bob手机在线登陆学报自然版

2021, 41(7): .

Abstract(542) PDF(299)

Abstract:

2021, 41(7): .

Abstract(440) PDF(240)

Abstract:

Dimensional Analysis and Theoretical Study on the Expansion Deformation Behaviors of Thin-Walled Circular Tube

WU Mingze, ZHANG Xiaowei, ZHONG Xianzhe, ZHANG Qingming

2021, 41(7): 679-686. doi:10.15918/j.tbit1001-0645.2020.211

Abstract(839) PDF(359)

Abstract:
The expansion behavior of thin-walled circular tube was studied by the finite element method and the existing expansion experiments. It was found that the geometric dimensioninghandD₁of the expanded tube were mainly affected by the initial geometric parameters of the tube and die, but less affected by the metallic materials and friction coefficient. According to the dimensional analysis, the dimensionless relationships between the geometrical dimensioning (h,D₁) and the main influencing factors were obtained. Then, based on the above dimensionless relationships and the law of conservation of energy, a new prediction model of the steady compression force was put forward, in which the effects of strain hardening and die diameter on the curvature of the bending regions of expanded tube were also taken into account, and the predictions of the current model are in good agreement with experiment and simulation data.

Study on Numerical Simulation of Skipping Stone Movement Characteristics

LEI Juanmian, XIE Wenyang, YU Yong, LIU Qi

2021, 41(7): 687-695. doi:10.15918/j.tbit1001-0645.2020.121

Abstract(667) PDF(341)

Abstract:
Skipping stone is a common solid water bounce movement. Studying its take-off and reentry movement near the water surface has a strong reference significance for the development of the aircraft's high maneuverability penetration ability in the offshore surface. Based on the CFD numerical simulation method,taking the SSTk-ωmodel as the turbulence model,using the overlapping grid technology to couple the N~S equation and the six-degree-of-freedom ballistic equation,a numerical simulation was carried out for the skipping stone of a thin disk in three-dimensional space. The characteristics and movement laws of skipping stone under different working conditions were studied. The results show that the time between the disc contacting the water surface and leaving the water surface calculated by the numerical simulation is in good agreement with the experimental value,and the disc's motion trajectory is consistent with the experimental results. Due to the disc moving forward and also rotating at the same time,a Magnus effect takes place,causing a lateral offset in the trajectory of the disc and a lateral deflection of the posture of the disc itself.

Risk Analysis of Burning and Explosion of Gas Pipeline Network Based on Dynamic Bayesian Network

CHEN Jun, WU Yawei, LI Yuanzhi, QIAN Xinming, YUAN Mengqi

2021, 41(7): 696-705. doi:10.15918/j.tbit1001-0645.2020.170

Abstract(682) PDF(273)

Abstract:
In view of the limitation that the traditional risk analysis method cannot realize dynamic assessment, a risk analysis model of the gas pipeline network based on dynamic Bayesian network was proposed. Based on the causes of pipeline failure and accident consequences, the network structure of the whole process of accident evolution was constructed, and the Markov theory was used to associate the whole process of evolution with time, and finally a risk analysis model based on the dynamic Bayesian network was established. The model calculates the probability of leakage, disaster mode and consequence node based on the Bayesian theory, and realizes the cause diagnosis and accident developing trend prediction of the gas pipeline network accident. Taking "7.4" gas explosion accident in Songyuan city as an example, this model is used to demonstrate the accident deduction technology of the gas pipeline network accident. The results show that the accident is resulted from gas leakage caused by the destruction of the third-party construction, and because the diffusion range of gas in the soil is constantly expanding, the number of restricted spaces in the diffusion range is increasing, and the situation of human activities is more complex, thus increasing the probability of gas accumulation and ignition. Combined with the conditions of the accident scene, the model deduces the probability of the explosion and concludes that the probability of the gas explosion will reach 42.3% after 60 minutes of leakage, which is higher than the safe release probability. The result is basically consistent with the actual situation, which further verifies the feasibility and reliability of the model.

Performance of a Variable Geometry Turbine with Elastically Restrained Guide Vanes under Pulsating Conditions

WANG Zhihui, MA Chaochen, ZHU Fei

2021, 41(7): 706-712,780. doi:10.15918/j.tbit1001-0645.2020.126

Abstract(596) PDF(251)

Abstract:
A turbocharger turbine was proposed based on the concept of elastically restrained guide vane.Firstly,the unsteady characteristics of elastically constrained guide vane turbine and the influence of pulse amplitude and frequency on its performance were studied based on fluid structure coupling (FIS) method.And then,comparing with the traditional variable nozzle turbine (VNT),the new VNT was investigated to analyze the reason of its performance change.The comparison results show that,the smaller the pulse amplitude and the lower the frequency,the flow rate of the new VNT is higher,the output power increase rate is higher,and the efficiency decrease rate is lower.Based on the inlet flow angle and the stator outlet pressure loss distribution,the influence of pulse amplitude and frequency on elastically constrained guide vane turbine performance can be concluded.

Effect of Backing Plate Condition on Fracture Cone Shape ofAlumina Ceramic Thin Tiles

YU Yilei, JIANG Zhaoxiu, WANG Xiaodong, REN Wenke, DU Zhonghua, GAO Guangfa

2021, 41(7): 713-720. doi:10.15918/j.tbit1001-0645.2020.107

Abstract(550) PDF(272)

Abstract:
The influence of backplane conditions on the size and shape of ceramic cone angle formed in alumina ceramic/metal composite armor during the 12.7 mm penetration resistance was studied by means of ballistic penetration test and finite element numerical simulation, and the formation process and mechanism of ceramic cone were analyzed. The results show that the effect of back thickness is particularly obvious on the size of the ceramic cone. When the back thickness increases, the intersection of main cracks is near the target interface, here the tensile shear crack expansion plays a major role. When the thickness ratio of the back to ceramic thickness is less than 1, every 1/6 increase of the thickness ratio can cause 5% size increase of ceramic cone angle. When the interfacial wave impedance difference decreases, that is, when the back plate material wave impedance increases, the stress wave reflected from the interface weakens, thus reducing the damage to ceramics, and the ceramic fracture cone angle also decreases.

Three Dimensional Reconstruction Method of Pipeline Based on Snake Model

LIU Shaoli, ZHANG Wenxiong, WU Tianyi, LIU Jianhua, WANG Zhenjie, HU Jia

2021, 41(7): 721-727. doi:10.15918/j.tbit1001-0645.2020.141

Abstract(588) PDF(294)

Abstract:
Aiming at the difficult problem of high-precision and fast pipeline measurement applied in aerospace, a 3D pipeline reconstruction method was proposed based on snake model. Making full use of the edge features of the gray image of the pipeline and eliminating image noise by means of threshold segmentation and Gaussian filtering, the method was arranged firstly to combine the snake model to obtain accurate pipeline image edges, carry out iteration with the greedy algorithm to ensure convergence efficiency, and use the principle of Epipolar constraint to obtain a two-dimensional pipeline centerline point cloud. And then, a three-dimensional model of pipeline was reconstructed based on the principle of visual projection. Finally, the designed results were optimized to ensure the reconstruction accuracy according to the photos taken by the multi-eye vision system. The results show that the measurement accuracy of the method for pipelines can reach ±0.15 mm, the measurement process is simple and efficient without more operators. The new method can measure the bending radius of the pipeline arc section, adapting industrial applications.

Research on Somatosensory Simulation Algorithm Based on Six-Degree-of-Freedom Platform

WANG Junzheng, JIANG Shuo, WANG Shoukun, SHEN Wei

2021, 41(7): 728-733. doi:10.15918/j.tbit1001-0645.2020.097

Abstract(674) PDF(339)

Abstract:
Aiming at the needs for dynamic fidelity and platform's workspace, a somatosensory control strategy based on washout algorithm was applied to the six-degree-of-freedom paralleled motion simulator. First, the system was designed and its mathematical model was created. Then, by analyzing Human's perception mechanism, an acceleration-control based somatosensory simulation algorithm was put forward. Then, many possibly existed complicated working conditions in simulation driving and corresponding acceleration control modes were specifically studied. Finally, unity simulation and experiments were carried out to verify the feasibility of the proposed control algorithm and the control performance. The results show the significant improvement of platform's dynamic fidelity in limited motion range.

Ship Target Detection in Optical Images Based on Improved Mask R-CNN

MA Xiao, SHAO Limin, JIN Xin, LU Huimin, XIAO Junhao, GU Dongliang

2021, 41(7): 734-744. doi:10.15918/j.tbit1001-0645.2020.076

Abstract(742) PDF(367)

Abstract:
A ship target detection method was proposed based on improved Mask R-CNN (mask region-based convolution neural networks) to solve the problem that the classical rectangular detection boxes within the typical target detection algorithms based on the convolutional neural network will frame many irrelevant areas in ship target detecting, which can lead to problems such as missed detection and false detection. On the basis of Mask R-CNN, a discrimination module, category prediction branch, and semantic segmentation branch were added, thus, the target localization and category prediction of the ship targets in the optical images collected by the vision system were performed. At the same time, the edge contour of the ship target was obtained and semantic segmentation of warship targets was realized, providing more accurate information for the maritime unmanned combat system. Experimental results show that, keeping a high detection rate and operation efficiency, the proposed method can achieve lower false detection rate, higher average accuracy of ship target detection, better ship target detection performance.

Weakly Supervised Multilabel Classification Combining Sample Similarity

LUO Senlin, WANG Haizhou, PAN Limin, SUN Xiaoguang

2021, 41(7): 745-751. doi:10.15918/j.tbit1001-0645.2020.117

Abstract(535) PDF(227)

Abstract:
Multilabel classification is a machine learning method to improve the performance of multi label joint decision by label correlation. In practical application scenarios, data labels are easy to be incomplete, which can lead to the reduction of available training data, and it is difficult to train the model adequately. Moreover, it is easy to cause the increase of label distribution variance, the deviation of correlation knowledge, and the limitation of multi label classification effect. To solve the problems, a weak supervised multi label classification method based on sample similarity was proposed. The method was arranged to use label correlation and sample similarity to recover labels to improve data utilization, and to embed label recovery into the training process to correct the bias in the model learning process. Based on the proximal accelerated gradient method, parameter optimization was carried out, and a multi label classification model was established for weak supervised learning scene. Experiments were completed with real data set. The results show that the method can effectively improve the classification ability of the model for the incomplete labels according to the similarity of samples, possessing high practical value.

Collective Matrix Factorization Based on Knowledge Representation Learning

LIU Qiongxin, QIN Mingshuai

2021, 41(7): 752-757. doi:10.15918/j.tbit1001-0645.2018.055

Abstract(578) PDF(270)

Abstract:
In order to solve the problem of user feedback data sparseness existed in collaborative filtering method, a collective matrix factorization method was proposed based on knowledge graph. The method was arranged to make up for the scarce of the user feedback data with additional item sematic information. Learning item embeddings from items’ knowledge graph, the method was designed to jointly factorize a user feedback matrix and an item relatedness matrix with the same item embeddings. Experimental results on two datasets show that the proposed method can significantly improve the performance of matrix factorization models, and it can solve the cold start problem to some extent.

A Real-Time Algorithm for Visual Detection of High-Speed Unmanned Surface Vehicle Based on Deep Learning

ZHOU Zhiguo, LIU Kaiyuan, ZHENG Yipeng, QU Chong, WANG Liming

2021, 41(7): 758-764. doi:10.15918/j.tbit1001-0645.2018.317

Abstract(704) PDF(390)

Abstract:
In order to solve the problem of high real-time, and robustness to disturbances such as scene changes and wave reflections during visual detection in unmanned surface vehicle(USV) autonomous navigation, a real-time algorithm for visual detection of high-speed USV based on deep learning was proposed. First, a neural network MobileNet was arranged to quickly extract the full-image features. Then, a detection network based on SSD was used to fuse feature maps of each layer and achieve fast and multi-scale detection. Finally, the algorithm was implemented and validated on a hardware platform embedded GPU NVIDIA Jetson TX2. The results show that the proposed algorithm can quickly detect multiple types of specific obstacle on the water with strong robustness and multi-scale detection ability, and the detection speed of single-frame video within 50 ms.

Personalized Training Plan Generation for Improving Driving Attention

LIANG Wei, WANG Yu, LIAO Zhangliang, LI Xiangyuan

2021, 41(7): 765-773. doi:10.15918/j.tbit1001-0645.2020.022

Abstract(901) PDF(312)

Abstract:
Dr iving attention is one of the most important factors in safe driving. Due to the danger during the training process,it is hard to train a driver to improve their attention in the driving behavior. In this paper,a personalized driving attention training plan generation method was proposed based on virtual reality platform. Based on the technique of eye tracking on the VR platform,gathering the attention habits of users,considering the driving behaviors,the method was arranged to generate personalized driving attention training plan automatically. In the experiment,the personalized driving attention training of users was carried out according to the generated training plan. Comparing the performance before training with the performance after the training,the effectiveness of the new method was evaluated. Experimental results show that the proposed method can effectively improve the user's driving attention level and perform better than traditional method.

Design and Implementation of High Detection Rate Frequency Measurement Method Based on Mono-Bit Receiver

MA Yuehong, ZHANG Weitao, HUI Hui, GUO Zhirui

2021, 41(7): 774-780. doi:10.15918/j.tbit1001-0645.2020.225

Abstract(630) PDF(275)

Abstract:
A method to improve the detection rate of dual signals in a mono-bit receiver was studied. First, the filter bank was used to divide the signal into multiple channels, and each channel was sampled and measured independently, and the detection rate was improved by reducing the influence of harmonics generated by nonlinear changes. Secondly, according to the statistics and analysis carried out on the false detection data after frequency measurement, a compensation matrix based on the analysis results was designed and used to correct the false detection results. The simulation results show that this method effectively improves the dual-signal detection rate of the mono-bit receiver, and the detection rate of large dynamic range is improved more obviously. When the normalized gain difference is 6 dB, the detection rate is 3.5 times of the original detection rate. Related research methods and conclusions have certain reference significance for practical engineering applications.

Application of Biomass Carbon in Direct Carbon Solid Oxide Fuel Cell

QIAO Jinshuo, CHEN Haitao, WANG Zhenhua, SUN Wang, LI Haijun, SUN Kening

2021, 41(7): 781-790. doi:10.15918/j.tbit1001-0645.2020.023

Abstract(736) PDF(344)

Abstract:
In order to take activated carbon,carbonized paulownia leaves and orange peel as the fuel of direct carbon fuel cell,their physicochemical and electrochemical properties were investigated.The carbon type in fuel was characterized byX-ray diffraction method.And the energy dispersive spectrometer and Raman patterns were used to analyze the element content of fuel.The specific surface area and pore structure of the fuels were tested by BET.The results show that carbonized orange peel fuel contains potassium and high content of amorphous carbon,which is beneficial to the Boudouard reaction and electrochemical reaction of carbon.The carbonized orange peel possesses a specific surface area of 74 m²· g^-1,a small porosity and a large bulk density,which indicate the large contact interface between the anode and fuel.When the carbonized orange peel is used as a fuel,the maximum power density of a fuel cell can reach up to 572.6 m W· cm^-2at 800 ℃.Obtaining from carbonization of non-woody orange peels with high water content,the biomass carbon can provide excellent performance for the fuel of direct carbon fuel cell.

Submission System

Author Related

Writing Norms

Links

2021 Vol. 41, No. 7

Archive