In this paper,some conditions which assure the compactly supported refinable distributions supported on a self-affine tile to be Lebesgue-Stieltjes measures or absolutely continuous measures with respect to Lebesgue-S...In this paper,some conditions which assure the compactly supported refinable distributions supported on a self-affine tile to be Lebesgue-Stieltjes measures or absolutely continuous measures with respect to Lebesgue-Stieltjes measures are given.展开更多
In this paper,the global and local linear independence of any compactly supported distributions by using time domain spaces,and of refinable vectors by invariant linear spaces are investigated.
Let M=(111-1).In this paper,an optimal upper bound estimateof the modules of Fourier transforms of M-refinable distributions is obtained by theintroduction of cycle related to M.
Let M be a d × d expansive matrix, and FL2（Ω） be a reducing subspace of L2（Rd）. This paper characterizes bounded measurable sets in Rd which are the supports of Fourier transforms of M-refinable frame functi...Let M be a d × d expansive matrix, and FL2（Ω） be a reducing subspace of L2（Rd）. This paper characterizes bounded measurable sets in Rd which are the supports of Fourier transforms of M-refinable frame functions. As applications, we derive the characterization of bounded measurable sets as the supports of Fourier transforms of FMRA （W-type FMRA） frame scaling functions and MRA （W-type MRA） scaling functions for FL2（Ω）, respectively. Some examples are also provided.展开更多
Suppose that f（x）=（f<sub>1</sub>（x）,....f<sub>r</sub>（x））<sup>T</sup>, x∈R<sup>d</sup> is a vector-valued function satisfying the refinement equation f（x）=∑&...Suppose that f（x）=（f<sub>1</sub>（x）,....f<sub>r</sub>（x））<sup>T</sup>, x∈R<sup>d</sup> is a vector-valued function satisfying the refinement equation f（x）=∑<sub> </sub>c<sub>k</sub> f（2x-k） with finite set of Z<sup>d</sup> and some r×r matricex c<sub>k</sub>. The requirements for f to have accuracy p are given in terms of the symbol function m（ξ）.展开更多
In this paper, the author at first develops a method to study convergence of the cascadealgorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), andthen applies the previous result on th...In this paper, the author at first develops a method to study convergence of the cascadealgorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), andthen applies the previous result on the convergence to characterizing compactly supportedrefinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriateinitial to guarantee the convergence of the cascade algorithm (see Theorem 4.2).展开更多
Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as...Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as massive by-product,contribute to greenhouse effects and pose environmental challenges.Thus,the pursuit of nitrogen fixation through carbon–neutral pathways under benign conditions is a frontier of scientific topics,with the harnessing of solar energy emerging as an enticing and viable option.This review delves into the refinement strategies for scale-up mild photocatalytic nitrogen fixation,fields ripe with potential for innovation.The narrative is centered on enhancing the intrinsic capabilities of catalysts to surmount current efficiency barriers.Key focus areas include the in-depth exploration of fundamental mechanisms underpinning photocatalytic procedures,rational element selection,and functional planning,state-of-the-art experimental protocols for understanding photo-fixation processes,valid photocatalytic activity evaluation,and the rational design of catalysts.Furthermore,the review offers a suite of forward-looking recommendations aimed at propelling the advancement of mild nitrogen photo-fixation.It scrutinizes the existing challenges and prospects within this burgeoning domain,aspiring to equip researchers with insightful perspectives that can catalyze the evolution of cutting-edge nitrogen fixation methodologies and steer the development of next-generation photocatalytic systems.展开更多
Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification ...Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification structure was further investigated.With adding 0.0023%La,the Al_(2)O_(3)·CaO·CaS inclusions were modified to the LaAlO_(3)·CaO·CaS inclusions.Additionally,the morphology tended to be more spherical,and the proportion of small-sized inclusions increased significantly from 77.8%to 93.5%.The large-sized inclusions were almost completely eliminated.Based on experimental results,a dynamical model elucidating the process of inclusion modification by La was developed.Furthermore,the ratio of equiaxed zone of the solidification structure increased from 22.9%to 31.0%,and the average primary dendrite arm spacing decreased significantly from 288.4 to 226.2μm.Two-dimensional lattice mismatch analysis results determined that LaAlO_(3)can serve as an effective heterogeneous nucleation core,leading to solidification structure refinement.The beneficial transformation of inclusions and refinement of solidification structure are conducive to the cold heading process of 40Cr steel.展开更多
Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can res...Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.展开更多
The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(...The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was the diffusion in the molten slag.The dissolution rate of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was affected by the composition and size of inclusion.The functional relationship between the dimensionless inclusion capacity(Zh)and the dimensionless dissolution rate(Ry)of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was calculated as Ry=2.10×10^(-6)Zh^(0.160),while it was Ry=2.10×10^(-6)Zh^(0.0087)for Al_(2)O_(3)-CaO complex inclusions.On this basis,the complete dissolution time and rate of the complex inclusions were calculated by using the function relation between the Zh and Ry numbers.展开更多
A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped C...A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.展开更多
High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.Hi...High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.High-purity indium was prepared by combining zone refining with vacuum distillation.Results show that the average removal efficiency of impurity Sb can approach 95%,while the removal efficiency of impurities Sn and Bi can reach over 95%,and the removal efficiency of Si,Fe,Ni,and Pb can reach over 85%.Ultimately,the amount of Sn and Sb impurities is reduced to 2.0 and 4.1μg/kg,respectively,and that of most impurities,including Fe,Ni,Pb,and Bi,is reduced to levels below the instrumental detection limit.The average impurity removal efficiency is 90.9%,and the indium purity reaches 7N9.展开更多
Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material stru...Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material structure simulation has become more and more perfect.This study employs numerical simulation to investigate the microstructure evolution of Al-Cu-Mg-Ag alloys during solidification with the aim of controlling its structure.The size distribution of Ti-containing particles in an Al-Ti-B master alloy was characterized via microstructure observation,serving as a basis for optimizing the nucleation density parameters for particles of varying radii in the phase field model.The addition of refiner inhibited the growth of dendrites and no longer produced coarse dendrites.With the increase of refiner,the grains gradually tended to form cellular morphology.The refined grains were about 100μm in size.Experimental validation of the simulated as-cast grain morphology was conducted.The samples were observed by metallographic microscope and scanning electron microscope.The addition of refiner had a significant effect on the refinement of the alloy,and the average grain size after refinement was also about 100μm.At the same time,the XRD phase identification of the alloy was carried out.The observation of the microstructure morphology under the scanning electron microscope showed that the precipitated phase was mainly concentrated on the grain boundary.The Al_(2)Cu accounted for about 5%,and the matrix phase FCC accounted for about 95%,which also corresponded well with the simulation results.展开更多
Generalizing wavelets by adding desired redundancy and flexibility,framelets(i.e.,wavelet frames)are of interest and importance in many applications such as image processing and numerical algorithms.Several key proper...Generalizing wavelets by adding desired redundancy and flexibility,framelets(i.e.,wavelet frames)are of interest and importance in many applications such as image processing and numerical algorithms.Several key properties of framelets are high vanishing moments for sparse multiscale representation,fast framelet transforms for numerical efficiency,and redundancy for robustness.However,it is a challenging problem to study and construct multivariate nonseparable framelets,mainly due to their intrinsic connections to factorization and syzygy modules of multivariate polynomial matrices.Moreover,all the known multivariate tight framelets derived from spline refinable scalar functions have only one vanishing moment,and framelets derived from refinable vector functions are barely studied yet in the literature.In this paper,we circumvent the above difficulties through the approach of quasi-tight framelets,which behave almost identically to tight framelets.Employing the popular oblique extension principle(OEP),from an arbitrary compactly supported M-refinable vector functionφwith multiplicity greater than one,we prove that we can always derive fromφa compactly supported multivariate quasi-tight framelet such that:(i)all the framelet generators have the highest possible order of vanishing moments;(ii)its associated fast framelet transform has the highest balancing order and is compact.For a refinable scalar functionφ(i.e.,its multiplicity is one),the above item(ii)often cannot be achieved intrinsically but we show that we can always construct a compactly supported OEP-based multivariate quasi-tight framelet derived fromφsatisfying item(i).We point out that constructing OEP-based quasi-tight framelets is closely related to the generalized spectral factorization of Hermitian trigonometric polynomial matrices.Our proof is critically built on a newly developed result on the normal form of a matrix-valued filter,which is of interest and importance in itself for greatly facilitating the study of refinable vector functions and multiwavelets/multiframelets.This paper provides a comprehensive investigation on OEP-based multivariate quasi-tight multiframelets and their associated framelet transforms with high balancing orders.This deepens our theoretical understanding of multivariate quasi-tight multiframelets and their associated fast multiframelet transforms.展开更多
In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each componen...In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each component function of a compactly supported refinable vector satisfying an inhomogeneous matrix refinement equation with finitely supported masks.展开更多
In this paper some properties of refinable functions and some relationships between the mask symbol and the refinable functions are studied. Especially, it is illustrated by examples that the linear spaces formed by t...In this paper some properties of refinable functions and some relationships between the mask symbol and the refinable functions are studied. Especially, it is illustrated by examples that the linear spaces formed by the translates over the lattice points of refinable functions may contain polynomial spaces of deg-ree higher than the smooth order of the corresponding refinable functions.展开更多
We study shift invariant spaces generated by refinable distributions. We classify the summation and the intersection of shift invariant spaces generated by refinable distributions,and prove that they are also shift in...We study shift invariant spaces generated by refinable distributions. We classify the summation and the intersection of shift invariant spaces generated by refinable distributions,and prove that they are also shift invariant spaces generated by refinable distributions.展开更多
To mitigate the harmful effects of Al_(2)O_(3) inclusions in steel,it is necessary to conduct comprehensive research on the mechanisms and kinetic laws of Al_(2)O_(3) inclusion modification by Ce.Combined with laborat...To mitigate the harmful effects of Al_(2)O_(3) inclusions in steel,it is necessary to conduct comprehensive research on the mechanisms and kinetic laws of Al_(2)O_(3) inclusion modification by Ce.Combined with laboratory experiments,first-principles calculations,and molecular dynamics simulations,the kinetic model of Ce modification for Al_(2)O_(3) inclusions was established.Based on first-principles calculations,differential charge analysis,density of states analysis,and adsorption energy analysis were performed on the transformation process from Al_(2)O_(3) to CeAlO_(3) at the atomic scale,and the microscopic transformation mechanism of inclusions at the atomic scale was obtained.Molecular dynamics simulations and the solution of mean square displacement function show that the diffusion coefficient for Ce atoms was 2.169×10^(−4) cm^(2)/s,which agreed well with experimental results.In this model,the rate-determining step is the diffusion of Ce atoms across Ce–Al–O inclusions.The relationship between the conversion rate,refining time,and initial radius was discussed.A refining time of 60 s can completely transform Al_(2)O_(3) inclusions less than 2.56μm into CeAlO_(3) inclusions,while refining time of 1200 s is sufficient to modify inclusions size below 11.47μm.展开更多
Humins,as a group of by-products formed through the condensation and coupling of fragment intermediates during lignocellulosic biomass refining,can cause numerous negative effects such as the wastage of carbon resourc...Humins,as a group of by-products formed through the condensation and coupling of fragment intermediates during lignocellulosic biomass refining,can cause numerous negative effects such as the wastage of carbon resources,clogging of reactor piping,deactivation of catalyst,and barriers to product separation.Elucidating the generation mechanism of humins,developing efficient inhibitors,and even utilizing them as a resource,both from the perspective of atom economy and safe production,constitutes a research endeavor replete with challenges and opportunities.Orbiting the critical issue of humins structure and its generation mechanism from cellulose and hemicellulose resources,the random condensation between intermediates such as 5-hydroxymethylfurfural,furfural,2,5-dioxo-6-hydroxyhexanal,and 1,2,4-benzenetriol etc.were systematically summarized.Additionally,the presence of lignin in real biorefining processes further promotes the formation of a special type of humins known as"pseudo-lignin".The influences of various factors,including raw materials,reaction temperature and time,acid-base environment,as well as solvent systems and catalysts,on the formation of humins were comprehensively analyzed.To minimize the formation of humins,the design of efficient solvent systems and catalysts is crucial.Furthermore,this review investigates the approaches to value-added applications of humins.The corresponding summary could provide guidance for the development of the humins chemistry.展开更多
文摘In this paper,some conditions which assure the compactly supported refinable distributions supported on a self-affine tile to be Lebesgue-Stieltjes measures or absolutely continuous measures with respect to Lebesgue-Stieltjes measures are given.
文摘In this paper,the global and local linear independence of any compactly supported distributions by using time domain spaces,and of refinable vectors by invariant linear spaces are investigated.
基金Supported by the Natural Science Foundation of Beijing(1013005)the Educational Committee Foundation of Beijing(01KJ-019)
文摘Let M=(111-1).In this paper,an optimal upper bound estimateof the modules of Fourier transforms of M-refinable distributions is obtained by theintroduction of cycle related to M.
基金Supported by Beijing Natural Science Foundation (No.1122008)the Scientific Research Common Programof Beijing Municipal Commission of Education (No.KM201110005030)
文摘Let M be a d × d expansive matrix, and FL2（Ω） be a reducing subspace of L2（Rd）. This paper characterizes bounded measurable sets in Rd which are the supports of Fourier transforms of M-refinable frame functions. As applications, we derive the characterization of bounded measurable sets as the supports of Fourier transforms of FMRA （W-type FMRA） frame scaling functions and MRA （W-type MRA） scaling functions for FL2（Ω）, respectively. Some examples are also provided.
文摘Suppose that f（x）=（f<sub>1</sub>（x）,....f<sub>r</sub>（x））<sup>T</sup>, x∈R<sup>d</sup> is a vector-valued function satisfying the refinement equation f（x）=∑<sub> </sub>c<sub>k</sub> f（2x-k） with finite set of Z<sup>d</sup> and some r×r matricex c<sub>k</sub>. The requirements for f to have accuracy p are given in terms of the symbol function m（ξ）.
文摘In this paper, the author at first develops a method to study convergence of the cascadealgorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), andthen applies the previous result on the convergence to characterizing compactly supportedrefinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriateinitial to guarantee the convergence of the cascade algorithm (see Theorem 4.2).
基金financially supported by the National Natural Science Foundation of China(No.21675131)the Volkswagen Foundation(Freigeist Fellowship No.89592)+1 种基金the Natural Science Foundation of Chongqing(No.2020jcyj-zdxmX0003,CSTB2023NSCQ-MSX0924)the National Research Foundation,Singapore,and A*STAR(Agency for Science Technology and Research)under its LCER Phase 2 Programme Hydrogen&Emerging Technologies FI,Directed Hydrogen Programme(Award No.U2305D4003).
文摘Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as massive by-product,contribute to greenhouse effects and pose environmental challenges.Thus,the pursuit of nitrogen fixation through carbon–neutral pathways under benign conditions is a frontier of scientific topics,with the harnessing of solar energy emerging as an enticing and viable option.This review delves into the refinement strategies for scale-up mild photocatalytic nitrogen fixation,fields ripe with potential for innovation.The narrative is centered on enhancing the intrinsic capabilities of catalysts to surmount current efficiency barriers.Key focus areas include the in-depth exploration of fundamental mechanisms underpinning photocatalytic procedures,rational element selection,and functional planning,state-of-the-art experimental protocols for understanding photo-fixation processes,valid photocatalytic activity evaluation,and the rational design of catalysts.Furthermore,the review offers a suite of forward-looking recommendations aimed at propelling the advancement of mild nitrogen photo-fixation.It scrutinizes the existing challenges and prospects within this burgeoning domain,aspiring to equip researchers with insightful perspectives that can catalyze the evolution of cutting-edge nitrogen fixation methodologies and steer the development of next-generation photocatalytic systems.
基金the National Natural Science Foundation of China(52004180,52204350)the China Postdoctoral Science Foundation(2020M683706XB)the Research Project Supported by Shanxi Scholarship Council of China(2023-080).
文摘Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions.The impact of La on the inclusion modification was studied,and its influence on the solidification structure was further investigated.With adding 0.0023%La,the Al_(2)O_(3)·CaO·CaS inclusions were modified to the LaAlO_(3)·CaO·CaS inclusions.Additionally,the morphology tended to be more spherical,and the proportion of small-sized inclusions increased significantly from 77.8%to 93.5%.The large-sized inclusions were almost completely eliminated.Based on experimental results,a dynamical model elucidating the process of inclusion modification by La was developed.Furthermore,the ratio of equiaxed zone of the solidification structure increased from 22.9%to 31.0%,and the average primary dendrite arm spacing decreased significantly from 288.4 to 226.2μm.Two-dimensional lattice mismatch analysis results determined that LaAlO_(3)can serve as an effective heterogeneous nucleation core,leading to solidification structure refinement.The beneficial transformation of inclusions and refinement of solidification structure are conducive to the cold heading process of 40Cr steel.
基金supported by the National Natural Science Foundation of China(No.51871155).
文摘Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.
基金support from the National Key R&D Program(No.2023YFB3709900)the National Natural Science Foundation of China(Grant No.U22A20171)+1 种基金the High Steel Center at the North China University of Technologythe University of Science and Technology Beijing,China.
文摘The dissolution behavior of complex inclusions in refining slag was studied using confocal laser scanning microscope.Based on the dissolution curve of complex inclusions,the main rate-limiting link of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was the diffusion in the molten slag.The dissolution rate of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was affected by the composition and size of inclusion.The functional relationship between the dimensionless inclusion capacity(Zh)and the dimensionless dissolution rate(Ry)of CaO-SiO_(2)-Al_(2)O_(3)complex inclusions was calculated as Ry=2.10×10^(-6)Zh^(0.160),while it was Ry=2.10×10^(-6)Zh^(0.0087)for Al_(2)O_(3)-CaO complex inclusions.On this basis,the complete dissolution time and rate of the complex inclusions were calculated by using the function relation between the Zh and Ry numbers.
基金supported by the National Key R&D Program of China(No.2019YFA0209902)the Natural Science Foundation of China(Nos.52071326,52192593,51601204)+1 种基金the NSFC Basic Science Center Program for Multiscale Problems in Nonlinear Mechanics(No.11988102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.
基金National Key Research and Development Program of China(2023YFC2907904)National Natural Science Foundation of China(52374364)。
文摘High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.High-purity indium was prepared by combining zone refining with vacuum distillation.Results show that the average removal efficiency of impurity Sb can approach 95%,while the removal efficiency of impurities Sn and Bi can reach over 95%,and the removal efficiency of Si,Fe,Ni,and Pb can reach over 85%.Ultimately,the amount of Sn and Sb impurities is reduced to 2.0 and 4.1μg/kg,respectively,and that of most impurities,including Fe,Ni,Pb,and Bi,is reduced to levels below the instrumental detection limit.The average impurity removal efficiency is 90.9%,and the indium purity reaches 7N9.
文摘Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material structure simulation has become more and more perfect.This study employs numerical simulation to investigate the microstructure evolution of Al-Cu-Mg-Ag alloys during solidification with the aim of controlling its structure.The size distribution of Ti-containing particles in an Al-Ti-B master alloy was characterized via microstructure observation,serving as a basis for optimizing the nucleation density parameters for particles of varying radii in the phase field model.The addition of refiner inhibited the growth of dendrites and no longer produced coarse dendrites.With the increase of refiner,the grains gradually tended to form cellular morphology.The refined grains were about 100μm in size.Experimental validation of the simulated as-cast grain morphology was conducted.The samples were observed by metallographic microscope and scanning electron microscope.The addition of refiner had a significant effect on the refinement of the alloy,and the average grain size after refinement was also about 100μm.At the same time,the XRD phase identification of the alloy was carried out.The observation of the microstructure morphology under the scanning electron microscope showed that the precipitated phase was mainly concentrated on the grain boundary.The Al_(2)Cu accounted for about 5%,and the matrix phase FCC accounted for about 95%,which also corresponded well with the simulation results.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)(Grant No.RGPIN-2019-04276)。
文摘Generalizing wavelets by adding desired redundancy and flexibility,framelets(i.e.,wavelet frames)are of interest and importance in many applications such as image processing and numerical algorithms.Several key properties of framelets are high vanishing moments for sparse multiscale representation,fast framelet transforms for numerical efficiency,and redundancy for robustness.However,it is a challenging problem to study and construct multivariate nonseparable framelets,mainly due to their intrinsic connections to factorization and syzygy modules of multivariate polynomial matrices.Moreover,all the known multivariate tight framelets derived from spline refinable scalar functions have only one vanishing moment,and framelets derived from refinable vector functions are barely studied yet in the literature.In this paper,we circumvent the above difficulties through the approach of quasi-tight framelets,which behave almost identically to tight framelets.Employing the popular oblique extension principle(OEP),from an arbitrary compactly supported M-refinable vector functionφwith multiplicity greater than one,we prove that we can always derive fromφa compactly supported multivariate quasi-tight framelet such that:(i)all the framelet generators have the highest possible order of vanishing moments;(ii)its associated fast framelet transform has the highest balancing order and is compact.For a refinable scalar functionφ(i.e.,its multiplicity is one),the above item(ii)often cannot be achieved intrinsically but we show that we can always construct a compactly supported OEP-based multivariate quasi-tight framelet derived fromφsatisfying item(i).We point out that constructing OEP-based quasi-tight framelets is closely related to the generalized spectral factorization of Hermitian trigonometric polynomial matrices.Our proof is critically built on a newly developed result on the normal form of a matrix-valued filter,which is of interest and importance in itself for greatly facilitating the study of refinable vector functions and multiwavelets/multiframelets.This paper provides a comprehensive investigation on OEP-based multivariate quasi-tight multiframelets and their associated framelet transforms with high balancing orders.This deepens our theoretical understanding of multivariate quasi-tight multiframelets and their associated fast multiframelet transforms.
基金Supported by National Natural Science Foundation of China (Grant Nos. 10771190, 10471123)
文摘In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each component function of a compactly supported refinable vector satisfying an inhomogeneous matrix refinement equation with finitely supported masks.
文摘In this paper some properties of refinable functions and some relationships between the mask symbol and the refinable functions are studied. Especially, it is illustrated by examples that the linear spaces formed by the translates over the lattice points of refinable functions may contain polynomial spaces of deg-ree higher than the smooth order of the corresponding refinable functions.
基金supported by National Natural Science Foundation of China (Grant No. 10871180)Projects of International Cooperation and Exchanges NSFC-NSF (Grant No. 10911120394)
文摘We study shift invariant spaces generated by refinable distributions. We classify the summation and the intersection of shift invariant spaces generated by refinable distributions,and prove that they are also shift invariant spaces generated by refinable distributions.
基金supported by the National Natural Science Foundation of China(Nos.52064011,52274331 and 52264041)Guizhou Provincial Basic Research Program(Natural Science)(Nos.ZK[2021]258 and ZK[2023]Zhongdian 020)+6 种基金Guizhou Provincial Key Technology R&D Program(No.[2021]342)Guizhou Provincial Program on Commercialization of Scientific and Technological Achievements(No.[2022]089)supported by Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(No.SKLASS 2023-08)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)supported by State Key Laboratory of Advanced Metallurgy(No.K23-04)China Postdoctoral Science Foundation(No.2023MD744232)Key Research Projects in Higher Education Institutions of Henan Province(No.24B450003).
文摘To mitigate the harmful effects of Al_(2)O_(3) inclusions in steel,it is necessary to conduct comprehensive research on the mechanisms and kinetic laws of Al_(2)O_(3) inclusion modification by Ce.Combined with laboratory experiments,first-principles calculations,and molecular dynamics simulations,the kinetic model of Ce modification for Al_(2)O_(3) inclusions was established.Based on first-principles calculations,differential charge analysis,density of states analysis,and adsorption energy analysis were performed on the transformation process from Al_(2)O_(3) to CeAlO_(3) at the atomic scale,and the microscopic transformation mechanism of inclusions at the atomic scale was obtained.Molecular dynamics simulations and the solution of mean square displacement function show that the diffusion coefficient for Ce atoms was 2.169×10^(−4) cm^(2)/s,which agreed well with experimental results.In this model,the rate-determining step is the diffusion of Ce atoms across Ce–Al–O inclusions.The relationship between the conversion rate,refining time,and initial radius was discussed.A refining time of 60 s can completely transform Al_(2)O_(3) inclusions less than 2.56μm into CeAlO_(3) inclusions,while refining time of 1200 s is sufficient to modify inclusions size below 11.47μm.
文摘Humins,as a group of by-products formed through the condensation and coupling of fragment intermediates during lignocellulosic biomass refining,can cause numerous negative effects such as the wastage of carbon resources,clogging of reactor piping,deactivation of catalyst,and barriers to product separation.Elucidating the generation mechanism of humins,developing efficient inhibitors,and even utilizing them as a resource,both from the perspective of atom economy and safe production,constitutes a research endeavor replete with challenges and opportunities.Orbiting the critical issue of humins structure and its generation mechanism from cellulose and hemicellulose resources,the random condensation between intermediates such as 5-hydroxymethylfurfural,furfural,2,5-dioxo-6-hydroxyhexanal,and 1,2,4-benzenetriol etc.were systematically summarized.Additionally,the presence of lignin in real biorefining processes further promotes the formation of a special type of humins known as"pseudo-lignin".The influences of various factors,including raw materials,reaction temperature and time,acid-base environment,as well as solvent systems and catalysts,on the formation of humins were comprehensively analyzed.To minimize the formation of humins,the design of efficient solvent systems and catalysts is crucial.Furthermore,this review investigates the approaches to value-added applications of humins.The corresponding summary could provide guidance for the development of the humins chemistry.
