ISSN 
2008 Vol. 37, No. 3
2008, 37(3): 321-324.
Abstract:
When the range-Doppler algorithm is used in inverse synthetic aperture radar (ISAR) imaging, the reduction of echo correlation will add more difficulties on motion compensation and bring more error. Accordingly, based on the adjacent-correlate compensate method used in FFT range-Doppler algorithm, an improved compensation method is presented in this paper. The traditional compensation method is modified to avoid the envelope drift and envelope jump in range align. In phase compensation, a new algorithm based on accurate target parameter estimation by use of discrete chirp-Fourier transform (DCFT) transform is presented. Finally the improve method is verified by simulation.
When the range-Doppler algorithm is used in inverse synthetic aperture radar (ISAR) imaging, the reduction of echo correlation will add more difficulties on motion compensation and bring more error. Accordingly, based on the adjacent-correlate compensate method used in FFT range-Doppler algorithm, an improved compensation method is presented in this paper. The traditional compensation method is modified to avoid the envelope drift and envelope jump in range align. In phase compensation, a new algorithm based on accurate target parameter estimation by use of discrete chirp-Fourier transform (DCFT) transform is presented. Finally the improve method is verified by simulation.
2008, 37(3): 325-327,353.
Abstract:
In this paper, a new level set synthetic aperture radar (SAR) image segmentation approach based on region and edge information is proposed. An energy functional which is adapted for SAR image segmentation is defined. The energy functional consists of a region-based term derived from maximum-likelihood estimation of a mixed Gamma model and a boundary-based term derived from geodesic active contour model. Partial differential equations (PDEs) of curve evolution are obtained by minimization of the energy functional. To implement image segmentation, the solution of the PDEs by a level set approach is proposed. The efficiency of the method is verified by both synthetic and real SAR images. Experimental results implement the more accurate and rapid SAR images segmentation without preprocessing steps to filter speckle noise.
In this paper, a new level set synthetic aperture radar (SAR) image segmentation approach based on region and edge information is proposed. An energy functional which is adapted for SAR image segmentation is defined. The energy functional consists of a region-based term derived from maximum-likelihood estimation of a mixed Gamma model and a boundary-based term derived from geodesic active contour model. Partial differential equations (PDEs) of curve evolution are obtained by minimization of the energy functional. To implement image segmentation, the solution of the PDEs by a level set approach is proposed. The efficiency of the method is verified by both synthetic and real SAR images. Experimental results implement the more accurate and rapid SAR images segmentation without preprocessing steps to filter speckle noise.
2008, 37(3): 328-330.
Abstract:
The major problem to make precision mobile location is the nonline of light (NLOS) effect. It adds positive error to time of arrival (TOA) measures, the linear filter can not effectively deal with the NLOS error, because the linear filter mainly bases on the Gaussian noise. In this paper, a nonlinear LMS algorithm is brought forward to mitigate the NLOS effect on location precision. It regards NLOS error as the impulse noise and reconstructs the TOA measures by using the non-linear objective function. The simulation results justify the proposed algorithm.
The major problem to make precision mobile location is the nonline of light (NLOS) effect. It adds positive error to time of arrival (TOA) measures, the linear filter can not effectively deal with the NLOS error, because the linear filter mainly bases on the Gaussian noise. In this paper, a nonlinear LMS algorithm is brought forward to mitigate the NLOS effect on location precision. It regards NLOS error as the impulse noise and reconstructs the TOA measures by using the non-linear objective function. The simulation results justify the proposed algorithm.
2008, 37(3): 331-334.
Abstract:
The influence of two kinds of algorithm initial values on results in bearing-only passive location is described with geometry method. Via adding the difference of phase as a new measurement vector, converting the nonlinear system to linear system, a way to avoid this influence is proposed. In the linear system, Kalman filtering (KF) is used, and the initial values can be gotten from the measured values. Simulations show that this way can eliminate the initial value's influence, and the relative error of distance is less than 2%.
The influence of two kinds of algorithm initial values on results in bearing-only passive location is described with geometry method. Via adding the difference of phase as a new measurement vector, converting the nonlinear system to linear system, a way to avoid this influence is proposed. In the linear system, Kalman filtering (KF) is used, and the initial values can be gotten from the measured values. Simulations show that this way can eliminate the initial value's influence, and the relative error of distance is less than 2%.
2008, 37(3): 335-338.
Abstract:
The ionospheric layer movement produces frequency modulation for the HF sky-wave radar signal such that the sea clutter is broadened in Doppler domain. Compensation for the modulation is significant before radar coherent integration. This paper addresses a modified adaptive short time Fourier transform (MASTFT) and proposes a MASTFT-based compensation method. Experimental tests are constructed by inducing the contamination of simulative traveling ionospheric disturbance (TID) to the undisturbed data collected by high frequency surface wave radar (HFSWR). The test results show that the proposed method can effectively compensate even for rapid TID and has good adaptability for different ionospheric frequency modulations.
The ionospheric layer movement produces frequency modulation for the HF sky-wave radar signal such that the sea clutter is broadened in Doppler domain. Compensation for the modulation is significant before radar coherent integration. This paper addresses a modified adaptive short time Fourier transform (MASTFT) and proposes a MASTFT-based compensation method. Experimental tests are constructed by inducing the contamination of simulative traveling ionospheric disturbance (TID) to the undisturbed data collected by high frequency surface wave radar (HFSWR). The test results show that the proposed method can effectively compensate even for rapid TID and has good adaptability for different ionospheric frequency modulations.
2008, 37(3): 339-342.
Abstract:
A new operation model for joint optical multi-band detection systems is provided corresponding to the different characters of the detection probabilities of subsystems. It leads to a higher over-all detection probability. The joint optical detection system is able to operate under different models when detection probabilities of subsystems are low and when there is big difference among the probabilities. The joint optical detection detection system directly conducts data fusing under the former condition. And information from the subsystems is chosen before entering the fusion center under the latter condition. In this way, the false-alarm probability of a joint optical detection system reduces obviously comparing with direct data fusion.
A new operation model for joint optical multi-band detection systems is provided corresponding to the different characters of the detection probabilities of subsystems. It leads to a higher over-all detection probability. The joint optical detection system is able to operate under different models when detection probabilities of subsystems are low and when there is big difference among the probabilities. The joint optical detection detection system directly conducts data fusing under the former condition. And information from the subsystems is chosen before entering the fusion center under the latter condition. In this way, the false-alarm probability of a joint optical detection system reduces obviously comparing with direct data fusion.
2008, 37(3): 343-346.
Abstract:
A novel approach of deterministic blind beamforming (DBBF) for broadband nonstationary source separation is presented in this paper. Utilizing the nonstationarity of broadband sources, the conventional narrowband DBBF, based on rotational invariance techniques, is extended to the broadband case, and implemented in frequency domain. A channel rearranging operation, exploring the correlation coefficients between the separated sequences of adjacent bins, is performed to cope with the channel swap. Then the frequency consistency of the recovered sources can be ensured. In addition, the problem of scale ambiguity is eliminated and the original sources can be recovered without scale distortion. Numerical examples confirm the excellent performance of the proposed approach.
A novel approach of deterministic blind beamforming (DBBF) for broadband nonstationary source separation is presented in this paper. Utilizing the nonstationarity of broadband sources, the conventional narrowband DBBF, based on rotational invariance techniques, is extended to the broadband case, and implemented in frequency domain. A channel rearranging operation, exploring the correlation coefficients between the separated sequences of adjacent bins, is performed to cope with the channel swap. Then the frequency consistency of the recovered sources can be ensured. In addition, the problem of scale ambiguity is eliminated and the original sources can be recovered without scale distortion. Numerical examples confirm the excellent performance of the proposed approach.
2008, 37(3): 347-349.
Abstract:
One of the most important issues of pulse position modulation (PPM) for optical wireless communications is the receiver symbol synchronization subsystem, in this paper, the basic principle of symbol synchronization for PPM sequence is discussed, and the upper limit of exact synchronization probability for random PPM sequence is analyzed. To solve this problem a new scheme of inserting synchronous back-to-back PPM symbols to the PPM sequence at intervals of certain symbols is presented, the synchronization signal is obtained by searching for the synchronous symbols, and the corresponding digital logic circuit is presented too. Theory and experiment results show that the exact PPM symbol synchronization can be obtained by this scheme with more credibility compared to the scheme proposed by Ref.[8].
One of the most important issues of pulse position modulation (PPM) for optical wireless communications is the receiver symbol synchronization subsystem, in this paper, the basic principle of symbol synchronization for PPM sequence is discussed, and the upper limit of exact synchronization probability for random PPM sequence is analyzed. To solve this problem a new scheme of inserting synchronous back-to-back PPM symbols to the PPM sequence at intervals of certain symbols is presented, the synchronization signal is obtained by searching for the synchronous symbols, and the corresponding digital logic circuit is presented too. Theory and experiment results show that the exact PPM symbol synchronization can be obtained by this scheme with more credibility compared to the scheme proposed by Ref.[8].
2008, 37(3): 350-353.
Abstract:
An optimum MAP Turbo joint detection (JD) technology is studied for TD-SCDMA mobile communication system. A simple scheme is proposed in order to reduce the computational complexity. The performance of MAP Turbo JD algorithms are simulated for a TD-SCDMA uplink transmission. The result shows that the simple MAP Turbo JD scheme yields much better performance than the linear joint detection, and its computational complexity is much lower than the optimum algorithm.
An optimum MAP Turbo joint detection (JD) technology is studied for TD-SCDMA mobile communication system. A simple scheme is proposed in order to reduce the computational complexity. The performance of MAP Turbo JD algorithms are simulated for a TD-SCDMA uplink transmission. The result shows that the simple MAP Turbo JD scheme yields much better performance than the linear joint detection, and its computational complexity is much lower than the optimum algorithm.
2008, 37(3): 354-357.
Abstract:
It's necessary to evaluate the performance of satellite navigation receivers regularly. Due to the limitation of available instruments and related measuring methods, however, It is very difficult to verify the precision of motion velocity measurement of the receivers. For this reason, one of the measurement methodologies for dynamic measuring implemented by navigation receiver is reported on the background of global positioning system (GPS). The principle for passive motion velocity measuring of navigation receivers is discussed, and the fundamental architecture of navigation signal simulator which imitates and generates satellite signals is analyzed. An expected carrier wave frequency-shifting, by which the theoretic values of motion velocity would be derived, can be obtained via careful adjustment of time delay of the navigation signal simulator, and the measurement precision of receivers can be sequentially certificated via comparing the theoretic values with practical measured values. Provided with the preceding arguments, an approach for precision measurement of motion velocity is eventually presented based on the simulator.
It's necessary to evaluate the performance of satellite navigation receivers regularly. Due to the limitation of available instruments and related measuring methods, however, It is very difficult to verify the precision of motion velocity measurement of the receivers. For this reason, one of the measurement methodologies for dynamic measuring implemented by navigation receiver is reported on the background of global positioning system (GPS). The principle for passive motion velocity measuring of navigation receivers is discussed, and the fundamental architecture of navigation signal simulator which imitates and generates satellite signals is analyzed. An expected carrier wave frequency-shifting, by which the theoretic values of motion velocity would be derived, can be obtained via careful adjustment of time delay of the navigation signal simulator, and the measurement precision of receivers can be sequentially certificated via comparing the theoretic values with practical measured values. Provided with the preceding arguments, an approach for precision measurement of motion velocity is eventually presented based on the simulator.
2008, 37(3): 358-360.
Abstract:
Continuous phase modulation (CPM) is an attractive technique for wireless communications due to its highly power and bandwidth efficiency, but the complexity of the CPM receiver increases exponentially with the modulation parameters. This paper proposes a noncoherent sequence estimation (NSE) algorithm which reduces the complexity of CPM demodulator remarkably. The front-end of the receiver is substituted by signal decomposition followed by vector multiplication, and the sequence decoding part of the back-end is truncated by the exponential window.
Continuous phase modulation (CPM) is an attractive technique for wireless communications due to its highly power and bandwidth efficiency, but the complexity of the CPM receiver increases exponentially with the modulation parameters. This paper proposes a noncoherent sequence estimation (NSE) algorithm which reduces the complexity of CPM demodulator remarkably. The front-end of the receiver is substituted by signal decomposition followed by vector multiplication, and the sequence decoding part of the back-end is truncated by the exponential window.
2008, 37(3): 361-363,392.
Abstract:
A new minimum mean squared error (MMSE) detector based on widely linear processing combined with the decision feedback (DF) strategy for V-BLAST signals is proposed. It can deal with the poor performance of traditional DF detection under higher signal-noise-ratio (SNR). Simulations show that the performance of the proposed scheme utilizing optimal order approaches that of maximum likelihood detection. Furthermore, the algorithm with random order outperforms the Golden MMSE detection. Under the same simulation condition, there is at least 3 dB gain in bit-error-ratio (BER) performance by adopting widely linear processing.
A new minimum mean squared error (MMSE) detector based on widely linear processing combined with the decision feedback (DF) strategy for V-BLAST signals is proposed. It can deal with the poor performance of traditional DF detection under higher signal-noise-ratio (SNR). Simulations show that the performance of the proposed scheme utilizing optimal order approaches that of maximum likelihood detection. Furthermore, the algorithm with random order outperforms the Golden MMSE detection. Under the same simulation condition, there is at least 3 dB gain in bit-error-ratio (BER) performance by adopting widely linear processing.
2008, 37(3): 364-365,369.
Abstract:
A method to design wideband digital receiver on filed programmable gates array (FPGA) is proposed in this paper. The coordinate rotation digital computer (CORDIC) algorithm is employed to generate real time numerically controlled oscillator (NCO) data. Double frequency conversion, quarter decimation and polyphase filters further enhance the system performance. The proposed receiver is more flexible, less computation and less resource consumption. Design example and simulation results are shown to testify the validities and feasibilities.
A method to design wideband digital receiver on filed programmable gates array (FPGA) is proposed in this paper. The coordinate rotation digital computer (CORDIC) algorithm is employed to generate real time numerically controlled oscillator (NCO) data. Double frequency conversion, quarter decimation and polyphase filters further enhance the system performance. The proposed receiver is more flexible, less computation and less resource consumption. Design example and simulation results are shown to testify the validities and feasibilities.
2008, 37(3): 366-369.
Abstract:
In this paper we discussed a feedback loop for carrier frequency offset synchronization in orthogonal frequency division multiplexing (OFDM) systems. The maximum likelihood (ML) algorithm is introduced, and we present an improved frequency offset synchronization method which uses the ML algorithm and the second-order feedback loop jointly. The result of analysis and computer simulation show that the new method can significantly improve the performance of the ML estimators.
In this paper we discussed a feedback loop for carrier frequency offset synchronization in orthogonal frequency division multiplexing (OFDM) systems. The maximum likelihood (ML) algorithm is introduced, and we present an improved frequency offset synchronization method which uses the ML algorithm and the second-order feedback loop jointly. The result of analysis and computer simulation show that the new method can significantly improve the performance of the ML estimators.
2008, 37(3): 370-373.
Abstract:
Channel estimation is a very important problem that has been paid much attention in orthogonal frequency division multiplexing (OFDM) communication system. In this paper, an improved blind OFDM channel estimation algorithm based on maximum likelihood is proposed. The improved algorithm uses the cyclic prefix (CP) processing to implement channel blind estimation. It estimates the influence of the OFDM channel before DFT. The analysis and simulation results show that the method proposed both reduces the computation complexity obviously and improves its performance in theory.
Channel estimation is a very important problem that has been paid much attention in orthogonal frequency division multiplexing (OFDM) communication system. In this paper, an improved blind OFDM channel estimation algorithm based on maximum likelihood is proposed. The improved algorithm uses the cyclic prefix (CP) processing to implement channel blind estimation. It estimates the influence of the OFDM channel before DFT. The analysis and simulation results show that the method proposed both reduces the computation complexity obviously and improves its performance in theory.
2008, 37(3): 374-377.
Abstract:
In this paper, a second-order characteristic window approach to blind signal separation based on short-time stationarity of speech signals is proposed. This approach uses a new whitening algorithm via joint difference correlation matrix to remove the effect of colored noise for one thing, then uses characteristic window that the length is approximately equal to the fundamental period to divide the whitening observation data into series. In every different data frame, time-lag covariance matrices are computed and jointly approximately diagonalized to estimate the rotation parameters which could make the sources obtained. This approach avoids colored noises and separates speech signals only by means of second-order information. Its effectiveness is shown via computer simulation.
In this paper, a second-order characteristic window approach to blind signal separation based on short-time stationarity of speech signals is proposed. This approach uses a new whitening algorithm via joint difference correlation matrix to remove the effect of colored noise for one thing, then uses characteristic window that the length is approximately equal to the fundamental period to divide the whitening observation data into series. In every different data frame, time-lag covariance matrices are computed and jointly approximately diagonalized to estimate the rotation parameters which could make the sources obtained. This approach avoids colored noises and separates speech signals only by means of second-order information. Its effectiveness is shown via computer simulation.
2008, 37(3): 378-381.
Abstract:
For single tone complex signal estimator in the presence of additive white Gaussian noise, based on the autocorrelations, we proposes a statistically improved hybrid estimator that outperforms other recently proposed approaches at lower signal-to-noise ratio (SNR). The Cramér-Rao lower bound is closely followed at moderate SNR. The estimator is applicable to problems in applications requiring low SNR and limited frequency range.
For single tone complex signal estimator in the presence of additive white Gaussian noise, based on the autocorrelations, we proposes a statistically improved hybrid estimator that outperforms other recently proposed approaches at lower signal-to-noise ratio (SNR). The Cramér-Rao lower bound is closely followed at moderate SNR. The estimator is applicable to problems in applications requiring low SNR and limited frequency range.
2008, 37(3): 382-385.
Abstract:
A novel scheme of M-ary spreading communication system using filter-banks for frequency domain equalization (FB-FDE) is proposed for overcoming multi-path fading with large delay and rapid variation of the channel, which is inherent in wideband ground-air communications under low antenna elevation conditions. Because the FB-FDE can remove the effect of dynamical long delay multi-path fading with very simple structure and the M-ary spreading communication system can support code-division multiple-access (CDMA) with high band efficiency, the proposed system is capable of suppressing the dynamic multi-path fading without reducing the channel efficiency. Theoretical analysis and simulation experiments show that the proposed system behaves better than single carrier with frequency domain equalization (SC-FDE) system in transmission performance, so that it should be promising in the applications of wideband ground-air communications with low elevation antenna.
A novel scheme of M-ary spreading communication system using filter-banks for frequency domain equalization (FB-FDE) is proposed for overcoming multi-path fading with large delay and rapid variation of the channel, which is inherent in wideband ground-air communications under low antenna elevation conditions. Because the FB-FDE can remove the effect of dynamical long delay multi-path fading with very simple structure and the M-ary spreading communication system can support code-division multiple-access (CDMA) with high band efficiency, the proposed system is capable of suppressing the dynamic multi-path fading without reducing the channel efficiency. Theoretical analysis and simulation experiments show that the proposed system behaves better than single carrier with frequency domain equalization (SC-FDE) system in transmission performance, so that it should be promising in the applications of wideband ground-air communications with low elevation antenna.
2008, 37(3): 386-388.
Abstract:
The wavelet transform has become a new signal processing technology in last decade, it has been imposed great importance by more and more theoretical workers and engineers. Simultaneity, the mathematical theory of the wavelet transform is complicated. In this paper, the basic theory and advantage of wavelet transform is simply revealed by comparing with Fourier transform and short time Fourier transform, deep cognition and understanding of wavelet transform is given by MATLAB simulation. These result shows that wavelet transform is superior to Fourier transform and short time Fourier transform both in time and frequency orientation in signal processing.
The wavelet transform has become a new signal processing technology in last decade, it has been imposed great importance by more and more theoretical workers and engineers. Simultaneity, the mathematical theory of the wavelet transform is complicated. In this paper, the basic theory and advantage of wavelet transform is simply revealed by comparing with Fourier transform and short time Fourier transform, deep cognition and understanding of wavelet transform is given by MATLAB simulation. These result shows that wavelet transform is superior to Fourier transform and short time Fourier transform both in time and frequency orientation in signal processing.
2008, 37(3): 389-392.
Abstract:
Based on the analysis of the complex transmission zeros' effect on the group delay and S parameters of the general Chebyshev filter, we find out that the real and imaginary parts mainly effect the amplitude and linear of the group delay, respectively. The linear of the filter is improved by adjusting the imaginary parts of the general Chebyshev filters' complex transmission zero. Then a linear phase filter which gives group delay equalization about 50% of the bandwidth (35.5 ±0.7 ns) with six cavites is designed using this method. A good agreement between the measured result and the synthesized one verifies validity of the method.
Based on the analysis of the complex transmission zeros' effect on the group delay and S parameters of the general Chebyshev filter, we find out that the real and imaginary parts mainly effect the amplitude and linear of the group delay, respectively. The linear of the filter is improved by adjusting the imaginary parts of the general Chebyshev filters' complex transmission zero. Then a linear phase filter which gives group delay equalization about 50% of the bandwidth (35.5 ±0.7 ns) with six cavites is designed using this method. A good agreement between the measured result and the synthesized one verifies validity of the method.
2008, 37(3): 393-396.
Abstract:
By analyzing the architecture of current mode DC-DC converter, a novel lossless low-power current-sensing technique for minimizing the static power of DC-DC converter is proposed in the paper. It adopts a lossless current-sensing method and an improved low power current amplifier. The proposed technique can reduce the power of current-sensing circuit and result in the static power optimization of current mode DC-DC converter. Simulation results show that static power of the current mode buck converter based on the proposed technique is 61.22mW, which is only 57.5% compared to the converter with the typical circuit.
By analyzing the architecture of current mode DC-DC converter, a novel lossless low-power current-sensing technique for minimizing the static power of DC-DC converter is proposed in the paper. It adopts a lossless current-sensing method and an improved low power current amplifier. The proposed technique can reduce the power of current-sensing circuit and result in the static power optimization of current mode DC-DC converter. Simulation results show that static power of the current mode buck converter based on the proposed technique is 61.22mW, which is only 57.5% compared to the converter with the typical circuit.
2008, 37(3): 397-400.
Abstract:
Regarding to the chaos stability control, the mechanism of stability control caused by ramp compensation in buck, boost, and buck-boost converters is studied. The corresponding discrete map models are built, and the circuit stability criterions and the slope expressions of compensating ramp are achieved. With their bifurcation diagram, Lyapunov exponent spectrum, and time-domain waveform, the performance of switching converter circuit by utilizing compensating ramp current (or voltage) are given. The research results indicate that the ramp compensation technique can effectively improve stability of switched DC-DC converter.
Regarding to the chaos stability control, the mechanism of stability control caused by ramp compensation in buck, boost, and buck-boost converters is studied. The corresponding discrete map models are built, and the circuit stability criterions and the slope expressions of compensating ramp are achieved. With their bifurcation diagram, Lyapunov exponent spectrum, and time-domain waveform, the performance of switching converter circuit by utilizing compensating ramp current (or voltage) are given. The research results indicate that the ramp compensation technique can effectively improve stability of switched DC-DC converter.
2008, 37(3): 401-403,410.
Abstract:
Quantum key distribution is the most secure technology to distribute a secret key. There is a set of orthogonal product states in a two-qubit three-state quantum system which can show nonlocality. This paper provides a quantum key distribution protocol based otn the nonlocality of such system. The two parties establish the key by exchanging quantum qubits and performing the collective measurement on them. The laws of quantum mechanics guarantee that this protocol is unconditionally secure. No other people can get the key without being found. There are no entangled states and quantum operations needed in the protocol. So it is easier to carry out in practice. And it can gain high reliability and robustness.
Quantum key distribution is the most secure technology to distribute a secret key. There is a set of orthogonal product states in a two-qubit three-state quantum system which can show nonlocality. This paper provides a quantum key distribution protocol based otn the nonlocality of such system. The two parties establish the key by exchanging quantum qubits and performing the collective measurement on them. The laws of quantum mechanics guarantee that this protocol is unconditionally secure. No other people can get the key without being found. There are no entangled states and quantum operations needed in the protocol. So it is easier to carry out in practice. And it can gain high reliability and robustness.
2008, 37(3): 404-407.
Abstract:
A special equation is constructed based on large integer factoring problem (LIFP) and a parameter is introduced to transfer service private-key. The session key can be obtained by using the special equation and the service private-key in decryption. On the basis of the above, a multi-service oriented traitor tracing scheme on LIFP is proposed. It has many advantages such as multi-service, black-box traitor tracing, ciphertexts of constant size, adding or revoking users, and forward and backward security. Its whole capabilities are also better than the existing ones.
A special equation is constructed based on large integer factoring problem (LIFP) and a parameter is introduced to transfer service private-key. The session key can be obtained by using the special equation and the service private-key in decryption. On the basis of the above, a multi-service oriented traitor tracing scheme on LIFP is proposed. It has many advantages such as multi-service, black-box traitor tracing, ciphertexts of constant size, adding or revoking users, and forward and backward security. Its whole capabilities are also better than the existing ones.
2008, 37(3): 408-410.
Abstract:
Based on the crystal-field theory, the anisotropic g factors of the trigonal Ru3+ center in α-Al2O3 are theoretically studied by using the perturbation formulas of the g factors for a 4d5 ion in trigonal symmetry. In these formulas, the orbital reduction factor k and the spin-orbit coupling parameter ζd for the impurity Ru3+ in the crystal as well as their contributions to the g factors are taken into account in a uniform way. The calculated results show good agreement with the experimental data. In addition, the local structure property of the impurity center is also discussed.
Based on the crystal-field theory, the anisotropic g factors of the trigonal Ru3+ center in α-Al2O3 are theoretically studied by using the perturbation formulas of the g factors for a 4d5 ion in trigonal symmetry. In these formulas, the orbital reduction factor k and the spin-orbit coupling parameter ζd for the impurity Ru3+ in the crystal as well as their contributions to the g factors are taken into account in a uniform way. The calculated results show good agreement with the experimental data. In addition, the local structure property of the impurity center is also discussed.
2008, 37(3): 411-413,420.
Abstract:
A 8-millimeter-wave-band relativistic diffraction generator with a coaxial reflector is studied on this paper. High frequency system of the device is a slow-wave structure with a combination of rectangles and semicircles. A coaxial reflector is situated at the upstream entrance of the slow-wave structure. The parameter of reflector is obtained by calculating the S11 parameter by the software HFSS. The non-linear process of beam-wave interaction with the reflector is investigated on particle-in-cell (PIC) simulation. The result shows that there is the best location of the reflector, which makes the device have a maximum efficiency and single operation frequency.
A 8-millimeter-wave-band relativistic diffraction generator with a coaxial reflector is studied on this paper. High frequency system of the device is a slow-wave structure with a combination of rectangles and semicircles. A coaxial reflector is situated at the upstream entrance of the slow-wave structure. The parameter of reflector is obtained by calculating the S11 parameter by the software HFSS. The non-linear process of beam-wave interaction with the reflector is investigated on particle-in-cell (PIC) simulation. The result shows that there is the best location of the reflector, which makes the device have a maximum efficiency and single operation frequency.
2008, 37(3): 414-416.
Abstract:
This paper presents a novel conception that intense relativstic electron beam is accelerated by compact electrostatic accelerator cube. According to the theoretic analysis and PIC, the electron beam with current 1 kA and initial voltage 500 kV is accelerated in the accelerator of 0.8 m and it becomes 10 MeV. The beam is transported and accelerated without focusing magnetic field. The biggest electronic field can be decreased 20 MV/m by optimization design.
This paper presents a novel conception that intense relativstic electron beam is accelerated by compact electrostatic accelerator cube. According to the theoretic analysis and PIC, the electron beam with current 1 kA and initial voltage 500 kV is accelerated in the accelerator of 0.8 m and it becomes 10 MeV. The beam is transported and accelerated without focusing magnetic field. The biggest electronic field can be decreased 20 MV/m by optimization design.
2008, 37(3): 417-420.
Abstract:
The characteristic equation of THz photonic crystal fibers is obtained with effective refractive index method. The mode distribution and dispersion are discussed. It's found that when air hole pitch is fixed, the cladding effective refractive index of photonic crystal fiber (PCFs), the cut-off frequency of higher modes, and the frequency of maximum and zero dispersion will become larger, the maximum dispersion will become smaller if the air hole radius decreases; when air-filling fraction is fixed, the cladding effective refractive index, the cut-off frequency of higher modes, and the maximum dispersion will become larger, the frequency of maximum and zero dispersion will become smaller if air hole radius increases. The transmission with single-mode zero dispersion in THz region can be realized according to the changes of air hole pitch and the air hole radius.
The characteristic equation of THz photonic crystal fibers is obtained with effective refractive index method. The mode distribution and dispersion are discussed. It's found that when air hole pitch is fixed, the cladding effective refractive index of photonic crystal fiber (PCFs), the cut-off frequency of higher modes, and the frequency of maximum and zero dispersion will become larger, the maximum dispersion will become smaller if the air hole radius decreases; when air-filling fraction is fixed, the cladding effective refractive index, the cut-off frequency of higher modes, and the maximum dispersion will become larger, the frequency of maximum and zero dispersion will become smaller if air hole radius increases. The transmission with single-mode zero dispersion in THz region can be realized according to the changes of air hole pitch and the air hole radius.
2008, 37(3): 421-423,449.
Abstract:
The traditional independent component analysis is based on statistics mean of all aposteriori data and dismissed geometry. The classical lagrange constraint neural network (LCNN) employs Helmholtz free energy to unify supervised and unsupervised learning, and uses aprior and multi-sensing to solve independent components in one pixel, whose geometrical grain reached single pixel. The operations among pixels can be completely run parallelly. However, the constraints of classical LCNN bring ill-conditional matrix. In this paper, the real meaning of the constraints λ is discussed, four fast LCNN algorithms are proposed, the independent component (IC) models of still image is analyzed, and a new sub-pixel IC model is presented.
The traditional independent component analysis is based on statistics mean of all aposteriori data and dismissed geometry. The classical lagrange constraint neural network (LCNN) employs Helmholtz free energy to unify supervised and unsupervised learning, and uses aprior and multi-sensing to solve independent components in one pixel, whose geometrical grain reached single pixel. The operations among pixels can be completely run parallelly. However, the constraints of classical LCNN bring ill-conditional matrix. In this paper, the real meaning of the constraints λ is discussed, four fast LCNN algorithms are proposed, the independent component (IC) models of still image is analyzed, and a new sub-pixel IC model is presented.
2008, 37(3): 424-427.
Abstract:
This paper adopts a novel approach to reduction techniques of serial and parallel connection models in the normal generalized stochastic Petri net (NGSPN). The equivalent theorems of reducing the NGSPN's serial connection model is deduced. An availability method for reducing the parallel connection model is proposed and emulated. We also present an asymptotic formula for reducing the two parallel transitions connection model under independent and non-identically distributed cases. The proposed theorems and methods are especially useful in modeling and analyzing complex and large scale systems with Petri net.
This paper adopts a novel approach to reduction techniques of serial and parallel connection models in the normal generalized stochastic Petri net (NGSPN). The equivalent theorems of reducing the NGSPN's serial connection model is deduced. An availability method for reducing the parallel connection model is proposed and emulated. We also present an asymptotic formula for reducing the two parallel transitions connection model under independent and non-identically distributed cases. The proposed theorems and methods are especially useful in modeling and analyzing complex and large scale systems with Petri net.
2008, 37(3): 428-431.
Abstract:
Multi-level delegation mechanism that meets management structure in most of organizations is an important strategy of authorization. Present Vega grid model has not discussed it deeply, and then the application is subject to certain restrictions because of lack of it. An authorization model with delegation based on Vega grid is proposed, meanwhile, authorities' collection and affiliation, subjects' collection and multi-level segmentation, resources-operation collection and authoritative relationship are formally defined. In addition, not only are search algorithm and data structure that implement the model also proposed, also quantitative analysis of its performance is done. The model supports multi-level delegation under the premise of generalization and ease of use, which extends Vega grid model to fit practical applications better.
Multi-level delegation mechanism that meets management structure in most of organizations is an important strategy of authorization. Present Vega grid model has not discussed it deeply, and then the application is subject to certain restrictions because of lack of it. An authorization model with delegation based on Vega grid is proposed, meanwhile, authorities' collection and affiliation, subjects' collection and multi-level segmentation, resources-operation collection and authoritative relationship are formally defined. In addition, not only are search algorithm and data structure that implement the model also proposed, also quantitative analysis of its performance is done. The model supports multi-level delegation under the premise of generalization and ease of use, which extends Vega grid model to fit practical applications better.
2008, 37(3): 432-435.
Abstract:
This paper presents a method based on analytical hierarchy process (AHP) for neural network ensemble. In the method, five subsystems are constructed. Those neural networks compute parallel which have been trained solely. The decisions are made. Correct classification rates are obtained from the mat lab simulation. In experiments, the proposed methods have been successfully evaluated using thirteen different datasets, it is more effective than the relative majority voting scheme, it can be applicable to other method of pattern recognition.
This paper presents a method based on analytical hierarchy process (AHP) for neural network ensemble. In the method, five subsystems are constructed. Those neural networks compute parallel which have been trained solely. The decisions are made. Correct classification rates are obtained from the mat lab simulation. In experiments, the proposed methods have been successfully evaluated using thirteen different datasets, it is more effective than the relative majority voting scheme, it can be applicable to other method of pattern recognition.
2008, 37(3): 436-438,456.
Abstract:
The reliability of network reflects one aspect of network's performance, it plays an important part in the evaluation of system performance. Is this paper, a new estimate index of network reliability is introduced and an incidence matrix is used to depict the connectivity of the network nodes in a dynamic network model. A determinant arithmetic of the network connectivity and a calculate method are presented to achieve reliavility evaluation for Ad hoc network. Simulation results through random trials indicate that the method presented in this paper is usable to validate the reliability of the dynamic Ad hoc network.
The reliability of network reflects one aspect of network's performance, it plays an important part in the evaluation of system performance. Is this paper, a new estimate index of network reliability is introduced and an incidence matrix is used to depict the connectivity of the network nodes in a dynamic network model. A determinant arithmetic of the network connectivity and a calculate method are presented to achieve reliavility evaluation for Ad hoc network. Simulation results through random trials indicate that the method presented in this paper is usable to validate the reliability of the dynamic Ad hoc network.
2008, 37(3): 439-442.
Abstract:
This paper proposes a new algorithm for document-word co-clustering. After mining semantics with word hyperclique patterns, the document dataset with a bipartite graph is described. Then, the efficient graph partitioning algorithm is employed to partition this graph, so that the high computational overhead of traditional clustering algorithms over huge document datasests can be avoided. During clustering, word hyperclique patterns that are full of document semantics are preserved. In this way, our algorithm partially circumvents the problem of loosing document semantics, which happens a lot in traditional clustering algorithms based on document pairwise similarity alone. Finally, the extensive experimental results demonstrated the effectiveness of this algorithm in document clustering accuracy and cluster topic detection.
This paper proposes a new algorithm for document-word co-clustering. After mining semantics with word hyperclique patterns, the document dataset with a bipartite graph is described. Then, the efficient graph partitioning algorithm is employed to partition this graph, so that the high computational overhead of traditional clustering algorithms over huge document datasests can be avoided. During clustering, word hyperclique patterns that are full of document semantics are preserved. In this way, our algorithm partially circumvents the problem of loosing document semantics, which happens a lot in traditional clustering algorithms based on document pairwise similarity alone. Finally, the extensive experimental results demonstrated the effectiveness of this algorithm in document clustering accuracy and cluster topic detection.
2008, 37(3): 443-445,449.
Abstract:
A novel method for the production of nanoscale polymeric multilayer films of ferroelectric PVDF/PDDA is presented. The ultrathin multilayer film of poly (diallyldimethylammonium chloride) (PDDA) and polyvinylidene fluoride (PVDF) has been prepared by the layer-by-layer static self-assembly (LbL-SA) method. The PVDF/PDDA multilayer film with the thickness ranging from about 30nm to 150 nm (the thickness of each layer is about 9nm.) is characterized by quartz crystal microbalance (QCM), atomic force microscope (AFM), X-ray diffraction (XRD), and infrared spectra (IR). The QCM reveals that the alternate ultrathin films of PVDF and PDDA are well orderly assembled. AFM results indicate that PVDF/PDDA polymeric multilayer film with high uniformity has been obtained. Compared with PVDF thick film, resistivity of PVDF/PDDA ultrathin film is dramatically enhanced.
A novel method for the production of nanoscale polymeric multilayer films of ferroelectric PVDF/PDDA is presented. The ultrathin multilayer film of poly (diallyldimethylammonium chloride) (PDDA) and polyvinylidene fluoride (PVDF) has been prepared by the layer-by-layer static self-assembly (LbL-SA) method. The PVDF/PDDA multilayer film with the thickness ranging from about 30nm to 150 nm (the thickness of each layer is about 9nm.) is characterized by quartz crystal microbalance (QCM), atomic force microscope (AFM), X-ray diffraction (XRD), and infrared spectra (IR). The QCM reveals that the alternate ultrathin films of PVDF and PDDA are well orderly assembled. AFM results indicate that PVDF/PDDA polymeric multilayer film with high uniformity has been obtained. Compared with PVDF thick film, resistivity of PVDF/PDDA ultrathin film is dramatically enhanced.
2008, 37(3): 446-449.
Abstract:
Composite of nanosized α-Fe and barium-W (Ba-W) hexaferrite phase has been synthesized by the ceramic processing rout. Pure Ba-W hexaferrite (Ba(Zn0.7Co0.3)2Fe16O27) was firstly prepared by calcinations. At different temperature, partly, the hexaferriet phase changed into FeCo metallic phase and BaFe2O4. These conclusions are based on the results of X-ray diffraction. The study of magnetic properties at microwave frequency shows that the permeability spectra changes from the type of ferromagnetic resonance into the type relaxation. The loss mechanism changes obviously.
Composite of nanosized α-Fe and barium-W (Ba-W) hexaferrite phase has been synthesized by the ceramic processing rout. Pure Ba-W hexaferrite (Ba(Zn0.7Co0.3)2Fe16O27) was firstly prepared by calcinations. At different temperature, partly, the hexaferriet phase changed into FeCo metallic phase and BaFe2O4. These conclusions are based on the results of X-ray diffraction. The study of magnetic properties at microwave frequency shows that the permeability spectra changes from the type of ferromagnetic resonance into the type relaxation. The loss mechanism changes obviously.
2008, 37(3): 450-452,463.
Abstract:
Pb(Zr0.52Ti0.48)O3 (PZT) nano-powder was prepared efficiently by hydrothermal method, with the characteristics of good dispersion, small grain, high sintering activity and so on. From the theory of electrolyte solution and the idea of crystallography, the particularity of physical and chemical environment for preparing PZT nano-powder is discussed. The driving force of forming nuclei and crystal growth of PZT nano-crystal are analyzed.
Pb(Zr0.52Ti0.48)O3 (PZT) nano-powder was prepared efficiently by hydrothermal method, with the characteristics of good dispersion, small grain, high sintering activity and so on. From the theory of electrolyte solution and the idea of crystallography, the particularity of physical and chemical environment for preparing PZT nano-powder is discussed. The driving force of forming nuclei and crystal growth of PZT nano-crystal are analyzed.
2008, 37(3): 453-456.
Abstract:
A bandgap voltage reference circuit using 0.5 μm complementary metal oxide semiconductor transistor (CMOS) N-well process is presented in the paper. The circuit has high power supply rejection ratio (PSRR) and low-temperature coefficient. The bias voltages of core circuit is independent to the power supply voltage, and the whole bandgap circuit has high PSRR through adding the power supply to the operational amplifier of which the output voltage is supplied for the core circuit. The simulation results for this circuit using SPECTRE show that the PSRR is 116 dB, the temperature coefficient from -40℃ to 85℃ temperature range is 46 ppm/℃ and the power consumption is only 1.45 mW. The bandgap discussed in this paper can be widely used in ADC, DAC, reference circuit and so on.
A bandgap voltage reference circuit using 0.5 μm complementary metal oxide semiconductor transistor (CMOS) N-well process is presented in the paper. The circuit has high power supply rejection ratio (PSRR) and low-temperature coefficient. The bias voltages of core circuit is independent to the power supply voltage, and the whole bandgap circuit has high PSRR through adding the power supply to the operational amplifier of which the output voltage is supplied for the core circuit. The simulation results for this circuit using SPECTRE show that the PSRR is 116 dB, the temperature coefficient from -40℃ to 85℃ temperature range is 46 ppm/℃ and the power consumption is only 1.45 mW. The bandgap discussed in this paper can be widely used in ADC, DAC, reference circuit and so on.
2008, 37(3): 457-459.
Abstract:
Due to the common problems such as low efficiency of red organic electroluminescence (EL) devices, considerable improvement in devices performance has been achieved by optimizing doped emitting materials. High efficient doped red organic light-emitting diodes (OLEDs) were investigated by 9,10-di-betanaphthylanthracene (AND) via thermal vacuum deposition method. Red organic EL devices with the structure of ITO/NPB/ADN:AlQ (20%):DCJTB(2%)/AlQ/Mg:Ag/Al had red light-emission with CIE coordinates of (0.59, 0.41), Maximum luminance of 3 000 cd/m2, and maximum luminance efficiency of 2.54 lm/W. The peak of EL spectrum of the device locates at 598 nm.
Due to the common problems such as low efficiency of red organic electroluminescence (EL) devices, considerable improvement in devices performance has been achieved by optimizing doped emitting materials. High efficient doped red organic light-emitting diodes (OLEDs) were investigated by 9,10-di-betanaphthylanthracene (AND) via thermal vacuum deposition method. Red organic EL devices with the structure of ITO/NPB/ADN:AlQ (20%):DCJTB(2%)/AlQ/Mg:Ag/Al had red light-emission with CIE coordinates of (0.59, 0.41), Maximum luminance of 3 000 cd/m2, and maximum luminance efficiency of 2.54 lm/W. The peak of EL spectrum of the device locates at 598 nm.
2008, 37(3): 460-463.
Abstract:
A measurement system is set up which could measure static optoelectronic characteristics of avalanche photodiodes (APDs). By using this system, the mesa-structure InP/InGaAs APDs is measured. The results show that the APDs have a relatively low dark current (~150 nA at 90% of breakdown) and a uniform photoresponse profile of about 500 μm diameter. A method of getting APDs's multiplication gain is also proposed. Through getting the photocurrent at the point where multiplication is beginning, the multiplication gain can be obtained by the simple current-voltage equipment. For InP/InGaAs APDs, the typical maximum multiplication gain measured by this method is about 10~100.
A measurement system is set up which could measure static optoelectronic characteristics of avalanche photodiodes (APDs). By using this system, the mesa-structure InP/InGaAs APDs is measured. The results show that the APDs have a relatively low dark current (~150 nA at 90% of breakdown) and a uniform photoresponse profile of about 500 μm diameter. A method of getting APDs's multiplication gain is also proposed. Through getting the photocurrent at the point where multiplication is beginning, the multiplication gain can be obtained by the simple current-voltage equipment. For InP/InGaAs APDs, the typical maximum multiplication gain measured by this method is about 10~100.
2008, 37(3): 464-465,473.
Abstract:
Amlodipine maleate is a new kind of medicine for hypertensive disease. This article mainly studies the conditions of quantitatively measuring amlodipine maleate of tablet. The double-wave, 365 nm and 425 nm, spectrophotometry was used for determining the content of the amlodipine maleate tablet to eliminate interference of excipient. The absorbance is well linear with concentration between 5.0 μg/ml and 50.0 μg/ml, and the linear equation of differential spectrophotometry is △A=0.01149C+0.003 (r=0.9994), the coefficient of recovery is 99.92%, and RSD is 0.67%.
Amlodipine maleate is a new kind of medicine for hypertensive disease. This article mainly studies the conditions of quantitatively measuring amlodipine maleate of tablet. The double-wave, 365 nm and 425 nm, spectrophotometry was used for determining the content of the amlodipine maleate tablet to eliminate interference of excipient. The absorbance is well linear with concentration between 5.0 μg/ml and 50.0 μg/ml, and the linear equation of differential spectrophotometry is △A=0.01149C+0.003 (r=0.9994), the coefficient of recovery is 99.92%, and RSD is 0.67%.
2008, 37(3): 466-469.
Abstract:
Identification and classification technology plays an important part in study of the brain-computer interface (BCI) system. In this paper, an algorithm is presented to deals with the complex brain signals and extract features and classify single-trial electroencephalogram (EEG). The algorithm combines independent component analysis algorithm and common spatial subspace decomposition with support vector machine to extract features from multi-channel EEG and electro cortico gram (ECoG). This algorithm was applied to the results of data analysis show that the proposed method can classify with high accuracy.
Identification and classification technology plays an important part in study of the brain-computer interface (BCI) system. In this paper, an algorithm is presented to deals with the complex brain signals and extract features and classify single-trial electroencephalogram (EEG). The algorithm combines independent component analysis algorithm and common spatial subspace decomposition with support vector machine to extract features from multi-channel EEG and electro cortico gram (ECoG). This algorithm was applied to the results of data analysis show that the proposed method can classify with high accuracy.
2008, 37(3): 470-473.
Abstract:
After discussing the design and applications of different periods of radiotherapy equipment collimator, a variable field collimator is proposed by use of mechatronics design and principles of robot technology. The characteristics and principle of this equipment is explained in detail. The equipment room is increased and the treatment of specific tumor place is improved.
After discussing the design and applications of different periods of radiotherapy equipment collimator, a variable field collimator is proposed by use of mechatronics design and principles of robot technology. The characteristics and principle of this equipment is explained in detail. The equipment room is increased and the treatment of specific tumor place is improved.
2008, 37(3): 474-477.
Abstract:
Reverse engineering is the process of extracting the solid features from the measured point data of the existing parts. The feature extraction based on point cloud is one of the key techniques in reverse engineering. A novel algorithm is proposed for feature recognition of revolving surface. The ant colony algorithm (ACA) is applied in reverse engineering for data processing. Firstly,the mathematic model is established which is suitable for extraction of feature parameter using ACA, and then a parameter optimization using ACA is processed. Finally the feature parameter is extracted and the surface is reconstructed. The new method is proved to be effective and flexible by experiments. The accuracy and efficiency to extract the parameters of revolving surface are improved and this method is suitable for the revolving surface in discretionary 3D-space.
Reverse engineering is the process of extracting the solid features from the measured point data of the existing parts. The feature extraction based on point cloud is one of the key techniques in reverse engineering. A novel algorithm is proposed for feature recognition of revolving surface. The ant colony algorithm (ACA) is applied in reverse engineering for data processing. Firstly,the mathematic model is established which is suitable for extraction of feature parameter using ACA, and then a parameter optimization using ACA is processed. Finally the feature parameter is extracted and the surface is reconstructed. The new method is proved to be effective and flexible by experiments. The accuracy and efficiency to extract the parameters of revolving surface are improved and this method is suitable for the revolving surface in discretionary 3D-space.
2008, 37(3): 478-480.
Abstract:
The vibratory characteristic of the chip size package (CSP) is difficult to be abstracted to an accurate academic model because of its complexity, and because the classic resonance rules can not take the fuzziness of resonant region into account, the results of vibration reliability analysis are inaccurate for actual demands possibly. finite element method (FEM) is used to build up the vibration analysis model and analyze. Furthermore, base on the analysis of FEM, an academic fuzzy reliability analysis model of vibration is built up with the help of fuzzy theory. In the end, a calculating example of fuzzy reliability analysis of vibration testifies the proposed method and principle are effective.
The vibratory characteristic of the chip size package (CSP) is difficult to be abstracted to an accurate academic model because of its complexity, and because the classic resonance rules can not take the fuzziness of resonant region into account, the results of vibration reliability analysis are inaccurate for actual demands possibly. finite element method (FEM) is used to build up the vibration analysis model and analyze. Furthermore, base on the analysis of FEM, an academic fuzzy reliability analysis model of vibration is built up with the help of fuzzy theory. In the end, a calculating example of fuzzy reliability analysis of vibration testifies the proposed method and principle are effective.
