最新刊期
卷 31 ， 期 8 ， 2003
- 摘要：The ever-rising complexity of operating system and communication networks has resulted in increased difficulty in detecting intrusions.So applying immune mechanism of human body to construct next generation intrusion detection becomes a new research focus.This paper presents a novel method to encode the antibody-antigen.And An generic algorithm based on niche technology of share function for generating diverse antibody is provided.In order to verify the validity of the algorithm,two evaluation function are suggested.The experimental results reveal that the algorithm has much to offer to keep population's diversity during evolution.关键词：immune system;antigen-antibody;niche;diversity2|1096|7更新时间：2025-07-16
- 摘要：A concrete method and expression form describing the meaning of a sentence by its skeleton is obtained.A knowledge database of this form is established in this system.Each record expresses the common feature of different sentences that describe the same matter.And the similarity degrees between sentences are calculated by fuzzy matching method.关键词：term;sentence skeleton;fuzzy matching;error membership2|2079|4更新时间：2025-07-16
- 摘要：Instruction supply can influence processor performance greatly.Instruction prefetching is an effective mechanism to reduce instruction cache miss rate.It proposes an instruction prefetching mechanism based on program control flow graph,while sequential prefetch and non-sequential prefetch are both employed to fetch instructions in advance.Experimental results show it can increase instruction cache hit rate effectively.It predicts program behavior statically so that it does not need any complex hardware to predict and restore.关键词：control flow graph;instruction prefetch;branch prediction2|1575|7更新时间：2025-07-16
- 摘要：Priority inheritance protocol is used to improve the scheduling precision of real time system with synchronization and exclusive requirements and hence increase the predictability of the behavior of an operating system.But the protocol and correspondent implementations do not involve non-exclusive mutex,such as reading lock.The paper gives rise to an algorithm of priority inheritance of non-exclusive mutex and analyzes the property of the protocol,on the basis of which an implementation under Linux is described.关键词：real time;non-exclusive mutex;priority inheritance protocol;priority inheritance;linux;preemptable kernel2|1036|0更新时间：2025-07-16
- 摘要：The research of access control model is a topic of information security area.There are many access control models in existing literatures,but they process the access requests only depending on existing conditions by themselves.Therefore they are not able to meet the need that authorization process must interact with users and that user's promises of the future actions are authorization conditions under electronic commerce environment.A promise-assurance-based access control model (PABAC) is presented to achieve the above access control need.Its architecture,promise & assurance mechanism, separation of duties of authorization and access control are discussed.The experimental results express its validity.关键词：access control;interacting authorization;promise;assurance;separation of duty2|935|1更新时间：2025-07-16
- 摘要：With the advent of XML as a standard for data representation and exchange on the Internet,storing and querying XML data becomes more and more important.This poses a new challenge concerning indexing and searching XML data,because conventional approaches no longer apply to XML data.A variety of novel indexing techniques for efficiently retrieving the results have been proposed in the recent literature.However,relative path based query still needs to be more efficient.A containment based indexing scheme for XML data is proposed,which makes full use of the topological structure of the XML documents and can be more efficient to deal with relative paths than previous methods.The key properties of the scheme are as follows:(1)Transform relative paths to absolute paths by using the topological structure of the XML documents instead of DTD or XML Schema;(2)Apply a numbering scheme to the topological structure,which can quickly determine the ancestor-descendant relationship between elements in the hierarchy.Experimental results from the prototype system implementation shows that the scheme can be used to process XML queries with regular path expressions(especially relative paths)faster than previous approaches.关键词：XML;query;index4|1359|4更新时间：2025-07-16
- 摘要：Graphical Electromagnetic Computing(GRECO)is one of the valuable method for computing the radar cross section(RCS)of complex radar target in high frequency region.But there are some shortages of edges detecting method in original GRECO literature[1],a new method of collecting the edge pixels and wedge parameters is presented in this paper.Since an expression of edge diffraction field in the literature[1] is in error,the error-correcting formulas are derived by using method of equivalent edge currents(MEC)and physical theory of diffraction(PTD).Finally,the total RCS expression is given by using physical optics(PO)and PTD method.The computing results are in close agreement with the measured data.关键词：electromagnetic wave scattering;GRECO;radar cross section;edge diffraction2|1296|5更新时间：2025-07-16
- 摘要：A simulation approach was proposed to analyze the spectra of Doppler signals from the steady flow within a stenosed vessel.The vorticity transportation and stream function equations were used to calculate the velocity distribution within the stenosed vessel.The spectral power density function of Doppler signals was estimated at variant positions along the vessel.The maximum frequency,the mean frequency and the spectral bandwidth were calculated from the spectra,which were used to analyze the characteristics of Doppler signals from stenosed vessels with different degrees of stenoses and flow velocities.关键词：stenosis;vorticity;stream function;power spectrum2|1007|0更新时间：2025-07-16
- 摘要：Search engines usually get web pages by using links between them.With already massive and ever increasing of web pages,they can only crawl and index a portion of the whole web pages.A model to evaluate their information coverage percentages is presented.We analyze main factors why crawlers can't cover all web information,and put up three kinds of benchmarks to measure the coverage of a search engine.The paper gives out an evaluation model for two of three benchmarks as follows:First,sampling WWW to get many web pages,which are used to check the coverage percentage of quantity through generating random IPs or breadth first search.Second,selecting high-qualified pages as samples of important pages,by HITS or PageRank algorithms.Finally,we submit the samples to page database of search engines,and get the coverage percentage.In our research work,we get experimental data from WebInfoMall system of Peking University and compute the coverage percentages of quantity and quality.Using different sampling approaches and algorithms,we get the same results,which can prove our model is right and all the results are exact.关键词：search engine;information coverage percentage;Sampling;weight computing;check;quantity coverage percentage;quantity coverage percentage2|1816|2更新时间：2025-07-16
- 摘要：As one of the most challenging problems in the upcoming next-generation high-speed networks,quality-of-service routing (QoSR) with multiple constraints has the NP-complete complexity.A precomputation algorithm,MEFPA,was proposed.This algorithm divides the significance of each QoS weight into multiple degrees,and constructs a number of linear energy functions (LEFs) distributed uniformly in the multi-dimensional QoS metric space.Using LEFs,it then converts different QoS weights to a single energy.At last,it uses Dijkstra's algorithm to create the least energy trees,based on which the QoS routing table is created.The performance of LEFs with constraints is analyzed,and the method is given to determine the feasible and unfeasible areas in the multi-dimensional QoS metric space for a QoS constraint.Then MEFPA for the multi-constrained QoS routing problem was introduce.Extensive simulations show that our easily implemented MEFPA is a promising precomputation algorithm to provide QoSR with high scalability and high performance in high-speed networks.关键词：linear energy function;QoS routing;precomputation;multiple constraints;scalability2|1374|5更新时间：2025-07-16
- 摘要：The increase of digital circuit integrity and complexity has made fault diagnosis of circuits more and more difficult.The scale of test set has become very large because of redundancy,which costs lots of time and memory unnecessarily.It is important to acquire optimal test set for test application.Test set optimization,which can eliminate the redundancy,is one of key problems in fault diagnosis of digital circuits.Ant colony optimization,a new kind of random optimization algorithm,has become a better alternative to genetic algorithm in some areas.That algorithm has such advantages as less parameters and simple operations,so it is easier to be adopted.We propose a method based on ant colony optimization that solves test set optimization better than classic algorithm or genetic algorithm.The better performance of the proposed method is demonstrated by experimental results.关键词：ant algorithm;test optimization;fault diagnosis2|1140|8更新时间：2025-07-16
- 摘要：Carbon nanotubes prepared by catalytic pyrolysis method have been considered as active electrode materials for the storage of energy in supercapacitors.Due to their unique mesoporosity,this material has a high ability for the accumulation of charges in the electrode/electrolyte interface.Electrochemical capacitors based on carbon nanotube electrodes have been developed in this paper.The value of capacitance obtained from nanotubes reaches 42F/g.The new technique for getting high working voltage was discussed in detail.The working voltage over 20V and resistance less than 360mΩ was obtained.Characteristics of capacitance and resistance for this type super capacitor were described.关键词：carbon nanotubes;supercapacitor;double layer capacitor2|1471|2更新时间：2025-07-16
- 摘要：LSA (Logarithmic Skip Adder) Algorithm is introduced in this paper.LSA is a hybrid structure of carry skip adder and ELM carry lookahead adder,which replaces serial carry chain with binary tree structure.In structure design,a carry-incorporated structure to include the primary carry input in carry chain is found to reduce logic depth.With its regular structure,32-bit LSA has a logic depth of 8 and a fanout no more than 5.Circuit simulating results in 0.25um CMOS process show a critical path delay of 760ps.关键词：adder;logarithmic skip;structure design;carry-incorporated2|1638|5更新时间：2025-07-16
- 摘要：A kind of piezoelectric transformer works in the bend vibration mode is discussed.Compared with other kind of piezoelectric transformers,this transformer can realize low frequency with small geometry size.Theoretical analysis and deduction are given through energy method,and the equivalent circuit model is found.Furthermore,the component is fabricated and tested,and the testing result is agreed with the calculated result.关键词：piezoelectric transformer;bend vibration;equivalent circuit2|959|1更新时间：2025-07-16
- 摘要：The effects of polarization mode dispersion and filters control are studied in systems of high speed OTDM dispersion managed soliton.Firstly,the dispersion managed soliton (DMS) transmission equations considering effects of polarization mode dispersion and filters are built.Secondly,the filter control DMS transmission with constant birefringence fibers is analyzed by Variational method,from which the transmission rule of DMS characteristic parameters can be obtained.At the same time,the stabilities of DMS transmission and its timing jitter rules controlled by filters are also investigated.Based on the expressions of timing jitter obtained by variational method,the timing jitter of three systems is discussed,with the results reveaing that it is very effective for filters to restrain the influence of PMD in DMS communication systems.关键词：polarization mode dispersion;dispersion managed soliton;filter2|886|1更新时间：2025-07-16
- 摘要：A robust configurable multiplexing approach is proposed,which presented 2∶1,3∶1,4∶1,5∶1 multiplex modes.Its cascade structure can realize all multiplexing modes except prime numbers of greater than 6.Based on this approach,an IC was designed to achieve the 10:1 multiplexing at the bit rate of 1.25Gbps.It used high speed units to improve the design efficiency and to realize low power.It has been developed using 0.35μm CMOS technology and the layout was finished in full custom method.The chip was realized through a foundry technology and measured on wafer.The chip area is 24.19 mm2.The power dissipation is 174.84mW under a 3.3V supply.The measured output voltage is 2.42Vp-p based on 50Ω load,the duty cycle is 49% and the phase jitter is 35ps rms at the 1.25Gbps standard bit rate.The highest speed of serial data is 1.62Gbps.关键词：fiber communication;multiplexer;CMOS process;integrated circuit2|1106|1更新时间：2025-07-16
- 摘要：A multi-functional 2×2 multimode interference optical switch based on the deep-etched GaAs/GaAlAs optical rib waveguide with spot-size converter is proposed and analyzed by using the variable transformed series expansion method and three-dimensional finite difference beam propagation method.As a result,the present device can operate in various kinds of output schemes including cross and bar state as well as 3dB coupler by controlling the Schottky electrode located in the center of the only multimode waveguide with the advantages of compactness,high design tolerance,and large optical bandwidth.Moreover,the deep-etched optical rib waveguide satisfies the requirement of the accurate self-imaging,greatly reduces the bent loss,and has large cross section under the single mode condition.In addition,the spot-size converter introduced in the ends of the input/output channels can be conveniently coupled with the single-mode fiber.关键词：optical switch;multimode interference;GaAs/GaAlAs;variable transformed series expansion method;three-dimensional finite-difference beam propagation method2|953|3更新时间：2025-07-16
- 摘要：Adaptive equalization algorithm based on wavelet packet transform is proposed in the paper,upon the basis of the given orthogonal matrices corresponding to discrete orthogonal wavelet packet transform.The performance of the algorithm is analyzed,and we prove the analysis results,from computer simulation.Additionally,in order to apply wavelet packet transform based adaptive equalization algorithm to various fields,the approach to minimize computational complexity is given.关键词：adaptive equalization;wavelet packet transform;optimized algorithm;orthogonal matrices2|1293|10更新时间：2025-07-16
- 摘要：Although discrete chaotic systems is sensitive to initial conditions and its behavior seems to be random,it is not really stochastic process but determinate.It results in that chaos based encryption schemes are not good as we expect.In order to enhance the performance of the encryption algorithms based on discrete chaotic dynamical system,we present composite discrete chaotic dynamical systems and gives some results about its invariant distribution density and iteration sequence.We present a new approach to stream cipher utilizing a peculiar composite discrete chaotic dynamical system.Because of its sensitivity to initial conditions and randomness of the iteration sequence,the approach mingles secret keys with plaintext by iterating the chaotic system to produce ciphertext.Therefor they hold very complex and sensitive nonlinear relations.It prevents ciphertext to leak the information of plaintext and secret key and makes the security of the algorithm independent of the complexity of the ciphertext.The algorithm is provided with larger secret space and uniform distributing ciphertext.关键词：chaos;dynamical system;stream cipher2|1173|12更新时间：2025-07-16
- 摘要：We present the calculated results of DC and AC characteristics of wurtzite GaN static induction transistor by two dimensional full band,ensemble Monte Carlo simulations.The gate length of SIT is 0.13 micron and the distance between source and drain is 0.5 micron.We obtained the output characteristics,transconductance and current cutoff frequency characteristics of SIT by the Monte Carlo simulations.The maximum transconductance is 140 mS/mm at a gate-source voltage of -1.5V,and the maximum current cutoff frequency is 123 GHZ at a drain-source current of 3.15A/cm.The calculated results indicates that wurtzite GaN SITs have a potential for applications in high power and high frequency.关键词：monte carlo simulation;GaN;static induction transistor;compound semiconductor2|794|0更新时间：2025-07-16
- 摘要：In this paper,we will present a kind of chaotic synchronization method using phase control.In this method,the phase and state errors between the sending and the receiving ends are sampled when the traces in the phase space of sending and receiving ends reach the Poincare planes set in advance.After processing,the sampled data are used to control the phase and state of receiving end so that the system gets synchronization.In this paper,the Chua's circuit will be used as system model to study this kind of synchronization method in details,and we also present the simulation results of the system.关键词：chaos;phase control;Chua's circuit;synchronization3|890|1更新时间：2025-07-16
- 摘要：Based on a series of operations such as detecting candidate target trajectories,the optimal algorithm of maximum likelihood ratio judgment and post-processing,etc.,this paper presents a kind of adaptive algorithms that can automatically recognize the point targets making straight movement with uniform velocity in the field of view from low SNR image sequence in which CN- and UCN- sequences are all suppressed. The theoretical analyses and optimal algorithms of various kinds of operations are expounded in the paper. The experimental results have proved the correctness of theoretical analyses and the feasibility of the adaptive algorithms. The lowest distinguishable SNR is 0.5,and the optimal algorithms are compatible with infrared- and television image sequences. The quantity of data processing can be also greatly reduced by the optimal algorithms.关键词：adaptive algorithms;target trajectories;maximum likelihood ratio;target recognition;image sequence;data processing;optimal algorithm2|937|1更新时间：2025-07-16
- 摘要：A novel multiple access control (MAC) protocol——User-dependent Perfect-scheduling Multiple Access (UPMA) protocol,which supports joint transmission of voice and data packets,is proposed.By this MAC protocol,the bandwidth can be allocated dynamically to the uplink and downlink traffic according to their respective service requirements.UPMA protocol endows different priority levels to different types of traffic,and can perfectly schedule the transmission of mobile terminals (MTs) by means of polling.Meanwhile,a unique frame structure is designed to guarantee that the voice traffic is always transmitted prior to the data traffic.Furthermore,an effective collision resolution algorithm is proposed to guarantee rapid channel access for activated MTs.Finally,performance of UPMA protocol is evaluated by simulation and compared with that of MPRMA protocol.Simulation results show that UPMA protocol has better performance.关键词：MAC protocol;quality of service (QoS)2|803|1更新时间：2025-07-16
- 摘要：This paper introduces the achievements of Internet end-to-end performance measurement technologies,including metric-induced topology inference,delay inference,loss probability inference and bandwidth measurement.Finally,we point out the application trend in this field and present some topics to be further studied.关键词：network measurement;delay;loss probability;topology inference;metric-based inference2|1788|16更新时间：2025-07-16
- 摘要：A systematic method of designing multiple-loop feedback current-mode nth-order lowpass filter based on multiple outputs current controlled conveyor is presented.Different kinds of nth-order low-pass filter structure are obtained by this method.The proposed nth-order filter is constructed by n CCCIIs and n grounded capacitors.PSpice simulation for an actual circuit is conducted,and the result shows that the proposed circuit is valid and effective.关键词：current-mode;current controlled conveyor;feedback network;active filter;systematic design2|1255|16更新时间：2025-07-16
- 摘要：After analyzing status quo of high dependability safeguard mechanism,an integrated high dependability safeguard systematic framework supporting multilevel criticality in which several subsystems share the same system resources is brought forward.In order to avoid deleterious interferences between subsystems with different criticality,a kind of high dependability temporal isolation mechanism based on two level scheduling approach is brought forward.In order to realize this mechanism,integrated high dependability safeguard mechanism supporting multilevel criticality based on single node computer is emphatically researched .The scheduling model is constructed.The schedulability of tasks and subsystems are analyzed.The correctness of time isolation mechanism is proved by several samples.The conclusion of researching on high dependability safeguard may be applied to the other no safety-related areas,and has great practicability.关键词：safety critical;multilevel criticality;high dependability;schedulability analysis;temporal isolation2|779|2更新时间：2025-07-16
- 摘要：In order to overcome long burst error induced by scintillation in atmospheric optical wireless channel,the paper proposes an iterative decoding scheme based on photons counting and analyzes performances of the iterative decoding scheme over atmospheric optical wireess channel.Compared with former channel interleaving+Concatenated codes scheme,the scheme significantly improves anti-jamming performance of system without channel interleaving delay,and the scheme reduces complementation complexity.关键词：optical wireless channel;photons counting;iterative decoding2|1098|1更新时间：2025-07-16
- 摘要：In a hybrid recording system,since the coercivity is dependent on temperature,an external laser may be used to locally reduce its value to a point where the field from the magnetic head is sufficient to switch the magnetization;In this paper the relation between the hybrid recording magnetic field and the thermal field,the recording media heat domino effect have been studied,the results indicate that the rectangle waveguide near field heating technology can break superparamagnetic limit and meet the demand of hybrid recording.This is a high potential method and can increase storage density consumedly.关键词：hybrid recording;superparamagnetic limit;integration of magnetic head and optical head;dual-gradient recording2|1003|1更新时间：2025-07-16
- 摘要：A new architecture of an embedded Flash CISC/DSP microprocessor is presented.Under unified enhanced complex instruction set,The single core processor has been implemented by using RISC and pipeline design principles based on Harvard and register-to-register architecture.To achieve double functionality of DSP and general CPU,we have combined general CPU、embedded FLASH、instruction buffer and DSP functional units,such as single clock MAC、barrel shifter、fast loop processing unit,etc. in a single architecture.This processor is fabricated using 0.35μm CMOS process,and the power consumption of the chip is less than 425mW working under 3.3V voltage and 80MHz clock.The low-cost high performance microprocessor is well suited for a wide range of SOC applications.关键词：CISC;VLSI;pipeline;DSP;flash memory2|976|1更新时间：2025-07-16
- 摘要：The principle of generating high-speed true random bit sequence using white noise is discussed.High-speed true random bit sequence was generated using broadband white noise source and high-speed D flip-flops.The jitter caused by the meta-stable state was eliminated.关键词：white noise;D flip-flop;high-speed true random bit sequence2|1092|2更新时间：2025-07-16
- 摘要：Based on the MOSFET PDE model we present a new iterative algorithm for the periodic steady state analysis of RF autonomous circuits.We illustrate the new algorithm with the simulation of a Colpitts oscillator.The results are compared with those obtained by MEDICI.关键词：RF autonomous circuit;MOSFET PDE;periodic steady state solution2|1041|0更新时间：2025-07-16
- 摘要：Similarities and differences of irradiation effects between floating gate ROMs (Read Only Memory) and SRAM (Static Random Access Memory) are compared.Reasons for differences are analyzed.The 14MeV neutron fluence threshold when error occurs in floating gate ROMs is higher than that in SRAM by 5 orders of magnitude,31.9MeV proton fluence threshold by 4 orders,and total dose threshold is about 104 rad(Si) for both memories.All of these are attributed to the structure of memory cells and mechanism of radiation effects.Floating gate ROMs are preferable to SRAM in application in space radiation environment when data in memory are not required to erase and write frequently.关键词：FLASH ROM;EEPROM;SRAM;single event effect;Total dose effect2|1365|9更新时间：2025-07-16
- 摘要：Based on decomposition of the minimal polynomial of a periodic sequence,we propose a new algorithm for computing the sphere complexity of the sequence.The new algorithm is applied to the sequence with special period.关键词：stream cipher;periodic sequence;linear complexity;sphere complexity2|872|1更新时间：2025-07-16
- 摘要：Conditional access system is the crucial part of Pay-TV System,and the efficiency and security of key distribution are the main factors which influence the performance of conditional access system.In this paper we proposed a new key distribution scheme on the basis of grouping users with their probability,and prove that this scheme has optimal distribution efficiency.关键词：conditional access;pay-TV;key distribution;Huffman tree2|851|1更新时间：2025-07-16
- 摘要：Construction and numeration of 1st-order correlation-immune functions were studied.A new method to construct the 1st-order correlation-immune functions was proposed,through which a number of 1st-order correlation-immune functions were got and the best lower bound of 1st-order correlation-immune functions so far was gained.The lower bound is at least (22<em>n-1+2n)/(2n+8-210) more than the present.关键词：Boolean function;correlation-immune functions;column-balanced matrix2|1311|2更新时间：2025-07-16
- 摘要：The mobile IP protocol based on RFC2002 can solve the problem that TCP/IP can't support a node roaming among subnets,only if the mobile node has the ability to modify its route table dynamically.While in practice,many typical operating systems such as Windows9x/Me etc.can't satisfy the above conditions,which restricts the utilization and the generalization of nobile IPseriously.So a new protocal——named active ARP(AARP) protocol,and the mobile IPalgorithm based on it have been proposed in this paper.Experiments and the analysis show that the protocol can be implemented on WIN platform easily and can be used by users more expediently with the performance not being deteriorated,which overcomes the disadvantage of the classical mobile IP algorithm that is hard to implement on Windows and extends the application field of mobile IPgreatly.Further more,the protocol can apply not only to windows but also to other operating systems.关键词：mobile IP;ARP;routing2|886|0更新时间：2025-07-16
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