JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Study on detonation velocity deficits of bending flexible detonation fuses

YE Yao-kun, WEN Yu-quan, YAN Nan

2011, 20(4): 427-432.

[Abstract](960) [PDF 384KB](286)

Abstract:
In order to study the detonation velocity deficits of bending flexible detonating fuses, a physical model and a theoretical mathematical equation of detonation velocity deficits for bending flexible detonation fuses were established based on the detonation wave's corner effects and delay time phenomenon by using non-dimensional analysis method. Besides, a semi-empirical formula of detonation velocity deficit for bending fuses in the same charge size was obtained through experiment and curve fitting. The result shows that an exponential relationship between the detonation velocity deficits and reciprocal of curvature radius.

Numerical calculation of JWL EOS parameters for explosives

HE Ning, XIANG Cong, ZHANG Qi

2011, 20(4): 433-437.

[Abstract](853) [PDF 309KB](246)

Abstract:
JWL equation of state (EOS) parameter for most energetic materials is blank, that makes it impossible for the numerical simulation of the explosive dynamic response and damage effects. In this paper, the numerical calculation of JWL EOS parameters for the gaseous, liquid and condensed source of the explosion was performed, the numerical simulation for the bottleneck problem of the dynamic response and damage effects for the aluminized explosives and some other non-ideal explosion source was solved, the visualization software for the detonation parameters and numerical parameters of JWL equation was developed. The results were relatively consistent with the experimental data.

Analysis of flowout gas field simulations and ignition methods for sulphuric gas wells

HUANG Ping, QIAN Xin-ming, SUN Wen-lei

2011, 20(4): 438-444.

[Abstract](788) [PDF 609KB](201)

Abstract:
To avoid potential human casualties and environmental pollution, flowout gas from sulphuric gas wells showing high concentrations of volatile gas must be neutralized by controlled ignition. Simulation model is built by using CFD software for flowout gas, and ignition methods are analyzed. The simulation results indicate that the optimal ignition zone is located between 150 mm and 570 mm above the gas flowout device. Two ignition methods, electronical and chemical, are developed. 12 and 6 experimental tests are performed respectively for these two methods. Results from the above tests verify that both approaches are successful in igniting the gas promptly and safely. In addition, our experience proves that the former way is more suitable for the fixed position ignition case, while the latter is more suitable for the long-distance or emergent ignition case. These two approaches can potentially be applied to a wide range of situations other than the fixed position ignition case and long distance ignition case.

Dynamic reconfiguration for en-route airspace

WANG Tong, WANG Zheng-jie, FAN Ning-jun

2011, 20(4): 445-450.

[Abstract](812) [PDF 546KB](238)

Abstract:
As the air traffic demand is anticipated to be increased significantly in the near future, dynamic and effective allocation of the airspace resource is becoming a world-wide focus in the research field of air traffic management (ATM). Taking the U.S. targeting the en-route airsapce, a dynamic airspace configuration (DAC) algorithm to reconfigure the airspace in consideration of higher efficiency and safety is presented. First, a modeling technique based on graph theory is proposed to generate a mathematical model for the airspace, and then, the graph model is partitioned into subgraphs for the purpose of sectorizatoin. The final step generates sector configuration with desirable geometry shape. Through analysis on the Cleveland airspace center (ZOB) in the U.S., the algorithm is proved to be robust to time-varying traffic load.

Real-time measurement of high rotational projectile axial acceleration based on 2-axis acceleration sensor

GUO Ze-rong, WU Ri-heng, LI Shi-yi

2011, 20(4): 451-455.

[Abstract](815) [PDF 343KB](183)

Abstract:
The real-time measurement principle of high rotational projectile's angular velocity based on 2-axis acceleration sensor and the axial acceleration measurement error caused by the installation error are discussed. The 2-axis acceleration sensor is applied to measure the high rotational projectile's angular velocity and the measurement value of axial acceleration, the axial acceleration of the high rotational projectile equals the measurement value of axial acceleration subtracting the centrifugal acceleration component, so that the high-accuracy real-time measurement of axial acceleration is realized. The memory test has confirmed the strike tally of the theoretical analysis and the test result. The measurement technique can satisfy the high-accuracy measurement of the high rotational projectile axial acceleration in the self-determination course correction fuze projectile.

Research on terminal maneuver strategy of anti-ship missiles

WANG Xiao-fang

2011, 20(4): 456-461.

[Abstract](790) [PDF 249KB](239)

Abstract:
To design the terminal maneuver strategy of an anti-ship missile, first,the analytical solution of miss distance when an anti-ship missile has planar weaving maneuver and three-dimension spiral maneuver is presented, in which not only the amplitude and frequency are considered but also the initial phase is taken into account. Next,based on the analytical solution of miss distance, the effects on the miss distance of the amplitude, frequency, initial phase of the anti-ship missile's maneuver acceleration and the order of flight control system of the air-ship missile are analyzed. Finally,the optimum weaving maneuver and spiral maneuver which make the miss distance be the largest under some conditions are designed, which is of important meaning for increasing the survival probability of the anti-ship missile.

Realization of proportional navigation and lateral acceleration autopilot for endoatmospheric kinetic interceptor with pulse thrusters

WANG Jiang, SHI Zheng-hai, LIN De-fu, QI Zai-kang

2011, 20(4): 462-465.

[Abstract](670) [PDF 304KB](165)

Abstract:
The guidance and control strategy for endoatmospheric kinetic interceptor controlled by lateral pulse thrusters was detailed. The pulse thruster control system was firstly proposed. The sample-and-hold approach was introduced to design a novel lateral acceleration autopilot on the basis of traditional two-loop topology. Combined with proportional navigation guidance law and the novel autopilot, the overall ballistic trajectory was presented and examined. Simulation results show that the pulse thruster control strategy can greatly improve the control system response speed and the maximal acceleration capability for realizing kinetic kill interception.

Measurement of laminar burning velocities and Markstein lengths near rich propane/air flammability limits under microgravity conditions

HU Jun, REN Tan

2011, 20(4): 466-471.

[Abstract](799) [PDF 394KB](219)

Abstract:
A small cubic closed vessel with schlieren measurement technique combined with high-speed video camera were used to study limit flame properties under microgravity conditions at atmospheric pressure and room temperature. The rich flammability limit of C₃H₈/air was determined to be 9.2% C₃H₈. Stretched flame propagation speeds, stretched laminar burning velocities and unstretched laminar burning velocities near rich C₃H₈/air flammability limits were measured at different equivalence ratios. Outwardly propagating spherical flames were used to study the sensitivities of the flame propagation speeds and laminar burning velocities to flame stretch using Markstein lengths. Unstretched laminar burning velocity at rich flammability limit was determined to be 1.09.cm/s. Lewis numbers were less than unity in rich C₃H₈/air and negative Markstein lengths were concluded. Absolute values of Markstein lengths were found to decrease linearly with equivalence ratios increase.

Numerical investigation of hydrodynamic tractor-retarder assembly under traction work condition

YAN Qing-dong, ZOU Bo, WEI Wei

2011, 20(4): 472-477.

[Abstract](612) [PDF 618KB](202)

Abstract:
To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition, a numerical simulation model of flow channel was established and tetrahedron unstructured grids were adopted in the meshing stage. The racing rotating speed of the brake wheels was calculated by computational fluid dynamics (CFD) calculation and interpolation, and then accurate boundary condition was applied to the CFD simulation to study the pressure and velocity distribution of internal flow field in hydrodynamic tractor-retarder assembly. Finally, the original characteristics were calculated by CFD post-processing analysis. Comparison of experimental data and flow field analysis results showed that the calculation tolerance of the torque ratioKand the efficiency η was less than 5%, and the calculation tolerance of the pump torque coefficient λ was less than 10%.

Experimental and numerical analysis of an air cleaner's acoustic performance

FENG Hui-hua, ZHAO Zhi-fang, ZUO Zheng-xing, LU Shou-wei

2011, 20(4): 478-482.

[Abstract](714) [PDF 496KB](226)

Abstract:
To improve acoustic performance of an air cleaner system, both experimental and theoretical studies were carried out. The air cleaner's acoustic numerical model was built by finite element methods (FEM). Acoustic parameters of filter paper imported in the FEM model were calculated according to experiential formulas. Based on the models, the cleaner's acoustic character of transmission loss (TL) was computed. To verify the numerical results, TL results of the real air cleaner with or without filter paper were tested by four-microphone transferring function method. The experimental results show that the filter paper influence acoustic performance of the air cleaner significantly, especially in mid and high frequency band, and should be considered in numerical simulation. Comparisons between experimental and numerical results show that the numerical model is accurate enough to be used in multi-scheme acoustic optimization. Based on our study, TL results of two schemes were calculated and analyzed, which is useful to the air cleaner's final design decision.

Design of the pressure regulation algorithm for active braking in vehicle ACC system

MA Guo-cheng, LIU Zhao-du, PEI Xiao-fei, Ye Yang

2011, 20(4): 483-489.

[Abstract](638) [PDF 455KB](182)

Abstract:
To develop the pressure control algorithm for active braking of adaptive cruise control (ACC) system, a test bench with real parts of the tested vehicle is built. With the dynamic analysis of the active braking actuators, it is demonstrated that different duty of pulse-width modulation (PWM) signals could control the pressure changing rate of the wheel cylinder. To obtain that signal, a modified proportional-integral -differential (PID) control algorithm is developed using the variable parameter method, the control value reset method, the dead zone method and the integral saturation method. Experimental results show that the delay and overshoot of the pressure response could be reduced considerably using the modified PID algorithm compared with the conventional one. The proposed pressure control algorithm could be used for the further development of the ACC's controller.

Electric vehicle simulation with battery in the loop

LI Si-guang, SULEIMAN Sharkh, ZHANG Cheng-ning, FRANK Walsh, HU Xiao-song

2011, 20(4): 490-495.

[Abstract](939) [PDF 372KB](210)

Abstract:
An electric vehicle simulation system with battery in the loop (BIL) is described in this paper. Virtual models are used for the other parts of power train including the electric motor/controller, transmission and vehicle dynamics, which allows the easy change of system parameters and rapid evaluation of vehicle and battery performance for different vehicle configurations. Tests were conducted using the system and the measurements (voltage and current, efficiency) obtained from the real battery were compared with those obtained from a standard nominal model of the battery. The results indicate that the measured voltage and current between the real battery and those obtained from the model are significantly different. Additionally, it is expected that the difference will increase significantly as the battery ages.

Simulation of volute tongue of small-size centrifugal compressor

LI Du, YANG Ce, ZHOU Mi, CHEN Shan

2011, 20(4): 496-501.

[Abstract](656) [PDF 659KB](212)

Abstract:
A high speed and small mass-flow-rate centrifugal compressor with original and modified volute tongue shape was simulated by 3D viscous Navier-Stokes equations. A sharp and a round tongue of volute were modeled to compare their pressure ratios and efficiency characteristics. The flow fields around volute tongues were investigated; the velocity and pressure distributions of volute inlet were studied by unsteady simulation. Static pressure fluctuation near volute tongue was monitored and transformed into amplitude spectrum to identify blade passing frequency influence. The results show that the tongue simplification can cause certain difference on pressure ratio and efficiency. The pressure and velocity distribution of volute inlet indicate obvious circumferential distortion due to volute tongue especially at low mass flow rate. In addition, the static pressure pulsation of volute inlet and the noise level in diffuser and volute increase significantly under low mass flow operating condition.

Rotor dynamic analysis of small vehicle gasoline turbocharger in semi-floating bearings

ZHANG Hong, ZHANG Xi, HE Nana

2011, 20(4): 502-508.

[Abstract](1011) [PDF 538KB](200)

Abstract:
The critical speed and unbalance response of a small vehicle gasoline turbocharger in semi-floating bearing are analyzed. The dynamical characters of semi-floating bush bearing used in small vehicle gasoline turbocharger were summarized by comparing the structure and shaft rigid mode of semi-floating bush bearings with those of floating bush bearings. The rotor model was built. The first, second and third mode of critical speeds of rotor system were computed, and the changes in the compressor or turbine bushing bearing clearances were analyzed. Compared with the experiment data, the accuracy and the rationality of computation model were verified. The unbalance response and time transient rotor response were also computed.

Technology of signal de-noising and singularity elimination based on wavelet transform

ZHAO Guo-jian, HAN Bao-ling, LUO Qing-sheng, WANG Xin

2011, 20(4): 509-513.

[Abstract](763) [PDF 380KB](211)

Abstract:
Based on wavelet transform theory, a method for signal de-noising and singularity detection and elimination is proposed, which can reduce the noises and express local singularity. Each singularity can also be detected and located through the local modulus maxima of wavelet transform. Simulation experiments are conducted with MATLAB software. The experimental results demonstrate that the method proposed in this paper is effective and feasible.

Ultrasonic transducer array tomography for detecting defect of metal plate based on Hilbert transformation

XU Han-hui, XU Chun-guang, ZHANG Yun-tao, LIU Long

2011, 20(4): 514-519.

[Abstract](679) [PDF 478KB](199)

Abstract:
Hilbert transformation and improved ellipse localization method is applied in ultrasonic transducer array tomography to detect defect of metal plate. By combining the improved ellipse localization method and time-reversal method, the new ultrasonic tomography algorithm employs smooth Hilbert envelope instead of discrete amplitude to reconstruct defect image. An ultrasonic tomography system with six transducers is built to evaluate the effectiveness of the new ultrasonic tomography algorithm. The S0 mode Lamb wave is excited on special condition,and the mode of received signal is identified by Vigner-Wille distribution. The gray value of image area is defined by envelope of the reflected S0 mode Lamb wave signal from defect boundary. Defect image can be reconstructed by summing gray value of all pixels in the image area. The experimentally reconstructed defect image shows that the new tomography algorithm based on Hilbert transformation is efficient for defect detection in metal plate.

New method for recognition of circular traffic sign based on radial symmetry and pseudo-zernike moments

FU Meng-yin, HUANG Yuan-shui, MA Hong-bin

2011, 20(4): 520-526.

[Abstract](905) [PDF 585KB](203)

Abstract:
Recognizing various traffic signs, especially the popular circular traffic signs, is an essential task for implementing advanced driver assistance system. To recognize circular traffic signs with high accuracy and robustness, a novel approach which uses the so-called improved constrained binary fast radial symmetry (ICBFRS) detector and pseudo-zernike moments based support vector machine (PZM-SVM) classifier is proposed. In the detection stage, the scene image containing the traffic signs will be converted into Lab color space for color segmentation. Then the ICBFRS detector can efficiently capture the position and scale of sign candidates within the scene by detecting the centers of circles. In the classification stage, once the candidates are cropped out of the image, pseudo-zernike moments are adopted to represent the features of extracted pictogram, which are then fed into a support vector machine to classify different traffic signs. Experimental results under different lighting conditions indicate that the proposed method has robust detection effect and high classification accuracy.

Constrained circular-patch-based texture synthesis

MA Rong-fei

2011, 20(4): 527-535.

[Abstract](956) [PDF 916KB](210)

Abstract:
Texture synthesis has been developed for several years. The traditional technique can generate a larger image from a small image while avoid feeling of repetition or uncontinuity. Some constrained synthesis methods which can synthesize image according to special location demand or other demands have been also proposed in recent years. However, in general, these constrained texture synthesis methods are simple and have few controllable factors to meet user's diverse needs. To control multiple-sample texture synthesis more flexibly in various aspects such as synthesis location, proportion and semantic objects, we present an interactive texture synthesis approach based on circular patches and constrained by objects according to a certain ratio. With this approach, source exemplars and the target image are firstly divided into several regions with different characters. Users can click the blocks in the source exemplars and the want-to-be-synthesized region in the target image, and then texture in the target image is synthesized with the corresponding regions in the source exemplars. In the process of texture synthesis, circular patch instead of square patch is used to eliminate the aliasing phenomena. Images are synthesized from multiple sample images with ratio constraint and experiments on images show that our approach can get effective results of ratio-constrained multi-sample synthesis.

Improved chirp scaling algorithm integrated motion compensation for parallel-track bistatic synthetic aperture radar

QI Chun-dong, ZENG Tao, LI Feng

2011, 20(4): 536-539.

[Abstract](749) [PDF 322KB](213)

Abstract:
To compensate motion errors of images from the parallel-track bistatic synthetic aperture radar (BiSAR), an improved chirp scaling algorithm (CSA) is proposed. Since velocity vector of the moving aircrafts in the parallel-track BiSAR system can not remain invariant in an aperture, an actual aperture is divided into subapertures so that it is reasonable to assume that the aircrafts move with constant acceleration vector in a subaperture. Based on this model, an improved CSA is derived. The new phase factors incorporate three-dimensional acceleration and velocity. The motion compensation procedure is integrated into the CSA without additional operation required. The simulation results show that the presented algorithm can efficiently resolve motion compensation for parallel-track BiSAR.

High-FM-linearity wideband chirp generator

HUANG Chao, REN Li-xiang, MAO Er-ke

2011, 20(4): 540-545.

[Abstract](845) [PDF 490KB](219)

Abstract:
An S-band wideband chirp generator using specially designed fast lock phase lock loop (FL-PLL) was demonstrated. To realize high linearity, structure of direct digital synthesizer (DDS) plus FL-PLL was used. DDS gives ideal linearity while FL-PLL retains the linearity and provides radio frequency. The system block diagrams were showed and the timing relationships of the components were provided. Two important considerations of the system, wideband loop and wideband voltage control oscillator (VCO), were discussed; meanwhile, after analyzing the considerations, corresponding solutions were presented. Measurement results show that the generated 2560.MHz to 2960.MHz chirp reaches a high FM linearity of 0.003%.

Adaptive blind equalizer based on least square support vector machine

MAO Zhong-yang, WANG Hong-xing, LI Jun, ZHAO Zhi-yong, SONG Heng

2011, 20(4): 546-551.

[Abstract](815) [PDF 354KB](204)

Abstract:
An adaptive blind support vector machine equalizer (ABSVME) is presented in this paper. The method is based upon least square support vector machine (LSSVM), and stems from signal feature reconstruction idea. By oversampling the output of a LSSVM equalizer and exploiting a reasonable decorrelation cost function design, the method achieves fine online channel tracing with Kumar express algorithm and static iterative learning algorithm incorporated. The method is verified through simulation and compared with other nonlinear equalizers. The results show that it provides excellent performance in nonlinear equalization and time-varying channel tracing. Although a constant module equalization algorithm requires that the signal has characteristic of constant module, this method has no such requirement.

Epoxidation of soybean oil with SO₃H-functional ionic liquid as catalyst

CAI Shuang-fei, WANG Li-sheng, LINGHU Rong-gang

2011, 20(4): 552-557.

[Abstract](876) [PDF 324KB](181)

Abstract:
Green technology for the preparation of epoxidized soybean oil (ESBO) is of significance. The epoxidation of soybean oil with peroxyacetic acid generated in situ from hydrogen peroxide and glacial acetic acid as monomers and SO₃H-functional ionic liquids 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate ([C₃SO₃HMIM][HSO₄] ) as catalyst was studied. The influence of stirring speed, hydrogen peroxide-to-ethylenic unsaturation molar ratio, acetic acid-to-ethylenic unsaturation molar ratio, catalyst loading and temperature on the relative percentage conversion to oxirane and the recycling properties of catalyst were examined. The rate constant and activation energy for epoxidation of soybean oil were found to be of the order of 10^-5.L/(mol·s) and 51.4.kJ/mol, respectively. The thermodynamic parameters of enthalpy, entropy and free energy of activation were found to be of 48.6.kJ/mol, -191.7.J/(mol·K) and 112.2.kJ/mol, respectively.

Thermal insulation and cooling properties of thermal barrier coatings of flame baffles

XU Wei-bao, LIU Bao-guo, SONG Qiu-zhi

2011, 20(4): 558-563.

[Abstract](584) [PDF 497KB](280)

Abstract:
In order to study the thermal insulation and cooling properties of thermal barrier coatings of a flame baffle, several ZrO₂thermal barrier coatings with different thicknesses were prepared on the surface of aluminium-alloy flame-baffle samples by plasma spraying. The relations between temperature and time of these samples were tested when they were heated by combustion flame. The relations between temperature of the coatings and the sample bodies and time were also tested when the samples at high temperatures were cooled by water. The experimental results indicated that ① the thicker the thermal barrier coatings, the better the thermal insulation effect of the thermal barrier; ② the higher the temperature, the more significant of the thermal insulation of the thermal barrier. Also, in the case of water-cooling, the cooling rate of the coatings was greatly subject to the plate body and the cooling rate of coatings below 1.0.mm was equivalent to that of the plate body.

Distribution in tissue and excretion in urine and feces of swertisin after intravenous administration to rats

LI Yu-juan, YANG Zhe-zhe, LI Yong-zhi, ZHANG Yu-shi, CHEN Bo

2011, 20(4): 564-570.

[Abstract](600) [PDF 342KB](194)

Abstract:
Swertisin contents in rat urine, feces and tissues were determined by reversed-phase high-performance liquid chromatography (RP-HPLC) method. Chromatographic separations were performed on a C₁₈column with acetonitrile-water (23∶77, v/v) as the mobile phase. The calibration curves were linear over the ranges of 0.175-35.0. μ g/mL for rat urine, 0.5-60.0. μ g/mL for rat feces, and 0.014 to 53.0. μ g/mL for all tissues. The inter- and intra-day precisions and accuracy for all measured samples were satisfactory. The fully validated method was applied for tissue distribution and excretion of swertisin in rat urine and bile after intravenous administration. The maximum level of swertisin was found in kidney, which reached 83.87± 6.36. μ g/g. In rat heart, swertisin was hardly detected under used experimental conditions. Swetisin level in liver, kidney, stomach, smooth muscle and skeletal muscle continued to decrease from 5 to 60.min. Swertisin showed increasing tendency in intestine, spleen and testis tissues at scheduled time points. Detectable swertisin was found in brain and lung tissue. Totally 11.9% swertisin dose was cumulatively excreted from urine in 60.h after intravenous administration. There was small amount of swertisin in rat feces and the cumulative excretion level reached 4.59% of intravenous dose in 60.h.

2011 Vol. 20, No. 4