Welcome to Journal of Beijing Institute of Technology

2018 Vol. 27, No. 1

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Quantitative Method of the Structural Damage Identification of Gas Explosion Based on Case Study: The Shanxi “11.23” Explosion Investigation
Huanjuan Zhao, Yiran Yan, Xinming Qian
2018, 27(1): 1-14. doi:10.15918/j.jbit1004-0579.201827.0101
Abstract:
In order to present a retrospective analysis of exposition accidents using input data from investigation processes, data from a specific accident was examined, in which we analyzed possible involved gas species (liquefied petroleum gas; nature gas) and computed their concentrations and distributions based on the interactions between the structures and the effects of the explosion. In this study, 5 scenarios were created to analyze the impact effect. Moreover, a coupling algorithm was put into practice, with a practical outflow boundary and joint strength are applied.Finally, the damage effects of each scenario were simulated. Our experimental results showed significant differences in the 5 scenarios concerning the damage effects on the building structures. The results from scenario 3 agree with the accident characteristics, demonstrating the effectiveness of our proposed modeling method. Our proposed method reflects gas properties, species and the concentration and distribution, and the simulated results validates the root cause, process, and consequences of accidental explosions. Furthermore, this method describes the evolution process of explosions in different building structures. Significantly, our model demonstrates the quantatative explosion effect of factors like gas species, gas volumes, and distributions of gases on explosion results. In this study, a feasible, effective, and quantitative method for structure safety is defined, which is helpful to accelerate the development of safer site regulations.
Compressional Deformation in Indentation Process for Microlens Array Mold
Yaqun Bai, Xibin Wang, Tianfeng Zhou, Zhiqiang Liang, Guang Li
2018, 27(1): 15-21. doi:10.15918/j.jbit1004-0579.201827.0102
Abstract:
The structure of a microlens array(MLA) can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property, thereby work time can be saved. Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array, namely micro lens and MLA. Based on finite element simulation method, factors affecting the form accuracy, such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays, are determined, and the results are verified by experiments under the same conditions. Meanwhile, indenter compensation method is proposed to improve form accuracy of single dimple, and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA's indentation processing. Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism. Finally, it is found that MLA at pitches higher than 1.47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.
Development and Verification of the Equilibrium Strategy for Batteries in Electric Vehicles
Rui Xiong, Yanzhou Duan
2018, 27(1): 22-35. doi:10.15918/j.jbit1004-0579.201827.0103
Abstract:
The inconsistency of the cells in a battery pack can affect its lifespan, safety and reliability in the electric vehicles. The balanced system is an effective technique to reduce its inconsistency and improve the operating performance. A hybrid equilibrium strategy based on decision combing battery state-of-charge (SOC) and voltage has been proposed. The battery SOC is estimated through an improved least squares method. An equalization hardware in loop(HIL) platform has been constructed. Based on this HIL platform, equilibrium strategy has been verified under the constant-current-constant-voltage (CCCV) and dynamic-stress-test (DST) conditions. Experimental results indicate that the proposed hybrid equalization strategy can achieve good balance effect and avoid the overcharge and over-discharge of the battery pack at the same time.
Modeling and Optimization of Heat Dissipation Structure of EV Battery Pack
Xinggang Li, Rui Xiong
2018, 27(1): 29-35. doi:10.15918/j.jbit1004-0579.201827.0104
Abstract:
In order to solve the problems of high temperature and inconsistency in the operation of electric vehicle (EV) battery pack,computational fluid dynamics (CFD) simulation method is used to simulate and optimize the heat dissipation of battery pack.The heat generation rate at different discharge magnifications is identified by establishing the heat generation model of the battery.In the forced air cooling mode,the Fluent software is used to compare the effects of different inlet and out-let directions,inlet angles,outlet angles,outlet sizes and inlet air speeds on heat dissipation.The simulation results show that the heat dissipation effect of the structure with the inlet and outlet on the same side is better than that on the different sides;the appropriate inlet angle and outlet width can improve the uniformity of temperature field;the increase of the inlet speed can improve the heat dissipation effect significantly.Compared with the steady temperature field of the initial structure, the average temperature after structure optimization is reduced by 4.8益and the temperature difference is reduced by 15.8℃,so that the battery can work under reasonable temperature and temperature difference.
Scheduling Optimization of Space Object Observations for Radar
Xiongjun Fu, Liping Wu, Chengyan Zhang, Min Xie
2018, 27(1): 36-42. doi:10.15918/j.jbit1004-0579.201827.0105
Abstract:
An optimizing method of observation scheduling based on time-division multiplexing is proposed in this paper, and its efficiency is verified by outdoor experiments.The initial observation scheduling is first obtained by using a semi-random search algorithm, and secondly the connection time pair(CTP) between adjacent objects is optimized by using a genetic algorithm.After obtaining these two parameters, the final observation scheduling can be obtained. According to pre-designed tracks between each adjacent objects in observation order, the seamless observation of neighboring targets is derived by automatically steering the antenna beam, so the observation efficiency is improved.
Chaff Jamming Recognition of Radar
Min Xie, Shuang Zhao, Xiongjun Fu, Tianyu Zhang, Kaiqiang Liu
2018, 27(1): 43-50. doi:10.15918/j.jbit1004-0579.201827.0106
Abstract:
A modified chaff jamming recognition method of radar is investigated using grey relational analysis (GRA) based on the difference in echo correlation characteristics between a complex rigid target and chaff cloud in time domain. Slice method (SM), a novel modeling approach, is proposed to construct an electromagnetic scattering model of chaff cloud in a scenario with slowly moving platform that is targeted. The diffusion characteristics and echo characteristics of the chaff cloud are analyzed. The GRA of a real target and chaff cloud shows that the adjacent return waves have a good correlation for the target but a weak correlation for chaff cloud. Since the correlation degree of chaff cloud's echo is far lower than that of a complex rigid target's, the chaff jamming can be identified by setting a reasonable threshold. Simulation results are presented to verify the effectiveness of this method.
Particle Filter Object Tracking Algorithm Based on Sparse Representation and Nonlinear Resampling
Zheyi Fan, Shuqin Weng, Jiao Jiang, Yixuan Zhu, Zhiwen Liu
2018, 27(1): 51-57. doi:10.15918/j.jbit1004-0579.201827.0107
Abstract:
Object tracking with abrupt motion is an important research topic and has attracted wide attention. To obtain accurate tracking results, an improved particle filter tracking algorithm based on sparse representation and nonlinear resampling is proposed in this paper. First, the sparse representation is used to compute particle weights by considering the fact that the weights are sparse when the object moves abruptly, so the potential object region can be predicted more precisely. Then, a nonlinear resampling process is proposed by utilizing the nonlinear sorting strategy, which can solve the problem of particle diversity impoverishment caused by traditional resampling methods. Experimental results based on videos containing objects with various abrupt motions have demonstrated the effectiveness of the proposed algorithm.
Automatic Satisfaction Analysis in Call Centers Considering Global Features of Emotion and Duration
Jing Liu, Chaomin Wang, Yingnan Zhang, Pengyu Cong, Liqiang Xu, Zhijie Ren, Jin Hu, Xiang Xie, Junlan Feng, Jingming Kuang
2018, 27(1): 58-64. doi:10.15918/j.jbit1004-0579.201827.0108
Abstract:
Analysis of customers' satisfaction provides a guarantee to improve the service quality in call centers. In this paper, a novel satisfaction recognition framework is introduced to analyze the customers' satisfaction. In natural conversations, the interaction between a customer and its agent take place more than once. One of the difficulties insatisfaction analysis at call centers is that not all conversation turns exhibit customer satisfaction or dissatisfaction. To solve this problem, an intelligent system is proposed that utilizes acoustic features to recognize customers' emotion and utilizes the global features of emotion and duration to analyze the satisfaction. Experiments on real-call data show that the proposed system offers a significantly higher accuracy in analyzing the satisfaction than the baseline system. The averageFvalue is improved to 0.701 from 0.664.
Oversample Reconstruction Based on a Strong Inter-Diagonal Matrix for an Optical Microscanning Thermal Microscope Imaging System
Meijing Gao, Ailing Tan, Jie Xu, Weiqi Jin, Zhenlong Zu, Ming Yang
2018, 27(1): 65-73. doi:10.15918/j.jbit1004-0579.201827.0109
Abstract:
Based on a strong inter-diagonal matrix and Taylor series expansions, an oversample reconstruction method was proposed to calibrate the optical micro-scanning error. The technique can obtain regular 2×2 microscanning undersampling images from the real irregular undersampling images, and can then obtain a high spatial oversample resolution image. Simulations and experiments show that the proposed technique can reduce optical micro-scanning error and improve the system's spatial resolution. The algorithm is simple, fast and has low computational complexity. It can also be applied to other electro-optical imaging systems to improve their spatial resolution and has a widespread application prospect.
Dwell Scheduling Algorithm for Digital Array Radar
Qun Zhang, Di Meng, Ying Luo, Yijun Chen
2018, 27(1): 74-82. doi:10.15918/j.jbit1004-0579.201827.0110
Abstract:
Aiming at the problem of resource allocation for digital array radar(DAR), a dwell scheduling algorithm is proposed in this paper. Firstly, the integrated priority of different radar tasks is designed,which ensures that the imaging tasks are scheduled without affecting the search and tracking tasks; Then, the optimal scheduling model of radar resource is established according to the constraints of pulse interleaving; Finally, a heuristic algorithm is used to solve the problem and a sparse-aperture cognitive ISAR imaging method is used to achieve partial precision tracking target imaging. Simulation results demonstrate that the proposed algorithm can both improve the performance of the radar system, and generate satisfactory imaging results.
Dielectric Properties and Microwave Heating of Molybdenite Concentrate at 2.45 GHz Frequency
Yonglin Jiang, Bingguo Liu, Jinhui Peng, Libo Zhang
2018, 27(1): 83-91. doi:10.15918/j.jbit1004-0579.201827.0111
Abstract:
Dielectric properties were measured using cavity perturbation method.The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave.This process was conducted to show the microwave absorption properties of molybdenite concentrate and the feasibility of microwave roasting molybdenite concentrate to prepare high purity MOO3.The dielectric constant,dielectric loss,and loss tangent increase from 3.51 to 5.04,0.22 to 0.51 and 0.065 to 0.102 respectively.They are proportional to the apparent density of molybdenite concentrate in the range of 0.9-1.4 g/cm3.The results show that the molybdenite concentrate has good microwave absorption capacity in the conventional density range.The temperature rising curves show that the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness.The temperature of concentrate sample of 100g reaches approximately 800℃ after 5 min of microwave treatment at 0.5 kW of power. Our findings show that it is feasible to prepare high-purity MOO3from molybdenite concentrate by microwave roasting.
Online Observability-Constrained Motion Suggestion via Efficient Motion Primitive-Based Observability Analysis
Zheng Rong, Shun'an Zhong, Nathan Michael
2018, 27(1): 92-102. doi:10.15918/j.jbit1004-0579.201827.0112
Abstract:
An active perception methodology is proposed to locally predict the observability condition in a reasonable horizon and suggest an observability-constrained motion direction for the next step to ensure an accurate and consistent state estimation performance of vision-based navigation systems. The methodology leverages an efficient EOG-based observability analysis and a motion primitive-based path sampling technique to realize the local observability prediction with a real-time performance. The observability conditions of potential motion trajectories are evaluated, and an informed motion direction is selected to ensure the observability efficiency for the state estimation system. The proposed approach is specialized to a representative optimization-based monocular vision-based state estimation formulation and demonstrated through simulation and experiments to evaluate the ability of estimation degradation prediction and efficacy of motion direction suggestion.
Parameters Sensitivity Analysis and Correction for Concrete Damage Plastic Model
Yaqin Jiang, Pengfei Xu, Chengzhi Wang, Dianshu Liu
2018, 27(1): 103-108. doi:10.15918/j.jbit1004-0579.201827.0113
Abstract:
In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through a convenient cube unit test was conducted. The results showed that the peak strength strain was independent of the hardening ductility parameter DH, but affected by AH, BH, and CH. The softening ductility was mainly related to the softening ductility parameter AS, but not affected by the damage ductility exponent BS. In case that the model with default parameters failed to match the AS-controlled damage softening phase, an optimized model with an AS correction was developed. The corrected model with the AS value of 2 matched well with the code model, and exhibited good feasibility in predicting the stress-strain curve of different grades of concrete. Moreover, the practicability of the corrected model was further validated by the conventional triaxial test. The simulated curve exhibited favorable consistence with the trial curve. Therefore, the model with parameter correction could provide a prospective reference for predicting the mechanical properties of concrete.
Propagating Characteristic of Premixed Methane-Oxygen Deflagration in the Coal Mine Lane Including a Refuge Chamber
Huanjuan Zhao, Yiran Yan, Yinghua Zhang, Yukun Gao
2018, 27(1): 109-117. doi:10.15918/j.jbit1004-0579.201827.0114
Abstract:
In order to investigate detonation propagation and distribution problems of premixed CH4+2O2mixture around a concrete structure such as a refuge chamber, detonation experiments in one small size tube were conducted. A simulation method was developed to obtain the flow field load distribution in the coal mine lane and pressure load of each part for the refuge chamber. Firstly, a physical model of a full-size explosion-test lane was established, which included the refuge chamber. With the calculations of the exact initial detonation pressure, the propagation characteristics of CH4+2O2premixed mixture detonation in the lane was simulated. Simulation results of various parts from AUTODYN are recorded, and the shock wave arrival time and the pressure peak can be observed from the detonation pressure-time curve over the changing propagation distance. So curve differences in different locations cannot be ignored. Then by detonation experiments in the small size tube, detonation pressure-time curves and velocity were obtained. Finally the simulation waveform of variation curve agreed well with the experimental results, which validated the detonation simulation method. The difference between shockwaves of the two sensors confirmed that detonation wave changed along with distance and time. These results should be taken into serious consideration for the detonation progration and distribution problem in future researches.
Bionic Attitude Transformation Combined with Closed Motion for a Free Floating Space Robot
Zhanpeng Sun, Yongjin Lu, Lixian Xu, Liang Wang
2018, 27(1): 118-126. doi:10.15918/j.jbit1004-0579.201827.0115
Abstract:
In order to realize the small error attitude transformation of a free floating space robot, a new method of three degrees of freedom(DOF) attitude transformation was proposed for the space robot using a bionic joint. A general kinematic model of the space robot was established based on the law of linear and angular momentum conservation. A combinational joint model was established combined with bionic joint and closed motion. The attitude transformation of planar, two DOF and three DOF is analyzed and simulated by the model, and it is verified that the feasibility of attitude transformation in three DOF space. Finally, the specific scheme of disturbance elimination in attitude transformation is presented and simulation results are obtained. Therefore, the range of application field of the bionic joint model has been expanded.
Improving Parallel Corpus Quality for Chinese-Vietnamese Statistical Machine Translation
Huu-anh Tran, Yuhang Guo, Ping Jian, Shumin Shi, Heyan Huang
2018, 27(1): 127-136. doi:10.15918/j.jbit1004-0579.201827.0116
Abstract:
The performance of a machine translation system heavily depends on the quantity and quality of the bilingual language resource.However, getting a parallel corpus, which has a large scale and is of high quality, is a very difficult task especially for low resource languages such as Chinese-Vietnamese. Fortunately, multilingual user generated contents (UGC), such as bilingual movie subtitles, provide us access to automatic construction of the parallel corpus. Although the amount of UGC parallel corpora can be considerable, the original corpus is not suitable for statistical machine translation (SMT) systems. The corpus may contain translation errors, sentence mismatching, free translations, etc. To improve the quality of the bilingual corpus for SMT systems, three filtering methods are proposed:sentence length difference, the semantic of sentence pairs, and machine learning. Experiments are conducted on the Chinese to Vietnamese translation corpus. Experimental results demonstrate that all the three methods effectively improve the corpus quality, and the machine translation performance (BLEU score) can be improved by 1.32.
Recommending Personalized POIs from Location Based Social Network
Haiying Che, Di Sang, Billy Zimba
2018, 27(1): 137-145. doi:10.15918/j.jbit1004-0579.201827.0117
Abstract:
Location based social networks (LBSNs) provide location specific data generated from smart phone into online social networks thus people can share their points of interest (POIs). POI collections are complex and can be influenced by various factors, such as user preferences, social relationships and geographical influence. Therefore, recommending new locations in LBSNs requires to take all these factors into consideration. However, one problem is how to determine optimal weights of influencing factors in an algorithm in which these factors are combined. The user similarity can be obtained from the user check-in data, or from the user friend information, or based on the different geographical influences on each user's check-in activities. In this paper, we propose an algorithm that calculates the user similarity based on check-in records and social relationships, using a proposed weighting function to adjust the weights of these two kinds of similarities based on the geographical distance between users. In addition, a non-parametric density estimation method is applied to predict the unique geographical influence on each user by getting the density probability plot of the distance between every pair of user's check-in locations. Experimental results, using foursquare datasets, have shown that comparisons between the proposed algorithm and the other five baseline recommendation algorithms in LBSNs demonstrate that our proposed algorithm is superior in accuracy and recall, furthermore solving the sparsity problem.
Layer-Constrained Triangulated Irregular Network Algorithm Based on Ground Penetrating Radar Data and Its Application
Zhenwu Wang, Jianqiang Ma
2018, 27(1): 146-154. doi:10.15918/j.jbit1004-0579.201827.0118
Abstract:
In this paper, a layer-constrained triangulated irregular network (LC-TIN) algorithm is proposed for three-dimensional (3D) modelling, and applied to construct a 3D model for geological disease information based on ground penetrating radar (GPR) data. Compared with the traditional TIN algorithm, the LC-TIN algorithm introduced a layer constraint to the discrete data points during the 3D modelling process, and it can dynamically construct networks from layer to layer and implement 3D modelling for arbitrary shapes with high precision. The experimental results validated this method, the proposed algorithm not only can maintain the rationality of triangulation network, but also can obtain a good generation speed. In addition, the algorithm is also introduced to our self-developed 3D visualization platform, which utilized GPR data to model geological diseases. Therefore the feasibility of the algorithm is verified in the practical application.
Mechanical Performances and Morphology of LDPE/UHMWPE Single-Polymer Composites Produced by Extrusion-Calendering Method
Jian Wang, Ziran Du, Tong Lian, Jiong Peng
2018, 27(1): 155-160. doi:10.15918/j.jbit1004-0579.201827.0119
Abstract:
Extrusion-calendering method was developed to prepare single-polymer composites (SPCs) of ultra-high molecular weight polyethylene (UHMWPE) fabric reinforcing low density polyethylene (LDPE). Differential scanning calorimeter (DSC) experiments were executed to determine the setup of extrusion temperature. Effects of the die temperature on the tensile and interfacial performances of SPCs were studied through the tensile and T-peel tests, respectively. The results showed that both tensile strength and modulus increased initially and decreased afterwards as the temperature increased. The peak values of tensile strength and modulus of PE SPCs, which are 10.8 and 3.5 times as high as those of the unreinforced LDPE respectively, were obtained at 150.℃. Higher temperatures also give a positive effect on peel strength. Scanning electron microscopy (SEM) and camera were also used to observe the morphology of the SPCs samples.
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