A new algorithm is developed to merge a high-resolution panchromatic image and a low-resolution multi-spectral image based on the combination of multi-resolution wavelet, decomposition, evolutionary strategy and the IHS transform. The high-resolution panchromatic image is firstly decomposed to the wavelet planes, then the region is divided by the wavelet planes and the proposed merging algorithm is done by adding edge influence factor in different region. The proposed method is compared with the IHS and the MWD methods. The results of the comparison show the proposed merger performing the best in combining and preserving spectral-spatial information for the test images.
2003, 25(1): 50-53.
Abstract:
The problem of unsupervised classification of remotely sensed image is considered in this paper. A Hidden Markov Random Field (HMRF) model is built and a new image clas-sification algorithm based on the HMRF model is presented to the remote sensing application. In the algorithm, the Finite Gaussian Mixture (FGM) model is used to describe the density function of the image pixel intensity, the Expectation Maximization (EM) algorithm is used for the HMRF model parameters under the incomplete data condition, and MAP (Maximum A Posteriori) method is used to estimate the image class label. As the MRF model with fixed parameters does not fit the real remotely sensed image very well, this paper adjusts the MRF models parameters during the classification procedure. The novel image classification method gives a more accurate and more robust image classification.
The problem of unsupervised classification of remotely sensed image is considered in this paper. A Hidden Markov Random Field (HMRF) model is built and a new image clas-sification algorithm based on the HMRF model is presented to the remote sensing application. In the algorithm, the Finite Gaussian Mixture (FGM) model is used to describe the density function of the image pixel intensity, the Expectation Maximization (EM) algorithm is used for the HMRF model parameters under the incomplete data condition, and MAP (Maximum A Posteriori) method is used to estimate the image class label. As the MRF model with fixed parameters does not fit the real remotely sensed image very well, this paper adjusts the MRF models parameters during the classification procedure. The novel image classification method gives a more accurate and more robust image classification.
2003, 25(1): 54-61.
Abstract:
The separability and separating conditions for mixed signals are analyzed in this paper. The limitation of nonlinear blind source separation methods is proposed. A new nonlinear BSS approach is developed by applying Edgeworth expansion and adaptive cumulant estimation into information back propagation algorithm. Computer simulation shows the validity of the proposed algorithm in some ad hoc model. A comparison with the Gram-Charlier expansion method is given.
The separability and separating conditions for mixed signals are analyzed in this paper. The limitation of nonlinear blind source separation methods is proposed. A new nonlinear BSS approach is developed by applying Edgeworth expansion and adaptive cumulant estimation into information back propagation algorithm. Computer simulation shows the validity of the proposed algorithm in some ad hoc model. A comparison with the Gram-Charlier expansion method is given.
2003, 25(1): 62-66.
Abstract:
DNA computing is a novel method for solving a class of intractable computational problem, in which the computing can grow exponentially with problem size. Up to now, many accomplishments have been achieved to improve its performance and increase its reliability. In this paper, a theoretical scheme of solving 0-1 planning problem with fluorescence labeling technique given and used to apply DNA computing to planning problem. This method has some significant advantages such as simple encoding, low cost, short operating time, etc.
DNA computing is a novel method for solving a class of intractable computational problem, in which the computing can grow exponentially with problem size. Up to now, many accomplishments have been achieved to improve its performance and increase its reliability. In this paper, a theoretical scheme of solving 0-1 planning problem with fluorescence labeling technique given and used to apply DNA computing to planning problem. This method has some significant advantages such as simple encoding, low cost, short operating time, etc.
2003, 25(1): 67-73.
Abstract:
An information-theoretic analysis of probability model for the stop-and-go sequences is proposed, the result of mutual information entropy between control sequence and output sequence is obtained and the lower bound of mutual information entropy between input sequence and output sequence is given.
An information-theoretic analysis of probability model for the stop-and-go sequences is proposed, the result of mutual information entropy between control sequence and output sequence is obtained and the lower bound of mutual information entropy between input sequence and output sequence is given.
2003, 25(1): 74-79.
Abstract:
It is necessary to know the logical meaning of every binary neuron when extracting knowledge from a binary neural network. Generally, it is difficult, to analyze learning results of a learning algorithm for binary neural networks. Ln this paper, a new learning method is presented which is based on analyzing a set of linear separable structures. The most important benefit of this method is all binary neurons belong to one or more types of linear separable structure sets. If those linear separable structure sets have clear logical meaning, the whole knowledge of binary neural networks can be dug out.
It is necessary to know the logical meaning of every binary neuron when extracting knowledge from a binary neural network. Generally, it is difficult, to analyze learning results of a learning algorithm for binary neural networks. Ln this paper, a new learning method is presented which is based on analyzing a set of linear separable structures. The most important benefit of this method is all binary neurons belong to one or more types of linear separable structure sets. If those linear separable structure sets have clear logical meaning, the whole knowledge of binary neural networks can be dug out.
2003, 25(1): 80-87.
Abstract:
In this paper, three heuristic algorithms are presented about deciding how many converters are needed in the best nodes of WDM network. By simulating in NSFNET, ARPANET and CERNET, the performances of three algorithms are compared. The results show that per-formance of the Algorithm 1 is the best and its complexity is the lowest. Furthermore, by using the Algorithm 1 in the best nodes and all nodes, it is found that the- performance of wavelength converters equipped in the best nodes is not worse than that in all nodes, so the cost and complexity of OXC in the network are reduced.
In this paper, three heuristic algorithms are presented about deciding how many converters are needed in the best nodes of WDM network. By simulating in NSFNET, ARPANET and CERNET, the performances of three algorithms are compared. The results show that per-formance of the Algorithm 1 is the best and its complexity is the lowest. Furthermore, by using the Algorithm 1 in the best nodes and all nodes, it is found that the- performance of wavelength converters equipped in the best nodes is not worse than that in all nodes, so the cost and complexity of OXC in the network are reduced.
2003, 25(1): 88-93.
Abstract:
In IP multicast network, how to choose appropriate multicast routes and optimize the configuration for reducing the cost of multicast are the key to popularize the multicast service. Aiming at characteristics of multicast routing algorithm and weakness of existing algorithm, a new dynamic multicast routing algorithm called Dynamic Minimum Path cost Heuristic (DMPH) is introduce. The simulation results show that the cost of tree from DMPH is similar to that of tree from static algorithm, and DMPH is faster than existing dynamic algorithms.
In IP multicast network, how to choose appropriate multicast routes and optimize the configuration for reducing the cost of multicast are the key to popularize the multicast service. Aiming at characteristics of multicast routing algorithm and weakness of existing algorithm, a new dynamic multicast routing algorithm called Dynamic Minimum Path cost Heuristic (DMPH) is introduce. The simulation results show that the cost of tree from DMPH is similar to that of tree from static algorithm, and DMPH is faster than existing dynamic algorithms.
2003, 25(1): 94-99.
Abstract:
Acting on the intermediate nodes, Active Queue Management (AQM) either keeps the high throughput for routers or effectively controls the queue lengths, so that arrives the object, to control end-to-end delay for QoS guarantees. C. Hollot, et al. (2001) designed the PI controller for AQM with the frequency approach in classical control theory, but it seems to be unscientific to tune the controller parameters through trial-errors, moreover the transient performance of the PI controller is not, perfect, such as the adjusting time is very long, etc. In this paper, the differential component is introduced to enhance the responsibility, and an approach for tuning controller parameters is put forward based on the explicit gain and phase margins. The simulation results show that the integrated performance of PID controller designed with the new approach is obviously superior to that of the PI controller.
Acting on the intermediate nodes, Active Queue Management (AQM) either keeps the high throughput for routers or effectively controls the queue lengths, so that arrives the object, to control end-to-end delay for QoS guarantees. C. Hollot, et al. (2001) designed the PI controller for AQM with the frequency approach in classical control theory, but it seems to be unscientific to tune the controller parameters through trial-errors, moreover the transient performance of the PI controller is not, perfect, such as the adjusting time is very long, etc. In this paper, the differential component is introduced to enhance the responsibility, and an approach for tuning controller parameters is put forward based on the explicit gain and phase margins. The simulation results show that the integrated performance of PID controller designed with the new approach is obviously superior to that of the PI controller.
2003, 25(1): 100-105.
Abstract:
Existing wavelet methods for the estimation of the Hurst parameter of self-similar traffic are systematically analyzed and examined. The effects of wavelet functions, vanishing-moments and wavelet decomposition levels on the results of wavelet methods for acquiring the Hurst index are investigated via numerical experiments. Some useful conclusions are drawn on the relationship between the accuracy of the methods and the selection of the order of vanishing moments and the selection of wavelet functions.
Existing wavelet methods for the estimation of the Hurst parameter of self-similar traffic are systematically analyzed and examined. The effects of wavelet functions, vanishing-moments and wavelet decomposition levels on the results of wavelet methods for acquiring the Hurst index are investigated via numerical experiments. Some useful conclusions are drawn on the relationship between the accuracy of the methods and the selection of the order of vanishing moments and the selection of wavelet functions.
2003, 25(1): 106-111.
Abstract:
The timing relationship between base stations is asynchronous in W-CDMA sys-tem. So the three-step cell search algorithm is introduced in 3GPP protocols in order to identify the special base station quickly. The second step, Secondary Synchronous CHannel(S-SCH) ac-quisition, is much critical, but the computing complexity of the conventional matched filter bank method is very large. This paper proposes Partial Fast Hadamard Transform (PFHT) ac-cording to the S-SCH structural property, which extremely reduces the computing complexity to almost 70%. On the other hand, a distributed sub-graph search algorithm is put forward to save more complication than RS code table brute-force search. In a word, the hardware complexity is dramatically cut down by the improved scheme, which is valuable for engineering applications.
The timing relationship between base stations is asynchronous in W-CDMA sys-tem. So the three-step cell search algorithm is introduced in 3GPP protocols in order to identify the special base station quickly. The second step, Secondary Synchronous CHannel(S-SCH) ac-quisition, is much critical, but the computing complexity of the conventional matched filter bank method is very large. This paper proposes Partial Fast Hadamard Transform (PFHT) ac-cording to the S-SCH structural property, which extremely reduces the computing complexity to almost 70%. On the other hand, a distributed sub-graph search algorithm is put forward to save more complication than RS code table brute-force search. In a word, the hardware complexity is dramatically cut down by the improved scheme, which is valuable for engineering applications.
2003, 25(1): 112-117.
Abstract:
This paper investigates the issues related to the cell assembly delay induced by filling AAL2 packets from different users into the payloads of ATM cells. A conclusion is drawn that the cell assembly delay is affected by the voice coding rate, voice packetization interval and the number of voice sources multiplexed. When the number of voice sources multiplexed is small and voice is compressed to a low bit rate, a timer is needed to limit the cell assembly delay. Timer can be set at 3ms if voice is compressed using 8kb/s G.729. When voice is compressed using 32kb/s G.726 with a voice packetization interval of 5ms, it is unnecessary to use the timer.
This paper investigates the issues related to the cell assembly delay induced by filling AAL2 packets from different users into the payloads of ATM cells. A conclusion is drawn that the cell assembly delay is affected by the voice coding rate, voice packetization interval and the number of voice sources multiplexed. When the number of voice sources multiplexed is small and voice is compressed to a low bit rate, a timer is needed to limit the cell assembly delay. Timer can be set at 3ms if voice is compressed using 8kb/s G.729. When voice is compressed using 32kb/s G.726 with a voice packetization interval of 5ms, it is unnecessary to use the timer.
2003, 25(1): 118-122.
Abstract:
The physical mechanism of PASOTRON (Plasma Assisted Slow-wave Oscillator) is studied. Taking into account the ion channel and making use of the linear field theory, the dispersion equation of corrugated waveguide filled with plasma is derived without a guiding magnetic field. It is analyzed by numerical computation that the temporal growth rates and the frequency of PASOTRON are affected by the filling factor of plasma.
The physical mechanism of PASOTRON (Plasma Assisted Slow-wave Oscillator) is studied. Taking into account the ion channel and making use of the linear field theory, the dispersion equation of corrugated waveguide filled with plasma is derived without a guiding magnetic field. It is analyzed by numerical computation that the temporal growth rates and the frequency of PASOTRON are affected by the filling factor of plasma.
2003, 25(1): 123-127.
Abstract:
In this paper, the synchronization of a coupled delayed neuron chaotic system is investigated. The asymptotic stability of the synchronization is discussed based on the Krasovskii-Lyapunov theory, and a sufficient condition of synchronization is obtained. The results of computer simulation show that the proposed synchronization system is an effective one, which is robust when Gaussian noise added.
In this paper, the synchronization of a coupled delayed neuron chaotic system is investigated. The asymptotic stability of the synchronization is discussed based on the Krasovskii-Lyapunov theory, and a sufficient condition of synchronization is obtained. The results of computer simulation show that the proposed synchronization system is an effective one, which is robust when Gaussian noise added.
2003, 25(1): 128-130.
Abstract:
The target of placement problem is related to the wire length, and the time delay optimization is also related to it. But in placement stage, it has not finished final routing, and must be decided without any wire routing whether a kind of placement is good or not, there must have a simple and accurate estimation method of wire net length to evaluate wire length. This paper introduces some kinds of conventional methods which are used to evaluate the wire length, then a new method using fractal to evaluate the wire length is given.
The target of placement problem is related to the wire length, and the time delay optimization is also related to it. But in placement stage, it has not finished final routing, and must be decided without any wire routing whether a kind of placement is good or not, there must have a simple and accurate estimation method of wire net length to evaluate wire length. This paper introduces some kinds of conventional methods which are used to evaluate the wire length, then a new method using fractal to evaluate the wire length is given.
2003, 25(1): 131-134.
Abstract:
The structure of aluminates which are used for Ba-W cathode is analyzed by XRD technology. It has been shown that the aluminates produced by some companies in Russian and our country are very complicated. The main single structure (Ba5CaAl4O12) of the aluminates has been formed by a new firing technology and new prescription. Its firing temperature; is 200C lower than that of conventional method. The melting point of the aluminates is lower than that of the conventional one. The cathode impregnated with the new aluminateH has high and stable emission current and low evaporation, which can improve the characteristics of Ba-W cathode.
The structure of aluminates which are used for Ba-W cathode is analyzed by XRD technology. It has been shown that the aluminates produced by some companies in Russian and our country are very complicated. The main single structure (Ba5CaAl4O12) of the aluminates has been formed by a new firing technology and new prescription. Its firing temperature; is 200C lower than that of conventional method. The melting point of the aluminates is lower than that of the conventional one. The cathode impregnated with the new aluminateH has high and stable emission current and low evaporation, which can improve the characteristics of Ba-W cathode.
2003, 25(1): 135-138.
Abstract:
The optimum design of magnet structures requires that every part of the magnets work at a point on the demagnetization curve which is as near to (BH)max as possible. CTA is a program for the computation of magnetic fields in axisymmetric systems. It has some defects in its search for magnet working points, and furthermore, for a complex structure it cannot provide a sole result to judge how much magnetic energy is contributed by the magnets. In this paper the authors introduce average magnetic energy product to serve as a criterion for the judgment of the work state of magnets. For every magnet structure the improved CTA can present a unique average magnetic energy product and a map of the energy product distribution.
The optimum design of magnet structures requires that every part of the magnets work at a point on the demagnetization curve which is as near to (BH)max as possible. CTA is a program for the computation of magnetic fields in axisymmetric systems. It has some defects in its search for magnet working points, and furthermore, for a complex structure it cannot provide a sole result to judge how much magnetic energy is contributed by the magnets. In this paper the authors introduce average magnetic energy product to serve as a criterion for the judgment of the work state of magnets. For every magnet structure the improved CTA can present a unique average magnetic energy product and a map of the energy product distribution.
