2006 Vol. 32, No. 12

Display Method:
Numerical study of aeroheating predictions for hypersonic reentry bodies
Kang Honglin, Yan Chao, Li Tinghe, Guo Dilong
2006, 32(12): 1395-1398.
Abstract:
In order to calculate the heating rates on hypersonic blunt bodies quickly and effectively, two engineering methods were developed based upon the axisymmetric analogue which required tracking the inviscid surface streamlines. Engineering predictions in the boundary layer were used in both methods. However, method No.1 used engineering predictions out of the boundary layer, and in method No.2 the boundary-layer edge conditions were determined by the CFD method solved by Euler equations of three dimensions. Results of the two methods are in good agreement with the existing experimental data, which validates the correctness of the methods in calculating the heating rates on hypersonic vehicles. Results of these two engineering methods were also compared with those of CFD method solved by N-S equations, which indicates that the engineering methods save much calculating time and also have precision on predicting the heating rates on windward.
Calculation method of critical radar cross section of low pulse repetition frequency PD radar
Ma Dongli, Ma Tielin, Liu Weiwei
2006, 32(12): 1399-1402.
Abstract:
The aerodynamic characteristic of UAV(unmanned air vehicle) was studied based on the method of combining aerodynamic prediction with wind tunnel test. The contrast tests of longitudinal moment for different anhedral and incidence of V-tails were conducted to confirm the empennage distribution and to find out that the anhedral of V-tail affected the longitudinal moment greatly. The causes of turnup moment curves were analyzed. The components and the whole airplane aerodynamic tests were carried out, and the methods for calculating the aerodynamic characteristic of V-tail UAVs were given. Furthermore, the cause of the difference between the two methods was analyzed. The aerodynamic characteristic of a UAV was optimized by adjusting the incidence of empennage. In the wind tunnel test, the aerodynamic prediction methodology is testified reliable to be used to calculate the aerodynamic characteristic of the other airplane with the same aerodynamic configuration.
Study of aeroelastic tailoring of high-aspect-ratio flexible composite wing
Liu Xiangning, Xiang Jinwu
2006, 32(12): 1403-1407.
Abstract:
The nonlinear government equations of the flutter problem of high-aspect-ratio flexible composite wing were derived from the most general aeroelasticequations with wing′s structure geometrical and aerodynamic nonlinearity being considered. Then the gradients of flutter speed and frequency of wing with respect to the design variables were deduced with analytical method. The influence of the composite wing′s configuration and ply angle on the flutter speed was revealed. It was concluded that the composite structure configuration that caused negative bending twist coupling was beneficial to wing′s flutter performances. An optimization design of a high-aspect-ratio flexible composite wing model was done with the flutter speed as object function and the composite plies as design variables. The best configuration and plies were obtained and the results obtained with analytical gradients of this paper and numerical difference gradients were compared at the same time.
Simulation experimental technique and primary study of Reynolds number effect on vortex asymmetry at forebody
Bo Nan, Deng Xueying, Wang Yankui
2006, 32(12): 1408-1412.
Abstract:
An experimental study with pressure measurement at low speed subcritical and critical Reynolds number range has been carried out for both slender body models with fineness ratios of 6.15 and 11. The results show that if the end of afterbody is far enough from the twin asymmetric vortices region, the muti-vortices system controlled by twin asymmetric vortices at forebody should be not influenced, and the correlations between manual mini-perturbation on the model nose and asymmetric vortex response are also consistent for experimental results of both models. It provides a high Reynolds simulation experimental technique in low speed wind tunnel with increasing the model diameter and decreasing the fineness ratio of test slender model. Based on this simulation technique, the results in critical Reynolds show that the sectional pressure distributions are much different at subcritical and critical Reynolds number ranges. At critical Reynolds number, the side force on the slender body is much lower, and the two-cyclebehavior of the curve Cy vs. γ is no longer existed, therefore the active control technique of asymmetric vortices with a single hole bleed perturbation is useless at critical Reynolds number range.
RCS study of moving radar targets
Su Donglin, Zeng Guoqi, Liu Yan, Wang Guoyu
2006, 32(12): 1413-1417.
Abstract:
Obtaining the angles between the moving target and the radar is very important in the study of radar cross section(RCS) of moving targets. The angles between the moving target and the radar were defined and calculated in detail. The differences and relationship of angles from static targets and moving targets were also discussed. The method of quasi-static was used to analyze the scattering from moving target. In high frequency approximate, RCS comes from the contributions of face scatter, edge scatter and corner reflector, ect. Because of the influence of airflow, the aircraft will be tremored in random. A kind of tremor model was used to analyze the effect of tremor on RCS. It indicates that the deviate degree of RCS increases with the frequency, the effect from tremor on RCS is different at different angles,and it is tremendous in certain angles.
Accurate method to calculate space-borne SAR Doppler parameters
Wen Zhu, Zhou Yinqing, Chen Jie
2006, 32(12): 1418-1421.
Abstract:
A new method which can calculate the whole swath Doppler parameters of space-borne SAR(synthetic aperture radar) was presented. The method, based on space coordinate transformation, made the satellite position and velocity as references. Using the space geometric model and the coordinate transformation, a quartic equation between the slant range and the look angle was founded. After solving the equation, the look angle value was got, and the Doppler parameters were then calculated. The simulation results show that the calculation precision of the method can reach below 0.02Hz(Doppler centroid) and 2×10-4Hz/s(Doppler rate) with no satellite position and velocity error. The precision can reach below 0.8Hz(Doppler centroid) and 0.07Hz/s(Doppler rate) even if there are measurement errors in satellite position (300m) and velocity (0.3m/s). This method is suitable for both single SAR and distributed SAR Doppler parameters precision calculations.
Dynamic source routing algorithm for LEO satellite networks
Song Xuegui, Liu Kai, Zhang Jun, Cheng Lianzhen
2006, 32(12): 1422-1426.
Abstract:
Based on the regular and predictable features of topology changes in low earth orbit (LEO) satellite networks, a dynamic source routing algorithm, namely adaptive route-selection (ARS) algorithm, was presented for LEO satellite networks. In the algorithm, logical location is adopted to hide satellite mobility from the routing algorithm so that a source satellite can compute the path with minimum propagation delay between source and destination satellites by only knowing their logical locations, which avoids the exchange overhead of collecting route information from other intermediate satellites. An efficient metric was proposed to denote the path with minimum propagation delay on the basisof its distribution properties. Then the path is designated by source satellite in packet header and according to the path the packet is forwarded to its destination satellite by intermediate satellites, which can greatly decrease the route overhead compared with other dynamic source routing algorithms. The algorithm can also deal with packet routing issues in case of link congestion or satellite failure. The performance comparison of the ARS algorithm with datagram routing algorithm (DRA) and Bellman′s shortest path (SP) algorithm was evaluated by simulation. The simulation results show that the proposed algorithm can guarantee the demand of end-to-end transmission delay for data packets with lower computation and exchange overhead.
Influence of slot width on transmission properties of frequency selective surfaces
Wang Huanqing, Lü Mingyun, Meng Zhijun, Wu Zhe
2006, 32(12): 1427-1430.
Abstract:
Influence of slot width on transmission properties of plannar FSS(frequency selective surfaces) was explained by physical essence. With the width of element slot in FSS increasing, it could shorten resonant wavelength of the element. Correspondingly it could increase the resonant frequency of the element. Influence of slot width on transmission properties of plannar FSS was calculated with Floquet theorem, and the small rectangle element was machined successfully by etching technique. Effects of the slot width on the transmission properties of FSS waspreliminarily explored by experiment. The experimental results show that the resonant frequency of FSS increases with the slot width, and the transmission ratio and resonant bandwidth is becoming greater. The experimental data accord with the computed results within error permissibility.
Quiet zone analysis of a RF simulation anechoic chamber
Ma Yongguang, Chen Haibo, He Guoyu
2006, 32(12): 1431-1434.
Abstract:
The performance of a RF(radio frequency) simulation anechoic chamber is influenced by many factors. With the geometrical optics methods, the quiet zone performance of a RF simulation anechoic chamber was analysed from the three factors, including microwave anechoic chamber layout, performance of radar absorbing materials and antenna radiation direction character. The calculating model of anechoic chambers quietness on co-polarization was gained and the quiet zone performance was computed in four frequency (0.8GHz, 2GHz, 6GHz, and 18GHz) based on reflectivity of radar absorbing materials and antenna pattern data provided by certain institute.The level layout of the quiet zone center face was gained in horizon and vertical polarization.The computed results accord with technic request, and indicate that this method could rapidly and exactly analyse the performance of a RF simulation anechoic chamber.
Wavelet based fault detection of aeronautic engine vanes by borescope
Ding Peng, Li Changyou, Ma Qishuang, Yao Hongyu
2006, 32(12): 1435-1438.
Abstract:
Using borescope equipment to inspect the inside of turbofan engines is an important technology to the daily fault diagnostic of aeronautic engine. In all the aeronautic engine interior faults, vane′s face fault is a regular one. Towards vane′s face fault, a kind of fault detection and estimation method was presented. First, vane′s face fault was detected by the SUSAN(smallest univalue segment assimilating nucleus) edge detector. Second, the image was analyzed by wavelet transforms to achieve the different frequency components at different locations. Third, the energy of the alternating components around fault was computed by the spectrum. And at last the vane′s face fault was detected and estimated by the energy. Test result shows that this method can quantificationally detect the fault of aeronautic engine vanes and estimate the grade of the fault. It provides a scientific basis for the fault detection and estimation of aeronautic engine vanes by borescope.
Influence of source spectrum on bias stability of interference fiber optic gyroscopes
Li Yan, Ou Pan, Zhang Chunxi, Xu Hongjie
2006, 32(12): 1439-1442.
Abstract:
The Jones matrixes and mathematical model for the optical transmission of IFOG(interference fiber optic gyroscopes) were built based on the polarization IFOG, which uses Y waveguide integrated optical modulator, and depended on the parameters of the optical instruments. The polarization errors were analyzed theoretically, and the expressions of the polarization errors of IFOG were achieved. The influence of different source spectra on the bias stability of IFOG, caused by the polarization errors, was analyzed for the first time with the aid of source degree of polarization. By calculation, when the source degree of polarization changes linearly between 0~3% and other parameters are constants, the result that the narrower the spectrum, the larger the bias stability caused by the polarization errors is achieved. Simulation results give theoretical reference to the selection of source spectra for the IFOG.
Scheme design and FPGA implementation of airborne image lossless and near-lossless compression
Liu Bo, Jiang Hongxu, Lian Youpin, Lu Jinyuan
2006, 32(12): 1443-1446.
Abstract:
For plane on-board image lossless and near-lossless compression, an improved compression algorithm based on the JPEG-LS was given. The algorithm is composed of three parts, decorrelation processor, adaptive entropy coder and controlling of compression ratio. The new decorrelation model solved the problem of transmission error propagation in JPEG-LS. A fast and effective entropy coder named Golomb was modified and used in the algorithm, and that a valid controlling strategy of compression ratio was present with invariable speed of image data input and output, so a full and feasible scheme was given and simulated with VHDL for airborne image coding and transmission. Furthermore, the whole scheme was implemented and verified with one chip of field-programmable gate arrays(FPGA) manufactured by Xilinx Corp. Results show the encoder meets the application of airborne image coding well in bulk, weight, and power consumption, and all key techniques in FPGA design are referred to.
Robust ellipsoidal state bounding algorithm
Chai Wei, Sun Xianfang
2006, 32(12): 1447-1450.
Abstract:
A numerically robust algorithm for computing ellipsoidal bounds on the state of a linear, discrete-time dynamic system was proposed. The algorithm employed ellipsoidal outer approximation of the feasible set assuming instantaneous process and observation noise vectors and the initial state to be bounded by known ellipsoids. The time and observation updates produced, respectively, the vector sum and intersection of two ellipsoids. Cholesky decomposition was used in the propagation of the shape-defining matrix of the ellipsoid to keep it positive definite in the presence of roundoff errors. Besides, a subminimal-volume ellipsoid was selected from a family of ellipsoids as the observation-updated ellipsoid to circumvent the complex optimization affected by ill-conditioned matrix inverse. Monte Carlo simulations on a digital computer were performed to compare the performance of the proposed algorithm with that of the optimal algorithm. Simulation results show that the proposed algorithm not only matches the performance of the optimal algorithm closely in terms of ellipsoid volumes and mean-square errors, but also is less vulnerable to roundoff errors. The proposed algorithm also features the capability to be realized on a parallel computer.
Design and realization of coder in missile IFF system
Fang Huimin, Li Dongguang, Shi Gengchen
2006, 32(12): 1451-1454.
Abstract:
One of the key technologies in the missile IFF (identification friend or foe) system is the encrypting transmission for the questioning and answering signals. To meet the ciphers requirements with larger capacity and stronger randomicity in the system, the M-sequence was introduced and its characteristics were analyzed. With the cut-join sieve method and the microcontroller, a coder was proposed. The principle diagrams and working process were analyzed. The generating flow chart on the intersecting line pairs of each layer was given and the five-level M-sequence circuit unit working process was analyzed. The software and the hardware were debugged. The coder could generate and store all five-level M-sequences. The ciphers capacity is 2048. The ciphers length is 32. The sequence waveforms of the coder and the stored contents in E2PROM(electrically-erasable programmable read-only memory) were given and their characteristics were analyzed. The experimental results show that the method is valid and the designed coder can work well.
Active spherical joint for modular reconfigurable mobile robot
Deng Zhicheng, Wang Wei, Zong Guanghua
2006, 32(12): 1455-1458.
Abstract:
The present reconfigurable robots have several shortcomings about workspace and output torque in the pose-adjusting mechanisms. Aiming at these problems, a novel active joint was developed, which took advantages of the parallel mechanism and the serial mechanism and had characteristics of high output torque and large workspace. The parallel part is able to pitch and yaw ±40° with 17.3 N·m output torque and the serial part can rotate 360° with 4.5 N·m output torque provided. The application of this mechanism to mobile robots will highly enrich the configurations of the robots, and consequently develop their adaptive abilities to environments. The kinematic and workspace analysis were showed. The drive torque of the joint was tested, and it′s functionalities experimentally using the robot—JL-I were verified.
Development of bluetooth technique in industrial control system
Ma Fangkui, Huan Ji
2006, 32(12): 1459-1462.
Abstract:
To solve the requirement problem of modern industrial control system to wireless communication technology, the bluetooth protocol was analysed and the integration and development of bluetooth wireless communication technique in industrial device control were introduced, which included accessing the bluetooth chip by UART (universal asynchronous receiver/transmitter) of using HCI(host controller interface) command packets, event packets and data packets. The two steps of establishing bluetooth wireless net are necessary: the master finds slave and the connecting between master and slave is established. A remote operating panel of numerical control machine tool based on bluetooth was designed, the cable was replaced by bluetooth, which included the system function, such as automatic connection, mode selection and over-time alarm. The format of data packet by using wireless communication was designed, and the encode and decode of electro-handwheel pulse were analysed.
New manipulator calibration method based onscrew theory and distance error
Shao Zhiyu, Sun Hanxu, Jia Qingxuan, Ye Ping
2006, 32(12): 1463-1467.
Abstract:
The installation of a sphere-wrist at the end of the manipulator is acommon characteristic of many robots. The sphere-wrist can be regarded as an important independent structure of a manipulator. Static errors of sphere-wrist will affect the pose precision of the end effector. Taking sphere-wrist as study object, a comprehensive criterion to evaluate its precision was presented on the basis of the analysis of static errors. Using this criterion, an optimization model was constructed to rebuild the model of the sphere-wrist that had static errors, and hence a new kinematic model of the sphere-wrist was constructed. When this new model was used in the kinematic and dynamic computing, the pose error of the sphere-wrist could be reduced evidently. This optimization method will be more beneficial to a sphere-wrist with big static errors. By the partial optimization to the robot with a sphere-wrist, the kinematic accuracy of the end effector of the whole robot can be increased to some extent.
Investigation into elastic properties of anisotropic random foam model
Lu Zixing, Zhang Jialei, Wang Song
2006, 32(12): 1468-1471.
Abstract:
In order to investigate the influence of cell microstructure anisotropy on the mechanical properties with random model, on the basis of isotropic Voronoi random foam model, anisotropic open-cell and closed-cell random foam models were established through considering cell growth rate difference. The elastic properties of these models were analyzed by the finite element method. The relation between the relative Young′s modulus of the models and the anisotropic size ratio was obtained and compared with theory predicted results; the relation between the Poisson′s ratio and the anisotropic size ratio was also obtained and compared. The results indicate that the open-cell and closed-cell random foam model can reflect the cell anisotropic mechanical properties well, and the anisotropic mechanical properties of open-cell and closed-cell foam both have relation with relative density.
Improve electricity generation of microbial fuel cells by low intensity ultrasound
Yao Lu, Li Zhenglong, Liu Hong
2006, 32(12): 1472-1476.
Abstract:
It is possible to produce electricity in microbial fuel cells(MFCs) while accomplishing biological wastewater treatment, but slow electron transference limits the development of MFCs. To improve the electricity generation, two similar single chambered MFCs were built, which had the available volume 1.5L, and each electrode area was 160cm2. One was irradiated by ultrasound, the other used as control. The MFCs was induced by ultrasound at 33kHz in 10min with the ultrasound intensities of 0.2W/cm2 every 83 hours. The result shows that in the end of the reaction(about 2880h), the maximum power density of the ultrasound treatment reactor increases by 6% comparing with that of the control, and the total coulomb increases by 46.5% in one reaction cycle. The ultrasound treatment reactor′s Coulombic efficiency(CE) is 25.7% higher than that of the control. Moreover, in the MFCs with ultrasound, the lowest pH of wastewater is lower than that in the control, and the lowest oxidation reduction potential(ORP) of reactor is lower by 34.8mV. In 3000min the two reactors′ removal rate of chemical oxygen demand(COD) all reaches to 72.9%. The ultrasound irradiation doesn′t increase the removal rate of COD obviously. The explanation of these differences was given according to the influence of low intensity ultrasound to the microorganisms.
Industrial CT imaging method for large objects
Wei Dongbo, Fu Jian, Gong Lei, Jiang Ming
2006, 32(12): 1477-1480.
Abstract:
An industrial computed tomography(ICT) imaging method to enlarge the field of view was proposed to execute the rapid CT test of large objects. Its projection data rebin pre-processing method and filter back-projection reconstruction algorithm were deduced. The pre-processing method is from the fact that there exists the data redundancy for 3rd scan ICT. It creates the function mapping relationship between fan beam projections and parallel beam projections. This method can rebin the two groups of incomplete fan beam projections acquired by the detector at two positions into one group of complete parallel beam projections to meet the requirement of the reconstruction algorithm. The computer simulation results prove the validity of the proposed method to large objects. Analysis shows that its field of view is 1.8 times larger than that of 3rd scan ICT. This method can be implemented with the table with the transverse movement and the rotation movement and is easy to compatible with 3rd scan ICT without extra hardware requirements.
Irregular information distortion and weakening methods in supply chains
Wang Jing, Sun Haiyan, Li Yilan
2006, 32(12): 1481-1484.
Abstract:
Based on information theory,systems engineering and control engineering theory,the uncertain information distortion problem in a simple two-stage supply chain was studied for the purpose of improving the stability of supply chain system. Firstly, the uncertain information distortion was generally defined and analyzed from the viewpoint of information transferring and processing. Secondly, the ordering subsystem model of a simple two-stage supply chain was built. The system transfer function and frequency response characteristics were analyzed. Two scenarios were considered: one is the traditional supply chain in which the members do not share information, the other one is the integrated supply chain in which the end customer demand information is shared by all members. According to these analyses, the influences of information distortion on supply chain performances were discussed. Finally, the benefits of information sharing in supply chains were effectively measured by using information theory and control engineering approach.
Simplification of unclosed mesh models with geometry and property boundary preservation
Shen Xukun, Zhao Xuewei, Qi Yue, Cai Su
2006, 32(12): 1485-1489.
Abstract:
In practice, property information such as colors, textures, surface normals, etc. is necessary to represent 3D models besides geometry and topology information of triangle meshes, which will inevitably result in a large volume of 3D data as well as boundary edges and holes of mesh models. In order to decrease the data volume as well as preserve significant character of 3D models, an improved quadric error metrics and error control method were used to present a new simplification algorithm of unclosed mesh models based on triangle collapse. With the conception of geometry and property boundary, the original meshes were labeled as boundary, corner, interior or character triangles according to different boundary conditions, and constraint strategies were adopted to preserve appearance and boundary of the original models during the simplification process. In addition, a method to generate progressive meshes was given to provide a continuous multi-resolution representation of 3D models. The proposed method has been successfully applied to progressive transmission and presentation system of 3D models over the Internet.
Prototype selection of customized development process based on open source software
Wang Zhonglin, Yin Baolin
2006, 32(12): 1490-1494.
Abstract:
Selecting an appropriate prototype for customized development process will increase development efficiency, decrease development costs and shorten development time. Based on the COCOMO(costructive cost model) II model, a new software cost assessment method was proposed to analyze the influence of the key factors, such as the function differences, system performances and scale, stability, in the development process. The influences of the key factors on the equivalent code, which is essential in the cost estimation formula, were quantified. A practical project shows that the assessment error is about 15%, well within the 40% acceptable threshold in COCOMO II model.
Auto-generation and configuration of visual modeling language editor
Zhang Li, Jiang Ke, Gao Hui
2006, 32(12): 1495-1498.
Abstract:
Visual modeling language is a language, which uses graphics to describe the system or software, while visual modeling language editor provides support tool for it. The common between visual modeling language editors make it possible to use auto-generation and configuration. Based on years′ theory research and development experience on visual modeling language editor, a framework of visual modeling language editor development, which uses auto-generation combined with configuration, was proposed to support rapid development of editor. A description method of visual modeling language RM was defined, which supports static semantics. In RM, regular-based formalization description method is used to describethe syntax of visual modeling language and the features of editor, while the MOF(meta object facility) is used to describe the static semantics. Finally, the development environment Veda was designed and implemented, which verified the feasibility of framework and description method.
Investment externality and game strategies of network security
Lü Junjie, Qiu Wanhua, Wang Yuanzhuo
2006, 32(12): 1499-1502.
Abstract:
An investment game theoretic model was presented to study the externality in firms′ network security investment with different investment costs and profits.Taking virus contagion as an example, the negative investment externality exerted by the contagion between firms in the network was investigated. Under such an environment, the investment threshold and factors concerned such as contagion probability and the number of investing firms were computed to determine several Nash equilibrium solutions with externality representing the risk. The model was analyzed further when the risk was endogenous and the invest threshold was much more complicated than that in exogenous environment. This endogenous threshold is determined not only by the probability of contagion between firms but also by the sign and absolute value of externalities. This method provides a novel viewpoint to information security risk management and advices for firms′ decision on security investment and government policies to induce investment under externality.