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Effect of a negative DC bias on a capacitively coupled Ar plasma operated at different radiofrequency voltages and gas pressures

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Plasma Science and Technology 2024年第5期26卷 62-71页

作者：相垚君王晓坤刘永新王友年 Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China chair of Applied Electrodynamics and Plasma Technology Ruhr University BochumBochum 44801Germany

The effect of a negative DC bias,|V_(dc)|,on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas *** electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission *** electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current *** was found that at a low|V_(dc)|,***α-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plasma impedance becomes more capacitive due to a widened ***,RF power deposition is ***|V_(dc)|exceeds a certain value,the plasma changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF ***,the plasma impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages,andα–γmode transition occurs at a lower|V_(dc)|at a higher RF *** increasing the pressure,plasma impedance becomes more resistive,so RF power deposition and electron density are *** particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

关键词： RF capacitively coupled plasma DC-overlapped RF discharge power deposition discharge mode transition

Experimental and numerical investigation to elucidate the fluid flow through packed beds with structured particle packings

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Particuology 2024年第6期89卷 218-237页

作者： Shirin Patil Christian Gorges Joel Lòpez Bonilla Moritz Stelter Frank Beyrau Berend van Wachem Laboratory of Technical Thermodynamics Otto-von-Guericke-Universität MagdeburgUniversitätsplatz 239106 MagdeburgGermany chair of Mechanical Process Engineering Otto-von-Guericke-Universität MagdeburgUniversitätsplatz 239106 MagdeburgGermany

The present paper presents an experimental and numerical investigation of the dispersion of the gaseous jet flow and co-flow for the simple unit cell(SUC)and body-centred cubic(BCC)configuration of particles in packed *** experimental setup is built in such a way that suitable and simplified boundary conditions are imposed for the corresponding numerical framework,so the simulations can be done under very similar conditions as the ***,a porous plate is used for the co-flow to achieve the uniform velocity and the fully developed flow is ensured for the jet *** SUC and BCC particle beds consist of 3D-printed spheres,and the non-isotropy near the walls is mostly eliminated by placing half-spheres at the channel *** flow velocities are analysed directly at the exit of the particle bed for both beds over 36 pores for the SUC configuration and 60 pores for the BCC configuration,for particle Reynolds numbers of 200,300,and *** particle image velocimetry is experimentally arranged in such a way that the velocities over the entire region at the exit of the packed bed are obtained *** numerical method consists of a state-of-the-art immersed boundary method with adaptive mesh *** paper presents the pore jet structure and velocity field exiting from each pore for the SUC and BCC packed particle *** numerical and experimental studies show a good agreement for the SUC configuration for all flow *** the BCC configuration,some differences can be observed in the pore jet flow structure between the simulations and the experiments,but the general flow velocity distribution shows a good overall *** axial velocity is generally higher for the pores located near the centre of the packed bed than for the pores near the *** addition,the axial velocities are observed to increase near the peripheral pores of the packed *** behaviour is predominant for the BCC configuration as compared to t

关键词： Uniform particle packing Packed bed reactor Stereo particle image velocimetry Immersed boundary method

Tailoring the microstructure， tensile properties， and creep resistance of additively manufactured Inconel 718 superalloy by post-processing

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Transactions of Nonferrous Metals Society of China 2024年

作者： Sajad Ghaemifar Milad Roostaei Mohammad Reza Zamani Stefan Wurster Hamed Mirzadeh School of Metallurgy and Materials Engineering College of Engineering University of Tehran Erich Schmid Institute of Materials Science Austrian Academy of Sciences Department of Materials Science chair of Materials Physics Montanuniversit?t Leoben

Effects of post-processing heat treatments on the microstructure， aging kinetics， and room/elevated temperature mechanical properties of additively manufactured Inconel 718 superalloy were investigated. Scanning electron microscopy (SEM)， electron backscattered diffraction (EBSD)， and X-ray diffraction (XRD)， as well as hardness， tensile， and creep testing were used for characterization. At temperatures higher than 1100 °C， homogenization treatment resulted in the appearance of equiaxed grains by recrystallization and diminishing the dislocation density. The precipitation activation energy for the homogenized aged condition was obtained as 203 kJ/mol， which was higher than the value of ～160 kJ/mol for the as-built IN718 superalloy. Therefore， direct aging resulted in a faster aging response， which led to a significant improvement in tensile properties， as rationalized by the strengthening mechanisms. Direct aging treatment resulted in a higher elevated-temperature ultimate tensile strength (UTS) as well as the optimum creep life and lowest minimum creep rate in comparison with other heat treating routes， which were attributed to the presence of fine and uniformly dispersed strengthening precipitates in conjunction with the high dislocation density.

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ON THE FOURIER-VILENKIN COEFFICIENTS

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Acta Mathematica Scientia 2017年第2期37卷 293-300页

作者： Martin G.GRIGORYAN Stepan SARGSYAN chair of higher mathematics Faculty of Physics Yerevan State University

In this article, we prove the following statement that is true for both unbounded and bounded Vilenkin systems： for any ε∈ （0, 1）, there exists a measurable set E C [0, 1） of measure bigger than 1 - s such that for any function f ∈ LI[0, 1）, it is possible to find a function g ∈ L^1 [0, 1） coinciding with f on E and the absolute values of non zero Fourier coefficients of g with respect to the Vilenkin system are monotonically decreasing.

关键词： Vilenkin system expansions Fourier coefficients

Computing Persistent Homology by Spanning Trees and Critical Simplices

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Research 2024年第2期2023卷 519-527页

作者： Dinghua Shi Zhifeng Chen Chuang Ma Guanrong Chen Department of mathematics Cllege of ScienceShanghai UniversityShanghaiChina School of Big Data Fuzhou University of International Studies and TradeFuzhouChina Department of Data Science and Big Data Technology School of InternetAnhui UniversityHefeiChina Department of Electrical Engineering City University of Hong KongHong KongChina

Topological data analysis can extract effective information from higher-dimensional *** mathematical basis is persistent *** persistent homology can calculate topological features at different spatiotemporal scales of the dataset,that is,establishing the integrated taxonomic relation among points,lines,and ***,the simplicial network composed of all-order simplices in a simplicial complex is *** the sequence of nested simplicial subnetworks can be regarded as a discrete Morse function from the simplicial network to real values,a method based on the concept of critical simplices can be developed by searching all-order spanning *** this new method,not only the Morse function values with the theoretical minimum number of critical simplices can be obtained,but also the Betti numbers and composition of all-order cavities in the simplicial network can be calculated ***,this method is used to analyze some examples and compared with other methods,showing its effectiveness and feasibility.

关键词： Morse establishing topological

Acceleration of solar wind particles due to inertial Alfvén waves

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Communications in Theoretical Physics 2024年第6期76卷 137-141页

作者： Kiran Batool Imran A Khan M Shamir Abdul Kabir S Ayaz Theoretical Physics Department National Centre for PhysicsIslamabad 44000Pakistan Department of Space Sciences Institute of Space TechnologyIslamabad 44000Pakistan Space and Astrophysics Research Lab(SARL) National Center of GIS and Space Applications(NCGSA)Islamabad 44000Pakistan Salam chair Department of PhysicsGC University LahoreKatchery RoadLahorePunjab 54000Pakistan Department of Space Science and CSPAR University of Alabama in HuntsvilleHuntsvilleAL 35899United States of America

Gaining an understanding of the effects and dynamics of the solar wind is crucial for the study of space weather,Earth's magnetosphere,spacecraft protection,the dynamics of the Solar System,and various other *** show that Alfvén waves effectively transfer energy to resonant *** study demonstrates how inertial Alfvén waves deliver their energy to resonant plasma particles in different solar environments under certain *** analysis shows that inertial Alfvén waves experience more rapid damping with increasing parallel wavenumber,ambient magnetic field strength,and particle number density,coupled with a decrease in *** rate of energy transfer to resonant particles intensifies with higher temperatures and reduced parallel wavenumber and particle number *** with higher initial velocities actively participate in Landau damping,especially in regions with a stronger ambient magnetic field.

关键词： solar wind inertial Alfven waves resonant particles

INTRODUCTION TO THE SPECIAL ISSUE ON mathematics AND ALGORITHMS IN COMPUTER-AIDED MANUFACTURING,ENGINEERING,AND NUMERICAL CONTROL

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Journal of Systems Science & Complexity 2013年第5期26卷 665-666页

作者： LI Hongbo SHPITALNI Moshe Key Laboratory of mathematics Mechanization Academy of Mathematics and Systems ScienceChinese Academy of Sciences Schlesinger chair of Manufacturing Systems Technion Israel Institute of Technology

Sixty years have passed since numerical control of machine tools was first demonstrated at *** then,rapid developments in advanced manufacturing technology have posed new challenges and requirements,among them faster machining(high-speed machining),higher feed-rates,more accurate parts and better surface *** only are sophisticated computerenabling technologies needed to cope with these challenges,but also significantly improved

关键词：计算机辅助制造计算机辅助工程数学工具算法数控计算机应用技术计算机数字控制麻省理工学院

CO_(2)Plume Geothermal(CPG)Systems for Combined Heat and Power Production:an Evaluation of Various Plant Configurations

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Journal of Thermal Science 2022年第5期31卷 1266-1278页

作者： SCHIFFLECHNER Christopher WIELAND Christoph SPLIETHOFF Hartmut chair of Energy Systems TUM School of Engineering and DesignTechnical University of Munich85747 GarchingGermany

CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration *** geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating *** paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power *** a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped *** net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation *** second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP ***,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG *** evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG ***,the minimum heat revenue required for compensating the power reduction increases with higher electricity *** summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.

关键词： deep geothermal energy combined heat and power generation CO_(2)plume geothermal systems petrothermal resources carbon capture utilisation and storage

Slip flow of MHD Casson fluid in an inclined channel with variable transport properties

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Communications in Theoretical Physics 2020年第9期72卷 21-38页

作者： K V Prasad Hanumesh Vaidya C Rajashekhar Sami Ullah Khan G Manjunatha J U Viharika Department of mathematics Vijayanagara Sri Krishnadevaraya UniversityVinayaka NagarBallari-583105KarnatakaIndia Bhaskaracharya Study chair Karnataka State Akkamahadevi Women's UniversityVijayapuraKarnatakaIndia Department of mathematics COMSTAS University IslamabadSahiwal Campus 54000Pakistan Department of mathematics Manipal Institute of TechnologyManipal Academy of Higher EducationManipalKarnataka576104-India

Due to the instructive role of the peristaltic phenomenon in the human body, interests have been developed in recent years towards peristaltic transport with various thermo-physical *** current investigation reveals the effects of the magnetic field and variable transport properties on the peristaltic transport of a Casson fluid slip flow through an inclined *** coupled partial differential equations regulate the fluid flow. Through the perturbation method, the momentum and energy equations are solved for small values of variable viscosity and thermal conductivity, and the closed-form solution is obtained for mass transfer. The impact on physiological quantities of related parameters of interest is evaluated and discussed via graphs. The results obtained for the current flow represent some interesting behaviors which have applications in the biomedical field.

关键词： velocity slip thermal slip concentration slip variable viscosity yield stress