JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Linearization and analytic solution of fluid dynamics of cell two-phase flow

FAN Tian-you, FAN Lei, TANG Zhi-yi

2011, 20(1): 1-3.

[Abstract](834) [PDF 229KB](361)

Abstract:
Linearized equations of fluid dynamics of cell two-phase flow for one-dimensional case are proposed. Based on the equations, an analytic solution is derived, in which the frequency of wave is observed. The frequency formula consists of all important parameters of the fluid dynamics. In our observation, the group velocity and phase velocity of the motion of wave propagation are explicitly exhibited as well.

A novel immune genetic algorithm based on quasi secondary response

ZHAO Liang-yu, XU Yong, XU Lai-bin, YANG Shu-xing

2011, 20(1): 4-13.

[Abstract](1001) [PDF 552KB](289)

Abstract:
Combining the advantages of a genetic algorithm and an artificial immune system, a novel genetic algorithm named immune genetic algorithm based on quasi secondary response (IGA-QSR) is proposed. IGA-QSR employs a database to simulate the standard secondary response and the quasi secondary response. Elitist strategy, automatic extinction, clonal propagation, diversity guarantee, and selection based on comprehensive fitness are also used in the process of IGA-QSR. Theoretical analysis, numerical examples of three benchmark mathematical optimization problems and a traveling salesman problem all demonstrate that IGA-QSR is more effective not only on convergence speed but also on convergence probability than a simple genetic algorithm with the elitist strategy (SGA-ES). Besides, IGA-QSR allows the designers to stop and restart the optimization process freely without losing the best results that have already been obtained. These properties make IGA-QSR be a feasible, effective and robust search algorithm for complex engineering problems.

Body area communication based on quasi-electrostatic field and spread spectrum

XIE Yu, HUANG Zhong-hua, CUI Zhan-zhong

2011, 20(1): 14-17.

[Abstract](863) [PDF 318KB](270)

Abstract:
Based on the electrical model of body area communication, the change tendency of channel gain in 100.kHz-10.MHz band was experimentally analyzed and verified. Results show that channel gain was flat and signal attenuation was approximately 43.dB in 1.MHz-10.MHz band. The characteristics of the channel were taken into account in the design of body area spread spectrum communication and its multiuser receiver issue. BER-Eb/No curves of single user and multiuser were derived by simulation. The characteristics of body area commutation channel were studied and the feasibility of introducing spread spectrum theory to body area communication was verified.

Trajectory design and simulation in injection phase for hyper-velocity kinetic energy missile

YU Jian-qiao, MEI Yue-song, HAN Chao

2011, 20(1): 18-22.

[Abstract](877) [PDF 338KB](248)

Abstract:
A movement law of laser beam facula is designed for the injection trajectory of hyper-velocity kinetic energy missile to eliminate the influence of motor exhaust smoke on laser signal transmission. Taking guidance loop of hyper-velocity kinetic energy missile as plant, a closed loop control system with desired step response characteristics is constructed and the movement law of laser beam facula for the missile injection trajectory is designed based on the output signal of the closed loop controller under a step input. Six degree-of-freedom trajectory simulations show that by the guidance of the laser beam facula moving with designed law, the missile can finish transition from the initial trajectory to a stable tracking trajectory without overshoot within the required time.

Electrothermal energy conversion mechanism of micro-scale semiconductor bridge

YANG Gui-li, JIAO Qing-jie, JIN Zhao-xin, XU Xin-chun

2011, 20(1): 23-29.

[Abstract](966) [PDF 548KB](288)

Abstract:
The response characteristics of resistance is observed by the analysis of experimental data of micro-scale semiconductor bridge (MSCB) under different voltage inputs. Two critical voltages are found. One is called exploding voltage, above which the MSCB can be melted and vaporized without generating a plasma, and the other is called producing a plasma voltage, above which the MSCB is entirely vaporized, and then the current flows through the vapor producing the plasma. Based on the non-Fourier heat conduction theory, the electrothermal energy conversion model is established for the stage from heating to exploding, and then the correlation of MSCB and time is obtained by graphic calculation. Importantly, the critical exploding voltage and exploding time are also derivate. With the comparison between the analytical result from the theoretical model and that from experimental data, it has been demonstrated that the theoretical model is reasonable and feasible for designing the exploding voltage and exploding time.

Implementation of VxWorks in autopilot for micro aerial vehicle based on PXA255 and FPGA

WANG Zheng-jie, LI Jie, CHENG Gui-peng, SUN Yin-di

2011, 20(1): 30-35.

[Abstract](1086) [PDF 313KB](252)

Abstract:
The overall hardware construction of autopilot within micro aerial vehicle is presented. The boot process of VxWorks real-time operating system as well as the conception and function of board-support package (BSP) is described. And the transplantation process of the VxWroks operating system into the hardware platform mentioned above is highlighted. It is shown from the final results that VxWorks has high stability and real-time performance, ensuring accurate flight control and a smooth flight of the micro aerial vehicle.

Bridging GPS outages of tightly-coupled GPS/SINS using GMDH neural network

PANG Chen-peng, LIU Zao-zhen

2011, 20(1): 36-41.

[Abstract](803) [PDF 394KB](298)

Abstract:
A tightly-coupled GPS (global positioning system)/SINS (strap-down inertial navigation system) based on a GMDH (group method of data handling) neural network was presented to solve the problem of degraded accuracy for less than four visible GPS satellites with poor signal quality. Positions and velocities of the satellites were predicted by a GMDH neural network, and the pseudo-ranges and pseudo-range rates received by the GPS receiver were simulated to ensure the regular operation of the GPS/SINS Kalman filter during outages. In the mathematical simulation a tightly-coupled navigation system with a proposed approach has better navigation accuracy during GPS outages, and the anti-jamming ability is strengthened for the tightly-coupled navigation system.

Bending behavior of carbon nanotube-reinforced composites

SUN Ling-yu, CUI Li

2011, 20(1): 42-47.

[Abstract](885) [PDF 375KB](281)

Abstract:
The multi-scale modeling method was utilized to study the bending characteristics of a carbon nanotube (CNT) and CNT-reinforced composites. Through combining molecular dynamics and continuum mechanics, the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds. Then, another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix, thus, a multi-scale representative volume element (RVE) model of CNT-reinforced composite was established. Using this RVE model, the bending behavior of CNT-based composites was analyzed. The influence of diameterD, lengthL, aspect ratioL/D, volume fraction, chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the reinforcement effect of flexural modulus of resultant nanocomposites were further discussed. The obtained data provide useful information for the design of CNT-reinforced composites.

Optimization approach hydroforming car beam billets based grey system theory

WU Yao-jin, XUE Yong, DUAN Jiang-nian

2011, 20(1): 48-53.

[Abstract](864) [PDF 540KB](248)

Abstract:
Perfect combination of structural size parameters of the hydroforming billets is essential to obtain even wall-thicknesses of the car-beam. Finite element (FE) analysis on hydroforming car-beam was carried out, and the results were optimized according to multiple quality objectives by the grey system theory. With bending angle, bending radius and hight-difference along the axis direction as variables, orthogonal FE analyses were conducted and the minimum and maximum wall-thicknesses of the billets with different sizes were obtained. Taking the minimum and maximum wall-thicknesses as two references, the correlation coefficient between the data for reference and those for comparison by the grey system theory reduced multi-objectives to a single quality objective, and the average correlation level of every billet facilitated the optimization of size parameters for hydroforming car beam. The trial production showed that the optimization approach satisfied the need of hydroforming car beams.

Numerical study of CNG engine combustion using CFD with detailed chemical kinetics

ZHANG Xin, WANG Yu-jun, XU Jian, HUANG Li

2011, 20(1): 54-59.

[Abstract](718) [PDF 359KB](255)

Abstract:
A three-dimensional model which considers the effects of turbulence and detailed chemical kinetics is built to simulate the combustion process of engine fueled by compressed nature gas (CNG). The model is accomplished by integrating CFD software-KIVA3V and chemical kinetic software-CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and detailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface (MPI). The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that simulation data have a good consistency with experimental results and parallel computing has good efficiency and accelerate ratio.

Modeling the dynamic behavior of a lithium-ion battery for electric vehicles using numerical optimization

HU Xiao-song, SUN Feng-chun, ZOU Yuan

2011, 20(1): 60-64.

[Abstract](881) [PDF 391KB](257)

Abstract:
In order to simulate the dynamical behavior of a lithium-ion traction battery used in electric vehicles, an equivalent circuit-based battery model was established. The methodology in the guide document of the ADVISOR software was used to determine the initial parameters of the model as a function of state of charge (SoC) over an experimental data set of the battery. A numerically nonlinear least squares algorithm in SIMULINK design optimization toolbox was applied to further optimize the model parameters. Validation results showed that the battery model could well describe the dynamic behavior of the lithium-ion battery in two different battery loading situations.

Thermodynamic analysis and combined cycle research on recoverable pressure energy in natural gas pipeline

ZHENG Bin, LIU Jun-de

2011, 20(1): 65-70.

[Abstract](866) [PDF 298KB](215)

Abstract:
Current research and ways of capturing mechanical energy are discussed in this paper. By the aid of the comprehensive thermodynamic analysis and Aspen simulation tool, the amount of available work that can be produced from capturing the pressure energy has been calculated. Based on the comprehensive thermodynamic analysis, two systems have been proposed to capture pressure energy of natural gas to generate electricity. In this study, the expression of exergy is given which can be used in evaluating purposes. A problem with this multidisciplinary study is the complicated boundary condition. In conclusion, a technical prospect on recoverable natural gas pressure energy has been presented based on total energy system theory.

Transient thermo-mechanical coupling simulation of wet brake friction disk on tracked vehicle

LI Jie, WANG Min, WANG Zhi-yong, ZHOU Guang-ming

2011, 20(1): 71-76.

[Abstract](1155) [PDF 504KB](244)

Abstract:
The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat-flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non-uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient thermo-mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the mechanical model of thermo-mechanical coupling can express well the dynamic characteristics of friction disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.

Simulation study on starting of dual clutch transmission for tracked vehicles

ZHANG Jin-le, MA Biao, ZHANG Ying-feng, ZHENG Chang-song

2011, 20(1): 77-83.

[Abstract](761) [PDF 358KB](254)

Abstract:
In order to study the application of dual clutch transmission (DCT) on tracked vehicles, a simulation model and two control methods were performed for starting analysis. Based on a certain transmission of an existing tracked vehicle, a DCT structure was proposed. Matlab/Simulink was adopted as a platform to develop the simulation model. The engine speed was controlled to follow the target speed as a launch strategy. Two control methods, a proportional-integral-derivative (PID) control method and a fuzzy control method, were proposed to control the engine throttle and oil pressure in order to track the target engine speed. Simulation results show that either the PID control or fuzzy control method can improve the starting performance compared with no loop control method. Fuzzy control method can lead a better starting quality compared with PID control method.

Miniaturized multi-band antenna using deformed splot ring resonator

GOU Ming-jiang, YANG Xi, YU Zhi-yuan, TAO Ran, SHI Qing-fan

2011, 20(1): 84-86.

[Abstract](685) [PDF 345KB](262)

Abstract:
A 48.mm×60.mm×1.mm miniaturized multi-band antenna based on deformed split ring resonators was presented. The antenna was consisted of a micro-strip line and a deformed split square ring. Its /S11/ parameters were determined through numerical simulation and experimental measurement within three working bands of 2.6.GHz to 3.0.GHz, 3.9.GHz to 4.4.GHz and 5.2.GHz to 5.8.GHz and the results showed that the parameters within all the bands were less than -10.dB. The gain at every frequency for the antenna was above 2.2.dB and it increased monotonously with the frequency from 5.5.GHz to 7.0.GHz.

Enhanced EM-based channel estimation for MIMO-OFDM in highly mobile channels

CHEN Dong-hua, QIU Hong-bing

2011, 20(1): 87-93.

[Abstract](691) [PDF 360KB](253)

Abstract:
An enhanced expectation-maximization (EM)-based iterative channel estimator for coping with channel time variation is proposed for mobile multiple-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. In the proposed scheme, the recursive least squares (RLS) algorithm is applied to track the time-varying channel impulse response (CIR) within several symbols. By using the tracked time-varying CIR, the ICI are constructed and then cancelled from the received signal, thus reducing their impactions on the channel estimation. Moreover, based on an over-sampled complex exponential basis expansion model (OCE-BEM), an improved channel predictor is derived in order to improve the initial channel estimates accuracy of the iterative estimator. Simulation results show that the proposed scheme outperforms the classic counterpart in time-varying scenarios with a smaller cost of complexity.

Low-complexity MP3 decoder based on Broadcom embedded platform

RAN Chuan, SHEN Ting-zhi

2011, 20(1): 94-99.

[Abstract](1062) [PDF 286KB](275)

Abstract:
A low-complexity MP3 decoder based on Broadcom embedded platform was proposed. C-code level optimization algorithms on inverse quantization, stereo decoding and alias reduction based on PC were proposed to further reduce the amount of memory usage and the computational complexity. Furthermore, the executable file of the optimized MP3 decoder was generated under the Linux environment, and transplanted to the set-top box based on Broadcom embedded platform. Experiment results showed that the total time for decoding was reduced on the embedded platform, and the goal of real time and fluent playing of audio files was fulfilled, which demonstrated the effectiveness of the proposed MP3 decoder. The proposed MP3 decoder could be applied in fields such as the set-top box based on Broadcom embedded platform and other portable devices.

Multichannel noncoherent integration detection using high range resolution profile

LIU Quan-hua, ZENG Da-zhi, LONG Teng

2011, 20(1): 100-104.

[Abstract](911) [PDF 297KB](252)

Abstract:
A multichannel noncoherent integration detection method based on high range resolution profile was presented in this paper. According to the property of the moment-generating function, the distribution characteristics of the noncoherent integrated signals with or without target presence were derived under the circumstance with noncorrelated Gaussian distribution noises. The loss of noncoherent integration was due to improper selection of integration range of cell numbers. A multichannel noncoherent integration detection scheme where the integration number in each channel varies was proposed to solve this problem. The quality of this method for detection of various targets was evaluated. A comparison of fixed integration range cell number detection and multichannel integration detection for a high range resolution profile was presented. Simulation results indicated that the principle of the method was correct and performed well for unknown physical dimension targets. The method required little prior knowledge about target and was convenient for practical implementation.

Adaptive high precision position control of servo actuator with friction compensation using LuGre model

SHAO Zhi-yu, FANG Dong-yang, ZHANG Xiao-dong

2011, 20(1): 105-110.

[Abstract](1015) [PDF 355KB](262)

Abstract:
Adaptive control of servo actuator with nonlinear friction compensation is addressed. LuGre dynamic friction model is adopted to characterize the nonlinear friction and a new kind of sliding-mode observer is designed to estimate the internal immeasurable state of LuGre model. Based on the estimated friction state, adaptive laws are designed to identify the unknown model parameters and the external disturbances, and the system stability and asymptotic trajectory tracking performance are guaranteed by Lyapunov function. The position tracking performance is verified by the experimental results.

Face recognition using illuminant locality preserving projections

LIU Peng-zhang, SHEN Ting-zhi, Kin Man Lam

2011, 20(1): 111-116.

[Abstract](1043) [PDF 473KB](252)

Abstract:
A novel supervised manifold learning method was proposed to realize high-accuracy face recognition under varying illuminant conditions. The proposed method, named illuminant locality preserving projections (ILPP), exploited illuminant directions to alleviate the effect of illumination variations on face recognition. The face images were first projected into low-dimensional subspace. Then the ILPP translated the face images along specific direction to reduce lighting variations in the face. The ILPP reduced the distance between face images of the same class, while increase the distance between face images of different classes. This proposed method was derived from the locality preserving projections (LPP) methods, and was designed to handle face images with various illuminations. It preserved the face image’s local structure in low-dimensional subspace. The ILPP method was compared with LPP and discriminant locality preserving projections (DLPP), based on the YaleB face database. Experimental results showed the effectiveness of the proposed algorithm on the face recognition with various illuminations.

Novel assay for identification of semicarbazide-sensitive amine oxidase by a priority-based strategy in mass spectrometry

ZHANG Yong-qian, WANG Hong-bin, WANG Lu, HU Gao-fei, ZHU Yong, DENG Yu-lin

2011, 20(1): 117-122.

[Abstract](1182) [PDF 469KB](246)

Abstract:
A novel assay for the identification of semicarbazide-sensitive amine oxidase in human umbilical artery tissue by a priority-based strategy in the mass spectrometry was developed. The protein extract was separated by SDS-PAGE,and then an entire band at 96.KDa was excised and digested by trypsin. The digested peptides were separated by capillary C₁₈analytical column and detected by ESI-MS-MS. In the direct data-dependent method (also called traditional method), the semicarbazide-sensitive amine oxidase (SSAO) cannot be identified by LC-ESI-MS-MS. Compared with the traditional method, our assay by a priority-based strategy in the mass spectrometry can successfully identify the target protein-SSAO in the complex biological sample. As 60. μ g, 120. μ g, 240. μ g of total protein extract were loaded on the SDS-PAGE, the Mascot result showed that SSAO score was 46, 86 and 137, the sequence coverage was 2.%, 5.% and 10.%, and the peptide count was 2, 6 and 10, respectively.The MS/MS spectra of two unique peptides of SSAO were confirmed by manual identification. The band at 96 KDa included SSAO was validated by the Western blot. The assay significantly improved the score and coverage of target protein and enhanced the identification of reliability and the confidence.

Thermal comfort in offices: comfort values and optimization of indoor control variables

XU Wei, CHEN Xiang-guang, ZHAO Jun, HU He

2011, 20(1): 123-128.

[Abstract](757) [PDF 325KB](242)

Abstract:
In order to search for reasonable air-conditioned indoor control variables and save energy consumption and meet to need of personal thermal comfort, a method which is based on numerical simulation is employed to optimize indoor control variables. Computational fluid dynamics (CFD) is used to describe thermal state of office. An optimal method is proposed in this paper, dual neural network model is firstly used to acquire reliable information, data from CFD model are pre-processed, and the remaining data are used to train artificial neural networks (ANN), then CFD model is replaced by ANN model to reduce computational cost when is optimized, indoor control variables are optimized by genetic algorithm. Simulation results show that indoor thermal comfort is improved obviously, and the energy cost is decreased accordingly.

Numerical study on mixing performance of screw elements in intermeshing counter-rotating and co-rotating twin-screw extrudes

CHEN Jin-nan, DAI Pan

2011, 20(1): 129-137.

[Abstract](584) [PDF 753KB](258)

Abstract:
The flow process of unplasticized polyvinyl chloride (U-PVC) through the mixing zone of intermeshing counter-rotating and co-rotating twin-screw extruders (TSEs) were numerically simulated by the finite element method. Three-dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing performance was characterized by the resident time distribution. The results indicate that the counter-rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co-rotating TSE has better performance in dispersive and distributive mixing.

Real-time control of aerobic/anoxic digestion for waste activated sludge

ZHANG Yan-ping, PENG Yong-zhen, WANG Shu-ying, WANG Ping

2011, 20(1): 138-142.

[Abstract](874) [PDF 371KB](248)

Abstract:
Experiments were conducted to study the performance characters of aerobic/anoxic (A/A) digestion of sludge at 30±1.℃, while the sludge retention time (SRT) was kept 16.d. The variations of oxidation reduction potential (E_h) and pH were continuously monitored during the A/A digestion and the conversions of ammonium and nitrate were investigated. Important features on bothE_hand pH profiles were identified to develop process control strategy. Since the feature point onE_hprofile where d²E_h/dt²0 is very stable during anoxic cycle, it can be used to determine the end of denitrification. The end of nitrification can be identified according to dpH/dt0. A real-time control strategy of A/A digestion of sludge was developed and tested with pH andE_has control parameters. It is shown that the performance of the real-time control strategy is better than that of a fixed-time control strategy. While the real-time controlled A/A digestion system can achieve a similar volatile suspended solids (VSS) destruction efficiency of 35.2.% as a continuously aerated system, it improves the supernatant quality in a shorter aeration time(7.75.d for a 20.d period).

2011 Vol. 20, No. 1