检索结果-南通市图书馆

Promoting the mechanical properties of Ti42Al9V0.3Y alloy by hot extrusion in the α+β phase region

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) 2010年第10期11卷 738-743页

作者： Wen-chen xu Hao ZHANG De-bin shan Department of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

Hot extrusion was conducted in the α+β phase region for promoting mechanical properties of Ti42Al9V0.3Y. The microstructures and tensile properties before and after hot extrusion were studied. The results show that the microstructure of the as-cast alloy mainly consists of massive γ phase in β matrix and the as-extruded alloy mainly consists of lamellar α2/γ, lamellar β/γ, and strip γ propagating from elongated β phase. In the as-cast alloy, the predominantly observed fracture mode is transgranular cleavage failure at room temperature and intergranular fracture at 650-750 °C. After hot extrusion, it transforms into transgranular cleavage-like failure, including translamellar cleavage and delamination. The excellent tensile properties of the as-extruded material are attributed to the obvious refined microstructure with broken YAl2 particles and the micro-crack shielding action of the TiAl lamellasome.

关键词： TiAl alloy Microstructure Mechanical property Hot extrusion

A correction of the 2D KdV equation of Djordjevic & Redekopp in exponentially stratified fluid

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2005年第4期21卷 346-352页

作者： Zhaoting xu Guojin Shen Samuel shan-pu Shen Institute Of Physical Oceanography and Physical Oceanography Laboratory Ocean University of China Qingdao 266003 China Department of Mathematics and Statistics Science University of Alberta Edmonton Alberta T6G 2G 1 Canada

To further study the nal solitons on the continental fission laws of initial intershelf/slope, we rederive and correct the 2D KdV equation of Djordjevic ＆ Redekopp for exponentially stratified fluid （or ocean） and with twodimensional topography. Through a combination of theoretical study and numerical experiments, we show that solitons in the odd vertical modes can fission. However, because of the corrections, the fission conditions are different from those of Djordjevic ＆ Redekopp. The even modes cannot fission unless the initial internal solitons propagate from shallow sea to deep sea. This conclusion is entirely opposite to that of Djordjevic ＆ Redekopp.

关键词： Internal wave Soliton Fission 2D KdV equation

Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2018年第2期31卷 106-114页

作者： Bing Yuan shan chang Geng Liu Li-Yan Wu Shaanxi Engineering Laboratory for Transmissions and Controls School of Mechanical Engineering Northwestern Polytechnical University China Shipbuilding Industry Corporation 703 Institute

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

关键词： Manufacturing error Mesh stiffness Transmission error Loaded composite mesh error Vibration acceleration Sideband frequency

Pyrrole/macrocycle/MOF supramolecular co-assembly for flexible solid state supercapacitors

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2021年第9期32卷 2773-2776页

作者： shan-shan Jia Wen-Shi xu Yong Chen Yu Liu College of Chemistry State Key Laboratory of Elemento-Organic ChemistryNankai UniversityTianjin 300071China

Supramolecular assemblies constructed through the encapsulation of conductive polymers(CPs)by macrocyclic molecules have attracted increasing interest in the fields of supramolecular chemistry and *** this work,an effective strategy was reported to improve the stability and conductivity of CPs by electrochemically constructing different supramolecular assemblies composed of macrocycles and ***,we uploaded zinc-based MOF(ZIF-8)onto carbon nanotube film(CNTF)and further electrically deposited macrocycles and CPs to gain the flexible conductive ***,five different supramolecular macrocycles,includingα-cyclodextrin(α-CD),sulfato-β-cyclodextrin(SCD),sulfonatocalix[4]arene(SC[4]),cucurbit[6]uril(CB[6])and cucurbit[7]uril(CB[7])were utilized and the electrochemical performances of the assembly electrodes increased in an order ofα-CD

关键词： Supramolecular assemblies Macrocycle Conductive polymers Electrochemical performance Cationic radical

Tuning d-spacing of graphene oxide nanofiltration membrane for effective dye/salt separation

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2023年第2期42卷 418-429页

作者： Chao Xing chang-Yu Liu Chao Lai shan-Qing Zhang Center for Clean Environment and Energy School of Environment and ScienceGold Coast CampusGriffith UniversitySouthportQLD4222Australia School of Chemistry and Materials Science Jiangsu Normal UniversityXuzhou221116China School of Biotechnology and Health Sciences Wuyi UniversityJiangmen529020China

The interlayer spacing(i.e.,d-spacing)plays a crucial role in determining the selectivity and permeability of nanofiltration membranes.A high-throughput directional filtration can be achieved by designing and controlling the *** this study,the d-spacing of a graphene oxide(GO)membrane was tuned and fixed to the desired value(approximately 0.79 nm)using a solution of polyethyleneimine(PEI)and GO at a PEI/GO mass ratio of15:*** resultant PEI/GO was deposited on a polyacrylonitrile(PAN)substrate to form a robust composite nanofiltration membrane(a PEI/GO@PAN membrane).The as-prepared membrane exhibited an ultrahigh flux of117.8 L·m^(-2)·h^(-1),and the rejection values for Direct Red80(DR80)and Na_(2)SO_(4)reached 99.7%and<1.7%,respectively;these are desirable values for dye/salt *** PEI/GO@PAN membrane exhibited an excellent filtration performance,and had a longer lifespan and excellent reusability because of its reinforced *** work suggested that tuning the d-spacing with PEI would be an effective strategy to achieve the anticipated functions of nanofiltration membranes.

关键词： Separation Nanofiltration Graphene oxide Membrane d-spacing

Influence of NO_(x) on the activity of Pd/θ-Al_(2)O_(3) catalyst for methane oxidation: Alleviation of transient deactivation

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2022年第2期34卷 38-47页

作者： chang Cui Yan Zhang Wenpo shan Yunbo Yu Hong He State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China Center for Excellence in Regional Atmospheric Environment and Key Laboratory of Urban Pollutant Conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Ningbo Research Center for Urban Environment Chinese Academy of SciencesNingbo 315800China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou 341000China

Alumina supported Pd catalyst(Pd/Al_(2)O_(3)) is active for complete oxidation of methane, while often suffers transient deactivation during the cold down process. Herein, heating and cooling cycle tests between 200 and 900 ℃ and isothermal experiments at 650 ℃ were conducted to investigate the influence of NO_(x) on transient deactivation of Pd/θ-Al_(2)O_(3) catalyst during the methane oxidation. It was found that the co-fed of NO alleviated transient deactivation in the cooling ramp from 800 to 500 ℃, which was resulted from the in situ formation of NO_(2) during the process of methane oxidation. Over the Pd/θ-Al_(2)O_(3), thermogravimetric analysis and O_(2) temperature programmed oxidation measurements confirmed that transient deactivation was due to the decomposition of Pd O particles and the hysteresis of Pd reoxidation, while the metal Pd entities were less active for methane oxidation than the Pd O ones. CO pulse chemisorption and scanning transmission electron microscopy characterizations rule out the NO_(2) effect on Pd size change. Powder X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to obtain palladium status of Pd/θ-Al_(2)O_(3) before and after reactions, indicating that in lean conditions at 650 ℃, the presence of NO_(2) increases the content of active Pd O on the catalyst surface, thus benefits methane oxidation. Homogeneous reaction between CH 4, O_(2), and NO_(x) may be partially responsible for the alleviation above 650 ℃. The interesting research of alleviation in transient deactivation by NO_(x), the components co-existing in exhausts, are of great significance for the application.

关键词： Methane Catalytic oxidation Palladium NO_(x)influence

Extending generalized unsupervised manifold alignment

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2022年第7期65卷 139-156页

作者： Xiaoyi YIN Zhen CUI Hong chang Bingpeng MA Shiguang shan Key Laboratory of Intelligent Information Processing of Chinese Academy of Sciences (CAS) Institute of Computing Technology Chinese Academy of Sciences CAS Center for Excellence in Brain Science and Intelligence Technology School of Computer Science and Engineering Nanjing University of Science and Technology University of Chinese Academy of Sciences

Building connections between different data sets is a fundamental task in machine learning and related application community. With proper manifold alignment, the correspondences between data sets will assist us with comprehensive study of data processes and analyses. Despite the several progresses in semi-supervised and unsupervised scenarios, potent manifold alignment methods in generalized and realistic circumstances remain in absence. Besides, theretofore unsupervised algorithms seldom prove themselves mathematically. In this paper, we devise an efficient method to properly solve the unsupervised manifold alignment problem and denominate it as extending generalized unsupervised manifold alignment(EGUMA)method. More specifically, an explicit relaxed integer programming method is adopted to solve the unsupervised manifold alignment problem, which reconciles three factors covering the updated local structure matching, the the feature comparability and geometric preservation. An additional effort is retained on extending the Frank Wolfe algorithm to tacking our optimization problem. Besides our previous endeavors we adopt a new strategy for neighborhood discovery in the manifolds. The main advantages over previous methods accommodate(1) simultaneous alignment and discovery of manifolds;(2) complete unsupervised learning structure without any prerequisite correspondence;(3) more concise local geometry for the embedding space;(4) efficient alternative optimization;(5) strict mathematical analysis on the convergence and efficiency issues. Experiments on real-world applications verify the high accuracy and efficiency of our proposed method.

关键词： unsupervised manifold alignment relaxed integer programming Frank Wolfe algorithm

同方期刊数据库

A non-myopic scheduling method of radar sensors for maneuvering target tracking and radiation control

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2020年第1期16卷 242-250页

作者： Gan-lin shan Gong-guo xu Cheng-lin Qiao Department of Electronic and Optical Engineering Army Engineering UniversityShijiazhuang 050003China

In decades,the battlefield environment is becoming more and more complex with plenty of electronic ***,in order to improve the survivability of radar sensors and satisfy the requirement of maneuvering target tracking with a low probability of intercept,a non-myopic scheduling is proposed to minimize the radiation cost with tracking accuracy *** first,the scheduling problem is formulated as a partially observable Markov decision process(POMDP).Then the tracking accuracy and radiation cost over the future finite time horizon are predicted by the posterior carmer-rao lower bound(PCRLB) and the hidden Markov model filter,***,the proposed scheduling is implemented efficiently by utilizing the branch and bound(B&B) pruning *** results show that the performance of maneuvering target tracking was improved by the improved interacting multiple model(IMM),and the scheduler time and maximum memory consumption were significant reduced by the present B&B pruning algorithm without losing the optimal solution.

关键词： Non-myopic scheduling Radiation control PCRLB POMDP Branch and bound

A Series of Variable Separation Solutions and New Soliton Structures of （2＋1）-Dimensional Korteweg-de Vries Equation

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2006年第3X期46卷 403-406页

作者： xu chang-Zhi Department of Physics Jinhua Education College Jinhua 321000 China

Variable separation approach is introduced to solve the （2＋1）-dimensional KdV equation. A series of variable separation solutions is derived with arbitrary functions in system. We present a new soliton excitation model （24）. Based on this excitation, new soliton structures such as the multi-lump soliton and periodic soliton are revealed by selecting the arbitrary function appropriately.

关键词： variable separation approach (2+1)-dimensional KdV equation new soliton excitation