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2016 Vol. 42, No. 3

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Volume 42 Issue32016
2016 Year 42 Volume 3 Issue E-journal
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Structural reliability analysis based on dimensionality reduction and Edgeworth series
MENG Guangwei, FENG Xinyu, LI Feng, ZHOU Liming
2016, 42(3): 421-425. doi: 10.13700/j.bh.1001-5965.2015.0181
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A reliability analysis method based on the dimension reduction algorithm and the Edgeworth series was proposed to treat the complicate structures with implicit and high dimensional nonlinear limit state functions in practical engineering. By utilizing the dimension reduction method, the n-dimensional function was expanded to n unidimensional functions and the random variable were made to subject to the independent normal distribution with mean value being zero and variance deviation being 0.5 by means of the variable transformation. The origin moments of the unidimensional functions were obtained after the Gauss-Hermite integration. In this case, the central moments of the limit state function of the structure were achieved successfully and applied to the Edgeworth series expanding expressions, from which the cumulative distribution function of the limit state function could be generated and finally the probability of failure could be obtained. Avoiding gradient computation, the proposed method requires less definite reanalysis and is proved to be effective and correct via numerical examples.
Design of control law for ejection seat under adverse attitudes
MAO Xiaodong, LIN Guiping, YU Jia
2016, 42(3): 426-434. doi: 10.13700/j.bh.1001-5965.2015.0188
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The escape performance of ejection seat under adverse attitudes is the key technology for the 4th generation ejection seat, and the design of control law algorithm is the core problem for attitude and trajectory adjustment. A new control law design method was presented. Firstly, a simulation model for the entire ejecting process was established and a control parameter optimization model was designed, through which an optimum parameter set was obtained as the discrete control law. Then, by utilizing multi-layer feedback of the error back propagation (BP) algorithm based neural network model, the ultimate continuous control law can be acquired under the whole ejecting conditions. The roll attitude ejecting condition was exampled to design and validate the approached method. The results indicate that the performance of ejection seat by adopting the control law designed by the proposed method is higher than the multi-mode control law and the K36Л-3.5 ejection seat, which also satisfies the performance demand of GJB under most conditions. Consequently, the design method is simple and clear, and the final algorithm is close to the theoretical optimum result. Therefore, it is proved to be a useful method for the design of the 4th generation ejection seat control law.
Hot-rolling batch scheduling in round steel production with flexible maintenance planning
WANG Lei, ZHAO Qiuhong, XU Shaoyun
2016, 42(3): 435-443. doi: 10.13700/j.bh.1001-5965.2015.0170
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A hot-rolling batch scheduling problem of round steel with flexible maintenance planning was studied. For obtaining an effective cooperative scheduling with machine maintenance and batch production, a multi-objective integer programming model was built with the objectives to minimize the makespan, the earliness and tardiness of orders. With the consideration on the feature of the model, an improved multi-objective particle swarm optimization (IMPSO) algorithm was proposed to solve the problem. In the proposed algorithm, an insertion algorithm based on fitness assignment with chaos weighting was designed to generate the initial solution. According to the constraints in the model, some rules were proposed to repair unreasonable solutions emerging in the genetic progress of the population. With the elitist strategy, advanced individuals are preserved in evolution process, and the extremums for every individual's updating were also selected from elite set. In addition, with considering the discrete characteristic of variables, genetic operators were introduced to update particles. Experimental results show that the model and algorithm are feasible and effective.
Heading sensitive drift behavior model for platform inertial navigation system under long-term storage
HUANG Xiaokai, ZHANG Chao, HU Fang, LIU Shouwen
2016, 42(3): 444-451. doi: 10.13700/j.bh.1001-5965.2015.0151
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The heading sensitive drift of platform inertial navigation system varies with the degradation of performance and the coupling characteristics under long-term storage conditions. Such heading sensitive drift is different from those under working conditions, which makes it difficult to analyze the stability for allocating resources for the calibration and maintenance in engineering application. The theory and expression of heading sensitive drift caused by servo loop zero and structure disturbing torque are firstly presented and derived. Secondly, the drift characteristics of influence parameters are analyzed thoroughly, and the integrated behavioral model of heading sensitive drift under servo loop zero and disturbing torque influence is concluded. And then, the long-time drift characteristic, acceleration performance, as well as the stability of heading sensitive drift behavior are analyzed with actual storage condition profile. Results indicate that heading sensitive drift on the X, Y and Z axis has the similar long-term drift characteristics without acceleration response, which is different from the response characteristic in actual use and therefore has great significance for allocating resources for the calibration and maintenance of inertial platform system.
Surface temperature distribution of molten pool by ultra high frequency pulsed GTAW
YANG Zhou, QI Bojin, YANG Mingxuan
2016, 42(3): 452-458. doi: 10.13700/j.bh.1001-5965.2015.0155
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Thermal observation of molten pool was carried out with Ti-6Al-4V plates (with thickness of 5 mm). The molten pool surface temperature distribution of ultra high frequency pulsed gas tungsten arc welding (UHFP-GTAW) was collected and analyzed by infrared imaging monitor. Compared with conventional GTAW (C-GTAW), the test results indicate that the surface temperature of molten pool center increases by 10-30 K with UHFP-GTAW(20 kHz, 40 kHz) after heating the base metal 20 seconds; meanwhile, the areas of the elevated temperature distribution were measured referring to varying temperature (678 K,823 K,968 K), which are reduced by the range of 13%-30%. A two-dimensional numerical model of molten pool was established, considering the essential factors such as heat flux, force and mixed heat transfer, to explore the characteristics of the temperature distribution in the molten pool. The calculated results of the above model are basically consistent with the test data.
Multi-valued decision diagram based reliability modeling of warm standby systems
ZHAI Qingqing, YANG Jun, PENG Rui, ZHAO Yu
2016, 42(3): 459-464. doi: 10.13700/j.bh.1001-5965.2015.0153
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As a generalization of cold and hot standby technique, warm standby has been widely used in the system design. This paper focuses on the reliability modeling of warm standby systems and extends a multi-valued decision diagram (MDD) based system reliability modeling approach. By concentrating on the failures in the system, the existing method first constructed the failure level MDD and system MDD, and then obtained the analytical expression for the system reliability based on the system MDD. However, the system reliability expression is a mixture of integrals of different dimensions, which requires some manual rearrangement to calculate the system reliability at given time. Based on the existing work, we suggest an MDD splitting procedure after obtaining the system level MDD and a reassignment for the probabilities of the edges in the system MDD. With this extension, the numerical value for the system reliability at any given time can be easily obtained and the MDD based reliability evaluation approach for warm standby systems is completed.
Phase retrieval for multiple-wavelength in-line digital holography
LI Yan, XIAO Wen, PAN Feng
2016, 42(3): 465-471. doi: 10.13700/j.bh.1001-5965.2015.0161
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In-line digital holography, because of its most simplified holographic recording architecture without extra reference beam, has a larger field of view compared with off-axis digital holography. Thus, it has been applied in many fields. However, both the defocused conjugate images and zero-order autocorrelation are superimposed on the real image of the object in the reconstruction process, which blurs the real image and degrades the measurement accuracy. A phase retrieval method is proposed to eliminate the unwanted conjugate image based on four diffraction intensity patterns recorded at different illumination wavelengths for in-line digital holography, in which the appropriate constraints are imposed both on the hologram plane and object plane. A synthetic wavelength is used to retrieve wrap-free phase distributions with a much extended vertical measurement range, thus the reconstructed phase distribution directly provides the height distribution of the surface of the sample after eliminating the twin image. In comparison with previous research, the proposed method requires a fewer number of illumination wavelengths and has a faster rate of convergence, as well as a better elimination effect, which is demonstrated by the simulation and experimental results.
Large angle maneuvering control for missiles based on improved Terminal sliding mode method
MA Yueyue, TANG Shengjing, GUO Jie
2016, 42(3): 472-480. doi: 10.13700/j.bh.1001-5965.2015.0189
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Based on compound sliding surface and disturbance rejection mechanism, a novel design approach of nonsingular Terminal sliding mode (NTSM) controller is proposed for large angle maneuvering control during an air-to-air missile intercepting a target in the rear hemisphere of the carrier. Firstly, the mathematical model of an air-to-air missile equipped with reaction-jet control system (RCS) is established considering the aerodynamic uncertainties. Subsequently, a missile attitude control law is designed by the traditional NTSM method. On this basis, taking original states far from equilibrium during large angle maneuvering into account, a compound sliding surface is adopted to accelerate the convergence of control system. To solve the problem of severe chattering caused by the aerodynamic uncertainties at high angle of attack, extended state observer (ESO) methodology is introduced to online estimate and compensate the system uncertainties. Furthermore, the stability analysis to the proposed method demonstrates the finite time convergence property of the control system. Eventually, the designed controller is applied to the large angle maneuvering control for agile turn of air-to-air missile. Simulation results reveal that the proposed method is able to make the convergence faster and effectively attenuate chattering caused by unmodeled dynamics.
Power upshift control strategy of torque-assist AMT
LU Jiapeng, LI Youde, HAN Peng, CHENG Xiusheng
2016, 42(3): 481-488. doi: 10.13700/j.bh.1001-5965.2015.0865
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The power upshift control strategy of torque-assist automated mechanical transmission (AMT) is researched. A torque-assist mechanism is equipped in the traditional AMT of commercial vehicle, which is made up of an assist clutch and automated control unit. The dynamic model of torque-assist AMT is established. According to the evaluation criterion of the shift process, the power upshift control strategy is developed. The simulation research is carried out based on the state from the second gear to the third gear, and the vehicle test is taken to verify the validity of the control strategy. The simulation and test results show that the torque-assist AMT can output power during the shift process and improve the shift quality.
Heat transfer characteristics of axial piston pump slipper pair
TANG Hesheng, YIN Yaobao, LI Jing
2016, 42(3): 489-496. doi: 10.13700/j.bh.1001-5965.2015.0142
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To explore the distribution law of oil film temperature field at slipper pair for axial piston pump, a thermodynamic model of slipper pair was built through the conservation law of heat flux after analyzing its transfer mechanism in detail. The effects of slipper structure parameters on film temperature under different piston chamber pressure and shaft rotational speeds were discussed. The results show that the film temperature distribution is non-uniform and show decreasing tendency along slipper radius. The maximum film temperature takes place in the slipper region where oil film thickness is thinnest. The phenomenon occurs mainly in discharge stroke, and causes slipper partial abrasion. When the slipper radius ratio is set from 1.5 to 2.0, the smaller radius ratio is selected to decrease film temperature and improve slipper lubrication performance under high shaft rotational speed. When the orifice length diameter ratio is set from 3.50 to 8.75, the lower orifice length diameter ratio is useful to decrease film temperature and improve the cooling effect of pump.
Local feature descriptor based on nonparametric marginal integration estimation
ZHENG Mingguo, WU Chengdong, CHEN Dongyue, JIA Tong, JIN Yonghu
2016, 42(3): 497-505. doi: 10.13700/j.bh.1001-5965.2015.0156
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A statistical model for the feature descriptor of local region was suggested to improve the image matching performance. This model is a marginal integration function model based on the gradient magnitude and orientation distribution. The marginal integration function on the discrete gradient orientations is the same as the magnitude accumulation orientation histogram of gradient vector field. Using the nonparametric estimator based on kernel function, we estimated this function and applied it to scale invariant feature transform (SIFT) descriptor. To enhance rotation invariance and distinctiveness and to reduce computational complexity for descriptor, local region around the feature point was selected as circle and partitioned to the 8 sub-regions by radial sampling grid. The marginal expectation functions are estimated in each sub-region and the feature vector consists of the function values on the 8 orientations for 8 sub-regions. Experiments show that this descriptor can improve detective rate (recall) for rotation and reduce computational complexity.
Fault diagnosis method based on extension rule-based reasoning
WEN Tianzhu, XU Aiqiang, WANG Yiping
2016, 42(3): 506-513. doi: 10.13700/j.bh.1001-5965.2015.0166
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Aimed at low inference efficiency, difficult knowledge acquisition and unsuitability for multi-fault diagnosis in production rule reasoning method, the fault diagnosis method based on extension rule-based reasoning is studied. Firstly, the expression of extension rule is obtained by combining basic-element theory with production rule. Secondly, the matching degree formula of extension rules is given, and the hierarchical matching method according to the difference of antecedent mode and data type is proposed. Furthermore, the conflict resolution strategy of "first cut, then sort" is put forward for all extension rules which are matched successfully, and the time complexity of this method is discussed. Finally, the whole process of expression, matching, reasoning and conflict resolution for extension rules is explained by an application case, and the results show that this method can be used for the multi-fault diagnosis of airborne equipment.
Correction of contrast distortion image based on nonlinear transform of histogram
GAO Ming, QIN Shiyin
2016, 42(3): 514-521. doi: 10.13700/j.bh.1001-5965.2015.0168
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In the practical imaging, the image contrast is distorted due to influence of multi-factors, which degrades image quality greatly. A contrast correction method is presented based on nonlinear transform of histogram and parameter optimization in order to improve image quality and enhance the visual effect. Firstly, in view of the limitation of conventional histogram equalization method, a nonlinear transform model of histogram was established based on the prior constraints of image histogram through the analysis of human visual perception characteristics. Then the parameters of transform model are optimized with the evolutionary searching of genetic algorithms to achieve optimal corrective effect so that a high performance contrast distortion correction algorithm emerged. A series of correction experimental results for real images with severe contrast distortion from different scenes demonstrate that the proposed algorithm outperforms the conventional correction methods in both of objective quality assessment and subjective visual effect and is provided with distinct advantages.
Missile competing fault prediction based on degradation data and fault data
CONG Linhu, XU Tingxue, WANG Qian, DONG Qi
2016, 42(3): 522-531. doi: 10.13700/j.bh.1001-5965.2015.0175
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Aiming at the problem of missile competing fault prediction which has multivariate degradation data, the characteristics of missile degradation are analyzed and missile competing fault prediction model which has multivariate degradation data is established considering the correlation between sudden fault and degradation fault. The distribution patterns of performance degradation data and sudden fault data are determined through statistical inference, and on this basis the parameters for competing fault prediction model are solved. Aiming at the distribution parameters of performance degradation data having the feature of small sample and nonlinearity, least square support vector machine (LS-SVM) prediction algorithm is used to predict the distribution parameters of performance degradation data in order to get the future distribution function. Aiming at the correlation between sudden fault and degradation data, the correlation parameters of sudden fault and degradation data are obtained using location-scale model to analyze the relations between sudden fault and degradation data. Furthermore, the future missile competing fault probability can be obtained according to the missile competing fault prediction model. The efficiency and validity of missile competing fault prediction model are verified by case analysis and contrasting with other prediction methods.
Body-flap attitude control method for lifting re-entry vehicle
WANG Zhi, LI Huifeng, BAO Weimin
2016, 42(3): 532-541. doi: 10.13700/j.bh.1001-5965.2015.0192
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An attitude output tracking control method is proposed for a lifting re-entry vehicle with a non-minimum phase property. Such problem is caused by body flaps which are the only actuators to be used for controlling three-channel. By using local differential homeomorphism, the attitude input-output model is transformed into normal form, and internal dynamics are obtained. A criterion of non-minimum phase is developed by analyzing the internal dynamics' stability, and this criterion is used to predict the non-minimum phase phenomena when aileron reversal exists. To solve this problem, the normal form is decomposed into a minimum phase subsystem (longitudinal channel) and a non-minimum phase subsystem (lateral-directional channel). And then, dynamics inversion is used to design the state-feedback controllers for these two subsystems.Moreover, a nonlinear auxiliary control input is introduced to stabilize the overall attitude control loop by both Lyapunov function and a minimum-norm control strategy. Simulation results demonstrate that in the case where body flap actuators are employed for attitude control, the control commands can be tracked and internal dynamics can be stabilized by the proposed method.
Stage-wise multidisciplinary design optimization for multi-stage solid launch vehicle
MA Shuwei, LI Jinglin, CHEN Xi, CHEN Wanchun
2016, 42(3): 542-550. doi: 10.13700/j.bh.1001-5965.2015.0196
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Because of the strong coupling of multi-disciplines and the complicated algorithm and the low design efficiency, the integral optimization design of solid launch vehicle is a difficult, but important problem. To solve this problem, the multidisciplinary models of a multi-stage solid launch vehicle, including geometry, mass, aerodynamic, propulsion and trajectory/guidance systems, were established. Then, the multi-stage solid launch vehicle was divided into several sub-stages which were connected by the continuous requirements of the flight states. Thus, the system-level and subsystem-level solution frameworks were constructed. Furthermore, two types of optimization processes, named parallel and serial methods, were presented to solve the multidisciplinary design optimization (MDO) problem where the objective function is to minimize the gross weight. The results show that via the stage-wise formulation, the number of iterations can be reduced and better results can be obtained,compared with the traditional multidisciplinary feasible (MDF) method, and thus we verify the feasibility and superiority of the proposed approach applied to MDO problems for multi-stage solid launch vehicles.
Improved Jacobi iterative method for hybrid grid and its application
HUANG Yu, YAN Chao, YUAN Wu
2016, 42(3): 551-561. doi: 10.13700/j.bh.1001-5965.2015.0197
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LU-SGS scheme is widely used today because of its robustness and cheap memory cost. However, the original LU-SGS shows less competitive convergence rate; in order to apply paralleled codes on hybrid unstructured grid, the grid reordering and regrouping procedure must be carried out beforehand. In this paper, an improved implicit method suitable for complex hybrid gird is developed to achieve fast convergence rate and to parallelize the algorithm without grid reordering and regrouping procedure. This method is simple for coding and easy to use OpenMP for code parallelization. The numerical results of Euler and viscous flows show that the method has a reliable performance, and it is able to achieve a significant efficiency improvement over implicit counterparts such as LU-SGS scheme with less requirement of extra memory, and parallel computation produce exactly the same result as serial case.
Vision guide based teaching programming for industrial robot
NI Ziqiang, WANG Tianmiao, LIU Da
2016, 42(3): 562-568. doi: 10.13700/j.bh.1001-5965.2015.0218
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Most industrial robots used in manufacture are based on teaching programming and offline programming. The shortcomings of these two programming methods limit the further application of industrial robots. A vision guide based programming method was introduced to solve the problem. The singular value decomposition (SVD) algorithm was used to calculate the registration matrix between computer vision space and robot space. The positions and orientations of robot's end-actuator were obtained by measuring the teaching tool, which is the key process to realize vision guide programming. Analytical the format of executable file which running on robot controller, and then transform the positions and orientations' data into executable file. An experiment was introduced to verify the feasibility and reliability of the programming method. The results indicate that the maximum error of trajectory tracking is -1.18 mm, and the root mean square error is 0.47 mm.
Cold standby n-component repairable system with repairman vacation
WEN Yanqing, CUI Lirong, LIU Baoliang
2016, 42(3): 569-575. doi: 10.13700/j.bh.1001-5965.2015.0226
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The reliability for a cold standby n-component repairable system with a repairman having multiple vacations is studied. If all of units are in normal state, the repairman may take his vacations, and the vacation time is a random variable. During the repairman's vacation, if a unit online fails to work, one of cold standby components becomes the component online immediately the failure unit will not be repaired until the repairman comes back from his vacation. The operational time of the unit online, the repair time and the vacation time of repairman are governed by different phase-type (PH) distributions, respectively. The system is studied in a transient and stationary regime. The reliability, availability, rate of occurrence of failures and busy probability of repairman are derived by Kronecker operator and Markov process theory. A numerical example is given to illustrate the results obtained.
Reliability assessment method of nonlinear step-stress accelerated degradation data
CAI Zhongyi, CHEN Yunxiang, ZHANG Zhengmin, XIANG Huachun
2016, 42(3): 576-582. doi: 10.13700/j.bh.1001-5965.2015.0459
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Aiming at nonlinear degradation data in the occasion of step-stress accelerated degradation test (SSADT), a reliability assessment method for degradation data based on Wiener process is put forward in consideration of individual performance degradation variation. Firstly, the process and performance degradation data model of SSADT are analyzed. Secondly, the nonlinear Wiener process is used to describe the nonlinear degradation process of products. The time scale model is used to change nonlinear data into linear data, and the drift coefficient of Wiener process is regarded as a random variable. A lifetime model of nonlinear degradation data is built in consideration of individual variation. According to the collected SSADT data, the two-step maximum likelihood estimation method is used to determine the unknown parameters in the lifetime model. Finally, an example of laser degradation data is analyzed to show that the presented model is matching well and the assessment result is more accurate.
Effect of pneumatization degree of temporal bone air cell on vascular pulsatile tinnitus
YANG Jiemeng, WANG Lizhen, TIAN Shan, LIU Zhaohui, FAN Yubo
2016, 42(3): 583-587. doi: 10.13700/j.bh.1001-5965.2015.0140
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To quantify the biomechanic relationship between the degree of pneumatization in the temporal bone air cell and vascular pulsatile tinnitus, the numerical simulation upon a typical vascular pulsatile tinnitus patient's data were conducted in this study. First, the two 3D geometric models of temporal bone air cell, including the basic model and the over-pneumatization model, were developed based on the same patient's CT images individually. Second, the models were meshed with tetrahedral elements by Hypermesh, and computed 3D finite element (FE) models were generated. Then two FE models were imported into Virtual. Lab Acoustics. Third, the same velocity boundary condition was loaded, and then the sound intensity of vibration response was achieved by Virtual. Lab Acoustics. Finally, the sound intensity amplitude at the vestibule was computed. A comparative analysis of two models was done based on the biomechanical numerical simulations. It was shown that the sound intensity amplitude of the over-pneumatization model was 3.02 dB lower than the basic one at 250 Hz. It was found that the difference of amplitude between two models could be perceived by vascular pulsatile tinnitus patient under the condition of same frequency. These would provide a new theoretical basis for innovative treatment of vascular pulsatile tinnitus.
Scattering characteristics simulation and experimental analysis of precession cone target
YE Taoshan, HUANG Peilin, SHU Changyong, WANG ying, PENG Yaokun
2016, 42(3): 588-595. doi: 10.13700/j.bh.1001-5965.2015.0141
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The micro-motion and structural parameters of the ballistic target play an important role in ballistic target recognition. And correctly acquiring scattering characteristics of precession targets is essential to obtain these parameters, such as time-frequency distribution (TFD), range profiles and inverse synthetic aperture radar (ISAR) images. Scattering characteristics of the precession cone target under narrowband and wideband are analyzed, especially on the case where the specular scattering exists, and the theoretical expressions of TFD, range profiles and ISAR images with respect to strong scattering centers of the target are given briefly. In addition, a dynamic measuring system in anechoic chamber was established to collect the electromagnetic response from the precession target. The simulation and experimental results are verified with theoretical deductions, and so as for the feasibility of the proposed model and imaging algorithm.
Spacecraft electrical signal classification method based on improved artificial neural network
LI Ke, WANG Quanxin, SONG Shimin, SUN Yi, WANG Jun
2016, 42(3): 596-601. doi: 10.13700/j.bh.1001-5965.2015.0186
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To solve the problem of multiple data and arduous task in the aircraft test and intellectualize the management of the testing work, an intelligent classification system based on artificial neural networks was designed. The system can classify the original test data intelligently, reduce the workload and reliance on testing experience and store the nonlinear debugging experience in the form of expert database. This system has many deficiencies, such as, long training time and high dependence on the initial threshold. To this end, the principal component analysis was used to compress the raw data and auto-encoder in deep learning was applied to initialize the network weights. Experimental data indicates that compared with traditional methods, the accuracy, stability and response speed of the improved learning system are significantly increased.
First-principles investigation of Heusler alloys M2CoA(M=Mn,Ti;A=Al,Si)
LIN Daobin, SA Baisheng, ZHOU Jian, SI Chen, SUN Zhimei
2016, 42(3): 602-609. doi: 10.13700/j.bh.1001-5965.2015.0201
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The electronic structure and magnetic properties of the M2 CoA type Heusler alloys Mn2CoAl, Mn2CoSi, Ti2CoAl and Ti2CoSi were systematically investigated using first-principles calculations based on the density functional theory. The results show that Mn2CoAl is a ferrimagnetic spin gapless semiconductor; Mn2CoSi and Ti2CoAl are ferrimagnetic spin half-metals, while Ti2CoSi is a ferromagnetic spin half-metal. The total spin magnetic moments of the M2CoA type Heusler alloys are integers, obeying the Slater-Pauling rule. By analyzing the band structures and electronic density of states, the origin of spin gapless semiconductor as well as half-metal were revealed. The calculation results of phonon dispersion curves and elastic constants show that all the M2CoA type Heusler alloys are stable in the lattice dynamics and mechanics.
Fluid-pipe coupling axis vibration characteristics induced by foundation vibration
LIU Sen, ZHANG Huailiang, PENG Huan
2016, 42(3): 610-618. doi: 10.13700/j.bh.1001-5965.2015.0208
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In view of the effect of axial foundation vibration on pipe and fluid fluctuation, an axial coupling vibration mathematical model of direct hydraulic pipeline was used to deduce boundary conditions under four different pipe end constraints, and method of characteristics was adopted to study the fluid fluctuation in pipe induced by foundation vibration under different constraints. The influences of bound manner, restraint stiffness, foundation vibration parameters and structural parameters on pipe outlet pressure fluctuation amplitude were analyzed. The results indicate that the outlet pressure fluctuation amplitudes increase a lot respectively when export axial and entrance axial are free, compared with fixed constraints of both ends. And the greater the exit restraint stiffness is, the smaller the pressure fluctuation amplitude is; the higher vibration frequency is, the stronger fluid-solid interaction is; the pressure fluctuation amplitude increases linearly with the increase of foundation vibration amplitude; the longer the distance of fluid flowing through the pipe is, the severer the fluid fluctuating is. The analysis results could provide a theoretical basis for the formulation of corresponding pipe vibration control strategy.
Low-temperature brazing wettability research of LD30 aluminum alloy and 304 stainless steel
XIONG Huan, QU Wenqing
2016, 42(3): 619-624. doi: 10.13700/j.bh.1001-5965.2015.0219
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LD30 aluminum alloy with 304 stainless steel using low temperature brazing was performed in the wettability research. Through wettability study contrast, three kinds of low melting point solders 60Sn-40Pb, Sn-3.5Ag and 35Sn-40Pb-25Bi which were suitable for LD30 aluminum alloy and 304 stainless steel were chosen, and solder flux was selected. The joint of microstructure, phase composition, X-ray inspection were analyzed. Results show that the 60Sn-40Pb and 35Sn-40Pb-25Bi combine with H3PO4 have good wettability on 304 stainless steel; the 60Sn-40Pb and 35Sn-40Pb-25Bi combine with 50% H3PO4 and 50% glycol have good wettability in the brazing experiment and the Sn-3.5Ag has relatively poor wettability.
Heat conduction analysis for simplified model of large scale space deployable structure
YANG Juntan, QIU Zhiping, LYU Zheng, LI Qi
2016, 42(3): 625-631. doi: 10.13700/j.bh.1001-5965.2015.0222
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Based on heat conduction and the equivalent thermal parameters, the space cable-strut deployable articulated mast and its ambient thermal environment were simplified. The dynamic boundary temperature was expanded into harmonic components adopting Fourier series, and the corresponding transient thermal response of the simplified mast under each component was calculated using one-dimensional heat conduction model, respectively. The overall transient response was then obtained via superposition principle. The thermal response under the same setup was estimated using a finite element model, by which the reasonability of aforementioned calculation was verified. The method presented in this paper could be a useful reference for thermal analysis of similar structures, particularly in conceptual design.
Simulation and analysis on electromagnetic impulse force of electro-impulse de-icing system
YUAN Qihang, LIN Guiping, LI Guangchao, SHEN Xiaobin, BU Xueqin
2016, 42(3): 632-638. doi: 10.13700/j.bh.1001-5965.2015.0351
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In order to calculate the electro-magnetic force on skin and changes with time more accurately, the working mechanism and process of the electro-impulse de-icing (EIDI) system were studied. The current in circuit of the system was calculated and analyzed. The electromagnetic field of the system was simulated by solving the Maxwell equations. Electromagnetic force time history was calculated and analyzed. The distribution of flux density, eddy current density and transient electromagnetic force density on skin was acquired. Meanwhile, it was accurately acquired how electromagnetic force changed with time by simulating the real circuit working whose inductance was influenced by skin. Moreover, considering that skin effect affects the eddy current and electromagnetic force density, finite element method is more reasonable for calculating the distribution of electromagnetic force on skin.

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