2006 Vol.24

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A Family of Full Transmit Diversity Space-Time Codes LIU Chen;LI Yue-hong;WU Zhen-yang Journal of Applied Sciences    2006, 24 (1): 1-0001.   Abstract （2404）            Knowledge map    Save A new family of space-time block codes is constructed, called diagonal block orthogonal algebraic space-time (DBOAST) block codes. It can transmit at a normalized rate of 1 symbol per channel use. It is proved that they can achieve the full transmit diversity with a larger coding gain than DAST block codes over quasi-static or fast fading channels. The capacity of an equivalent channel using the proposed code is analyzed. The performance merit of DBOAST block codes is confirmed by Monte Carlo simulations and compared with other space-time block codes. Related Articles | Metrics | Comments（0）

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A Decision-Feedback LSCM Beam-Forming Algorithm Based on Pre-despreading FU Hong-liang;FENG Guang-zeng Journal of Applied Sciences    2006, 24 (1): 6-0006.   Abstract （2076）            Knowledge map    Save A new Least Squares Constant Modulus beam-forming Algorithm based on decision-Feedback using the pre-Despreading signals (D-LSCMAFB) in DS-CDMA system is proposed in this paper. This algorithm is simulated and compared with SDCMA and DRLSCMA in additive white Gaussian channel and multipath fading channel environments. Simulation results show that the proposed D-LSCMAFB algorithm is superior to SDCMA and DRLSCMA. Related Articles | Metrics | Comments（0）

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Analysis and Improvement of the Backoff Mechanism Used in IEEE 802.11 DCF CHEN Yu-Zhong Journal of Applied Sciences    2006, 24 (1): 10-0010.   Abstract （2213）            Knowledge map    Save IEEE802.11 is the most popular WLAN standard based on CSMA/CA. The primary Medium Access Control (MAC) protocol of IEEE802.11 is the contention-based distributed coordination function (DCF) which adopts uniform distribution for backoff process. In this paper, a Markov model is introduced to analyze the impact of backoff time distribution on system performance of IEEE802.11 DCF.A simple and effective mechanism for backoff time distribution is the proposed. Simulation result proves that this mechanism can effectively improve saturation throughput . Related Articles | Metrics | Comments（0）

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Hierarchical Reduction Algorithm of Huge Information System LIANG Hong-li;ZHANG Hua-guang;LI Ming;LIU Jin-hai FENG Jian Journal of Applied Sciences    2006, 24 (1): 15-0015.   Abstract （2409）            Knowledge map    Save A hierarchical reduction algorithm is proposed to reduce a huge information system. Based on detailed studies on the certain increment operator, a series of theorems are derived, which form a theoretic basis for the hierarchical reduction algorithm. The hierarchical reduction algorithms are then presented for both the information system with and without core attributes. Validity of the algorithms is shown with an example. Related Articles | Metrics | Comments（0）

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Adaptive Echo Cancellation Based on Decorrelation NLMS Algorithm WANG Zhen-li;ZhANG Xiong-wei;YANG Ji-bin;HAN Yan－ming Journal of Applied Sciences    2006, 24 (1): 21-0021.   Abstract （2315）            Knowledge map    Save Based on NLMS, this paper proposes a decorrelation NLMS algorithm (DC-NLMS) by employing auto-correlation of the input speech signal. The proposed algorithm has fast convergence speed, but small stability maladjustment with the same computational complexity as NLMS, therefore overcomes the drawback of APA. Simulation results indicate that the DC-NLMS algorithm is optimal in adaptive echo cancellation as compared with NLMS, APA, and a previously developed algorithm in the literature. Related Articles | Metrics | Comments（0）

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A New Smooth Handoff Mechanism with Tunnel for Wireless Local Area Network LI Wei-zheng;HU Ai-qun Journal of Applied Sciences    2006, 24 (1): 25-0025.   Abstract （2360）            Knowledge map    Save Based upon post-registration handoff mechanism in low latency mobile IPv4 and mobile agent buffer technology, a smooth handoff mechanism with bi-directional edge tunnel is presented for IEEE 802.11 wireless LAN. Combined with the proposed methods for reducing handoff latency at link layer and network layer, this mechanism reduces link layer triggers. This is not feasible in 802.11 wireless LAN. By realizing smooth handoff, handoff latency is reduced, and seamless handoff is more closely approached. Simulation experiments indicate that the mechanism not only reduces the possibility of packet loss in the process of handoff, but also lowers handoff latency by more than 500ms in average. The throughput of TCP is increased approximately by 70%. Therefore the handoff performance of wireless LAN is considerably improved. Related Articles | Metrics | Comments（0）

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Modeling Optimal Clustering Based on Continuous Hopfield Neural Network WANG Mao-zhi;GUO Ke;XU Wen-xi;FAN An-dong Journal of Applied Sciences    2006, 24 (1): 31-0031.   Abstract （2558）            Knowledge map    Save Clustering is a combinational optimal calculation based on its mathematical description. A model combined with continuous Hopfield neural network and used to solve optimal clustering is designed and constructed based on Hopfield’s optimal ability. Details of network mapping, energy function construction and nerve state changing equation are described. Their simplified formation is presented according to the winner-tale-all competitive mechanism. Convergence of the model is proved. Effectiveness and rationality of the model is verified in an application to image compression coding. Related Articles | Metrics | Comments（0）

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Traffic Pattern Based Scalability Analysis of Hybrid Routing Protocol in Mobile Ad Hoc Network YANG Pan-Long;TIAN Chang;ZHANG Lei Journal of Applied Sciences    2006, 24 (1): 36-0036.   Abstract （2248）            Knowledge map    Save According to the routing protocol scalability evaluation standard proposed by MANET research group, the acalability evaluation of routing protocol based on real network traffic pattern is analytically performed. With the mathematic modeling procedure, the analytical results of hybrid routing mechanism of FSR and DSR show that hybrid routing is a fast convergent, routing message stable and adaptive protocol. It is suitable for applications in complicated network scenarios with varying network parameter. Related Articles | Metrics | Comments（0）

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Indirect Adaptive Fuzzy Tracking Control for MIMO Nonlinear Systems DU Zhen-bin;HU Shou-song Journal of Applied Sciences    2006, 24 (1): 41-0041.   Abstract （2596）            Knowledge map    Save Combining the adaptive fuzzy control with the adaptive fuzzy identification, this paper presents an indirect adaptive fuzzy control scheme for MIMO nonlinear systems. By using the tracking error and the identification error, the parameter adjusting laws are derived. Both errors improve the performance of the system by regulating the parameters. Extended fuzzy logic systems are used to estimate the multidimensional unknown functions, and the compensator eliminates fuzzy approximation errors and external disturbances. The control scheme guarantees the system stability and attains tracking. Simulation results demonstrate that the control scheme is effective. Related Articles | Metrics | Comments（0）

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Queuing Network Based Model for Bus Buffer Estimation WU Xu-fan;YANG Jun Journal of Applied Sciences    2006, 24 (1): 45-0045.   Abstract （2012）            Knowledge map    Save A method based on a priority-ranked queuing network model for bus buffer estimation is proposed from the characteristics of the embedded microprocessor structure. By summarizing the system, a queuing network model of bus buffer is built. Detailed step of estimating is then presented. Results are analyzed, and an example constructed based on a real application. Comparing the results with high-level model simulation, validity of the method is proved. Related Articles | Metrics | Comments（0）

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Vision Terrain Evaluation Function for Virtual Cockpit TAN Hao;SONG Yan-yan;WANG Jin-yan;SHEN Chun-lin Journal of Applied Sciences    2006, 24 (1): 50-0050.   Abstract （1598）            Knowledge map    Save Methods for analyzing dynamic multi-resolution terrain models for virtual cockpit systems are discussed. A new model based on the human vision characteristics is presented in order to make better display for terrain rendering, taking into consideration the models of retina gaze and eye motion. It is focused to simplify the 3D engine to avoid complex bio-characteristic of human eyes. The final vision terrain evaluation functions are quite simply with little additional computation cost. Experimental results show the effectiveness of the proposed algorithm. Related Articles | Metrics | Comments（0）

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Design of an Improved Current Summing Reference ZHANG Yao-zhong;WU Jian-hui;DING Jia-ping;LONG Shan-li Journal of Applied Sciences    2006, 24 (1): 50-0050.   Abstract （1927）            Knowledge map    Save A CMOS band-gap current summing reference is designed, which is self-biasd with a cascode structure. Hspice simulation with a Chart CMOS 0.35μm and 5V power supply shows that, within ?40?C ~ +85?C, the temperature coefficient is 15.2ppm/?C, and the power supply restrain ratio is ?51.8dB. Related Articles | Metrics | Comments（0）

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Discovery of High Dimensional Outliers Based on Association Analysis LU Jie-ping;NI Wei-wei;SUN Zhi-hui Journal of Applied Sciences    2006, 24 (1): 60-0060.   Abstract （1999）            Knowledge map    Save Discovery of outliers is to extract a few data objects with abnormal behavior patterns, which are more interesting than common patterns in some cases, from a large amount of data. It is of practical significance in IDS, credit fraud detection, etc. Data in these domains are usually high dimensional, particularly featured by their sparseness and decline properties. An algorithm that can obtain the outliers with high efficiency is proposed based on association analysis. Effectiveness of the algorithm is shown by theory analysis and experiment results. Related Articles | Metrics | Comments（0）

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Algorithm for Mining Constrained Maximum Frequent Itemsets Based on Frequent Pattern Tree CHEN Geng;ZHU Yu-Quan;SONG Yu-Qing;LU Jie-Ping;SUN Zhi-Hui Journal of Applied Sciences    2006, 24 (1): 64-0064.   Abstract （2180）            Knowledge map    Save Most algorithms of frequent itemsets (or maximum frequent itemsets) do not consider any domain knowledge. As a result they generate many irrelevant patterns. Therefore, finding constrained maximum frequent itemsets is a key in important data mining application such as discovery of constrained association rules, constrained strong rules, etc. Little work has been done on this problem. This paper presents an effective algorithm for mining constrained maximum frequent itemsets and its update, UCMFIA, based on a novel frequent pattern tree (FP-tree) structure that is an extended prefix-tree structure for storing compressed and crucial information about frequent patterns. Experiments show that the algorithm is effective. Related Articles | Metrics | Comments（0）

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Statistical Analysis of Linear Mixed Model for Longitudinal Data SUN Yan;CHAI Gen-xiang Journal of Applied Sciences    2006, 24 (1): 70-0070.   Abstract （2193）            Knowledge map    Save The linear mixed model for longitudinal data proposed by Laird and Ware is studied.Estimators of the random effects, regression coeddicients and error variance are established without assuming any distributions of random effects and random errors.Strong consistency and ssymptotic normality are discussed under the general conditions of design points and moments. Related Articles | Metrics | Comments（0）

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Identities and Recursive Algorithm of Function-Valued Padé-Type Approximation for Solution to Integral Equations Pan Baozheng Journal of Applied Sciences    2006, 24 (1): 74-0074.   Abstract （2328）            Knowledge map    Save To solve Fredholm integral equations of the second kind, a generalized linear functional was introduced and then function-valued Padé-type approximation was defined. Some useful identities are established by means of error formulas for function-valued Padé-type approximation. A recursive algorithm is also constructed. An example is given to show effectiveness of this method. Related Articles | Metrics | Comments（0）

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Effect of System Parameters on Dynamic Stability of DWX Single Hydraulic Prop WANG Zhong-min;CHEN Shi-qi;LI Bing-wen Journal of Applied Sciences    2006, 24 (1): 78-0078.   Abstract （1946）            Knowledge map    Save A dynamic model of DWX single hydraulic prop is established. Differential equations of motion for each part of the hydraulic prop are derived based on the Hamilton principle. Using the finite difference method and by discretization of spatial variables, differential equations with only time variable are obtained. By introducing state vector, the first order state equations with periodic coefficients is solved by the implicit second class fourth order Runge-Kutta method. Based on the Floquet theory, the principal dynamic instability regions and dynamic stability regions for the hydraulic prop are determined. As an example of DWX35 single hydraulic prop with a cylinder of 100mm diameter, effects of the system parameters on dynamic stability of the hydraulic prop are discussed. Related Articles | Metrics | Comments（0）

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Adaptive Nonlinear Design of Autopilot for Ship Course Tracking DU Jia-lu;GUO Chen;YANG Cheng-en Journal of Applied Sciences    2006, 24 (1): 83-0083.   Abstract （2316）            Knowledge map    Save An adaptive nonlinear control algorithm combined with an adaptive backstepping algorithm using the Nussbaum gain technique is proposed for ship course tracking steering, which takes into account rudder characteristics and parameter uncertainty. With the proposed algorithm, a ship course-tracking autopilot is designed without any a priori knowledge about virtual control coefficient. Based on the Lyapunov function, it is proved in theory that the controller makes all signals in the nonlinear system of unmacthed uncertain ship motion uniformly bounded, and the desired reference course is asymptotically tracked by the ship’s actual heading. Performance is demonstrated in a series of simulation studied. Related Articles | Metrics | Comments（0）

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Decision-Making for Air Combat Dogfight LUO De-lin;SHEN Chun-lin;WU Wen-hai;WU Shun-xiang Journal of Applied Sciences    2006, 24 (1): 89-0089.   Abstract （2095）            Knowledge map    Save Considering a scenario of air combat involving two opposing fighter aircrafts, a decision-making model for the pilot in air combat is established. The model is based on a situation of continually updated threat. An influence diagram analysis method is employed to describe the pilot decision-making process. Evaluation of air combat threat and the decision-making behavior are easy to describe and modify, if necessary, according to the experience and preference of the individual pilot. Simulation results show that the proposed model is effective to guide the fighter aircraft during air combat dogfight, and its decision-making process conforms to the concept of air combat dogfight. Related Articles | Metrics | Comments（0）

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Principle and Parameter Design of Hybrid Magnetic Axial Bearings JIA Hong-yun;ZHU Huang-qiu Journal of Applied Sciences    2006, 24 (1): 94-0094.   Abstract （2294）            Knowledge map    Save Based on configuration and operation of hybrid magnetic bearings used in an axial direction, the principle of suspension force generation is studied. The flux path is calculated by using an equivalent magnetic circuit. The equation of attraction is derived. Mathematic expressions of force/displacement coefficient, force/current coefficient and the maximum bearing capacity are obtained. A set of design and calculation methods are given, such as those for gap magnetic induction intension, pole area, gas length, electromagnet iron parameters, and permanent magnet parameters, providing reference to applications. Related Articles | Metrics | Comments（0）

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Analysis of Repeatedly Available Thermal Energy in Engines ZI Kun;LAN Xu-guang YANG Xiu-qi Journal of Applied Sciences    2006, 24 (1): 99-0099.   Abstract （1925）            Knowledge map    Save To further improve thermal efficiency of internal combustion engine, analysis of energy utilization in engine dynamical cycles is needed. Analysis of available energy can estimate the energy utilization in dynamical cycles of engine in terms of quality. Based on a model of finite time thermodynamics in the engine operation, loss of the available energy is analyzed. The results obtained are in good agreement with that in the actual engine operation. Related Articles | Metrics | Comments（0）

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A Novel Cooling System for Direct Methanol Fuel Cell Stacks WANG Jiang;SHI Ming-heng;CHEN Zhi Journal of Applied Sciences    2006, 24 (1): 103-0103.   Abstract （1946）            Knowledge map    Save A theoretical analysis is carried out for the effective heat management of a direct methanol fuel cell. Based on the requirement of heat management, a novel cooling system with fractal network channels is designed for the direct methanol fuel cell stacks. Optimum structural parameters of the fractal network channels are calculated, and the effect of flux of cooling water and heat load on the temperature distribution in the stacks quantitatively analyzed. The results can be applied to determine the optimal flux of cooling water and to optimize the stack design. Related Articles | Metrics | Comments（0）

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Application of Wavelet Transformation to Dynamic Measurement of Men-Board System WANG Jun WANG Feng－quan;Li Zhi－jun;ZHOU Xing－de Journal of Applied Sciences    2006, 24 (1): 108-0108.   Abstract （2273）            Knowledge map    Save In order to acquire the starting condition of a springboard diver from the response curve, discrete wavelet transform is used to decompose the signal. A correlation algorithm based on time-frequency analysis is improved to estimate only the low frequency relative coefficients of similar signals which contains most energy. The moment of take-off can be caught, and the jumping acceleration and velocity are obtained. Moreover, shock spectrum of the board is figured out to obtain optimum pressing condition. Experimental results indicate that the method can be used to evaluate the jumping skill, which is useful in the training. Related Articles | Metrics | Comments（0）

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Serial Circuit Architecture for Power-Sum in GF(2m) YUAN Dan-shou, RONG Meng-tian, LI Xin-tian Journal of Applied Sciences    2006, 24 (2): 111-114.   Abstract （396）      PDF（pc） （186KB）（127）       Knowledge map    Save An iterative algorithm for computing power-sum in GF (2m) is proposed using polynomial basis.During each iteration step, one bit-vector polynomial multiplication and reduction modulo of irreducible polynomial are computed. Based on this algorithm, a new serial power-sum circuit architecture is designed, with area complexity of O(m), and throughput of one result per m clock cycle.Compared with existing power-sum architectures, the proposed method has small area complexity, thus well is suited to VLSI design of applications with small chip area requirements.The powersum architecture can be used to compute exponentiations and squares. Related Articles | Metrics | Comments（0）

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Data Hiding in Text File Using TeX and Extraction of Hidden Data from Document Image CHEN Chao, WANG Shuo-zhong, ZHANG Xin-peng Journal of Applied Sciences    2006, 24 (2): 115-119.   Abstract （429）      PDF（pc） （261KB）（92）       Knowledge map    Save A steganographic technique using pdf files to carry secret data is proposed.Data are embedded into the control sequences in a TeX source file to slightly modify inter-word spaces in the text.Appropriate coding schemes may be applied.The coded TeX file is then compiled and converted to generate a stego-pdf file, which is convenient to be disseminated over the Internet.In reception, jpg images are obtained from the pdf document, and the hidden data are extracted by detecting the spaces between words.Data security is determined by the ability of reliably detecting small difference in space widths, size of the document file in terms of the amount of data to be embedded, and the encryption and coding techniques used. Related Articles | Metrics | Comments（0）

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Federal Filtering Algorithm in SINS/Beidou/STAR Integrated Navigation System HUA Bing, LIU Jian-ye, XIONG Zhi, ZHU Yan-hua Journal of Applied Sciences    2006, 24 (2): 120-124.   Abstract （472）      PDF（pc） （230KB）（101）       Knowledge map    Save Beidou satellite navigation location system is China's first generation satellite navigation system.The star sensor is a high precision attitude-measuring instrument.On the basis of non-feedback federal filtering, Beidou navigation lo cation system and the star sensor are used together in an integrated navigation system in order to set up the SINS/Beidou/star integrated navigation system.From the characteristics of Beidou and the star sensor, causes of delay and asynchronous problem in the instrumentation are analyzed, and a solution is proposed.Simulation shows that this integrated navigation system has high precision and good tolerance to faults.This shows application potentials for the Beidou system in defense industries. Related Articles | Metrics | Comments（0） Cited: Baidu(6)

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Reliability Description of Fault Detection and Optimization Algorithm of Sensor Location YANG Fan, XIAO De-yun Journal of Applied Sciences    2006, 24 (2): 125-130.   Abstract （418）      PDF（pc） （303KB）（75）       Knowledge map    Save Reliability problems in fault detection for large-scale complicated systems are studied by using a probabilistic signed directed graph (SDG) model.Influences of sensor selection and location on reliability with respect to different sensor fault probabilities are analyzed.When system faults occur, the sensors can detect the departure of variances, but the system faults may be ignored or misdiagnosed because of the sensor faults, directly affecting the fault detection reliability. With description of the probabilistic SDG model, the reliability description of fault detection is given.Optimal sensor lo cation and the corresponding algorithm are studied under restricted resources.Furthermore, a probabilistic SDG model is established for a typical 65 t/h boiler, on which the above algorithm is executed to determine an optimization scheme. Simulation experiment shows that sensor location solved in this way is effective in improving fault detection reliability. Related Articles | Metrics | Comments（0） Cited: Baidu(12)

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Laser Frequency Repetition Times in Portable Aerial Target Measurement MA Jian-wei, LI Peng, SHENG An-dong, GUO Zhi Journal of Applied Sciences    2006, 24 (2): 131-134.   Abstract （397）      PDF（pc） （214KB）（63）       Knowledge map    Save The problem of laser frequency repetition (LFR) times in target distance measurement is studied.In analyzing flight path data, power spectral density is computed to obtain the frequency range and times of LFR using the Shannon theorem.Under the assumption of line movement with constant velocity, the flight path is built such that prediction error variance computed by the LFR times meets the specified requirements.Relation between error variance and the maximum allowed number of missing measurements is presented.It is proved both in theory and from practice that the LFR times can meet the performance specifications of laser echo rate while guaranteeing the tracking precision. Related Articles | Metrics | Comments（0）

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A New Character-Localization Method in Wavelet Transform Domain ZHANG Er-hu, ZHANG Xu-jin, ZHANG Zhi-gang Journal of Applied Sciences    2006, 24 (2): 135-139.   Abstract （361）      PDF（pc） （271KB）（91）       Knowledge map    Save Characters in an image often provide important information of the image.Extraction of characterregions enables one to quickly browse and retrieve specific images.Based on analysis of the property of characters and study of their features in the wavelet transform domain, a new method for localizing and extracting characters is proposed.By using an adaptive dynamic threshold together with information of the adjacent blocks, the rate of correct-detection may be raised.A special feature of the method is that only partial decoding is required for encoded images involving wavelets such as JPEG2000 and MPEG4. Experimental results show that the processing is fast and correct-localization rate is high. Related Articles | Metrics | Comments（0） Cited: Baidu(3)

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Kernel Canonical Correlation Analysis and Application for Face Discrimination HE Yun-hui, ZHAO Li, ZOU Cai-rong Journal of Applied Sciences    2006, 24 (2): 140-144.   Abstract （408）      PDF（pc） （225KB）（145）       Knowledge map    Save Based on the equivalence between canonical correlation analysis (CCA) and Fisher linear discriminant analysis (FLDA), nonlinear discriminant features of face images are extracted with kernel CCA.These features are equivalent to those extracted with KFDA.Experimental results demonstrate that KCCA is similar to GDA and significantly better than FLDA. Related Articles | Metrics | Comments（0） Cited: Baidu(15)

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A Stable Mobile ad hoc Network Routing Algorithm with Gray Prediction YANG Pan-long, TIAN Chang, NI Ming-fang Journal of Applied Sciences    2006, 24 (2): 145-149.   Abstract （396）      PDF（pc） （299KB）（79）       Knowledge map    Save Due to the highly dynamic topology and complicated network scenario, stability is a key factor in ad hoc routing protocol efficiency.In this paper, the gray theory is applied to topology state prediction in mobile wireless ad hoc network in order to improve the proactive ability of reactive routing protocol such as DSR.In the developed routing protocol, a number of factors are taken into account to avoid turbulence of routing information in network, minimize unnecessary routing overhead, rapidly find disabled links and improve stability of routing information.Simulation results show that the stable routing protocol S-DSR based on the gray prediction theory is considerably more stable and efficient than that of the original one. Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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A New Design Method in CMOS Analog Cell Circuit Optimization ZHENG Wei-shan, PENG Yi-pin, ZHANG Men, WU Jian-hui Journal of Applied Sciences    2006, 24 (2): 150-153.   Abstract （413）      PDF（pc） （190KB）（81）       Knowledge map    Save This paper proposes a new method for sizing and optimizing CMOS cell circuit.The core algorithm is the niche-based genetic algorithm.The simulated result shows that the difference between the optimized circuit's performances obtained using the proposed method and that using the simulation-based method is not obvious, while the proposed method takes much less time. Related Articles | Metrics | Comments（0） Cited: Baidu(5)

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Application of Buffer Operator and Data Fusion in Target Tracking LIU Yi-an, CHEN Song-can, ZHANG Ming-jun, MA Xiu-fang Journal of Applied Sciences    2006, 24 (2): 154-158.   Abstract （387）      PDF（pc） （220KB）（97）       Knowledge map    Save Aiming at multi-radar target tracking in a complicated environment, this paper introduces a buffer operator of the gray system theory into a multi-radar target tracking scenario, and improves the primitive shock disturbed sequence to attenuate its randomness.Data fusion techniques are then applied to further improve tracking precision of the radar system for the random oscillatory sequence due to the buffer operator.Simulation results indicate that the method is effective and feasible. Related Articles | Metrics | Comments（0） Cited: Baidu(12)

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DMVR: A Dynamic Materialized View Replacement Algorithm Based on Disk Cache Mechanism ZHANG Bai-li, SUN Zhi-hui, ZHOU Xiao-yun, ZHANG Jing Journal of Applied Sciences    2006, 24 (2): 159-164.   Abstract （468）      PDF（pc） （255KB）（91）       Knowledge map    Save The current dynamic materialized view selection algorithms based on disk cache can tune with the altering query requirements and possess better dynamic adaptability.However these algorithms simply refer to the memory mechanism, whithout an accurate model to take into account the cost of retrieving materialized views from disk.A dynamic materialized view replacement (DMVR) algorithm is presented, which is based on a better cost model and therefore suitable for dynamically adjusting the materialized view set.For systems with a heavy workload, that DMVR algorithm is modified to become DMVR-IDLE, which possesses and maintains a better response performance to high frequency query.Experiments have shown effectiveness of both algorithms. Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Saturation Throughput and Delay Analysis of DCF in IEEE 802.11a WLAN CHEN Yu-zhong, YANG Bing-qing, KAI Cai-hong, LIU Zheng-kai Journal of Applied Sciences    2006, 24 (2): 165-170.   Abstract （359）      PDF（pc） （274KB）（88）       Knowledge map    Save IEEE 802.11a is a popular high-speed WLAN standard with a data rate up to 54 Mps.The basic Medium Access Control (MAC) protocol of IEEE 802.11a is the contention-based distributed coordination function.DCF includes two access mechanisms:basic access mechanism and RTS/CTS access mechanism.In this paper, an analysis and comparison of saturation throughput and access delay of these two access mechanisms in IEEE 802.11a WLAN is conducted by introducing a two-dimensional Markov model.The study reveals that, in contradiction to the situation in IEEE 802.11 WLAN, basic access mechanism is always more effective than RTS/CTS mechanism in high-speed IEEE 802.11a WLAN. Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Optimization of Disposition Actuators in High Level Multiple Degree of Freedom Structures Based on Fuzzy-Genetic Algorithm CAO Yuan, WANG Feng-quan Journal of Applied Sciences    2006, 24 (2): 171-175.   Abstract （420）      PDF（pc） （212KB）（88）       Knowledge map    Save Optimization of actuator disposition in high level multiple degree of freedom structures is an important problem.A fuzzy algorithm, with which full use of a priori information can made, has been applied.Using this algorithm, optimization of disposition actuators is confined to a limited range, and subsequent calculations are easy and fast.The genetic algorithm has been used in the optimization, ensuring a good performance. Related Articles | Metrics | Comments（0） Cited: Baidu(7)

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Gaussian Approximation of Irregular Repeat-Accumulate Codes over Mixed Gaussian/Erasure Channels GAO Hong-feng, XU Zong-ze Journal of Applied Sciences    2006, 24 (2): 176-180.   Abstract （391）      PDF（pc） （243KB）（98）       Knowledge map    Save Gaussian approximation models the message density in message passing decoders as Gaussian distribution.In this paper, irregular repeat accumulate (IRA) codes over the mixed white Gaussian noise/erasure channels are designed using Gaussian approximation.Recursive equations of density evolution and analytic expressions of bit error rate are derived.The analytic results not only provide a way to predict asymptotic performance of IRA codes but also help us design good IRA codes over the mixed channel.Comparison between simulation results and thresholds computed from analytic results shows that predication from the theoretical results is accurate enough.The optimized IRA codes designed for the mixed channels have better performance than that of IRA codes designed for AWGN channels when the designed erasure probability is close to the actual probability. Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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Quadratic Guaranteed Cost Control of a Class of Uncertain Discrete Time Delay Switched Systems SUN Wen-an, SHEN Lian-shan, ZOU Kai-qi, LI Pi-xian Journal of Applied Sciences    2006, 24 (2): 181-186.   Abstract （365）      PDF（pc） （244KB）（75）       Knowledge map    Save For a class of discrete-time state delay switched systems with norm-bounded time-varying parameter uncertainty, this paper addresses the problem of designing the guaranteed cost state feedback controller of quadratic stabilization under arbitrary switching laws.A condition for the existence of guaranteed cost controllers is derived.This condition can be solved easily with the MATLAB LMI toolbox.A numerical example shows the effectiveness of the method. Related Articles | Metrics | Comments（0） Cited: Baidu(3)

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Approximate String Match of Special Points in Signatures and Random Forgery Elimination QUAN Zhong-hua, HUANG De-shuang, ZHANG Guang-zheng Journal of Applied Sciences    2006, 24 (2): 187-192.   Abstract （384）      PDF（pc） （282KB）（82）       Knowledge map    Save For on-line signature verification, extraction and matching of special points is one of the most important problems.Because the special points can be regarded as features, and used as references in segmentation and alignment. This paper proposed an approach based on approximate string match to match the sequence of special points.By calculating the edit distance between strings consisting of the types of special points, this method can quickly detect random forgeries.This can improve the speed of the system. Related Articles | Metrics | Comments（0）

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Energy Oriented Optimization of Allocation Strategy for On-Chip Memory JIN Jing, PU Han-lai, LING Ming Journal of Applied Sciences    2006, 24 (2): 193-198.   Abstract （437）      PDF（pc） （270KB）（109）       Knowledge map    Save In this paper, an allocation strategy for on-chip memory is proposed to optimize energy of memory system. With data, global variable, instruction and branch instruction, the strategy uses ECFG to get the effect of energy and capacity caused by the object relationship.By using refined knapsack arithmetic with ILP, experiment results are obtained showing that, for most applications, general energy consumption of a memory system decreases by up to 50%. Especially, when an application's capacity approaches the content of SPM content, this figure is higher than 95%. Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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