Welcome to Journal of Beijing Institute of Technology

2017 Vol. 26, No. 4

Engineering Mechanics
Viscoplastic Damage-Softening Constitutive Model for Concrete Subjected to Uniaxial Dynamic Compression
Xiaowang Sun, Yongchi Li, Ruiyuan Huang, Zhongbao Ye, Kai Zhao
2017, 26(4): 427-433. doi:10.15918/j.jbit1004-0579.201726.0401
Abstract:
A new viscoplastic damage-softening constitutive model is presented. It is developed by integrating a Bodner-Partom viscoplastic model with a new damage evolution equation. A set of ordinary differential equations (ODEs) is formulated, and a Runge-Kutta integral method is used to get stress-strain curves given by the model. Also, stress-strain curves of a wide range of strain-rates for concrete were obtained by split Hopkinson pressure bar (SHPB) tests. By fitting the integral stress-strain curves to the experimental ones with the least square optimization method, we determined the material parameters in our model. Some properties of the new model, such as strain-rate sensitivity, damage evolution characteristics, strain-rate jump effects and unloading feature, are explored. These results show that our new model can describe dynamic behaviors of concrete very well, and our integrating-fitting-optimizing method to get material parameters is valid.
Compressive Mechanical Properties of Normalized 10#Low Carbon Steel
Jifeng Wei, Xin Xie, Ziyan Jin, Wulong Fan, Jifeng Zhang
2017, 26(4): 434-439. doi:10.15918/j.jbit1004-0579.201726.0402
Abstract:
Compressive mechanical properties of 10#low carbon steel with normalizing heat treatment are studied. A Gleeble system is adopted to analyze the quasi-static properties and thermal softening effects of heat treated 10#steel, while a Hopkinson bar apparatus is used to investigate its dynamic characteristics under different strain rates. The results show that yield stress of heat treated 10#steel is more than that of untreated one at room temperature. When the specimens are tested at different temperatures, yield stresses decrease with increasing temperature except 573 K. Moreover, the influence of strain rate on yield stress are verified, which shows that the yield stress increases sharply from 500 s-1to 1 890 s-1, while it changes a little from 1 890 s-1to 4 850 s-1. The results indicate that yield stress is mainly influenced by hardening effect at low strain rate and controlled by both thermal softening effect and strain rate hardening effect at high strain rate.
Mechanical Engineering
Vibration-Based Terrain Classification for Autonomous Vehicles
Kai Zhao, Mingming Dong, Zhiguo Wang, Yanxi Han, Liang Gu
2017, 26(4): 440-448. doi:10.15918/j.jbit1004-0579.201726.0403
Abstract:
A method for terrain classification based on vibration response resulted from wheel-terrain interaction is presented. Four types of terrains including sine, gravel, cement and pebble were tested. The vibration data were collected by two single axis accelerometers and a triaxial seat pad accelerometer, and five data sources were utilized. The feature vectors were obtained by combining features extracted from amplitude domain, frequency domain, and time-frequency domain. The ReliefF algorithm was used to evaluate the importance of attributes; accordingly, the optimal feature subsets were selected. Further, the predicted class was determined by fusion of outputs provided by five data sources. Finally, a voting algorithm, wherein a class with the most frequent occurrence is the predicted class, was employed. In addition, four different classifiers, namely support vector machine,k-nearest neighbors, Naïve Bayes, and decision tree, were used to perform the classification and to test the proposed method. The results have shown that performances of all classifiers are improved. Therefore, the proposed method is proved to be effective.
Vehicle Active Damping Control with Considering Time Delay
Danna Jiang, Ying Huang, Donghao Hao
2017, 26(4): 449-457. doi:10.15918/j.jbit1004-0579.201726.0404
Abstract:
A model predictive control (MPC) based active damping controller for automotive driveline oscillations with time-delay consideration is proposed. A simplified driveline model considering time delay is modeled and converted to a linear parameter varying state space equation. Based on the model and model predictive control theory, an active damping controller is designed for drivability and comfortability improvement. In order to verify the designed controller, a driveline with engine is modeled to simulate the tip-in/out driving operation. An MPC active damping controller without considering time delay is simulated together with the proposed controller. The simulation results show that, by adopting the new MPC active damping controller, the vibration of the vehicle is reduced and the drivability and comfortability are improved.
Structure Optimization and Performance Analysis of a Multiple Radial Magnetorheological Valve
Guoliang Hu, Fang Zhong, Haiyun Zhang, Ruqi Ding
2017, 26(4): 458-467. doi:10.15918/j.jbit1004-0579.201726.0405
Abstract:
Due to the controllable and reversible properties of the smart magnetorheological (MR) fluid, a novel multiple radial MR valve was developed. The fluid flow channels of the proposed MR valve were mainly composed of two annular fluid flow channels, four radial fluid flow channels and three centric pipe fluid flow channels. The working principle of the multiple radial MR valve was introduced in detail, and the structure optimization design was carried out using ANSYS software to obtain the optimal structure parameters. Moreover, the optimized MR valve was compared with pre-optimized MR valve in terms of their magnetic flux density of radial fluid resistance gap and performance of pressure drop. The experimental test rig was set up to investigate the performance of pressure drop of the proposed MR valve under different currents applied and different loading cases. The results show that the pressure drop between the inlet and outlet port could reach 5.77 MPa at the applied current of 0.8 A. Furthermore, the experimental results also indicate that the loading cases had no effect on the performance of pressure drop.
Design and Analysis of a Horizontal Quasi-Zero Stiffness Vibration Isolator by Combining Rolling-Ball and Disk Springs in Parallel
Gaofeng Guan, Dengfeng Xu, Yu Zhu, Qiang Li, Qiang Yu
2017, 26(4): 468-476. doi:10.15918/j.jbit1004-0579.201726.0406
Abstract:
Combining disk springs having negative stiffness with a rolling-ball in parallel is proposed in this paper. It is used to reduce the system stiffness and the positioning error in a non-ideal environment. The characteristics of a disk spring are analyzed. The dynamic equation of its motion has been obtained based on Newton's second law. After definition of a error margin, the dynamic equation of the motion can be treated as a Duffing oscillator, and the influences of non-dimensional parameters on the stiffness and transmissibility are studied. The natural frequency and transmissibility are achieved in a linearization range, where the ratio of linear to nonlinear items is small enough. The influence of mass ratio and non-dimensional parameters on natural frequency are analyzed. Finally, a comparison of numerical example demonstrates that the QZS system can realize a lower stiffness within an increased range.
Informatics and Electronic Engineering
Wideband Polarization Reconfigurable Dielectric Resonator Antenna
Bin Li, Ying Zhou, Mengda Wu, Yuxuan Xia, Yong Liu, Xin Lyu
2017, 26(4): 477-483. doi:10.15918/j.jbit1004-0579.201726.0407
Abstract:
A wideband polarization reconfigurable dielectric resonator antenna excited by quasi-lumped quadrature coupler (QLQC) is proposed. By adjusting the value of varactor diode on the QLQC feed network, both the wideband LP and CP dielectric resonator antennas (DRA) modes can be achieved. By selecting a different feed port, left-and right-handed CP conversion can be realized. It is found that the 10 dB impedance bandwidth of the LP and CP modes are 10.1% and 44.9%, respectively. For the CP mode, a very wide 3 dB axial ratio bandwidth of 37.7% can be obtained which is much larger than that of the microstrip patch counterpart (3.8%). It is worth mentioning that the wideband CP DRA has a stable broadside radiation pattern across the whole operating band where the boresight gain is larger than 3 dBi.
Scattering Center Modeling Using Adaptive Segmental Compressive Sampling
Qifeng Li, Kunyi Guo, Jiaxin Wang, Xinqing Sheng, Tianshu Liu
2017, 26(4): 484-493. doi:10.15918/j.jbit1004-0579.201726.0408
Abstract:
In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation (TFR) with aspect undersampling, an approach using adaptive segmental compressive sampling according to the aspect dependencies of the scattering centers is proposed. The random noise problem induced by compressive sampling is solved by employing a series of signal processing techniques of filtering, image transformation and Hough Transform. Three examples are presented to verify the effectiveness of this approach. The comparisons between the built models and the precise scattered fields computed by a well-validated full-wave numerical method are investigated, and the results show good agreements between each other.
Design and Implementation of Memory Access Fast Switching Structure in Cluster-Based Reconfigurable Array Processor
Rui Shan, Lin Jiang, Junyong Deng, Xueting Li, Xubang Shen
2017, 26(4): 494-504. doi:10.15918/j.jbit1004-0579.201726.0409
Abstract:
Memory access fast switching structures in cluster are studied, and three kinds of fast switching structures (FS, LR2SS, and LAPS) are proposed. A mixed simulation test bench is constructed and used for statistic of data access delay among these three structures in various cases. Finally these structures are realized on Xilinx FPGA development board and DCT, FFT, SAD, IME, FME, and de-blocking filtering algorithms are mapped onto the structures. Compared with available architectures, our proposed structures have lower data access delay and lower area.
Microblog Summarization via Enriching Contextual Features Based on Sentence-Level Semantic Analysis
Senlin Luo, Qianrou Chen, Jia Guo, Ji Zhang, Limin Pan
2017, 26(4): 505-516. doi:10.15918/j.jbit1004-0579.201726.0410
Abstract:
A novel microblog summarization approach via enriching contextual features on sentence-level semantic analysis is proposed in this paper. At first, a Chinese sentential semantic model (CSM) is employed to analyze the semantic structure of each microblog sentence. Then,a combination of sentence-level semantic analysis and latent dirichlet allocation is utilized to acquire extra features and related words to enrich the collection of microblog messages. The simlilarites between the two sentences are calculated based on the enriched features. Finally, the semantic weight and relation weight are calculated to select the most informative sentences, which form the final summary for microblog messages.Experimental results demonstrate the advantages of our proposed approach. The results indicate that introducing sentence-level semantic analysis for context enrichment can better represent sentential semantic.The proposed criteria,namely, semantic weight and relation weight enhance summary result. Furthermore, CSM is a useful framework for sentence-level semantic analysis.
Feature Selection with Fluid Mechanics Inspired Particle Swarm Optimization for Microarray Data
Shengsheng Wang, Ruyi Dong
2017, 26(4): 517-524. doi:10.15918/j.jbit1004-0579.201726.0411
Abstract:
Deoxyribonucleic acid (DNA) microarray gene expression data has been widely utilized in the field of functional genomics, since it is helpful to study cancer, cells, tissues, organisms etc. But the sample sizes are relatively small compared to the number of genes, so feature selection is very necessary to reduce complexity and increase the classification accuracy of samples. In this paper, a completely new improvement over particle swarm optimization (PSO) based on fluid mechanics is proposed for the feature selection. This new improvement simulates the spontaneous process of the air from high pressure to low pressure, therefore it allows for a search through all possible solution spaces and prevents particles from getting trapped in a local optimum. The experiment shows that, this new improved algorithm had an elaborate feature simplification which achieved a very precise and significant accuracy in the classification of 8 among the 11 datasets, and it is much better in comparison with other methods for feature selection.
Cooperative Multi-Agent Reinforcement Learning with Constraint-Reduced DCOP
Yi Xie, Zhongyi Liu, Zhao Liu, Yijun Gu
2017, 26(4): 525-533. doi:10.15918/j.jbit1004-0579.201726.0412
Abstract:
Cooperative multi-agent reinforcement learning (MARL) is an important topic in the field of artificial intelligence, in which distributed constraint optimization (DCOP) algorithms have been widely used to coordinate the actions of multiple agents. However, dense communication among agents affects the practicability of DCOP algorithms. In this paper, we propose a novel DCOP algorithm dealing with the previous DCOP algorithms' communication problem by reducing constraints. The contributions of this paper are primarily threefold:① It is proved that removing constraints can effectively reduce the communication burden of DCOP algorithms. ② An criterion is provided to identify insignificant constraints whose elimination doesn't have a great impact on the performance of the whole system. ③ A constraint-reduced DCOP algorithm is proposed by adopting a variant of spectral clustering algorithm to detect and eliminate the insignificant constraints. Our algorithm reduces the communication burdern of the benchmark DCOP algorithm while keeping its overall performance unaffected. The performance of constraint-reduced DCOP algorithm is evaluated on four configurations of cooperative sensor networks. The effectiveness of communication reduction is also verified by comparisons between the constraint-reduced DCOP and the benchmark DCOP.
Simultaneous Localization and Mapping System Based on Labels
Tong Liu, Panpan Liu, Songtian Shang, Yi Yang
2017, 26(4): 534-541. doi:10.15918/j.jbit1004-0579.201726.0413
Abstract:
In this paper a label-based simultaneous localization and mapping (SLAM) system is proposed to provide localization to indoor autonomous robots. In the system quick response(QR) codes encoded with serial numbers are utilized as labels. These labels are captured by two webcams, then the distances and angles between the labels and webcams are computed. Motion estimated from the two rear wheel encoders is adjusted by observing QR codes. Our system uses the extended Kalman filter (EKF) for the back-end state estimation. The number of deployed labels controls the state estimation dimension. The label-based EKF-SLAM system eliminates complicated processes, such as data association and loop closure detection in traditional feature-based visual SLAM systems. Our experiments include software-simulation and robot-platform test in a real environment. Results demonstrate that the system has the capability of correcting accumulated errors of dead reckoning and therefore has the advantage of superior precision.
Single Radar Measurement Method for Antiaircraft Projectile Miss Distance
Wanjun Zhang, Guohui Li, Xiaoying Wu, Kailin Wang, Xuebing Leng
2017, 26(4): 542-547. doi:10.15918/j.jbit1004-0579.201726.0414
Abstract:
To measure miss distance for antiaircraft projectile, a radial velocity identification and positioning method with a single radar is proposed. By analyzing the spatial resolution of multi-frequency ranging radar, the discrimination and testing model of this radar for multi-targets (projectile and target) is established to analyze the systematic error of antiaircraft miss distance. Then through the aerial target flight test and contrast test with optical test equipment, the validity of the measurement method is verified. This new method has the potential to be used in the measurement of antiaircraft projectile miss distance.
Three-Dimensional Discrete Observability Analysis for Air-to-Air Missile Target Tracking
Fei Liu, Zhang Ren, Yuan Liang
2017, 26(4): 548-556. doi:10.15918/j.jbit1004-0579.201726.0415
Abstract:
The interception information of infrared (IR)-guided air-to-air missiles (AAM) is mainly estimated only using the basic bearing measurements. In order to intercept highly maneuverable targets, it is essential to study the system observability to improve the target tracking system performance. The uniqueness of this paper is that the observability analysis is derived based on a discrete three-dimensional(3D) system model. During the maneuvering scenario, the system is approximated by a segment-by-segment system. The relationship between missile-target motion and observability is given by direct and dual approaches. Meanwhile sufficient observability conditions are derived. Moreover, a numerical simulation is conducted and an alternate method is provided to reinforce the proposed observability analysis results.
Actuation Delay-Time Estimation with Imaging Fuze
Yuzhao Li, Zhiqiang Ge, Yan Liu
2017, 26(4): 557-562. doi:10.15918/j.jbit1004-0579.201726.0416
Abstract:
Generally, Doppler fuze can only estimate actuation delay-time with a limited precision. As an improvement, imaging fuze can estimate actuation delay-time more precisely with the available two-dimensional image of the target. In this paper, imprecision of actuation delay-time estimation with Doppler fuze is first analyzed theoretically in brief. Secondly, feasibility analysis and theoretical model of imaging fuze are described, in which a criterion is established for the actuation delay-time based on the image, and then an image based gray-value weighted least square (GWLS) algorithm is presented to calculate actuation delay-time of the imaging fuze. Finally, a simulation model of missile-target near-field encounter is established. Simulation results indicate that actuation delay-time of the imaging fuze is estimated more precisely than by the Doppler fuze.
Chemical Engineering and Materials Science
Molecular Simulation and Catalytic Active Sites Identification of Dammarenediol-II Synthase
Ting Liu, Xiangmei Zhang, Fanglong Zhao, Wenyu Lu
2017, 26(4): 563-570. doi:10.15918/j.jbit1004-0579.201726.0417
Abstract:
Squalene and oxidosqualene cyclizations are regarded as the most complex chemical reactions in the nature, which can achieve protonation, deprotonation,a sequence of hydride and methyl migration. Dammarenediol-Ⅱ synthase (DS), as a kind of 2,3-oxidosqualene-triterpene cyclase, catalyses 2,3-oxidosqualene to form dammarenediol-Ⅱ. To assess the three-dimensional (3D) structure and catalytic active sites of dammarenediol-Ⅱ synthase, utilizing the homology modeling method, 3D models of DS were established in the Modeller9v14 software and I-TASSER server. With the highest sequence identity with DS, human oxidosqualene cyclase 3D models (PDB:1W6K and 1W6J) were chosen as templates. Through further evaluation and optimization, an optimal DS model was obtained consequently. Then several putative catalytic active sites were found through the molecular docking simulation between DS model and product dammarenediol-Ⅱ by using Autodock 4.2. Finally, site-directed mutants of DS were expressed inSaccharomyces cerevisiae, a significant decrease of the yield of dammarenediol-Ⅱ is achieved, which verified the significance of these putative active sites.
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