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Bio-Inspired Controller for a Robot Cheetah with a Neural Mechanism Controlling Leg Muscles

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Journal of Bionic Engineering 2012年第3期9卷 282-293页

作者： Xin wang Mantian Li pengfei wang Wei Guo Lining Sun State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001P.R.China

The realization of a high-speed running robot is one of the most challenging problems in developing legged robots. The excellent performance of cheetahs provides inspiration for the control and mechanical design of such robots. This paper presents a three-dimensional model of a cheetah that predicts the locomotory behaviors of a running cheetah. Applying biological knowledge of the neural mechanism, we control the muscle flexion and extension during the stance phase, and control the positions of the joints in the flight phase via a PD controller to minimize complexity. The proposed control strategy is shown to achieve similar locomotion of a real cheetah. The simulation realizes good biological properties, such as the leg retraction, ground reaction force, and spring-like leg behavior. The stable bounding results show the promise of the controller in high-speed locomotion. The model can reach 2.7 m-s^-1 as the highest speed, and can accelerate from 0 to 1.5 m-s^-1 in one stride cycle. A mechanical structure based on this simulation is designed to demonstrate the control approach, and the most recently developed hindlimb controlled by the proposed controller is presented in swinging-leg experiments and jump-force experiments.

关键词： biomimetics biologically-inspired robots legged robots neural mechanism artificial pneumatic muscle

DFTracker: detecting double-fetch bugs by multi-taint parallel tracking

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Frontiers of Computer Science 2019年第2期13卷 247-263页

作者： pengfei wang Kai LU Gen LI Xu ZHOU Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha 410073 China College of Computer National University of Defense Technology Changsha 410073 China Collaborative Innovation Center of High Performance Computing National University of Defense Technology Changsha 410073 China

A race condition is a common trigger for concurrency bugs. As a special case, a race condition can also occur across the kernel and user space causing a doublefetch bug, which is a field that has received little research attention. In our work, we first analyzed real-world doublefetch bug cases and extracted two specific patterns for doublefetch bugs. Based on these patter ns, we proposed an approach of multi-taint parallel tracking to detect double-fetch bugs. We also implemented a prototype called DFTracker (doublefetch bug tracker), and we evaluated it with our test suite. Our experiments demonstrated that it could effectively find all the double-fetch bugs in the test suite including eight realworld cases with no false negatives and minor false positives. In addition, we tested it on Linux kernel and found a new double-fetch bug. The execution overhead is approximately 2x for single-file cases and approximately 9x for the whole kernel test, which is acceptable. To the best of the authors1 knowledge, this work is the first to introduce multi-taint parallel tracking to double-fetch bug detection—an innovative method that is specific to double-fetch bug features—and has better path coverage as well as lower runtime overhead than the widely used dynamic approaches.

关键词： multi-taint parallel tracking double fetch race condition between kernel and user time of check to time of use real-world case analysis Clang Static Analyzer

Modeling Temporal Dynamics of Users' Purchase Behaviors for Next Basket Prediction

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Journal of Computer Science & Technology 2019年第6期34卷 1230-1240页

作者： pengfei wang Yongfeng Zhang Shuzi Niu Jiafeng Guo School of Computer Science Beijing University of Posts and TelecommunicationsBeijing 100876China Department of Computer Science Rutgers UniversityNew Jersey 07450U.S.A. Institute of Software Chinese Academy of SciencesBeijing 100190China Institute of Computing Technology Chinese Academy of SciencesBeijing 100190China

Next basket prediction attempts to provide sequential recommendations to users based on a sequence of the user's previous purchases. Ideally, a good prediction model should be able to explore the personalized preference of the users, as well as the sequential relations of the items. This goal of modeling becomes even more challenging when both factors are time-dependent. However, existing methods either take these two aspects as static, or only consider temporal dynamics for one of the two aspects. In this work, we propose the dynamic representation learning approach for time-dependent next basket recommendation, which jointly models the dynamic nature of user preferences and item relations. To do so, we explicitly model the transaction timestamps, as well as the dynamic representations of both users and items, so as to capture the personalized user preference on each individual item dynamically. Experiments on three real-world retail datasets show that our method significantly outperforms several state-of-the-art methods for next basket recommendation.

关键词： sequential recommendation dynamic representation next basket recommendation

Peering into the Milky Way by FAST:Ⅲ.Magnetic fields in the Galactic halo and farther spiral arms revealed by the Faraday effect of faint pulsars

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Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 39-54页

作者： Jun Xu JinLin Han pengfei wang Yi Yan National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy University of Chinese Academy of SciencesBeijing 100049China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive radio telescope for pulsar *** make polarimetric measurements of a large number of faint and distant pulsars using the *** present the new measurements of Faraday rotation for 134 faint pulsars in the Galactic *** improvements are also made for some basic pulsar parameters for 15 of *** analyse the newly determined rotation measures(RMs)for the Galactic magnetic fields by using these 134 halo pulsars,together with previously available RMs for pulsars and extragalactic radio sources and also the newly determined RMs for another 311 faint pulsars which are either newly discovered in the project of the Galactic Plane Pulsar Snapshot(GPPS)survey or previously known pulsars without *** RM tomographic analysis in the first Galactic quadrant gives roughly the same field strength of around 2μG for the large-scale toroidal halo magnetic *** scale height of the halo magnetic fields is found to be at least 2.7±0.3 *** RM differentiation of a large number of pulsars in the Galactic disk in the Galactic longitude range of 26°

关键词： magnetic fields interstellar medium pulsars

On Existence of Local Solutions for a Hyperbolic System Modelling Chemotaxis with Memory Term

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Journal of Partial Differential Equations 2021年第2期34卷 170-185页

作者： WU Shaohua wang pengfei School of Mathematics and Statistics Wuhan UniversityWuhan 430072China

In this paper,we discuss the-local existence of weak solutions for some hyperbolic parabolic systems modelling chemotaxis with memory *** main methods we use are the fixed point theorem and semigroup theory.

关键词： Hyperbolic-parabolic system KS model chemotaxis memory term

Effect of Rare Earth Element Ce on Microstructure and Properties of Aluminum Rod for Electrical Purpose

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Journal of Rare Earths 2004年第z1期22卷 218-221页

作者： Li pengfei wang Yunli Gao Xizhu wang Zaiyun Inner Mongolia University of Technology Huhhot 010062 China Baotou Aluminum Co. Ltd Baotou 014046 China Baotou Aluminum Co. Ltd Baotou 014046 China Baotou Aluminum Co. Ltd Baotou 014046 China

The effect of rare earth element Ce on microstructure, electrical conductivity and mechanical properties was *** optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffractometer, the microstructure and phase composition of aluminum rod for electrical purpose were measured and *** results indicate that rare earth element Ce can considerably refine grain size of aluminum rod for electrical purpose,improve the regular distribution pattern of the impurity, such as silicon and iron which present in the aluminum matrix,form stable metal compound with pernicious *** metal compound precipitates on the crystal *** a result, the solid solubility of impurity in aluminum reduce, and the electrical conductivity of aluminum rod for electrical purpose is *** is found that the mechanical properties of aluminum rod for electrical purpose are improved by rare earth element in certain range of RE addition.

关键词： rare earth element aluminum rod for electrical purpose electrical conductivity microstructure

Determination of optimal blowing-to-suction flow ratio in mechanized excavation face with wall-mounted swirling ventilation using numerical simulations

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International Journal of Coal Science & Technology 2021年第2期8卷 248-264页

作者： Runze Gao pengfei wang Yongjun Li Ronghua Liu School of Resource Environment&Safety EngineeringHunan University of Science&TechnologyXiangtan 411201China Work Safety Key Lab On Prevention and Control of Gas and Roof Disasters for Southern Coal Mines Hunan University of Science&TechnologyXiangtan 411201China Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines Hunan University of Science&TechnologyXiangtan 411201China

Wall-mounted swirling ventilation is a new type of system in mechanized excavation faces with a dust sup-pression performance that is closely related to the blowing-to-suction flow *** and simulation models were developed according to the No.C103 mechanized excavation face in the Nahe Coal Mine of the Baise Mining Bureau,Guangxi Province to optimize the blowing-to-suction flow ratio for wall-mounted swirling *** the k-εturbulence model and the discrete phase model were utilized to simulate airflow field structures and dust concentration distribution patterns at various blowing-to-suction flow *** results suggest that higher blowing-to-suction flow ratios increase the airflow field disturbance around the working face and weaken the intensity of the axial air *** the other hand,both the intensity of the radial air curtain and the dust suppression effect are *** a blowing-to-suction flow ratio of 0.8,the wall-mounted swirling ventilation system achieved the most favorable dust suppression *** the total dust and respirable dust had their lowest concentrations with maximum efficiencies of reducing both types at 90.33%and 87.16%,respectively.

关键词： Mechanized excavation face Wall-mounted swirling ventilation Blowing-to-suction flow ratio Airflow field Dust

Enhanced strength-ductility of CoCrFeMnNi high-entropy alloy with inverse gradient-grained structure prepared by laser surface heat-treatment technique

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Journal of Materials Science & Technology 2022年第16期111卷 111-119页

作者： Bohong Zhang Jie Chen pengfei wang Bingtao Sun Yu Cao College of Mechanical&Electrical Engineering Wenzhou UniversityWenzhou 325035China

The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface *** to the gradually decayed thermal effect along with the thickness,the grain size increases from the hard core to the soft surface in terms of the inverse gradient-grained sample,which is in good consistent with the microhardness *** hetero-deformation induced strengthening and strain hardening caused by the inverse gradient-grained structure improve the strength-ductility combination,as well as the high-order hierarchal nanotwins due to the enhanced interaction with *** the laser surface heat-treatment technique,the strength and ductility are significantly increased by enlarging the microhardness difference and decreasing the thermal *** the high volume fraction of gradient-grained layer and a great deal of high-order hierarchal nanotwins in the central region,the laser surface heat-treatment technique is a promising way to produce the gradientstructured materials without thickness limitation.

关键词： High-entropy alloy Laser surface heat-treatment Cold rolling Inverse gradient-grained structure Strength-ductility combination

Molecular dynamics simulation study of nitrogen vacancy color centers prepared by carbon ion implantation into diamond

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Nanotechnology and Precision Engineering 2024年第3期7卷 71-78页

作者： Wei Zhao Zongwei Xu pengfei wang Hanyi Chen State Key Laboratory of Precision Measuring Technology and Instruments Tianjin UniversityTianjin 300072China Department of Modern Physics University of Science and Technology of ChinaHefei 230026China

Nitrogen vacancy(NV)color centers in diamond have useful applications in quantum sensing andﬂuorescent *** can be gen-erated experimentally by ion implantation,femtosecond lasers,and chemical vapor ***,there is a lack of studies of the yield of NV color centers at the atomic *** the molecular dynamics simulations described in this paper,NV color centers are pre-pared by ion implantation in diamond with pre-doped nitrogen and subsequent *** differences between the yields of NV color centers produced by implantation of carbon(C)and nitrogen(N)ions,respectively,are *** is found that C-ion implantation gives a greater yield of NV color centers and superior location *** effects of different pre-doping concentrations(400–1500 ppm)and implantation energies(1.0–3.0 keV)on the NV color center yield are analyzed,and it is shown that a pre-doping concentra-tion of 1000 ppm with 2 keV C-ion implantation can produce a 13%yield of NV color centers after 1600 K annealing for 7.4 ***,a brief comparison of the NV color center identiﬁcation methods is presented,and it is found that the error rate of an analysis utiliz-ing the identify diamond structure coordination analysis method is reduced by about 7%compared with conventional identiﬁcation+methods.

关键词： NV color center Ion implantation Molecular dynamics(MD)simulation Yield enhancement