ISSN 
2010 Vol. 39, No. 4
2010, 39(4): 481-485.
doi: 10.3969/j.issn.1001-0548.2010.04.001
Abstract:
In this paper, an improved algorithm is proposed for the single-carrier transport mode channel in digital television terrestrial multimedia broadcasting (DTMB) Standard. Based on the research to the DTMB single-carrier transport mode frame structure and the process of receiving-processing system, the shortage in the current algorithms for the channel estimation on the PN sequence moving correlation is indicated. According to the results of simulation, it is shown that the improved algorithm is better than the common one when the signal to noise ratio (SNR) is greater 20 dB.
In this paper, an improved algorithm is proposed for the single-carrier transport mode channel in digital television terrestrial multimedia broadcasting (DTMB) Standard. Based on the research to the DTMB single-carrier transport mode frame structure and the process of receiving-processing system, the shortage in the current algorithms for the channel estimation on the PN sequence moving correlation is indicated. According to the results of simulation, it is shown that the improved algorithm is better than the common one when the signal to noise ratio (SNR) is greater 20 dB.
2010, 39(4): 486-489.
doi: 10.3969/j.issn.1001-0548.2010.04.002
Abstract:
Enhanced techniques to declare Mode S preamble pulses in high Mode A/C fruits environment are discussed in this paper. Basis and roles to detected preamble are analyzed first. The improved preamble detection algorithm includes three steps: preamble detection, preamble validation, and reference level generation. Leading edge detection method and pulse matching method are employed to acquire pulse positions, then detect preamble by position matching. The PPM encoding used in the data block is difficult to generate with Mode A/C fruit replies. Counting the sample amplitudes within 2 dB in four sub-pulses, the reference level is the most amplitude. At last, efficiency of algorithms is verified by simulation results.
Enhanced techniques to declare Mode S preamble pulses in high Mode A/C fruits environment are discussed in this paper. Basis and roles to detected preamble are analyzed first. The improved preamble detection algorithm includes three steps: preamble detection, preamble validation, and reference level generation. Leading edge detection method and pulse matching method are employed to acquire pulse positions, then detect preamble by position matching. The PPM encoding used in the data block is difficult to generate with Mode A/C fruit replies. Counting the sample amplitudes within 2 dB in four sub-pulses, the reference level is the most amplitude. At last, efficiency of algorithms is verified by simulation results.
2010, 39(4): 490-494.
doi: 10.3969/j.issn.1001-0548.2010.04.003
Abstract:
In view of the deficiency of the performance of fixed threshold acquisition for PN code in spread spectrum communication, a new adaptive threshold acquisition scheme is proposed by combining the median filtering with mathematical morphology in image processing. Based on the analysis of the statistical property of the decision variable, the estimator consisting of sequence conversion circuit and morphological filter is used to estimate the background noise real-timely to get adaptive threshold for acquisition decision. The Monte Carlo simulation result shows that the adaptive threshold acquisition scheme in the paper can adapt to the multi-path environment well. Its performance of anti-jamming is good and it has high practicability.
In view of the deficiency of the performance of fixed threshold acquisition for PN code in spread spectrum communication, a new adaptive threshold acquisition scheme is proposed by combining the median filtering with mathematical morphology in image processing. Based on the analysis of the statistical property of the decision variable, the estimator consisting of sequence conversion circuit and morphological filter is used to estimate the background noise real-timely to get adaptive threshold for acquisition decision. The Monte Carlo simulation result shows that the adaptive threshold acquisition scheme in the paper can adapt to the multi-path environment well. Its performance of anti-jamming is good and it has high practicability.
2010, 39(4): 495-500.
doi: 10.3969/j.issn.1001-0548.2010.04.004
Abstract:
An efficient iterative method is presented for fast analysis of cylindrically conformal microstrip structure. Based on the transmission line modeling (TLM) method and the fast mode transform (FMT) theory, this method accelerates the process of the calculation by introducing the concept of the transverse electromagnetic waves instead of the transverse fields considered in the traditional algorithm. In the cylindrically stratified media, the transverse electromagnetic waves are represented by mixed modal basis functions. Ultimately, the material form of the modal admittance and the spectral reflection operator are deduced. The surface electric field and electric current of the cylindrically conformal microstrip antenna fed by means of a microstripline are calculated via wave concept iterative process. On this basis, the input impedance of the antenna can also be obtained. The results gained by utilizing WCIP are compared with those from published references to demonstrate the accuracy or efficiency of the method.
An efficient iterative method is presented for fast analysis of cylindrically conformal microstrip structure. Based on the transmission line modeling (TLM) method and the fast mode transform (FMT) theory, this method accelerates the process of the calculation by introducing the concept of the transverse electromagnetic waves instead of the transverse fields considered in the traditional algorithm. In the cylindrically stratified media, the transverse electromagnetic waves are represented by mixed modal basis functions. Ultimately, the material form of the modal admittance and the spectral reflection operator are deduced. The surface electric field and electric current of the cylindrically conformal microstrip antenna fed by means of a microstripline are calculated via wave concept iterative process. On this basis, the input impedance of the antenna can also be obtained. The results gained by utilizing WCIP are compared with those from published references to demonstrate the accuracy or efficiency of the method.
2010, 39(4): 501-504,522.
doi: 10.3969/j.issn.1001-0548.2010.04.005
Abstract:
A simplified hierarchical equalizer's extrinsic information of base-layer for 4-QAM multi-layer modulation is presented. A new hierarchical equalization method of base layer is applied to multi-layer modulation. Simulation results show that the proposed hierarchical equalization method works effectively for multi-layer modulations and the simplified equalizer's extrinsic information algorithm is able to reduce the calculation complexity degrees of equalizer's extrinsic information without the loss of bit error rate (BER) performance.
A simplified hierarchical equalizer's extrinsic information of base-layer for 4-QAM multi-layer modulation is presented. A new hierarchical equalization method of base layer is applied to multi-layer modulation. Simulation results show that the proposed hierarchical equalization method works effectively for multi-layer modulations and the simplified equalizer's extrinsic information algorithm is able to reduce the calculation complexity degrees of equalizer's extrinsic information without the loss of bit error rate (BER) performance.
2010, 39(4): 505-508.
doi: 10.3969/j.issn.1001-0548.2010.04.006
Abstract:
The characteristics of electromagnetic wave propagating in a multi-layer structure with anisotropic conductor-dielectric-plasma are researched. The dispersion curve is obtained by theoretical analysis and numerical calculation. The coupling effect of the anisotropic conductor sheet on electromagnetic wave is proved through comparing dispersion curves under various conditions. The results show that the slow plasma surface wave is formed because of the coupling of slow wave with plasma surface wave.
The characteristics of electromagnetic wave propagating in a multi-layer structure with anisotropic conductor-dielectric-plasma are researched. The dispersion curve is obtained by theoretical analysis and numerical calculation. The coupling effect of the anisotropic conductor sheet on electromagnetic wave is proved through comparing dispersion curves under various conditions. The results show that the slow plasma surface wave is formed because of the coupling of slow wave with plasma surface wave.
2010, 39(4): 509-512.
doi: 10.3969/j.issn.1001-0548.2010.04.007
Abstract:
Multiple accumulated-crossover parallel concatenated SPC (M-ACPC-SPC) codes is a class of novel error-correcting codes with low encoding/decoding complexity and good bit-error-rate (BER) performance. The average input-redundancy weight enumerating function (IRWEF) of M-ACPC-SPC codes is deduced to evaluate an upper BER bound of M-ACPC-SPC codes. An approximate formula of BER at high SNR is proposed for analyzing M-ACPC-SPC codes. Analysis show that the error floors of M-ACPC-SPC codes decrease as the growth of interleaver length and the number of interleavers.
Multiple accumulated-crossover parallel concatenated SPC (M-ACPC-SPC) codes is a class of novel error-correcting codes with low encoding/decoding complexity and good bit-error-rate (BER) performance. The average input-redundancy weight enumerating function (IRWEF) of M-ACPC-SPC codes is deduced to evaluate an upper BER bound of M-ACPC-SPC codes. An approximate formula of BER at high SNR is proposed for analyzing M-ACPC-SPC codes. Analysis show that the error floors of M-ACPC-SPC codes decrease as the growth of interleaver length and the number of interleavers.
2010, 39(4): 513-516.
doi: 10.3969/j.issn.1001-0548.2010.04.008
Abstract:
In vertical Bell labs layered space-time (V-BLAST) orthogonal frequency division multiplexing (OFDM) systems with distributed transmit antennas, since the carrier frequency offsets (CFOs) between the receiver and each transmit antenna are possibly different, the effects of multiple CFOs should be taken into account in detection. This paper first proposes a low-complexity CFO correction method for low delay spread channels by exploiting the underlying characteristics of zero-forcing (ZF) detection; and then proposes a ZF based detection method involving two CFO correction processes by combining the proposed CFO correction method with the conventional one. Simulation results show that the proposed CFO correction method can effectively eliminate the effects of multiple CFOs in low delay spread channels; while in channels with larger delay spread the proposed detection method involving two CFO correction processes can further improve the system performance.
In vertical Bell labs layered space-time (V-BLAST) orthogonal frequency division multiplexing (OFDM) systems with distributed transmit antennas, since the carrier frequency offsets (CFOs) between the receiver and each transmit antenna are possibly different, the effects of multiple CFOs should be taken into account in detection. This paper first proposes a low-complexity CFO correction method for low delay spread channels by exploiting the underlying characteristics of zero-forcing (ZF) detection; and then proposes a ZF based detection method involving two CFO correction processes by combining the proposed CFO correction method with the conventional one. Simulation results show that the proposed CFO correction method can effectively eliminate the effects of multiple CFOs in low delay spread channels; while in channels with larger delay spread the proposed detection method involving two CFO correction processes can further improve the system performance.
2010, 39(4): 517-522.
doi: 10.3969/j.issn.1001-0548.2010.04.009
Abstract:
The operations with large bit-width in residue to binary (R/B) conversion impairs the parallelism degree of residue number system (RNS). In this paper an scaling based R/B conversion algorithm and an RNS power of two scaling method are proposed. The analysis results show that the operation bit-width in the proposed R/B conversion is smaller than the maximum bit-width of radix in moduli set. Furthermore, the conversion results can be mapped into Tow's complement system (TCS) directly with arbitrary moduli set. As a result, the proposed R/B conversion algorithm can reduce the critical path in very large scale Integration (VLSI) circuits and improve the performance of VLSI.
The operations with large bit-width in residue to binary (R/B) conversion impairs the parallelism degree of residue number system (RNS). In this paper an scaling based R/B conversion algorithm and an RNS power of two scaling method are proposed. The analysis results show that the operation bit-width in the proposed R/B conversion is smaller than the maximum bit-width of radix in moduli set. Furthermore, the conversion results can be mapped into Tow's complement system (TCS) directly with arbitrary moduli set. As a result, the proposed R/B conversion algorithm can reduce the critical path in very large scale Integration (VLSI) circuits and improve the performance of VLSI.
2010, 39(4): 523-527,555.
doi: 10.3969/j.issn.1001-0548.2010.04.010
Abstract:
To the issue of hyper-parameter selection for radial basis function (RBF) based support vector machines (SVM), a new algorithm named as pseudo gradient and dynamic step optimization is proposed. Based on the characteristics of RBF, the kernel parameter is pre-estimated according to the distribution of the train set and the logarithmic scale is employed for the parameter space. The search direction is estimated with the changing of classification accuracy and by tuning the search step accordingly. At last, comparative experiments with Grid approach and PSO algorithm indicate the validity of the proposed algorithm.
To the issue of hyper-parameter selection for radial basis function (RBF) based support vector machines (SVM), a new algorithm named as pseudo gradient and dynamic step optimization is proposed. Based on the characteristics of RBF, the kernel parameter is pre-estimated according to the distribution of the train set and the logarithmic scale is employed for the parameter space. The search direction is estimated with the changing of classification accuracy and by tuning the search step accordingly. At last, comparative experiments with Grid approach and PSO algorithm indicate the validity of the proposed algorithm.
2010, 39(4): 528-531,536.
doi: 10.3969/j.issn.1001-0548.2010.04.011
Abstract:
A hardware semaphore module is designed to support the synchronization primitives, such as mutex and barrier. Compared with the atomic instruction realization, the method executes efficiently and uses fewer instructions. Based on the structure of scratch-pad memory, a shared program memory with two addressing mode of absolute address mapping and virtual address mapping is designed to implement instruction space sharing, resulting in higher utility of memory. The result of FPGA simulation demonstrates that, the performance of the proposed design can achieve speed-up 14.7% compared with traditional shared L2 caches.
A hardware semaphore module is designed to support the synchronization primitives, such as mutex and barrier. Compared with the atomic instruction realization, the method executes efficiently and uses fewer instructions. Based on the structure of scratch-pad memory, a shared program memory with two addressing mode of absolute address mapping and virtual address mapping is designed to implement instruction space sharing, resulting in higher utility of memory. The result of FPGA simulation demonstrates that, the performance of the proposed design can achieve speed-up 14.7% compared with traditional shared L2 caches.
2010, 39(4): 532-536.
doi: 10.3969/j.issn.1001-0548.2010.04.012
Abstract:
The design of multi-radio access selection simply according to the number of accessed users and the system capacity(MRAS) is not accurate for the wireless packet networks. A novel multi-radio access selection algorithm in heterogeneous wireless packet networks is proposed, in which the effect of link adaptive technology (including MAC retransmission and adaptive modulation) is considered together with the requirement of quality of packet service, in order to evaluate the resource requirement of packet service and network load status. The dynamic simulation is implemented to evaluate the performance of the proposed algorithm compared with traditional minimum accessed user and minimum path loss MRAS schemes,. The results reveal that the proposed MRAS algorithm performs better than those schemes in terms of QoS guarantee and load balancing.
The design of multi-radio access selection simply according to the number of accessed users and the system capacity(MRAS) is not accurate for the wireless packet networks. A novel multi-radio access selection algorithm in heterogeneous wireless packet networks is proposed, in which the effect of link adaptive technology (including MAC retransmission and adaptive modulation) is considered together with the requirement of quality of packet service, in order to evaluate the resource requirement of packet service and network load status. The dynamic simulation is implemented to evaluate the performance of the proposed algorithm compared with traditional minimum accessed user and minimum path loss MRAS schemes,. The results reveal that the proposed MRAS algorithm performs better than those schemes in terms of QoS guarantee and load balancing.
2010, 39(4): 537-541,555.
doi: 10.3969/j.issn.1001-0548.2010.04.013
Abstract:
In order to improve spectrum efficiency of communication system, a novel time-frequency overlapped hybrid division multiplexing system was researched. A rapid detection algorithm based on Gabor transform and an improved detection algorithm using error back propagation method was proposed. The simulation results show that the proposed rapid detection algorithm obtains significant increase in detection speed at the expense of some performance compared with maximum likelihood sequence estimation algorithm, and that the improved detection algorithm is a good compromise between system performance and detection speed and its performance is still better than the high level modulation with the same spectrum efficiency at a high signal to noise ratio. This shows that improving the transmission data rate with overlapped signals can achieve greater gains than using high-level QAM modulation with the same spectrum efficiency.
In order to improve spectrum efficiency of communication system, a novel time-frequency overlapped hybrid division multiplexing system was researched. A rapid detection algorithm based on Gabor transform and an improved detection algorithm using error back propagation method was proposed. The simulation results show that the proposed rapid detection algorithm obtains significant increase in detection speed at the expense of some performance compared with maximum likelihood sequence estimation algorithm, and that the improved detection algorithm is a good compromise between system performance and detection speed and its performance is still better than the high level modulation with the same spectrum efficiency at a high signal to noise ratio. This shows that improving the transmission data rate with overlapped signals can achieve greater gains than using high-level QAM modulation with the same spectrum efficiency.
2010, 39(4): 542-545,569.
doi: 10.3969/j.issn.1001-0548.2010.04.014
Abstract:
For the problem of multisensor-multitarget tracking in nonlinear system, a novel centralized multisensor unscented filter algorithm based on S-D assignment, SD-CMSUKF, is proposed. In the new algorithm, the association of measurements from each sensor to targets is first implemented according to the generalized S-D assignment technique and the optimal partition can be achieved. Then in the optimal partition, the measurements from the same target are dealt with sequentially in terms of the principle of sequential multisensor joint probabilistic data association algorithm (MSJPDA). Based on these, UKF is used for the propagation of state distribution in nonlinear system and the SD-CMSUKF algorithm is derived. Compared with the MSJPDA/EKF, the accuracy and robustness of the proposed algorithm are improved. Simulation results show the superiority of the new algorithm.
For the problem of multisensor-multitarget tracking in nonlinear system, a novel centralized multisensor unscented filter algorithm based on S-D assignment, SD-CMSUKF, is proposed. In the new algorithm, the association of measurements from each sensor to targets is first implemented according to the generalized S-D assignment technique and the optimal partition can be achieved. Then in the optimal partition, the measurements from the same target are dealt with sequentially in terms of the principle of sequential multisensor joint probabilistic data association algorithm (MSJPDA). Based on these, UKF is used for the propagation of state distribution in nonlinear system and the SD-CMSUKF algorithm is derived. Compared with the MSJPDA/EKF, the accuracy and robustness of the proposed algorithm are improved. Simulation results show the superiority of the new algorithm.
2010, 39(4): 546-550.
doi: 10.3969/j.issn.1001-0548.2010.04.015
Abstract:
In order to reduce the scale invariant feature transform (SIFT) algorithm's complexity, improve the real-time performance of the algorithm and ensure that the feature points are corners, a new Harris-SIFT algorithm is proposed. The feature points of images are detected by using Harris operator, the main orientation for each feature point is calculated, and lastly, the feature point descriptors are generated after rotating the coordinates of the descriptors relative to the feature points' main orientations. Experimental results of image matching in binocular stereo vision demonstrate the effectiveness of the proposed algorithm.
In order to reduce the scale invariant feature transform (SIFT) algorithm's complexity, improve the real-time performance of the algorithm and ensure that the feature points are corners, a new Harris-SIFT algorithm is proposed. The feature points of images are detected by using Harris operator, the main orientation for each feature point is calculated, and lastly, the feature point descriptors are generated after rotating the coordinates of the descriptors relative to the feature points' main orientations. Experimental results of image matching in binocular stereo vision demonstrate the effectiveness of the proposed algorithm.
2010, 39(4): 551-555.
doi: 10.3969/j.issn.1001-0548.2010.04.016
Abstract:
To resolve the problem that the switch frequency of sliding mode control (SMC) switching power converter with hysteresis modulation method changes with the variation of the input voltage or load, this paper presents a fixed-frequency modulation method that can directly convert a switching function to a fixed-frequency switching control signal. The operation principle of the modulation method for a SMC buck converter is described, and its mixed implementation circuits was given. Simulation results show that the modulation technique reserves the advantage of a hysteresis modulation's outstanding transient characteristics, and possesses a constant switching frequency. This will help the integration and digital implementation of sliding mode controller for switching DC-DC converter.
To resolve the problem that the switch frequency of sliding mode control (SMC) switching power converter with hysteresis modulation method changes with the variation of the input voltage or load, this paper presents a fixed-frequency modulation method that can directly convert a switching function to a fixed-frequency switching control signal. The operation principle of the modulation method for a SMC buck converter is described, and its mixed implementation circuits was given. Simulation results show that the modulation technique reserves the advantage of a hysteresis modulation's outstanding transient characteristics, and possesses a constant switching frequency. This will help the integration and digital implementation of sliding mode controller for switching DC-DC converter.
2010, 39(4): 556-559.
doi: 10.3969/j.issn.1001-0548.2010.04.017
Abstract:
The precision time protocol (PTP) improves the clock synchronization accuracy greatly and makes sensors, actuators and other terminals share unique time reference, which assures clock synchronization quality of different terminals. This paper puts forward a typical network topology in wireless distributed measurement system, and introduces the work process of PTP. The improvement of PTP clock synchronization adjust algorithm is analyzed. The clock synchronization accuracy of tree network topology is presented through simulation in MATLAB. The PTP clock synchronization offset can be reduced significantly with the implementation of drift estimation and skew compensation in tree network topology.
The precision time protocol (PTP) improves the clock synchronization accuracy greatly and makes sensors, actuators and other terminals share unique time reference, which assures clock synchronization quality of different terminals. This paper puts forward a typical network topology in wireless distributed measurement system, and introduces the work process of PTP. The improvement of PTP clock synchronization adjust algorithm is analyzed. The clock synchronization accuracy of tree network topology is presented through simulation in MATLAB. The PTP clock synchronization offset can be reduced significantly with the implementation of drift estimation and skew compensation in tree network topology.
2010, 39(4): 560-563.
doi: 10.3969/j.issn.1001-0548.2010.04.018
Abstract:
In order to reduce tasks execution time and the route, a changeable path planning and multi-task assignment optimization design method is introduced in this paper. Tasks finishing time of unmanned aerial vehicles (UAVs) cluster is reduced by tasks balanced distribution to each UAV and flying route is shortened by adjacent tasks distribution to same UAV. The result proves that compared with route priority algorithm or task priority algorithms, The tasks finishing time of UAVs cluster of the proposed method is decreased 18% and fuel consumption is reduced obviously.
In order to reduce tasks execution time and the route, a changeable path planning and multi-task assignment optimization design method is introduced in this paper. Tasks finishing time of unmanned aerial vehicles (UAVs) cluster is reduced by tasks balanced distribution to each UAV and flying route is shortened by adjacent tasks distribution to same UAV. The result proves that compared with route priority algorithm or task priority algorithms, The tasks finishing time of UAVs cluster of the proposed method is decreased 18% and fuel consumption is reduced obviously.
2010, 39(4): 564-569.
doi: 10.3969/j.issn.1001-0548.2010.04.019
Abstract:
The application of un-continue double BOOST DC/DC inverter maximum power point tracking control of the photovoltaic generate system is discussed in detail in this paper. Interleave BOOST circuit is capable of absorbing and reduce the output wave. Then sliding model control technology used in the system can track the max power of the uncertainly photovoltaic generate system adaptively and real-time go into sliding surface，consequently obtain the maximum power. The whole system is able to improve the performance of robust control in the case of input/output parameter perturbation. The simulation and the experiments show that the sliding-model control technology is capable of reducing the ripples current of the load of in the double BOOST DC/DC interleave convener and improving the efficiency.
The application of un-continue double BOOST DC/DC inverter maximum power point tracking control of the photovoltaic generate system is discussed in detail in this paper. Interleave BOOST circuit is capable of absorbing and reduce the output wave. Then sliding model control technology used in the system can track the max power of the uncertainly photovoltaic generate system adaptively and real-time go into sliding surface，consequently obtain the maximum power. The whole system is able to improve the performance of robust control in the case of input/output parameter perturbation. The simulation and the experiments show that the sliding-model control technology is capable of reducing the ripples current of the load of in the double BOOST DC/DC interleave convener and improving the efficiency.
2010, 39(4): 570-573,633.
doi: 10.3969/j.issn.1001-0548.2010.04.020
Abstract:
Time-frequency signal analysis is a hot research topic in signal processing domain at present. A number of time-frequency distributions have been developed and used to analyze time-frequency signal. The linear canonical transform with multi-parameter is a powerful time-frequency analysis tool. It is the generalization of the Fourier transform and the fractional Fourier transform. In this paper, the relations between the linear canonical transform and time-frequency distributions are obtained. Based on these relations, a novel method for time-frequency signal separation is proposed. This method is very effective to separate components from a time-frequency signal, whose components interact in the time and the frequency domains and does not overlapped with each other in the time-frequency plane.The simulation results illustrate the validity and practicability of the proposed method.
Time-frequency signal analysis is a hot research topic in signal processing domain at present. A number of time-frequency distributions have been developed and used to analyze time-frequency signal. The linear canonical transform with multi-parameter is a powerful time-frequency analysis tool. It is the generalization of the Fourier transform and the fractional Fourier transform. In this paper, the relations between the linear canonical transform and time-frequency distributions are obtained. Based on these relations, a novel method for time-frequency signal separation is proposed. This method is very effective to separate components from a time-frequency signal, whose components interact in the time and the frequency domains and does not overlapped with each other in the time-frequency plane.The simulation results illustrate the validity and practicability of the proposed method.
2010, 39(4): 574-577.
doi: 10.3969/j.issn.1001-0548.2010.04.021
Abstract:
The intensive absorption and scattering caused by seawater extremely affect the operating range and the detecting capability of underwater laser imaging technology. The absorption effect and the scattering effect of light in the seawater are analyzed. By using semi-analytical Monte Carlo algorithm, the process of how the blue-green laser transmits in the seawater is simulated. And the rules of how the photon number of the forward scatter light spot changes with the parameters, such as the average cosine of the scattered angles, the attenuation coefficient, the seawater single-scattering albedo and distance, are obtained. When the transmit distance increases, the photon amount of the forward scatter light spot will increase and tend to stable after reaching a certain distance. The photon amount has an analogous exponential downtrend when the transmit distance increases. At the same transmit distance but with different water quality parameters, the photon amount has big differences.
The intensive absorption and scattering caused by seawater extremely affect the operating range and the detecting capability of underwater laser imaging technology. The absorption effect and the scattering effect of light in the seawater are analyzed. By using semi-analytical Monte Carlo algorithm, the process of how the blue-green laser transmits in the seawater is simulated. And the rules of how the photon number of the forward scatter light spot changes with the parameters, such as the average cosine of the scattered angles, the attenuation coefficient, the seawater single-scattering albedo and distance, are obtained. When the transmit distance increases, the photon amount of the forward scatter light spot will increase and tend to stable after reaching a certain distance. The photon amount has an analogous exponential downtrend when the transmit distance increases. At the same transmit distance but with different water quality parameters, the photon amount has big differences.
2010, 39(4): 578-580,633.
doi: 10.3969/j.issn.1001-0548.2010.04.022
Abstract:
This paper introduces the miniature soft X-ray detector for detecting the subnanosecond X-ray pulse. Its response time is analyzed and calculated in theory. According to the results of the theoretical analysis, the HFSS based on the finite element theory is used to model and simulate the X-ray diode and the transmission line theory is applied to design the ultra-broad band coaxial line also. The high dielectric strength film is chosen to fabricate the big storage capacitance and therefore to solve the problem that it is difficult to fabricate big storage capacitance and high voltage resistance at the same time. The characteristic of the detector is experimentally examined on the archetype of “Shenguang Ⅲ Laser Facility” and the response time is about 51ps. also, Some different physics aspects that need to be considered when designing such fast response detectors are discussed.
This paper introduces the miniature soft X-ray detector for detecting the subnanosecond X-ray pulse. Its response time is analyzed and calculated in theory. According to the results of the theoretical analysis, the HFSS based on the finite element theory is used to model and simulate the X-ray diode and the transmission line theory is applied to design the ultra-broad band coaxial line also. The high dielectric strength film is chosen to fabricate the big storage capacitance and therefore to solve the problem that it is difficult to fabricate big storage capacitance and high voltage resistance at the same time. The characteristic of the detector is experimentally examined on the archetype of “Shenguang Ⅲ Laser Facility” and the response time is about 51ps. also, Some different physics aspects that need to be considered when designing such fast response detectors are discussed.
2010, 39(4): 581-584,622.
doi: 10.3969/j.issn.1001-0548.2010.04.023
Abstract:
A method of obtaining the surface form deviation of the plane optical element by using BP neural network is presented. The curvatures of the interference fringes and the values of the fringe spacing of tested zones in the interferogram are determined, and the BP neural network is trained to obtain the value of light ring of the plane optical element. It is found that the test results obtained by Zygo interferometer are consistent with the test results obtained by the proposed method. Experimental results show that the method can enhance the adaptation capability of processing the interferograms and improve the measuring precision of the plane optical element
A method of obtaining the surface form deviation of the plane optical element by using BP neural network is presented. The curvatures of the interference fringes and the values of the fringe spacing of tested zones in the interferogram are determined, and the BP neural network is trained to obtain the value of light ring of the plane optical element. It is found that the test results obtained by Zygo interferometer are consistent with the test results obtained by the proposed method. Experimental results show that the method can enhance the adaptation capability of processing the interferograms and improve the measuring precision of the plane optical element
2010, 39(4): 585-588.
doi: 10.3969/j.issn.1001-0548.2010.04.024
Abstract:
Real-time garbage collection should collect unused memory and guarantee real-time tasks to meet their deadlines. Furthermore, system memory requirement should be considered. A hybrid garbage collection is proposed in this paper. Reference counting algorithm is used to collect acyclic garbage and timestamp algorithm is used to collect cyclic garbage. GC and real-time tasks are scheduled concurrently. The proposed GC not only collects all unused memory but also reduces memory requirement compared with hybrid GC based on mark-sweep algorithm. It fits for large-scale system.
Real-time garbage collection should collect unused memory and guarantee real-time tasks to meet their deadlines. Furthermore, system memory requirement should be considered. A hybrid garbage collection is proposed in this paper. Reference counting algorithm is used to collect acyclic garbage and timestamp algorithm is used to collect cyclic garbage. GC and real-time tasks are scheduled concurrently. The proposed GC not only collects all unused memory but also reduces memory requirement compared with hybrid GC based on mark-sweep algorithm. It fits for large-scale system.
2010, 39(4): 589-592.
doi: 10.3969/j.issn.1001-0548.2010.04.025
Abstract:
An annular architecture for the intrusion-tolerance system is presented. The data consistency algorithm and control algorithm for servers are described in detail. This system guarantees the data consistency when the total of servers online is more than twice the number of malicious servers, and the performance of intrusion-tolerance can be improved by adjusting the number of servers online dynamically. The system availability is illustrated in the simulation experiments and a time zone of higher availability is also presented.
An annular architecture for the intrusion-tolerance system is presented. The data consistency algorithm and control algorithm for servers are described in detail. This system guarantees the data consistency when the total of servers online is more than twice the number of malicious servers, and the performance of intrusion-tolerance can be improved by adjusting the number of servers online dynamically. The system availability is illustrated in the simulation experiments and a time zone of higher availability is also presented.
2010, 39(4): 593-597.
doi: 10.3969/j.issn.1001-0548.2010.04.026
Abstract:
A new approach is presented for blog post summarization based on ranking smooth support vector machine (Rank-sSVM). The use of ranking algorithm for this task allows one to adapt summaries to the commenter needs and to the blog corpus characteristics. To use Rank-sSVM, firstly, key sentences are extracted manually from blog posts as training samples. Feature set representing post sentences, which consist of 14 features including tag, comment and other unique blog information, is generated by machine. After all the sentences are ranked by the ranking model, the most important ones in front are selected to summarize the post. The experimental results show that the proposed method has good performance on Chinese blog datasets.
A new approach is presented for blog post summarization based on ranking smooth support vector machine (Rank-sSVM). The use of ranking algorithm for this task allows one to adapt summaries to the commenter needs and to the blog corpus characteristics. To use Rank-sSVM, firstly, key sentences are extracted manually from blog posts as training samples. Feature set representing post sentences, which consist of 14 features including tag, comment and other unique blog information, is generated by machine. After all the sentences are ranked by the ranking model, the most important ones in front are selected to summarize the post. The experimental results show that the proposed method has good performance on Chinese blog datasets.
2010, 39(4): 598-602,622.
doi: 10.3969/j.issn.1001-0548.2010.04.027
Abstract:
On deep research on the workflow of non-repudiation and fair-exchange protocols in electronic commerce, it is proved that these protocols with trusted third party need to run in four steps at least. The analysis of an existing protocol shows that it needs to run in four steps, rather than just run in three steps it claims. On the principle that security protocol and cryptography system should be designed separately, a common model of convertible authenticated encryption schemes is proposed by analyzing some existing convertible authenticated encryption schemes. By using this model, a secure email protocol with semi-trusted third party is designed. Result shows that this protocol has non-repudiation features of both sender and receiver by formal analysis.
On deep research on the workflow of non-repudiation and fair-exchange protocols in electronic commerce, it is proved that these protocols with trusted third party need to run in four steps at least. The analysis of an existing protocol shows that it needs to run in four steps, rather than just run in three steps it claims. On the principle that security protocol and cryptography system should be designed separately, a common model of convertible authenticated encryption schemes is proposed by analyzing some existing convertible authenticated encryption schemes. By using this model, a secure email protocol with semi-trusted third party is designed. Result shows that this protocol has non-repudiation features of both sender and receiver by formal analysis.
2010, 39(4): 603-606.
doi: 10.3969/j.issn.1001-0548.2010.04.028
Abstract:
In order to solve the problem of dated routes and poor flexibility to variations in topology in Ad hoc routing protocols, a multipath routing algorithm based on stable topology and ant colony optimization (SAMR) is proposed. In SAMR, pheromones of a path are used to reflect the quality of the path, which are a function of two parameters: topology stability and end-to-end delay. Routes are dynamically updated and maintained to avoid being dated by ant colony optimization algorithm. Simulation results show that in dynamic conditions, SAMR can improve network throughput and reduce end-to-end delay.
In order to solve the problem of dated routes and poor flexibility to variations in topology in Ad hoc routing protocols, a multipath routing algorithm based on stable topology and ant colony optimization (SAMR) is proposed. In SAMR, pheromones of a path are used to reflect the quality of the path, which are a function of two parameters: topology stability and end-to-end delay. Routes are dynamically updated and maintained to avoid being dated by ant colony optimization algorithm. Simulation results show that in dynamic conditions, SAMR can improve network throughput and reduce end-to-end delay.
2010, 39(4): 607-611.
doi: 10.3969/j.issn.1001-0548.2010.04.029
Abstract:
A recursive bipartitioning algorithm, RPM, is proposed for low energy mapping in tree-based Network-on-Chip (NoC) architectures subject to communication latency constraints. The mapping problem is formulated to multi-level IP core communication task graph partitioning problems, and the modified Kernighan-Lin mincut heuristic is used to solve them. Experimental results show that RPM obtains lower energy mapping solutions compared with existing algorithms.
A recursive bipartitioning algorithm, RPM, is proposed for low energy mapping in tree-based Network-on-Chip (NoC) architectures subject to communication latency constraints. The mapping problem is formulated to multi-level IP core communication task graph partitioning problems, and the modified Kernighan-Lin mincut heuristic is used to solve them. Experimental results show that RPM obtains lower energy mapping solutions compared with existing algorithms.
2010, 39(4): 612-616.
doi: 10.3969/j.issn.1001-0548.2010.04.030
Abstract:
An approach based on maximum entropy model is proposed for event classification. This approach can classify the events by merging the features about trigger and context in event mention sentences. The key of the method is parameter estimation and feature selection, which are discussed in detail. IIS algorithm is employed for parameter estimation and incremental method is used for feature selection. Experiments are performed on management succession, meeting, terror attack, judicial adjudicate, and natural disaster in the People Daily corpus. The results show that the method can achieve much better performance than the traditional approach.
An approach based on maximum entropy model is proposed for event classification. This approach can classify the events by merging the features about trigger and context in event mention sentences. The key of the method is parameter estimation and feature selection, which are discussed in detail. IIS algorithm is employed for parameter estimation and incremental method is used for feature selection. Experiments are performed on management succession, meeting, terror attack, judicial adjudicate, and natural disaster in the People Daily corpus. The results show that the method can achieve much better performance than the traditional approach.
2010, 39(4): 617-622.
doi: 10.3969/j.issn.1001-0548.2010.04.031
Abstract:
The global asymptotical robust stability of neural networks with time-varying delays is investigated. Based on nonnegative matrix theory and Lyapunov-Razumikhin technique, a sufficient condition for global asymptotical robust stability is given, which is independent of time delays and can be verified easily. Theoretical analysis and numerical examples show that the obtained condition generalizes two corresponding results derived in the literatures, and complements the results concerning the robust stability research of neural networks effectively. A numerical example and the corresponding computer simulation are presented to verify the effectiveness of the obtained result.
The global asymptotical robust stability of neural networks with time-varying delays is investigated. Based on nonnegative matrix theory and Lyapunov-Razumikhin technique, a sufficient condition for global asymptotical robust stability is given, which is independent of time delays and can be verified easily. Theoretical analysis and numerical examples show that the obtained condition generalizes two corresponding results derived in the literatures, and complements the results concerning the robust stability research of neural networks effectively. A numerical example and the corresponding computer simulation are presented to verify the effectiveness of the obtained result.
2010, 39(4): 623-628.
doi: 10.3969/j.issn.1001-0548.2010.04.032
Abstract:
Aiming at crackle occurs of the drum brake during the braking process, the contact analysis model and transient thermal analysis model of the drum brake is established respectively based on the finite element method and the non-static equation of heat conduction. The magnitude and the distribution of mechanical stress as a result of the brake shoe's braking on the drum is analyzed by nonlinear-contact method. The magnitude and the distribution law of heat generation, heat dissipating and the thermal strees is given by the method of transient thermal analysis. The cracking reason of the brake drum of a certain heavy vehicle is analyzed. It show that either the mechanical stress or the thermal stress can influence the brake drum's cracking under the emergency braking condition, yet the influences of morphology of cracking in the dram are different. The conclusion is also validated by the practical cracking morphology of the brake drum, proving that this method has good value in the field of engineering application and significance of theoretical guiding.
Aiming at crackle occurs of the drum brake during the braking process, the contact analysis model and transient thermal analysis model of the drum brake is established respectively based on the finite element method and the non-static equation of heat conduction. The magnitude and the distribution of mechanical stress as a result of the brake shoe's braking on the drum is analyzed by nonlinear-contact method. The magnitude and the distribution law of heat generation, heat dissipating and the thermal strees is given by the method of transient thermal analysis. The cracking reason of the brake drum of a certain heavy vehicle is analyzed. It show that either the mechanical stress or the thermal stress can influence the brake drum's cracking under the emergency braking condition, yet the influences of morphology of cracking in the dram are different. The conclusion is also validated by the practical cracking morphology of the brake drum, proving that this method has good value in the field of engineering application and significance of theoretical guiding.
2010, 39(4): 629-633.
doi: 10.3969/j.issn.1001-0548.2010.04.033
Abstract:
To solve the problems such as the insufficiency of the required data and the low credibility in reliability prediction for diesel engine in engineering, this paper utilizes the property of fuzzy number which is suitable for quantifying fuzzy information and combines the fuzzy sets and the traditional similar product method by using fuzzy sets theory and interval analysis. Then it puts forward a new reliability prediction method which combines the fuzzy similar product method and the fuzzy comprehensive evaluation, which is then used to do the fuzzy prediction on the reliability of the diesel engine's air compressor. This method not only makes sufficient use of the reliability data of the old machine type, but also combines the experts' practical experiences and judgments. It realizes the mutual complement of the fixed information and the uncertain information. This method has the practical value in engineering.
To solve the problems such as the insufficiency of the required data and the low credibility in reliability prediction for diesel engine in engineering, this paper utilizes the property of fuzzy number which is suitable for quantifying fuzzy information and combines the fuzzy sets and the traditional similar product method by using fuzzy sets theory and interval analysis. Then it puts forward a new reliability prediction method which combines the fuzzy similar product method and the fuzzy comprehensive evaluation, which is then used to do the fuzzy prediction on the reliability of the diesel engine's air compressor. This method not only makes sufficient use of the reliability data of the old machine type, but also combines the experts' practical experiences and judgments. It realizes the mutual complement of the fixed information and the uncertain information. This method has the practical value in engineering.
2010, 39(4): 634-639.
doi: 10.3969/j.issn.1001-0548.2010.04.034
Abstract:
Multi-objective dynamic voltage/reactive power control is a complicated non-linear problem. Conventional pre-evaluated methods can get one solution only. A novel multi-objective dynamic reactive power optimization model is created in this paper and, for solving the model, a relevant improvement has been made in the non-dominated sorting genetic algorithm II (NSGA-II). This approach has been applied to the IEEE 14 nodes and 30 nodes systems and an actual system. The result shows that the approach has encouraging performance in dynamic reactive power optimization with objectives of minimizing reactive power loss, voltage deviation, and the number of operations as well.
Multi-objective dynamic voltage/reactive power control is a complicated non-linear problem. Conventional pre-evaluated methods can get one solution only. A novel multi-objective dynamic reactive power optimization model is created in this paper and, for solving the model, a relevant improvement has been made in the non-dominated sorting genetic algorithm II (NSGA-II). This approach has been applied to the IEEE 14 nodes and 30 nodes systems and an actual system. The result shows that the approach has encouraging performance in dynamic reactive power optimization with objectives of minimizing reactive power loss, voltage deviation, and the number of operations as well.
