ISSN 
2009 Vol. 38, No. 6
2009, 38(6): 897-903.
doi: 10.3969/j.issn.1001-0548.2009.06.001
Abstract:
It is very difficult to promote performance of microwave tubes in power, bandwidth, gain, efficiency, and nonlinearity comprehensively by traditional design method based on experience. The technique of modeling and simulation is the key method to improve the capability of microwave tubes. Recent advances in modeling and simulation of microwave tube are reviewed. The classification and representative codes of microwave tubes are introduced. 2D TWTCAD and 3D MTSS (Microwave Tube Simulator Suite) developed by University of Electronic Science and Technology of China are demonstrated. Finally, some proposals how to promote Chinese's capability in developing codes of microwave tubes are given.
It is very difficult to promote performance of microwave tubes in power, bandwidth, gain, efficiency, and nonlinearity comprehensively by traditional design method based on experience. The technique of modeling and simulation is the key method to improve the capability of microwave tubes. Recent advances in modeling and simulation of microwave tube are reviewed. The classification and representative codes of microwave tubes are introduced. 2D TWTCAD and 3D MTSS (Microwave Tube Simulator Suite) developed by University of Electronic Science and Technology of China are demonstrated. Finally, some proposals how to promote Chinese's capability in developing codes of microwave tubes are given.
2009, 38(6): 904-907.
doi: 10.3969/j.issn.1001-0548.2009.06.002
Abstract:
Based on stepped-frequency continuous wave (SFCW) and MTD filter with joint detection in time and frequency domain, a new method for life detection is proposed to get the range information in detecting human beings. Firstly, stepped-frequency continuous echo model in life detection built is according to human vibration model. Secondly, range gate is divided and time domain detection is used to gain the actually range gate where the targets are. And thirdly, the frequency information of these range gates is obtained, and then the effect of statistic objects elimilated through MID filter. At last, frequency domain detection is applied to get human beings targets. The theoretical validity is illustrated by simulation results.
Based on stepped-frequency continuous wave (SFCW) and MTD filter with joint detection in time and frequency domain, a new method for life detection is proposed to get the range information in detecting human beings. Firstly, stepped-frequency continuous echo model in life detection built is according to human vibration model. Secondly, range gate is divided and time domain detection is used to gain the actually range gate where the targets are. And thirdly, the frequency information of these range gates is obtained, and then the effect of statistic objects elimilated through MID filter. At last, frequency domain detection is applied to get human beings targets. The theoretical validity is illustrated by simulation results.
2009, 38(6): 908-912.
doi: 10.3969/j.issn.1001-0548.2009.06.003
Abstract:
According to the characteristics of non-cooperative bistatic pulse radar systems, A fast method for time delay estimation of moving targets, based on segment correlation-video integration, is proposed to solve the problem that the doppler mismatched loss of the cross-correlation detection of moving targets is serious. The processing performance of cross-correlation and segment correlation-video integration of LFM pulse-series is calculated and analyzed by simulation. It is demonstrated that the weak moving target can be detected and the time delay can be fast estimated by means of the segment correlation-video integration method, when the difference of the signal-noise ratio of the reference channel and target channel is very great.
According to the characteristics of non-cooperative bistatic pulse radar systems, A fast method for time delay estimation of moving targets, based on segment correlation-video integration, is proposed to solve the problem that the doppler mismatched loss of the cross-correlation detection of moving targets is serious. The processing performance of cross-correlation and segment correlation-video integration of LFM pulse-series is calculated and analyzed by simulation. It is demonstrated that the weak moving target can be detected and the time delay can be fast estimated by means of the segment correlation-video integration method, when the difference of the signal-noise ratio of the reference channel and target channel is very great.
2009, 38(6): 913-915.
doi: 10.3969/j.issn.1001-0548.2009.06.004
Abstract:
A new synchronous method is suggested to mitigate the negative impact of channel in ultra-wide band system. The new method uses a local reference signal whose sweeping frequency and time are expanded multiply with the input signal, and then the strength of the strongest part of the product is used in a feedback loop to capture and track the timing of input signal. The method has low complexity and eliminates the influence of channel.
A new synchronous method is suggested to mitigate the negative impact of channel in ultra-wide band system. The new method uses a local reference signal whose sweeping frequency and time are expanded multiply with the input signal, and then the strength of the strongest part of the product is used in a feedback loop to capture and track the timing of input signal. The method has low complexity and eliminates the influence of channel.
2009, 38(6): 916-920.
doi: 10.3969/j.issn.1001-0548.2009.06.005
Abstract:
According to the structure covariance matrix, the covariance matrix can be separated into two matrices rebuilt by phase information and amplitude information, respectively. The 2D-DOA could be estimated from the rebuilt phase information matrix by using traditional methods. Based on specially array geometry designation, the angular spread could be estimated by substituting the estimated DOA into the amplitude information vector. Thus such separation realizes separable estimations of 2D-DOA and angular spread for incoherently distributed sources. Computer simulation validated the performance of the method.
According to the structure covariance matrix, the covariance matrix can be separated into two matrices rebuilt by phase information and amplitude information, respectively. The 2D-DOA could be estimated from the rebuilt phase information matrix by using traditional methods. Based on specially array geometry designation, the angular spread could be estimated by substituting the estimated DOA into the amplitude information vector. Thus such separation realizes separable estimations of 2D-DOA and angular spread for incoherently distributed sources. Computer simulation validated the performance of the method.
2009, 38(6): 927-931.
doi: 10.3969/j.issn.1001-0548.2009.06.007
Abstract:
Pilot-symbol-assisted channel estimation techniques of 2-D transform-domain OFDM system. The right-bottom zero-padding and middle zero-padding of pilot-position channel frequency response (CFR) matrix are utilized to gain the whole channel's CFR. To decrease the interpolation error of aforementioned zero-padding methods, a novel method is proposed which uses different number zeros and different padding mode based on pilot quantity along frequency and time direction. Lastly, by Simulink® baseband model, the proposed method is verified and compared with other 2-D interpolations. Results show that it can improve the channel estimation accuracy and decrease system bit error rate (BER) observably.
Pilot-symbol-assisted channel estimation techniques of 2-D transform-domain OFDM system. The right-bottom zero-padding and middle zero-padding of pilot-position channel frequency response (CFR) matrix are utilized to gain the whole channel's CFR. To decrease the interpolation error of aforementioned zero-padding methods, a novel method is proposed which uses different number zeros and different padding mode based on pilot quantity along frequency and time direction. Lastly, by Simulink® baseband model, the proposed method is verified and compared with other 2-D interpolations. Results show that it can improve the channel estimation accuracy and decrease system bit error rate (BER) observably.
2009, 38(6): 932-937.
doi: 10.3969/j.issn.1001-0548.2009.06.008
Abstract:
How to realize the cognitive capability is a key point to realize the cognitive wireless network. At present the method that combines network situation-aware database with case based reasoning (CBR) is received much attention. The construction of database in cognitive wireless network based on network situation-aware is deeply investigated in unfixed establishment network such as Ad hoc. The combination of NSGA-Ⅱand fuzzy decision is applied to constructing the Database in Cognitive Wireless Network from the aspect of network situation-aware and protocol configuration. Simulation result shows that: when adopting the mechanism of reconfiguration, the average time delay of the network will decrease to 50% above that of worst performance; the ratio of calling success will increase to 100%, and the throughput of the network will increase to 20%.
How to realize the cognitive capability is a key point to realize the cognitive wireless network. At present the method that combines network situation-aware database with case based reasoning (CBR) is received much attention. The construction of database in cognitive wireless network based on network situation-aware is deeply investigated in unfixed establishment network such as Ad hoc. The combination of NSGA-Ⅱand fuzzy decision is applied to constructing the Database in Cognitive Wireless Network from the aspect of network situation-aware and protocol configuration. Simulation result shows that: when adopting the mechanism of reconfiguration, the average time delay of the network will decrease to 50% above that of worst performance; the ratio of calling success will increase to 100%, and the throughput of the network will increase to 20%.
2009, 38(6): 938-942.
doi: 10.3969/j.issn.1001-0548.2009.06.009
Abstract:
The mobile-cellular model for weapon cooperation data link (WCDL) is proposed. The frequency hopping/code division multiple access (FH/CDMA) for this model is studied based on discrete frequency division multiplexing (FDM). Theoretically, the multiple access technology can sustain the service for infinite users and provide low delay service. The performances of success rate, throughput, and delay are analyzed. The influences of the main parameters such as the number of channels and the gain of spreading spectrum are simulated. The results demonstrale that the multiple access technology can meet the low delay application request of WCDL with better performances.
The mobile-cellular model for weapon cooperation data link (WCDL) is proposed. The frequency hopping/code division multiple access (FH/CDMA) for this model is studied based on discrete frequency division multiplexing (FDM). Theoretically, the multiple access technology can sustain the service for infinite users and provide low delay service. The performances of success rate, throughput, and delay are analyzed. The influences of the main parameters such as the number of channels and the gain of spreading spectrum are simulated. The results demonstrale that the multiple access technology can meet the low delay application request of WCDL with better performances.
2009, 38(6): 943-947.
doi: 10.3969/j.issn.1001-0548.2009.06.010
Abstract:
A new distributed key management scheme based on self-certified public key system and threshold cryptography is proposed for Ad hoc network. The storage space and the communication overheads can be reduced because the public key is self certified and the certificate is unnecessary. There is no key escrow problem since the key distribution center (KDC) does not know the users' private keys. The idea of composite public key (CPK) is introduced for selecting random number for threshold key distribution. It reduces the process of generating a random number before threshold signature is issued in traditional ElGamal type threshold signature and so it reduces the communication and computation overheads of network nodes. The analysis shows that the scheme is more secure and efficient than previous works implemented with public key systems.
A new distributed key management scheme based on self-certified public key system and threshold cryptography is proposed for Ad hoc network. The storage space and the communication overheads can be reduced because the public key is self certified and the certificate is unnecessary. There is no key escrow problem since the key distribution center (KDC) does not know the users' private keys. The idea of composite public key (CPK) is introduced for selecting random number for threshold key distribution. It reduces the process of generating a random number before threshold signature is issued in traditional ElGamal type threshold signature and so it reduces the communication and computation overheads of network nodes. The analysis shows that the scheme is more secure and efficient than previous works implemented with public key systems.
2009, 38(6): 948-951.
doi: 10.3969/j.issn.1001-0548.2009.06.011
Abstract:
In plain decode-and-forward (DF) cooperative diversity, asymmetric inter-user channel can have an impact on the performance of system and simple signal retransmission for each other is not an efficient diversity manner. In this paper, a new DF cooperative scheme based on signal-space diversity is propesed, in which the retransmission signals of each user always contain its own data frame and are designed in signal space diversity (SSD) manner. So the proposed scheme can defeat the effect of asymmetric inter-user channel and utilize diversity more efficiently. Simulation results prove that the new cooperative scheme achieves better bit error rate performance than both plain DF cooperative and non-cooperation scheme.
In plain decode-and-forward (DF) cooperative diversity, asymmetric inter-user channel can have an impact on the performance of system and simple signal retransmission for each other is not an efficient diversity manner. In this paper, a new DF cooperative scheme based on signal-space diversity is propesed, in which the retransmission signals of each user always contain its own data frame and are designed in signal space diversity (SSD) manner. So the proposed scheme can defeat the effect of asymmetric inter-user channel and utilize diversity more efficiently. Simulation results prove that the new cooperative scheme achieves better bit error rate performance than both plain DF cooperative and non-cooperation scheme.
2009, 38(6): 952-956.
doi: 10.3969/j.issn.1001-0548.2009.06.012
Abstract:
To solve the problem of poor resolution in passive millimeter wave (PMMW) imaging, we present an improved maximum a posteriori (MAP) super-resolution algorithm. The algorithm combines the advantages of Wiener filter restoration algorithm and MAP algorithm based on Poisson distribution. The Wiener filter is employed to restore the pass-band spectrum, and the MAP algorithm is applied to complete spectral extrapolation as the main iterative process to ensure that low-frequency component is not destroyed as spectral extrapolating. Meanwhile, the computational complexity and real time of the algorithm are analyzed. Furthermore, simulation results show that the algorithm can effectively restore the frequency out side the cut off frequency, enhances the resolution and can be implemented by parallel processing.
To solve the problem of poor resolution in passive millimeter wave (PMMW) imaging, we present an improved maximum a posteriori (MAP) super-resolution algorithm. The algorithm combines the advantages of Wiener filter restoration algorithm and MAP algorithm based on Poisson distribution. The Wiener filter is employed to restore the pass-band spectrum, and the MAP algorithm is applied to complete spectral extrapolation as the main iterative process to ensure that low-frequency component is not destroyed as spectral extrapolating. Meanwhile, the computational complexity and real time of the algorithm are analyzed. Furthermore, simulation results show that the algorithm can effectively restore the frequency out side the cut off frequency, enhances the resolution and can be implemented by parallel processing.
2009, 38(6): 957-961.
doi: 10.3969/j.issn.1001-0548.2009.06.013
Abstract:
Based on Taylor series expansion of the equations the third order analytical solutions of power system dynamical equations is derived by using normal form theory. In order to verify the theory proposed in this paper, numerical simulations are performed on a single machine infinite bus system and a four-generator two-area system. The linear, the second order, and the third order, solutions are compared, with two proximity indices defined in time domain and frequency domain, respectively. And Prony analysis is performed, testifying the existence of higher-order combination modes, which verifies the effectiveness of the third-order analytical solutions in the post-disturbance analysis of power system.
Based on Taylor series expansion of the equations the third order analytical solutions of power system dynamical equations is derived by using normal form theory. In order to verify the theory proposed in this paper, numerical simulations are performed on a single machine infinite bus system and a four-generator two-area system. The linear, the second order, and the third order, solutions are compared, with two proximity indices defined in time domain and frequency domain, respectively. And Prony analysis is performed, testifying the existence of higher-order combination modes, which verifies the effectiveness of the third-order analytical solutions in the post-disturbance analysis of power system.
2009, 38(6): 962-966.
doi: 10.3969/j.issn.1001-0548.2009.06.014
Abstract:
A constrained time-optimal predictive controller based on the piecewise affine (PWA) model is designed for solving the computation complexity of optimal control problem for mechanical system with backlash. For reducing computation burden of online implementation, the control law is computed offline for the range of states and references tracking speed by dynamic programming. In the experiments of tracking the reference speed, it is demonstrated that the constrained time-optimal predictive controller has better tracking control performance and reduces the computation time about ten times when compared with the constrained finite time optimal controller, therefore, the proposed approach and controller are suitable for real-time tracking control for systems with small sampling time.
A constrained time-optimal predictive controller based on the piecewise affine (PWA) model is designed for solving the computation complexity of optimal control problem for mechanical system with backlash. For reducing computation burden of online implementation, the control law is computed offline for the range of states and references tracking speed by dynamic programming. In the experiments of tracking the reference speed, it is demonstrated that the constrained time-optimal predictive controller has better tracking control performance and reduces the computation time about ten times when compared with the constrained finite time optimal controller, therefore, the proposed approach and controller are suitable for real-time tracking control for systems with small sampling time.
2009, 38(6): 967-970.
doi: 10.3969/j.issn.1001-0548.2009.06.015
Abstract:
Redundant design is an important method to increase reliability of small satellite. Traditional redundant design methods in small satellite design use spare hardware, therefore greatly increases the power consumption, volume and weight of the satellite. A redundant design method which combines software and hardware is presented in this paper. In this method sensors are divided into several groups. Multi sensor data fusion algorithm based on Bayes rule is used to give the estimate value for each sensor in a group. The validity of the estimate value is judged. If the estimate is invalid, the spare sensor is enabled. This redundant design method uses software to judge the validity of the result of temperature measurement and hardware to provide spare sensor. Therefore the number of spare sensors can be reduced significantly.
Redundant design is an important method to increase reliability of small satellite. Traditional redundant design methods in small satellite design use spare hardware, therefore greatly increases the power consumption, volume and weight of the satellite. A redundant design method which combines software and hardware is presented in this paper. In this method sensors are divided into several groups. Multi sensor data fusion algorithm based on Bayes rule is used to give the estimate value for each sensor in a group. The validity of the estimate value is judged. If the estimate is invalid, the spare sensor is enabled. This redundant design method uses software to judge the validity of the result of temperature measurement and hardware to provide spare sensor. Therefore the number of spare sensors can be reduced significantly.
2009, 38(6): 971-974.
doi: 10.3969/j.issn.1001-0548.2009.06.016
Abstract:
A fault diagnosis method for analog circuits with low testability using sensitivity analysis and support vector machine (SVM) is presented in this paper. The transfer function poles and zeros sensitivity of circuit under test is analyzed. The ambiguity group is determined according to the poles and zeros sensitivity with respect to the components and the testable components set is obtained. The poles and zeros sensitivity analysis theoretically determines all of the diagnosable circuit components and SVM has advantages of simple structure and strong generalization ability. Experimental results prove that the proposed method for diagnosing analog circuit fault using poles and zeros sensitivity analysis and SVM is effective and the fault diagnosis accuracy of the method is more than 99%.
A fault diagnosis method for analog circuits with low testability using sensitivity analysis and support vector machine (SVM) is presented in this paper. The transfer function poles and zeros sensitivity of circuit under test is analyzed. The ambiguity group is determined according to the poles and zeros sensitivity with respect to the components and the testable components set is obtained. The poles and zeros sensitivity analysis theoretically determines all of the diagnosable circuit components and SVM has advantages of simple structure and strong generalization ability. Experimental results prove that the proposed method for diagnosing analog circuit fault using poles and zeros sensitivity analysis and SVM is effective and the fault diagnosis accuracy of the method is more than 99%.
2009, 38(6): 975-978.
doi: 10.3969/j.issn.1001-0548.2009.06.017
Abstract:
Time domain reflection is a method for detecting cable's fault positions and reasons by analyzing the relationship between the transmitted pulse and the reflected pulse. Aimed at the blind spot in the domain reflection with narrow transmitted pulse, a method using wide differential transmitted pulse is proposed. The cable length and the fault reasons can be located by the method and the blind spot can be eliminated. The hardware structure of network cable tester designed by the method is presented and the key parts pulse generator and reflected pulse analyzer are analyzed in detail. At the end, the experiment data obtained by network cable tester are analyzed, the results show that the method is reliable.
Time domain reflection is a method for detecting cable's fault positions and reasons by analyzing the relationship between the transmitted pulse and the reflected pulse. Aimed at the blind spot in the domain reflection with narrow transmitted pulse, a method using wide differential transmitted pulse is proposed. The cable length and the fault reasons can be located by the method and the blind spot can be eliminated. The hardware structure of network cable tester designed by the method is presented and the key parts pulse generator and reflected pulse analyzer are analyzed in detail. At the end, the experiment data obtained by network cable tester are analyzed, the results show that the method is reliable.
2009, 38(6): 979-982.
doi: 10.3969/j.issn.1001-0548.2009.06.018
Abstract:
The Twiddler and head mounted display (HMD) are the most useful input and output devices for wearable computers, the tapping performance of Twiddler directly affects the controllability and usability of wearable computers. According to Fitts's law, the model of tapping performance in the Twiddler-HMD mode is established. Based on the model of tapping performance, the relationship between average tapping time and information quantity is researched. The result shows the icon is suitable for tapping operation of the wearable computer, when the ratio of the icon size to the width of graphical user interface (GUI) reaches 1/15.
The Twiddler and head mounted display (HMD) are the most useful input and output devices for wearable computers, the tapping performance of Twiddler directly affects the controllability and usability of wearable computers. According to Fitts's law, the model of tapping performance in the Twiddler-HMD mode is established. Based on the model of tapping performance, the relationship between average tapping time and information quantity is researched. The result shows the icon is suitable for tapping operation of the wearable computer, when the ratio of the icon size to the width of graphical user interface (GUI) reaches 1/15.
2009, 38(6): 983-986.
doi: 10.3969/j.issn.1001-0548.2009.06.019
Abstract:
An improved function point analysis (FPA) is proposed according to the project experience. According to difference of bussiness requierments and change factors in projects, a stability parameter is added into each function point of FPA to adjust original function point individually. A practical example is studied by the improved FPA. The experiment data proves that this method workes more exactly and more smoothly than traditional methods.
An improved function point analysis (FPA) is proposed according to the project experience. According to difference of bussiness requierments and change factors in projects, a stability parameter is added into each function point of FPA to adjust original function point individually. A practical example is studied by the improved FPA. The experiment data proves that this method workes more exactly and more smoothly than traditional methods.
2009, 38(6): 987-992.
doi: 10.3969/j.issn.1001-0548.2009.06.020
Abstract:
A distributed self-adaptive defense mechanism based on peer identification and real-time flow filtering is proposed in this paper under the research of DDos attacks in P2P network which is established on Gnutella protocol. In this mechanism, peers in such network can actively block the connection with malicious nodes by building local trust and reputation mechanism and keep away DDos attacks through real-time detection of the characteristic of DDos attack. Simulation result shows that our proposed distributed defense mechanism against DDos attacks can effectively improve the network resistance by obstructing 75% of the malicious messages and blocking 80% of the retransmission of them.
A distributed self-adaptive defense mechanism based on peer identification and real-time flow filtering is proposed in this paper under the research of DDos attacks in P2P network which is established on Gnutella protocol. In this mechanism, peers in such network can actively block the connection with malicious nodes by building local trust and reputation mechanism and keep away DDos attacks through real-time detection of the characteristic of DDos attack. Simulation result shows that our proposed distributed defense mechanism against DDos attacks can effectively improve the network resistance by obstructing 75% of the malicious messages and blocking 80% of the retransmission of them.
2009, 38(6): 993-997.
doi: 10.3969/j.issn.1001-0548.2009.06.021
Abstract:
A WA mesh network infrastructure combining WALN and Ad Hoc technologies is proposed, and an improved link status based routing algorithm, LSDSR, is presented for the need of high performance computing required by WA Mesh. Research analysis demonstrates that WA mesh network not only has the advantage of WLAN: low cost, high throughput, and high reliability, but also get the advantage of Ad-hoc network: high mobility, high flexibility, and high fault-tolerance. LSDSR could reduce the routing down time and flooding, hence LSDSR not only improves the routing discovery time and link load balance, but also optimizes the routing request message and reduces the packet loss rate.
A WA mesh network infrastructure combining WALN and Ad Hoc technologies is proposed, and an improved link status based routing algorithm, LSDSR, is presented for the need of high performance computing required by WA Mesh. Research analysis demonstrates that WA mesh network not only has the advantage of WLAN: low cost, high throughput, and high reliability, but also get the advantage of Ad-hoc network: high mobility, high flexibility, and high fault-tolerance. LSDSR could reduce the routing down time and flooding, hence LSDSR not only improves the routing discovery time and link load balance, but also optimizes the routing request message and reduces the packet loss rate.
2009, 38(6): 998-1000.
doi: 10.3969/j.issn.1001-0548.2009.06.022
Abstract:
The performance of campus networks involves many factors, including some non-quantitative ones, which result in the subjectivity and uncertainty in the network performance evaluation. Based on the fuzzy theory and its comprehensive evaluation, a model of network performance evaluation is presented by using the fuzzy relationship composition principle. The fuzzy dividing line between each factor and its divisors is measured by using the subordination degree; the fuzzy evaluation matrix is constructed according to the parameter of network performance index and evaluation grade; and the transformation theory of the fuzzy assemblage is employed to make a multi-calculation so as to decide the grade of the evaluated object.
The performance of campus networks involves many factors, including some non-quantitative ones, which result in the subjectivity and uncertainty in the network performance evaluation. Based on the fuzzy theory and its comprehensive evaluation, a model of network performance evaluation is presented by using the fuzzy relationship composition principle. The fuzzy dividing line between each factor and its divisors is measured by using the subordination degree; the fuzzy evaluation matrix is constructed according to the parameter of network performance index and evaluation grade; and the transformation theory of the fuzzy assemblage is employed to make a multi-calculation so as to decide the grade of the evaluated object.
2009, 38(6): 1001-1005.
doi: 10.3969/j.issn.1001-0548.2009.06.023
Abstract:
To improve the dependability of security/safety-critical systems, after analyzing status quo of high dependable safeguard mechanism, a multi-layered architecture based on the concept of separation and the VM is proposed, which supports applications with multi-level security. This paper researches multi-layered security/safety policy, the information flow control mechanism and the evaluation and certification for trusted software. This architecture can provide trustworthy services for the embedded security/safety-critical systems.
To improve the dependability of security/safety-critical systems, after analyzing status quo of high dependable safeguard mechanism, a multi-layered architecture based on the concept of separation and the VM is proposed, which supports applications with multi-level security. This paper researches multi-layered security/safety policy, the information flow control mechanism and the evaluation and certification for trusted software. This architecture can provide trustworthy services for the embedded security/safety-critical systems.
2009, 38(6): 1006-1010.
doi: 10.3969/j.issn.1001-0548.2009.06.024
Abstract:
A smooth terrain rendering algorithm based on GPU is proposed to solve time and space discontinuity problems during terrain visualization. The algorithm is a coarse-grained aggregated LOD method. Based on the smooth geomorph idea, the terrain chunk is divided into regions and the morphing weight of every vertex in the region is evaluated in real time for current morphing operation. The morphing weight involves the transition between different detail levels and the level difference between neighboring chunks. Through this morphing operation, during the terrain rendering, the smooth transition between different LOD levels and different terrain chunks can be achieved at the same time, and a smooth terrain walkthrough can be gotten. The method is implemented in a GPU-oriented way and the main computation for morphing is accomplished on GPU. The tests show that the algorithm can generate the smooth terrain scene at a high frame rate, and the cracks and pops during rendering can be eliminated efficiently.
A smooth terrain rendering algorithm based on GPU is proposed to solve time and space discontinuity problems during terrain visualization. The algorithm is a coarse-grained aggregated LOD method. Based on the smooth geomorph idea, the terrain chunk is divided into regions and the morphing weight of every vertex in the region is evaluated in real time for current morphing operation. The morphing weight involves the transition between different detail levels and the level difference between neighboring chunks. Through this morphing operation, during the terrain rendering, the smooth transition between different LOD levels and different terrain chunks can be achieved at the same time, and a smooth terrain walkthrough can be gotten. The method is implemented in a GPU-oriented way and the main computation for morphing is accomplished on GPU. The tests show that the algorithm can generate the smooth terrain scene at a high frame rate, and the cracks and pops during rendering can be eliminated efficiently.
2009, 38(6): 1011-1016.
doi: 10.3969/j.issn.1001-0548.2009.06.025
Abstract:
According to the interactive requirements of rich media scene, a script for control of rich media scene in embedded environment. In this script, XML markup language is adopted to describe grammar. The semantics is represented by defining elements and attributes. The script can be executed by traversing the scene DOM tree and it resolves logic controlling, state recovering, and terminal device capabilities calling of the scene. The script can share lots of same modules with the scene, such as parsing modules and executing modules. Therefore, the script has the characteristics of high execution efficiency and low consumption of resources compared with some other existing scripts.
According to the interactive requirements of rich media scene, a script for control of rich media scene in embedded environment. In this script, XML markup language is adopted to describe grammar. The semantics is represented by defining elements and attributes. The script can be executed by traversing the scene DOM tree and it resolves logic controlling, state recovering, and terminal device capabilities calling of the scene. The script can share lots of same modules with the scene, such as parsing modules and executing modules. Therefore, the script has the characteristics of high execution efficiency and low consumption of resources compared with some other existing scripts.
2009, 38(6): 1017-1020.
doi: 10.3969/j.issn.1001-0548.2009.06.026
Abstract:
For collected barcodes images, an image analysis method with the ability of locating, segmenting, correcting and recognizing the QR code is introduced. In order to meet real-time demands and obtain the optimal thresholds under various lighting conditions, we propose an improved adaptive thresholding, which is proved with high efficiency and high stability. In order to get the four corner points of QR code in the segmentation of barcode, a new algorithm is presented to obtain three points among those corner points according to their patterns features. The fourth corner point is then obtained by employing known point. Hough transformation. Experiment shows that the algorithm can get the four corner points of QR code effectively under various acquisition situations.
For collected barcodes images, an image analysis method with the ability of locating, segmenting, correcting and recognizing the QR code is introduced. In order to meet real-time demands and obtain the optimal thresholds under various lighting conditions, we propose an improved adaptive thresholding, which is proved with high efficiency and high stability. In order to get the four corner points of QR code in the segmentation of barcode, a new algorithm is presented to obtain three points among those corner points according to their patterns features. The fourth corner point is then obtained by employing known point. Hough transformation. Experiment shows that the algorithm can get the four corner points of QR code effectively under various acquisition situations.
2009, 38(6): 1021-1025.
doi: 10.3969/j.issn.1001-0548.2009.06.027
Abstract:
In order, to reduce the impact environmental requirements and overcome the effects of illumination on face recognition, a novel recognition method is presented based on normalization illumination in frequency-domain, via analyzing the Amplitude-frequency and phase-frequency characteristics of human faces. Collected images under any light conditions are normalized so that the light is exactly the same for the training images, while retaining the distinctive features of human faces. As the different information of faces is usually small, the smallest non-zero eigenvector is chosen as a facial feature. Experimental results show that our method is more robust against light than traditional methods.
In order, to reduce the impact environmental requirements and overcome the effects of illumination on face recognition, a novel recognition method is presented based on normalization illumination in frequency-domain, via analyzing the Amplitude-frequency and phase-frequency characteristics of human faces. Collected images under any light conditions are normalized so that the light is exactly the same for the training images, while retaining the distinctive features of human faces. As the different information of faces is usually small, the smallest non-zero eigenvector is chosen as a facial feature. Experimental results show that our method is more robust against light than traditional methods.
2009, 38(6): 1026-1030.
doi: 10.3969/j.issn.1001-0548.2009.06.028
Abstract:
A restorable image authentication with cellular automata transform is proposed. The original image is splited into non-overlppin blocks and two layer cellular automata transform (CAT) is performed on each block. Authentication watermark and restoration watermark are produced from the second-layer low frequency coefficients and embedded into the first-layer low frequency coefficients of the current block and the corresponding block separately. Image authentication is played with the authentication watermark, and the tampered blocks can be restored with restoration watermark. Experiment results show that the scheme's security is strong and can resist vector quantization attack effectively.
A restorable image authentication with cellular automata transform is proposed. The original image is splited into non-overlppin blocks and two layer cellular automata transform (CAT) is performed on each block. Authentication watermark and restoration watermark are produced from the second-layer low frequency coefficients and embedded into the first-layer low frequency coefficients of the current block and the corresponding block separately. Image authentication is played with the authentication watermark, and the tampered blocks can be restored with restoration watermark. Experiment results show that the scheme's security is strong and can resist vector quantization attack effectively.
2009, 38(6): 1031-1033.
doi: 10.3969/j.issn.1001-0548.2009.06.029
Abstract:
Accurate estimate of available bandwidth can make the Ad hoc network resources be used reasonably and effectively. A novel available bandwidth estimation mechanism based on frame retransmission prediction is proposed. The average size of contention window (CW) is used to evaluate the collision status and the number of frames that need to be retransmitted, and the estimation procedure is accomplished with the method of cooperation between mobile nodes. Results show that the method based on the average size of contention window can evaluate the frames collision status on the link with reasonable accuracy.
Accurate estimate of available bandwidth can make the Ad hoc network resources be used reasonably and effectively. A novel available bandwidth estimation mechanism based on frame retransmission prediction is proposed. The average size of contention window (CW) is used to evaluate the collision status and the number of frames that need to be retransmitted, and the estimation procedure is accomplished with the method of cooperation between mobile nodes. Results show that the method based on the average size of contention window can evaluate the frames collision status on the link with reasonable accuracy.
2009, 38(6): 1034-1038.
doi: 10.3969/j.issn.1001-0548.2009.06.030
Abstract:
Distinguishing the states of “movement” or “rest” in electroencephalogram (EEG) plays an important role in the domain of brain computer interface (BCI). According to the electroencephalogram feature, Hidden Markov model (HMM)-AR might be a useful tool in EEG pattern classification. The method which jointly employs Laplacian filter, ICA transform, and HMM-AR is presented for EEG pattern classification. The hybrid method is confirmed through the classification of EEG that is recorded during the imagination of a left or right hand movement. The results illustrate the algorithm can availably classify the two brain states of movement and rest. The algorithm for cue movement determination has been designed resulting in detecting the movements within one second interval. it prove the algorithm feasibility in BCI data sets.
Distinguishing the states of “movement” or “rest” in electroencephalogram (EEG) plays an important role in the domain of brain computer interface (BCI). According to the electroencephalogram feature, Hidden Markov model (HMM)-AR might be a useful tool in EEG pattern classification. The method which jointly employs Laplacian filter, ICA transform, and HMM-AR is presented for EEG pattern classification. The hybrid method is confirmed through the classification of EEG that is recorded during the imagination of a left or right hand movement. The results illustrate the algorithm can availably classify the two brain states of movement and rest. The algorithm for cue movement determination has been designed resulting in detecting the movements within one second interval. it prove the algorithm feasibility in BCI data sets.
2009, 38(6): 1039-1041.
doi: 10.3969/j.issn.1001-0548.2009.06.031
Abstract:
Based on the mental arithmetic task, computed EEG topography and brain electric power spectrum of the different competencies are analyzed. The results indicate the difference between the quick and slow groups and the frontal lobe of quick group is activated in higher degree. There is difference in α (8～12.8 Hz). The frequency band of quick group is lower than the slow group.
Based on the mental arithmetic task, computed EEG topography and brain electric power spectrum of the different competencies are analyzed. The results indicate the difference between the quick and slow groups and the frontal lobe of quick group is activated in higher degree. There is difference in α (8～12.8 Hz). The frequency band of quick group is lower than the slow group.
2009, 38(6): 1042-1046.
doi: 10.3969/j.issn.1001-0548.2009.06.032
Abstract:
Aiming at the problems of dynamic analysis on multi-body systems with redundant constraints, a solution based on the dynamic simulation in Mechanism module of Pro/E is proposed and illustrated with an example of a translational platform with multicrank. A three-dimensional model of the system is built simplified to fit the pivot in the research. Comprehensive dynamic simulation is performed based on the application of virtual prototyping technology in Pro/E. The factors which impact the motion and reacting forces of the platform are analyzed with simulation results. The optimized design is then considered.
Aiming at the problems of dynamic analysis on multi-body systems with redundant constraints, a solution based on the dynamic simulation in Mechanism module of Pro/E is proposed and illustrated with an example of a translational platform with multicrank. A three-dimensional model of the system is built simplified to fit the pivot in the research. Comprehensive dynamic simulation is performed based on the application of virtual prototyping technology in Pro/E. The factors which impact the motion and reacting forces of the platform are analyzed with simulation results. The optimized design is then considered.
Prediction of Plane Slotted-Array Antenna Electrical Performance Affected by Manufacturing Precision
2009, 38(6): 1047-1051.
doi: 10.3969/j.issn.1001-0548.2009.06.033
Abstract:
The manufacturing precision of slot in the plane slotted-array antenna has a great effect on the electrical performance. In order to avoid the shortcomings of assumptions and approximations made by some traditional methods during the course of studying the effect, a new method using support vector regression is proposed to obtain the prediction model of electrical performance affected by manufacturing precision, according to the data from the manufacturing of plane slotted-array antennas. Moreover, a method minimizing both model fitting capabilities and generalization as the objective function is offered to choose the proper parameters of support vector regression and facilitate the application. Simulation research shows that the proposed method can accurately predict the effect and has better generalization compared with BP neural network and least squares regression.
The manufacturing precision of slot in the plane slotted-array antenna has a great effect on the electrical performance. In order to avoid the shortcomings of assumptions and approximations made by some traditional methods during the course of studying the effect, a new method using support vector regression is proposed to obtain the prediction model of electrical performance affected by manufacturing precision, according to the data from the manufacturing of plane slotted-array antennas. Moreover, a method minimizing both model fitting capabilities and generalization as the objective function is offered to choose the proper parameters of support vector regression and facilitate the application. Simulation research shows that the proposed method can accurately predict the effect and has better generalization compared with BP neural network and least squares regression.
2009, 38(6): 1052-1056.
doi: 10.3969/j.issn.1001-0548.2009.06.034
Abstract:
Due to some restrictions to the numerical simulation of continua vibrations from the base, including rigid-body motion, constrains, loading mode and so on. An approach named the static inertia method is presented based on the principle of harmonic base vibration and FEM. This approach transforms the original problem into an ordinary harmonic vibration with fixed base according to the equivalent form of base load. The response is numerically simulated by combining the general FEM software with self-developed data processing software. Both the theoretical and numerical results show that the static inertia method is of effectiveness, simple implement and accurate.
Due to some restrictions to the numerical simulation of continua vibrations from the base, including rigid-body motion, constrains, loading mode and so on. An approach named the static inertia method is presented based on the principle of harmonic base vibration and FEM. This approach transforms the original problem into an ordinary harmonic vibration with fixed base according to the equivalent form of base load. The response is numerically simulated by combining the general FEM software with self-developed data processing software. Both the theoretical and numerical results show that the static inertia method is of effectiveness, simple implement and accurate.
