JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Experimental Investigation on Spall Fracture of 30CrMnSiNi2A Steel

WU Hai-jun, YAO Wei, HUANG Feng-lei, ZHANG Lian-sheng

2010, 19(1): 1-7.

[Abstract](677)

Abstract:
Spall fracture is a damage that occurs in a body when two rarefaction waves interact and produce enough dynamic tension breakage, and then the spall zone is founded in the interior of the target. Behavior of materials in the spall phenomenon is strongly affected by the stress level, time of loading and so on. The spall properties of 30CrMnSiNi2A steel loaded by a gas gun were investigated using the planar impact experiment and the two-wave structural profiles of free surface velocities of specimens were recorded by velocity interferometer system for any reflector (VISAR) techniques. The Hugoniot elastic limit (HEL), spall strength, spall thickness and strain rate were obtained in the plate impact experiments of 30CrMnSiNi2A steel specimens with different thickness. The result indicates that the values of HEL and spall strength increase with the increasing strain rate. The dynamic spall fracture and corresponding microscopic mechanism of 30CrMnSiNi2A at different strain rates were evaluated through the fracture analysis and fractography using a scanning electron microscope (SEM).

Theoretical Model for Calculating Electric-Power Curves Depicting Accelerated Flyer by Exploding Foil

ZHAO Yan, ZENG Qing-xuan, FENG Chang-gen

2010, 19(1): 8-13.

[Abstract](8920)

Abstract:
A theoretical model for calculating electric-power curves of small-size foil during its electrical explosion is given. This technique is based on temperature dependence of foil conductivity. After taking into account the energy conversion of the foil explosion, the power-time curve is applied to the hydrodynamic code. One-dimensional numerical simulations of electric-explosion driving flyers are performed using this code. Calculated flyer velocities lie within ±8% of experimental data from Lawrence Livermore National Laboratory (LLNL), and simulated history curves of flyer velocities coincide well with those measured using velocity interferometer system for any reflector (VISAR), indicating a helpful work for design optimization of slapper detonators.

Qualitative Knowledge Based Discrete Rod Model with Simulation Case

ZHOU Hai-ying, DONG Su-rong, LI Long-jun

2010, 19(1): 14-18.

[Abstract](1322)

Abstract:
Constructing a qualitative model for discrete rods warhead, the kinematics analysis and dynamics analysis of the rods are completed. On the basis of the qualitative model of discrete rods, a simulation case is provided. The qualitative simulation result shows that hexagon cross section shape of rod will receive the lowest air drag while by means of better preplaced dip angle, controlling the rotation velocity of the rod and keeping every rod with identical dip angle to the axis of warhead will make the rod get a lateral direction velocity so as to have the rod gain identical casting initial velocity in its length direction. Simulation experiment shows that when dip angle of preplaced discrete rod is 6°, the damage cycle reaches the optimal value.

Numerical Study on Aerodynamic Characteristics of Ducted Fan Aircraft

FAN Ning-jun, XU Jia, YANG Ji-wei

2010, 19(1): 19-24.

[Abstract](517)

Abstract:
Based on investigations into the flow field of ducted fan aircrafts, structural parameters of duct are quantified. A three-dimensional model is established for numerical simulation, and adaptive Cartesian grid is used to mesh the model in order to improve calculation speed and solution accuracy. Three-dimensional Navier-Stokes equations are brought in to analyze different duct styles. Generalization of simulation results leads to several conclusions in duct aerodynamics to help design ducted fan aircrafts.

Tensioner Vibration and Belt Slipping Behavior Investigation for Damped Serpentine Belt Drive Systems

WANG Hong-yun, SHANGGUAN Wen-bin

2010, 19(1): 25-30.

[Abstract](459)

Abstract:
A nonlinear rotational motion model forn-pulley damped serpentine belt drive systems (SBDSs) was developed. The effects of the belt deflection along the contact arc of pulleys on the belt span tensions were considered. The methods for calculating the tensioner arm vibration and belt slipping on pulleys were introduced. The effects of belt damping on rotational vibration of tensioner arm and belt slipping on pulleys were studied. Numerical solutions for a 3-pulley SBDS indicate that the belt slipping at the steady states should be controlled to avoid belt slipping at transient states. The slip factors tend to decrease when the belt damping increases, and the possibility of the belt slipping can be controlled through adjusting the wrap angles of pulleys and the preload of the tensioner when the design parameters of SBDS remain constant.

Regulated and Speciated Hydrocarbon Emissions from a Dual Fuel Light Duty Vehicle with and Without a Three-Way Catalyst

DING Yan, GE Yun-shan, WANG Jun-fang, TAN Jian-wei, YOU Ke-wei

2010, 19(1): 31-36.

[Abstract](5732)

Abstract:
The regulated pollutants (CO, HC and NO_x) and unregulated pollutants (volatile organic compounds and carbonyl compounds) , emitted from a dual fuel vehicle fueled with gasoline and E10 fuel, are measured under a transient cycle and steady modes. The impacts of a three-way catalyst (TWC) are investigated for the two types of fuels. The measured results show that NO_xand acetaldehyde emitted from the E10-fueled car are much more than that from the gasoline-fueled car under the same modes. On the basis of maximum incremental reactivity (MIR) factors and emissions of organic gases, the ozone specific reactivity of the tailpipe gases are evaluated.

Research on the Control Strategy of Variable Nozzle Turbocharger for Natural Gas Engine

HAO Li-jun, HUANG Ying, ZHUANG Fu-jun, GE Yun-shan

2010, 19(1): 37-41.

[Abstract](702)

Abstract:
A variable nozzle turbocharger (VNT) was applied to a 2.2-liter L4 natural gas engine, and a VNT control system was designed to operate it. Based on VNT matching test results, a VNT control strategy was studied, in which VNT adjustment is carried out through pre-calibrated VNT handling rod position, combined with a closed-loop target boost pressure feedback using proportional-integral-derivative(PID) algorithm. Experimental results showed that the VNT control system presented in this thesis can lead to optimized performance of VNT, increase engine volumetric efficiency over a wide speed range, improve engine dynamic characteristics and upgrade economic performance.

Study on Control of Pneumatic Selecting and Shifting Actuators Using Rapid Control Prototyping

XIONG Guang-ming, GUO Li-li, ZHOU Sheng-yan, XI Jun-qiang, DONG Yi-liang, LI Hong-jun

2010, 19(1): 42-46.

[Abstract](653)

Abstract:
A gearbox in-the-loop control platform using dSPACE real-time system is designed for the study on the control technology of pneumatic selecting and shifting actuators based on rapid control prototyping. The operational principle of such actuators was analyzed using dSPACE hardware and software, resulting in a better knowledge of the logical relationship among solenoid valves, gear positions of cylinders and system input／output. Based on these, a control model was developed under the Matlab／Simulink environment and rapidly improved to meet requirements through experiments. Relevant tests have shown that analysis efficiency on selecting and shifting actuators could be raised and development of control strategy facilitated.

Development of AMT Fault Diagnosis Technique Based on KWP2000

HUANG Hua, XI Jun-qiang, XIAO Kuan, YANG Deng-hua

2010, 19(1): 47-52.

[Abstract](530)

Abstract:
In order to make automatic mechanical transmission (AMT) capable of performing fault self-diagnoses and adaptive to standard communication interface, through technical analysis and intensive study concerning on-board diagnostic protocols now widely applied in Europe and America, KWP2000 on CAN is accepted as a technological path. An AMT fault communication system using hardware-in-the-loop simulation by dSPACE is developed, and communications compatible with ISO 15031-6 is realized on this module. Moreover, a hand-held fault diagnosis instrument with built-in software is designed to facilitate communications with AMT fault communication module with accuracy, rapidity and stableness. Bench and real vehicle experimental results show that the developed instrument and module can perform the anticipated functions, so as to maintain steady communications under the KWP2000-on-CAN protocol.

Vehicle Dynamics Modeling and Simulation for ACC

LI Jing-liang, LIU Zhao-du, LI Zhi-yuan

2010, 19(1): 53-57.

[Abstract](526)

Abstract:
A 7 degree-of-freedom (DOF) 4 wheels vehicle dynamics model based on Matlab-Simulink is established, and 7 DOF vehicle dynamics equations in the form of nonlinear state-space standards are given. The characters of the electronic throttle and the active braking system have been analyzed. And the electronic throttle model and the active braking system model are built according to the test results respectively. Off-line simulation results indicate that the model is suitable for the vehicle adaptive cruise control system, and both of the electronic throttle and the active braking system work in a reasonable way. An adaptive cruise control (ACC) example illustrates that the model has a good performance in cruise and distance keeping.

New Synchronization Algorithm and Analysis of Its Convergence Rate for Clock Oscillators in Dynamical Network with Time-Delays

GAN Ming-gang, YU Miao, CHEN Jie, DOU Li-hua

2010, 19(1): 58-65.

[Abstract](5930)

Abstract:
New synchronization algorithm and analysis of its convergence rate for clock oscillators in dynamical network with time-delays are presented. A network of nodes equipped with hardware clock oscillators with bounded drift is considered. Firstly, a dynamic synchronization algorithm based on consensus control strategy, namely fast averaging synchronization algorithm (FASA), is presented to find the solutions to the synchronization problem. By FASA, each node computes the logical clock value based on its value of hardware clock and message exchange. The goal is to synchronize all the nodes logical clocks as closely as possible. Secondly, the convergence rate of FASA is analyzed that proves it is related to the bound by a nondecreasing function of the uncertainty in message delay and network parameters. Then, FASAs convergence rate is proven by means of the robust optimal design. Meanwhile, several practical applications for FASA, especially the application to inverse global positioning system (IGPS) base station network are discussed. Finally, numerical simulation results demonstrate the correctness and efficiency of the proposed FASA. Compared FASA with traditional clock synchronization algorithms (CSAs), the convergence rate of the proposed algorithm converges faster than that of the CSAs evidently.

Infinity Norm Measurement of Sensitivity for Closed-Loop Systems Using Chirp as Excitation

SHI Da-wei, WANG Jun-zheng

2010, 19(1): 66-70.

[Abstract](587)

Abstract:
A simple identification method based on a closed-loop experiment is proposed to measure the infinity norm of sensitivity function. A chirp signal, modified to have desired band-limited characteristic and finite duration, is used as the excitation in the experiment, and the sensitivity function is calculated using Fourier transform of input and error signals before the infinity norm is evaluated through maximization of the magnitude of sensitivity function. With an additional feature of providing values of gain margin and phase margin at a little extra effort, this method can be used in the identification step of a controller auto-tuning procedure, as having been supported by simulation results showing its capability of providing fast and accurate estimates for a large variety of processes.

New Algorithm for Binary Connected-Component Labeling Based on Run-Length Encoding and Union-Find Sets

WANG Hong-tao, LUO Chang-zhou, WANG Yu, GUO He, ZHAO Shu-fang

2010, 19(1): 71-75.

[Abstract](490)

Abstract:
Based on detailed analysis of advantages and disadvantages of the existing connected-component labeling (CCL) algorithm, a new algorithm for binary connected components labeling based on run-length encoding (RLE) and union-find sets has been put forward. The new algorithm uses RLE as the basic processing unit, converts the label merging of connected RLE into sets grouping in accordance with equivalence relation, and uses the union-find sets which is the realization method of sets grouping to solve the label merging of connected RLE. And the label merging procedure has been optimized: the union operation has been modified by adding the "weighted rule" to avoid getting a degenerated-tree, and the "path compression" has been adopted when implementing the find operation, then the time complexity of label merging isO(nα(n)). The experiments show that the new algorithm can label the connected components of any shapes very quickly and exactly, save more memory, and facilitate the subsequent image analysis.

Non-Intrusive Objective Speech Quality Measurement Based on Fuzzy GMM and SVR for Narrowband Speech

WANG Jing, ZHANG Ying, ZHAO Sheng-hui, KUANG Jing-ming

2010, 19(1): 76-81.

[Abstract](578)

Abstract:
Based on fuzzy Gaussian mixture model (FGMM) and support vector regression (SVR), an improved version of non-intrusive objective measurement for assessing quality of output speech without inputting clean speech is proposed for narrowband speech. Its perceptual linear predictive (PLP) features extracted from clean speech and clustered by FGMM are used as an artificial reference model. Input speech is separated into three classes, for each a consistency parameter between each feature pair from test speech signals and its counterpart in the pre-trained FGMM reference model is calculated and mapped to an objective speech quality score using SVR method. The correlation degree between subjective mean opinion score (MOS) and objective MOS is analyzed. Experimental results show that the proposed method offers an effective technique and can give better performances than the ITU-T P.563 method under most of the test conditions for narrowband speech.

Effect of Annealing Process on Microstructure and Mechanical Properties of Ultrafine Copper Prepared by Spark Plasma Sintering

ZHANG Zhao-hui, ZAHNG Chun, WANG Fu-chi, LI Shu-kui

2010, 19(1): 82-86.

[Abstract](404)

Abstract:
The spark plasma sintering (SPS) method is used to prepare the ultrafine copper with the average grain size less than 10μm and the tensile strength greater than 280MPa. The ultrafine copper is annealed at different temperatures for 60min, and the annealing microstructure is observed and the hardness and the deformation behavior of the bulk copper are tested. The results indicate that the grains grow very slowly when the annealing temperature is less than 450℃. However, the grain growth becomes remarkable when the annealing temperature exceeds 450℃. And the plasticity of the bulk copper is the best when the annealing temperature of 450℃ is adopted. After stamping and spin forming, the deformed copper is recrystallized completely and the grain is refined when the copper is annealed at 500℃ for 30min.

Method of Predicting Water Content in Crude Oil Based on Measuring Range Automatic Switching

CHEN Xiang-guang, ZHU Wen-bo, ZHAO Jun, REN Lei

2010, 19(1): 87-91.

[Abstract](422)

Abstract:
Water content in output crude oil is hard to measure precisely because of wide range of dielectric coefficient of crude oil caused by injected dehydrating and demulsifying agents. The method to reduce measurement error of water content in crude oil proposed in this paper is based on switching measuring ranges of on-line water content analyzer automatically. Measuring precision on data collected from oil field and analyzed by in-field operators can be impressively improved by using back propogation (BP) neural network to predict water content in output crude oil. Application results show that the difficulty in accurately measuring water-oil content ratio can be solved effectively through this combination of on-line measuring range automatic switching and real time prediction, as this method has been tested repeatedly on-site in oil fields with satisfactory prediction results.

New Method for Multivariate Statistical Process Monitoring

PEI Xu-dong, CHEN Xiang-guang, LIU Chun-tao

2010, 19(1): 92-98.

[Abstract](489)

Abstract:
A new method using discriminant analysis and control charts is proposed for monitoring multivariate process operations more reliably. Fisher discriminant analysis (FDA) is used to derive a feature discriminant direction (FDD) between each normal and fault operations, and each FDD thus decided constructs the feature space of each fault operation. Individuals control charts (XmR charts) are used to monitor multivariate processes using the process data projected onto feature spaces. Upper control limit (UCL) and lower control limit (LCL) on each feature space from normal process operation are calculated for XmR charts, and are used to distinguish fault from normal. A variation trend on an XmR chart reveals the type of relevant fault operation. Applications to Tennessee Eastman simulation processes show that this proposed method can result in better monitoring performance than principal component analysis (PCA)-based methods and can better identify step type faults on XmR charts.

Study of High-Temperature Stability of Pyrochlore Zirconates

FAN Qun-bo, WANG Fu-chi, ZHANG Hui-ling

2010, 19(1): 99-102.

[Abstract](552)

Abstract:
Based on defect chemistry theory and molecular dynamics, the defect formation energy and its relationship with the mechanism of pyrochlore-fluorite phase change were investigated, so as to reveal the underlying mechanism of high-temperature stability of pyrochlore zirconates. Results showed that with the rise of the atom mass of A, the defect formation energies decreased that meant the crystal structure tended to become more disordered. Noticeably, the first nearest cation antisite dominated the pyrochlore disorder transformation process. In addition, it was found that the diffusion of oxygen atoms was far higher than that of cations, and was increased with the temperature, thus also promoting the pyrochlore-fluorite transformation process.

Protective Effects of Qingshen Compound on Experimental Masugi Nephritis Model in Rats

LI Yan, XIN Nian

2010, 19(1): 103-108.

[Abstract](599)

Abstract:
To study protective effects of Qingshen Compound on experimental anti-glomerular basement membrane antibody (AGBM-Ab) nephritis model in rats, an experimental Masugi nephritis model was established in Sprague-Dawley(SD) rats by a single-dose injection of prepared rabbit anti-rat glomerular basement membrane(GBM) serum into sublingual vein and then effects of Qingshen Compound on urine volume, urinary protein level, blood urea nitrogen (BUN), creatinine (Cr), albumin (Alb), triglycerides (TG), cholesterol (CHO) and histopathological changes were investigated. After successive daily three-dosage oral administration to rat groups (9.4, 4.7, 2.3g ·kg^-1) for 8 weeks, Qingshen Compound was proved effective on increasing urine volume and Alb content, and decreasing levels of urinary protein, BUN, Cr and TG. Furthermore, high and middle dosages (9.4, 4.7g ·kg^-1) could improve histopathological healing of the model. In summary, Qingshen Compound has shown protective effects on experimental Masugi nephritis model in rats.

Supplier Evaluation Model Based on Fuzzy Measures and Choquet Integral

WU Jian-zhang, ZHANG Qiang, SANG Sheng-ju

2010, 19(1): 109-114.

[Abstract](589)

Abstract:
To identify interactions among evaluation criteria and describe their importance, a new identification method making use of a fuzzy measure is presented. The relative weight and interaction degree of every evaluation criteria pair are obtained by using the diamond pairwise comparison method. Based on comparison results, the maximum eigenvector method of analytic hierarchy process (AHP), the hierarchical clustering method, and the phi(s) transformation are utilized to generate values of the fuzzy measure for each subset of the evaluation criterion set. Overall evaluation on each supplier is aggregated by Choquet integral with respect to the fuzzy measure. Finally, an illustrative example demonstrates the practical feasibility and validity of the proposed method.

Return Contract of Supply Chain with Fuzzy Continuous Demand

SANG Sheng-ju, ZHANG Qiang, WU Jian-zhang

2010, 19(1): 115-120.

[Abstract](541)

Abstract:
In a two-stage supply chain composed of one supplier and one retailer, the supply chain coordination mechanism in a fuzzy continuous demand environment is researched. A positive triangular fuzzy number is used to model the external market demand. Using the method of fuzzy cut sets theory, both fuzzy decentralized and centralized decision-making processes are analyzed, and another model of fuzzy return contract is proposed to help coordinate such supply chain. It is shown that in fuzzy environment there exists a unique solution of the retailers optimal order quantity, the double marginalization problem can be solved by providing different tactics for wholesale pricing and return pricing, and the fuzzy expected profit of each actor can be expected to improve in the return contract. Finally, a numerical example is given to illustrate the models and the solution-seeking process.

Simulation Methods of Stochastic Volatility Interest Rate Term Structure

RAN Lun, ZHOU Li, CHEN Qian

2010, 19(1): 121-126.

[Abstract](697)

Abstract:
A term structure model bearing features of stochastic volatility and stochastic mean drift with jump (SVJ-SD model for short) is built in the paper to describe the stochastic behavior of interest rates. Based on sample data of an interest rate of national bond repurchase, maximum likelihood (ML), linear Kalman filter and efficient method of moments (EMM) are used to estimate the model. While ML works well for simple models, it may lead to considerable deviation in parameter estimation when dynamic risks of interest rates are considered in them. Linear Kalman filter is a tractable and reasonably accurate technique for estimation cases where ML was not feasible. Moreover, when compared with the first two approaches, using EMM can obtain better parameter estimates for complex models with non-affine structures.

2010 Vol. 19, No. 1