JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Initiation behavior of covered explosive subjected to reactive fragment

WANG Hai-fu, ZHENG Yuan-feng, YU Qing-bo, LIU Zong-wei, YU Wei-min

2012, 21(2): 143-149.

[Abstract](1032) [PDF 3316KB](275)

Abstract:
Reactive fragment enhances lethality by incorporating the defeat mechanisms of kinetic energy and chemical energy into a unitary damage unit. Combined studies on the behavior of reactive fragment initiating covered explosive are performed theoretically and experimentally. The results indicate that the response of the covered explosive subjected to reactive fragment is not consistent with the classical shock initiation model. When impacting and penetrating into the covered explosive, the reactive fragment releases great amounts of thermo-chemical energy up to 5.68 times of its kinetic energy into the explosive due to violent chemical reactions. This impact-induced chemical energy release behavior of the reactive fragment significantly enhances the initiation capability and damage effects on the covered explosive.

Modeling and simulation of JWL equation of state for reactive Al/PTFE mixture

JIANG Jian-wei, WANG Shu-you, ZHANG Mou, WEI Qiang

2012, 21(2): 150-156.

[Abstract](1091) [PDF 1398KB](514)

Abstract:
An analytical method is presented to fit parameters of Jones-Wilkins-Lee (JWL) equation of state (EOS) for the chemical process of aluminum-polytetrafluoroethylene (Al/PTFE) mixture. Subroutine codes for both strength model and EOS were developed in explicit-FE code AUTODYN. Firstly, the shock Hugoniot data of reactive Al/PTFE mixture was analytically derived by implementing this methodology. The JWL EOS was verified to fit shock Hugoniot data of both reacted and unreacted Al/PTFE mixture, which gives reasonable results. Furthermore, to numerically ascertain the reaction phases of ignition and growth and quasi detonation of Al/PTFE mixture, characterized experiment was setup to validate the reaction phases and coefficients of JWL EOS for Al/PTFE mixture. From the test, a promising example of reactive mixture Al/PTFE is capable to enhance lethality of weapons, the status computation in clude quasi-detonation pressure and temperature of Al/PTFE mixture in different chemical reaction phases is validated.

Artificial neural network modeling of mechanical properties of armor steel under complex loading conditions

XU Ze-jian, HUANG Feng-lei

2012, 21(2): 157-163.

[Abstract](776) [PDF 399KB](184)

Abstract:
An artificial neural network (ANN) model is established to predict plastic flow behaviors of the 603 armor steel, based on experiments over wide ranges of strain rates (0.001-4.500.s^-1) and temperatures (288-873.K). The descriptive and predictive capabilities of the ANN model are compared with several phenomenological and physically based constitutive models. The ANN model has a much better applicability than the other models in characterization of the flow stress. The temperature and the strain rate effects on the flow stress can be described successfully by the ANN model, with an average error of 1.78% for both quasi-static and dynamic loading conditions. Besides its high accuracy in prediction of the strain rate jump tests, the ANN model is more convenient in model establishment and data processing. The ANN model developed in this study may serve as a valid and effective tool to predict plastic behaviors of the 603 steel under complex loading conditions.

Optimization of the carrier tracking loop for GPS high dynamic receivers

LI Chuan-jun, YANG Shu-xing

2012, 21(2): 164-171.

[Abstract](640) [PDF 400KB](225)

Abstract:
A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γ filter model, adaptive loop structure model and adaptive loop bandwidth model respectively, are added in the presented tracking loop compared with the traditional carrier tracking loop based on the second-order frequency lock loop (FLL) assisting third-order phase lock loop (PLL) loop filter. And the optimization methods for the tracking bandwidth and the carrier loop order are analyzed. The real-time estimation methods of the dynamic parameters, the velocity, acceleration and jerk along the line of sight (LOS) between the satellite and the receiver’s antenna, and the measurement parameters are discussed based on the presented α-β-γ filter algorithm. A method is introduced to improve the filter’s dynamic response to meet high dynamic application by self-adjusted α-β-γ filter coefficient used in the tracking loop. The performance of three cases with different carrier tracking loop is compared by simulation.

Analysis and design for missile of three-loop autopilot

WEN Qiu-qiu, XIA Qun-li, ZUO Ti-ti

2012, 21(2): 172-178.

[Abstract](794) [PDF 346KB](209)

Abstract:
The structure characteristic of the three-loop autopilot is analyzed and the pole placement analytic algorithm is given. In order to ensure that the system will meet the stability requirement when taking the dynamic characteristics of all the hardware devices into account, the frequency of the open-loop crossover should be constrained. Based on the pole placement algorithm, a non-linear equation with the non-dominant pole as a variable and the open-loop crossover frequency as a constraint is constructed. Solving the equation and getting the corresponding value of the non-dominant pole, the design of autopilot can be completed. Finally, through an example, it is shown that the method is convenient and practicable for the design of a three-loop autopilot.

Vibration test of micro machined gyroscope based on high speed photography and SURF

YAO Feng-lin, GAO Shi-qiao, ZHAO Jie, GAO Chong-ren

2012, 21(2): 179-184.

[Abstract](647) [PDF 801KB](174)

Abstract:
Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more accurate, and more suitable for the vibration test of micro machined gyroscope. After the frequency analysis and related interpolation, more characteristics of micro gyroscope can be obtained.

Intrusion response goals and corresponding strategies

MU Cheng-po, HAN Cao-zheng, SHUAI Bing

2012, 21(2): 185-191.

[Abstract](649) [PDF 708KB](153)

Abstract:
The effects of strategy on the network security defense and the related research on intrusion response strategy are briefly presented, with the focus on the status and function of intrusion response strategy in the intrusion response decision-making. Some specific response strategies for specific response goals are presented as well. The relevant knowledge of the planning, and a classification of response tasks are proposed. The intrusion response planning methods and models based on hierarchical task network (HTN) are described in detail. On this basis, the model of combining the response measure decision-making with the response time decision-making is expounded. The proposed model can integrate response strategy into response decision-making mechanism. In addition, the results of the intrusion response experiments are provided to verify the ability of using different response strategies to achieve different response goals. At last, the application needs of response strategy in network security are analyzed, and the approaches of the response strategy applied in intrusion response system are summarized.

Experimental validation method of elastic thin rod model for simulating the motional cable harness

WANG Chun-sheng, LIU Jian-hua, NING Ru-xin, CHEN Tao

2012, 21(2): 192-197.

[Abstract](620) [PDF 1172KB](157)

Abstract:
To analyze the spring disturbance torque caused by motional cable harness in a stabilized platform, the Kirchhoff theory based cable harness model has been previously developed to dynamically simulate the motional cable harness. In this paper, this model was validated by comparing the simulation results with the experiment results (both the spring force and the deformed profile of the motional cable harness). In the experiment, a special optical measuring instrument based on binocular vision was developed and the motion and deformation of cable harness were measured. A simplified stabilized platform system was constructed, and the absolute value of spring disturbance force during the motion of this simplified frame was obtained by using a force gauge (0.02.N precision). The physical parameters of experimental specimen were also measured. The experimental and simulated results showed good agreement. These results should be useful for better motional cable harness layout design and reliable evaluation of the spring disturbance torque.

Calculation methods of lubricant film pressure distribution of radial grooved thrust bearings

HU Ji-bin, LIU Ding-hua, WEI Chao

2012, 21(2): 198-202.

[Abstract](599) [PDF 344KB](186)

Abstract:
In order to calculate the pressure distribution of radial grooved thrust bearing, analytical and numerical methods were applied respectively. Grooved region and land region were linked by using the mass conservations principle at the groove/land boundary in each method. The block-weight approach was implemented to deal with the non-coincidence of mesh and radial groove pattern in numerical method. It was observed that the numerical solutions had higher precision as mesh number exceed 70×70, and the relaxation iteration of differential scheme presented the fastest convergence speed when relaxation factor was close to 1.94.

Development of an occupant restraint system model and parametric study on equivalent crash pulse in vehicle frontal offset crash

LI Zhi-gang, ZHANG Jin-huan, MA Chun-sheng

2012, 21(2): 203-209.

[Abstract](646) [PDF 710KB](212)

Abstract:
Studies were conducted to evaluate driver injury metrics with varying crash pulse in offset crash. First, a vehicle finite element (FE) model and an occupant restraint system (ORS) model were developed and validated against tests; then, the crash pulse collected from the test vehicle was equivalent to a dual-trapezoid shape pulse which will be quantitatively described by six parameters and was put into the ORS model; finally, parametric studies were conducted to analyze the sensitivities of parameters of equivalent crash pulse on head resultant acceleration, head injury criteria (HIC), neck axial force and chest deformation. Results showed that the second peak value of the crash pulse was statistically significant on all these injury criteria (P=0.001, 0.000, 0.000, 0.000 respectively), the first peak level had a negative significantly effect on all the criteria aforementioned except the chest deformation (P=0.011, 0.038, and 0.033 respectively), and the interaction of the time-points of first and second peak values had a significant influence on head resultant acceleration (P=0.03). A higher first peak value and a lower second peak value of the crash pulse could bring deeply lower injury metrics.

Analyzing influence of bicycles on traffic flow using microscopic simulation approach

GUO Hong-wei, WANG Wu-hong, ZHAO Fa-cheng, GUO Wei-wei

2012, 21(2): 210-215.

[Abstract](638) [PDF 591KB](150)

Abstract:
Mixed traffic consisting of cars and bicycles is a typical pattern of urban traffic in China. To study the impact of bicycles on traffic performance, a microscopic simulating model based on the principle of cautious driving and collision free was proposed. The interaction between cars and bicycles were described by lateral friction and overlapping driving. The dynamical features of speed and time-headway were investigated by numerical simulations. The results show that bicycles have a significant impact on travel speed and time-headway. The effect of bicycles can cause different results in the free flow phase and congestion phase respectively. The results also indicate the necessity to mitigate the interaction between motorized vehicles and non-motorized vehicles.

Traffic organization during urban road constructions

SONG Li-ying

2012, 21(2): 216-221.

[Abstract](603) [PDF 336KB](122)

Abstract:
This research presented a bi-level programming approach to optimize the schedule of urban road construction activities based on a hypothetical transport network, with an objective of minimizing the overall traffic delays. A heuristic algorithm was utilized to identify a set of road construction schedules, while PARAMICS was adopted to estimate the total travel time in the network under each road construction scenario. To test the performance of proposed heuristics-simulation methodology, a numerical test was implemented. The overall results suggested that the proposed methodology could quickly find the optimum solution with good convergence.

Distribution of driving trajectory of passenger car in highway horizontal curves

REN Yuan-yuan, LI Xian-sheng, GUO Wei-wei, WANG Ji-liang

2012, 21(2): 222-228.

[Abstract](756) [PDF 405KB](162)

Abstract:
In this paper the track behavior of passenger car was studied. The vehicle driving trajectory and driving direction were defined, and a classification of the type of vehicle trajectories along the curves was developed. The statistical parameters of vehicle trajectory samples in free flow and their frequency curves and cumulative frequency curves were achieved, K-S test and chi-square test were used to test normal distribution and gamma distribution for collected sample data, and the probability density functions were given. At last, dispersion degree between vehicle trajectory random variable and the characteristic value of cumulative frequency curve in each key cross section in curves was analyzied. The proposed conclusion can provide theoretical support for the reasonable optimization of widen curve, design of alignment and the management of counter flow conflicts.

Bicycle capacity of borrowed-priority merge at unsignalized intersections in China

YANG Xiao-bao, HUAN Mei, SI Bing-feng, GAO Liang

2012, 21(2): 229-233.

[Abstract](479) [PDF 435KB](143)

Abstract:
To investigate bicyclists’ behavior at unsignalized intersections with mixed traffic flow, a bicycle capacity model of borrowed-priority merge was developed by the addition-conflict-flow procedure. Based on the actual traffic situation, the concept of borrowed priority, in which the major-road bicycles borrow the priority of major-road cars to enter the intersections when consecutive headway for major-steam cars is lower than the critical gap for minor-road cars, was addressed. Bicycle capacity at a typical unsignalized intersection is derived by the addition-conflict-flow procedure. The proposes model was validated by the empirical investigation. Numerical results show that bicycle capacity at an intersection is the function of major-road and minor-road car streams. Bicycle capacity increases with increasing major-road cars but decreases with increasing minor-road cars.

Unsupervised FIR adaptive filtering and its frequency domain analysis

LI Zhen-hua, CHEN Jia-bin, MA Tao

2012, 21(2): 234-239.

[Abstract](607) [PDF 339KB](164)

Abstract:
An unsupervised minimum mean square error FIR adaptive filtering (UAF) algorithm is proposed to estimate the system’s input signal. The algorithm only uses the system’s output signal and noise variance without requiring knowledge of a reference signal. The frequency analysis shows that the UAF is a multi-spot bandpass filter with passing frequency determined by the system’s input signal. Namely, the UAF chooses the expected frequency and extremely restricts the unwanted frequency signal by using weight-updating scheme in time domain. However, the UAF presents the Gibbs phenomenon since the ideal filter is infinitely long which is unrealizable. The simulation and experimental results show that the UAF could effectively reduce the amplitude of the noise and improve the signal to noise ratio.

Active contours with normally generalized gradient vector flow external force

ZHAO Heng-bo, LIU Li-xiong, ZHANG Qi, YAO Yu-hua, LIU Bao

2012, 21(2): 240-245.

[Abstract](705) [PDF 591KB](170)

Abstract:
Gradient vector flow (GVF) is an effective external force for active contours, but its isotropic nature handicaps its performance. The recently proposed gradient vector flow in the normal direction (NGVF) is anisotropic since it only keeps the diffusion along the normal direction of the isophotes; however, it has difficulties forcing a snake into long, thin boundary indentations. In this paper, a novel external force for active contours called normally generalized gradient vector flow (NGGVF) is proposed, which generalizes the NGVF formulation to include two spatially varying weighting functions. Consequently, the proposed NGGVF snake is anisotropic and would improve active contour convergence into long, thin boundary indentations while maintaining other desirable properties of the NGVF snake, such as enlarged capture range, initialization insensitivity and good convergence at concavities. The advantages on synthetic and real images are demonstrated.

Novel algorithm for pose-invariant face recognition

LIU Peng-zhang, SHEN Ting-zhi, ZHAO San-yuan, YUE Lei, YAN Xue-mei

2012, 21(2): 246-252.

[Abstract](859) [PDF 1146KB](132)

Abstract:
By combining the AdaBoost modular locality preserving projection (AMLPP) algorithm and the locally linear regression (LLR) algorithm, a novel pose-invariant algorithm is proposed to realize high-accuracy face recognition under different poses. In the training stage of this algorithm, the AMLPP is employed to select the crucial frontal blocks and construct effective strong classifier. According to the selected frontal blocks and the corresponding non-frontal blocks, LLR is then applied to learn the linear mappings which will be used to convert the non-frontal blocks to visual frontal blocks. During the testing of the learned linear mappings, when a non-frontal face image is inputted, the non-frontal blocks corresponding to the selected frontal blocks are extracted and converted to the visual frontal blocks. The generated virtual frontal blocks are finally fed into the strong classifier constructed by AMLPP to realize accurate and efficient face recognition. Our algorithm is experimentally compared with other pose-invariant face recognition algorithms based on the Bosphorus database. The results show a significant improvement with our proposed algorithm.

Low-complexity transceiver design scheme based on channel null-space feedback

NI Ji-qing, FEI Ze-song, XING Cheng-wen, KUANG Jing-ming

2012, 21(2): 253-257.

[Abstract](794) [PDF 382KB](150)

Abstract:
To reduce the negative impact of channel quantization errors, a low-complexity transceiver joint design scheme for both the transmit beamformers and receive combining vectors is proposed in the two-user multiple-input multiple-output (MIMO) system. In the scheme, the channel null-space quantization vector is used as the transmit beamformer of the interference user directly based on channel null-space feedback. Since the interference can be determined at the receiver, interference rejection combining (IRC) is jointly utilized to cancel the inter-user interference. Simulation results show that the proposed scheme can provide substantial sum-rate improvement especially at high SNR.

Large deflection of annular throttle-slices in shock absorbers

HE Li-ping, GU Liang, XIAO Jie-ping

2012, 21(2): 258-263.

[Abstract](653) [PDF 374KB](135)

Abstract:
A general analytical formula of large deflection for annular throttle-slices in shock absorbers was deduced. The Chien-perturbation method was used to derive the stiffness curve equation of a single throttle-slice in shock absorbers. The analytical formula of large deflection for superposed throttle-slices was deduced directly and generalized. The undetermined coefficients of analytical formula were obtained through the finite element method (FEM) and curve fitting. Numerical results show that the analytical formula has satisfactory accuracy.

Supervised polarimetric SAR classification method based on Fisher linear discriminant

WANG Peng, LI Yang, HONG Wen

2012, 21(2): 264-268.

[Abstract](792) [PDF 1763KB](139)

Abstract:
A supervised polarimetric SAR land cover classification method was proposed based on the Fisher linear discriminant. The feature parameters used in this classification method could be selected flexibly according to land covers to be classified. Polarimetric and texture feature parameters extracted from co-registered multifrequency and multi-temporal polarimetric SAR data could be combined together for classification use, without consideration of the dimension difference of each feature parameter and the joint probability density function of those parameters. Experimental result with AGRSAR L/C-band full polarimetric SAR data showed that a total classification accuracy of 94.33% was achieved by combining the polarimetric with texture feature parameters extracted from L/C dual band SAR data, demonstrating the effectiveness of this method.

Fusion of multi-spectral image and panchromatic image based on support vector regression

HU Gen-sheng, LIANG Dong

2012, 21(2): 269-277.

[Abstract](723) [PDF 5639KB](145)

Abstract:
In our study, support vector value contourlet transform is constructed by using support vector regression model and directional filter banks. The transform is then used to decompose source images at multi-scale, multi-direction and multi-resolution. After that, the super-resolved multi-spectral image is reconstructed by utilizing the strong learning ability of support vector regression and the correlation between multi-spectral image and panchromatic image. Finally, the super-resolved multi-spectral image and the panchromatic image are fused based on regions at different levels. Our experiments show that, the learning method based on support vector regression can improve the effect of super-resolution of multi-spectral image. The fused image preserves both high space resolution and spectrum information of multi-spectral image.

Effects of laser beam divergence angle on airborne LIDAR positioning errors

JIANG Li-fang, LAN Tian, GU Mei-xia, NI Guo-qiang

2012, 21(2): 278-284.

[Abstract](702) [PDF 359KB](228)

Abstract:
The influence of laser beam divergence angle on the positioning accuracy of scanning airborne light detection and ranging (LIDAR) is analyzed and simulated. Based on the data process and positioning principle of airborne LIDAR, the errors from pulse broadening induced by laser beam divergence angle are modeled and qualitatively analyzed for different terrain surfaces. Simulated results of positioning errors and suggestions to reduce them are given for the flat surface, the downhill of slope surface, and the uphill surface.

2012 Vol. 21, No. 2