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Dependence on forming parameters of an integral panel during the electromagnetic incremental forming process

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Chinese Journal of Aeronautics 2018年第7期31卷 1625-1634页

作者： Jinqiang TAN Mei zhan Hongwei LI State Key Laboratory of Solidification Process School of Materials Science & Engineering Northwestern Polytechnical University

Nowadays, more and more attentions are paid to electromagnetic incremental forming（EMIF）, especially for a part with a large-scale size, e.g., an integral panel with stiffened ribs. In this work, the bending of a panel into a double-curvature profile via EMIF is carried out experimentally and evaluated by comparing the formed profile with the desired profile. During the process,discharges at four positions along different discharge paths are designed. The effects of forming parameters on the die-fittingness of the workpiece are discussed, for which two evaluation indices are used to judge forming results. The results show that a discharge voltage in an incremental mode is helpful to improve the fittingness and avoid the collision rebound against the die at the same *** at the diagonal positions with the ‘‘X＂ discharge path exhibits the minimal shape deviation and the best forming uniformity. On the contrary, discharging at the parallel positions with the ‘‘Z＂ discharge path obtains the worst forming quality. Overlap of the coil at different positions should be given during EMIF; however, a lower overlap rate of the coil helps improve the forming quality. The results obtained in this work are useful for forming integral panels with stiffened ribs via the EMIF process.

关键词： Electromagnetic incrementalforming (EMIF) Forming uniformity Integral panel Parameters Shape deviation

Virtual Reality Toolkit for the Assembly of Nanotube-based Nano-electro-mechanical Systems

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Chinese Journal of Mechanical Engineering 2011年第1期24卷 1-11页

作者： GAO zhan LECUYER Anatole zhanG Shuyou State Key Laboratory ofCAD＆CG Zhejiang University Hangzhou 310027 China School of Computer Science and Technology Nantong University Nantong 226019 China BUNRAKU Group INRIA Campus University de Beaulieu Rennes 35042 France

Nano assembly and manipulation technologies are the basis for nano-electro-mechanical systems（NEMS）. Atomic force microscope（AFM） is widely used to manipulate nanotubes to assemble NEMS. Manipulating nanotubes with AFM is a challenging and difficult task. One of the major reasons is the deficiency of visual information during the manipulation process. To address these difficulties, this research aims to put forward novel virtual tools and assembly strategies to improve the efficiency, accuracy and ease of the assembly process of NEMS. This paper begins by the discussion of the principles and implementation of a virtual nano-assembly simulator, which serves as a benchmark to test the proposed NEMS assembly techniques and virtual tools. Then, a general framework of nanotube-based NEMS assembly is proposed. Several nano-assembly strategies and virtual tools, such as automated path planning for NEMS assembly, a four-step scheme of nanotube manipulation, virtual fixtures for assembly finalization and safe manipulation, are introduced. These virtual tools and methods are experimented for justification. An assembly task of moderate complexity was performed in our virtual nano-assembly simulator with and without the help of the proposed toolkit. Experimental results suggest that the proposed methods tend to greatly enhance the efficiency and accuracy of nanotube-based NEMS assembly. In general, the proposed virtual reality toolkit not only ensures the safety, but also enhances the accuracy and efficiency of the assembly of nanotube-based NEMS.

关键词： virtual reality nano-assembly nano-electro-mechanical systems haptic feedback

Experimental studies of the formation and dissociation of methane hydrate in loess

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Journal of Natural Gas Chemistry 2010年第3期19卷 217-223页

作者： Guanli Jiang Qingbai Wu Jing zhan State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Science Lanzhou 730000 Gansu China

In order to study the nature of gas hydrate in porous media,the formation and dissociation processes of methane hydrate in loess were *** cooling rates were applied to form methane *** nucleation times of methane hydrate formation at each cooling rate were measured for *** experimental results show that cooling rate is a significant factor affecting the nucleation of methane hydrate and gas *** the same initial conditions,the faster the cooling rate,the shorter the nucleation time,and the lower the methane gas *** dissociating temperatures were applied to conduct the dissociation experiment of methane hydrate formed in *** experimental results indicated that the temperature evidently controlled the dissociation of methane hydrate in loess and the higher the dissociating temperature,the faster the dissociating rates of methane hydrate.

关键词： methane hydrate loess formation dissociation nucleation conversion gas volume percentage

Negative refraction in a rotational plasma metamaterial

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Plasma Science and Technology 2019年第1期21卷 13-18页

作者： Yemin zhan Bin GUO Department of Physics Wuhan University of Technology

The features of negative refraction are investigated by using a rotational plasma metamaterial. It is assumed that the plasma metamaterial is composed of plasma and dielectric material periodically. The analytical results show that the plasma density, plasma filling factor, and rotation angle significantly changed the properties of negative refraction. Interestingly, the plasma metamaterial without exhibiting negative refraction effect will show negative refraction when rotating the optical axis of the metamaterial, while the range of incident angle for negative refraction will be reduced or even disappear for the plasma metamaterial exhibiting negative refraction effect when rotating the optical axis. Moreover, the full-angle negative refraction can be obtained by specific rotation angle and plasma density. The effects of plasma density, plasma filling factor and the rotation angle on the properties of THE negative refraction effect are also explored and discussed in detail.

关键词： negative refraction plasma metamaterial Poynting vector rotational

Bayesian edge detector for SAR imagery using discontinuity-adaptive Markov random feld modeling

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Chinese Journal of Aeronautics 2013年第6期26卷 1534-1543页

作者： Yuan zhan He You Cai Fuqing Research Institute of Information Fusion Technology Naval Aeronautical and Astronautical University

Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge *** this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly *** the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent *** normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are *** fnal edge detection result is achieved by fusing the results of two thresholded *** experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.

关键词： Discontinuity-adaptive Markov random feld(DAMRF) Edge detection Local mean reflectivity Maximum a posteriori(MAP) estimation Synthetic aperture radar(SAR

Recent Progress on Engineering Highly Efficient Porous Semiconductor Photocatalysts Derived from Metal–Organic Frameworks

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Nano-Micro Letters 2019年第1期11卷 5-32页

作者： Wenwen zhan Liming Sun Xiguang Han Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials Department of ChemistrySchool of Chemistry and Chemical Engineering Jiangsu Normal University

Porous structures o er highly accessible surfaces and rich pores, which facilitate the exposure of numerous active sites for photocatalytic reactions, leading to excellent performances. Recently, metal–organic frameworks(MOFs) have been considered ideal precursors for well-designed semiconductors with porous structures and/or heterostructures, which have shown enhanced photocatalytic activities. In this review, we summarize the recent development of porous structures, such as metal oxides and metal sulfides, and their heterostructures, derived from MOF-based materials as catalysts for various light-driven energy-/environment-related reactions, including water splitting, CO_2 reduction, organic redox reaction, and pollution degradation. A summary and outlook section is also included.

关键词： Metal–organic frameworks Derivatives Porous structure Photocatalysis

Modified unscented particle filter for nonlinear Bayesian tracking

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Journal of Systems Engineering and Electronics 2008年第1期19卷 7-14页

作者： zhan Ronghui Xin Qin Wan Jianwei School of Electronic Science and Engineering National Univ. of Defense Technology. Changsha 410073 P. R. China

A modified unscented particle filtering scheme for nonlinear tracking is proposed, in view of the potential drawbacks （such as, particle impoverishment and numerical sensitivity in calculating the prior） of the conventional unscented particle filter （UPF） confronted in practice. Specifically, a different derivation of the importance weight is presented in detail. The proposed method can avoid the calculation of the prior and reduce the effects of the impoverishment problem caused by sampling from the proposal distribution, Simulations have been performed using two illustrative examples and results have been provided to demonstrate the validity of the modified UPF as well as its improved performance over the conventional one.

关键词： Bayesian estimation modified unscented particle filter nonlinear filtering unscented Kalman filter

Performance Improvement of NCSs Under Complex Network via Concurrent Paths

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Journal of Systems Science & Complexity 2019年第2期32卷 453-478页

作者： WANG zhan-Yu LIU Guo-Ping School of Mechanical and Electrical Engineering Harbin Institute of Technology School of Engineering University of South Wales

Different from the single paths between controllers and plants of networked control systems(NCSs), the complex network provides widespread links and brings plenty of paths from the controller side to the plant side. Benefit from this advantage, a novel data transmission dispatching strategy is proposed. When the direct path can not satisfy the condition of system demand, neither stability nor performance, some specified paths compose a concurrent-path to transmit the control signal concurrently. Firstly, the networked control systems(NCSs) are expressed by the switched systems model with the constant network-induced delay, and the network communication is described as a packet-loss process. Secondly, taking system's exponential decay rate as its performance indicator, the relationship between control signal transmission paths and system performance is quantitatively given by considering packet losses as the compound poisson process and the alternating renewal process. Then, due to that different combination of paths induces the different statistical properties of packet losses, the approach to find an appropriate concurrent-path is proposed concerning two mutually constrained factors, the system performance demand and the utilization of network resources. After the theoretical analysis, a distributed communication platform based on peer-to-peer(P2P) network technology is designed and implemented to realize the concurrent-path transmission on internet. Finally, the practical experiment on the platform demonstrates the validity and effectiveness of proposed approach.

关键词： Dispatching strategy networked control system. P2P switched system transmission platform for networked control systems

Prediction of temperature field in machined workpiece surface during the cutting of Inconel 718 coated with surface-active media

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Advances in Manufacturing 2023年第3期11卷 378-389页

作者： Qing-An Yin zhan-Qiang Liu Bing Wang School of Mechanical Engineering Shandong UniversityJinan 250061People's Republic of China Key National Demonstration Center for Experimental Mechanical Engineering Education/Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MQE Jinan 250061People's Republic of China

The heat generated and accumulated on the machined surface of an Inconel 718 workpiece causes thermal damage during the cutting ***-active media with high thermal conductivity coated on the workpiece to be machined may have the potential to reduce the generation of cutting *** this study,a theoretical model for predicting the instantaneous machined surface temperature field is proposed for surface-active thermal conductive medium(SACM)-assisted cutting based on the finite element and Fourier heat transfer *** cutting experiments were performed to verify the results predicted using the proposed surface-temperature field *** SACMs with various thermal conductivities were used to coat Inconel 718 surface to be *** embedded into the workpiece were used to measure the cutting temperature at different points on the machined workpiece surface during the cutting *** experimental results were in agreement with the predicted temperatures,and the maximum error between the experimental results and predicted temperatures was approximately 9.5%.The cutting temperature on the machined surface decreased with an increase in the thermal conductivity of the *** graphene SACM with high thermal conductivity can effectively reduce the temperature from 542℃ to 402℃,which corresponds to a reduction of approximately 26%.The temperature reduction due to SACM decreases with an increase in the distance between the temperature prediction point and machined workpiece *** conclusion,the cutting temperatures on the machined workpiece surface can be reduced by coating with SACM.

关键词： Surface-active thermal conductive media(SACM) Finite element model Cutting heat Cutting temperature Inconel 718