JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Strain Effect of Manganin Transverse Piezoresistive Gauge and Measurement of Dynamic Transverse Stresses

DUAN Zhuo-ping, OU Zhuo-cheng, CAI Shao-jia, HUANG Feng-lei

2010, 19(3): 0253-258.

[Abstract](489)

Abstract:
Manganin piezoresistive gauges have been extensively used in dynamic stress measurement for decades. It is noted, however, that when used to measure transverse stresses, considerable strain effect is caused as the consequence of change of electrical resistance resulted from bending of wires in the longitudinal-strain-experiencing sensing element of the gauge, a phenomenon discussed in this paper theoretically as well as experimentally. This effect yields unwanted signals to blend with output piezoresistive signals and is not negligible, hence decreases measurement accuracy sizably if not properly handled. To overcome this drawback, a new type of manganin transverse piezoresistive gauge has been developed by authors of this paper, which can reduce the resistance increment to acceptable low level so as to effectively bring the adverse effect under control.

New CFD Validation Method with Application to Verify Computations of Near Wall Flows

YU Yong

2010, 19(3): 0259-263.

[Abstract](623)

Abstract:
For highRenumber flows, a new computational fluid dynamics (CFD) validation method, namely, wall-surface compatibility criteria method and also called Gaos criteria, is proposed to verify near wall flows. As examples, Gaos criteria method and other two CFD verification methods (analytic solutions method and grid convergence analysis) are used to verify FLUENTs near wall flows solutions for two-dimensional incompressible laminar stagnation-point flows. The exact solution of the Navier-Stokes equations for laminar stagnation-point flows satisfy accurately all Gaos criteria, numerical simulations of laminar stagnation-point flows show that when physical parameters (the pressure coefficient and the Stanton number at wall surface) achieve convergence with more and more fine-screen grid, a part of Gaos criteria are not satisfied.

Study on Echo Time-Delay Estimation of Pulsed Laser Fuze

GUO Hua-ling, DENG Jia-hao, SANG Hui-ping, CAI Ke-rong

2010, 19(3): 0264-267.

[Abstract](1000)

Abstract:
Pulse laser range detector is to measure the distance by estimating the time delay between the emitting pulse and echo pulse. In this paper, a mathematical model for the target echo signal of laser fuze has been established; in accordance with this model, the formulas for echo time-delay estimation and for amplitude estimation based on least squares criterion have been deduced. It is argued and simulated that the resolution of echo time-delay estimation could be improved through multi-reference correlation approach. Experiments illustrate that the approach enables pulsed laser fuze to perform high-precision ranging under a low signal-to-noise ratio condition.

Catalysis of Active Carbon Supporting Transition Metal Oxides for Pyrotechnical Reagent with Potassium Perchlorate

QIAN Xin-ming, DENG Nan, SUN Wen-lei, WEI Si-fan

2010, 19(3): 0268-273.

[Abstract](689)

Abstract:
In order to improve the pyrotechnical reagent with potassium perchlorate, composite catalyst of active carbon supporting transition metal oxides (TMO), Fe₂O₃and CuO, were prepared and added into pyrotechnical reagent with potassium perchlorate. Accelerating rate calorimeter (ARC) was used to study the catalysis of pyrotechnical reagent which is consisted of potassium perchlorate and composite catalyst. Composite catalyst of both Fe₂O₃and CuO supported by active carbon can catalyze pyrotechnical reagent with potassium perchlorate. Furthermore, it can lower the apparent activation energy and accelerate the reaction with a smaller quantity than that with Fe₂O₃and CuO. The maximal reaction rate of pyrotechnical reagent with potassium perchlorate mixed with Fe₂O₃/active carbon and CuO/active carbon is 8.31min^-1and 9.13min^-1, which is 1.74times and 1.91times of pyrotechnical reagent mixed with no catalyst; time to maximal rate was 18.99min and 1.96min respectively, which is lower than pyrotechnical reagent mixed with no catalyst by 86.46% and 98.67%; the apparent activation energy is 368.10kJ ·mol^-1and 325.29kJ ·mol^-1, which is lower than pyrotechnical reagent mixed with no catalyst by 31.89% and 39.81% respectively.

Dynamic Analysis and Structural Optimization of a Novel Palletizing Robot

LI Jin-quan, DING Hong-sheng, DUAN Bing-lei, NAN Qian, FU Tie

2010, 19(3): 0274-278.

[Abstract](716)

Abstract:
A novel palletizing robot is presented and developed. By using the Newton-Euler method and the principle that the instantaneous inertial force system could be transformed into a static system, the force equilibrium equations of the whole robot and its subsystem were derived and the robots dynamic models were established. After that, an example simulation was performed by using Matlab software and the structural optimization of the robots key parts were discussed and analyzed in ANSYS platform. The results show that the dynamic models are correct and can be helpful for the design, validation and kinetic control based on dynamics of this kind of palletizing robots.

ICM Method Combined with Meshfree Approximation for Continuum Structure

LONG Kai, ZUO Zheng-xing, XIAO Tao, Rehan H.Zuberi

2010, 19(3): 0279-285.

[Abstract](704)

Abstract:
The independent continuous mapping(ICM) method is integrated into element free Galerkin method and a new implementation of topology optimization for continuum structure is presented. To facilitate the enforcement of the essential boundary condition and derivative of various sensitivities, a singular weight function in element free Galerkin method is introduced. Material point variable is defined to illustrate the condition of material point and its vicinity instead of element or node. The topological variables field is constructed by moving least square approximation which inherits the continuity and smoothness of the weight function. Due to reciprocal relationships between the topological variables and design variables, various structural responses sensitivities are derived according to the method for calculating the partial derivatives of compound functions. Numerical examples indicate that checkerboard pattern and mesh-dependence phenomena are overcome without additional restriction methods.

Thermal Analysis of Vehicular Twin-Tube Hydraulic Gas-Precharged Shock Absorbers

YAO Ming-tao, GU Liang, GUAN Ji-fu

2010, 19(3): 0286-292.

[Abstract](646)

Abstract:
In this study of temperature rising in vehicular twin-tube hydraulic gas-precharged shock absorbers, thermodynamic analyses were conducted via simulations. Equations on heat conduction, heat convection as well as radiation were derived by applying certain laws governing heat transfer; an equivalent thermal resistance network model of a shock absorber undergoing heat transfer was established innovatively; moreover, the shock absorber’s thermodynamic model of control volume system was built by using the first law of thermodynamics; and finally, time required for shock absorber to reach thermal equilibrium and corresponding value of steady temperature were calculated by programming. In this way, a lower thermal equilibrium temperature will be achieved, hence help to improve reliability of shock absorbers in work by of fering low ambient temperature, by reducing amplitudes and frequencies of external incentives exerted on them and by increasing flow rate of ambient air passing around them.

Research on Simulation and Prediction of Internal Combustion Engine Structural Acoustic Radiation

ZHANG Bao-cheng, SHI Yuan-yuan, ZHANG Zi-ying

2010, 19(3): 0293-297.

[Abstract](638)

Abstract:
With the purpose of efficiently predicting structural radiated noise of internal combustion engine(I.C.E.), a new simulation technique is introduced, which is an approach based on boundary element method(BEM), acoustic transfer vector(ATV) technique and coupled boundary element model and finite element model (BEM-FEM) approach. Analyses of vibration exciting loads, computing structural dynamic characteristics and dynamic responses have led to theoretical results, which are tested on an L6 diesel engine to validate this proposed technique in engineering practice.

Combustion Characteristics of a Single Cylinder Spark Ignition Engine Fueled with Coal Mine Methane

ZHANG Xin, LI Cong-xin, XU Jian

2010, 19(3): 0298-304.

[Abstract](502)

Abstract:
An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane (CMM). The CMM was simulated by the compressed nature gas (CNG)/nitrogen blend fuels. The cylinder pressure was measured. The maximum heat release ratio, the flame development duration and the main combustion duration were analyzed with the nitrogen volume fraction in the blends changing from 0% to 35%. The results indicate that the maximum cylinder pressure, the maximum rate of pressure, the flame development duration and the main combustion duration increase and the maximum rate of heat release decreases with increasing nitrogen fraction. When the level of nitrogen volume fraction in coal-mine methane is lower than 20%, the combustion process of engine is stable. But with the level of nitrogen volume fraction over 30%, the cycle to cycle combustion variation is large, especially under low load condition.

Controlling of NO_xEmitted from a Diesel Engine Fueled on Biodiesel: Theoretical Modeling and Experimental Evaluation

Asad Naeem Shah, GE Yun-shan, TAN Jian-wei, LIU Zhi-hua, ZHAO Hong

2010, 19(3): 0305-311.

[Abstract](574)

Abstract:
The development of a diesel engine model using one-dimensional (1-D) fluid-dynamic engine simulation codes, and its validation using experimental measurements are described in this paper. The model was calibrated by running the engine on an electric dynamometer at eight steady-state operating conditions. The refined engine model was used to predict the oxides of nitrogen (NO_x) less than those measured earlier in the experiments, and hence to recommend changes in the engine for the verification of the results. The refined engine model is greatly influenced by the start of injection angle (ψ), ignition delay (φ), premix duration (D_P), and main duration (D_M) for the prediction of reduced NO_xemissions. It is found that optimumψis 6.5° before top dead center (BTDC). At this angle, the predicted and experimental results are in good agreement, showing only a difference of up to 4%, 6.2%, and 7.5% for engine performance, maximum combustion pressure (P_max), and NO_x, respectively.

Turbocharger Noise Prediction Using Broadband Noise Source Model

LI Hui-bin, SUN Zhen-lian, PENG Xin

2010, 19(3): 0312-317.

[Abstract](624)

Abstract:
The noise prediction of the turbocharger is studied. The broadband noise source model is employed to predict the near-field noise of the turbocharger. The 3D software Solidworks is adopted to establish the model blades and inlet of turbocharger compressor, then this 3D model is introduced into the software CFD to calculate the flow-field under different inlet shapes, different blades shapes and different clearances between casing and impeller. On the base of the above simulation, the broadband noise source model is employed to calculate and analyze the near-field noise. The calculation shows that compressor static pressure values and the sound power values near the impeller outlet are the largest. Through the noise calculation by using broadband noise source model under different inlet shapes and blade shapes, we find that the noise level of the inlet of cylindrical and cone types are smaller. Compared with the current widespread used backward skewed or radial blades, there is little difference of the noise value of the inlet of the forward skewed blades.

Numerical Study on Neck Injury Under Different Postures in Vehicle Side Impact

LI Zhi-gang, ZHANG Jin-huan, MA Chun-sheng, LAI Qing-xin

2010, 19(3): 0318-323.

[Abstract](735)

Abstract:
Neck injury is a severe problem in traffic accidents. While most studies are focused on the neck injury in rear and front impacts, few are conducted in side impact. This study focuses on the difference of neck injury under different postures and the difference of 7 cervical vertebras under the same posture using the method of prescribed structure motion(PSM). The analytical results show that the maximum changes of mean force and mean moment of 7 cervical vertebras under 8 different postures are 20% and 47% respectively. The variation of each cervical vertebra is different under different neck postures. Up cervical vertebras (C1-C4) and low cervical vertebras (C5-C7) suffer different forces and moments under the same neck posture. Generally speaking, No.6 (neck right leaning 40°) is the posture with lowest neck injury risk.

Analysis and Numerical Modeling of a 20W Microwave Electrothermal Thruster

GAO En-yu, Sven G. Bilén, YANG Shu-xing

2010, 19(3): 0324-330.

[Abstract](666)

Abstract:
The microwave electrothermal thruster (MET) is an electric propulsion device that uses an electromagnetic resonant cavity within which free-floating plasma is ignited and sustained in a propellant gas. The thrust is generated when the heated propellant gas is exhausted out of a gas-dynamic nozzle. For an empty cavity without any perturbing regions—e.g., dielectric regions or antenna regions—it is fairly straightforward to accurately calculate the cavitys resonant frequency and describe the electric field intensity distribution within the cavity. However, actual METs do contain perturbing regions, which means that analytical solutions are no longer possible to fully characterize the device. Hence, the numerical methods to simulate the electric field intensity and distribution within the resonant cavity were employed. The simulation results are that with the cap height increasing, the resonant frequency and electric field strength decrease, also increasing the permittivity of dielectric material causes decreasing the resonant frequency and electric field strength. A decrease in resonant frequency and maximum electric field strength, and an increase in resonant bandwidth, were observed with increasing antenna depth. Rounding an antenna of a given depth equals decreasing the depth.

Optimal Tuning of Plant-Friendly PID Controllers

SHI Da-wei, WANG Jun-zheng, MA Li-ling

2010, 19(3): 0331-336.

[Abstract](604)

Abstract:
A plant-friendly proportional-integral-derivative (PID) controller optimization framework is proposed to make tradeoffs among set-point response, controller output variations and robustness. The objective function is chosen as the weighted sum of the integral of squared time-weighted error and the integral of squared time-weighted derivative of the control variable with respect to set-point response, while the robustness of the system is guaranteed by constraints on gain and phase margins. Due to the complex structure of the constraints, the problem is solved by genetic algorithms. Simulation analysis show the proposed method could efficiently reduce the controller output variations while maintaining a short settling time. Based on the simulation results, iterative tuning rules for the weighting factor in the objective function are obtained, which allows efficient simple proportional-integral(PI) tuning formulae to be derived.

Fault-Diagnosis Method Based on Support Vector Machine and Artificial Immune for Batch Process

MA Li-ling, ZHANG Zhao, WANG Jun-zheng

2010, 19(3): 0337-342.

[Abstract](570)

Abstract:
A new fault-diagnosis method to be used in batch processes based on multi-phase regression is presented to overcome the difficulty arising in the processes due to non-uniform sample data in each phase. Support vector machine is first used for phase identification, and for each phase, improved artificial immune network is developed to analyze and recognize fault patterns. A new cell elimination role is proposed to enhance the incremental clustering capability of the immune network. The proposed method has been applied to glutamic acid fermentation, comparison results have indicated that the proposed approach can better classify fault samples and yield higher diagnosis precision.

An Algorithm for Boundary Extraction Based on Turning Row Permutation into Sequence Permutation

FU Meng-yin, ZHANG Xiao-chen, ZHOU Pei-de

2010, 19(3): 0343-347.

[Abstract](659)

Abstract:
Image output by computer is done row by row, the shortcoming of which is that we cannot know the topological relations between points at the image boundary. To obtain the closed boundary of the target from an image and turn points row permutation of boundary into sequence permutation, an algorithm based on 4-connection relation of pixel points is proposed and the analysis of its correctness and complexity is given. Compared with classical operators and existing method, the single pixel boundary extracted from gray images by this algorithm is more complete and more distinct. Moreover, it has a lower time complexity and can eliminate the noise inside and outside the target area. The obtained sequence permutation of points is also conducive to follow-up image processing.

Extending Dynamic Range of Phase Diversity

WANG Xin, ZHAO Da-zun

2010, 19(3): 0348-352.

[Abstract](530)

Abstract:
A method for extending dynamic range of phase diversity (PD) is proposed. The estimating of pupil phase is divided into two steps. Low-order Zernike coefficients of the phase are estimated firstly before all of the Zernike coefficients estimated. The method is based on the assumption that the aberrations of the system are dominated by low order Zernike modes, which is true to most practical situations. The algorithm of Broyden-Fletcher-Goldfarb-Shanno(BFGS) is used in the two steps for optimizing process. Computer simulations are conducted after the theoretical analysis. The result shows that this method can effectively avoid the trap in local minimum during iteration process, and the dynamic range that PD can detect extends from about 2λto about 4λ.

Low-Power Operational Amplifier for Real-Time Signal Processing System of Micro Air Vehicle

WANG Zhu-ping, ZHONG Shun-an, NIE Dan-dan

2010, 19(3): 0353-356.

[Abstract](585)

Abstract:
A low-power complementary metal oxide semiconductor(CMOS) operational amplifier (op-amp) for real-time signal processing of micro air vehicle (MAV) is designed in this paper. Traditional folded cascode architecture with positive channel metal oxide semiconductor(PMOS) differential input transistors and sub-threshold technology are applied under the low supply voltage. Simulation results show that this amplifier has significantly low power, while maintaining almost the same gain, bandwidth and other key performances. The power required is only 0.12mW, which is applicable to low-power and low-voltage real-time signal acquisition and processing system.

Linear Dispersion Orthogonal Space-Time Block Codes

GAO Ming, GE Jian-hua, LI Jing

2010, 19(3): 0357-361.

[Abstract](587)

Abstract:
A new architecture of space-time codes as a combination of orthogonal space-time block codes (OSTBC) and linear dispersion codes (LDC) is proposed in order to improve the bit error rate(BER) performance of OSTBC. The scheme proposed is named linear dispersion orthogonal space-time block codes (LDOSTBC). In LDOSTBC scheme, firstly, the data is coded into LDC codewords. Then, the coded LDC substreams are coded into OSTBC codewords again. The decoding algorithm of LDOSTBC combines linear decoding of OSTBC and ML decoding or suboptimum detection algorithms of LDC. Compared with OSTBC scheme when the rate of LDC isM_tR, the performance of LDOSTBC scheme can be improved without decreasing the data rate, whereM_tis the number of transmit antennas andRis the spectral efficiency of the modulation constellation. If some rate penalty is allowed, when the rate of LDC is less thanM_tRthe performance of LDOSTBC can be improved further.

Parameters Design of Pull-off Deceptive Jamming to Terminal Guidance Radar

LI Yun-jie, ZHANG Yan-bin, GAO Mei-guo

2010, 19(3): 0362-366.

[Abstract](592)

Abstract:
A deceptive pull-off jamming method to terminal guidance radar is put forward in this paper. The design rules about the important jamming parameters are discussed in detail, including the number of the decoy targets in range dimension, the velocity of the range gate pull-off, and the number of the decoy targets in velocity dimension and the velocity of the Doppler frequency pull-off. Also, the steps to design these parameters are brought out. The rules and design procedure discussed in this paper have important meaning for the choice of the reasonable jamming parameters in the practical applications, which can help to obtain good jamming effect.

SiO₂Aerogels Prepared with Ambient Pressure Drying and Its Properties

YANG Kai, PANG Jia-wei, WU Bo-rong, CHEN Shi, WU Feng

2010, 19(3): 0367-370.

[Abstract](480)

Abstract:
SiO₂aerogels were produced from tetraethyl orthosilicate (TEOS) as silicon resources, ethanol as solvent and watery HCl or ammonia by sol-gel method and surface modification at ambient pressure. Scanning electronic microscopy,Fourier transform infrared spectrometer (FT-IR),pore size distribution measurement, packing density and some other experiment methods were used to characterize the morphology and pore structure and other properties of the silica aerogels. The results show that the silica aerogels have a typical nano-porous microstructure with hydrophobic property. It was discovered that SiO₂aerogels have better properties when the preparation condition is as following: the watery HCl concentration is 1%, the aging reagent is CH₃CHOHC₄H₉, the aging time is 20d, the volume concentration of trimethylchlorosilane (TMCS) in hexane is 6% and the surface modification time is 24h.

Study on High Power MH/Ni Battery for Hybrid Electric Vehicles

AN Wei-feng, WU Bo-rong, YANG Kai, LI Han-jun, WU Feng, CHEN Shi, CHEN Feng

2010, 19(3): 0371-374.

[Abstract](587)

Abstract:
Metal hydride-nickel cell is one of the best choices for hybrid electric vehicle for its high specific energy density, security, reliability and renewability. However, its poor capability under high temperature and low specific power restrict its applications. Our studies on the metal hydride-nickel cell with different loading densities show that Ni(OH)₂with CoOOH has good oxidation and reduction properties and proton spread rate when the loading density is 0.617kg/m². The power density and energy density can be as high as 1250W/kg and 49.4W ·h/kg respectively when Ni(OH)₂with CoOOH was used in high power battery with the nickel foam.

Periodic Solutions for a Kind of Second-Order Neutral Differential Equation on Time Scales

ZHANG Li, DU Bo, GE Wei-gao

2010, 19(3): 0375-378.

[Abstract](489)

Abstract:
In this paper, the existence of periodic solutions and nonnegative periodic solutions for a kind of second-order neutral differential equation on time scales is considered. The partial increment is a fixed constant if the time scale is the real number set and is a multiple of the periodic of the time scale if the time scale is not the real number set. By means of a fixed point theorem due to Krasnoselskii, some sufficient conditions are obtained.

2010 Vol. 19, No. 3