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2009 Vol. 35, No. 9

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Thermal performance analysis of antigravity suit
Qiu Yifen, Li Yanjie, Ren Zhaosheng
2009, 35(9): 1035-1038.
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To study the thermal performance of an antigravity suit, the thermal system simulation modal was build among human body, antigravity suit and environment. The suit was divided into 15 segments, each segment has different thermal resistance and gas permeability. The system heat and mass transfer process were analyzed according to suit characteristic. This modal can simulate human body skin temperature, core temperature and sweat. The combined index of heat stress(CIHS) was calculated with these parameter to evaluating human body hot load. Experiments were designated to validate the modal calculation results. The differences between experimental and calculating results is small. At last, influences of the suit thermal resistance and impermeability index to body hot load ware analyzed with the modal built above.
Ammonium dinitramide (ADN) combustion model with detailed gas phase reactions
Duan Yi, Liu Yu
2009, 35(9): 1039-1042.
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A numerical calculation model with detailed gas phase reactions was developed to study the physical and chemical processes involved in ammonium dinitramide(ADN) combustion. The model was based on the conservation equations of mass, species concentration and energy, and takes into account finite-rate chemical kinetics. At last, the equation of state for a multicomponent system was employed to close the equations. A chemical kinetics scheme, containing totally 34 species and 165 reactions, was established and employed in the model. The model was applied to predict species mole fractions and temperature profiles in ADN gas phase flame at 0.3MPa. The agreements between calculation results and experimental data are very well. The results show that the model can predict ADN gas phase combustion wave accurately.
Affine invariant based on determinant points in object recognition
Wu Gaojie, Li Chao, Xiong Zhang
2009, 35(9): 1043-1047.
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The common affine invariants were very sensitive to the edge of the image, so a new method entitled "an affine variant based on the determinant points in image recognition" was proposed. First the centroid of the separated object image was computed, and then many line segments were derived through the centroid, at the end the nearest extreme grayscale points were found on every line. In order to compute the affine invariants, the extreme points were used to build up a collection of determinant points. The affine invariants of the collection could be served as an input vector of the trained neural networks to distinguish whether the source image was the destination image. The method was applied to the plane recognition and was proved to keep highly stable even if the object contour was ill-segmented or noisy. It is much easier and effective compared with the traditional methods and has a very wide scope of application.
Software defined GNSS reflections receiver design
Yang Dongkai, Ding Wenrui, Zhang Qishan
2009, 35(9): 1048-1051.
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The characteristics of navigation satellite reflected signal was analyzed. Both the architecture and the components for GNSS (global navigation satellite system) reflections receiver were presented including the two antennas, two RF (radio frequency) front ends, two high speed A/D converter and the computer for data processing. The basic reflections processing workflow was elaborated on, where C/A code generation for the reflected signal was mainly discussed following the correlation power computation with one simulation example. The software was designed and its detailed flowchart, key parameters and functions definition, user interface were also proposed. Field test data were feed into the designed software receiver, and the displayed result show that the receiver runs stably. And it can give correlation power with user defined different parameters.
Application of PH curve in CNC look-ahead function
Wang Qikui, Li Wei, Chen Youdong, Wang Tianmiao
2009, 35(9): 1052-1056.
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A new method was developed to smooth the micro-line while machining in computer numerical control systems. Four rules including angle between transfer vectors with speed limitation, length and angle between the micro-lines with accuracy limitation and the monotonicity of the point were proposed to divide segments into some areas. Nonlinear least squares method was introduced to fit the lines into PH curves. Simulated annealing algorithm was used to adjust the tangent vector for getting better accuracy. The model of adjustment included both unidirectional and bidirectional adjustments by the situation of the point between the areas. Straight slope was considered as the initial value of the tangent vector in the simulated annealing algorithm. Chord error was computed by segmenting the micro-line, the error was the objective function to determine the adjustment of the vector. The results illustrate the dividing rules improve the fitting efficiency. Smooth curves with high accuracy were obtained to get better velocity profile.
Learning drifting user interest incrementally from numerically labeled feedbacks
Zhang Pin, Pu Juhua, Liu Yongli, Xiong Zhang
2009, 35(9): 1057-1061.
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Most incremental approaches for learning drifting user interests assume that data instances in user feedbacks are binary labeled. A novel incremental learning approach was presented which learns drifting user interests from numerically labeled feedbacks instead of binary labeled ones. User interests were modeled as a set of probabilistic concepts. Numerical instance labels were considered as probabilities that the user likes those instances. Feedbacks were used to update user interest models incrementally based on an exponential, recency-weighted average algorithm. Experimental results on different learning tasks showed that the approach outperforms existing approaches in numerically labeled feedback environment.
Exact linearization based modeling and control for electro-hydraulic compound regulating integrated actuator
Lang Yan, Li Yunhua
2009, 35(9): 1062-1066.
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A new designed total pressure control valve,which can keep the sum of high and low pressures of actuating cylinder be a constant and also make the two chambers pressures be controllable,was added to the classic pump controlled electro-hydraulic actuator(EHA)to enhance its natural frequency. This improved EHA is called electro-hydraulic compound regulating integrated actuator(EHCA) which has the same response frequency with valve controlled actuator. For the multiplicative nonlinear problem of system flow, the principle of EHCA and the total pressure control valve operation scheme was analyzed,and exact linearization based modeling and controller design were implemented. The best matching of motor speed and pump displacement regulation in the different working conditions was discussed. Analysis and simulation show that,exact linearization based on EHCA sliding mode control concept achieves the control purposes of high efficiency,energy saving and faster response for dual-variable compound regulation.
Signature on conic curve over Zn based on two hard problems
Lin Song, Li Zhoujun, Wang Biao
2009, 35(9): 1067-1071.
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The security of the digital signature scheme (Xiao06 scheme) on conic curve Cn(a,b) over the residue class ring Zn was analyzed. The analysis result indicates that the published parameters can make the modulus n be factorized using the Weda-s theorem, and shows that the Xiao06 scheme is not a scheme whose security based on the integer factorization problem. To address this issue, an improved digital signature scheme on conic curve over Zn was proposed. Some parameters were kept secretly, and the verification algorithm was modified in the improved scheme. Furthermore, the numerical simulation of the improved scheme was given. The analysis shows that the improved scheme is a digital signature scheme based on two hard problems in computing discrete logarithm and factorizing integer simultaneously, and that the improved scheme has not only the merits (convenience for plaintext embedding, quickness for the inverse operation, and easiness for element order and points computing in curve) of the Xiao06 scheme, but also the advantage of strong anti-cracking ability.
Lake height variation measurement utilizing GNSS reflected signal carrier phase
Yao Yanxin, Yang Dongkai, Zhang Qishan
2009, 35(9): 1072-1075.
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A lake height variation measurement method utilizing global navigation satellite system(GNSS) reflected signal carrier phase was given. Carrier phase observation equations were built firstly. Then the single-differences between the carrier phase observation measurements for direct and reflected signal and the double-differences between epochs were calculated. A large amount of errors was eliminated by the differencing process. Also, the geometry path differences of direct and reflected signal were derived. The lake height variation was calculated using observation measurement and elevation information from separate satellite. The weighted average of the lake height variations from various satellites was derived to improve the precision and reliability of the measuring system. Simulation confirms that the precision of millimeter order is achieved with the method under -15dB signal to noise ratio(SNR).
Finding most vital node by node importance contribution matrix in communication netwoks
Zhao Yihuan, Wang Zulin, Zheng Jing, Guo Xujing
2009, 35(9): 1076-1079.
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Node importance evaluation based on removal of nodes and their incident links may change the topology of the network, even splits the network into several disconnected parts.The neighbor nodes- node importance contribution matrix (NICM) was defined and an improved node importance evaluation method was proposed. A node-s importance value was initialized as its betweenness. Different node contributed importance value dissimilarly to a certain node, according to its degree and their position relationship. The algorithm was compared with the node-removal based method in the analysis of advanced research project agency(ARPA) net topology. The results show that this algorithm accurately represents the node importance, with less calculation workload and no change of the net topology. Nodes- ability to control the network recourse is also involved in this method.
New pairwise key predistribution scheme for wireless sensor networks
Ding Xiaoyu, Liu Jianwei, Shao Dingrong
2009, 35(9): 1080-1082.
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A new hypercube-based key predistribution scheme for establishing pairwise keys between sensor nodes using polynomials, which is parameterized by the dimension of hypercube and the Hamming distance threshold variables was developed. This scheme exhibits a nice property: when the Hamming distance between any two neighboring sensor nodes is less than the pre-defined threshold, the pairwise key can be established directly. The scheme is typical for the innovation that the Hamming distance threshold is parameterized which solves the constraint in previous schemes that any two neighboring nodes can establish pairwise key only when the Hamming distance is one. Extensive performance and security analysis shows that by increasing Hamming distance threshold value, the resilience against node capture attack for higher probability of direct pairwise key establishment can be traded off, so as to save the energy consumption which is the most important issue for sensor networks.
Moving object trajectory clustering method in intelligent surveillance video
Hao Jiuyue, Li Chao, Gao Lei, Xiong Zhang
2009, 35(9): 1083-1086.
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Trajectory analysis is the basis of scene understanding, however noise trajectories causing by barriers in true surveillance scene will influence the result veracity. A trajectory similarity measure and clustering method to segment a scene into semantic regions were proposed to eliminate the effect causing by noise. First, the trajectory was encoded, and then both the object position and its instantaneous velocity were computed by improved similarity measure method to represent the distance between two trajectories. Then, the improved hierarchical clustering algorithm which chooses the longest trajectory as each cluster representation was applied to cluster trajectories according to different spatial and velocity distributions. In each cluster, trajectories were spatially close, had similar velocities of motion, and represented one type of activity pattern. This algorithm does-t need complex pre-process or filter, and because of adding velocity direction, the scene division is more reasonable. Finally, through experiment in true scene, the results show that the method can distinguish different clusters reasonably and improve the effectiveness of clustering.
Observer-based control for a class of nonlinear networked control systems
Zhu Guizhi
2009, 35(9): 1088-1090.
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Considering the data packet dropout between sensor and controller, when some states of the object cannot be measured directly, a class of networked control systems (NCSs) with nonlinear perturbing terms in the plant was investigated. There is a network between the sensor and controller. The network was considered as a switch, which happened between sub-system when network communication was connected and sub-system when network communication was interrupted. So the NCS could be modeled as a switched system. Motivated by dwell-time idea, some sufficient conditions of exponential stability of NCS were established by Lyapunov stability theory. Utilizing the solutions of linear matrix inequalities (LMIs), the parameterized expression method of the state observer and controller was given which could ensure the NCS exponential stability. A numerical example was shown to demonstrate the efficiency of the obtained result.
Advanced spectral unmixing algorithm based on spectral information divergence
Xu Zhou, Zhao Huijie
2009, 35(9): 1091-1094.
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Spectral unmixing is a key issue of quantitative remote sensing. An advanced spectral unmixing algorithm based on per-pixel optimal endmembers selection named spectral information divergence-spectral mixed analysis (SID-SMA) was proposed. It determined the optimal endmembers subset using the criteria of SID and selected endmembers through two selection steps which could improve the precision of endmember selection and obtain small abundance estimation error. The results of simulated data from spectral library indicate that SID-SMA has better precision of endmember selection and abundance estimation. When the signal-to-noise ratio (SNR) is 100∶ 1, the correct proportion of endmember selection arrives at 99.86% and total abundance error of 29 endmembers is less than 0.1 and the speed of SID-SMA is much faster.
Method for investigation of combustion flowfield characteristics in single element gas/gas injector chamber
Wang Xiaowei, Jin Ping, Cai Guobiao
2009, 35(9): 1095-1099.
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To facilitate hot-fire tests of single element gas/gas injector chamber, a method used to reveal the combustion development and completion length of the chamber flowfield was designed, which combines wall temperature measurement and numerical simulation of gas/gas combustion flowfield. The impacts of using various turbulence and combustion models was investigated to obtain the models which best represented the experimental data. And influences of H2/O2 momentum ratio and chamber pressure on shear-coaxial injector combustion flowfield were investigated. The result shows that the better mixing and the shorter combustion length can be obtained with the larger H2/O2 momentum-ratio and the chamber pressure can hardly influences the combustion flowfield.
Modal parameter identification based on image streams under disturbance measurement environment
Li Jing, Cheng Wei
2009, 35(9): 1100-1103.
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To aim at structure modal parameter identification,a method based on a sequence of 2D images was proposed．Chose certain feature points from the object whose modal parameter need to be identified．Factorization method was employed on the image streams taken by CCD camera to solve structure from motion problem and obtain motion track of each point．Eigen-system realization algorithm (ERA) was used to identify modal parameter of structure．Especially when the measure equipment,that is CCD camera was disturbed,it can separate disturbance through image streams and get structure motion parameter,so that the identification result was ensured．A simulation model of cantilever beam under disturbed measurement environment was analyzed．It shows that the first five frequencies of the beam coordinating well with the ANSYS calculation result,which offers high significance to the dynamic characteristic identification using optic images in project programs．
Monotone restriction model of reliability growth evaluation
Liu Zhiyang, Liu Lu, Huang Min
2009, 35(9): 1104-1107.
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The test data of large complex products presents small sample characteristic in each phase during the development process normally. The restriction, the reliability of one phase is always higher than that of the previous one, was recommended to be used for reliability evaluation based on multi-phase test data. The reliability of product is increasing during the development process normally, therefore, such method has broad applicability. The reliability was considered a random variable with such restriction. The reliability probability distribution function based on the restriction was given, and an approximative calculational method was presented. An example was given to compare the result obtained from single phase test data with that based on multi-phase test data. Since the precondition is brief and the reliability probability distribution function can be achieved, the mentioned method is more applicable to practical applications in comparison with traditional army materiel system analysis activity(AMSAA)-model, and it can gain the reliability interval estimation which can not be obtained from Duane-model.
Simulation experiment on air flow and heat transfer of fight plane’s cockpit
Shen Haifeng, Yuan Xiugan
2009, 35(9): 1108-1112.
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A full-scale experiment was carried out on air flow and heat transfer of a fight plane-s cockpit. Aerothermal load and body heat load were simulated, and ATM2400 36-channel airflow and temperature instrument were used to measure velocity fields of 5 measurement planes and temperature fields of 2 measurement planes and near clothing surface. The influnce of air supply flux and the switch of nozzles was observed, and the cockpit comfort was assessed. The results show that velocity fields are asymmetry and temperature distribution on cockpit-s inside wall is unevenness, and the switch of nozzles has great effect on velocity fields, temperature fields and temperature distribution near clothing surface while has little effect on the average velocity and temperature in cockpit, and the average velocity is linear with air supply flux. Experimental results can be used for proving numerical simulation accuracy.
Ionosphere fitting method and path parameters analysis
Han Yifeng, Yan Zhaowen
2009, 35(9): 1113-1116.
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Anti-parabolic model that function as the joint layer was adopted to describe the electron density distribution between the quasi-parabolic multi-lays in ionosphere. The parameters of the anti-parabolic layer, such as critical frequency, semi thickness and the layer bottom radial distance from earth-s center, were calculated on the basis of the continuous electron density distribution and its continuous derivative. The plasma frequency calculated in the quasi-parabolic model or anti-parabolic model was substituted into Appleton-Hartree formula and Snell theorem to calculate the ray trace with the help of ray geometry in the ionosphere. The three important path parameters which are the ground range, group path and phase path were calculated on this multi-layer ionosphere model with the joint layer. The relationship between the path parameters, which is influenced by the angle of incidence and the working frequency, was analyzed. The relationship between the path parameters and the angle of incidence or the working frequency was analyzed too.
Modeling of wireless datalink communication region between two aircraft
Yu Fuzhang, Cai Zhiyong, Hu Yingqiong
2009, 35(9): 1117-1120.
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A mathematical model of communication region should be developed for realizing normal communication of two aircraft in flight. Based on the air-to-ground wireless datalink communication, the wireless datalink communication area between two aircraft was analyzed by considering the factors such as transmitters, receivers, send and receive antennas in communication datalink, transmission space and earth curvature, vehicle attitude angle and space positional relationship of aircrafts from implementing the normal communication conditions. A mathematical model of wireless datalink communication area between two aircraft was developed, including antennas, flight altitude, space positional relationship of two aircraft, communication area models and so on. The model has been successfully applied to a particular model; it provides a reference for analyzing air-to-ground wireless transmission system communication area based on the wireless datalink communication, and supplies for the spacecraft, satellite and other air-to-air, air-to-ground wireless data communications systems.
Calculation of aircraft exhaust system infrared characteristics based on SNBCK model and finite volume method
Hu Haiyang, Wang Qiang
2009, 35(9): 1121-1124.
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The coupled calculations for flow fluid field, species concentration field and gas radiation transfer /energy equations based on SNBCK model were employed to simulate accurately the aerothermodynamic and infrared characteristics of the aircraft exhaust system. The parameters of narrow-band model were evaluated by HITEMP line-by-line database. Two calculating cases, the computation of carbon dioxide absorptivity at 4.3 micron band and the radiation heat transfer evaluation of the cylindrical furnace, respectively proved the accuracy of using this method to calculate radiation transfer/energy equations. Finally, the infrared characteristics of two two-dimensional nozzles were calculated, and the results show the great differences of infrared characteristic for high width-height ratio 2-dimentional nozzle between ground and high altitude state.
Design of ethanol micro gas turbine engine
Zhang Chi, Wang Jianchen, Qin Qingqin, Du Peng
2009, 35(9): 1125-1129.
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To develop the application of the biomass fuel in micro-turbine-based distributed energy system, micro gas turbine using ethanol as fuel was designed. The design operation parameters of this micro gas turbine were determined by thermodynamic cycle. Based on the parameters and the characteristic of ethanol fuel, the combustor geometry size was designed. Thus the technology of micro gas turbine combustor was achieved for the combustion of ethanol fuel. Experimental results of this engine indicate that the ethanol micro gas turbine engine has successfully realized self-operating, and it demonstrates the designed scheme of the engine is feasible.
Rapid resolution of GPS ambiguities of satellite formation flying with two-step method
Wang Haitao, Ou Jikun, Yuan Yunbin
2009, 35(9): 1130-1133.
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In order to rapidly resolve the carrier ambiguities of satellite formation flying, a two-step method combined with extended Kalman filter (EKF) was proposed. The first step is to fix the wide-lane ambiguities during the state estimation after initializing the filtering with carrier-smoothed-code algorithm and mean value of L6. The second step is to calculate the float double-frequency ambiguities with the method of selecting the parameter weights using the baseline component as a constraint. The simulated case reveales that the baseline accuracy is within 5 cm after the wide-lane ambiguity was solved and the proposed method can correctly resolve the ambiguities within 3 minutes after the filtering initialization with 10 epochs observation.
Randomization analysis of the thermal-mechanical crack growth
Yang Hongqin, Bao Rui, Zhang Jianyu, Fei Binjun
2009, 35(9): 1134-1138.
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In order to describe the crack growth law under thermal-mechanical loading, the linear superposition model of fatigue and creep crack growth was amended based on the experimental results. New material parameters in the model were determined, as the original ones may not be independent of the stress ratio, temperature and dwell time due to the influence of alternating load to the creep crack propagation. Then, a random crack growth model was obtained by introducing lognormal random process to the amended model. With the Taylor series expansion, the distribution of the crack size at any service time and the distribution of the service time to reach any crack size were attained. An example was given to validate the reliability of the proposed randomization method by comparing the life distribution obtained from the model with the experiment.
Effectiveness analysis of multi-source decoying system against ARM
Zhao Juanjuan, Ma Dongli, Zheng Jiang-an
2009, 35(9): 1139-1143.
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Based on the theory of active decoying system against anti-rediation missile(ARM), decoy error formula was derived. Three typical distributions, which were the first three-source distribution, the second three-source distribution and four-source distribution were discussed as examples, and the error formulae of them were simplified, and decoy error curves were obtained with numerical calculation, then the influence of radiation source power rate on decoy error under different distributions was analyzed. Besides, the real attack process of ARM was also analyzed, and ARM-s mobile correction was inducted. Then diagrams of ARM-s point of impact and radar-s protect probability curves were obtained with simulation analysis. Decoy effect of different distributions was compared with each other, and the results show that four-source distribution is the best plan. These conclusions have great significance in researching the operational effectiveness of multi-source decoying system against ARM.
GA based design of sliding mode control law for hypersonic vehicle
Li Huifeng, Wang Jian, Sun Wenchong
2009, 35(9): 1144-1147.
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A sliding mode control law was presented according to the six DOF nonlinear model of pitching channel of hypersonic vehicle generic hypersonic vehicle(GHV). First, for making a good use of sliding mode control theory, the six DOF model was transformed into an affine system through input-output feedback linearization. Then, the structure of sliding mode control law was designed for the affine system. After the structure design of sliding mode control law, the control parameters of sliding mode control law were designed based on genetic algorithm. The design process of sliding mode control parameters takes into account stochastic robustness strategy, which is to make sure that the possibility of loss of flight control stability or robustness achieves least through control parameter optimization based on genetic algorithm, when dealing with parameter uncertainties in stochastic uniform distribution. Simulations show that the method is able to satisfy both the robustness of flight control system and the convergence of parameter optimization process on request.
Evaluate interoperability of foundational software platform by Bayesian networks
Lan Yuqing, Zhao Tong
2009, 35(9): 1148-1151.
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Interoperability is one of the most important features of current software. Bayesian networks was proposed to solve the problem of evaluating interoperability of foundational software platform after analyzing both the problem domain and the Bayesian networks feature domain. First of all, Bayesian algorithm was chosen according to the problem domain, and actual data were gathered for importing domain knowledge. Bayesian structure was formed by the selected algorithm and used to learn its parameters. During this process, the chosen K2 algorithm was improved. After that, Bayesian reasoning was used to evaluate the grade of interoperability of foundational software platform according to the established Bayesian structure and parameters. At last, an application showed how to use this brand-new model to evaluate the interoperability of foundational software platform. The experimental result proved the reasonableness and usefulness of the model.
Integrated reliability assessment using varied environment test data
Hong Dongpao, Zhao Yu, Ma Xiaobing
2009, 35(9): 1152-1155.
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The influence of environment on reliability was studied, and a method of integrated reliability assessment using varied environment test data was put forward. The relations of reliability and environment factors were described by the Cox proportional hazards model, and the influences of environment factors were measured. According to the reliability model and the measurement, a new data conversion was proposed to convert the test data of varied environment into that of the same environment. Then the reliability of product was assessed synthetically with the converted test data. With the method, the varied environment test data is used synthetically to enlarge the sample size and increase the information for reliability assessment. Thus, the precision of reliability assessment is improved. The example shows that the method is reasonable, and it is convenient for engineering.
Improved ECS algorithm for spaceborne spotlight SAR based on deramp processing
Li Ran, Li Jingwen, Li Linlin
2009, 35(9): 1156-1160.
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Based on the two-step imaging algorithm and the extended chirp scaling (ECS) algorithm,an approach for spotlight mode of spaceborne synthetic aperture radar(SAR), which combines the deramp processing and ECS algorithm was proposed. The deramp processing is based on SPECAN algorithm, and passes the raw data through a space invariant azimuth matched filter. The azimuthal spectral folding caused by insufficient sampling rate especially in high resolution spaceborne spotlight SAR was overcomed through the deramp processing. Although the division into subappertures in ECS can reduce the system requirement of the pulse repetition frequency(PRF), the PRF is restricted to higher than the accumulated doppler frequency bandwidth of a single point target. The presented method further reduces the requirement of the PRF in subapperture processing without the resolution loss. Thereby the ECS algotithm can be applied easily. The simulating and imaging results of point targets demonstrate the validity of this approach.

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