NUMERICAL SIMULATION OF WATER ENVIRONMENT IN RADIAL SAND RIDGES AREA OF THE YELLOW SEA

TAO JIANFENG,WANG ZHEN,ZHANG CHANGKUAN 한국수자원학회 2005 한국수자원학회 학술대회 Vol.2005 No.1

Optimization and Control of Cable Tensions for Hyper-redundant Snake-arm Robots

Jianfeng Tao,Chengjin Qin,Zhilin Xiong,Xiang Gao,Chengliang Liu 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.11

Based on the feedback linearization of joints motion and the tension optimization of cables, a hyperredundant snake-arm robot control strategy is presented to solve the problems caused by the joint motion coupling and the cable drive redundancy. First, a hierarchical control system architecture of snake-arm robot is developed. Subsequently, the computed torque control method is utilized to decouple the motion in the joint space, and the tension distribution satisfying the constraint condition is obtained in the cable space by quadratic programming. Since it is hard and also expensive to feedback joint motion and cable tension by sensors, the cable tensions are obtained by the system dynamics equation and the position and speed of joints motion is calculated approximately from the driving electric motors’ position. Finally, the control performance under three typical conditions is studied by numerical simulation. The results demonstrate that the presented method can effectively limit the cable tensions within the range of the minimum preload tension and the maximum allowable tension.

Design of a MEMS sensor array for dam subsidence monitoring based on dual-sensor cooperative measurements

( Tao Tao ),( Jianfeng Yang ),( Wei Wei ),( Marcin Woźniak ),( Rafał Scherer ),( Robertas Damaševičius ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.10

With the rapid development of the Chinese water project, the safety monitoring of dams is urgently needed. Many drawbacks exist in dams, such as high monitoring costs, a limited equipment service life, long-term monitoring difficulties. MEMS sensors have the advantages of low cost, high precision, easy installation, and simplicity, so they have broad application prospects in engineering measurements. This paper designs intelligent monitoring based on the collaborative measurement of dual MEMS sensors. The system first determines the endpoint coordinates of the sensor array by the coordinate transformation relationship in the monitoring system and then obtains the dam settlement according to the endpoint coordinates. Next, this paper proposes a dual-MEMS sensor collaborative measurement algorithm that builds a mathematical model of the dual-sensor measurement. The monitoring system realizes mutual compensation between sensor measurement data by calculating the motion constraint matrix between the two sensors. Compared with the single-sensor measurement, the dual-sensor measurement algorithm is more accurate and can improve the reliability of long-term monitoring data. Finally, the experimental results show that the dam subsidence monitoring system proposed in this paper fully meets the engineering monitoring accuracy needs, and the dual-sensor collaborative measurement system is more stable than the single-sensor monitoring system.

Cryptanalysis of a Biometric-based Multi-Server Authentication Scheme

Tao Wan,Nan Jiang,Jianfeng Ma,Lin Yang 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.2

Authentication and key agreement protocol becomes an important security issue for multi-server architecture. Combining biometrics with password enhances the level of security. Recently, Baruah et al. analyzed that Mishra et al.’s protocol has several drawbacks and proposed an improved biometric based multi-server authentication scheme. They claimed that their scheme satisfies all the required security attributes for a secure authentication. In this paper, we indicate that their scheme is not secure against key reveal attack, replay attack, and smart card forgery attack. Any registered user can retrieve the session key or launch the replay attack by eavesdropping on the communication channel. In addition, registered user can forge smart card when colluding with registered server.

An investigation of the mechanical property and thermal shock behavior of machinable B₄C/BN ceramic composites

Tao Jiang,Haiyun Jin,Zhihao Jin,Jianfeng Yang,Guanjun Qiao 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.1

Machinable B₄C/BN ceramic composites were fabricated by a hot-pressing process at 1,850 ℃ for 1 h under a pressure of 30MPa. In this article, the mechanical property, thermal shock behavior and machinability of the B₄C/BN ceramic composites were investigated. The fracture strength and fracture toughness of B₄C/BN nanocomposites were significantly improved in comparison with B₄C/BN microcomposites. The Vickers hardness of B₄C/BN nanocomposites and B₄C/BN microcomposites decreased gradually with an increase in the content of h-BN, while the machinability of B₄C/BN nanocomposites and B₄C/BN microcomposites were significantly improved. The B₄C/BN ceramic composites with an h-BN content of more than 20 wt% exhibited excellent machinability. The thermal shock resistance of the B₄C/BN ceramic composites was much better than that of the B₄C monolith, and the thermal shock resistance of B₄C/BN nanocomposites was much better than that of B₄C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B₄C monolith was about 300℃, while the ΔTc of B₄C/BN microcomposites was about 500℃ and the ΔTc of B₄C/BN nanocomposites was about 600℃. Machinable B₄C/BN ceramic composites were fabricated by a hot-pressing process at 1,850 ℃ for 1 h under a pressure of 30MPa. In this article, the mechanical property, thermal shock behavior and machinability of the B₄C/BN ceramic composites were investigated. The fracture strength and fracture toughness of B₄C/BN nanocomposites were significantly improved in comparison with B₄C/BN microcomposites. The Vickers hardness of B₄C/BN nanocomposites and B₄C/BN microcomposites decreased gradually with an increase in the content of h-BN, while the machinability of B₄C/BN nanocomposites and B₄C/BN microcomposites were significantly improved. The B₄C/BN ceramic composites with an h-BN content of more than 20 wt% exhibited excellent machinability. The thermal shock resistance of the B₄C/BN ceramic composites was much better than that of the B₄C monolith, and the thermal shock resistance of B₄C/BN nanocomposites was much better than that of B₄C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B₄C monolith was about 300℃, while the ΔTc of B₄C/BN microcomposites was about 500℃ and the ΔTc of B₄C/BN nanocomposites was about 600℃.

Novel Passive Snubber Suitable for Three-Phase Single-Stage PFC Based on an Isolated Full-Bridge Boost Topology

Tao Meng,Hongqi Ben,Daqing Wang,Jianfeng Song 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3

In this paper a novel passive snubber is proposed, which can suppress the voltage spike across the bridge leg of the isolated full-bridge boost topology. The snubber is composed of capacitors, inductors and diodes. Two capacitors connected in series are used to absorb the voltage spike and the energy of each capacitor can be transferred to the load during one switching cycle by the resonance of the inductors and capacitors. The operational principle of the passive snubber is analyzed in detail based on a three-phase power factor correction (PFC) converter, and the design considerations of both the converter and the snubber are given. Finally, a 3kW laboratory-made prototype is built. The experimental results verify the theoretical analysis and evaluations. They also prove the validity and feasibility of the proposed methods.

Evaluation of the seismic performance of butt-fusion joint in large diameter polyethylene pipelines by full-scale shaking table test

Shi Jianfeng,Feng Ying,Tao Yangji,Guo Weican,Yao Riwu,Zheng Jinyang 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.9

High-density polyethylene (HDPE) pipelines in nuclear power plants (NPPs) have to meet high requirements for seismic performance. HDPE pipes have been proved to have good seismic performance, but joints are the weak links in the pipelines, and pipeline failures usually initiate from the defects inside the joints. Limited data are available on the seismic performance of butt-fusion joints of HDPE pipelines in NPPs, especially in terms of defects changes inside the joints after earthquakes. In this paper, full-scale shaking table tests were performed on a test section of suspended HDPE pipelines in an NPP, which included straight pipes, elbows, and 10 butt-fusion joints. During the tests, the seismic load-induced strain of the joints was analyzed by strain gauges, and it was much smaller than the internal pressure and self-weight-induced strain. Before and after the shaking table tests, phased array ultrasonic testing (PA-UT) was conducted to detect defects inside the joints. The locations, numbers, and dimensions of the defects were analyzed. It was found that defects were more likely to occur in elbows joints. No new defect was observed after the shaking table tests, and the defects showed no significant growth, indicating the satisfactory seismic performance of the butt-fusion joints.

A Novel Dynamic Time Wrapping Similarity Algorithm Optimized by Multi-Granularity

Xu Jianfeng,Tang Tao,Zhang Yuanjian 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.10

Dynamic time warping algorithm (DTW) is a method of measuring the similarity of time series. Concerning the problem that DTW cannot keep high classification accuracy when the computation speed improved, a FG-DTW method based on the idea of naive granular computing is proposed. In this method, firstly, better temporal granularity is acquired by calculating temporal variance feature and it is used to replace original time series; Secondly, the elastic size of under comparing time series granularity allow dynamic adjustment through DTW algorithm and optimal time series corresponding granularity is obtained; Finally, DTW distance is calculated by optimal corresponding granularity model. At the same time, the early termination strategy of infimum function is introduced to improve the efficiency of FG-DTW algorithm. Experiments show that the proposed algorithm improves the running rate and accuracy effectively.

Effect of Interstitial Solutes on Precipitation Behavior of 9-12% Chromium Ferritic Steels

Xingang Tao,Chuanwei Li,Lizhan Han,Jianfeng Gu 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3

Effects of nitrogen and carbon content on precipitation behavior in two 9-12% Cr ferritic heat-resistant steels during isothermal transformation were investigated. Isothermal aging treatments at 700 °C after solution annealing were carried out for the different periods up to over 220 h. Microstructure characterization was performed by many characterization methods, such as physicochemical phase analysis, X-ray diffraction and scanning electron microscope etc. It was found that Cr-rich M2N nitride was formed as the main precipitate in the alloy A with content of 0.15% N and 0.03% C in wt%, together with some Cr-rich M23C6 carbide and Nb-rich MN nitride. Comparatively, the aged alloy B with 0.05% N and 0.11% C, predominantly contains Cr-rich M23C6 carbides. Besides, both alloys showed the similar microstructure evolution process: The precipitates were found to be formed initially along prior austenite grain boundaries, then grew toward interior of grain in the form of cell with the increasing aging time. Meanwhile, the cell growth feature was also discussed based on the experimental observation in well-controlled specimens.

Novel Passive Snubber Suitable for Three-Phase Single-Stage PFC Based on an Isolated Full-Bridge Boost Topology

Meng, Tao,Ben, Hongqi,Wang, Daqing,Song, Jianfeng The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3

In this paper a novel passive snubber is proposed, which can suppress the voltage spike across the bridge leg of the isolated full-bridge boost topology. The snubber is composed of capacitors, inductors and diodes. Two capacitors connected in series are used to absorb the voltage spike and the energy of each capacitor can be transferred to the load during one switching cycle by the resonance of the inductors and capacitors. The operational principle of the passive snubber is analyzed in detail based on a three-phase power factor correction (PFC) converter, and the design considerations of both the converter and the snubber are given. Finally, a 3kW laboratory-made prototype is built. The experimental results verify the theoretical analysis and evaluations. They also prove the validity and feasibility of the proposed methods.