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Numerical analysis of thermal plasma scrubber for CF4 decomposition

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Plasma Science and Technology 2019年第6期21卷 9-14页

作者： j KO T h KIM S ChOI Department of Nuclear and Energy Engineering Jeju National University Jeju 63243 Republic of Korea Institute for Nuclear Science and Technology Jeju National University Jeju 63243 Republic of Korea

CF4 gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse *** must be removed or converted safely due to its extreme *** a CF4 decomposition system using a thermal plasma scrubber was commercialized,its removal efficiency is *** this work,a numerical analysis of CF4 decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition *** decomposition and recombination temperatures of CF4 were analyzed using thermodynamic equilibrium *** chemical reaction of CF4 decomposition into carbon and fluorine gas was considered in this numerical *** injection position and angle of the CF4 were controlled in order to enhance the decomposition *** vertical injection of CF4 near the torch exit improved the mixing of the CF4 with the thermal plasma *** addition,it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped *** a result,it is revealed that the CF4 injection location and the reactor configuration are the most important factors in improving the decomposition rate.

关键词： numerical simulation decomposition CF4 thermal plasma scrubber

Convexification of hybrid AC-DC Optimal Power Flow with Line-Commutated Converters

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CSEE journal of Power and Energy Systems 2024年第2期10卷 617-628页

作者： hongyuan Liang Zhigang Li j.h.Zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based high-voltage DC (hVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. Simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

Dispatchable Region for Active Distribution Networks Using Approximate Second-order Cone Relaxation

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CSEE journal of Power and Energy Systems 2023年第6期9卷 1999-2007页

作者： Zhigang Li Wenjing huang j.h.Zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

Uncertainty in distributed renewable generation threatens the security of power distribution *** concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating *** DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution *** achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex *** cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve ***,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable *** studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.

关键词： Dispatchable region distribution system renewable power generation second-order cone relaxation uncertainty

Application of the extended Fourier amplitude sensitivity testing(FAST)method to inflated,axial stretched,and residually stressed cylinders

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Applied Mathematics and Mechanics(English Edition) 2023年第12期44卷 2139-2162页

作者： h.ASGhARI h.TOPOL B.MARKERT j.MERODIO Departamento de Matemática Aplicada a las TIC ETS de Ingenier a de Sistemas InformáticosUniversidad Politécnica de MadridMadrid 28031Spain Institute of General Mechanics RWTH Aachen UniversityAachen 52062Germany

This paper is dedicated to applying the Fourier amplitude sensitivity test(FAST)method to the problem of mixed extension and inflation of a circular cylindrical tube in the presence of residual *** metafunctions and the Ishigami function are considered in the sensitivity analysis(SA).The effects of the input variables on the output variables are investigated,and the most important parameters of the system under the applied pressure and axial force such as the axial stretch and the azimuthal stretch are determined.

关键词： sensitivity analysis(SA) Fourier amplitude sensitivity test(FAST)method cylindrical inflation nonlinear elasticity

Development of a group support system to support collaborative works in value management workshops

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journal of harbin Institute of Technology(New Series) 2004年第1期11卷 91-97页

作者： ChUNG j K h Dept. of Building and Real Estate Hong Kong Polytechnic University Kowloon Hong Kong China

Value Management (VM) is a rigorous and systematic approach to improve the value and optimise the overall cost of a facility. It identifies opportunities to remove unnecessary costs while assuring that quality, reliability, performance, and other critical factors will meet or exceed the customers’ expectations. It has been widely used in the construction industry in a number of countries. A recent survey, however, revealed several problems that hinder the wider use of this methodology in the industry. To overcome these problems, a feasibility study has been conducted to investigate whether or not a Group Support System (GSS) can support collaborative works in VM workshops. This paper introduces the development and structure of a prototype GSS which is designed to support the collaborative works of stakeholders in VM workshops. It begins with an introduction to the conceptual GSS framework and job plan, illustrating what GSS supports can be provided to VM workshops. This is followed by a detailed description of the GSS prototype system to demonstrate how these supports can be performed as an integrated computer system. The testing of the system is also discussed. The research findings provide strong evidence in supporting the notion of using GSS to improve VM implementation. The information support of GSS has been ranked to be the most useful GSS functions and most of the practitioners interviewed are highly interested in applying GSS to support VM workshops in the future.

关键词： group support system value management workshops construction

Grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe(41)Mn(25)Ni(24)Co8Cr2high entropy alloy

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journal of Materials Science & Technology 2020年第7期42卷 190-202页

作者： h.T.jeong W.j.Kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe(41)Mn(25)Ni(24)Co8 Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5μm),8.1μm and 590.2μ*** the temperature between 298 and773 K,the material with the large grain size of 590.2μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain *** material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%)due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement *** tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5μ*** deformation behavior of the Fe(41)Mn(25)Ni(24)Co8 Cr2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic *** activation energies for plastic flow for the materials with different grain sizes were similar as^199 kj/*** predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation *** sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85%due to it

关键词： high entropy alloys Grain size high temperature deformation mechanism Tensile behavior Grain boundary sliding

Effect of roll speed ratio on the texture and microstructural evolution of an FCC high-entropy alloy during differential speed rolling

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journal of Materials Science & Technology 2022年第16期111卷 152-166页

作者： h.T.jeong W.j.Kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

A very coarse-grained(335μm)Fe_(41)Mn_(25)Ni_(24)Co_(8)Cr_(2)high-entropy alloy with a single FCC phase was cold rolling to a 80%reduction in thickness using the differential speed rolling technique with various speed ratios(SRs)ranging between 1 and *** the SR was increased,the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear *** SR=4,the entire thickness of the sheet was covered with micro-shear bands,and ultrafine(sub)grains with a size of1.4μm were uniformly formed along the shear bands.A continuous dynamic recrystallization(CDRX)mechanism occurred during rolling,and a higher SR accelerated the CDRX *** conventional rolling(at SR=1),a brass{110}orientation texture with minor components of S{123}and Cu{112}orientations *** higher SRs,shear texture developed as the main type,while the development of rolling texture was *** microstructure at SR=4 obtained after annealing at973 K showed a fully recrystallized microstructure composed of a five times smaller grain size(4μm)with a higher intensity ofγfiber texture compared with that prepared by conventional *** samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after *** current results demonstrate that by using differential speed rolling with a high SR,one can achieve a significantly finer and more homogeneous microstructure,stronger shear texture,and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional *** strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening.

关键词： high entropy alloys Differential speed rolling Texture Grain refinement Strength Severe plastic deformation

Effects of grain size and Al addition on the activation volume and strain-rate sensitivity of CoCrFeMnNi high-entropy alloy

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journal of Materials Science & Technology 2023年第12期143卷 242-252页

作者： h.T.jeong W.j.Kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The activation volume(V∗)and strain-rate sensitivity exponent(m)of CoCrFeMnNi and Al_(0.5)CoCrFeMnNi high entropy alloys(hEAs)with various grain sizes(ranging between 2.4 and 356μm)were measured at different strain rates and strain levels at room *** the strain rate decreased,the plastic strain decreased,and the grain size increased,V∗*** enhanced solid-solution strengthening by addition of aluminum decreased V∗.The hassen plot was modified to capture the grain-size depen-dence of V∗by considering the grain-size dependence of the dislocation *** the plastic strain increased,the strain rate decreased,and the grain size decreased,m *** behavior of m could be quantitatively predicted by using equations derived for the grain-size-dependent V∗and flow *** difference in the grain-size dependence of m between conventional face centered cubic(FCC)metals and FCC hEAs over the nanograin size range could not be explained in terms of a relatively large hall-Petch slope of the FCC hEAs compared with that of the FCC conventional metals,but was explainable in terms of a substantially higher probability of activation of grain-boundary diffusion-controlled grain-boundary-sliding mechanism at nanograin sizes in the FCC conventional metals than in the FCC hEAs.

关键词： Grain size high entropy alloys Activation volume Strain-rate sensitivity Solid solution

Microstructures in a carburized steel after isothermal pearlitic treatment

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journal of Materials Science & Technology 2023年第29期160卷 66-75页

作者： j.Abraham Mathews h.Farahani j.Sietsma R.h.Petrov M.G.Mecozzi M.j.Santofimia Department of Materials Science and Engineering Delft University of TechnologyMekelweg 22628 CDDelftThe Netherlands Tata Steel Research&Development IJmuidenThe Netherlands Department of Electromechanical Systems and Metal EngineeringGhent UniversityTech Lane Ghent Science park-Campus A ZwijnaardeTechnologiepark 46Belgium

The influence of carbon concentration variations on pearlite formation(20 h at 600℃)in a case-carburized steel is *** resultant microstructure shows three distinct regions:carburized case,a transition region,and the original *** microstructural transition from the case to the core regions is observed to be relatively *** investigated region of the carburized case(0.9 wt.%C)con-tains two types of pearlite:ferrite+cementite and ferrite+M_(23)C_(6),where the pearlitic aggregate with M_(23)C_(6)shows faster formation *** kinetics of pearlite formation in the transition region(0.3 wt.%C)is very slow and is observed with only M_(23)C_(6)*** around 40%austenite decomposes into pearlite in the transition region,which,in comparison to the carburized case region of 0.9 wt.%C is a fraction that is lower by a factor of *** is absent in the investigated core region(0.16 wt.%C).The microstructure in this region is predominantly martensite and pro-eutectoid ferrite,with a fraction of ferrite well below the equilibrium *** formation in this region is limited by the redistribution of mainly Ni,Mn,and Cr,and their resulting solute drag effect on the austenite/ferrite interface.A ther-modynamic and kinetic argumentation of these observations is provided with the help of thermodynamic data,precipitation simulations,and a general mixed-mode Gibbs energy balance model.

关键词： Pearlite formation Carburized steel M 2_(3)C_(6)carbide Kinetics Solute drag