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Numerical simulation for the comparison of thermal and plastic material flow behavior between symmetrical and asymmetrical boundary conditions during friction stir welding

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Advances in Manufacturing 2023年第1期11卷 143-157页

作者： Hao Su Chuan-song wu MOE Key Lab for Liquid-Solid Structure Evolution and Materials Processing Institute of Materials JoiningShandong UniversityJinan250061People’s Republic of China

An accurate description of the contact condition between the tool and the workpiece material is one of the most important issues for expounding the underlying multi-physics coupled mechanism during friction stir welding(FSW)*** the present study,a novel asymmetrical boundary condition around the tool-workpiece contact interface is proposed for the FSW of AA2024-T4 alloy.A three-dimensional computational fluid dynamics model is employed for the comparison of the coupled thermal and plastic material flow behavior between asymmetrical and symmetrical boundary *** results of heat generation,temperature distribution,tunnel defect formation and material flow streamline during the welding process are quantitatively ***,various experimental measuring methods are utilized to obtain information about temperature,thermal cycle,tool torque and horizontal cross-section around the exiting *** is revealed that the modeling results of heat flux density and temperature distribution around the pin,as well as material flow characteristics all change significantly for the two models with different boundary ***,the asymmetrical boundary condition is more capable of predicting temperature fluctuation,plastic material flow along the vertical direction,as well as tunnel defect formation during ***,the superiority of the model with asymmetrical boundary condition over the symmetrical one during the numerical simulation of FSW is elucidated.

关键词： Friction stir welding(FSW) Numerical simulation Heat generation Plastic material flow Asymmetrical boundary condition

On-site conversion reaction enables ion-conducting surface on red phosphorus/carbon anode for durable and fast sodium-ion batteries

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Journal of Energy Chemistry 2023年第5期80卷 381-391,I0009页

作者： Jiangping song Xin Peng Dan Liu Hao Li Mengjun wu Kan Fang Xinxin Zhu Xinyuan xiang Haolin Tang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070HubeiChina Department of Chemistry School of ChemistryChemical Engineering and Life SciencesWuhan University of TechnologyWuhan 430070HubeiChina Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory Xianhu Hydrogen ValleyFoshan 528200.GuangdongChina

The practical applications of high-capacity alloy-type anode materials in sodium-ion batteries(SIBs)are challenged by their vast volume effects and resulting unstable electrode-electrolyte interphases during discharge-charge *** red phosphorus(P)/carbon anode material as an example,we report an on-site conversion reaction to intentionally eliminate the volume effect-dominated surface P and yield an ionically conducting layer of Na3PS4solid-state electrolyte on the *** a surface reconstruction can significantly suppress the electrode swelling and simultaneously enable the activation energy of interfacial Na+transfer as low as 36.7 k J mol^(-1),resulting in excellent electrode stability and ultrafast reaction ***,excellent cycling performance(510 mA h g^(-1)at 5 A g^(-1)after 1000 cycles with a tiny capacity fading rate of 0.016%per cycle)and outstanding rate capability(484 mA h g^(-1)at 10 A g^(-1)are achieved in half *** coupled with Na_(3)V_(2)(PO4)3cathode,the full cells exhibit 100%capacity retention over 200 cycles at 5C with an average Coulombic efficiency of 99.93%and a high energy density of 125.5 W h kg^(-1)at a power density of 8215.6 W kg^(-1)(charge or discharge within~49 s).Remarkably,the full cell can steadily operate at a high areal capacity of 1.9 mA h cm^(-2),the highest level among red P-based full SIBs ever reported.

关键词： Sodium-ion batteries Red phosphorus P_(4)S_(n) Na_(3)PS_(4) Solid electrolyte interphase

Light enhanced proton conductivity in a terbium phosphonate photochromic chain complex

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Science China Chemistry 2021年第7期64卷 1170-1176页

作者： Qian Zhang wu-Ji Wei Qi Li Jie Pan song-De Han Ji-xiang Hu Guo-Ming Wang College of Chemistry and Chemical Engineering Qingdao UniversityQingdao 266071China

Crystalline complexes that exhibited light switchable proton conductivity are of great interest but still a challenge in material ***,a terbium phosphonate chain complex was synthesized through assembly of electron-rich phosphonate units,electron-deficient polypyridine components and paramagnetic Tb^(3+)*** light irradiation and heat treatment,the photogenerated radicals could simultaneously and reversibly tune the photochromic,luminescent and magnetic *** from the abundant hydrogen bonding networks formed between PO_3 groups and lattice water molecules,proton conductive behaviour was explored with high proton conductivity of(1.74±0.19)×10^(-3)S cm^(-1)at 80°C and 100%relative ***,accompanied with the colorless sample changed to blue,the proton conductivity increased about 20%after room temperature light illumination,implying that light irradiation could act as an external stimulus to enhance the conductive properties of original *** work innovatively realized the light responsive conductive property in the electron transfer photochromic materials,providing a novel strategy for the construction of smart materials.

关键词： electron transfer H-bonding interactions light responsive proton conductivity photochromism photomagnetism

Is it universal that the layered-spinel structure can improve electrochemical performance?

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Journal of Energy Chemistry 2022年第1期31卷 344-353,I0010页

作者： Daqiang Wang Zhenguo wu Wei xiang Yuxia Liu Gongke Wang Kanghui Hu Qi Xu Yang song Xiaodong Guo College of Chemical Engineering Sichuan UniversityChengdu 610065SichuanChina College of Materials and Chemistry&Chemical Engineering Chengdu University of TechnologyChengdu 610059SichuanChina The Key Laboratory of Life Organic Analysis Key Laboratory of PharmaceuticalSchool of Chemistry and Chemical EngineeringQufu Normal UniversityQufu 273165ShandongChina School of Materials Science and Engineering Henan Normal UniversityXinXiang 453007HenanChina

The introduction of spinel phase to form the layered-spinel structure(LSS)is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides(LMR).But is this structure universal for all LMR systems?In this work,different Mn/Ni ratio systems with the LSS are discussed in *** is found that,high discharge capacity(200.8 mA h g^(-1) at 1C rate;1C=250 mA h g^(-1))as well as high capacity-retention(94%at 1C rate after 100 cycles)can be achieved by forming the LSS for low-Ni system(Mn/Ni=5.0).However,the capacity retention decreases severely in the high-Ni system(Mn/Ni=3.5,2.6).For example,when the ratio of Mn/Ni is 3.5,the capacity-retention of the layered-spinel sample was only 65.8%,compared to the 83%of the original LMR *** Ex-situ XRD,XPS,and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal *** work provides guidance for optimizing the proportions of elements and the design of structures for the LMR.

关键词： Li-ion battery Li-and Mn-rich layered oxides Spinel phase Mn/Ni ratio

Study of the synthesis,antiviral bioactivity and interaction mechanisms of novel chalcone derivatives that contain the 1,1-dichloropropene moiety

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Chinese Chemical Letters 2017年第7期28卷 1566-1570页

作者： Liang-Run Dong De-Yu Hu Zeng-Xue wu Ji-xiang Chen Bao-An song State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering Key Laboratory of Green Pesticide and Agricultural BioengineeringMinistry of EducationResearch and Development Center for Fine ChemicalsGuizhou UniversityGuiyang 550025China

A series of novel chalcone derivatives that contain the 1,1-dichloropropene moiety was designed and synthesized. Bioactivity assays showed that most of the target compounds exhibited moderate to good antiviral activity against tobacco mosaic virus（TMV） at 500 mg/m L. Among the target compounds,compound 7h showed the highest in vivo inactivation activity against TMV with the EC50 and EC90value of 45.6 and 327.5 mg/m L, respectively, which was similar to that of Ningnanmycin（46.9 and 329.4 mg/m L）and superior to that of Ribavirin（145.1 and 793.1 mg/m L）. Meanwhile, the microscale thermophoresis and fluorescence spectroscopy experiments showed that the compound 7h had a strong interaction with the tobacco mosaic virus coat protein.

关键词： Chalcone derivatives 1 1-Dichloropropene moiety Synthesis Antiviral activity Interaction mechanisms

Resource allocation with minimum transmit power in multicast OFDM systems

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Journal of Systems Engineering and Electronics 2010年第3期21卷 355-360页

作者： Bo wu Jun Shen Haige xiang School of Electronics Engineering and Computer Science Peking University Beijing 100871 R R. China

To minimize the total transmit power for multicast service in an orthogonal frequency division multiplexing（OFDM） downlink system,resource allocation algorithms that adaptively allocate subcarriers and bits are *** proposed algorithms select users with good channel conditions for each subcarrier to reduce the transmit power,while guaranteeing each user＇s instantaneous minimum rate *** resource allocation problem is first formulated as an integer programming（IP） problem,and then,a full search algorithm that achieves an optimal solution is *** reduce the computation load,a suboptimal algorithm is *** suboptimal algorithm decouples the joint resource allocation problem by separating subcarrier and bit ***-like algorithms are employed in both *** results illustrate that the proposed algorithms can significantly reduce the transmit power compared with the conventional multicast approach and the performance of the suboptimal algorithm is close to the optimum.

关键词： resource allocation multicast orthogonal frequency division multiplexing (OFDM) integer programming (IP) greedy algorithm.

A comprehensive method for joint wear prediction in planar mechanical systems with clearances considering complex contact conditions

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Science China(Technological Sciences) 2015年第1期58卷 86-96页

作者： xiang wuWeiKai YAN ShaoZe wu JiaNing State Key Laboratory of Tribology Department of Mechanical Engineering Tsinghua University

A comprehensive method to predict wear in planar mechanical systems with clearance joints is presented and discussed in this *** method consists of a system dynamic analysis and a joint wear *** the size and shape of the clearance are dictated by wear and evolve with the dynamic response of the system,the contact between the journal and bearing could be conformal or non-conformal,which makes the contact conditions in clearance joints quite *** a modified contact force model is employed to evaluate the joint reaction force in this *** the nonlinear stiffness coefficient is related to the physical and geometrical properties of contact bodies and varies with the deformation,this contact force model is applicable to different contact conditions between the journal and ***,based on the Archard’s wear model,the amount of wear can be quantified in the *** the geometry is updated to reflect the evolving contact ***,the wear process and the contact force model are integrated into the motion equations of the system to perform coupled iterative analyses between system dynamic response and joint wear *** addition,a slider-crank mechanism is simulated as an example to demonstrate efficiency of the proposed method and to carry out a parametric study on mechanical systems considering joint *** influence of clearance size and driving power are discussed and compared *** index of concordance is introduced to quantify contributions of contact pressure and sliding distance to wear rate under different types of journal *** study could help to predict joint wear in mechanical systems with clearances and optimize mechanisms in design.

关键词： wear joint clearance dynamics

FlexPolh adaptive event polling for network-intensive applications

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Frontiers of Computer Science 2016年第3期10卷 532-542页

作者： Xingbo wu xiang LONG Lei WANG School of Computer Science and Engineering Beihang University Beijing 100191 China

In today＇s data centers supporting Internet-scale computing and input/output （I/0） services, increasingly more network-intensive applications are deployed on the network as a service. To this end, it is critical for the applications to quickly retrieve requests from the network and send their responses to the network. To facilitate this network func- tion, operating system usually provides an event notification mechanism so that the applications （or the library） know if the network is ready to supply data for them to read or to receive data for them to write. As a widely used and repre- sentative notification mechanism, epoll in Linux provides a scalable and high-performance implementation by allowing applications to specifically indicate which connections and what events on them need to be watched. As epoll has been used in some major systems, includ- ing key-value （KV） systems, such as Redis and Memcached, and web server systems such as NGINX, we have identified a substantial performance issue in its use. For the sake of efficiency, applications usually use epoll＇s system calls to inform the kernel exactly of what events they are interested in and always keep the information up-to-date. However, in a system with demanding network traffic, such a rigid main- tenance of the information is not necessary and the excess number of system calls for this purpose can substantially de- grade the system＇s performance. In this paper, we use Redis as an example to explore the issue. We propose a strategy of informing the kernel of the interest events in a manner adaptive to the current network load, so that the epoll system calls can be reduced and the events can be efficiently deliv- ered. We have implemented an event-polling library, named as FlexPoll, purely in user-level without modifying any ker- nel code. Our evaluation on Redis shows that the query through- put can be improved by up to 46.9% on micro-benchmarks, and even up to 67.8% on workloads emulating real-world a

关键词： operating systems performance evaluation andmodeling storage systems and networks workload characterization

Fuzzy Q learning algorithm for dual-aircraft path planning to cooperatively detect targets by passive radars

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Journal of Systems Engineering and Electronics 2013年第5期24卷 800-810页

作者： xiang Gao Yangwang Fang Youli wu School of Aeronautics and Astronautic Engineering Air Force Engineering University

The problem of passive detection discussed in this paper involves searching and locating an aerial emitter by dualaircraft using passive radars. In order to improve the detection probability and accuracy, a fuzzy Q learning algorithrn for dual-aircraft flight path planning is proposed. The passive detection task model of the dual-aircraft is set up based on the partition of the target active radar＇s radiation area. The problem is formulated as a Markov decision process （MDP） by using the fuzzy theory to make a generalization of the state space and defining the transition functions, action space and reward function properly. Details of the path planning algorithm are presented. Simulation results indicate that the algorithm can provide adaptive strategies for dual-aircraft to control their flight paths to detect a non-maneuvering or maneu- vering target.

关键词： Markov decision process (MDP) fuzzy Q learning dual-aircraft coordination path planning passive detection.