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2008 Vol. 34, No. 12

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Numerical model for a commercial aircraft water landing
Hu Dayong, Yang Jialing, Wang Zanping, Wei Jiaoyu, Tong Yabin
2008, 34(12): 1369-1374.
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Aircraft water impact crashworthiness must be considered for the aircraft used near or over the sea. The current crashworthiness criteria, design approaches and analysis methods have mainly focused on the ground impact conditions, without adequately accounting for fundamental differences associated with water crashes. This is because the crash dynamics in water impact condition is extremely complex with multi-physics interacting. To simplify the problem, an uncoupled method is proposed, using finite element simulation combined with corresponding experiments. A finite element model of reasonably simplified aircraft structure including the fuselage, wing and empennage is established by using MSC.PATRAN/MSC.DYTRAN code. The loading condition is transformed from the ditching test and thirteen dynamic load cases are considered in computation. Corresponding stress distributions for each case are predicted. It is shown that the strength of the skin on the bottom of fuselage will not be failed.
Design of guidance law of missile in attack with high angle
Bao Yiming, Jiang Zhichao, Peng Chen, Wu Sentang
2008, 34(12): 1375-1378.
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According to the requirements of impact angle constraint of the missile, a new terminal guidance law was deduced base on the Lyapunov method to null miss distance and to achieve a desired impact attitude angle, simultaneously. The impact angle constraint was turned to line of sight angle constraint in this method. The proposed guidance law contains two parts that base on line of sight angle rate and the difference between the line of sight angle and the required line of sight angle, respectively. To adjust the two parts portion reasonably the guidance goal with the overload constraint can be realized. The proposed guidance law is simple and convenient to be realized in engineering. Besides that, the best initial condition when the guidance law imported was analyzed considering the missile-s overload availability and the seeker-s performance. The simulation result for model of some missiles shows the effectiveness of this proposed guidance law.
Application of experimental design in software reliability test
Fu Jianping, Lu Minyan, Ruan Lian, Huang Baiqiao
2008, 34(12): 1379-1383.
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Experimental design was introduced to software reliability test to take full advantage of resources and optimize test data. Typical operations were selected by orthogonal experiment design in the development of operational profiles and optimized results were produced by combinatorial design in the generation of test data considering of occurrence probabilities. A full software reliability test consists of determining the system modes profile, developing operational profiles by orthogonal experiment design, choosing run categories by combinatorial design and generating reliability test data to execute test finally. An automation test data generation tool was developed according to the method and an example was applied with it. Results show that it can not only generate software reliability test data but also finding more software defects.
Novel method for moving point target detection under glint and clutter background of sea-sky blending
Zhu Fengyun, Qin Shiyin
2008, 34(12): 1384-1387.
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Based on the features of glint and clutter sea-sky blending background as well as point target with one pixel, a fast location algorithm for sea-sky blending area and an extended median-mean filter for all direction ring-neighborhood difference data based on pattern classification were designed as pre-processing methods. The all-direction difference was re-carried out again so that candidates of point target can be detected by segmentation with an adaptive threshold based on histogram. The morphologic filter was used to keep point targets with only one pixel. Finally the moving point target and its trajectory can be detected in sequence images based on trajectory matching and direct search if mismatching occurs. The simulation results with 220 frame images which were made by adding simulation point target in real images show that moving point targets with signal to noise ratio (SNR) not lower than 0.5 can be detected effectively: the correct detection rate is 91% in one frame and 95% in a sequence of three frames, in addition the false alarm in a sequence of three frames does not occur for the 22 frame images without simulation point target.
Longitudinal flight qualities of the saucer-shaped aircraft
Wang Linlin, Gao Ge
2008, 34(12): 1388-1391.
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The saucer-shaped aircraft is a novel aircraft adopting blend-wing-body configuration. The linear perturbation theory based on the classic flight dynamics was used to analyze the longitudinal flight qualities of the saucer-shaped aircraft under low speed conditions, and the time-domain method was applied on the longitudinal mode. The longitudinal flight qualities were given by simulation. Meanwhile, flight tests were conducted to validate the analysis results. The aerodynamic characteristics of the saucer-shaped aircraft, the conventional aircraft and the flying wing aircraft were also contrasted to discuss their similarities and differences. The results show that he saucer-shaped aircraft has a stable longitudinal mode and exhibits superior flight qualities and excellent comprehensive performances.
Automatic configuration approach for ATS test resource based on a kind of matching function
Fu Xinhua, Xiao Mingqing
2008, 34(12): 1392-1397.
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Aiming at the problem of lacking in design automation and generalization during the process of instrument selection and resource configuration of automatic test system(ATS), a kind of matching function was presented to describe the matching degree between test point and instrument port. Matching function was built with signal-oriented method, and it integrated signal properties of test point, capability parameters of instrument, and instrument- s price, reliability, operation complexity and so on. The strategy and algorithm for matching test point and instrument port were proposed. And the strategy was also optimized to meet the requirement of parallel test. The method was validated by an example and the result showed that it could reduce test cost, enhance system reliability and improve test efficiency and throughput.
Decoupling method for solving isothermal phase change problem
Wu Bin, Xing Yuming
2008, 34(12): 1398-1401.
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A simple computational model for isothermal phase change problem was based on the enthalpy formulation. The temperature field and liquid fraction field were decoupled of the computational model to solve the temperature of the control volume separately which was melting/freezing or not. The computational model was verified with a test problem of a rectangular container. The agreement of the computation results with the experimental data indicates this method could be used to estimate the model-s isothermal phase change quickly and effectively. The numerical analysis of the melting time of phase change material for rectangular and cylindrical containers was then performed using the computational model. The results show that the phase change material of rectangular container requires nearly half of the melting time as for the cylindrical container of the same volume and characteristic size.
Electrochemical oxidation film of magnesium alloy at low voltage( 10V)
Zhu Liqun, Wang Ximei, Zhang Lingling
2008, 34(12): 1402-1406.
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Anodic oxidation coatings formed on the surface of magnesium alloys at higher voltage could degrade the mechanical performance of the magnesium alloys material. In order to overcome the shortcoming of mechanical performance reduction, the electrochemical oxidation films were prepared on AZ91D magnesium alloy in Na2SiO3 mainly contained solution and the electrochemical oxidation voltage which was supplied by AC power supply was from 10 V to 110 V. The growth process of the electrochemical oxidation on the surface of AZ91D magnesium alloys was studied. The influence of oxidation voltage and electrochemical oxidation time on the oxidation films was discussed. The microstructure of the electrochemical oxidation films formed at different oxidation voltage and time were analyzed as well. The results show that the corrosion resistance of the electrochemical oxidation films formed at 10 V is as good as that formed at 70~110 V. The growth process of the electrochemical oxidation films formed at 10 V could be summarized under four steps which are grain-like, block-like, integrated insulating and cross-layer films respectively.
Fuzzy logic reaction control method for re-entry vehicle
Li Kefeng, Song Jianshuang, Ren Zhang, Zhang Qingzhen
2008, 34(12): 1407-1410.
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To solve the re-entry control problem of reusable launch vehicle (RLV), a reaction control system (RCS) based on fuzzy logic was presented. The characteristic of RCS was analyzed deeply, and the RCS model based on effect coefficient and relay feature was built. Then the three-channel RCS controller based on fuzzy logic by using the expertise knowledge was designed. Both of the attitude angles and attitude angles- rate errors were used to be the controller-s inputs. These inputs were processed by fuzzy logic controller, and then the RCS commands to each channel were generated. This controller was testified in the 6 degree of freedom simulation system and compared its effect with proportional-integral-differential (PID) controller. It was proved by the simulation results that the controller has better tracking performance and the RCS outputs are more efficient.
Fast mode selection for intra and inter prediction
Zhu Leiqi, Zhang Qishan, Yang Dongkai, Hu Weiwei
2008, 34(12): 1411-1414.
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H.264 video coding standard is high complex and time-consuming owing to its multi-mode in intra prediction and multi-size sub-block modes in inter prediction to improve the efficiency of I frame and P frame. A new algorithm with fast mode selection based on wavelet transforms in intra prediction and combined with pre-estimation of intra mode in inter prediction was proposed. Firstly, the method utilized the optimal modes selected in low frequent part transformed by wavelet to estimate the possible modes in sub-block of original macro-block. This method reduces the calculate times from 9 to 3.75 averagely. Secondly, pre-estimation of intra mode in inter prediction was implemented using the parameter of mean removed mean absolute difference, and it reduced the P frame coding time. Simulation experiment results from video sequences show the method effective with the encoding time of sequences lower about 19% averagely while peak signal-to-noise ratio lower 0.0664dB at most.
Calculation method for military aircraft’s turnaround time
Wei Yi, Kang Rui, Cheng Hailong
2008, 34(12): 1415-1418.
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The turnaround time (TAT) is one of main measurement parameter for evaluating the fight capability of military airplane. In order to solve the problem of how to analysis and compute military airplane-s TAT, based on the discussion of impact factors on TAT from military airplane-s mission type, design characteristics and operational support resource, a calculation method for one military aircraft-s TAT was provided. While computing the TAT, the airplane-s mission type percentage was integrated and mission type matrix and TAT matrix was constructed. A matrix was used to define the logic relationship between work items of turnaround activity. The elements of this matrix were ranked and ordered topologically, and the results were put in sets for computing. Based on the results critical work items of each mission type TAT were determined, and the critical impacting factors on this mission type TAT were obtained. These factors will provide auxiliary decision for improving military airplane design and operational support resources planning.
Preparation of superhydrophobic copper surfaces by electroplating
Qiao Zhenmei, Xi Wenjun, Zhu Chunlei, Jia Ao
2008, 34(12): 1419-1422.
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The structure of the natural superhydrohlbic surface, lotus leaf, was studied, which inspired the fabrication method of superhydrophobic surfaces. Various copper surfaces were fabricated in different current densities via electroplating. As the current density increased, the water contact angle (CA) increased first and then decreased. When the current density was about 0.08 A/cm2, the electroplated copper surface which resembled the lotus leaf reached superhydrophobic state (CA=153.5°, SA (sliding angle) = 7.9°). The surface with lotus leaf structure is superhydrophobic without any surface modification. It-s suggested that this is a meta-stable state in Cassie state. As long as the surface structure is suitable, a hydrophobic surface could be gotten, or even superhydrophobic surface, on hydrophilic materials. The hydrophobic mechanism was also analyzed. The results widen the horizon of fabricating superhydrophobic surfaces on hydrophilic materials and give light to the existing popular theories.
Temperature prediction for nano satellite on orbit based on BP neural network
Zhang Xudong, Li Yunze
2008, 34(12): 1423-1427.
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In order to realize the temperature prediction for nano satellite on orbit, a basic thermal environment model of nano satellite was established and analyzed. A BP neural network was used to predict the temperature of nano satellite based on it. After the analysis of the thermal environment model, the thermal flow of satellite-s crust, radiater and equipments in cabin was got and used as the inputs of the BP neural network, their temperatures were used as the outputs and data sample of BP neural network was got and used to train BP neural network. The BP neural network which was trained is the temperature prediction model of nano satellite and used to predict the temperature of the satellite on orbit after 10s. Results fit the actual temperature of nano satellite on orbit well, and show that the temperature prediction model of neural network can predict the temperature of nano satellite accurately and rapidly.
Uncertain theory for fatigue crack extension
Wang Jun, Qiu Zhiping
2008, 34(12): 1428-1432.
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Based on the foremost two non-probabilistic methods, second-order interval analysis method and second-order convex model method were advanced. The uncertain theories described all the uncertainties as interval or convex set. Then through the Taylor series expansion, the interval range of fatigue crack growth rate and its life with uncertainty parameters can be estimated. The inclusion relation of traditional probabilistic method and two uncertain theories was presented. This inclusion relation can verify the results of examples. The fatigue crack growth rate and its life of 00Cr17Ni14Mo2 were computed to illustrate that uncertain theories are effective by comparing with the interval analysis method, convex model method and the traditional probabilistic method. Their advantages are that they only need less statistical data and the method is simple, practical and with high precision.
Risk decision for the development of the aerospace project based on the incomplete linguistic information
Yang Yaqin, Zhou Rongxi, Qiu Wanhua
2008, 34(12): 1433-1436.
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For the complexity of aerospace project development, its risk evaluating model was proposed on the basis of modern multiple attribute linguistic decision method. The method of decision based on uncertain extended ordered weighed averaging (UEOWA) operator was given under incomplete linguistic information. The scale of risk measure was extended, on the one hand which can measure accurately the risk, on the other hand which can match with linguistic information of decision model in reason. The example of risk decision for aerospace project development was presented to show the feasibility and effectiveness of this method. It can offer a new method for the evaluation of project risk.
Structure-preserving balanced truncation for flexible spacecraft using cross Gramian
Meng Zhanfeng, Han Chao
2008, 34(12): 1437-1440.
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For model reduction of flexible spacecraft, conventional first-order balanced truncation(FOBT) method will destroy the second-order structure and dynamic properties of original system. In order to overcome this drawback, a new structure-preserving approximated balanced truncation method for model reduction of flexible spacecraft was proposed. The modal cost was described by a cross Gramian and the closed-form solution of cross Gamian was obtained via special form of dynamical equation of flexible spacecraft. The new method preserves the second-order structure, symmetry and positive definiteness of the original system. The numerical results show that the new method is superior to conventional first-order balanced truncation(FOBT) method for improving efficiency without sacrificing accuracy.
Normalized cross correlation computation for geometry image features
Sun Minglei, Zhang Rong, Zhu Xiaofeng, Zong Guanghua
2008, 34(12): 1441-1444.
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Normalized cross correlation operator (NCCO) was used for pattern matching to localize popular cross-shaped features in microscopic vision. Distribution feature of similarity function around peak zone was found to be four symmetry hyperboloid planes. Inspired by this, some research work on pattern matching of geometry image features (such as rectangular, circular, etc.) was presented. A probability distribution based formula computing NCCO with two binary images was proposed. Mathematic models of some typical geometry image features- (rectangular, circular, cross-type, box-type) similar functions around peak point were derived from and proved. Based on these models, some experiments about template image optimum and feature size optimum were conducted on a microscopic vision workcell. Conclusions above are practically useful to image positioning, image calibration and image tracking techniques.
Model design of project risk assessment based on cloud theory
Liu Xiaolong, Qiu Wanhua
2008, 34(12): 1445-1447.
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A risk evaluation method based on the cloud theory was put forward for evaluating project risk quantitatively. Cloud theory was proved to be an excellent mathematical tool for dealing with uncertain and vague description of objects, and it can realize the transforms between qualitative concepts and their quantitative expression . Based on the cloud theory, the system performance model and the cloud model of the risk assessment were proposed .A new way for project risk assessment was given and it can solve the transition problem between qualitative and quantitative in risk assessment. The project risk model was constructed by analyzing the causal relation between risk and risk factors, and the research way of project risk model was expanded in our country of a period of economy, and the applied value of the system of risk assessment was illustrated by practical application.
Remote sensing image fusion assessment based on SVD
Zhu Weigang, Zhou Yinqing, Xu Huaping, Li Chunsheng
2008, 34(12): 1448-1451.
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Existent measures of fused image quality were analyzed to research the objective evaluation problem of remote sensing image fusion. A new approach based on the singular value decomposition (SVD) was proposed for the remote sensing image fusion assessment. This method measured the divergence of the singular value features between the source images and fused image, and calculated energy distortion of fused image from source images. By that means, effect of fusion algorithm was measured. Experiments were conducted from two aspects to confirm the idea. When the source images including SAR image, this method is more effective than the Piella-s evaluation methods and Xydeas-s evaluation methods. In the other hand, the experiments of different kinds of sensors and pixel-level fusion algorithms show that the objective evaluation appears highly consistent with the subjective evaluation. It is an effective and universal assessment method with high coherence to the subjective factors.
Design of low voltage CMOS folded-cascode mixer
Song Dan, Zhang Xiaolin, Xia Wenbo
2008, 34(12): 1452-1455.
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By using the folded-cascode structure, the problem on high supply voltage of the stacking trans-conductance stage and switching-transistor stage was solved, and the trade-off among the high trans-conductance, high linearity of the trans-conductance stage and the low noise of the switching-transistor stage were also realized. Implemented in a SMIC 0.18μm CMOS process, the low-voltage complementary metal-oxide semiconductor (CMOS) folded-cascode mixer (FCM) core has an area of 165μm×75μm. When the frequency of the radio frequency (RF) signal, local oscillator (LO) signal and the intermediate frequency (IF) signal are 1575.42MHz, 1570MHz and 5.42MHz, respectively, the simulation results show that the mixer features a conversion gain ( GC ) of 15dB, a dual sideband (DSB) noise figure of 12.5dB, a third-order input intercept point (IIP3) of -0.4dBm, and consumes 3.8mW at a power supply voltage of 1.2V. The mixer can be applied to the electronic systems within the realm of the aviation aerospace.
Improving dorsal S-shaped inlet performance by vortex flow control
Li Dawei, Ma Dongli
2008, 34(12): 1456-1459.
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In order to effectively reduce flow distortion produced in the S-shaped inlet, a computational fluid dynamics (CFD) procedure was used to design vortex generator installations near the entry of the diffuser. Several parameters, i.e. the ratio of generator blade height to local boundary layer thickness, the locating position, angle against the centerline, that characterize the vortex generator array were discussed to determine their effects. Especially the numbers of blades were varied to minimize total pressure distortion by restructuring the development of secondary flow. The results show that by using a properly designed vortex generator array total pressure distortion can be greatly reduced and flow separation can be totally prevented, the vortex generator with 8 pairs of blades reduced the circumferential distortion from 0.11 to 0.09. These results should provide valuable guidance in designing vortex generator installations in the S-shaped inlet.
Signal processing method and realization of vortex flow meter
Zhang Yuxiao, Zheng Dezhi, Fan Shangchun
2008, 34(12): 1460-1463.
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A new method of vortex flow meter based on variable gain amplifier and band pass switched-capacitor active filter is designed. The singlechip processor measures the range and frequency of the vortex flow meter output signals by the inner analog to digital converter (A/D), and the gain of the variable gain amplifier is controlled by the digital to analog converter (D/A) of the processor, then the relative stable active signal is provided to the subsequent measurement circuits. The band pass switched-capacitor active filter traces the frequency of the variable gain amplifier output signal, it is guaranteed that the center frequency of the band pass filter is near to the signal frequency, so the favourable filter result is obtained. The frequency of the filtered signal and the flux of the liquid are calculated by the processor. The experimental results show that the complex amplifier circuit due to the large variable range of the vortex flow meter output signal is replaced, and the discontinuous problem of the signal is solved. The noise of the signal is effectively restrained because that the center frequency of the band pass filter is adjusted by the processor.
Numerical and experimental research on buckling design of reaction-wheel’s sealed cowling structure
Zhao Libin, Long Liping, Zhang Jianyu, Han Bangcheng
2008, 34(12): 1464-1468.
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It is significant to ensure stability of the sealed cowling structure, which offers a safe work environment for the reaction-wheel. The stability of some kind of sealed cowling structure was quantitatively researched by the eigenvalue buckling technique and nonlinear analysis method based on the general software ANSYS. The shell shape as a key factor to affect the stability of the sealed cowling was pointed. A small protruding arc and large concave arc scheme was presented to design the sealed cowling structures. The application scopes of the eigenvalue buckling analysis and nonlinear buckling analysis were described aimed to the similar structures. The experimental results illustrate the practicability to predict the critical buckling load via nonlinear buckling analysis method in engineering. The researches are useful for the design and buckling analysis of similar structures.
Performance analysis and experimental research on nitrous oxide monopropellant micro-thruster
Sun Wei, Fang Jie, Cai Guobiao, Cong Yu
2008, 34(12): 1469-1472.
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Performance analysis for monopropellant micro-thruster using nitrous oxide (N2O) propellant was carried out based on the thermodynamic computation. Preliminary results show that decomposition rate of nitrous oxide and the expansion ratio of nozzle both have effects on the specific impulse of the thruster. Experiments of nitrous oxide catalytic decomposition at different initial catalyst bed temperature were conducted in testers of different structures. Self-sustaining decomposition reaction of nitrous oxide was observed at preheated temperature of 250℃. The performance of the sub-Newton micro-thruster was greatly affected by the combustion chamber structure and the loading factor of catalyst bed according to experimental results. Although the results are not conclusive because of the small initial test set, preliminary numbers demonstrate the feasibility of the N2O monopropellant micro-thruster.
Triangular mesh generation algorithm of point clouds
Li Xu, Gao Feng
2008, 34(12): 1473-1476.
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The establishment of topological mesh problem in point clouds preprocessing was researched. To solve the problem obtaining the correct topological relations of the scattered point clouds, a sort of triangulation based on incremental growth was researched for point clouds. Searched the nearest neighbors of boundary points by using the algorithm of k-nearest neighbors quickly, it constructs triangles based on the boundary ring of incremental algorithm, and realizes the construction of topological mesh. Three new criteria were presented for the selection of the optimal points, and three operations of mesh topology based on the different position of the optimal points was given out to construct new triangular mesh,which the triangulation could be proceeded precisely. The overlapping , pore as well as long and narrow triangles were eliminated. The application for the point clouds of auto body indicates that triangulation mesh of body surface can be constructed effectively and steadily.

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