检索结果-南通市图书馆

Effects of Nb on microstructure and wear resistance of Fe-Cr-C-B surfacing alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2018年第2期25卷 243-251页

作者： Jian Gou zheng-jun Liu hua Jia Department of Material Science and Engineering ShenyangUniversity of Technology Shenyang 110870 LiaoningChina

The influence of Nb on the microstructure and wear resistance of the surfacing layer was investigated by using the Fe-based flux-cored wire in the Fe-Cr-C-B system. The microstructure, microhardness and wear resistance properties of the samples were investigated by X-ray diffraction, scanning electron microscopy, microhardness testing and abrasive wear testing, respectively. The results indicate that microstructures of the alloy are composed of martensite, retained austenite, M23（C,B）6 and NbC. Boride M23（C,B）6 is distributed along the grain boundaries, while NbC in shape-regular quadrilateral is distributed in martensite. The microhardness is distributed from the substrate to the surfacing layer gradiently. NbC significantly improved the wear resistance of surfacing layer.

关键词： Flux-cored wire Surfacing layer Microhardness Microstructure Wear resistance

Grasping Force Planning and Control for Tendon-driven Anthropomorphic Prosthetic Hands

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2018年第5期15卷 795-804页

作者： hua Deng huanxin luo Rong Wang Yi Zhang State Key Laboratory of High-Performance Complex Manufacturing Central South University Changsha 410083 China School of Mechanical and Electrical Engineering Central South University Changsha 410083 China College of Mechanical & Electrical Engineering Changsha University Changsha 410022 China

A force planning and control method is proposed for a tendon-driven anthropomorphic prosthetic hand. It is necessary to consider grasping stability for the anthropomorphic prosthetic hand with multi degrees of freedom which aims to mimic human hands with dexterity and stability. The excellent grasping performance of the anthropomorphic prosthetic hand mainly depends on the accurate computation of the space position of finger tips and an appropriate grasping force planning strategy. After the dynamics model of the tendon-driven anthropomorphic prosthetic hand is built, the space positions of the finger tips are calculated in real time by solving the dynamic equations based on the Newton iteration algorithm with sufficient accuracy. Then, the balance of internal grasping force on the thumb is adopted instead of force closure of the grasped objects to plan the grasping forces of other fingers based on the method of the linear constraint gradient flow in real time. Finally, a fuzzy logic controller is used to control the grasping force of the prosthetic hand. The proposed force planning and control method is implemented on the tendon-driven anthropomorphic prosthetic hand and the experimental results dem- onstrate the feasibility and effectiveness of the proposed method.

关键词： prosthetic hands tendon-driven grasping force planning grasping force control

Influence of Alignment Errors on Contact Pressure during Straight Bevel Gear Meshing Process

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2015年第6期28卷 1089-1099页

作者： HAN Xinghui hua Lin DENG Song luo Qiuping Hubei Key Laboratory of Advanced Technology for Automotive Components School of Automotive EngineeringWuhan University of Technology

Straight bevel gears are widely applied in automotive, aerospace, chemical and many other fields as one of the most common type of gears. Currently, the researches on straight bevel gears have focused on the fields of fatigue, wear, noise and vibration, while little attention is paid to the effect of multiple alignment errors on the gear tooth wear. To study the influence of alignment errors on the gear tooth wear, a simulated model of a straight bevel gear pair is established. Then, the contact pressure on the tooth surface is analyzed under the various alignment errors according to the Archard wear relationship. The main combinations of alignment errors played vital roles on the tooth wear are investigated. The result shows that under the single alignment error, the contact pressure moves to the tooth heel and increases greatly at here when ？P=0.1 or ？G=0.1; when ？E=–0.03, the contact pressure greatly increases at the tooth heel, but it obviously increases at the tooth toe when ？E=0.03; the alignment error ？γ=1 has little effect on the contact pressure on the tooth surface. Moreover, the combination of ？P, ？G, ？E〈0 and ？γ is the most dangerous type among the multiple alignment errors. This research provides valuable guidelines for predicting the tooth wear under various alignment errors.

关键词： straight bevel gear multiple alignment errors contact pressure wear

A framework of region-based dynamic image fusion

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第1期8卷 56-62页

作者： WANG Zhong-hua QIN zheng LIU Yu Department of Computer Science and Technology Tsinghua University Beijing 100084 China

A new framework of region-based dynamic image fusion is proposed. First, the technique of target detection is applied to dynamic images (image sequences) to segment images into different targets and background regions. Then different fusion rules are employed in different regions so that the target information is preserved as much as possible. In addition, steerable non-separable wavelet frame transform is used in the process of multi-resolution analysis, so the system achieves favorable characters of orientation and invariant shift. Compared with other image fusion methods, experimental results showed that the proposed method has better capabilities of target recognition and preserves clear background information.

关键词： Dynamic image fusion Region segmentation Non-separable wavelet frame

Mixing times in single and multi-orifice-impinging transverse(MOIT) jet mixers with crossflow

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2016年第7期24卷 825-831页

作者： Peicheng luo Yuncui Tai Yi Fang hua Wu School of Chemistry & Chemical Engineering Southeast University Nanjing 211189 China Institute for Chemical and Bioengineering Department of Chemistry and Applied Bioscience ETH Zurich 8093 Zurich Switzerland

We study the macromixing behavior of single and multi-orifice-impinging transverse(MOIT) jet mixers with crossflow, in particular, the overall mixing time and the back-splash mixing time of the injected flow with the crossflow, using the PLIF technique. It is found that for a given mixer configuration, there is a critical jet-tocrossflow velocity ratio rcat which the back-splash begins to occur. Further increase in the velocity ratio r leads to sharp increase in the back-splash mixing time, which can offset the intensification of the downstream mixing. The dimensionless overall mixing time decreases as r increases to reach either a plateau or a local minimum, and the corresponding r value represents the optimal velocity ratio roptfor the macromixing. The momentum ratio of the two liquid streams is a key factor determining rcand ropt. For a larger scale mixer, a higher momentum ratio is required to achieve the optimal macromixing with the minimum dimensionless overall mixing time.

关键词： MixingChemical reactorsMixing timeJet mixerPlanar laser induced fluorescence (PLIF)

Spatiotemporal Prediction of Urban Traffics Based on Deep GNN

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第1期78卷 265-282页

作者： Ming luo Huili Dou Ning zheng School of Computer Science Hangzhou Dianzi UniversityHangzhou310018China Zhejiang Institute of Communications Hangzhou310012China School of Cyberspace Security Hangzhou Dianzi UniversityHangzhou310018China

Traffic prediction already plays a significant role in applications like traffic planning and urban management,but it is still difficult to capture the highly non-linear and complicated spatiotemporal correlations of traffic *** well as to fulfil both long-termand short-termprediction objectives,a better representation of the temporal dependency and global spatial correlation of traffic data is *** order to do this,the Spatiotemporal Graph Neural Network(S-GNN)is proposed in this research as amethod for traffic *** S-GNN simultaneously accepts various traffic data as inputs and investigates the non-linear correlations between the *** terms of modelling,the road network is initially represented as a spatiotemporal directed graph,with the features of the samples at the time step being captured by a convolution *** order to assign varying attention weights to various adjacent area nodes of the target node,the adjacent areas information of nodes in the road network is then aggregated using a graph *** data is output using a fully connected layer at the *** findings show that S-GNN can improve short-and long-term traffic prediction accuracy to a greater extent;in comparison to the control model,the RMSE of S-GNN is reduced by about 0.571 to 9.288 and the MAE(Mean Absolute Error)by about 0.314 to *** experimental results on two real datasets,Pe MSD7(M)and PEMS-BAY,also support this claim.

关键词： Urban traffic traffic temporal correlation GNN prediction

Impact of Improving Design Factor over 0.72 on the Safety and Reliability of Gas Pipelines and Feasibility Justification

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第1期25卷 166-172页

作者： ZHAO Xinwei ZHANG Guangli luo Jinheng ZHANG hua Tubular Goods Research Institute of China National Petroleum Corporation Xi’an 710065China Petroleumtubular engineering Key Laboratory of China National Petroleum Corporation Xi’an 710065China

Many years experience of the operation of high stress (>72% specified minimum yield strength, SMYS) gas pipelines and statistical analysis results of pipeline incidents showed that the operating pipelines at stress levels over 72% SMYS have not presented problems in USA and Canada, and design factor does not control incidents or the safety of pipelines. Enhancing pipeline safety management level is most important for decreasing incident rate. The application history of higher design factors in the U.S and Canada was reviewed. And the effect of higher factors to the critical flaw size, puncture resistance, change of reliability with time, risk level and the arrest toughness requirements of pipeline were analyzed here. The comparison of pipeline failure rates and risk levels between two design factors (0.72 and 0.8) has shown that a change in design factor from 0.72 to 0.8 would bring little effect on failure rates and risk levels. On the basis of the analysis result, the application feasibility of design factor of 0.8 in China was discussed and the related suggestions were proposed. When an operator wishes to apply design factor 0.8 to gas pipeline, the following process is recommended: stress level of line pipe hydro test should be up to 100% SMYS, reliability and risk assessment at the design feasibility or conceptual stage should be conducted, Charpy impact energy should meet the need of pipeline crack arrest; and establish and execute risk based integrity management plan. The technology of pipeline steel metallurgy, line pipe fabrication and pipeline construction, and line pipe quality control level in China achieved tremendous progresses, and line pipe product standards and property indexes have come up to international advanced level. Furthermore, pipeline safety management has improved greatly in China. Consequently, the research for the feasibility of application of design factor of 0.8 in China has fundamental basis.

关键词： gas pipeline higher design factor safety and reliability risk integrity management

A molecular dynamics investigation of the deformation mechanism and shape memory effect of epoxy shape memory polymers

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2016年第3期59卷 89-95页

作者： hua Yang zheng Dao Wang Ya Fang Guo Xing hua Shi Institute of Engineering Mechanics Beijing Jiaotong University State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences

Following deformation, thermally induced shape memory polymers(SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behaviors of three types of epoxy SMPs with varying curing agent contents were investigated using a molecular dynamics(MD) method. The mechanical properties under uniaxial tension at different temperatures were obtained, and the simulation results compared reasonably with experimental data. In addition, in a thermomechanical cycle, ideal shape memory effects for the three types of SMPs were revealed through the shape frozen and shape recovery responses at low and high temperatures, respectively, indicating that the recovery time is strongly influenced by the ratio of E-51 to 4,4'-Methylenedianiline.

关键词： shape memory polymer molecular dynamics simulation thermomechanics

A New Type of Absorbance Sensors Based on Long-Period Fiber Gratings

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2011年第5期28卷 128-131页

作者： luo Tao GU zheng-Tian Laboratory of Photo-electric Functional Films College of ScienceUniversity of Shanghai for Science and TechnologyShanghai 200093

A new absorbance sensor based on long-period fiber gratings(LPFGs)is presented,The measurand is coated on the cladding of the *** is found that the depth of the stop band of the LPFG spectrum will be strongly affected by the absorbance of the measurand if an optimum coating thickness is *** analysis showsthat within the optimal thickness range,the cladding modes could transform into the overlay modes and interact with the measurand more *** absorbance sensitivity of 7×10^(3)is available when the sensor structure is optimized.

关键词： fiber cladding optimum