JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Numerical simulation of the parabolic shell surface under blast wave loading

HOU Jun-liang, JIANG Jian-wei, FANG Yu-jun

2012, 21(4): 427-433.

[Abstract](1065) [PDF 984KB](59)

Abstract:
Deformation of parabolic shell surface under explosion shock waves is a complex dynamic problem. Because of reflection and interference of blast wave, it's hard to analytically delineate the dynamic responds of radar parabolic shell surface on blast wave. To gain the characteristics of thin shell deformation under impulsive loading of blast wave, numerical simulation methods for blast load on the shell structure was studied and analyzed. Euler-Lagrange numerical simulation was implemented by AUTODYN code to simulate the problem. Through analysis on deflection feature of radial position under different explosive mass and detonation height, an equation was founded by fitting the deflection results from numerical simulation results of shockwave loading. Experiments were arranged to confirm the validity of the formula. The results gained by simulation are consistent with experiments, and the formula can be used to delineate the deflection of aluminum alloy parabolic shell under blast loading.

Compound control allocation strategy of dual aero/jet vane control missile

GAO Feng, TANG Sheng-jing, SHI Jiao, GUO Jie

2012, 21(4): 434-441.

[Abstract](1142) [PDF 430KB](35)

Abstract:
To solve the control allocation problem of dual aero/jet vane control missile, dynamics equations in longitudinal plane are derived, and the structure of compound control loop is designed based on attitude autopilot. Four brief compound control allocation strategies are researched and analyzed. Furthermore, a new strategy called chain combination variable proportional coefficient strategy based on rudder effect is presented. By simulation of initial climb trajectory, the characteristics of all the strategies are researched, and the results illustrate that the new strategy can meet the requirement well.

Effect of gas compressibility on the characteristics of a synthetic jet flow

DING Ying-tao, SU Ri-na, LI Bo

2012, 21(4): 442-446.

[Abstract](870) [PDF 461KB](11)

Abstract:
Numerical simulations are performed to investigate the effects of gas compressibility on the synthetic jet flow. A slot synthetic jet and a circular orifice synthetic jet are simulated assuming 2D and axis-symmetric behavior. The velocity of orifice, frequency response and the compressibility are studied through simulation. The numerical results are validated against existing experimental and analytical data, and good agreement are obtained. Gas compressibility effects on the synthetic jet flow are discussed. In conclusion, for the two kinds of different synthetic jets studied in this paper, the critical values of Mach number are 0.082 and 0.033.

Research on active vibration control on a piezoelectric intelligent flexible beam

WU Da-fang, HUANG Liang, WANG Yue-wu, MU Meng, ZHOU An-feng

2012, 21(4): 447-452.

[Abstract](972) [PDF 372KB](10)

Abstract:
The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible cantilever beam is implemented based on the independent modal control law. Experimental results show that the structural damping of the flexible cantilever beam is effectively improved and an excellent degree of vibration suppression is achieved with the active vibration control strategy.

Experimental study of the mechanical property of barrel processed by cold radial forging

LIU Li-li, FAN Li-xia, DONG Xue-hua

2012, 21(4): 453-459.

[Abstract](1117) [PDF 376KB](33)

Abstract:
The cold radial forging process usually introduces some changes of the material, such as the increased strength, the decreased plasticity and the introduction of anisotropic mechanical property. To obtain the changes of mechanical property of barrel processed by cold radial forging, the tangential mechanical properties of the barrel blank and the forged barrel are measured with a designed test based on the plastic deformation analysis for a barrel and by applying internal pressure, and their axial mechanical properties are measured by the tensile test. The changes of mechanical property of barrel processed by cold radial forging are obtained by comparing the mechanical properties of the barrel blank and the forged barrel. The tangential and axial flow stresses of the barrel blank and the forged barrel are also presented.

Bearing loads of dual rotor-bearing system under stationary and transient conditions

LIU Shu-hui, WANG Guo-li, ZHU Qing-le, ZHOU Nian-fa, CHEN Yong

2012, 21(4): 460-465.

[Abstract](972) [PDF 465KB](12)

Abstract:
Aimed at aeroengine vibration failure, bearing loads of dual rotor-bearing system caused by unbalance are calculated under stationary and transient conditions. The three-dimensional (3-D) finite element method (FEM) model of dual rotor-bearing system was established. Applying the rotor dynamics function of Ansys 12.0, bearing loads were calculated under various unbalance force in stationary condition, and the transient vibration characteristics and the effect of acceleration on bearing loads were discussed. On the basis of simulation results, the influence disciplines of unbalance on bearing loads and theoretic reference for reducing bearing loads during start-up were obtained.

Road identification method based on angular acceleration of vehicle driving wheel

LI Fu-qing, LIU Zhao-du

2012, 21(4): 466-471.

[Abstract](818) [PDF 329KB](14)

Abstract:
The fundamental principle of road identification by using angular acceleration of driving wheels was demonstrated in this paper. Based on the analysis of energy conversion and parameters variation during the vehicle drive slip process, the change of adhesion coefficient relative to the angular acceleration were theoretically studied experimentally validated. The variation shows that the change of adhesion coefficient relative to the angular acceleration and the change of slip ratio in the drive slip process have same trend-both of them exist an only optimal angular acceleration corresponding to the peak value of adhesion coefficient. The peak adhesion coefficient of the prototype vehicle is about 0.14 on the ice-covered road surfaces, with the corresponding optimal angular acceleration of about 23.5.rad/s²and optimal slip ratio of about 9.4%.

Improved single-neuron PID controller for DC motor applied in robot system

SU Xiao-dong, LUO Qing-sheng, ZHI Wei

2012, 21(4): 472-478.

[Abstract](954) [PDF 813KB](19)

Abstract:
An improved single-neuron proportional integral derivative (PID) controller and a new method to build the DC motor system were presented in the article. In the simulation, the robot arm is considered as an external load to DC motor. Both the motor module and the load module are created in Simulink to achieve simulation results closer to real robot system. In this way, it can well verify the performance of the improved single-neuron PID controller, which is a combined controller of normal PID controller and single-neuron PID controller. Besides, an intelligent switcher can help to realize the function of choosing a better control algorithm according to motor’s velocity output. Simulated results confirm the rapid and stable response of the improved PID controller. Moreover, the improved single-neuron PID controller has an excellent ability to overcome the load impact and supress the jamming signals. At last, a GUI interface platform is built to make the controller easier to be applied in other robot systems.

Robustness and precision evaluation of the form error of micro-structured surfaces using real coded genetic algorithm

ZHOU Jing-bo, SUN Tao

2012, 21(4): 479-486.

[Abstract](1057) [PDF 1362KB](18)

Abstract:
To obtain the form error of micro-structured surfaces robustly and accurately, a form error evaluation method was developed based on the real coded genetic algorithm (RCGA). The method employed the average squared distance as the matching criterion. The point to surface distance was achieved by use of iterative method and the modeling of RCGA for the surface matching was also presented in detail. Parameter selection for RCGA including the crossover rate and population size was discussed. Evaluation results of series simulated surfaces without form error show that this method can achieve the accuracy of root mean square deviation (S_q)less than 1 nm and surface profile error (S_t)less than 4.nm. Evaluation of the surfaces with different simulated errors illustrates that the proposed method can also robustly obtain the form error with nano-meter precision. The evaluation of actual measured surfaces further indicates that the proposed method is capable of precisely evaluating micro-structured surfaces.

Analysis of opposing left-turn conflicts based on traffic conflict technology

MAO Yan, WANG Wu-hong, GUO Wei-wei, DING Chen-xi, XIA Shuang-chen

2012, 21(4): 487-491.

[Abstract](938) [PDF 328KB](16)

Abstract:
The relationship between the opposing left-turn conflict and the traffic participants was analyzed in this study. Based on the traffic conflict technology, the image data were collected in a real traffic situation. The relationship was investigated under two different conditions. The number of opposing left-turn conflicts was positively correlated with the number of left-turn vehicles while the ratio of left-turn vehicles to opposing vehicles was less than 1, and showed a positive correlation with the number of opposing-through vehicles when the ratio of left-turn vehicles to opposing vehicles was more than 1. In other words, the opposing left-turn risk was positively correlated with the number of the minor traffic participants, which had a negative effect on the whole traffic system operation.

Determining capacity of multimodal multi-commodities freight transportation network from critical link volumes

XU Wang-tu

2012, 21(4): 492-497.

[Abstract](764) [PDF 347KB](10)

Abstract:
The commodity transportation capacity between all origin-destination (OD) pairs over the multimodal multi-commodities freight transportation network (MMFTN) is determined. A multi-objectives mathematical model is formulated for determining the OD capacity over the MMFTN according to a transporting capacity matrix that increased from the reference matrixes. The corresponding incremental factor for estimating the capacity matrix is obtained via the maximal likelihood estimation method that samples data of differences between the estimated commodity volumes and carrying capacities of the critical links. The proposed formulations are tested by an experimental highway and railroad freight transportation network in an existing literature. The relevant results of OD capacities are displayed and applicability of the algorithm is certified.

Comprehensive analysis of pedestrian speed under different conditions in Beijing

MA Ling-ling, HAN Bao-ming, LI De-wei

2012, 21(4): 498-503.

[Abstract](784) [PDF 325KB](16)

Abstract:
Factors influencing pedestrians’ speed were investigated. They included types of pedestrian facilities, the accompanying numbers, gender, age, purpose of trips and surrounding pedestrians. The data mining technique of statistical package for the social science (SPSS) was used to filter and analyze the data of pedestrians’ speed under different conditions. The differences among influencing factors on pedestrians’ speed was investigated by comparing the diagrams generated by SPSS. Through comprehensive analysis, including quantitative and qualitative analysis, a pedestrian’s speed was influenced significantly by the facilities, his surrounding pedestrians and his own personality.

Adaptive switching control of a class of nonlinear systems based on mixed multiple models

CAO Qi-min, ZHANG Yan-xia

2012, 21(4): 504-509.

[Abstract](807) [PDF 322KB](13)

Abstract:
The transient behaviors of traditional adaptive control may be very poor in general. A practically feasible approach to improve the transient performances is the adoption of adaptive switching control. For a typical class of nonlinear systems disturbed by random noises, mixed multiple models consisting of adaptive model and fixed models were considered to design the switching control law. Under certain assumptions, the nonlinear system with the switching control law was proved rigorously to be stable and optimal. A simulation example was provided to compare the performance of the switching control and the traditional adaptive control.

Description method of conceptual model based on the ontology

CHEN Xin, DUAN Feng, ZHANG Ying-chao

2012, 21(4): 510-517.

[Abstract](1940) [PDF 377KB](13)

Abstract:
The conceptual model is the first time abstraction of the real world. The traditional conceptual model description method based on the UML and the text usually has the semantic ambiguity problem. The formal description method lacks the mechanism of integrity and consistency check. Therefore both of them cannot support the simulation scenario description and the model composability. A simulation conceptual description method based on ontology is put forward. According to the OWL language which was put forward by the W3C organization, a conceptual model description language is established. The OWL language semantic element in the description function in the military conceptual model is introduced. Then two layers of the military conceptual model framework are built up based on the general ontology and the domain ontology. In the general ontology, the class and property definition are given. While in the domain ontology, they are extended and a related example is given. The technique advantages of our method include the mechanism of conceptual model consistency and integrity check, the support of composable simulation models, and automatic creation of simulation scenario.

A fast and effective fuzzy clustering algorithm for color image segmentation

WANG Gai-hua, LI De-hua

2012, 21(4): 518-525.

[Abstract](859) [PDF 1652KB](13)

Abstract:
A fast and effective fuzzy clustering algorithm is proposed. The algorithm splits an image inton×nblocks, and uses block variance to judge whether the block region is homogeneous. Mean and center pixel of each homogeneous block are extracted for feature. Each inhomogeneous block is split into separate pixels and the mean of neighboring pixels within a window around each pixel and pixel value are extracted for feature. Then cluster of homogeneous blocks and cluster of separate pixels from inhomogeneous blocks are carried out respectively according to different membership functions. In fuzzy clustering stage, the center pixel and center number of the initial clustering are calculated based on histogram by using mean feature. Then different membership functions according to comparative result of block variance are computed. Finally, modified fuzzyc-means with spatial information to complete image segmentation are used. Experimental results show that the proposed method can achieve better segmental results and has shorter executive time than many well-known methods.

Implementation of a kind of FPGA-based binary phase coded radar signal processor architecture

TIAN Li-yu, SUN Mi, WAN Yang-liang

2012, 21(4): 526-531.

[Abstract](1004) [PDF 874KB](13)

Abstract:
A flexible field programmable gate array based radar signal processor is presented. The radar signal processor mainly consists of five functional modules: radar system timer, binary phase coded pulse compression(PC), moving target detection(MTD), constant false alarm rate(CFAR) and target dots processing. Preliminary target dots information is obtained in PC, MTD, and CFAR modules and Nios II CPU is used for target dots combination and false sidelobe target removing. System on programmable chip(SOPC) technique is adopted in the system in which SDRAM is used to cache data. Finally, a FPGA-based binary phase coded radar signal processor is realized and simulation result is given.

Tracking error analysis and simulation of FLL-assisted PLL

TIAN Tian, AN Jian-ping, ZHANG Ruo-bing

2012, 21(4): 532-537.

[Abstract](2652) [PDF 336KB](38)

Abstract:
In order to solve problems in high dynamic environment, a frequency-locked loop (FLL) assisted phase-locked loop (PLL) is put forward for carrier tracking. On the basis of the analysis of discriminators, the total phase error of the tracking loop is analyzed and a general error expression is derived. By using linearization and Jaffe-Rechtin coefficients, the performance of a special first order FLL-assisted second order PLL is analyzed to get a closed expression. Analysis results and simulations show that there exist an optimal FLL loop bandwidth and a optimal PLL loop bandwidth which can make the phase jitter much less than that when the PLL is used alone.

Implementation of low-density parity-check codes decoder for CCSDS standard

LI Xiao-feng, AN Si-ning, ZHAN Tian-xiang

2012, 21(4): 538-542.

[Abstract](875) [PDF 308KB](15)

Abstract:
The complexity/performance balanced decoder for low-density parity-check (LDPC) codes is preferred in practical wireless communication systems. A low complexity LDPC decoder for the Consultative Committee for Space Data Systems (CCSDS) standard is achieved in DSP. An approximate decoding algorithm, normalized min-sum algorithm, is used in the implementation for its low amounts of computation. To reduce the performance loss caused by the approximation, the parameters of the normalized min-sum algorithm are determined by calculating and finding the minimum value of thresholds through density evolution. The minimum value which indicates the best performance of the decoding algorithm is corresponding with the optimized parameters. In implementation, the memory cost is saved by decomposing the parity-check matrix into submatrices to store and the computation of passing message in decoding is accelerated by using the intrinsic function of DSP. The performance of the decoder with optimized factors is simulated and compared with the ideal BP decoder. The result shows they have about the same performance.

Application of improved BPNN in image restoration-learning coefficient

Umar Farooq, SHEN Ting-zhi, Muhammad Imran, ZHAO San-yuan, Sadia Murawwat, WANG Qing-yun

2012, 21(4): 543-546.

[Abstract](1204) [PDF 733KB](16)

Abstract:
A new method of artificial intelligence based on a new improved back propagation neural network (BPNN) algorithm is partially applied in the problem of image restoration. In order to overcome the inherited issues in conventional back propagation algorithm i.e. slow convergence rate, longer training time, hard to achieve global minima etc., different methods have been used including the introduction of dynamic learning rate and dynamic momentum coefficient etc. With the passage of time different techniques has been used to improve the dynamicity of these coefficients. The method applied in this paper improves the effect of learning coefficientηby using a new way to modify the value dynamically during learning process. The experimental results show that this helps in improving the efficiency overall both in visual effect and quality analysis.

Influence of O/Ar ratio on the properties of NiO thin film grown with the method of radio-frequency magnetron sputtering

WANG Xin, TANG Hai-ying, LI Ye, QIN Xu-lei, DUANMU Qing-duo, YU Yang

2012, 21(4): 547-550.

[Abstract](1018) [PDF 279KB](23)

Abstract:
In order to obtain high quality NiO thin film grown with the radio-frequency magnetron sputtering method, the influence of O/Ar ratio on the structure, band-gap, resistivity and optical transmittance of NiO thin films were studied. It was found that the obtained NiO thin film showed (111) preferred orientation and higher transparency in the visible region. With the increasing of O/Ar ratio from 1∶7 to 8∶2, the optical transmittance of NiO thin films decreased and the optical band-gap was between 3.4.eV and 3.7.eV, and the sheet resistivity decreased from 5.4×10⁷. Ω /□ to 1.0 ×10⁵. Ω /□. Our study shows that the properties of NiO thin films can be adjusted in a wide range by adjusting the O/Ar ratio in the sputtering process.

Electroless plating of carbon nanotubes and their millimeter-wave absorbing properties

YIN Yan-hua, FU Min, ZHAO Jing-lei, WANG Chun-fang

2012, 21(4): 551-557.

[Abstract](671) [PDF 2888KB](9)

Abstract:
A method of electroless plating was utilized to deposit Cu, Ni, Co, Ag on the surface of carbon nanotubes (CNTs) respectively, in order to prepare millimeter-wave absorbing materials. Field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS) were used to observe morphologies and chemical compositions of the samples respectively. Millimeter-wave radiometer imaging detection was employed to measure the absorbing properties of the samples. FE-SEM and EDS results demonstrate the effectiveness of successful metal deposition. The results of millimeter-wave radiometer imaging detection reveal that the millimeter-wave absorbing properties of electroless-silver plating are better than other kinds of samples.

Thermal aging behavior of high performance poly(vinyl alcohol) hydrogel

TANG Qi-heng, NIU Run-li, YANG Rong-jie, LI Xiao-dong, HE Ji-yu

2012, 21(4): 558-563.

[Abstract](811) [PDF 386KB](10)

Abstract:
The thermal aging behavior of poly(vinyl alcohol) (PVA) hydrogel was studied at four different temperatures of 40.℃, 50.℃, 60.℃ and 70.℃ in one year. The samples of PVA hydrogel were closely covered by plastic film. The changes of their chemical structures and physical properties during aging were measured through different measurable techniques including tensile testing, gel permeation chromatography (GPC), viscosity analysis, and Fourier transform infrared (FTIR) spectrum. The results showed that the molecular weight of PVA in hydrogel changed little with time and temperature. FTIR spectra of PVA in all the samples were similar to those of the original samples. The tensile strength of PVA hydrogel didn’t change until the 330^thdays.

Study of intumescent flame-resistant fluoroelastomer

LIAO Qiu-heng, HAO Jian-wei, DU Jian-xin

2012, 21(4): 564-570.

[Abstract](785) [PDF 2395KB](14)

Abstract:
The efficiency of different intumescent flame-retardant (IFR) formulations designed to improve the flame resistance of fluoroelastomer (FKM) composites was studied. The proportion of ammonium polyphosphate (APP) with charring-foaming agent (CFA) in IFR systems, and the addition of synergists zinc borate (ZB) and ketonealdehyde resin (KR120) were investigated to show their effect on flame resistance of FKM. According to flame resistance tests, when the mass ratio of APP to CFA was 4∶1 as well as the loadings of IFR, ZB, KR120 were 83 parts per hundred resin (phr), 13phr, 25phr, respectively, the FKM-KR120/IFR-ZB composites had good synergetic flame resistant effect. TGA data showed that IFR and synergists could obviously lower the maximum weight loss rate of FKM composites and effectively increase the char residue at high temperature. The morphological structures of the composites observed by scanning electron microscopy (SEM) demonstrated that the addition of ZB and KR120 could clearly reduce the cracks in char residue and make the char layer structure more integrated and compact.

2012 Vol. 21, No. 4