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2012 Vol. 38, No. 9

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Real-time path planning to track moving target in complex environments for UAV
Liang Xiao, Wang Honglun, Cao Menglei, Guo Tengfei
2012, (9): 1129-1133.
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In complex environments, when unmanned aerial vehicle (UAV) tracks a moving target, there are some defects on real-time capability and feasibility in the existing algorithm of path planning. A new heuristic direction of the rolling window was designed to make route search and track moving target. In the rolling window, the stream function was utilized for avoiding obstacle. To satisfy the constraints of UAV, the rolling window was triangle, also with adaptive function. In potential flows, a potential function was proposed to overcome the trap of terrain, and the route was smoothed. The simulation results show that this hybrid method could reduce the time and space complexity, and find a satisfactory route for UAV in complex environments when tracks moving target.
Observability analysis of transfer alignment of airborne weapons
Qin Feng, Zhan Xingqun, Zhan Lei, Zhang Yanhua
2012, (9): 1134-1138.
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The velocity and attitude selected as measurements were used to design transfer alignment system of airborne weapons. The dynamic error models and measurement models of system were established, and Kalman filter was designed based on these models. The observability analysis of piece-wise constant system (PWCS) based on singular value decomposition (SVD) of observable matrix was introduced. By using this method, the observability of every state vector in the transfer alignment of airborne weapons can be analyzed. Based on observability analysis of system, unobservable state vectors were omitted and the dimension of Kalman filter was reduced. At the same time, the filter performances and transfer alignment precision before and after reducing dimension were compared under wing rock maneuvers. The results of comparison can effectively prove the necessity and rationality of observability analysis.
Calculation and analysis of electric-powered helicopter flight performance
Nie Zi, Chen Ming
2012, (9): 1139-1143,1153.
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Based on the traditional method, a calculation method of electric-powered helicopter flight performance was proposed, which combined with the features of electric-power system and the characteristics of helicopter preliminary design. The influence of different variables and parameters on flight performance was analyzed. By taking a small-scale helicopter as an example, the flight performance before and after was calculated and compared. The calculated results and analysis show that electric-powered helicopter with short endurance due to battery technology limitation has higher ceiling. Compared with light and medium helicopter, micro and small-scale helicopter have a lot of advantage and latent capacity. This method is applicable to electric-powered helicopter preliminary design and parameter selection, which is also significant for helicopter.
Error analysis of space stabilized strap-down inertial navigation system on stationary base
Sun Feng, Wang Gen
2012, (9): 1144-1148.
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In order to satisfy the technical index of strap-down inertial navigation system and the precision of inertial components, the error propagation characteristics of the space stabilized strap-down inertial navigation system have been analyzed. The scheme of space stabilized inertial navigation system was proposed. According to the analysis of stationary base error equations, the impacts of gyro drift and accelerometer errors on space stabilized inertial navigation system were researched. Theoretical analysis and the experiment show that, the longitude error increased gradually based on the gyro constant drift, the other parameters accumulated base on the Schuler and Earth circle.
New techneque for multi-missile cooperative localization
Liu Juncheng, Zhang Jingjuan, Tan Lifen
2012, (9): 1149-1153.
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One of the key technologies in multi-missile cooperative combat (MCC) is the missile precision positioning technology. In the environment of system-of-systems combat, multi-missile cooperative localization (MCL) based on mutual rangings was proposed to improve the inertial positioning accuracy of the missile community. The cooperative localization system, which is mainly composed of the missile-borne data link and inertial navigation system (INS), was designed and the ranging scheme of the data link as well as the time synchronization problem was analyzed. The weighted rank-defect network adjustment algorithm was applied to estimate the inertial positioning errors. Simulation results show that the method slows down the divergence speed of positioning errors and improves the positioning precision effectively. The positioning precision comes higher with the increase of missiles and it is more than 2 times of the original level when the number of missiles is more than 4.
Controller design for limit protection of aero-engine based on ADRC
Wang Yuan, Li Qiuhong, Huang Xianghua, Zhao Yongping
2012, (9): 1154-1157.
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This controller is designed to monitor and control the specific variables while the aero-engine is running. It can perform engine protection if the signals exceed their maximum allowance. The active disturbance rejection control (ADRC) was proposed to design the limit protection controller. Advantage of the extended state observer was taken to estimate the model uncertainty and external interference of the system. The control signal was compensated through feedback. Fast protection was gotten when exceeding occurs, and safety was improved. Simulation results show that the ADRC limit protection controller can transmit the error of over limit to reference signal adjustment of the main loop very well. The overall control system responses quickly, and can carry the point of limit protection.
Design of multi-stage nested wiener filter employing Krylov subspace for anti-interference
Fan Guangwei, Yu Baoguo, Deng Zhixin, Yang Peng
2012, (9): 1158-1162.
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Space and time anti-interference for global navigation satellites system (GNSS) receivers requires good real-time processing ability. This limits the application of conventional matrix inversion algorithms due to their large amount of computation. Based on the analysis of the principle of multi-stage wiener filtering and combined with Krylov subspace nature, a multi-stage Wiener filter was designed for GNSS receivers. In this way, a reduction of filtering dimensions in Krylov subspace was achieved and the intensive computation for matrix inversion was avoided. Simulation results show that the proposed method can effectively reduce the amount of STAP algorithm computation with no anti-interference performance being affected and is more appropriate for real-time applications.
Simulation method of ionospheric effects on spaceborne SAR using multiple phase-screen technic
Li Li, Zhang Yongsheng, Dong Zhen, Liang Diannong
2012, (9): 1163-1166.
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Spaceborne P band SAR echo affected by the ionosphere was simulated using a multiple phase screen (MPS) method. Ionospheric dispersion effects, phase scintillation and amplitude scintillation were included in the simulated echo. The ionosphere was modeled into several thin screens which only changes phase of the signal. Phase scintillation and amplitude scintillation were realized by diffraction effects in vacuum between phase-screens. Diffraction result was reached by solving a parabolic equation of a sphere wave under an inclined incident condition. Ionospheric dispersion, phase scintillation and amplitude scintillation were included in the signal complex amplitude propagating through the multiple phase-screens. Echo spectrum was simulated by multiplication of the transmitted signal spectrum with the ionospheric effected complex amplitude. Simulation results show that the ionospheric dispersion effect, phase scintillation, amplitude scintillation can be included in the echo by the new method. Veritable and reliable data of ionospheric affected spaceborne SAR can be available for further study.
Analysis methodology of interference from radar to spectrum spread communication system
Wang Lei, Xie Shuguo
2012, (9): 1167-1171.
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Radar is one of severe interferences for spread spectrum communication system. A time-symbol level interference analysis methodology from radar to spread spectrum communication was proposed. Firstly, the electromagnetic interference mechanism from radars to spectrum spread communication system was analyzed based on time-symbol level, and the error bit rate formula of spectrum spread communication system in the presence of pulse radars interference was concluded. The performance of interference from pulse radar to spectrum spread communication system was simulated by the radar electromagnetic interference model, which proved the theory analysis result. Finally the frequency-distance relationship of five general radar and spread spectrum communication system in microwave band was calculated. The results show that this interference analysis method well exhibits the interference essence of radar and improve the frequency utilization efficiency.
Reduction of PAPR using companding with pre-distortion
Li You, Zhang Xiaolin, Xiao Xin
2012, (9): 1172-1175.
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To solve the conflict between peak to average power ratio (PAPR) and bit error ratio (BER) in companding, a joint companding pre-distortion (PD) method was proposed. The closed form expression of subcarrier signal to noise ratio (SNR) of orthogonal frequency division multiplexing (OFDM) signal, which was distorted by nonlinear power amplifier, was deduced under additive white Gaussion noise (AWGN) channel using Bussgang theorem. The nonlinear power amplifier was replaced by ideal PD. Then the linear companding was modified. The new expression of subcarrier SNR was obtained using three parameters of ideal PD and modified linear companging. The system BER was calculated by the new SNR. The simulation results show that, by adjusting the three parameters, the SNR threshold can be improved by 0.8 dB under the same PAPR reduction and BER.
Error correction code for Flash memory
Kang Wang, Zhang Youguang, Jin Lingxu, Wang Mingbang
2012, (9): 1176-1180.
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Flash memory is a non-volatile storage device, as the technology continuously scales down and storage density requirement increases up, the storage reliability and lifetime of flash memory become two of the most serious challenges. According to the multi-level cell (MLC) NAND Flash structural features and operating characteristics, an error correction coding approach based on orthogonal mapping was proposed, and the error correcting ability was analyzed. On this basis, two typical application scenarios in flash memory system were presented, i.e., distributed multi-user access storage and error-free recovery of historical data. Moreover, the lifetime of flash is strictly limited by the block-erasures operation; this coding scheme could utilize the bad block to enhance the flash lifetime. The analysis shows that this coding scheme could achieve multiple practical applications with simple adjustment to the encoder module.
Quaternion based switching filter for impulse noise removal in color images
Geng Xin, Hu Xiaoguang
2012, (9): 1181-1185.
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A novel color pixel distance based on the quaternion unit transform was proposed to quantify the intensity and chromaticity differences between two color pixels simultaneously. A quaternion switching filter was presented to suppress the impulse noise in color images based on the aforementioned distance and the property of image edge in both structure and direction. Each pixel in the color image was detected along four directions to determine whether it was noisy and only the noisy one was removed by the filter. The experimental result indicates that the proposed filter can suppress both correlated and uncorrelated impulse noise in color image while preserve image detail and has a faster execution speed than the traditional filters.
Dynamic phase-contrast microscopy of living cells by digital holography
Liu Shuo, Pan Feng, Xiao Wen
2012, (9): 1186-1188,1193.
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A digital holographic approach for dynamic phase-contrast microscopy of living cells was proposed. Fiber optic devices and individual optical components were adopted to set up a pre-magnified off-axis digital holographic imaging system. An infinity-corrected microscope objective was utilized to improve lateral resolution. Phase aberrations were compensated by using curvature matching lens and digital phase mask. The proposed method was used to investigate living samples of mouse osteocytes, whose movements and variations were indicated by phase-contrast images. The experimental results prove the feasibility of the proposed method.
ROSAR imaging algorithm based on frequency analysis
Yang Ke, Liao Guisheng, Xu Qing, Zhang Xiangyang
2012, (9): 1189-1193.
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In the existing imaging algorithms for synthetic aperture radar with rotating antennas (ROSAR), the methods based on the Taylor series expansion of the slant range suffer from mismatch problems in azimuth. In addition, the time-domain convolution method cannot rapidly correct the curvature. In the proposed ROSAR imaging algorithm in frequency domain, the echo was transformed into the two-dimension frequency domain directly using the stationary phase principle. In this case, spectral characteristics of the echo signal were retained completely. Thus, the correspondent decoupling function and matching function in frequency domain were constructed to achieve the range curvature correction and scene reconstruction. Simulation results demonstrate that the proposed algorithm can perform the curvature correction rapidly. Furthermore, the proposed algorithm can overcome the mismatch problems in azimuth effectively.
Design of decentralized robust attitude controller for hypersonic sliding vehicles
Li Jingjing, Ren Zhang, Shen Zhen
2012, (9): 1194-1199.
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Based on the mission and aerodynamic features of hypersonic sliding vehicles, the control-oriented model was built by taking first-order actuator dynamics into account. The decentralized robust attitude controller for re-entry flight incorporated the idea of decentralized control and sliding mode control was designed. And the decentralized robust sliding surfaces were designed using Tornambe control technique to ensure good tracking performance in sliding mode in the presence of coupling and unmatched uncertainties. The second order sliding mode control law was synthesized using modified sub-optimal control method in which the on-line estimate of equivalent control reduced chattering. Finally, a six-degree-of-freedom simulation in Simulink for a conceptual hypersonic sliding vehicle was performed, the robust tracking of guidance command is guaranteed despite of large parameter perturbations.
Evaluation method for the receiver sensitivity requirement of CATR with single reflector
Ou Naiming, Bai Ming, Liang Bin, Miao Jungang
2012, (9): 1200-1204.
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Based on the Lorentz reciprocity theorem, a novel method was proposed for evaluating the receiver sensitivity requirement of compact antenna test range (CATR) with single reflector. Through calculating the near fields that excited by the feed of the CATR and scattered by the standard calibration sphere respectively, and considering the efficiency of the reflector and the transmit power of the feed, the receiver sensitivity requirement in the testing process could be obtained. This method could reflect the influences of radar cross section (RCS) of the target, working frequency, the property and position of the feed, the size, sawtooth structure and edge diffraction of the reflector, the center position of quiet zone. This method was used to evaluate the receiver sensitivity requirement of CATR in microwave anechoic chamber of Beijing University of Aeronautics and Astronautics, and the evaluation result was compared with the experiment result, then the validity of this method could be verified.
Parameter matrix-based approach to computing all minimal hitting sets
Wang Dong, Feng Wenquan, Li Jingwen, Zhao Qi
2012, (9): 1205-1209.
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Computing all minimal hitting sets is one of the key steps in model-based diagnosis. Because of the limitations of parameterized algorithms and the low capabilities due to the expansion of state space in large-scale system diagnosis, a generalized minimal hitting-set algorithm named matrix-based minimal hitting set (M-MHS) algorithm was proposed. The parameter matrix was used to record the relationships between elements and sets, and the initial problem was broaken into several sub-problems by matrix decomposition. The computation of the sub-problems without solutions was avoided by the efficient prune rules. The simulation results show that all minimal hitting sets can be found. Compared with HSSE (hitting set-set enumeration) and de-parameterized BNB-HSSE (branch and bound-HSSE), the proposed algorithm has advantages in large scale computations and can keep relatively stable when data changes. The algorithm is a feasible means for computing all hitting sets in model-based diagnosis of large-scale systems.
Design of data-aided symbol timing and carrier synchronization loop
Yan Hui, Zhang Zhongpei
2012, (9): 1210-1213.
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Considering the problem of joint symbol timing and carrier estimation with high complexity for burst communication systems, a data-aided synchronization algorithm was proposed. First, the matched filter was implemented by the architecture of polyphase filter bank which avoids the use of interpolation filter. And then, the implementation and control of sample phase in polyphase filter bank was discussed. Second, a carrier synchronization estimator with optimal pilot placement was constructed based on the sum of autocorrelation function of the pilots, whose estimation accuracy can attain Cramer-Rao bound and has a low complexity. Lastly, the simulations were presented to verify the new algorithm performance. The results show the new receiver is easy to realize and can achieve perfect synchronization with a certain amount of pilots.
Correlation between Rayleigh-Somerfield diffraction and physical optics integration
Liang Bin, Bai Ming, Jin Ming, Miao Jungang
2012, (9): 1214-1218.
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To calculate the propagation of electromagnetic field in quasi-optics, the internal consistency and distinction between different approaches were researched respectively from Rayleigh-Somerfield scalar diffraction integration and vectorial physical optics integration. The two integration methods were firstly distinguished from physical conception, and then the consistency was discussed in the condition that electromagnetic field propagates between parallel planes. Propagation of the Gaussian beam was numerically simulated respectively by the two integration methods and compared with the analytical solution result. Precision of the two methods in handling problems of electromagnetic field propagation and different applications in vectorial diffraction problems was finally proposed.
GPS position solution algorithm based on the optimization theory
Zhao Xin, Qin Honglei, Lang Rongling
2012, (9): 1219-1223.
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In order to solve the problems of the traditional positioning solution methods, a new position solution method which was maximum a posteriori estimation based on the optimization theory was put forward. The basic principle of the method was introduced, and the derivation of the algorithm was detailed. The algorithm was from the joint probability density function of the system state variables, observation variables, and then transformed the estimation problem into optimization problem, using the solution of the optimization problem to estimate the state variables of the system. On this basis, simulation experiments had been used to show the effectiveness of the method. The experimental results show that the method can completely solve the nonlinear problem of the position solution, and have a high positioning accuracy.
Application of PS-InSAR to monitoring Berkeley landslides
Lei Ling, Zhou Yinqing, Li Jingwen, Rol
2012, (9): 1224-1226.
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To monitor Berkeley hills landslides,stacks of ERS1/2, Radarsat-1 and TerraSAR-X spaceborne SAR data ordered between 1992 and 2010 were utilized by an advanced interferometry method, persistent scatterer interferometry synthetic aperture radar (PS-InSAR). Differential interferometry processing was firstly made between one master SAR scene and all the other SAR scenes. The PS points were then selected by setting thresholds for both amplitude and phase part of SAR data. Based on the spatial and temporal characteristics of SAR differential phase, the deformation phase of PS points was filtered out. The results clearly locate landslides areas and the velocity maps of different SAR data show good consistence with each other.
Simulation of 94 GHz radial helix waveguide travelling wave tube
Wang Shaomeng, Duan Zhaoyun, Wei Yanyu, Gong Yubin
2012, (9): 1227-1229.
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A novel slow wave structure with low work voltage, high work current, compact structure was proposed by using radial helix waveguide.The dispersion and transmission character was analyzed, and its work voltage was obtained, which could be as low as several hundred Volts.As the emitter face of cylinder gun larger than ordinary TWT's, it is possible to produce a high current with low current density.The current can reach 30 A while the current density is 100 mA/cm2.The fabrication is easy as the large size in W-band and above.The good transmission character indicates that the study is valuable.
Selection for signals of opportunity based on affinity propagation clustering method
Zheng Lei, Zhang Jun, Xue Rui
2012, (9): 1230-1234,1266.
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The navigation method with signals of opportunity (SOOP) in the complex low airspace was introduced. Then a selection algorithm for SOOP was presented to solve the problem, which was hard to choose for the types of SOOP were various and the number of SOOP was so many. More less geometry dilution of precision (GDOP) for signals, the positioning accuracy would be higher. Consequently, the clustering method was considered to choose navigation signals because the signals in the same area influenced GDOP similarly. Firstly, each similarity between arbitrary two SOOP was expressed by their distance. Similar groups were acquired through the affinity propagation clustering method. Then, the groups were selected according to the centers of similar groups. Lastly, for navigation signals were chosen from the determinate groups. The simulation analyzed the rule of clustering for SOOP with different distributions. Then the algorithm simulation, which was applied in Wenchuan of Sichuan Province, proved the signal selection method effective. Meantime, this algorithm will greatly improve the efficiency of signal selection in the complex low airspace.
Content aware image distance measure for joint use of seam carving and non-homogeneous warping
Cao Lianchao, Si Nong, Gao Meiqin, Wu Lifang
2012, (9): 1235-1239.
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A content aware image distance measure for joint use of seam carving and warping was proposed. Firstly, important pixels in the original image were extracted. After a seam was removed, the important pixels were updated. For the preserved important pixels, the average difference of sub images (ADSI) was computed. For the removed pixels, the average lost energy (ALE) was computed correspondingly. Finally, the important information deformation function (IIDF) was defined by combining ADSI with ALE. If IIDF satisfies the designed terminating condition, seam carving was terminated and non-homogeneous warping was used to get the image of a target size. Experimental results show that the proposed approach can remove unimportant regions while incurring less deformation to important regions and also keeps the aspect ratio of important objects closer to that in the original image.
Multi-layer parallel simulation for complex system based on extended Modelica
He Dongjing, Song Xiao, Zhang Lin, Li Tan
2012, (9): 1240-1244.
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To improve multi-disciplinary modeling and simulation (M&S) efficiency for complex systems, and overcome the shortcoming of no parallel mechanisms in current multi-domain M&S languages like Modelica, a multi-layer parallel framework for complex system simulation was proposed. Parallel mechanisms of application systems were captured from three layers including task layer, entity layer and model layer. Modelica was extended by inserting typical parallel elements of message passing interface (MPI) and OpenMP. A code mapping strategy was presented to transfer Modelica texts to parallel-support codes like C++. Application systems were simulated in multi-layer parallel platforms like multi-core clusters after task allocating. The iterative process of optimization in a typical military complex system was tested using the proposed means. The simulation results show that the efficiency can be improved evidently through the above framework and methods.
Semi-regular triangular mesh subdivision surface reconstruction
Chen Tiantian, Zhao Gang
2012, (9): 1245-1249.
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Focusing on mesh reconstruction problem of reverse engineering, a subdivision surface reconstruction method to reproduce a semi-regular triangular mesh while preserving the sharp feature was proposed, which can make full use of the multiresolution analysis of subdivision surface. Firstly, the base mesh was created by removing maximally the independent set of vertices after the pretreatment. Then by employing the nearest point method on the normal direction projection and considering the Loop subdivision limited position mask, iterative vertices modifications were utilized to adapt the semi-regular mesh to fit the subdivision surface. Finally, experimental results were given to illustrate the effectiveness and efficiency of the proposed method.
Method of bond graph for distinguishing power flow of closed planetary gear train
Li Qingkai, Tang Dewei, Jiang Shengyuan, Deng Zongquan
2012, (9): 1250-1254.
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In order to distinguish the power flow of the closed planetary gear train more simply and clearly, the theory of bond graph was applied for the analysis of power flow of the gear train utilizing the characteristic of conversation of energy and power fluxion of bond graph. Taking the power regurgitant and confluence style of the gear trains for examples, the bond graph model of the gear trains was established according to the transmission relationships and the method of absolute speed. And then the power flow of the gear trains, as well as the conversion mechanism, was got after distinguishing the power flow basing on the discriminant, which provides the foundation for the efficiency computing. This method which is more intuitionistic and systematic than the traditional methods could be applied in the power flow judgement of other complex gear trains.
Formal specification of dynamic fault tree based on sequence failure symbol
Wang Bo, Liu Dong, Li Yi
2012, (9): 1255-1260.
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The formal framework of the sequence failure symbol (SFS) was defined, including definitions, properties, rules and theorems, which is the basis of the formal specification for dynamic fault tree (DFT). Under the formal framework of the SFS, formal specifications methods and automatic conversion algorithms for any form of static fault tree (SFT) and DFT were given. An example demonstrated the effectiveness of the proposed approach. Formal specification helps to build a more rigorous mathematical theoretical system of DFT. Meanwhile, automatic conversion algorithms based on SFS's formal specification are conducive to the realization of effective computer-aided modeling for DFT.
Production plan and control of manufacturing system based on simulation
Zhong Meiying, Liu Zhixin
2012, (9): 1261-1266.
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Based on the analysis on production plan and schedule data of the modern manufacturing procedure, the objected-oriented simulation system model for job-shop was established using objective-oriented method. From the viewpoints of manufacturing cell and job shop, the simulation procedure and control points of the modern manufacturing system were provided by process control charts. An example of objected-oriented simulation system was established to apply production planning design and optimization for a job shop manufacturing engine turbine blade of an aviation enterprise based on witness dynamic system simulation platform.
Effect of twist on permeability of the sewing thread
Liu Qian, Zhao Yan, Duan Yuexin, Luo Ji
2012, (9): 1267-1270.
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An accurate assessment of the axial permeability of sewing thread with different twists was presented. Meanwhile, the dimensions of the sewing threads with different twists and their interface with resin were discussed by the scanning electron microscope technology. The experimental results show that the increasing of sutures' twist degrades the permeability along the axial direction of sewing thread and dimensions of sutures' cross-section decrease while the interface of sewing thread and resin deteriorate with increasing the twist of the sewing thread. However, the dimensions of sutures after infiltration of resin are greater than before.

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