最新刊期
卷 43 ， 期 10 ， 2009
- 摘要：A Radix-8 complex divider with high performance and low power is designed. The complex divider architecture adopts the digit-recurrence algorithm and the prescaling technique of operands, and has an optimizing function, with which the prescaled operands are kept in redundant forms so that long carry propagation adders are saved. Moreover, combination of the real and imaginary parts of the internal quotient digits and optimization for hardware mapping based on the 6-input look-up table are made to improve the utilization of logic resources. The proposed design is then implemented on Stratix-II field programmable gate array. Simulation results and comparisons with the traditional structure show that the speed of the complex divider is increased by 44% and its hardware resources are reduced by 31%.关键词：complex divider;digit-recurrence algorithm;field programmable gate array3480|4|0更新时间：2025-07-09
- 摘要：Focusing on the high error of shape from shading(SFS)for diffuse surfaces, a fast SFS method based on Oren-Nayar reflection model(FSFS-ON)is proposed. The image irradiance equation for diffuse surfaces is established under assumptions that the camera performs orthographic projection and its direction is the same as the direction of the light source. The equation is then transformed into the Eikonal partial differential equation(PDE)that includes the shape information of the surface. The viscosity solution of the resulting PDE is approximated by using the monotone upwind Godunov Hamiltonian and the fast marching method so that the heights of three-dimensional surface are obtained. Experimental results and comparisons on synthetic vase image show that the CPU time of the FSFS-ON algorithm is greatly reduced, compared with the existing methods of the same kind, and that the root mean square errors of the heights of the FSFS-ON algorithm are decreased by 35.04%, compared with the method based on Lambertian reflection model关键词：shape from shading;diffuse surface;viscosity solution2999|4|4更新时间：2025-07-09
- 摘要：For lack of sparseness characteristic in support vector machines(SVM)by least squares solution(LSSVM), a density weighted pruning algorithm to improve the sparseness of the LSSVM regression model is investigated. The estimation error of training sample is weighted by corresponding density value and the potential contribution of training sample is obtained. Then the sample with the greatest value in the sorted spectrum of the potential contribution is selected as the support vector. The density and the potential contribution of training sample are updated and the potential contribution of the neighborhood sample of support vectors is significantly reduced. Thus the rechoosing of similar sample as support vector is properly avoided. More support vectors in the training sample set are iteratively selected, until the user-defined performance is achieved, thus the sparse LSSVM model is obtained. The simulation and practical applications indicate that the proposed method performs more effectively than Suykens standard sparse method for removing the redundant support vector with better sparseness and robustness.关键词：least square support vector machine;density weighted;sparse;mill load3240|6|7更新时间：2025-07-09
- 摘要：By analyzing the hydraulic system of the earthquake simulation platform in Xiamen science and technology museum, a nonlinear compensation approach for three-direction six hydraulic cylinder system is proposed, where the reciprocating movement parameters along x and y axles are adjusted according to reference area ratios, and ones of 4 cylinders in z-direction are set by experiments, so the non-linear compensations for each cylinder are achieved. The double close loops system composing of position error and velocity error is employed to turn the PID parameters adaptively. In addition, the steady errors caused by the leakage and dead-zone of the hydraulic cylinder can be compensated with zero compensation method. The whole algorithm is implemented on a host-servo MIMO real time control.关键词：three-direction;synchronization control;nonlinear compensation;zero compensation;real time2801|4|2更新时间：2025-07-09
- 摘要：Because of long test time, low efficiency and high cost of serial test, a parallel automatic test system(PATS)for missiles is designed and emulated based on parallel program. A task scheduling algorithm for PATS is brought forward based on the ant colony algorithm. Reconfigurable test unit adapters(TUA)and the combination of synchronization classes and instrument classes are designed in the hardware and software architecture of the PATS. A local search function, the probability of state transfer, the pheromone updating based on Tchebycheff inequality and the taboo formula are designed in the scheduling algorithm. Test task priorities are configured so that the optimized task scheduling is achieved. Emulation results show that the parallel test time is reduced to 30%-75% of the serial test time. Moreover, the scheduling algorithm gains an advantage over the TaskScheduler-T and the genetic annealing algorithm on aspects of average search time, probability of finding the optimal solution and so on.关键词：parallel test;reconfigurable test unit adapter;task priority;scheduling optimization;ant colony algorithm50|4|3更新时间：2025-07-09
- 摘要：A new mechanism of the message aggregation is proposed for debugging large-scale parallel programs. A remote source level debugging prototype system that is suitable for debugging large-scale parallel programs is created. The core of the message aggregation strategy includes: a tree structure that is used to aggregate and transfer the messages, and the resulting message returned by debug combination commands. Through the improved tree structure with fixed number the tree can be partitioned into two layers: a tree formed by nodes, and a tree formed by controllers within nodes, so that the amount of message passing between nodes can be greatly reduced. The serial debug tool GNU gdb is integrated into the bottom of the system to carry out the single process debug. A method of message combination is designed for satisfying the four kinds of gdb results. Meanwhile, the original output data of gdb are retained in the resulting information. Experimental results show that the debugging prototype system satisfies user's basic demands, simplifies the remote calculation, and shields the complicated hardware structure and processing flow.关键词：remote computing;message aggregation;parallel program debugging;tree structure3013|4|1更新时间：2025-07-09
- 摘要：A single sample biometric recognition approach is proposed based on the feature level and curvelet transform of the second-generation to improve the recognition rate of the single modal biometric system in application. Two kinds of biometric features are used. These are the palm-print feature and the face feature. All image samples are normalized and decomposed using the combination of curvelet & wavelet transform. Then the normalized curvelet & wavelet-transformed face and palm-print features are combined at the feature fusion level. The K-NN classifier is used to determine the final biometric classification, and then the recognition results are reported. The experimental results show that the proposed approach has better performance than the single modal solution: the best average recognition rate is improved to 92.40%,and the recognition rate is improved by 35.38% and 8.92% compared with single face feature and single palm-print feature respectively.关键词：multimodal biometric recognition;curvelet transform;face recognition;palmprint recognition;image fusion3265|4|2更新时间：2025-07-09
-
A Memetic Algorithm with Predictive Selection for Multi-Satellite TT&C Resources Scheduling Problems
摘要：Focusing on the problems that the model description of the multi-satellite spacecraft tracking, telemetry and command(TT&C)resources scheduling systems are commonly complicated and that the existing solution algorithms are usually not appropriate to large scale instances, the multi-satellite TT&C resources scheduling system is converted into a maximum independent set(MIS)problem in a special class of graphs by exploiting the binary-structure of the system constraints. Then a new Memetic algorithm with predictive selection is proposed to solve the strong deceptive problem that comes from highly multi-peak distributed structure of the MIS. An efficient and fast predictive operator is designed based on the analysis of the reachable domains. The operator can predict the maximum accessible profit of the crossover operation with different objects, and selects the best crossover object from several candidate ones, thereby searches for promising solutions. Simulation results on large scale benchmark graphs show that, the predictive selection strategy reduces effects of the deceptive problem and that the performance of Memetic algorithm is improved at an average of 17%.2767|4|6更新时间：2025-07-09 - 摘要：The traditional color-based mean shift algorithm is unable to accurately track the object in some challenging scenarios. A mean shift tracker that fuses multiple visual cues is proposed to address the problem. The search region of the object is partitioned into one target region and some background regions according to the estimated location of the object in the previous frame. Then based on the region partition, a novel histogram model is presented for characterizing the color and motion cues. The model can effectively suppress the clutter of adjacent backgrounds. Finally the visual tracker is proposed within the mean shift framework to fuse the color and motion cues so that both. The visual cues can be complemented each other and the accuracy and robustness of tracking is improved. Experiments show that the proposed tracker can obtain more accurate and robust tracking results in some challenging scenarios such as rapid motion, large pose variation or occlusion of objects.关键词：visual tracking;color cue;motion cue3053|4|1更新时间：2025-07-09
- 摘要：Focusing on the limitations of the existing route repair algorithm for ad hoc networks, such as without considering the nondeterminacy of the node state, setting a single node as the routing destination, and low repair efficiency, a new route repair mechanism is presented based on link failures. The mechanism doesn't always regard the moving node at working state. The status changes of downstream nodes from the repairing node are used as the basis of choosing route repair schemes. The causes of link breaks such as mobility between nodes, node failures and node power-off are analyzed according to the change of node status, and different nodes are selected as destinations for RREQ. RREQ with multiple destinations is broadcasted by the repairing node. Mathematical analysis and simulations are carried out to evaluate the network performance. Results under different node failure circumstances show that the average route setup time of the proposed mechanism is reduced by 13%, the control overhead ratio is decreased by 18%, and that the proposed mechanism is well applicable to real networks.关键词：Ad Hoc network;route repair;link failure3345|4|0更新时间：2025-07-09
- 摘要：Aimed at the problem that the vulnerable wireless local area network(WLAN)802.1X protocol is not susceptible to replay and DoS(denial of service)attacks, etc, an informal method is introduced to analyze the security properties of 802.1X protocol. The method classifies attack behaviors according to the ability of attackers, and from the aspect of the role which attackers can play in the protocols(i.e., imitating normal protocol behavior or breaking normal communication). Then a new method, WLAN active testing, is proposed. Attacks to the protocol running mainbody are implemented by simulating the actions of the attacker which can be used to make up protocol messages. The results are used to determine whether the protocol security vulnerabilities exist or not. Testing results show that the method combines characteristics of both the attacker and the tester to cover some known protocol security vulnerabilities, and has the ability to reveal some potential problems.关键词：wireless local area network;security analysis;active testing3389|4|2更新时间：2025-07-09
- 摘要：The network dynamics is one of the most important factors that impact the stability of the mesh streaming networks. A streaming multicast mechanism using redundant coding is proposed to alleviate the influence to the transmission performance from dynamic nodes. The media source encodes the stream into several sub-streams with equal length redundantly, and distributes them to different successors. Each node in the network establishes the cooperative relationships with others to get the required sub-streams. A parent selection algorithm with relatively lower complexity is proposed to take full advantage of redundant coding. In case of node's failure, a repairing algorithm of swap-in-turn between different sources of sub-streams is proposed. The algorithm makes the best use of the current parents to ensure high continuity of steaming transmission. Simulation results show that the multicast mechanism can ensure high quality for more than 90% users when the churn rate is below 10; and the codes with higher redundant degree can adapt to more dynamic scenario; and that the codes with redundancy less than 33.3% does not significantly decrease the effective transmission rate when the churn rate is beyond 8.关键词：overlay network;streaming;redundant coding3022|4|1更新时间：2025-07-09
- 摘要：According to the scheduling problem in storage aggregating of application-level, a scheduling algorithm for load balance sensitive storage(LBS)is proposed based on policy. In the LBS algorithm, requirements from applications for storage are represented as a series of restrictions. The LBS then makes choice between new appropriate storage nodes and existing scheduling scenario by analyzing relations between restrictions so that the reusability of scheduler scenarios can be improved. The LBS maintains the balance between the reusability of policy and the load of storage, and achieves the goal of load balance finally. The simulation and comparisons show that the LBS outperforms the Random and the Least obviously in load balancing, policy decupling and scalability, and that the load balance of the LBS improves 10 times against the two baseline algorithms.关键词：application-level storage aggregating;schedule algorithm;load balance3334|4|1更新时间：2025-07-09
- 摘要：A decision model of redundant node without the location information is proposed for heterogeneous wireless sensor network to prolong the wireless sensor network useful lifetime as well as to maintain sufficient sensing coverage at a specific application level. Based on the model, a useful lifetime maximization for partial coverage conserve in wireless sensor network(ULMPCC)protocol is proposed. The protocol allows for closing all redundant nodes that have relative less residual energy according to their residual energy states so that the least number of nodes are maintained as working nodes and the distributed collaborative scheduling of nodes is achieved. The residual energy-based election strategy in ULMPCC effectively balances the network energy consumption, and maximizes the useful network lifetime. Simulation results show that ULMPCC guarantees the desired coverage QoS accurately and minimizes the number of active nodes. The error between the resulting coverage QoS and the desired coverage QoS is less than 1% when the desired coverage QoS is greater than 90%.关键词：coverage QoS;node scheduling;network useful lifetime;heterogeneous wireless sensor network3126|4|3更新时间：2025-07-09
- 摘要：The performance and scalability evaluation of the large scale simulation software on planetary fluid dynamics are investigated by the experiments on the domestic 100 TFlops supercomputer, Dawning 5000A. The details of the software testing procedures, the environment and the process of the testing are introduced. For the mesh size of 80×80×50, the performance testing on 16 to 128 processor cores with mapping 4 processes on each node and the performance testing on 16 to 512 processor cores with mapping 16 or 8 processes on each node are performed, respectively. The relative speedups reach 5.33, 10.48 and 12.57, respectively, and the corresponding parallel efficiencies of these 3 testing cases are 66.66%, 32.58% and 32.29%, respectively. For the mesh size of 160×160×100, the performance testing on 64 to 8 192 processor cores with mapping 16 processes on each node gives the results that the relative speedup is 12.46, and its parallel efficiency is 9.73%. The experimental results reveal the good performance of Dawning 5000A and show important clues of the software optimization.关键词：Dawning 5000A;numerical simulation;performance evaluation;scalability532850|14|0更新时间：2025-07-09
- 摘要：Based on the model of cylindrical waveguide coated with lossy conductor on its inner surface, the effects of the coated layer on the propagation characteristic of electromagnetic wave are studied.The characteristic equation is derived from the electromagnetic equation and boundary conditions under the assumption that both the conductivity and thickness of the coated layer and the waveguide wall are finite. Then the approximate analytic formulas for the propagation constants are obtained. Finally, the effects of the coated lossy layer on the propagation characteristic are presented. The approximate analytic results agree very well with the numerical solutions obtained by solving the characteristic equation. The results show that the lossy layer has a great effect on the propagation constants when the thickness is smaller than 2 times the skin depth of the lossy layer.关键词：cylindrical waveguide;coated layer with conductor;propagation constant;characteristic equation3270|4|3更新时间：2025-07-09
- 摘要：To improve the performance of motion estimation(ME), a new fast motion estimation algorithm is proposed for motion complexity decision(MC-FME). The algorithm adaptively estimates the frame-level motion complexity by using the frame texture information and the macro-block residual value at first, and then adaptively estimates the macro-block-level motion complexity by calculating the variations of predictions in the prediction set of the macro-block motion vectors. The complexity is finally used to estimate the motion. Experimental results and comparisons with the diamond search algorithm and the hierarchical motion estimation algorithm show that the proposed algorithm can get 5% to 21% reduction in the number of matched points and save 3% to 5% motion estimation time while the image quality is guaranteed.关键词：motion estimation;motion complexity;adaptive3612|4|3更新时间：2025-07-09
-
A Finite Difference Frequency Domain Method for Waveguide with Rough Surface and Imperfect Conductor
摘要：A finite difference frequency domain method(FDFD)is presented to analyze the propagation characteristics of waveguides with imperfect conductor and rough surface. Two curl equations in the Maxwell system are discretized with difference method in the cross-section of the waveguide, and the loss surfaces and rough surfaces of the waveguide are replaced by the surface impedance boundary conditions(SIBC)and the equivalent SIBC, respectively. Then the eigen equations about the electromagnetic field components are formed and solved to obtain the propagation constants for a given frequency. Comparison with the perturbation method shows that the presented method is effective when the interested frequency is under cutoff frequency and the waveguide has irregular boundary. The simulation results show that with the increase of roughness, the attenuation constant is gradually increased to 2 times of that with smooth surfaces.关键词：finite difference frequency domain;propagation constant;rough surface;equivalent surface impedance boundary condition4904|4|1更新时间：2025-07-09 - 摘要：A method of modifying display gray levels is proposed to reduce the dynamic false contour(DFC)in alternating current plasma display panel(AC PDP). The sub-field coding adopted in AC PDP is utilized to give a quantitative measure of the DFC by the motion picture distortion(MPD)distance method. Then, the gray levels in which the DFC is not observed are displayed. At the same time, the quality of the output image is enhanced by the digital halftoning technology. The noises generated by bigger quantified errors can be reduced effectively by the error diffusion method with accepting the nearest threshold. On the other hand, the pixels with the lower grayscale are processed by the ordered dithering method. Consequently, the DFC in the moving images can not be observed and the images are represented better in the whole grayscale scope. The proposed method is applied to an 81 cm AC PDP and experimental results show that the DFC in the moving images is reduced effectively under the premise that the image quality in AC PDP is not affected.关键词：alternating current plasma display panel;dynamic false contour;digital halftoning;error diffusion;ordered dithering3351|4|0更新时间：2025-07-09
- 摘要：To overcome the shortage of the conventional bilinear method in diffraction ultrasound tomography reconstruction, an accurate reconstruction algorithm is proposed by using kernel convolution interpolation. The first step of the algorithm calculates the reconstruction data by Shepp and Logan, and the kernel matrix obtained in the least squares nonuniform fast Fourier transform(LS-NUFFT)algorithm is used for the convolution kernel. Then the kernel matrix is used to interpolate the non-Cartesian sampling reconstruction data into the Cartesian grid.The image reconstruction is finally fulfilled by 2-dimensional IFFT. Comparisons with the bilinear method and the Gauss kernel convolution method show that, the reconstruction error in 2-norm is reduced more 40% than the bilinear method, and that the reconstruction time is shortened about 50% compared with the Gauss kernel convolution method.关键词：diffraction tomography;nonuniform fast Fourier transform;kernel matrix3168|4|2更新时间：2025-07-09
- 摘要：A new type of pilot protection for transmission line with shunt reactors at double terminal following parameter identification is proposed. Based on the fault component nets, R-L models with the same pattern are established for the internal fault state and the external fault state. The inductance in R-L models can be evaluated by parameter identification. When an internal fault occurs, the inductance reflects the impedance of the system source as a smaller minus, and when an external fault occurs,it signs the inductance of reactor as a greater positive,thus the internal fault and external fault are distinguished. The criterion is not influenced by the transient components and fault resistance, and also can be easily set. EMTP simulation shows the higher sensitivity, reliability and effectiveness.关键词：transmission line;pilot protection;parameter identification;shunt reactor3116|4|6更新时间：2025-07-09
- 摘要：To realize systematic analysis and forecast for electromagnetic susceptibility(EMS), a method is presented to characterize electromagnetic interference(EMI)coupling path of signal port of relay protection equipment in power system. Referring to test standard of IEC, the transfer function of EMI coupling path in frequency domain is gotten according to the tested interference waveform. Based on discrete value by sampling in frequency domain, the vector fitting method(VFM)is adopted combining rational function approximation to construct the macromodel and equivalent circuit of EMI coupling path,thus the problem of ill-condition matrix with high order approximation is alleviated and the mixed frequency/time domain problem is solved. Good coincidence between the simulated result and the measurements demonstrates the validity of this modeling method.关键词：relay protection equipment;electromagnetic interference coupling path;vector fitting method;macromodel3119|4|1更新时间：2025-07-09
- 摘要：A calculating model considering nonlinearity of both the transformer inductance and the losses is presented,where the simulated transformer is by nonlinear inductance and resistance in parallel. The calculating method for the characteristic curves of the nonlinear inductance and resistance with the data of voltage, current and power losses measured in no-load test is proposed to simulate and evaluate the ferroresonance overvoltage, and the experiments are accomplished to verify the accuracy. The results show that the error between simulation and experiment approaches 3.81% and 0.2% respectively for the peak value of transformer voltage and circuit current by nonlinear resistance model, far lower than 19.5% and 15.9% by constant resistance model.2815|4|3更新时间：2025-07-09
- 摘要：To investigate the effect of varying load on the synthesis ammonia, the process of a large-scale ammonia synthesis plant is simulated with the process and operational parameters of the petrochemical company by ASPEN PLUS, and the operational characteristics on varying load conditions from 85% to 100% are analyzed. Thermal efficiency and exergy efficiency of the key equipment, such as heating-furnace, primary reformer and auxiliary boiler are evaluated, and reaction conversion ratio of the reactors is obtained. It is suggested that reducing the amount of input air to the heating-furnace and primary reformer and enlarging the area of the steam overheating coil in the convection part of the primary reformer can utilize energy efficiently. The curve and expression between energy consumption of the ammonia synthesis with load of 85% to 100% are fitted by Newton interpolation polynomial for synthesis ammonia output in the plant from 1 000 t/d to 1 500 t/d. Thus it is predicted that energy consumption of the synthesis ammonia approaches 36.707 GJ/t to 40.797 GJ/t, which agree well with the field data with a deviation less than 3%.关键词：synthesis ammonia;varying load;energy consumption of synthesis ammonia;fitting curve3262|4|0更新时间：2025-07-09
- 摘要：Focusing the capacity of the circle of Willis(CoW)and the cerebral hemodynamic changes before and after clamping internal carotid artery(ICA)during carotid endarterectomy(CEA), a 3D computational model was developed combining patient-specific CT images with CAD software. A series of different axisymmetric stenosis were artificially inserted in right internal carotid artery(RICA). Non-Newtonian blood flow in CoW was simulated under steady flow condition by ANSYS-CFX. The results show that cerebral blood flow gets redistributed as the degree of stenosis is greater than 50%. Collateral flow in anterior communicating artery(ACoA)is much more important than that in posterior communicating artery(PCoA). As cerebral blood flow(CBF)is proportional to blood pressure, raising blood pressure facilitates improving the cerebral blood supply efficiently during the CEA operation. However, while ACoA missing, the blood supply can not be simply maintained by raising blood pressure, a shunt is necessary.关键词：circle of Willis;arterial stenosis;3D reconstruction;blood dynamics3143|4|2更新时间：2025-07-09
- 摘要：The direction of information flow within electroencephalogram(EEG)and the relationship between functional coupling at different electrode pairs and cardiac automatic nervous system during a mental arithmetic(MA)task are explored with partial directed coherence(PDC). Forty-three healthy male subjects voluntarily participate in the project. The sympathetic and parasympathetic activities are estimated with heart rate variability obtained by power spectral analysis of R-R intervals. The results show that when mental arithmetic task is implemented heart rate increases(P<0.01), the sympathetic activity increases and the sympathetic activity decreases(P<0.01); relative wavelet packet energy in alpha rhythm of EEG decreases and the beta rhythm of EEG increases significantly(P<0.01); the direction of the information flow changed from posterior-to-anterior direction to anterior-to-posterior direction and the information flow get stronger(P<0.05). There are obvious correlations between the increases of frontal and posterior coupling and heart rate variability(P<0.05). It is noted that anterior-to-posterior direction of the cortical functional coupling enhanced with the decrease of parasympathetic activity and increase of sympathetic activity, and the post-central areas influence heart rate by virtue of increasing sympathetic activity and decreasing parasympathetic activity during MA.关键词：autonomic nerve;coupling;partial directed coherence;mental arithmetic task;heart;cortex2905|4|3更新时间：2025-07-09
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0