最新刊期
卷 47 ， 期 6 ， 2013
- 摘要：Since the 0/1 space hopping technique in forward training mode has security problems after the leak of space hopping pattern, a backward training technique with weight-feedback is proposed. Through backward training between the transmitter and the target user, the target user can obtain the weights that are equivalent with those generated from the forward training, while the eavesdropper, even if she steals the space hopping pattern, cannot correctly demodulate because of the diversity of the wireless channel. It is this technique that is completely different from the traditional frequency hopping spread spectrum technique. The proposed technique aims at solving the secure problem of wireless communications fundamentally, makes full use of the abundant space-time spectrum resources of the wireless signals, and ensures secure transmission in physical layer. Simulation results show that even when both the space hopping pattern and the feedback weights are leaked, the eavesdropper keeps a high symbol error rate and cannot intercept information.关键词：wireless communications;physical layer security;multi-antenna;wireless channel;space hopping;space-time spectrum;frequency hopping spread spectrum2076|4|0更新时间：2025-05-01
- 摘要：A programming framework is proposed to address the problem that the context-oriented programming languages do not provide any mechanisms to support dynamic layer addition, and its implementation is presented. The key component of the framework is an extended Java virtual machine. It incorporates predicate for checking object composition and delegation to implement layer activation, and uses existing virtual machine services to support dynamic layer addition. Therefore,the framework provides the capabilities of layer activation and dynamic layer addition. Experimental results show that the performance of layer activation in the proposed framework is approximately 10% higher than that in ContextJ.关键词：Java virtual machine;object composition;delegation;dynamic behavior adjustment2030|4|1更新时间：2025-05-01
- 摘要：A novel Bayesian compressive sensing image reconstruction algorithm based on the context modeling is proposed to solve the problem that the intrascale dependencies of image's wavelet coefficients is not fully exploited by the compressive sensing reconstruction algorithm. It is assumed that the wavelet coefficients of image obey a spike-and-slab probability model. Context vectors in the current coefficient's neighborhood are obtained through a new context modeling method. Then, the significant probability of current coefficient is estimated according to the dependencies of the context vector with the current coefficient and the state of parent coefficient. Finally, the image's wavelet coefficients is recovered from the observation vector based on the significant probabilities of the image's wavelet coefficients by using a Bayesian inference via Markov chain Monte Carlo sampling, thus, the reconstruction image is generated. Since the spike-and-slab probability model with context modeling is adaptive to the spatial changes of the images, experimental results and comparisons with Bayesian tree-structured wavelet compressive sensing algorithm which only uses the interscale dependencies show that the proposed algorithm improves the peak-signal-to-noise-ratio nearly by 2 dB at the sampling rate of 0.9.关键词：context modeling;compressive sensing;image reconstruction;Bayesian inference1949|4|0更新时间：2025-05-01
- 摘要：A novel algorithm to estimate illumination parameter based on quotient image(QI)is proposed to improve the accuracy of facial image illumination synthesis. Analysis indicates that the hypothesis of uniform albedos in traditional QI algorithm can not be strictly hold, and that inherent error in illumination parameter estimation will be incurred. Then, an improved objective function is derived in the parametric illumination subspace framework, and the albedo ratios is replaced by the quotient image itself, so that the impacts of the hypothesis is weakened, and independent albedo per facial pixel can be permitted. An iterative algorithm is designed to solve the objective function through linear system, and illumination parameter can be estimated at high accuracy. Experiments on the oriental face database(OFD)and the AI&R face database show that the proposed algorithm has good convergence ability, and that the trace ratio for illumination estimation and the peak-signal-to-noise-ratio in illumination synthesis images are improved by 25.49～43.09 dB and 4.51～9.24 dB, respectively.关键词：facial image;illumination parameter;quotient image;illumination re-rendering1780|4|2更新时间：2025-05-01
- 摘要：An adaptive detection algorithm is proposed to solve on the problem in the application of the SAR images that the traditional target detection algorithms, which are on the basis of sliding window, cannot give an accurate detection to targets that are in short distances, near to the coast, or very different in size. The method separates the sea surface using threshold filtering, and then the targets to be detected are obtained by counting the pixel volume of targets and eliminating the most acreage of the land. Adaptive windows are set according to the pixel distribution. The K-distribution possibility model of the scenes near the targets is obtained by separating the counting of the target pixel from the counting of the background pixel on adaptive windows. The adaptive window detection algorithm has the advantages of achieving accurate statistics of background pixel of targets and K-distribution fitting over the traditional target detection algorithm. Experimental results show that the quality factor of the proposed adaptive window detection algorithm is 0.34 higher than that of the traditional target detection algorithm when the detecting is performed on the SAR images with the circumstances of the complicated sea surface and the same CFAR condition.关键词：synthetic aperture radar;ship target detection;constant false alarm;K-distribution2047|4|6更新时间：2025-05-01
- 摘要：A joint detection threshold and power allocation optimization(JDPO)based on underlay cognitive radio is proposed to improve spectrum utilization in narrowband satellite systems. The joint scheme maximizes throughput and focuses on uplink. A corresponding model is established using the operation relationship among detection error, power allocation and throughput. Then, the optimization problem is partioned into two sub-problems: optimization of detection threshold and optimization of power allocation. A windowed particle swarm optimization is proposed to solve the former sub-problem, and the Kuhn-Tucker condition is applied to find the solution of the latter one. An intermediate variable is introduced to repeatedly perform iteration between both the sub-solutions to get the joint-optimal solutions for the detection threshold and power allocation. Simulation results and comparisons with the traditional satellite communication show that the JDPO scheme gets about 50% throughput increasing.关键词：satellite cognitive radio;uplink;spectrum utilization;detection threshold;power allocation;joint optimization1957|4|6更新时间：2025-05-01
- 摘要：A packet-layer assessment model for video quality is proposed to realize real-time quality monitoring for networked video. The model utilizes only information provided by packet headers without resorting to any payload information. The information, including the bit-rate, the frame rate, the coded bits of each frame, the number of lost packets, and the positions of lost packets, is obtained or estimated by analyzing limited information from packet header. Then, the temporal complexity factor is estimated using the bit-rate and the average coded bits of I-frames. The estimated temporal complexity factor and the frame type are incorporated to evaluate the distortion due to compression first and the distortion due to packet loss afterwards, and the quality for networked video is then generated. Experimental results and comparisons with G.1070 and Enhanced G.1070 models show that the proposed model gets an increment of about 0.087 and 0.065 in PCC, and a decrement of about 0.219 and 0.164 in RMSE, respectively. The proposed model can be used to accurately estimate the networked video quality on account of its advanced performance.关键词：networked video;video quality assessment;coding distortion;distortion caused by packet loss1958|4|3更新时间：2025-05-01
- 摘要：A low cost attitude estimation(LCAE)algorithm assisted by the single baseline GPS is proposed to solve the problem that the inertial measurement unit with the micro electro mechanical system elements is not accurate enough to the broadband mobile satellite communication system. The attitude angles acquired by accelerometers are fused with the measurement of gyros by complementary filters. In order to remove the interference of maneuver acceleration, compensations to both the maneuver acceleration and the sideslip angle are added using the velocity and heading data of single baseline GPS. A switch is added to reduce the dependence level of LCAE algorithm on GPS. Experimental results show that the LCAE algorithm can drive out the non-gravitational components in the output of the accelerometers efficiently and isolate the interference of vehicle's motion. The proposed algorithm can satisfy the low cost mobile satcom with estimation accuracy of ±0.5° in attitude angles when GPS signal is locked all the while, and the estimation of attitude angles achieves an accuracy of ±1° and is better than the estimation accuracy of the switch alman filter algorithm when GPS signal is not locked all the while.1968|4|1更新时间：2025-05-01
- 摘要：Recently, multi-dimensional support vector regression(M-SVR)has been a promising tool in solving a wide range of multi-input and multi-output(MIMO)regression problems. However, when some output dimensions have more dependencies than others, M-SVR is are generally hard to obtain impressive performance due to the negative or redundant domain knowledge across all outputs. A structure of adaptive grouping is introduced into the M-SVR to solve the problem. It is assumed that model parameters of related output dimensions are similar to each other, then a new regularization-based M-SVR algorithm is presented by introducing a regularizer with grouping structure. The regularization problem is then converted into a mixed 0-1 programming problem. Alternating optimization is employed for learning related outputs jointly in the same group, and to obtain the optimal grouping structure and model parameters through adaptively identifying the grouping structure. The proposed algorithm is tested empirically on a toy problem as well as a real-life data set. The experimental results show that the performance of the proposed algorithm outperforms the performance of the classical M-SVR and the single-output SVM algorithm.关键词：support vector machine;adaptive grouping;mixed 0-1 programming1982|4|1更新时间：2025-05-01
- 摘要：A selection method for parameters of the rough fuzzy C-means clustering based on uncertainty measurement is proposed. The selection of parameter threshold is converted into an optimal partition problem, and partitions are evaluated based on variances. The information entropy is employed to measure the fuzziness of the sample membership to clusters, then an adaptive method to calculate weights is presented based on the roughness of clusters and the fuzziness of samples. The adaptive parameter selection method is employed in rough fuzzy C-meaning algorithm. Experiments and comparisons with some existing typical parameters selection methods for rough fuzzy C-means clustering algorithm are performed on synthetic and real-world data sets, and the results show that the proposed algorithm achieves higher accuracy, and is effective.关键词：clustering;rough fuzzy C-means;entropy;roughness1968|4|7更新时间：2025-05-01
- 摘要：A multi-channel multi-path cross-layer(MCMP-CL)protocol is proposed to meet the data reliability and real-time demands for industrial monitoring sensor networks. The MCMP-CL protocol achieves distributed network management by clustering. The self-designed high tolerance channel switching(HTCS)algorithm is used to evaluate the channel quality and to adaptively switch channels in real-time, and multi-channel with TDMA mechanism is implemented in intra-cluster communication to reduce packet loss that is caused by the adjacent clusters and adjacent frequency protocols' interference. A link Q value is introduced to evaluate route condition, and the multi-path mechanism based on the probability forwarding method is adopted in inter-cluster communication to balance the network streaming so that the packet loss that is caused by the congestion in a large or quickly changed data streaming is reduced. The protocol improves the network performance by combining the multi-channel mechanism in intra-cluster and the multi-path mechanism in inter-cluster. Simulation results and comparison with traditional clustered protocols show that the MCMP-CL can effectively resist interference, control and ease congestion, and reduce time delay in inter-clusterby about 22%.关键词：wireless sensor networks;clustered networks;multi-channel;cross-layer;reliability1876|4|2更新时间：2025-05-01
- 摘要：A low time complexity method for checking the correctness of ARM memory model is proposed by identifying the pending windows of microprocessor and introducing the restrictions of time order, and a validation tool is presented. The ARM memory model is explored and the formal definition of the model is given in the method. The time order constraints are obtained by scanning the performance counters of the ARM memory system periodically. The validation tool consists of three parts, namely, a random instruction generation module, a performance counter recording module and a results analysis module. The tool can effectively handle millions of lines of ARM multicore program because of the low time complexity of the algorithm. The validation tool is written in C++, and the length of the access memory instructions can be adjusted dynamically in run-time, which supports high extendability. Experiments with several infected errors in an ARM MPCore simulator show that the validation tool can detect these errors correctly, and that the proposed validation method and tool can effectively verify the ARM memory model.关键词：ARM processor;memory model;correctness validation1835|4|1更新时间：2025-05-01
- 摘要：A novel image-based method is proposed to automatically detect steering angle for vehicle modeling and safety analysis. A CCD sensor is installed on vehicles to construct a visual detection system, and edge extraction is implemented on the image captured by the CCD sensor. The extracted edge points of the steering wheel are then used in an ellipse fitting, and a preliminary steering angle is calculated using the algorithm for detecting the rotation angle of circle. The continuity of the vehicle movement is used to analyze the effectiveness of the resulting preliminary steering angle. The statistical values of steering angle increments are used to modify the steering angle and to obtain the final steering angle of the vehicle. Experimental results show that the average error between values of angles measured by the proposed method and those measured by the steering wheel-based method is 0.256 24°, while the average error between both of the angles is approximately 0.1° when the steering angles are in the concentrated interval [-4.15°, 4.15°]. The results show that the proposed method is able to effectively detect steering angles of moving vehicle during daytime.关键词：steering angle detection;ellipse fitting;rotation angle of circle1833|5|1更新时间：2025-05-01
- 摘要：For the reliability assessment of complicated electronic equipment, the thimbleful testing samples and the degradation characters data recognition become the main focuses. Thus, a new approach based on accelerated degradation tests of virtual samples is proposed. Relative nearness degree is introduced for degradation dada process, and the degradation characters data are represented by the relative nearness degree, then the original samples are expanded virtually and modified, and the degradation track of electronic equipment under various stresses is obtained. Combining the traditional reliability prediction, the difficulty of thimbleful testing sample is solved in the accelerated degradation tests. Example analysis shows that the error of the life prediction of a kind of electronic equipment is 5.93% by contrast with the factory calibrating error of service life, and the predicted service life of 86.27% samples is more than nine years, which indicates validity and higher ratio of efficiency to cost of the proposed method.1964|4|2更新时间：2025-05-01
- 摘要：To heighten sensitivity of permanent fault identification for single-phase-to-ground fault, a three-phase adaptive reclosure in transmission lines with shunt reactors is developed. It is found that the shunt reactor zero modal current gets with different free oscillation frequencies in transient fault or permanent fault fin the case of single-phase-to-ground. An identification model of shunt reactor zero-modal current is established, which includes decaying DC component and two frequency components corresponding to transient fault and permanent fault. Once the single-phase-to-ground fault occurs and circuit breakers open, each frequency component is obtained by least square fitting, where shunt reactor zero-modal current is available. The amplitudes of various frequency components are adopted to distinguish the permanent faults from transient faults. EMTP simulation shows that the proposed scheme is of higher sensitivity and freedom from the influences of transient resistance and fault position in permanent faults identification for transmission lines with shunt reactors.关键词：transmission line;current of shunt reactors;three-phase adaptive reclosure;free oscillation frequency;least square fitting1891|4|4更新时间：2025-05-01
- 摘要：An economic scheduling model for a microgrid is proposed by considering demand side management. Three types of loads, i.e., fixed, transferable, and user-action loads, are considered, and the management of transferable load is especially significant in the demand side management. In the case of time-of-use price, the formula of demand side management is described, and the harmonization scheduling model of the distributed generations with demand management is established. Function linearization facilitates converting the optimization case into a mixed-integer linear programming, and a commercial mixed-integer linear programming software is applied to solve the programming problem. The numerical tests for a microgrid indicate that with demand side management consideration, the total cost reduces by 3.83%.关键词：demand side mangement;load management;microgrid;optimal operation;mixed-integer linear programming2122|4|14更新时间：2025-05-01
- 摘要：To compensate the hysteresis and saturation characteristic of magnetic iron core, a nonlinear module based filter with memory effect is proposed. This module adopts polynomial functions instead of the coefficients of FIR filter to make the output get nonlinear fitting and memory. The existing parameters of magnetism gathering OCT(optical current transformer)measurements are used to train this module, whose output acts as an inverse function of the hysteresis and saturation characteristics. The experiments verify the effectiveness of the polynomial nonlinear compensation method with memory effect, the linear range extends 4.76 times, RMS error increases by about 15 dB, and output of magnetism gathering OCT keeps accurate in under-saturation state of magnetic iron core.关键词：magnetism gathering optical current transformer;magnetic saturation;memory effect;nonlinear compensation1877|4|2更新时间：2025-05-01
- 摘要：To investigate the effect of discharge area on discharge characters during partial discharge(PD)process, the variation of surface charge distribution is obtained via changing the void area, and its effect on PD magnitude is analyzed. When void size gets larger, streamer spreads freely after landing on the interface, and the discharge area varies in a wider range to lead to an intense fluctuation of discharge magnitude. Once the void diameter reduces to 1.5 mm, the variation range of discharge magnitude narrows due to the restriction of discharge area developing. As the void area becomes much smaller, the uniformity of discharge magnitude increases. Replacing the PE with aluminum foil to cover the interface, the variation range of discharge magnitude decreases to the minimum. When the void diameter gets to 0.7 mm, only one discharge takes place in each positive and negative half cycle, and the discharge locations coincide with each other, which results in an obvious effect of the magnitude of the former discharge on the phase of the subsequent discharge.关键词：surface charge;partial discharge;discharge area;discharge magnitude;discharge phase1739|4|3更新时间：2025-05-01
- 摘要：To design a preferable controller for the three-level H-bridge DC/DC converter, the topology of the circuit and principles of the converter with phase-shift PWM control are analyzed, so all the working modes both in CCM and DCM period get visible, the small signal models are thus established in CCM and DCM with average state space method and average switched network method, and their correctness is verified by the simulations. Following the small signal models, a double loop PI mode adaptive controller is designed. The comparative experiments for the new controller and the conventional PI one show that the changed mode results in a bad dynamic output, and the new controller adjusts the parameters instantaneously by mode examination. The output voltage droop of the new controller reduces by 46.6% compared with the common PI controller case under sudden loading.关键词：three-level H-bridge;phase-shift pulse width modulation;small signal model;control1993|4|2更新时间：2025-05-01
- 摘要：To solve the invalidity of traditional forward and backward substitution in distributed generation(DG)case, an improved forward and backward substitution method is proposed. Large deviation between the reactive initial value from the traditional method and the actual value leads to increasing iterations, so reactive power allocation theory is considered to determine the reactive initial value,and to improve the algorithm for modified reactive value. The traditional forward and backward substitution is unable to deal with PV-type nodes, they have to be converted to PQ nodes to solve. The relationship of reactive power revised value with voltage deviation of nodes and node reactance is obtained. The simulation indicates that for load flow of single invariable PV-type DG connecting to grid, the convergence needs 5, 7 and 7 iterations respectively for one to three PV-type DG grid. The increase of iteration number is less than 2 and the increased iteration period is less than 0.01 s to verify the reasonableness of the algorithm. For PQ-type and PI-type DG separate grid or mixing grid, the iterations of all options are less than 10, and increased period is less than 0.01 s.关键词：distributed generation;load flow calculation;backward and forward1862|4|7更新时间：2025-05-01
- 摘要：An improved re-sampling filtering algorithm is proposed to deal with the digital base-band shaping filter, which is applied in the highly dynamic signal measurement of aerospace TT&C(Track, Telemetry and Control)and satellite navigation systems. The design of truncated raise cosine filter is conducted to restore the continuous sequence of digital spread-spectrum signals. A spectrum adaptive piecewise parabola interpolation filter is constructed to carry out the signal dynamic re-sampling, and the Farrow implementation structure is adopted to reduce the calculation cost of the shaping filter. Simulation and experimental results show that the proposed shaping filter successfully adapts to Doppler frequency shifts, reduces the base-band signal phase jitter error from decimeter scale to millimeter scale, and effectively suppresses signal's out-band power. The proposed algorithm gives a way to improve the overall precision and steadiness of highly dynamic satellite signal measurement in missile and aerospace range.2124|4|1更新时间：2025-05-01
- 摘要：The maintenance effect in strategy of periodic preventive maintenance and periodic inspection/maintenance for petrochemical equipment is discussed. The proportional age reduction model and the delay time model with imperfect inspection maintenance are used to evaluate the equipment reliability. Improving the risk based maintenance(RBM)strategy, both objective and subjective methods are given to determine the reduction of equipment failure probability to keep subsystem risk under acceptable risk criterion. A model involving imperfect maintenance is presented to determine the optimal maintenance and inspection intervals. The improved RBM strategy is applied to the inspection optimization of a reforming reaction system(RRS). The results show that the risks of all subsystems in the RRS are acceptable when the inspection intervals of heat exchanger E201A/B, reactor R201～R204, water cooler E202A/B and air cooler A201 are reduced to 9 months.关键词：maintenance effect;risk based maintenance;inspection/maintenance optimization;reforming reaction system2036|4|2更新时间：2025-05-01
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