Advanced Search

2011 Vol. 37, No. 6

  Previous Issue | Next Issue 
Display Method:
Virtual extension imaging applied to large FOV attitude angle measurement
Jiang Jie, Wang Haoyu, Zhang Guangjun
2011, 37(6): 631-634.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1642
Abstract:
Virtual extension imaging was proposed to apply to large field of view (FOV) attitude angle measurement based on photoelectric collimation and pinhole imaging theory. The FOV was virtually enlarged through multi-imaging. Based on the designed anisomerous pinhole diaphragm, an identify method for spot pattern was proposed to judge whether the spot was reflected or not, and to map the spot coordinate to expanded imaging surface. The identify result was analyzed and verified via the computer simulation. The results show that the design can identify diversified spot pattern exactly, which is high accuracy and large FOV for attitude angle measurement.
Simulation of G-loads in post-stall maneuver on sustained G-load flight simulator
Pan Wenjun, Wang Lixin, Tan Xiangsheng
2011, 37(6): 635-638.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1041
Abstract:
Methods of simulating G-loads in post-stall maneuvers on a novel sustained G-load flight simulator (SGFS) was studied. Considering features of intense angular motion of the aircraft in post-stall maneuvers, additional G-loads generated by the rotation of the aircraft were also counted in the calculation of G-loads on pilot, which was later employed in the mathematical model for SGFS G-load simulation. G-loads on pilot in a typical post-stall maneuver known as Herbst maneuver were simulated by using the model. SGFS tracked 3-axis G-loads command precisely with the maximal error less than 0.2g during the simulation. The results indicate that additional G-loads on pilot generated by aircraft rotation could not be neglected and show SGFS could meet the requirements of post-stall maneuver G-loads simulation.
Sensor fault diagnosis algorithm based on adaptive UKF
Hu Di, Dong Yunfeng
2011, 37(6): 639-643.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1094
Abstract:
To the questions of the abnormal values and the instruments failures for the nonlinear sensor measurement systems, a robust fault diagnosis algorithm based on adaptive unscented Kalman filtering (UKF) was proposed. An adaptive matrix was produced according to the innovation of UKF, then a systems- detector and a parts- detector were built which were made use of restraining the abnormal values and diagnosing the instruments- faults respectively. The innovation of UKF was introduced to status prediction by the adaptive function for modifying the error efforts between the abnormal values and status predictive values and achieving the systems- robust, which was called systems- detector. The innovation was separated into the different sensors- parameters to produce adaptive matrix, which was formed the parts- detector. The trace of adaptive matrix was made use of detecting whether a fault or not and isolating the faults. The simulation results show that the algorithm is robust to the abnormal values, and is accurate to detect the faults from the sensor instruments and compute the range of faults at the same time. The structure of the algorithm is simple and less computational load, and is a good reference for engineering application.
Match features of aircraft-carrier parameters during ski-jump takeoff
Liu Xingyu, Xu Dongsong, Wang Lixin
2011, 37(6): 644-648,653.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1028
Abstract:
The influence of primary aircraft-ramp parameters on ski-jump takeoff safety was analyzed by numerical simulation. The match set of primary parameters that satisfy the takeoff safety criteria was computed and the match law was summarized. The results indicate that the takeoff mass is the primary effect factor of flight path descent. Enhancing preset elevator angle and ramp angle can help to decrease the flight path descent. The preset elevator angle influences the attack angle. Too large preset elevator angle would lead to stall. The ramp angle influences the pitch rate, which attains its peak value when ramp angle is 12°. Within the boundary of the match set, the range confined by preset elevator angle and ramp exit angle decreases with the increase of takeoff mass.
Prediction of lateral liquid sloshing force of tank based on neural networks
Kang Ning, Jia Jia, Liu Xi
2011, 37(6): 649-653.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 817
Abstract:
Numerical simulation of liquid sloshing force under lateral acceleration of reference tank was conducted with volume of fluid (VOF) model of fluent software. Liquid filling ratio, forces, acceleration were set as inputs, while forces after a few seconds as target outputs. Reasonable distributed results were selected as training samples to establish prediction model of liquid sloshing forces acting on the reference tank. This trained BP neural networks were tested by 158 various samples. The maximum prediction errors of vertical force, lateral force and lateral moment were 8.88%, 0.36%, and 1.38%. The magnitude and regulation of the modified time step and forces of reference tank are nearly the same as general cylindrical tanks; The magnitudes of forces are proportional to the length of cylindrical tank in lateral motion. Through revising the time step and forces of reference tank, the forces of general cylindrical tank can be predicted based on BP neural network. The study can provide the necessary data for the analysis of tank truck dynamics efficiently.
Technique of aircraft loads spectrum statistics based on kernel density estimation
Tang Ani
2011, 37(6): 654-657,664.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 785
Abstract:
Restricted by real condition, small sample method is usually used to measure the aircraft loads spectrum. The small sample data is a simple sample from the real matrix, which can-t ensure the adequacy and the integrity of data. The traditional average statistics method which is the common method to be used to develop loads spectrum can-t compensate for the defects of data. In order to overcome the shortage of small sample data, kernel density estimation was used to static loads spectrum, and better results were gotten. The basic theory of kernel density estimation was introduced and using the statistic of an airplane-s sinking velocity spectrum as an example to describe the mathematical course of kernel density estimation method on load spectrum statistics datailedly. The results show that kernel density estimation method has a good effect for restoring the original appearance of the load spectrum and can make up the shortage of small sample data.
Novel buck-boost converter based on Z-source
Qi Bojin, Du Qing, Zhang Jin, Ma Jun
2011, 37(6): 658-664.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 685
Abstract:
Basic non-isolated buck-boost circuit exists the problem of short-circuit ring caused by the diode-s reverse recovery. A buck-boost DC/DC converter based on Z-sourse was designed. The presence of short-circuit ring was avoided from the circuit structure. The step response of initial state of the Z-network and the converter were discussed. The pre-charge circuits was also designed. The voltage and current spikes when the converter started were also eliminated. The three operation modes and operation theory of the converter was analysed when it worked in the situation of inductor current continuous mode(CCM). The operation modes of the boost and buck mode were simplified according to the principles of optimal efficiency, thereby the control strategy was also optimized. A method was presented to ensure the converter worked in CCM through choosing the reasonable inductor ripple factor. The design rules of the components was also given. Smulation and experimental results coincide with the theoretical analysis.
Base excitation and load identification based on Craig reduction model
Zhu Siyan, Zhu Liwen
2011, 37(6): 665-668,679.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 761
Abstract:
Load identification use measured acceleration of few degree of freedom (DOF) to determine external applied load. Base excitation give movement upon foundation freedom to excite the structure, and then obtain the whole dynamic response. Making use of characteristics of Craig reduction model, and the known motion of interface DOF, the dynamic response of all other DOF could be calculated, thus the base excitation was achieved. The load identification could be performed through the dynamic equation with these motion of interface DOF and the calculated dynamic response of non-interface DOF. The only error of this method for base excitation and load identification is the difference between the Craig reduction model and the original finite-element model. For this reason, frequency response analysis was applied to determine the precision of Craig reduction model through the variation of the frequency response curve. An example was given to demonstrate the validity of the present base excitation and load identification method.
Computation of scatter characters of media target based on GRECO
Fang Ning, Wang Shuailei, Wang Gu, Wang Taosheng
2011, 37(6): 669-672.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 727
Abstract:
Among all the methods of computing the scatter characters of radar targets, graphic electromagnetic method and ray tracing technique are two valid ways in high frequency.A valid method was presented to combine these two ways. First, with the help of illumination model and automatic hiding in OpenGL, the shape of media target was shown on screen. The color and position information of each pixel could be obtained from the buffers to compute the first scatter effect and then the position and normal vector information was taken as the start point to calculate the multi scatter effect by the ray tracing technique. At last, adding the two components leads to the total radar cross scatter. The simulation of cylinder and sphere proves the validity and effectiveness of this method.
Methods of image processing for automatic grading of porosity defects in aeronautical alloy
Wu Xin, Qi Bojin, Zhang Jianhe
2011, 37(6): 673-679.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 822
Abstract:
Aiming at the disadvantage of manual grading of porosity in aeronautical alloy cast currently, a method of automatic grading by image processing and pattern recognition of computer to images got by X-ray radiography was put forward, and the methods of image processing and pattern recognition were mainly studied. According to the characteristics of gray distribution in typical porosity image, an algorithm of wavelet was taken to filter the disturbance of low frequency, which can remain the information of high frequency. Then segmentation was taken to pick up the porosity region and dimension characteristics of single porosity further, and macroscopic statistics and analysis was carried out. Neural network training was adopted by standard images from first level to eighth level, and finally the automatic grading of porosity was realized. The experimental results show that the method of image processing has good adaptability.
Rapid wing structural finite element modeling and automated adjustment
Luo Mingqiang, Feng Haocheng, Liu Hu, Wu Zhe
2011, 37(6): 680-684.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1308
Abstract:
In order to improve the quality and efficiency of civil airplanes conceptual and preliminary design, the method of wing structural finite element modeling and automated adjustment in a computer aided aircraft conceptual/preliminary design system called open conceptual aircraft design system(OpenCADS) which organizes data in an object-oriented approach was studied. The equivalent method of wing structural finite element modeling using beam elements and shell elements in conceptual design was proposed. The finite element nodes which were calibrated by ribs and number rule of the elements were defined. The organization and application logic of related data classes was designed and wing structural finite element modeling and automated adjustment were implemented which laid the foundation for multi-disciplinary design optimization in aircraft conceptual design phase. An example was presented to illustrate the effectiveness and reliability of the method proposed.
Numerical analysis of high-temperature-gas wind tunnel thermal characteristics
Yao Feng, Dong Sujun, Wang Jun
2011, 37(6): 685-689,694.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 740
Abstract:
An experimental method using subsonic high-temperature gas flow to simulate aerodynamic thermal environment of near space hypersonic vehicle was introduced. In the test section of the experiment equipment, the room temperatwe air was ejected by the subsonic high-temperature gas flow to make the heat distribution of the experimental condition in line with that of the real flight condition on the cap. 13 experimental conditions were analyzed using computational fluid dynamics(CFD). The numerical analysis verifies the feasibility of the experimental method and provides basis for demonstration of the experiment facilities.
Method to analyze the impact of maintenance and support process based on neural network
Wen Jingqian, Li Qing, Zhao Qingbin
2011, 37(6): 690-694.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 824
Abstract:
To solve the problem in determining key influence factors of maintenance and support, a new quantitative method was put forward which takes the support service processes as analysis object. In this method, the relation function between the influence factors and equipment performance was established, and the definitions of the influence degree, key element, key influencing factors and the combined influence degree were given out. To analyze the maintenance and support ability of manufacturer, the account, efficiency and stability of support processes were used as assessment indexes. Based on back-propagation neural network, the approximation solution for the relation function was calculated out by MATLAB software, which provided a computer realization to find out the key process and key influence factor for the producer. An application of certain aircraft manufacture was given to demonstrate the process analysis result. Compared with the expert grading method, the result obtained by this method is more objective.
Efficient design of multi-rate low-density parity-check code decoder
Zhao Ling, Zhang Xiaolin, Hou Yi
2011, 37(6): 695-700.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 778
Abstract:
An efficient partially parallel decoder architecture suited for multi-rate low density parity check(LDPC) codes was presented. Algorithmic transformation and architectural level optimization were incorporated to reduce the critical path. The check node updating units (CNU) and the variable node updating units (VNU) were divided several smaller parts, which are dynamically grouped under different code rate according to the row the column weights of check matrix. This method brings in great redundancy reduction of CNU and VNU, and the decoding rate was increased significantly for the small row-weight (column-weight) codes. Based on the proposed architectures, a 7k-lenth multi-rate LDPC code of rate 0.4, 0.6 and 0.8 decoder was described using verilog hardware design language and implemented on Altera field programmable gate array (FPGA) Stratix EP1S80. The implementation results show that this multi-rate decoder is just 12% larger in logic core size than a single rate decoder. Compared with the conventional partially parallel decoder, this decoder increases the throughput of rate 0.4 code is increased by 100% and rate 0.6 code by 50% without any hardware resource incensement and performance loss.
Hybrid RANS-LES method applied to backward facing step flow
Wu Jingfeng, Ning Fangfei
2011, 37(6): 701-704.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 774
Abstract:
Turbulent flow over a backward facing step was simulated using a hybrid Reynolds averaged navier stokes (RANS)-large eddy simulation(LES) approach, and the results were compared with experimental data. The hybrid system combines delayed detached-eddy simulation (DDES) with an improved RANS-LES hybrid model aimed at wall modeling in LES (WMLES). It ensures a different response depending on whether the simulation has inflow turbulent content. In the case of with inflow turbulent content, the WMLES branch of the system is active: most of the turbulent is resolved expect the flow near the wall. In the other case, the DDES branch of the system is active,i.e., it gives a pure RANS solution for attached flows and a DES-like solution for massively separated flows. In the system, a scheme which combines the upwind low-diffusion flux-splitting scheme and fourth-order skew-symmetric scheme was used as the convective flux scheme. The spalart-allmaras(S-A)model was applied as a subgrid scale(SGS)model. The definition of the subgrid length-scale was new which depends not only on the grid spacing, but also on the wall distance.
Biased Monte Carlo method for reliability sensitivity analysis
Li Jinghui, Kang Rui
2011, 37(6): 705-710,716.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 981
Abstract:
The likelihood ratio (LR) method was chosen as the basic derivative/gradient estimation method for reliability sensitivity analysis. The implementation of the LR method in crude component-based Monte Carlo (MC) and especially in the setting of classical reliability was first derived. To speed up the simulation, a biasing technique was then developed, which defines an unbiased importance sampling estimator based on system structure functions, and identifies the optimal set of biasing parameters via minimizing the variance of this estimator. One important advantage of this estimator is that, the task of minimizing its variance can be achieved by optimizing at the component level, thus avoiding the difficulty of high dimensional optimizations. A simple example with analytical solution available was studied to test the effectiveness of the LR method for reliability sensitivity analysis, and also the effectiveness of the proposed biasing technique for reducing the variance of LR derivative estimators. The results show that, the proposed biased MC method produced accurate estimates for all the quantities, and achieved at least six orders of magnitude of variance reduction for all of them, compared to crude MC．
Modeling and analysis of collaborative maintenance process based on synthesis of Petri net
Yang Yuan, Li Fang, Hou Chongyuan, Yang Lei
2011, 37(6): 711-716.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 723
Abstract:
To deal with some classical characteristics and problems during collaborative maintenance process such as shared resource constraints, complicated handover about maintenance tasks and uncertain maintaining time, a method based on synthesis Petri net for modeling collaborative maintenance process was put forward. The three parametric array was applied to depict fuzzy maintenance time. Activity graphic ideas was introduced to describe interface information about collaborative units. The dispatching rule about shared resource was utilized to form a control net to avoid the conflict with limited resources. The construction algorithm of the synthesis Petri net for the collaborative maintenance process was shown. This method can solve the three major difficulties of the collaborative maintenance process analysis and give a reasonable interpretation on the dependency relationship of collaborative maintenance activities. The model is constructed which can be conducive to achieve the standardized description of the collaborative maintenance process. The example shows that the model is effective to predict completion time of collaborative maintenance and grasp the timing about handover of maintenance tasks and give the proposal of the optimal allocation on shared resources.
Simulation on performance and effects of parameters analysis on three-bed OBOGS
Wang Huidan, Lin Guiping, Wang Liang, Fang Ling
2011, 37(6): 717-722,732.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 805
Abstract:
A set of mathematical models was built and utilized to simulate the performance of three-bed on-board oxygen generation system (OBOGS). Then the results of simulation were compared with the data from experiments and the good agreements were obtained to validate the models and simulation process. Based on the validated simulation, the performance of the OBOGS at different flight altitudes and in different operation conditions were predicted by simulation, and effects of some design and operation parameters such as product flow rate, feed pressure, purge orifice size and cycle time were investigated. It provides a guidance of design and optimization for three-bed OBOGS.
Base on semi-optical path difference of antenna reflector surface accuracy detection
Zhou Guofeng, Li Xiaoxing
2011, 37(6): 723-727.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 843
Abstract:
The selection of minimum value of surface fitting is one of the key technologies refer to the antenna panel surface detection. The antenna surface root-mean-square of semi-optical path difference is an index of antenna surface accuracy. A direct calculation method of semi-optical path difference (OPD) was presented according to the geometric definition of conic surface and its optical properties. The nonlinear least squares curve fitting algorithm based on the semi-optical path difference was described. Employing a parabolic reflector panel as the sample, through simulation and actual measurements, the fitting results were contrastively analyzed while selected axial deviation and semi-optical path difference as minimum value respectively. The experiments verifying the fitting method based on semi-optical path difference is more precision and stability.
Polynomial calibration method for millimeter-wave reflectometer
Zhao Xin, Liu Jinyang, Miao Jungang, Jiang Jingshan
2011, 37(6): 728-732.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 731
Abstract:
In order to measure the accurate reflection coefficient of waveguide component at millimeter-wave band, a method for reflectometer calibration was proposed. The calibration method was based on a polynomial error model, making the solution of each error term transformed into a problem solving the center of a circle trace, without reducing the solution precision. The method adopted a sliding load, a sliding short and a short circuit, thus reduced the requirements of standards in the millimeter-wave band. In experiment, a Ka-band reflectometer was built, the errors- solving processes and physical meanings were presented. After calibration, measurement results from reflectometer and vector network analyzer (VNA) were compared, and good agreement was achieved. Measurement results of a W-band corrugated horn were also compared, which further validate the method.
Experimental based traffic flow detectors data accuracy evaluation
Zhai Yaqiao, Weng Jiancheng, Rong Jian, Liu Xiaoming
2011, 37(6): 733-737,742.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 937
Abstract:
Considerable errors exist in the road speed data obtained from various detectors and directly influence the accuracy.Various traffic models were established for estimation. 12 groups of field experiments on different classes- roads by using a test vehicle with global positioning system(GPS) modules were implemented. Through combining automatically recording and manually recording, the accuracy discrepancy of travel speed data collected by floating car system, microwave detectors, and loop detectors was attempted to verify. The results analysis shows that the average error rate of travel speed of floating cars at road section on urban expressways and arteries are 13.6% and 27.8%, and the acquisition data and the actual speed have the same distribution. Microwave detector on expressways and loop detectors on arteries are 30% and 56%. Even though the section velocities of the microwave detector have some errors, which could more or less describe the basic driving conditions. Thus, results provide some evidences for selecting appropriate traffic model decided by accuracy. Moreover, it provides evidences for the application of different dimensions information in multi-source data fusion for higher accuracy.
Flow and heat transfer characteristics in laminar flow through random rough microchannels
Miao Hui, Huang Yong, Chen Haigang
2011, 37(6): 738-742.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 760
Abstract:
The flow and heat transfer characteristics of water in laminar flow through random roughness microchannels were investigated numerically. Two random rough microchannels were modeled by a simple method. And another microchannel was designed with periodically distributed roughness for compare. The Re range was 100~2 000. Results show that the Poiseuille number (Po) and the Nusselt number (Nu) in three rough microchannels are all larger than that in smooth channels significantly, and increase slightly with Re. In addition, Po and Nu in random roughness microchannels are all smaller than that in regular roughness microchannel. It could be concluded that the effect of roughness on local Nusselt number is attributed to the variation of velocity and the intersection angle between velocity and temperature gradient together.
Method based on fuzzy evaluation and GIOWA operator fortechnical risk assessment
Feng Zhen, Deng Zhongmin, Wu Qiang, Huang Xiaofeng
2011, 37(6): 743-747.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 737
Abstract:
The purpose was to present a qualitative and quantitative integrated approach to assess technical risk in aircraft type development project, with multiple attribute decision making methods introduced into it. A fuzzy syntheses evaluating system based on the generally induced ordered weighted averaging (GIOWA) operator was adopted to aggregate the fuzzy linguistic evaluating information used in risk assessment. By quantifying the possibility and consequence respectively, as well as employing risk matrix, the rank of each technical risk scenario was determined, and the whole project-s risk status was evaluated. Finally, a technical risk assessment example for aircraft development project was analyzed to illustrate detailed steps and feasibility of the method given above. It can provide an approach for technical risk assessment in the process of aircraft type development.
Fuzzy parity equation based fault diagnosis approach for PL/INS navigation system
Jin Xing, Song Hua, Qiu Hongzhuan, Wang Yangzhu
2011, 37(6): 748-752.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 751
Abstract:
A method for multiple faults identification for pseudolite (PL)/ inertial navigation system (INS) tightly coupled navigation system was presented. The failures associated with PL and their modes were analyzed, what is more, fuzzy parity equations were used to identify the PL failure modes. First of all, the PL/INS tightly coupled navigation system was described by a Takagi-Sugeno (T-S) fuzzy model, and then the full de-coupled parity equations were applied to the local linear models. The faults can be detected by the sum of the local residuals and Kalman filter algorithm was used for identifying the parameters of failure modes. Besides, the necessary conditions for parameter identification were given. The simulation results show that, in case of multiple signal faults and multiple types of fault in PL simultaneously, this method can effectively detect them and precisely identify the parameters of failure modes.
Coking properties of aircraft engines- nozzles
Huang Yanfei, Zhu Yuelin, Xiong Changjian, Pan Yingjie
2011, 37(6): 753-756.
Abstract References Relative Articles Resource File Access Statistics iconViews $!{v.htmlCount} iconDownload 1466
Abstract:
In order to solve the problem of air safety and service lives of the aircrafts with a mass of coking, the properties and micro-morphologies of coking which generated on aircrafts engines- nozzles when aircraft fuel combusted were researched. The properties of coking were characterized by the techniques of scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy disperse spectroscopy(EDS) and X-ray diffraction(XRD). It is found that two coking morphologies are produced: one is filamentous coking, and the other is granular coking. On the one hand, the filamentous coking only appears on the smooth surface of machine parts which includes short fiber filamentous coking and amorphous filamentous coking. It is generated by metal catalysis reaction and its formation has close connection with machine parts- structures, materials and surface. On the other hand, the granular coking, including aggregative granular coking and dispersive granular coking, mainly emerges on the surface of nozzles- pistons and it is aroused by the interaction of catalytic reaction and thermal cracking.

Copyright © Journal of Beijing University of Aeronautics and Astronautics

Address: Editorial Department of Journal of Beijing University of Aeronautics and Astronautics, 37 Xueyuan Road, Haidian District, Beijing Post Code: 100191 Email: jbuaa@buaa.edu.cn

Supported by: Beijing Renhe Information Technology Co., Ltd.