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Multi-temperature modeling of femtosecond laser pulse on metallic nanoparticles accounting for the temperature dependences of the parameters

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Nanotechnology and Precision Engineering 2022年第4期5卷 26-45页

作者： Victor K.Pustovalov Belarussian National Technical University Pr.Independency65Minsk 220013Belarus

This review considers the fundamental dynamical processes of metal nanoparticles during and after the impact of a femtosecond laser pulse on a nanoparticle,including the absorption of photons.Understanding the sequence of events after photon absorption and their timescales is important for many applications of nanoparticles.Various processes are discussed,starting with optical absorption by electrons,proceeding through the relaxation of the electrons due to electron–electron scattering and electron–phonon coupling,and ending with the dissipation of the nanoparticle energy into the environment.The goal is to consider the timescales,values,and temperature dependences of the electron heat capacity and the electron–phonon coupling parameter that describe these processes and how these dependences affect the electron energy relaxation.Two-and four-temperature models for describing electron–phonon relaxation are discussed.Significant emphasis is paid to the proposed analytical approach to modeling processes during the action of a femtosecond laser pulse on a metal nanoparticle.These consider the temperature dependences of the electron heat capacity and the electron–phonon coupling factor of the metal.The entire process is divided into four stages:(1)the heating of the electron system by a pulse,(2)electron thermalization,(3)electron–phonon energy exchange and the equalization of the temperature of the electrons with the lattice,and(4)cooling of the nanoparticle.There is an appropriate analytical description of each stage.The four-temperature model can estimate the parameters of the laser and nanoparticles needed for applications of femtosecond laser pulses and nanoparticles.

关键词： Femtosecond pulse Nanoparticle Metallic Model thermal processes Analytical solution

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Unravelling the precipitation evolutions of AZ80 magnesium alloy during non-isothermal and isothermal processes

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Journal of Materials Science & Technology 2021年第16期75卷 184-195页

作者： Longqing Tang Guowei Bo Fulin Jiang Shiwei Xu Jie Teng Dingfa Fu Hui Zhang College of Materials Science and Engineering Hunan UniversityChangsha 410082China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China

The precipitation evolutions of Mg-Al-Zn alloys play essential roles in their mechanical properties,corrosion performance,formability,plastic deformation mechanisms and texture development.In the present work,the precipitation evolutions of AZ80 magnesium alloy during both non-isothermal and isothermal processes were unraveled by utilizing in situ electrical resistivity monitoring,hardness testing,differential scanning calorimetry and microstructural characterization.The results showed that discontinuous precipitation(DP)and continuous precipitation(CP)occurred competitively during non-isothermal and isothermal processes.The precipitation of dominantβ-Mg17 Al12 phase during non-isothermal processes was highly dependent on the thermal history.During isothermal processes,the precipitation behavior of AZ80 magnesium alloy could be considered as the functions of holding temperature and time.At lower temperatures,massive DP and CP were gradually formed to equally strengthen the alloy.At higher temperatures,the Ostwald coarsening was characterized in the later stages and indicated to slightly soften the alloy.Isothermal time-temperature-precipitation curves and quantitative precipitate evolution were estimated to unravel precipitation characteristics and their strengthening functions.

关键词： Magnesium alloy Precipitation thermal processes In situ electrical resistivity Strengthening

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On transitioning from PID to ADRC in thermal power plants

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Control Theory and Technology 2021年第1期19卷 3-18页

作者： Zhenlong Wu Zhiqiang Gao Donghai Li YangQuan Chen Yanhong Liu School of Electrical Engineering Zhengzhou UniversityZhengzhou 450001HenanChina Department of Electrical and Computer Engineering Cleveland State UniversityClevelandOH 44115USA State Key Lab of Power Systems Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Mechatronics Embedded Systems and Automation(MESA)LabDepartment of Mechanical EngineeringSchool of EngineeringUniversity of CaliforniaMercedCA 95343USA

This paper focuscs on the recent progress in the adoption of active disturbance rejection control(ADRC)in thermal pro-cesses as a viable alternative to proportional-_integral-derivative(PID),especially in coa-fired power plants.The profound interpretation of this paradigm shift,with backward compatibility,is discussed in detail.A few fundamental issues associated with ADRC's applications in thermal processes are discussed,such as implementation,tuning,and the structural changes.Examples and case studies are presented,encompassing coal-fired power plants,gas turbines and nuclear power plants,as well as highlighting results of field applications.Also discussed are future research opportunities brought by ADRC's entry as the baseline control technology in thermal processes.

关键词： Active disturbance rejection control(ADRC) Proportional-integral-derivative(PID) thermal processes Coal-fired power plant Field applications

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