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2003 Vol. 29, No. 7

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Calculation of range and endurance of jet aircraft at constant altitude
Zhang Yunfei, Guo Wei, Ma Dongli, Xiang Jinwu
2003, 29(7): 565-569.
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When the thrust coefficients of fuel consumption were constant, the calculation formulas of optimal cruise states (including posture and airspeed) were presented for long-range and long-endurance, and the calculation formula of range and endurance were given when flight strategy held airspeed or posture uniform. The results show that variable posture and airspeed are needed for long-range flight and changeless posture and variable airspeed are needed for long-endurance flight. The example expresses that when the flight parameter is close to the optimal ones, either changeless posture or constant airspeed flight can highly approach long-range or long-endurance flight. When the thrust coefficients of fuel consumption changing with airspeed, the above questions were studied also and the main processes of calculation were given.
Fuzzy basis function network based approach for fault information detection in unknown systems
Song Hua, Zhang Hongyue
2003, 29(7): 570-574.
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Fuzzy basis function network (FBFN) based on T-S fuzzy model is given. A general approach for fault information detection in unknown systems using FBFN is present. The unknown system is composed of known part and unknown part. The output of an actual system is composed of three portions: the output of a mathematical model, the output of unknown part and fault information. The known part can be represented by a mathematical model. The unknown part, which includes the uncertainty of model error, disturbance inputs, etc, is estimated by a FBFN. The fault information in the unknown system can be estimated using the outputs of actual system, the mathematical model and FBFN.A simulation example of fault information detection in a microwave landing system of an aircraft is given.
Research on relation between crack extension resistance curve and sample thickness
Yang Jiyun, Zhang Xing, Zhang Min
2003, 29(7): 575-578.
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A mathematical formula for the relation between resistance curve of crack extension and sample thickness was obtained in fracture mechanics, based on the theoretical resistance curve of crack extension which was provided in the previous work. Some parameters in the formula were determined by the least square method. The resistance curve equation of specimen with arbitrary sample thickness can be calculated by this method. The mathematical expression is verified by test results and additional data may be provided by this expression for complementing the current handbook.
Singularity avoidance in redundant single gimbal control moment gyroscope systems
Wu Zhong, Chou Wusheng
2003, 29(7): 579-582.
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Single gimbal control moment gyroscope (SGCMG) is one kind of inertial actuators applied to the spacecrafts. Three or more SGCMGs are used in order to meet the need of the 3-axis attitude control. Singularity often arises when several SGCMGs work coordinately. A new detecting method of avoidability of singular states was proposed which was suitable for SGCMG systems. This approach can transform the problem of detecting avoidability/unavoidability to qualitative study on a set of nonlinear ordinary differential equations. Several examples indicate that the method presented above is feasible.
Analysis of optimal adjustment of turbofan engine based on trial center data
Zhu Zhili, Meng Fantao, Chen Baoyan
2003, 29(7): 583-587.
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A new optimal adjustment method of engine was discussed. Based on multi variables and multi objectives, this method can search out an optimal adjustment case to meet the design demand in use of the engine characteristic simulation model and the result of fault diagnosis. An engine adjustment model was build up and used to a turbofan engine in the state of test. The investigation shows that the optimal adjustment case can guide the adjustment of fault engine in the trial center.
Research on infrared stealth system for armed helicopter
Wu Zhenbo, Wu Zhe
2003, 29(7): 588-592.
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Based on the battlefield environment for performing operational mission, emphasis should be placed on the threat from infrared guided missile when conducting infrared stealth for armed helicopter. Modes and developing tendency of infrared guidance were introduced, calculation formulas of performance range of point-source and imaging guided missile were derived, and two approaches, theoretical analysis computation and flight measurement, of obtaining infrared radiation characteristic of armed helicopter were described. Effects of radiation intensity and difference in temperature on missile performance range were studied through samples. Infrared suppression effects and approaches were analyzed.
Study on method for processing image of strip in structured-light 3D vision measuring technique
He Junji, Zhang Guangjun
2003, 29(7): 593-597.
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In a structured-light vision system, the accuracy of center position of the stripe is of great importance for that of the whole measuring system. Processing the image of stripe is an important step, especially for images with serious noises. Methods for processing images of stripe disturbed by various noise sources were discussed, as well as the method for detecting accurately the center of stripes. A special filtering mask was submitted for "surrounding" disturbance and was verified effective. For the measuring range as large as 200mm×200mm the accuracy of the whole measuring system when using the methods mentioned is 0.083 mm.
Study of optimization method for flight path following
He Pei, Qu Xiangju
2003, 29(7): 598-601.
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Minimizing the tracking deviation between the real path and the referenced path can produce optimal following path, but it will bring a considerable oscillation of optimal control variables. In order to alleviate the considerable oscillation, a new integrated control method that combines the deviation with its differential was presented. The numerical application of the integrated control method demonstrates that the proposed method is effective and valid with respect to the possible oscillation of optimal control variables. Consequently, the precision performance of the flight path following is further realized.
Research on dynamic virtual prototyping of aircraft
Liu Jie, Peng Xiaoyuan, Liu Li
2003, 29(7): 602-606.
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Virtual prototyping(VP) is a new technique in design and manufacture. Dynamic virtual prototype has some key techniques, such as the highest model, real time running architecture and normative data structure, etc. A basic study of dynamics VP was accomplished, and a simple and clear environment of the complex dynamic VP for designing, developing and integrating was submitted. A deep study was thrown into the collaboration simulation environment that based on run time infrastructure(RTI),and a data-gateway was used to deal with high real-time system. The characteristics and key techniques of dynamics VP were summed up.
Research on high-efficiency arithmetic to improve ray trace method
Huang Peilin, Wu Zhe
2003, 29(7): 607-610.
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A new technique named local aperture grid optimization arithmetic was presented to improve the efficiency of the classical method. The chief aperture that contains all the rays in the incident field was divided into local aperture grids, on which selected sampling rays was calculated to determine its contribution level.Pre-defined calculation level was used to determine whether to calculate the rest rays on the local aperture or not. Therefore the rays that have no or little RCS contribution were neglected and the calculating time consumed on intersecting judgment was reduced. By programming examination, the optimization arithmetic was proved to be fairly precise and remarkably efficient, and also applied.
constant toolpath generation in NC machining
Yan Guangrong, Zhu Xinxiong, Bai Juntao, Lei Yi
2003, 29(7): 611-615.
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Appealed by high-speed Z -constant machining with high quality, an algorithm of generating Z -constant toolpath in NC machining was presented based on the cutter location surface and its Zmap model. It suggests guarantees that the toolpath of climb cutting can be obtained in consideration of the cutter location surface Zmap model features, thus to gain a qualitied surface. This method was realized successfully in business software:CAXA-ME,which with satisfying computing speed and stability.
Thermal design technology of space suit used for extravehicular activity
Qiu Yifen, Yuan Xiugan, Mei Zhiguang, Sang Minjing
2003, 29(7): 616-619.
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Contents about the title were presented, and the current situation was reviewed in this field. Three mathematical simulation models were analyzed, they were mathematical simulation of two-dimensional human thermalregulation system in wide temperature range, the finger temperature field simulation and the heat and mass transfer analysis of liquid and ventilation cooling garment (LVCG) used for extravehicular activity (EVA). The simulation model used for thermal design technology of space suit was developed based on three models related above. Thermal physiological experiment research was carried out to verify this model.
Research on improving the disturbance resistance ability of radioactive isotope aircraft fuel density measurement
Li Nan, Lü Junfang
2003, 29(7): 620-623.
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The aircraft fuel density measuring system by utilizing the radioactive isotope was introduced. A method of correcting the measuring data and a scheme of twin-detectors measuring system were led by efforts to solve the initial intensity fluctuation of the radioactive source in the measuring procedure. Then the principles of these two solutions were discussed in detail.
Design and implementation of communication server on highway toll connection system
Fu Mengruo, Wu Jinpei, Zhang Qishan
2003, 29(7): 624-626.
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Communication server on highway toll connection system is the center of data transmission. The design, realization and characteristics of communication server were introduced. Based on designed protocol support packets priority, communication server exchanges data concurrently with end-users. Client/Server model was utilized to meet the need of centralized control of sharing data. Multithread programming technique was used to fulfill requirement of real-time. The system works satisfactorily at Guangzhou-Shenzhen highway.
B-P viscoplastic constitutive modeling of Udimet 720 Li
Shi Duoqi, Yang Xiaoguang, Wang Yanrong, Zhou Yanpei
2003, 29(7): 627-630.
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Udimet 720 Li is a Ni-based superalloy used for aeroengine disc. Based on the uniaxial tensile, cyclic loading and creep experiments results at 650℃, the Bodner-Partom unified viscoplastic constitutive theory was applied to model the mechanical behaviors of the material under three different loading conditions. After detailed analysis of constitutive characteristics of B-P model, a global optimized strategy for model parameters was given in order to simulate tensile, cyclic and creep curves simultaneously. The B-P model was implemented in ABAQUS soft ware through UMAT subroutine using a self-adaptive time stepping strategy. The results shows that B-P model is able to describe such kinds of mechanical behaviors, but it needs to be modified to model fast isotropic softening and ratchetting.
Study of grid security architecture
Liu Yiwen, Li Weiqin, Wei Wei
2003, 29(7): 631-635.
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The unigue security requirements of grids were described as well as the shortcoming of the existing technologies, a grid layered security architecture was developed which provides an integrated solution to fit all these grid security requirements, and some key techniques to achieve the grid security architecture such as single sign-on and security group communication were studied. Using this security architecture, a secure model for a shared electronic exchange was constructed which provides a security platform for electronic commerce.
Heat transfer in rotating cavity with axial throughflow of cooling air
Ning Lei, Ding Shuiting, Tao Zhi, Xu Guoqiang
2003, 29(7): 636-639.
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A test model of four co-rotating disks was developed as the simplified version of a typical internal cooling system of a gas turbine compressor. The investigation was on the distribution of local heat transfer coefficient and the averaged nusselt number of the downstream main disk. Experimental analysis may lead to following conclusions:the distribution is not of monotony and multi-peaks were found along the disk surface, u increases with the decrease of the rotational reynold number ( Re w), u increases with the axial reynold number ( Re ) and the grasholf number ( Gr ).
Study on an improved recursive partial least-squares modeling approach and application
Liu Qiang, Yin Li
2003, 29(7): 640-643.
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Based on the related partial least-squares (PLS) algorithms, a new improved recursive partial least-squares (SR-PLS) algorithm was derived. The SR-PLS simplifies the recursive computations by substituting the two principal matrices of the independent variables for the residual matrices directly. By using a computer simulation, it shows the consumed time using SR-PLS decreased greatly. The SR-PLS was implemented in modeling peak resultant cutting force of an NC machining process. The estimated outputs of the process model with the identified parameters were re-constructed, consistent with the measurement. The simulation and experiment demonstrate that the SR-PLS algorithm was correct and effective, with the advantages of less computation time, valid parameter estimation and small modeling errors. SR-PLS algorithm is suitable for the on-line modeling applications in the cases of large-scale measurement data and the requirement of high efficiency as well.
Error analysis of high-aspect-ratio finite elements for 2-D boundary layer simulations
Wang Hao, Wu Songping
2003, 29(7): 644-648.
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A new error analysis in finite element method, which is based on the element size in spatial directions respectively, was proposed. This analysis is different from the ordinary error analysis method, which is based on the overall size of elements. An error matching principle can be derived from the analysis presented here. The principle can be used in generating optimal grids and in analyzing the error of the calculation. A high precision finite element scheme was discussed upon the error matching principle, that uses the high order interpolation in the desired direction. The new error analysis method and the error matching principle were verified by the numerical tests. The results show that the proper grid sizes and right order of interpolation can minimize the error and improve the computational efficiency.
Techniques and developments of MPEG audio
Li Chao, Xiong Zhang, Ouyang Yuanxin
2003, 29(7): 649-653.
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Moving pictures experts group(MPEG) series standards have become one of the most popular families in the field of multimedia application. MPEG audio is an elementary part of these standards. With the normalization of new standards such as MPEG-4/7/21 in the recent several years, a novel multimedia application interoperability framework will be founded. However, many attentions should still be concentrated on improving the efficiency of audio coding and on mining more precise content-based description methods. A detailed review of the techniques and developments of MPEG audio standards was made, and possible problems of existing standards were pointed out. The conclusion and a brief description of the perspectives of MPEG audio were given.
Analysis of double-sided arc welding technology and physical process
Cui Xuming, Li Liuhe, Zhang Yanhua
2003, 29(7): 654-658.
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Double-sided arc welding (DSAW) is a new technology which has been utilized in recent years. It has many advantages such as increasing weld penetration, decreasing weld defects, reducing welding deformation, improving welding speed and saving power consumption. The basic types and technological mechanism of DSAW process were introduced. The mechanism of increasing joint penetration in single-power DSAW process was discussed. The welding mechanism of DSAW was revealed from arc physics side. The practical use of DSAW process would be improved.

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