ISSN 
2009 Vol. 38, No. 1
2009, 38(1): 1-4.
Abstract:
After analyzing the iterative-filtering algorithm of a stationary step size adaptive polarization canceller (APC), a variable step size APC algorithm is proposed. The convergence condition and convergence speed of the proposed algorithm are analyzed. The simulation and comparison show that the variable step size algorithm has higher convergence speed than the stationary step size algorithm.
After analyzing the iterative-filtering algorithm of a stationary step size adaptive polarization canceller (APC), a variable step size APC algorithm is proposed. The convergence condition and convergence speed of the proposed algorithm are analyzed. The simulation and comparison show that the variable step size algorithm has higher convergence speed than the stationary step size algorithm.
2009, 38(1): 5-8.
Abstract:
An improved speckle reduction algorithm for polarimetric SAR image based on the local adaptive processing is proposed. This algorithm automatically adjusts the size of the filter window according to distributed characteristic of the pixels in and around the window in the span image. The window size is expanded in the homogeneous area to suppress speckle noises, while the window size is reduced in the area that contains abundant details. This algorithm has the advantages of effectively reducing the speckle noise and keeping the detail. Experiments demonstrate the effectiveness of the proposed method.
An improved speckle reduction algorithm for polarimetric SAR image based on the local adaptive processing is proposed. This algorithm automatically adjusts the size of the filter window according to distributed characteristic of the pixels in and around the window in the span image. The window size is expanded in the homogeneous area to suppress speckle noises, while the window size is reduced in the area that contains abundant details. This algorithm has the advantages of effectively reducing the speckle noise and keeping the detail. Experiments demonstrate the effectiveness of the proposed method.
2009, 38(1): 9-12.
Abstract:
The blanketed zone of support jamming is computed by the pattern propagation factor (PPF) with different reflection coefficient and carrier frequency. The signal jamming noise ratio is concluded with the different reflectance on different propagation path. The antenna model is built with rectangular aperture, and a cosine-squared-on-a-pedestal is adopted to suppress the back lobe. The PPF calculation model is formed according to reflection coefficient definition and the wave path difference between the direct path and reflected path. The simulation results show that the jamming blanketed zone is extended for the multipath effect, and the zone is divided into parts. In addition, the exposed zone decrease with the decrease of reflection coefficient, but the shape of exposed zone does not change. And the higher the radar carrier frequency is, the greater the PPF fluctuation is. Analysis results indicate that the multipath effect can be lightened or utilized in virtue of the diversity of carrier frequency for the broad band radar.
The blanketed zone of support jamming is computed by the pattern propagation factor (PPF) with different reflection coefficient and carrier frequency. The signal jamming noise ratio is concluded with the different reflectance on different propagation path. The antenna model is built with rectangular aperture, and a cosine-squared-on-a-pedestal is adopted to suppress the back lobe. The PPF calculation model is formed according to reflection coefficient definition and the wave path difference between the direct path and reflected path. The simulation results show that the jamming blanketed zone is extended for the multipath effect, and the zone is divided into parts. In addition, the exposed zone decrease with the decrease of reflection coefficient, but the shape of exposed zone does not change. And the higher the radar carrier frequency is, the greater the PPF fluctuation is. Analysis results indicate that the multipath effect can be lightened or utilized in virtue of the diversity of carrier frequency for the broad band radar.
2009, 38(1): 13-16.
Abstract:
A multi-sensor image fusion method based on redundant lifting non-separable wavelet transform is presented. This method can capture the detail information of an image accurately. The wavelet coefficients of the approximant and detail sub-images are fused respectively based-on the fusion rule of local area gradient. This method is effectively used to fuse the multi-spectral infrared images and the multi-sensor medical images. The results show that the proposed method has the property of shift-invariance and betterfusion effect.
A multi-sensor image fusion method based on redundant lifting non-separable wavelet transform is presented. This method can capture the detail information of an image accurately. The wavelet coefficients of the approximant and detail sub-images are fused respectively based-on the fusion rule of local area gradient. This method is effectively used to fuse the multi-spectral infrared images and the multi-sensor medical images. The results show that the proposed method has the property of shift-invariance and betterfusion effect.
2009, 38(1): 17-20.
Abstract:
Ionospheric frequency modulation causes spreading of the surface clutter in Doppler domain which greatly limits the detection performance of HF sky-wave radars. This paper proposes a cascaded approach to correct the ionospheric frequency modulation. This approach consists of two correction steps. At the first step, time-frequency distribution (spectrogram or pseudo Wigner-Ville distribution) of the time-varying signal is adopted and a peak-tracking scheme is designed to obtain a coarse ionosperic modulation estimation from the time-frequency distribution. At the second correction step, a parametric method based on piecewise polynomial phase model is exploited to eliminate the residual contamination. Simulation results show the effectiveness of this cascaded approach even for very serious cases where broadened Bragg lines are overlapped.
Ionospheric frequency modulation causes spreading of the surface clutter in Doppler domain which greatly limits the detection performance of HF sky-wave radars. This paper proposes a cascaded approach to correct the ionospheric frequency modulation. This approach consists of two correction steps. At the first step, time-frequency distribution (spectrogram or pseudo Wigner-Ville distribution) of the time-varying signal is adopted and a peak-tracking scheme is designed to obtain a coarse ionosperic modulation estimation from the time-frequency distribution. At the second correction step, a parametric method based on piecewise polynomial phase model is exploited to eliminate the residual contamination. Simulation results show the effectiveness of this cascaded approach even for very serious cases where broadened Bragg lines are overlapped.
2009, 38(1): 21-24.
Abstract:
Cooperative communication allows the sharing of antennas among single antenna wireless terminals, and thus can create a virtual multi-antenna system. Because of the strong coherence among the symbols of the LDPC code word, a virtual multiple input multiple output (MIMO) system can be created to obtain space diversity gain by encoding the parts of the symbols of a LDPC code word using space-time code and transmitting them via different users'antennas. By using such a code cooperation method, the system performance can be improved effectively without increasing the transmitting bandwidth or power.
Cooperative communication allows the sharing of antennas among single antenna wireless terminals, and thus can create a virtual multi-antenna system. Because of the strong coherence among the symbols of the LDPC code word, a virtual multiple input multiple output (MIMO) system can be created to obtain space diversity gain by encoding the parts of the symbols of a LDPC code word using space-time code and transmitting them via different users'antennas. By using such a code cooperation method, the system performance can be improved effectively without increasing the transmitting bandwidth or power.
2009, 38(1): 25-27.
Abstract:
A frequency-domain channel estimation (CE) scheme for orthogonal frequency division multiplexing (OFDM) channel estimation which is based on a linear transformation is developed. The transmitted signal can be recovered efficiently by a linear transformation of the received signal. Firstly, two results on the generalized rotation matrix are deduced. Then based on the modulations of pilot symbols BPSK or QPSK, we achieve two channel estimation algorithms respectively. Simulations are performed at the condition that the channel is assumed to be Rayleigh fading and flat within one frame. Simulation results show that the BER and PER performance can be improved obviously when in-phase channel and quadrature-phase channel of each sub-carrier are inserted in the pilot symbols.
A frequency-domain channel estimation (CE) scheme for orthogonal frequency division multiplexing (OFDM) channel estimation which is based on a linear transformation is developed. The transmitted signal can be recovered efficiently by a linear transformation of the received signal. Firstly, two results on the generalized rotation matrix are deduced. Then based on the modulations of pilot symbols BPSK or QPSK, we achieve two channel estimation algorithms respectively. Simulations are performed at the condition that the channel is assumed to be Rayleigh fading and flat within one frame. Simulation results show that the BER and PER performance can be improved obviously when in-phase channel and quadrature-phase channel of each sub-carrier are inserted in the pilot symbols.
2009, 38(1): 28-31.
Abstract:
Multi-input multi-output (MIMO) radar is a new radar technique developed recently. On transmitting, each channel radiates a unique and orthogonally coded waveform. On receiving, the return signals are processed through a bank of matched filters to separate each transmitted signal. Hence, the orthogonal performance between signals is crucial for implementing MIMO radar system. In this paper, the cross-ambiguity of OFD-LFM (orthogonal frequency division linear frequency modulation)signals is analyzed. The location and level of the cross-correlation peaks are investigated. The relation between the parameters that minimize the cross-correlation peaks of MIMO signals is derived. The simulation validates the correctness of the proposed theoretical analysis.
Multi-input multi-output (MIMO) radar is a new radar technique developed recently. On transmitting, each channel radiates a unique and orthogonally coded waveform. On receiving, the return signals are processed through a bank of matched filters to separate each transmitted signal. Hence, the orthogonal performance between signals is crucial for implementing MIMO radar system. In this paper, the cross-ambiguity of OFD-LFM (orthogonal frequency division linear frequency modulation)signals is analyzed. The location and level of the cross-correlation peaks are investigated. The relation between the parameters that minimize the cross-correlation peaks of MIMO signals is derived. The simulation validates the correctness of the proposed theoretical analysis.
2009, 38(1): 32-35.
Abstract:
This paper gives the discrete Fourier transform (DFT) implementation of the overlapped frequency division multiplexing (OvFDM) of non-orthogonal frequency division multiplexing (NOFDM) systems. This paper investigates the impact of conventional cyclic-prefix and zero-padding cyclic-prefix for DFT-OvFDM/DFTNFODM systems in the time-variant frequency-selective fading channels, respectively. Theoretical analysis and simulation results show that the zero-padding cyclic-prefix can exploit much more frequency diversity than the conventional cyclic-prefix.
This paper gives the discrete Fourier transform (DFT) implementation of the overlapped frequency division multiplexing (OvFDM) of non-orthogonal frequency division multiplexing (NOFDM) systems. This paper investigates the impact of conventional cyclic-prefix and zero-padding cyclic-prefix for DFT-OvFDM/DFTNFODM systems in the time-variant frequency-selective fading channels, respectively. Theoretical analysis and simulation results show that the zero-padding cyclic-prefix can exploit much more frequency diversity than the conventional cyclic-prefix.
2009, 38(1): 36-39.
Abstract:
A power allocation scheme for decode and forward cooperative communication is proposed to minimize the system outage probability. By considering power allocation scheme with perfect feedback which gives the lower bound of outage probability, the power allocation scheme with limited feedback is proposed. The transmission power in the latter scheme can be adjusted according to a few feedback bits. The simulation results prove that the proposed scheme with only a few feedback bits can achieve better performance gain than the relay channel scheme elsewhere.
A power allocation scheme for decode and forward cooperative communication is proposed to minimize the system outage probability. By considering power allocation scheme with perfect feedback which gives the lower bound of outage probability, the power allocation scheme with limited feedback is proposed. The transmission power in the latter scheme can be adjusted according to a few feedback bits. The simulation results prove that the proposed scheme with only a few feedback bits can achieve better performance gain than the relay channel scheme elsewhere.
2009, 38(1): 40-42.
Abstract:
Aimed at the channel estimation of OFDM-based (orthogonal frequency division multiplex based) transform domain communication (TDCS) systems under low SNR scenarios, channel estimation techniques fou suppressing noise in time domain and/or transform domain are proposed. In time domain, the noise is mitigated through three schemes:time-sliding average, time-forgetting average, and their combination as the channel is slowly time-varying. To further reduce the influence of noise, the time-domain-based channel estimation methods are also combined with IDFT transform domain technique. Simulation results show the proposed channel estimation methods can achieve nearly the same performance as that of perfect channel estimation.
Aimed at the channel estimation of OFDM-based (orthogonal frequency division multiplex based) transform domain communication (TDCS) systems under low SNR scenarios, channel estimation techniques fou suppressing noise in time domain and/or transform domain are proposed. In time domain, the noise is mitigated through three schemes:time-sliding average, time-forgetting average, and their combination as the channel is slowly time-varying. To further reduce the influence of noise, the time-domain-based channel estimation methods are also combined with IDFT transform domain technique. Simulation results show the proposed channel estimation methods can achieve nearly the same performance as that of perfect channel estimation.
2009, 38(1): 43-46.
Abstract:
Multidimensional scaling (MDS) algorithms are widely used in node localization for wireless sensor networks by constructing a pair-wise squared distance matrix and performing a double-centered transformation. Classical MDS algorithms reconfigure relative coordinates of nodes in a similarity space and give the solution based on least squares (LS) criterion. However, the transformation of classical MDS algorithms result in non-Gaussian distribution of the noise in the similarity matrix when white Gaussian noise exists in distance measurements. Thus the LS based estimator can not optimize the node location. To overcome this problem, a least absolute deviation (LAD) based cost function of classical MDS algorithm is presented. Simulation results show that the LAD based method yields better performance.
Multidimensional scaling (MDS) algorithms are widely used in node localization for wireless sensor networks by constructing a pair-wise squared distance matrix and performing a double-centered transformation. Classical MDS algorithms reconfigure relative coordinates of nodes in a similarity space and give the solution based on least squares (LS) criterion. However, the transformation of classical MDS algorithms result in non-Gaussian distribution of the noise in the similarity matrix when white Gaussian noise exists in distance measurements. Thus the LS based estimator can not optimize the node location. To overcome this problem, a least absolute deviation (LAD) based cost function of classical MDS algorithm is presented. Simulation results show that the LAD based method yields better performance.
2009, 38(1): 47-50.
Abstract:
A new medium access control (MAC) protocol based on fuzzy logic is proposed for Ad hoc networks. In MAC layer, the fuzzy logic is used to choose a proper add-in back-off window size for different priority flows. Thus, the low priority flows, interacted on the higher ones, can reduce their access probabilities. Simulation result shows that the new protocol can achieve better performance compared with 802.11e protocol in the terms of end-to-end delay and throughput of high priority flows.
A new medium access control (MAC) protocol based on fuzzy logic is proposed for Ad hoc networks. In MAC layer, the fuzzy logic is used to choose a proper add-in back-off window size for different priority flows. Thus, the low priority flows, interacted on the higher ones, can reduce their access probabilities. Simulation result shows that the new protocol can achieve better performance compared with 802.11e protocol in the terms of end-to-end delay and throughput of high priority flows.
2009, 38(1): 51-54.
Abstract:
An authenticated group key agreement protocol for resource-limited mobile devices was proposed by Tseng Y.M. It is demonstrated that this protocol has security vulnerabilities by mounting a man-in-middle attack against it. The protocol can not achieve key authentication in the presence of an active attacker. This paper presents an improved protocol which achieves mutual authentication. It provides not only the capability of forward secrecy and key authentication, but also the capability against passive attack and man-in-middle attack. The analysis shows that the presented protocol has lower computation cost and communication cost compared with Tseng's protocol.
An authenticated group key agreement protocol for resource-limited mobile devices was proposed by Tseng Y.M. It is demonstrated that this protocol has security vulnerabilities by mounting a man-in-middle attack against it. The protocol can not achieve key authentication in the presence of an active attacker. This paper presents an improved protocol which achieves mutual authentication. It provides not only the capability of forward secrecy and key authentication, but also the capability against passive attack and man-in-middle attack. The analysis shows that the presented protocol has lower computation cost and communication cost compared with Tseng's protocol.
2009, 38(1): 55-58.
Abstract:
With Canetti-Krawczyk model, a fast authentication protocol of exchanging multiple session keys between two participants is proposed. The security analysis and formal proof show that the proposed protocol is session-key secure with perfect forward secrecy (PFS). Moreover, the implementation of the protocol just need twice communications and a little computation. The results show the efficiency of the protocol in wireless network.
With Canetti-Krawczyk model, a fast authentication protocol of exchanging multiple session keys between two participants is proposed. The security analysis and formal proof show that the proposed protocol is session-key secure with perfect forward secrecy (PFS). Moreover, the implementation of the protocol just need twice communications and a little computation. The results show the efficiency of the protocol in wireless network.
2009, 38(1): 59-62.
Abstract:
An algorithm for rapid PN code acquisition based on combined short time correlation and FFT is studied in detail. The correlation time effect and FFT window size effect on the system gain are analyzed in theory when the pre-detection integration time is fixed. A novel method to measure the system performance is proposed in terms of mean system gain and mean detection probability. Also, the principle based on the maximum mean gain criteria is presented for selecting the optimal combination of the FFT size and window size of short time correlation. Simulation shows that even with the Doppler shift, the system performance with the optimal combination approaches the optimal performance without the Doppler shift.
An algorithm for rapid PN code acquisition based on combined short time correlation and FFT is studied in detail. The correlation time effect and FFT window size effect on the system gain are analyzed in theory when the pre-detection integration time is fixed. A novel method to measure the system performance is proposed in terms of mean system gain and mean detection probability. Also, the principle based on the maximum mean gain criteria is presented for selecting the optimal combination of the FFT size and window size of short time correlation. Simulation shows that even with the Doppler shift, the system performance with the optimal combination approaches the optimal performance without the Doppler shift.
2009, 38(1): 63-66.
Abstract:
The popular VoIP encryption algorithms have the disadvantages of high computational complexity and huge system capability consumption. To solve this problem, this paper proposes a new VoIP encryption algorithm suitable to civilian commercial applications with low cost, high speed, and low capability consumption. This algorithm uses the combination of encryption arithmetic operations and solves the problem that the secret key must be transmitted by public key cipher system.
The popular VoIP encryption algorithms have the disadvantages of high computational complexity and huge system capability consumption. To solve this problem, this paper proposes a new VoIP encryption algorithm suitable to civilian commercial applications with low cost, high speed, and low capability consumption. This algorithm uses the combination of encryption arithmetic operations and solves the problem that the secret key must be transmitted by public key cipher system.
2009, 38(1): 67-70.
Abstract:
Based on the analysis of all the intra prediction modes of H.264, an efficient hardware architecture for H.264 prediction is proposed to support all the prediction modes. By utilizing the idle cycles of certain special modes, some prediction values can be calculated in advance. The redundancy of prediction values between two neighbour lines in the same prediction mode is also fully utilized in order to get four prediction values in one cycle using two calculating uints. Under 55 MHz frequency, the implements can process 39 standard definition TV (SDTV) frames(720×480) per second.
Based on the analysis of all the intra prediction modes of H.264, an efficient hardware architecture for H.264 prediction is proposed to support all the prediction modes. By utilizing the idle cycles of certain special modes, some prediction values can be calculated in advance. The redundancy of prediction values between two neighbour lines in the same prediction mode is also fully utilized in order to get four prediction values in one cycle using two calculating uints. Under 55 MHz frequency, the implements can process 39 standard definition TV (SDTV) frames(720×480) per second.
2009, 38(1): 71-74.
Abstract:
The current distribution characteristics of microstrip lines are investigated with the improved spectral domain analysis method. The Chebyshev polynomial as basis functions is used to generate the expression for the tangential current distributions on microstrip lines, tangential current distribution characteristics within wider frequency range are obtained, and the effective relative permittivity is calculated with required basis functions in different range of frequency. Compared with the other numerical methods, this method can not only obtain high accurate results but also reduce the compute time in the corresponding frequency band. Simulation results showa good agreement with the calculated results within the range of h/λ0 ≤ 0.7.
The current distribution characteristics of microstrip lines are investigated with the improved spectral domain analysis method. The Chebyshev polynomial as basis functions is used to generate the expression for the tangential current distributions on microstrip lines, tangential current distribution characteristics within wider frequency range are obtained, and the effective relative permittivity is calculated with required basis functions in different range of frequency. Compared with the other numerical methods, this method can not only obtain high accurate results but also reduce the compute time in the corresponding frequency band. Simulation results showa good agreement with the calculated results within the range of h/λ0 ≤ 0.7.
2009, 38(1): 75-78.
Abstract:
The limitation of classical adaptive optics (AO) system and the basic principle of multi-conjugate adaptive optics (MCAO) a system are briefly introduced. The isoplanatic angle's expression of single and dual-conjugate is deduced on the base of the relative reference, and the selections of conjugation height are thoughtfully discussed. The isoplanatic angles for single and dual-conjugate and classical AO system are compared in the condition of level and upright-propagtion. The simulation results indicate that MCAO system has a notable effect on the gain of the isoplanatic angle. single-conjugate AO system is suitable for short-distance propagation applications, but for the far-distance remote sensing, MCAO system performs better than the former.
The limitation of classical adaptive optics (AO) system and the basic principle of multi-conjugate adaptive optics (MCAO) a system are briefly introduced. The isoplanatic angle's expression of single and dual-conjugate is deduced on the base of the relative reference, and the selections of conjugation height are thoughtfully discussed. The isoplanatic angles for single and dual-conjugate and classical AO system are compared in the condition of level and upright-propagtion. The simulation results indicate that MCAO system has a notable effect on the gain of the isoplanatic angle. single-conjugate AO system is suitable for short-distance propagation applications, but for the far-distance remote sensing, MCAO system performs better than the former.
2009, 38(1): 79-82.
Abstract:
A 3 mm low-voltage second-harmonic complex cavity gyrotron with gradual transition is designed and evaluated with a particle-in-cell code. The high efficient gyrotron interaction can be achieved at the second harmonic. The insulation requirements of the gyrotron and the size and weight of the power supply can be reduced by setting the operation voltage at 25 kV. A diffraction-coupled complex cavity operating in the low ohmic loss TE02/TE03 circular modes is introduced to control the mode competition problem and promote efficiency. The characteristics of RF structure, the suppression of parasite oscillations, and the optimization of work parameters are discussed. The PIC simulation results show that the gyrotron can generate 34 kW output power at 94 GHz with 34% operation efficiency.
A 3 mm low-voltage second-harmonic complex cavity gyrotron with gradual transition is designed and evaluated with a particle-in-cell code. The high efficient gyrotron interaction can be achieved at the second harmonic. The insulation requirements of the gyrotron and the size and weight of the power supply can be reduced by setting the operation voltage at 25 kV. A diffraction-coupled complex cavity operating in the low ohmic loss TE02/TE03 circular modes is introduced to control the mode competition problem and promote efficiency. The characteristics of RF structure, the suppression of parasite oscillations, and the optimization of work parameters are discussed. The PIC simulation results show that the gyrotron can generate 34 kW output power at 94 GHz with 34% operation efficiency.
2009, 38(1): 83-86.
Abstract:
The producing mechanism of secondary electrons in sealed neutron generator is discussed and several methods to suppress secondary electrons are introduced. The PIC simulation is carried out for the different methods. The result indicates that only a part of secondary electrons can be suppressed by Faraday cylinder and a part of them can enter into the accelerating gap to form electron current. The secondary electron current is about 1/5 of emitting current of secondary electrons on target. But almost all secondary electrons can be suppressed by electrostatic field combined with Faraday cylinder and the secondary electron current is about zero when the deflection voltage is 300 V.
The producing mechanism of secondary electrons in sealed neutron generator is discussed and several methods to suppress secondary electrons are introduced. The PIC simulation is carried out for the different methods. The result indicates that only a part of secondary electrons can be suppressed by Faraday cylinder and a part of them can enter into the accelerating gap to form electron current. The secondary electron current is about 1/5 of emitting current of secondary electrons on target. But almost all secondary electrons can be suppressed by electrostatic field combined with Faraday cylinder and the secondary electron current is about zero when the deflection voltage is 300 V.
2009, 38(1): 87-91.
Abstract:
The fault diagnosis model of radar receiver is built by applying multi-signal flow graphs. Based on the model the dependence matrix which relates faults and tests is generated and an algorithm calculating Bayes maximal posteriori probability of fault sources is derived. This algorithm is applied in fault diagnosis of radar receiver, and the real-time multi-fault locations are realized by using the maximal posteriori probability of fault sources as judging rule.
The fault diagnosis model of radar receiver is built by applying multi-signal flow graphs. Based on the model the dependence matrix which relates faults and tests is generated and an algorithm calculating Bayes maximal posteriori probability of fault sources is derived. This algorithm is applied in fault diagnosis of radar receiver, and the real-time multi-fault locations are realized by using the maximal posteriori probability of fault sources as judging rule.
2009, 38(1): 92-96.
Abstract:
In order to address the issue of power supply for electrical valve in the deserts and other circumstances, a novel method of electrical valve power supply by accumulator is presented, which is charged by photovoltaic cell. The controlling circuits of digital software phase-locked loop (DSPLL) using digital signal process (DSP) is constructed, which is driven by the pulse-width modulation (PWM) controlled by DC motor. The experiments prove that the photovoltaic cell can provide enough energy to turn on or shut down the electrical valve. The control method not only realizes the functions of the whole system, but also runs more precisely and reliable. In addition, this method greatly decreases the harmonics and ripples of power supply systems, making the entire system realize online remote control, data acquisition and transmission, and display the torque of electrical machine on LCD precisely. At the same time, the DC motor is able to control the flow magnitude of electrical valve more precisely and steadily.
In order to address the issue of power supply for electrical valve in the deserts and other circumstances, a novel method of electrical valve power supply by accumulator is presented, which is charged by photovoltaic cell. The controlling circuits of digital software phase-locked loop (DSPLL) using digital signal process (DSP) is constructed, which is driven by the pulse-width modulation (PWM) controlled by DC motor. The experiments prove that the photovoltaic cell can provide enough energy to turn on or shut down the electrical valve. The control method not only realizes the functions of the whole system, but also runs more precisely and reliable. In addition, this method greatly decreases the harmonics and ripples of power supply systems, making the entire system realize online remote control, data acquisition and transmission, and display the torque of electrical machine on LCD precisely. At the same time, the DC motor is able to control the flow magnitude of electrical valve more precisely and steadily.
2009, 38(1): 97-101.
Abstract:
According to the status of temporal logic languages without object-oriented concepts, projection temporal logic is extended, and then the new syntax and semantics are introduced. In the extended projection temporal logic, formal definitions of objects, classes, and inheritances are given based on the hierarchical variable sets and grouping predicates. An object-oriented temporal logic language framed tempura++, is defined as an executable subset of extended projection temporal logic, and it can be used for object-oriented programming and simulating the execution of composite web services. The illustrated example shows that the language can reuse code efficiently and improve code readability and maintainability in compare with Framed Tempura.
According to the status of temporal logic languages without object-oriented concepts, projection temporal logic is extended, and then the new syntax and semantics are introduced. In the extended projection temporal logic, formal definitions of objects, classes, and inheritances are given based on the hierarchical variable sets and grouping predicates. An object-oriented temporal logic language framed tempura++, is defined as an executable subset of extended projection temporal logic, and it can be used for object-oriented programming and simulating the execution of composite web services. The illustrated example shows that the language can reuse code efficiently and improve code readability and maintainability in compare with Framed Tempura.
2009, 38(1): 102-107.
Abstract:
By utilizing the repellency of Tibetan characters in the Tibetan grammar, all the basic Tibetan characters are reasonably assigned to the limited keyboard keys of the universal computer. A non-repeated code Tibetan keyboard layout is designed according to the similarity in pronunciation of English and Tibetan alphabet and the rules of computer keyboard layout. And a non-repeated code fast Tibetan input method in accordance with international and national Tibetan character coding standards is implemented on the base of the analysis of Tibetan coding standards. The problem achieving fast Tibetan input without using shift or redundancy keys is also resolved.
By utilizing the repellency of Tibetan characters in the Tibetan grammar, all the basic Tibetan characters are reasonably assigned to the limited keyboard keys of the universal computer. A non-repeated code Tibetan keyboard layout is designed according to the similarity in pronunciation of English and Tibetan alphabet and the rules of computer keyboard layout. And a non-repeated code fast Tibetan input method in accordance with international and national Tibetan character coding standards is implemented on the base of the analysis of Tibetan coding standards. The problem achieving fast Tibetan input without using shift or redundancy keys is also resolved.
2009, 38(1): 108-112.
Abstract:
Considering the heterogeneity and physical location of nodes, this paper represents a layered mixed query routing protocol. It uses time-stamp to achieve the agreement of physical location and logical position, and introduces super-node to cope with load imbalance between nodes and performance bottlenecks. Simulation test on P2PSim shows that this solution is superior to other protocols, such as Kademlia, Chord, and Tapestry, on large-scale peer-to-peer (P2P) networks.
Considering the heterogeneity and physical location of nodes, this paper represents a layered mixed query routing protocol. It uses time-stamp to achieve the agreement of physical location and logical position, and introduces super-node to cope with load imbalance between nodes and performance bottlenecks. Simulation test on P2PSim shows that this solution is superior to other protocols, such as Kademlia, Chord, and Tapestry, on large-scale peer-to-peer (P2P) networks.
2009, 38(1): 113-116.
Abstract:
Although network security situation (NSS) becomes a hot topic, the investigation on situation awareness (SA) still lacks an approbatory standard. Based on Endsley's research, the paper presents a scalable NSS model, and improves situation extraction (SE) to fit the network environment. The proposed model utilizes knowledge bases to standardize the situation acquisition and model the situation as an entity. The incident frequency, incident time, and space information are contained in the model, and the situation acquisition is simplified. Finally, the simulation results prove the model's feasibility and efficiency.
Although network security situation (NSS) becomes a hot topic, the investigation on situation awareness (SA) still lacks an approbatory standard. Based on Endsley's research, the paper presents a scalable NSS model, and improves situation extraction (SE) to fit the network environment. The proposed model utilizes knowledge bases to standardize the situation acquisition and model the situation as an entity. The incident frequency, incident time, and space information are contained in the model, and the situation acquisition is simplified. Finally, the simulation results prove the model's feasibility and efficiency.
2009, 38(1): 117-121.
Abstract:
A method based on an improved artificial immune strategy is introduced for the optimization of distributed multi-sensor decision fusion systems under Neyman-Pearson criteria for the cases with statistically dependent observation and fixed fusion rule. The object function is optimized in two steps without any information of its derivation:filter operator is used for pre-search to reduce the search space and then an artificial immune strategy is applied for the global search. The experimental results show that the proposed method has better convergence and higher precision than the traditional gradient algorithms. A further discussion on the best fusion rule for different means of signals is given.
A method based on an improved artificial immune strategy is introduced for the optimization of distributed multi-sensor decision fusion systems under Neyman-Pearson criteria for the cases with statistically dependent observation and fixed fusion rule. The object function is optimized in two steps without any information of its derivation:filter operator is used for pre-search to reduce the search space and then an artificial immune strategy is applied for the global search. The experimental results show that the proposed method has better convergence and higher precision than the traditional gradient algorithms. A further discussion on the best fusion rule for different means of signals is given.
2009, 38(1): 122-125.
Abstract:
A risk warning model of tax payment evaluation based on neural network and domain knowledge is presented in this paper. The enterprises that have the most possibility of tax dodging can be found by applying neural network methods. The doubtful points in tax payment of these enterprises are evaluated by statistical analysis methods. A case study shows the feasibility of the model.
A risk warning model of tax payment evaluation based on neural network and domain knowledge is presented in this paper. The enterprises that have the most possibility of tax dodging can be found by applying neural network methods. The doubtful points in tax payment of these enterprises are evaluated by statistical analysis methods. A case study shows the feasibility of the model.
2009, 38(1): 126-129.
Abstract:
We present a workflow modeling method based on the improved UML acting diagram after introducing the UML language in this paper. The modeling for semiconductor packing and testing is described and analyzed. The result shows that the improved method can achieve better effect in describing workflow modeling progress than conventional approaches.
We present a workflow modeling method based on the improved UML acting diagram after introducing the UML language in this paper. The modeling for semiconductor packing and testing is described and analyzed. The result shows that the improved method can achieve better effect in describing workflow modeling progress than conventional approaches.
2009, 38(1): 130-133.
Abstract:
The risk evaluation of E-government information systems is of the most importance in government administration and services. This paper presents a risk evaluation factors system based on operationally critical threat, asset and vulnerability evaluation (OCTAVE). A method of multi-element fuzzy synthesis Judgement on the risk of E-government information systems is established. A case study demonstrates the effectiveness of the proposed system and method.
The risk evaluation of E-government information systems is of the most importance in government administration and services. This paper presents a risk evaluation factors system based on operationally critical threat, asset and vulnerability evaluation (OCTAVE). A method of multi-element fuzzy synthesis Judgement on the risk of E-government information systems is established. A case study demonstrates the effectiveness of the proposed system and method.
2009, 38(1): 134-136.
Abstract:
ZnO nanowires were prepared on two piece of Si (100) substrates which faced up and down separately using Au as catalyzer by thermal evaporation and vapor transport. Only (002) diffraction peaks of ZnO can be found on the X-ray diffraction (XRD) patterns, this indicates that ZnO nanowires exhibit (001) preferred orientation. The scanning electronic microscope (SEM) images show that the average diameter is 100 nm and the average length is 4 μm. They are aligned on Si substrate well. While substrates facing up, the ZnO thin film of thickness of 500 nm is deposited on Si substrate firstly and ZnO nanowires grow on the ZnO thin films. And while substrates facing down, epitaxial ZnO nanowires grow on the substrates. The result indicates that the exposure of substrate affects the growth mechanism of ZnO nanowires.
ZnO nanowires were prepared on two piece of Si (100) substrates which faced up and down separately using Au as catalyzer by thermal evaporation and vapor transport. Only (002) diffraction peaks of ZnO can be found on the X-ray diffraction (XRD) patterns, this indicates that ZnO nanowires exhibit (001) preferred orientation. The scanning electronic microscope (SEM) images show that the average diameter is 100 nm and the average length is 4 μm. They are aligned on Si substrate well. While substrates facing up, the ZnO thin film of thickness of 500 nm is deposited on Si substrate firstly and ZnO nanowires grow on the ZnO thin films. And while substrates facing down, epitaxial ZnO nanowires grow on the substrates. The result indicates that the exposure of substrate affects the growth mechanism of ZnO nanowires.
2009, 38(1): 137-140.
Abstract:
A nonlinear compensated bandgap reference based on current-mode is designed, The reference exhibits low temperature drift and low power consumption. The temperature-related nonlinear item in the VBF of a bipolar transistor can be compensated by adding a bipolar transistor and two resistors to conventional circuit. Implemented in CSMC 0.5 μm double poly triple metal CMOS technology, the proposed bandgap reference delivers an output voltage of 1.217 V with 3.3 V supply at 27℃. A temperature coefficient of 4.6 ppm/℃ from -40℃ to 125℃ and a line regulation of 1.6 mV/V from 2.6 V to 4 V are achieved after trimming. The power dissipation of the circuit is just 0.21 mW with 3.3 V supply.
A nonlinear compensated bandgap reference based on current-mode is designed, The reference exhibits low temperature drift and low power consumption. The temperature-related nonlinear item in the VBF of a bipolar transistor can be compensated by adding a bipolar transistor and two resistors to conventional circuit. Implemented in CSMC 0.5 μm double poly triple metal CMOS technology, the proposed bandgap reference delivers an output voltage of 1.217 V with 3.3 V supply at 27℃. A temperature coefficient of 4.6 ppm/℃ from -40℃ to 125℃ and a line regulation of 1.6 mV/V from 2.6 V to 4 V are achieved after trimming. The power dissipation of the circuit is just 0.21 mW with 3.3 V supply.
2009, 38(1): 141-143.
Abstract:
A new type of integrated optical waveguide magnetic field probe was proposed for electromagnetic compatibility test. The probe head is constituted with a LiNbO3 optical waveguide modulator and a doubly-loaded loop antenna element. The magnetic field information can be obtained by detecting the output optical intensity. Compared with the traditional magnetic field probes, it has lower disturbance of measured field, and can suppress the electrical influence effectively. Simulation result is consistent with the theoretical analysis.
A new type of integrated optical waveguide magnetic field probe was proposed for electromagnetic compatibility test. The probe head is constituted with a LiNbO3 optical waveguide modulator and a doubly-loaded loop antenna element. The magnetic field information can be obtained by detecting the output optical intensity. Compared with the traditional magnetic field probes, it has lower disturbance of measured field, and can suppress the electrical influence effectively. Simulation result is consistent with the theoretical analysis.
2009, 38(1): 144-147.
Abstract:
While a spatial object is observed by a ground detection system, some important influence of cirrus scattering on the target detection and identification might occur. In this paper, a review of single scattering and distribution properties of regular geometric cirrus particle is given. Micro physical properties are analyzed ulteriorly. Based on an assumption that size distribution of cirrus particles is a Gamma function, the phase function with the scattering angle is simulated within wavelength 0.4 mm to 4 mm and effective radius 10 mm to 120 mm. An approximate model of multiple scattering probability concerning ice crystal particles and photons is proposed. Numerical results show that optical depth of cirrus increases with the order of multiple scattering.
While a spatial object is observed by a ground detection system, some important influence of cirrus scattering on the target detection and identification might occur. In this paper, a review of single scattering and distribution properties of regular geometric cirrus particle is given. Micro physical properties are analyzed ulteriorly. Based on an assumption that size distribution of cirrus particles is a Gamma function, the phase function with the scattering angle is simulated within wavelength 0.4 mm to 4 mm and effective radius 10 mm to 120 mm. An approximate model of multiple scattering probability concerning ice crystal particles and photons is proposed. Numerical results show that optical depth of cirrus increases with the order of multiple scattering.
2009, 38(1): 148-151.
Abstract:
By considering the difference of all kinds of optical paths, the echo signal from plane target in underwater detection is analyzed. The power equation of the echo signal is deduced. The factors to influence the signal power, such as the size of target, the parameters of water and the angles of incidence etc., are simulated and analyzed. The result indicates that the received power will reduce as the transmission distance and the parameters of water increase; but it will increase as the size of target increases.
By considering the difference of all kinds of optical paths, the echo signal from plane target in underwater detection is analyzed. The power equation of the echo signal is deduced. The factors to influence the signal power, such as the size of target, the parameters of water and the angles of incidence etc., are simulated and analyzed. The result indicates that the received power will reduce as the transmission distance and the parameters of water increase; but it will increase as the size of target increases.
2009, 38(1): 152-156.
Abstract:
By using magnetostrictive characteristics of Tb0.3Dy0.7Fe1.95 to tune the time-delay line of linear chirped fiber grating (CFG), the ends of linear CFG are pasted firmly to the magnetostrictive rod with length of 70 mm and diameter of 8 mm. The center wavelength of the grating is 1 550 nm, the FWHM bandwidth is 15.48 nm and its length is 60 mm. The magnetostrictive rod is laid into a uniform magnetic field of coil. When the current in the solenoid changes from 0 A to 2 A, the grating gets a axial strain and the spectrum shifts about 1.6 nm to the longer wavelength, consequently, the maximum time-delay change, 60 ps, is achieved. The setup can make a four-elements optical-controlled phased array antenna with the element spacing of 0.006 m realize the scanning angles from 0°to 90°.
By using magnetostrictive characteristics of Tb0.3Dy0.7Fe1.95 to tune the time-delay line of linear chirped fiber grating (CFG), the ends of linear CFG are pasted firmly to the magnetostrictive rod with length of 70 mm and diameter of 8 mm. The center wavelength of the grating is 1 550 nm, the FWHM bandwidth is 15.48 nm and its length is 60 mm. The magnetostrictive rod is laid into a uniform magnetic field of coil. When the current in the solenoid changes from 0 A to 2 A, the grating gets a axial strain and the spectrum shifts about 1.6 nm to the longer wavelength, consequently, the maximum time-delay change, 60 ps, is achieved. The setup can make a four-elements optical-controlled phased array antenna with the element spacing of 0.006 m realize the scanning angles from 0°to 90°.
2009, 38(1): 157-160.
Abstract:
A new method to rectify the optical axis based on visual servoing is given in this paper. This method separates the linear distortion from the non-linear distortion. Firstly, the non-linear distortion is removed through iterations on the basis of the non-linear distortion coefficients obtained by accurately calibrating camera with many pattern images. Then the position of the camera is finely adjusted by a way of feedback elements according to the linear distortion without special guiding equipment. With the help of this method, finally the problem of rectification of optical axis is perfectly solved.
A new method to rectify the optical axis based on visual servoing is given in this paper. This method separates the linear distortion from the non-linear distortion. Firstly, the non-linear distortion is removed through iterations on the basis of the non-linear distortion coefficients obtained by accurately calibrating camera with many pattern images. Then the position of the camera is finely adjusted by a way of feedback elements according to the linear distortion without special guiding equipment. With the help of this method, finally the problem of rectification of optical axis is perfectly solved.
