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A coupled model of grain growth and solute transfer in molten pool of nickel-based alloy

China Welding 2009年第4期18卷 15-20页

作者：魏艳红马瑞占小红董志波王勇 State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001. School of Material Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016. Shanghai Xin Li Institute of Power Equipment Shanghai 201109.

A coupled model of grain growth and solute transfer based on cellular automaton （ CA ） method was established and applied to grain growth simulation in molten pool of nickel-based alloy. The CA method was used to simulate welding solidification process successfully, but few researches had taken the effect of convection on dendrite morphology into account. In this paper, solute transfer model was used to calculate the effect of convection and diffusion on solute field with CA method simulating grain growth. The results indicate that convection has a significant effect on the morphology of equiaxed grain. Dendrite growth in the upstream direction is amplified, while it is inhibited in the downstream direction. With inlet velocity increasing, this effect becomes more severe.

关键词： grain growth convection cellular automaton

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Numerical simulation of the transient multiphase field during plasma deposition manufacturing composite materials

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Science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 508-517页

作者： KONG FanRong1,2,ZHANG HaiOu1 & WANG GuiLan3 1 state key laboratory of Digital Manufacturing equipment and technology,Huazhong University of Science and technology,Wuhan 430074,China 2 Research Center for advanced Manufacturing,Southern Methodist University,3101 Dyer Street,Dallas,Texas 75205,USA 3 College of Material Science and Engineering,Huazhong University of Science and technology,Wuhan 430074,China 1. State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China 2. Research Center for Advanced Manufacturing Southern Methodist University 3101 Dyer Street Dallas Texas 75205 USA 3. College of Material Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

A solid/liquid/gas unified model has been developed to investigate the gradient composition formation during the plasma deposition manufacturing(PDM) composite materials process. In this model,an enthalpy porosity model was applied to deal with the melting and solidification of the deposited layer,and a level-set approach was introduced to track the evolution of the free surface of the molten pool and the deposited layer. Moreover,complicated physical phenomena occurring at the liquid/gas interface,including forced convection heat loss,heat emission and plasma heat source,have been incorporated into the governing equations by source terms. In this study,the numerical experiment of nickel base alloy powder deposited on the medium steel substrate by PDM technique was implemented based on the staggered grid and SIMPLEC algorithm. Concentration gradient distribution of the solute material at the composite material interface,fluid flow and temperature distribution in the molten pool and the deposited layer have been investigated in detail.

关键词： plasma deposition manufacturing composite material solid/liquid/gas unified model level-set approach

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Numerical investigation of post buckling strength and failure modes in advanced grid stiffened structure under thermal-mechanical loads

Numerical investigation of post buckling strength and failur...

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作者： Bai, Ruixiang Bo, Chen Cheng, Yan Lin, Ye Zecheng, Li Chen, Haoran State Key Laboratory of Structural Analysis of Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian 116024 China Centre for Advanced Materials Technology School of Aerospace Mechanical and Mechatronic Engineering University of Sydney NSW 2006 Australia

This work investigated the post buckling strength and failure behavior of advanced grid stiffened structures (AGS) under thermal-mechanical load using a finite element method. Based on the first order shear deformation theory (FSDT), Von Karman non-linear deformation assumption, and a progressive failure criterion, the buckling, large deformation, local failure modes in the AGS were studied. The thermal effect was also analyzed. By some numerical examples, the failure characteristics of the AGS were discussed.

关键词： Structures (built objects)

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Heat Treat ment of Die and Mould Oriented Concurrent Design

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Journal of Iron and Steel Research International 2006年第1期13卷 40-43,74页

作者： LI Xiong ZHANG Hong bing RUAN Xue-yu LUO Zhong-hua ZHANG Yan Department of Plasticity Forming Engineering Shanghai Jiaotong University Shanghai 200030 China Department of Materials Engineering Shanghai Institute of Technology Shanghai 200235 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beiiing Beijing 100083 China

Many disadvantages exist in the traditional die design method which belongs to serial pattern. It is well known that heat treatment is highly important to the dies. A new idea of concurrent design for heat treatment process of die and mould was developed in order to overcome the existent shortcomings of heat treatment process. Heat treatment CAD/CAE was integrated with concurrent circumstance and the relevant model was built. These investigations can remarkably improve efficiency, reduce cost and ensure quality of R and D for products.

关键词： die design heat treatment mould

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Mechanical properties of welded joints in vertical-up variable polarity plasma arc welding of 2219 aluminum alloy

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中国有色金属学会会刊：英文版 2005年第S2期15卷 83-86页

作者：杨春利郭立杰林三宝沈鸿源 State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China School of Materials Science and Engineering Shanghai Jiaotong University Shanghai 200030 China Shanghai Aerospace Equipment Manufacturing Corporation Shanghai 200245 China

The mechanical properties of the 2219 aluminum alloy welded joints by vertical-up variant polarity plasma arc welding (VPPAW) with keyhole were analyzed. The tensile strength of welded joints can reach 55% of that of base metal. The microstructure of weld joints was studied to explain the mechanical properties of the weld. The results show that the intensity of weld center is less than that of HAZ, and the intensity of weld center is the worst. So an advanced welding procedures is presented to reduce the heat input and increase the welding speed. The results in this procedures show that the tensile strength of welded joints reaches more than 60% of that of the parent metal, and the specific elongation does not descend.

关键词： 2219 aluminum alloy variable polarity plasma arc welding mechanical property microstructure

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Analog-experiment analysis of ash-deposition monitoring model of boiler economizers in power plants

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Journal of Harbin Institute of technology(New Series) 2005年第6期12卷 680-683页

作者：程伟良夏国栋徐寿臣 Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education North China Electric Power University Beijing 102206 China School of Environment and Energy Engineering Beijing University of Technology Beijing 100022 China Advanced Training Center State Grid Beijing 100085 China

Ash deposition is a form of particulate fouling, and appears usually in boiler economizers. The ash deposition increases capital expenditure, energy input and maintenance costs. An analog experiment for monitoring ash deposition was performed from the analogous objective of a 410 t/h boiler economizer to verify the rationality and reliability of the ash-deposition-monitoring model presented in order to increase the security and economy in economizer running. The analog experiment platform is a tube-shell exchanger that conforms well to the conditions of a self-modeling area. The analog flue gas in the shell side is the heated air mixed with ash, and in the tube side the fluid is water heated by the flue gas. The fluid state in the water side and the flue gas side follows the second self-modeling area. A 4-factor-3-level orthogonal table was used to schedule 9 operation conditions of orthogonal experiment, with the 4 factors being heat power, flue gas velocity, ashes grain diameter and adding ashes quantity while the three levels are different values due to different position classes in every factor. The ash deposition thermal resistances is calculated by the model with the measure parameters of temperature and pressure drop. It shows that the values of the ash deposition thermal resistances gradually increase up to a stable state. And the experimental results are reliable by F testing method at α= 0.001. Therefore, the model can be applied in online monitoring of ash deposition in a boiler economizers in power plants and provides scientific decision on ash deposition prediction and sootblowing.

关键词： thermal power engineering monitoring model ash deposition orthogonal experiment boiler economizer tube-shell exchanger

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Mechanical properties of welded joints in vertical-up variable polarity plasma arc welding of 2219 aluminum alloy

Mechanical properties of welded joints in vertical-up variab...

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作者： Yang, Chun-Li GuoL, Li-Jie Lin, San-Bao Shen, Hong-Yuan State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China School of Materials Science and Engineering Shanghai Jiaotong University Shanghai 200030 China Shanghai Aerospace Equipment Manufacturing Corporation Shanghai 200245 China

关键词： Microstructure

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The Finite Element Analysis in Measurement System of Airplane Fuel Mass

The Finite Element Analysis in Measurement System of Airplan...

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2011 2nd Asia-Pacific Conference on Wearable Computing Systems (APWCS 2011);2011 International Conference on Intelligent Control and Information technology (ICICIT 2011)

作者： SUI Xiuwu QI Xiaoguang LI Dapeng ZHANG Guoxiong FAN Yuming Tianjin Key Laboratory of Advanced Mechantronics Equipment Technology School of Machinery and Electron Tianjin Polytechnic University State Key Lab of Precision Measuring Technology&Instrument Tianjin University

The paper presents the measurement system of the air plane fuel mass consisting of cylinder shell resonating density meter and double cylinders capacitance level meter. The finite element analysis met

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Distributed Computation Offloading and Power Control for UAV-Enabled Internet of Medical Things

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ACM Transactions on Internet technology 1000年

作者： Jiakun Gao Xiaolong Xu Lianyong Qi Wanchun Dou Xiaoyu Xia Xiaokang Zhou School of Software Nanjing University of Information Science and Technology NanJing China School of Software Nanjing University of Information Science and Technology NanJing China and Jiangsu Province Engineering Research Center of Advanced Computing and Intelligent Services Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET) Nanjing University of Information Science and Technology Nanjing China College of Computer Science and Technology China University of Petroleum (East China) QingDao China and State Key Laboratory for Novel Software Technology Nanjing University Nanjing China State Key Laboratory for Novel Software Technology Nanjing University Nanjing China School of Computer Technology RMIT University Victoria Australia Faculty of Data Science Shiga University Hikone Japan

The advancement of the Internet of Medical Things (IoMT) has led to the emergence of various health and emotion care services, e.g., health monitoring. To cater to increasing computational requirements of IoMT services, Mobile Edge Computing (MEC) has emerged as an indispensable technology in smart health. Benefiting from the cost-effectiveness of deployment, unmanned aerial vehicles (UAVs) equipped with MEC servers in Non-Orthogonal Multiple Access (NOMA) have emerged as a promising solution for providing smart health services in proximity to medical devices (MDs). However, the escalating number of MDs and the limited availability of communication resources of UAVs give rise to a significant increase in transmission latency. Moreover, due to the limited communication range of UAVs, the geographically-distributed MDs lead to workload imbalance of UAVs, which deteriorates the service response delay. To this end, this paper proposes a UAV-enabled Distributed computation Offloading and Power control method with Multi-Agent, named DOPMA, for NOMA-based IoMT environment. Specifically, this paper introduces computation and transmission queue models to analyze the dynamic characteristics of task execution latency and energy consumption. Moreover, a credit assignment scheme-based reward function is designed considering both system-level rewards and rewards tailored to each MD, and an improved multi-agent deep deterministic policy gradient algorithm is developed to derive offloading and power control decisions independently. Extensive simulations demonstrate that the proposed method outperforms existing schemes, achieving \(7.1\%\) reduction in energy consumption and \(16\%\) decrease in average delay.

关键词： Internet of Medical Things (IoMT) Mobile Edge Computing (MEC) Unmanned Aerial Vehicles (UAV) Non-Orthogonal Multiple Access (NOMA)

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