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Effect of Rotation Rate on microstructures and mechanical Properties of FSW mg-Zn-Y-Zr Alloy Joints

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Journal of materials Science & Technology 2011年第12期27卷 1157-1164页

作者： g.m. xie Z.Y. ma Z.A. Luo P. Xue g.D. Wang The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China

Friction stir welding （FSW） of mg-Zn-Y-Zr plates with 6 mm in thickness was successfully carried out under a wide range of rotation rates of 600-1200 r/rain with a constant traverse speed of 100 mm/min. After FSW, the coarse grains in the parent material （Pm） were changed into fine equiaxed recrystallized grains at the＇nugget zone （NZ）. Furthermore, the coarse mg-Zn-Y particles （W-phase） were broken up and dispersed homogenously into the mg.m.trix. With increasing rotation rates, the size of the W-phase particles at the NZ significantly decreased, but the recrystallized grain size tended to increase. The hardness values of the NZs for all the FSW joints were higher than those of the Pm, and the lowest hardness values were detected in the heat affected zone （HAZ）. The fracture occurred in the thermo-mechanical affected zone （TmAZ） on the advancing side for all the FSW joints in the tensile test, due to the incompatibility of the plastic deformation between the NZ and TmAZ caused by remarkably different orientation of grains and W-phase particles. The strength of FEW ioint reaches 90% of that of its Pm

关键词： Friction stir welding magnesium alloys microstructure mechanical property

Optimal Coordination of Transportable Power Sources and Repair Crews for Service Restoration of Distribution Networks Considering Uncertainty of Traffic Congestion

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Journal of modern Power Systems and Clean Energy 2024年第1期12卷 189-201页

作者： Zhao Shi Yan Xu Dunjian xie Shiwei xie Amer m.Y.m.ghias Nanyang Technological University Singapore the School of Electrical Engineering and Automation Fuzhou UniversityFuzhou 350108China

This paper proposes a new method for service restoration of distribution network with the support of transportable power sources(TPSs)and repair crews(RCs).Firstly,a coupling.m.del of distribution networks and vehicle routing of TPSs and RCs is proposed,where the TPSs serve as emergency power supply sources,and the RCs are used to repair the faulted *** the uncertainty of traffic congestion,the probability distribution of the travel time spent on each road is derived based on the Nesterov user equilibrium model,and a two-stage stochastic program is formulated to determine the optimal routings of TPSs and *** efficiently solve the proposed stochastic mixed-integer linear program(mILP),a two-phase scenario reduction method is then developed to scale down the problem size,and an adaptive progressive hedging algorithm is used for an efficient *** effectiveness of the proposed methods and algorithms has been illustrated in a modified IEEE 33-bus system.

关键词： Service restoration distribution network traffic uncertainty transportable power source repair crew stochastic program

g.m.-theoretic multi-agent motion planning in a mixed environment

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Control Theory and Technology 2024年第3期22卷 379-393页

作者： Xiaoxue Zhang Lihua xie School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore City 639798Singapore

The motion planning problem for multi-agent systems becomes particularly challenging when humans or human-controlled robots are present in a mixed *** address this challenge,this paper presents an interaction-aware motion planning approach based on g.m. theory in a receding-horizon manner Leveraging the framework provided by dynamic potential g.m.s for handling the interactions among agents,this approach formulates the multi-agent motion planning problem as a differential potential g.m.,highlighting the effectiveness of constrained potential g.m.s in facilitating interactive motion planning among ***,online learning techniques are incorporated to dynamically learn the unknown preferences and models of humans or human-controlled robots through the analysis of observed *** evaluate the effectiveness of the proposed approach,numerical simulations are conducted,demonstrating its capability to generate interactive trajectories for all agents,including humans and human-controlled agents,operating within the mixed *** simulation results illustrate the effectiveness of the proposed approach in handling the complexities of multi-agent motion planning in real-world scenarios.

关键词： motion planning Differential potential g.m. multi-agent systems Constrained potential g.m.

Analysis of a class of globally divergence-free HDg.m.thods for stationary Navier-Stokes equations

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Science China mathematics 2024年第5期67卷 1133-1158页

作者： gang Chen Xiaoping xie School of mathematics Sichuan University Chengdu 610064China

In this paper,we analyze a class of globally divergence-free(and therefore pressure-robust)hybridizable discontinuous galerkin(HDg)finite element methods for stationary Navier-Stokes *** methods use the P_(k)/P_(k-1)(k≥1)discontinuous finite element combination for the velocity and pressure approximations in the interior of elements,piecewise Pm(m=k,k-1)for the velocity gradient approximation in the interior of elements,and piecewise P_(k)/P_(k) for the trace approximations of the velocity and pressure on the inter-element *** show that the uniqueness condition for the discrete solution is guaranteed by that for the continuous solution together with a sufficiently small mesh *** on the derived discrete HDg Sobolev embedding properties,optimal error estimates are *** experiments are performed to verify the theoretical analysis.

关键词： Navier-Stokes equations HDg.m.thods divergence-free uniqueness condition error estimates

Boson star superradiance

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Science China(Physics,mechanics & Astronomy) 2024年第6期67卷 69-78页

作者： He-Yu gao Paul m.Saffin Yi-Jie Wang Qi-Xin xie Shuang-Yong Zhou School of Physical Sciences University of Science and Technology of ChinaHefei 230026China School of Physics and Astronomy University of NottinghamUniversity ParkNottingham NG72RDUK Interdisciplinary Center for Theoretical Study University of Science and Technology of ChinaHefei 230026China Peng Huanwu Center for Fundamental Theory Hefei 230026China

Recently,it has been realized that in some systems internal space rotation can induce energy amplification for scattered waves,similar to rotation in real *** particularly,it has been shown that energy extraction is possible for a Q-ball,a stationary non-topological soliton that is coherently rotating in its field *** this paper,we generalize the analysis to the case of boson stars,and show that the same energy extraction mechanism still works for boson stars.

关键词： superradiance boson star field space rotation

Tailoring.m.ene Thickness and Functionalization for Enhanced Room‑Temperature Trace NO_(2) Sensing

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Nano-micro Letters 2024年第5期16卷 71-86页

作者： muhammad Hilal Woochul Yang Yongha Hwang Wanfeng xie Department of Physics Dongguk UniversitySeoul 04620Republic of Korea Department of Control and Instrumentation Engineering Korea UniversitySejong 30019Republic of Korea School of Electronics&Information University‑Industry Joint Center for Ocean Observation and Broadband CommunicationQingdao UniversityQingdao 266071China

In this study,precise control over the thickness and termination of Ti3C2TX mXene flakes is achieved to enhance their electrical properties,environmental stability,and gas-sensing *** a hybrid method involving high-pressure processing,stirring,and immiscible solutions,sub-100 nm mXene flake thickness is achieved within the mXene film on the *** control is achieved by defunctionalizing.m.ene at 650℃ under vacuum and H2 gas in a CVD furnace,followed by refunctionalization with iodine and bromine vaporization from a bubbler attached to the ***,the introduction of iodine,which has a larger atomic size,lower electronegativity,reduce shielding effect,and lower hydrophilicity(contact angle:99°),profoundly affecting *** improves the surface area(36.2 cm^(2) g^(-1)),oxidation stability in aqueous/ambient environments(21 days/80 days),and film conductivity(749 S m^(-1)).Additionally,it significantly enhances the gas-sensing performance,including the sensitivity(0.1119Ωppm^(-1)),response(0.2% and 23%to 50 ppb and 200 ppm NO_(2)),and response/recovery times(90/100 s).The reduced shielding effect of the–I-terminals and the metallic characteristics of mXene enhance the selectivity of I-mXene toward *** approach paves the way for the development of stable and high-performance gas-sensing two-dimensional materials with promising prospects for future studies.

关键词： Controlled mXene thickness gaseous functionalization approach Lower electronegativity functional groups Enhanced mXene stability Trace NO_(2)sensing

Customer Joining Behavior and Regulation Strategy in Visible multi-Server Queues with Synchronous Vacations of Partial Servers

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Journal of Systems Science & Complexity 2024年第3期37卷 1209-1232页

作者： SUN Wei WANg Hao xie Xumeng LI Shiyong School of Economics and manag.m.nt Yanshan UniversityQinhuangdao 066004China

This paper studies customer joining behavior and system regulation strategy in nonexhaustive visible m/m/m queues with synchronous vacations of a part of the *** this part of the servers are idle,they take multiple vacations simultaneously(vacation period).Until there are customers waiting in the queue,they are reactivated and all servers are busy or idle(busy period).The authors call this part of the servers as“partial servers”.In view of the fully visible queue and the almost visible queue,the authors obtain customers’equilibrium joining threshold strategies and their socially optimal joining threshold strategies,respectively,and observe that customer joining behavior in equilibrium generally makes the system overcrowded,which makes the equilibrium social welfare lower than the optimal social *** regulation,interestingly,for optimizing social welfare,the system manager hopes not only customers arriving in vacation period pay attention to the number of partial servers,but also customers arriving in busy period should care about it rather than ***,arranging.m.re servers for vacation does not necessarily lead to the decrease of social welfare on condition that the number of partial servers is close to *** for the information advantage of the fully visible case,it is not obvious for increasing social welfare and even unfavorable to servers’profit unless the number of partial servers is big ***,given the different composition of social welfare,there exists the optimal number of partial servers and the optimal arrival rate of customers for maximizing social welfare.

关键词： Customer behavior non-exhaustive service partial servers regulation strategy synchronous vacations visible queue

Kriging.m.del Averaging Based on Leave-One-Out Cross-Validation method

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Journal of Systems Science & Complexity 2024年第5期37卷 2132-2156页

作者： FENg Ziheng ZONg Xianpeng xie Tianfa ZHANg Xinyu School of mathematics Statistics and MechanicsBeijing University of TechnologyBeijing 100124China Academy of mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China

In recent years,Kriging.m.del has gained wide popularity in various fields such as space geology,econometrics,and computer *** a result,research on this model has *** this paper,the authors propose a model averaging estimation based on the best linear unbiased prediction of Kriging.m.del and the leave-one-out cross-validation method,with consideration for the model *** authors present a weight selection criterion for the model averaging estimation and provide two theoretical justifications for the proposed ***,the estimated weight based on the proposed criterion is asymptotically optimal in achieving the lowest possible prediction ***,the proposed method asymptotically assigns all weights to the correctly specified models when the candidate model set includes these *** effectiveness of the proposed method is verified through numerical analyses.

关键词： Asymptotic optimality best linear unbiased prediction cross-validation Kriging.m.del model averaging

Enhanced properties of stone coal-based composite phase change materials for thermal energy storage

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International Journal of minerals,metallurgy and materials 2024年第1期31卷 206-215页

作者： Baoshan xie Huan ma Chuanchang Li Jian Chen Key Laboratory of Renewable Energy Electric-Technology of Hunan Province School of Energy and Power EngineeringChangsha University of Science and TechnologyChangsha 410114China State Key Laboratory of Disaster Prevention and Reduction for Power grid Changsha University of Science and TechnologyChangsha 410114China

Phase change materials (PCms) can be incorporated with low-cost minerals to synthesize composites for thermal energy storage in building *** coal (SC) after vanadium extraction treatment shows potential for secondary utilization in composite *** prepared SC-based composite PCms with SC as a matrix,stearic acid (SA) as a PCm,and expanded graphite (Eg) as an *** combined roasting and acid leaching treatment of raw SC was conducted to understand the effect of vanadium extraction on promoting loading *** showed that the combined treatment of roasting at 900℃ and leaching increased the SC loading of the composite by 6.2%by improving the specific surface *** loading capacity and thermal conductivity of the composite obviously increased by 127%and 48.19%,respectively,due to the contribution of 3wt% *** data were supported by the high load of 66.69%and thermal conductivity of 0.59 W·m^(-1)·K-1of the designed *** obtained composite exhibited a phase change temperature of 52.17℃,melting latent heat of 121.5 J·g^(-1),and good chemical *** SC-based composite has prospects in building applications exploiting the secondary utilization of minerals.

关键词： thermal energy storage phase change material stone coal vanadium extraction secondary utilization