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Advances on topological materials

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Frontiers of physics 2020年第4期15卷 33-34页

作者： qian Niu Department of Physics The University of Texas at AustinAustinTX 78712USA

Topological materials refer to solid structures with topo-logically protected electronic states or other degrees of freedom.A prime example is a Chern insulator in which the occupied bands of states are organized with a non-trivial topology as characterized by a nonzero Chern in-teger,exhibiting gapless chiral excitations on the bound-aries,which are robust against scatterings.

关键词： topological trivial excitation

Derivative-free reinforcement learning:a review

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Frontiers of Computer Science 2021年第6期15卷 75-93页

作者： Hong qian Yang YU National Key Laboratory for Novel Software Technology Nanjing UniversityNanjing 210023China

Reinforcement learning is about learning agent models that make the best sequential decisions in unknown *** an unknown environment,the agent needs to explore the environment while exploiting the collected information,which usually forms a sophisticated problem to ***-free optimization,meanwhile,is capable of solving sophisticated *** commonly uses a sampling-andupdating framework to iteratively improve the solution,where exploration and exploitation are also needed to be well ***,derivative-free optimization deals with a similar core issue as reinforcement learning,and has been introduced in reinforcement learning approaches,under the names of learning classifier systems and neuroevolution/evolutionary reinforcement *** such methods have been developed for decades,recently,derivative-free reinforcement learning exhibits attracting increasing ***,recent survey on this topic is still *** this article,we summarize methods of derivative-free reinforcement learning to date,and organize the methods in aspects including parameter updating,model selection,exploration,and parallel/distributed ***,we discuss some current limitations and possible future directions,hoping that this article could bring more attentions to this topic and serve as a catalyst for developing novel and efficient approaches.

关键词： reinforcement learning derivative-free optimization neuroevolution reinforcement learning neural architecture search

Modeling the measurement precision of Fringe Projection Profilometry

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Light(Science & Applications) 2023年第11期12卷 2480-2497页

作者： Shenzhen Lv qian Kemao School of Computer Science and Engineering Nanyang Technological UniversitySingaporeSingapore

Three-dimensional(3D)surface geometry provides elemental information in various sciences and precision *** Projection Profilometry(FPP)is one of the most powerful non-contact(thus non-destructive)and non-interferometric(thus less restrictive)3D measurement techniques,featuring at its high ***,the measurement precision of FPP is currently evaluated experimentally,lacking a complete theoretical model for *** propose the first complete FPP precision model chain including four stage models(camera intensity,fringe intensity,phase and 3D geometry)and two transfer models(from fringe intensity to phase and from phase to 3D geometry).The most significant contributions include the adoption of a non-Gaussian camera noise model,which,for the first time,establishes the connection between camera’s electronics parameters(known in advance from the camera manufacturer)and the phase precision,and the formulation of the phase to geometry transfer,which makes the precision of the measured geometry representable in an explicit and concise *** a result,we not only establish the full precision model of the 3D geometry to characterize the performance of an FPP system that has already been set up,but also explore the expression of the highest possible precision limit to guide the error distribution of an FPP system that is yet to *** theoretical models make FPP a more designable technique to meet the challenges from various measurement demands concerning different object sizes from macro to micro and requiring different measurement precisions from a few millimeters to a few micrometers.

关键词： sizes concerning formulation

Deeply missing my career idol and role model--Professor Perry ***

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Frontiers of Environmental Science & Engineering 2023年第9期17卷 257-258页

作者： Yi qian School of Environment Tsinghua UniversityBeijing 100084China

Upon hearing the news of Professor Perry ***’s passing,I felt deeply saddened and heartbroken,and was unable to contain my emotions.I couldn’t help but reminiscing about the cherished moments we shared together and the valuable lessons I learned from him over the years.I first met Professor Perry *** in *** the opportunity of attending a conference in the United States,I visited Professor McKinney at the University of Kansas,the first American expert in my field that I had ever known of.I told him that I was very interested in Professor McCarty’s research on aerobic bio-filters and wanted to learn more.“Let me give Perry a call,”he said immediately,and in less than five minutes,Perry and I became *** turned out that Professor McKinney had been Professor McCarty’s teacher and mentor in the past.I changed my flight immediately and flew to California the next day,where I met Professor McCarty,a world-renowned expert in water pollution control,and visited the aerobic bio-filter he established and their water pollution control *** had inspiring yet amiable conversations,and a friendship that lasted for over 30 years ensued.

关键词： visited career missing

Sign-Changing Solutions for a Class of Nonlinear Elliptic Problems

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Chinese Annals of Mathematics,Series B 2007年第5期28卷 609-616页

作者： Aixia qian Department of mathematics Qufu Normal University Qufu 273165 Shandong China.

In the present paper, the author studies the existence of sign-changing solutions for nonlinear elliptic equations, which have jumping nonlinearities, and may or may not be resonant with respect to Fucik spectrum, via... 详细信息

关键词： Sign-changing solutions Fucik spectrum Jumping nonlinearities

Rational cubic/quartic Said-Ball conics

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Applied Mathematics(A Journal of Chinese Universities) 2011年第2期26卷 198-212页

作者： HU qian-qian WANG Guo-jin Department of Mathematics Zhejiang University Hangzhou 310027 College of Statistics and Mathematics Zhejiang Gongshang University Hangzhou 310018.

In CAGD, the Said-Ball representation for a polynomial curve has two advantagesover the B′ezier representation, since the degrees of Said-Ball basis are distributed in a step *** advantage is that the recursive algorithm of Said-Ball curve for evaluating a polynomialcurve runs twice as fast as the de Casteljau algorithm of B′ezier curve. Another is that theoperations of degree elevation and reduction for a polynomial curve in Said-Ball form are simplerand faster than in B′ezier form. However, Said-Ball curve can not exactly represent conics whichare usually used in aircraft and machine element design. To further extend the utilizationof Said-Ball curve, this paper deduces the representation theory of rational cubic and quarticSaid-Ball conics, according to the necessary and su？cient conditions for conic representation inrational low degree B′ezier form and the transformation formula from Bernstein basis to Said-Ballbasis. The results include the judging method for whether a rational quartic Said-Ball curve is aconic section and design method for presenting a given conic section in rational quartic Said-Ballform. Many experimental curves are given for confirming that our approaches are correct ande？ective.

关键词： Rational Said-Ball curve Rational B′ezier curve conics.

Detection of Phthalate Esters in Environmental Water Samples -Comparison of Nylon6 Nanofibers Mat-based Solid Phase Extraction and Other Conventional Extraction Methods

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Chinese Journal of Chemistry 2011年第3期29卷 567-574页

作者： Xu, qian Ministry of Education Key Laboratory of Environmental Medicine and Engineering Southeast University Nanjing Jiangsu 210009 China State Key Laboratory of Bioelectronics Southeast University Nanjing Jiangsu 210096 China Suzhou Key Laboratory of Environment and Biosafety Suzhou Jiangsu 215123 China

In this article, a new method for simultaneous determination of six phthalate esters was developed by a combination of electrospun nylon6 nanofibers mat-based solid phase extraction with high performance liquid chromatography-ultraviolet detector （HPLC-UV）. The six phthalate esters were dimethyl phthalate （DMP）, diethyl phthalate （DEP）, butyl benzyl phthalate （BBP）, di-n-butyl phthalate （DBP）, di-（2-ethylhexyl） phthalate （DEHP） and dioctyl phthalate （DOP）. Under optimized conditions, all target analytes in 50 mL environmental water samples could be completely extracted by 2.5 mg nylon6 nanofibers mat and eluted by 100 μL solvent. Compared with C18 cartridges solid phase extraction, C 18 disks solid phase extraction and national standard method （China）, nylon6 nanofibers mat-based solid phase extraction was advantageous in aspects of simple and fast operation, low consumption of extraction materials and organic solvents. The four methods were applied to analysis of environment water samples. All the results indicated that the determination values of target compounds with the proposed method were consistent with C18 cartridges and C18 disks solid phase extraction method, and the new method was better than the national standard method in aspects of recovery, LOD and precision. Therefore, nylon6 nanofibers mat has great potential as a novel material for solid phase extraction.

关键词： Nylon6 nanofibers mat C18 cartridges C18 disks national standard method phthalate esters highperformance liquid chromatography-ultraviolet detector

Role of interfacial water in adhesion,friction,and wear--A critical review

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Friction 2021年第1期9卷 1-28页

作者： Lei CHEN Linmao qian Tribology Research Institute State Key Laboratory of Traction PowerSouthwest Jiaotong UniversityChengdu 610031China

Surficial water adsorption and interfacial water condensation as natural phenomena that can alter the contact status of the solid interface and tribological performances are crucial in all length scales,i.e.,from earthquakes to skating at the macroscale level and even to micro/nano-electromechanical systems(M/NEMS)at the microscale/nanoscale *** water exhibits diverse structure and properties from bulk water because of its further interaction with solid *** this paper,the evolutions of the molecular configuration of the adsorbed water layer depending on solid surface chemistry(wettability)and structure,environmental conditions(i.e.,relative humidity and temperature),and experimental parameters(i.e.,sliding speed and normal load)and their impacts on tribological performances,such as adhesion,friction,and wear,are systematically *** on these factors,interfacial water can increase or reduce adhesion and friction as well as facilitate or suppress the tribochemical wear depending on the water condensation kinetics at the interface as well as the thickness and structure of the involved interfacial water.

关键词： water adsorption water condensation adhesion friction tribochemical wear

Consensus Analysis of Fractional Multi-Agent Systems with Delayed Distributed PI Controller

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Journal of Systems Science & Complexity 2023年第1期36卷 205-221页

作者： XIE Yingkang MA qian School of Automation Nanjing University of Science and TechnologyNanjing 210094China

The consensus problem for fractional multi-agent systems(MASs)with time delay is *** distributed fractional proportional-integral(PI)-type controller is designed so that the consensus of the proposed systems is ***,explicit condition to determine the crossing directions is *** results show that with the increase of time delay,the closed-loop system has two different dynamic characteristics:From consensus to nonconsensus and consensus ***,delay margin within which consensus of MASs will always hold is *** results should provide useful guidelines in the consensus analysis and in the analytical design of the distributed controllers.

关键词： Consensus switching crossing direction fractional multi-agent systems fractional PI controller time delay