Against the background of the integration of the digital economy and industrial intelligence,AI technology has become the core support for the logistics industry to reduce costs,improve efficiency,and break through de...Against the background of the integration of the digital economy and industrial intelligence,AI technology has become the core support for the logistics industry to reduce costs,improve efficiency,and break through development bottlenecks.This paper constructs a research framework of“Application Scenarios-Transformation Mechanism-Challenges-Development Path,”systematically analyzing the application value and practical issues of AI in the logistics industry.The core applications of AI are concentrated in three scenarios:intelligent customer service,logistics data analysis and decision optimization,and intelligent inventory management.Through process automation replacement,service model upgrading,and data-driven decision-making,it achieves a systematic transformation of industry operational efficiency improvement,customer experience optimization,and decision-making model transformation.At the same time,AI applications still face practical challenges such as insufficient technical integration compatibility,data security and privacy protection risks,and talent structure adaptation gaps.In the future,the logistics industry needs to fully release the value of AI technology by deepening the integration of AI with cross-technologies,promoting green and flexible development.展开更多
Transformation Mechamism of RE slag containing fluoride was analyzed by using Flood’s Model.The ef-fects of slag basicity, TiO_2 content, CaF_2 content and atom ratio of O/Si+Ti+2Al on transformation of slagcontainin...Transformation Mechamism of RE slag containing fluoride was analyzed by using Flood’s Model.The ef-fects of slag basicity, TiO_2 content, CaF_2 content and atom ratio of O/Si+Ti+2Al on transformation of slagcontaining fluoride were also discussed.展开更多
Ecological vulnerability refers to the degree of ecosystem disturbance,system damage,and the ability of system restoration.Although case-specific evaluations of ecological vulnerability are progressing rapidly,they ha...Ecological vulnerability refers to the degree of ecosystem disturbance,system damage,and the ability of system restoration.Although case-specific evaluations of ecological vulnerability are progressing rapidly,they have been carried out mainly in areas with intensive human activities or in harsh natural environments.Using the Web of ScienceTM core collection,this review paper summarized studies on ecological vulnerability published from 2000 to 2022 and analyzed in depth major case studies.It was found that traditional ecological vulnerability research has been addressed largely in terms of assessment models,data processing models,and analysis of influencing factors,however there was a lack of research on the process of vulnerability transformation.Because the vulnerability transformation in a hierarchical vulnerability index system is regulated by multiple factors in a heterogeneous region,it is urgent to understand how the ecological vulnerability in a region evolves from one level to another over time.Therefore this paper put forward the new perspective of research,i.e.,applying quantitative analysis to identification of regulating factors and exploring the mechanisms of ecological vulnerability transformation.This new perspective could assist in monitoring the complex spatiotemporal changes in ecological vulnerability and taking necessary measures to prevent from decline of ecological stability.展开更多
This article discusses the coexistence of prostate adenocarcinoma and prostate urothelial carcinoma.Combining existing literature and research results,the potential mechanisms of the co-occurrence of these two cancers...This article discusses the coexistence of prostate adenocarcinoma and prostate urothelial carcinoma.Combining existing literature and research results,the potential mechanisms of the co-occurrence of these two cancers are explored,including the role of androgen receptor,gene mutations,and their complex interactions in cell signaling pathways,etc.Also,the hypothesis of prostate cancer transformation into urothelial carcinoma is explained from some perspectives,including tumor multipotent stem cell differentiation,epithelial-mesenchymal transition,mesenchymal-epithelial transition,and other mechanisms.Ultimately,the goal is to provide more accurate diagnoses and more personalized treatments in clinical practice,as well as to lay the foundation for improving patient prognoses in the future.展开更多
High entropy alloys(HEAs)have attracted much attention for their excellent mechanical properties stem-ming from diverse deformation mechanisms.Particularly,face-centered cubic(FCC)to body-centered cu-bic(BCC)martensit...High entropy alloys(HEAs)have attracted much attention for their excellent mechanical properties stem-ming from diverse deformation mechanisms.Particularly,face-centered cubic(FCC)to body-centered cu-bic(BCC)martensitic transformation is crucial for enhancing the strength and plasticity of HEAs,partic-ularly at cryogenic temperatures.However,the fundamental atomic mechanism underlying martensitic transformation remains elusive,and the impact of martensitic transformation on the mechanical prop-erties of HEAs at room temperature is unknown.Here,we report in situ atomic-scale observation of a reversible martensitic transformation from FCC to body-centered tetragonal(BCT)and ultimately back to FCC in the nanostructured CrMnFeCoNi HEA at room temperature under deformation.This martensitic transformation is completed by the synergistic action of 90°partial dislocations slip on(111)FCC plane and atom shuffling,involving the periodic arrangement and slip of two 90°half Shockley partial disloca-tions a/12[112](111)and one 90°Shockley partial dislocation-a/6[112](111)on three successive(111)FCC atomic planes.Additionally,the reversible phase transformation induced by high stress dissipates strain energies and hinders crack propagation,thereby enhancing the fracture toughness of HEAs.Our findings contribute to a deeper comprehension of the martensitic transformation mechanisms in HEAs,offering valuable insights for improving their mechanical properties.展开更多
The aged and quenched microstructures of both alloys, Ti-42at-%Al and Ti-45at -%Al,homogenized in the disordered single phase field. were investigated And the results show that the quinched microstructure is a supersa...The aged and quenched microstructures of both alloys, Ti-42at-%Al and Ti-45at -%Al,homogenized in the disordered single phase field. were investigated And the results show that the quinched microstructure is a supersaturated single phase of ordered 22. When the supersaturated phase is aged in the two phase range at 1273 and 1373 K, it will transform to a lamellar microstructure of γ+α2. with a discontinuous decomposition mechanism in Ti-42at-%Al alloy and a semicontinuous decomposition mechanism in T1-45at-%Al alloy. With the methods of quantitative metallograph examination and X-ray diffraction analysis. the relationship between the amount of γ, phase precipitation and the time of isothermal transformation is agreed展开更多
Amounts of lithium-containing salt lake brine resources are widely distributed in the four provinces named Qinghai,Tibet,Inner Mongolia and Xinjiang province,especially the salt lakes in Qinghai-Tibet Plateau are abun...Amounts of lithium-containing salt lake brine resources are widely distributed in the four provinces named Qinghai,Tibet,Inner Mongolia and Xinjiang province,especially the salt lakes in Qinghai-Tibet Plateau are abundant of展开更多
The peculiarities of energy dissipation transferred by solitary waves on defects such as freesurface, grain boundary, region with high concentration of vacancies are studied. One of theways of description of the long ...The peculiarities of energy dissipation transferred by solitary waves on defects such as freesurface, grain boundary, region with high concentration of vacancies are studied. One of theways of description of the long range effect taking place at ion implantation in metallic materialsis suggested.展开更多
A diagnostic study is performed in the paper on the process of typhoon Norris (1980) transforming into an ex-tratropical cyclone after its landing over Southeast China. The main findings are as follows:The changes of ...A diagnostic study is performed in the paper on the process of typhoon Norris (1980) transforming into an ex-tratropical cyclone after its landing over Southeast China. The main findings are as follows:The changes of kinetic energy are mainly attributed to the generation due to non-divergent wind. During the early stage of the typhoon landing, there exits only a small quantity of kinetic energy exchanging with the environment. And after it is transformed into an extratropical cyclone, a large amount of kinetic energy is exported from the system toward the environment.The horizontal and vertical flux-divergence terms of eddy available potenlial energy are the prominent sinks in the budgets of eddy kinetic energy. The generations of eddy kinetic energy due to both the barotropic and baroclinic processes are source terms. The former is remarkable during the initial stage. But after the depression is transformed into an extratropical cyclone, the roles of the generation by the barotropic and baroclinic processes are reversed, 1. e. , the latter has become more significant than the former.Diabatic heating is the most dominant heat source. The terms of vertical heat flux by cumulus and large-scale motion are the major sinks. And the latter is prominent after the system is transformed into an extratropical cycfone.展开更多
According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rat...According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.展开更多
Under the vision of development for the new era,China has entered a stage of high-quality economic development and an important window period in which we have the conditions and ability to address the prominent issue ...Under the vision of development for the new era,China has entered a stage of high-quality economic development and an important window period in which we have the conditions and ability to address the prominent issue of economic development and ecological protection in a coordinated way.However,all kinds of environmental benchmark values in China are lacking and need to be constantly supplemented and improved.Therefore,exploring and putting forward a simple and efficient method for the transformation of environmental criteria into environmental standards is an important basis for the rapid establishment of relevant environmental criteria system and the effective promotion of the development of environmental standards system towards a scientific and reasonable direction.In this paper,the water environment is taken as the research object.By analyzing the research progress of environmental criteria and standards at home and abroad,and the foreign method of transforming environmental criteria into environmental standards,combined with the problems faced in the process of transforming environmental criteria into environmental standards in China,an effective method to transform China's environmental criteria into environmental standards is analyzed.After analysis and comparison,it is found that the pollution reduction accounting method could achieve their simple and efficient conversion.Under the premise of obtaining environmental criteria for certain pollutants,environmental criteria for certain pollutants could be obtained by distributing pollutants reduction costs,and accounting economic benefits after reaching standard,thus obtaining the environmental standard of this type of pollutant,which provides reference to determine the environmental standard limits of such pollutants.展开更多
The reduction of high-chromium vanadium–titanium magnetite as a typical titanomagnetite containing 0.95wt% V2O5 and 0.61wt% Cr2O3 by H2–CO–CO2 gas mixtures was investigated from 1223 to 1373 K. Both the reduction d...The reduction of high-chromium vanadium–titanium magnetite as a typical titanomagnetite containing 0.95wt% V2O5 and 0.61wt% Cr2O3 by H2–CO–CO2 gas mixtures was investigated from 1223 to 1373 K. Both the reduction degree and reduction rate increase with increasing temperature and increasing hydrogen content. At a temperature of 1373 K, an H2/CO ratio of 5/2 by volume, and a reduction time of 40 min, the degree of reduction reaches 95%. The phase transformation during reduction is hypothesized to proceed as follows： Fe2O3 → Fe3O4 → FeO → Fe; Fe9 TiO 15 ＋ Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeT iO 3 → TiO 2;（Cr0.15V0.85）2O3 → Fe2VO4; and Cr1.3Fe0.7O3 → FeC r2O4. The reduction is controlled by the mixed internal diffusion and interfacial reaction at the initial stage; however, the interfacial reaction is dominant. As the reduction proceeds, the internal diffusion becomes the controlling step.展开更多
To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,t...To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.展开更多
The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity（TRIP） steels with polygonal ferrit...The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity（TRIP） steels with polygonal ferrite matrix, but rarely studied in bainitic TRIP steels. The aim of the present study is to properly investigate the effect of Al and Si on bainite transformation, microstructure and mechanical properties in bainitic steels in order to provide guidelines for the alloying design as a function of process parameters for the 3 rd generation advanced high strength steels（AHSS）. It is shown from the dilatometry study,microstructural investigations and tensile properties measurements that the Al addition results in an acceleration whereas Si addition leads to a retardation in bainite transformation kinetics. The addition of Al retards the decomposition of austenite into pearlite and carbides at holding temperatures higher than450℃ whereas Si retards the decomposition of austenite into carbides at temperatures lower than 450℃.Consequently, the Al-added bainitic steel has a better strength-elongation combination at bainitic holding temperatures higher than 450℃ while Si-added steel has a better strength-elongation combination at temperatures lower than 450℃. The higher yield strength of Al-added steel is mainly attributed to its finer bainitic lath. The higher tensile strength of Si-added steel is not only related to the stronger contribution of Si on work hardening during deformation, but also due to the higher volume fraction of martensite or martensite/austenite（MA） blocks in all heat treatment conditions, as well as the lower mechanical stability of retained austenite in this steel.展开更多
Based on our previous paper (Commun.Theor.Phys.39 (2003) 417) we derive the convolution theoremof fractional Fourier transformation in the context of quantum mechanics,which seems a convenient and neat way.Generalizat...Based on our previous paper (Commun.Theor.Phys.39 (2003) 417) we derive the convolution theoremof fractional Fourier transformation in the context of quantum mechanics,which seems a convenient and neat way.Generalization of this method to the complex fractional Fourier transformation case is also possible.展开更多
In order to realize the small error attitude transformation of a free floating space robot,a new method of three degrees of freedom（ DOF） attitude transformation was proposed for the space robot using a bionic joint...In order to realize the small error attitude transformation of a free floating space robot,a new method of three degrees of freedom（ DOF） attitude transformation was proposed for the space robot using a bionic joint. A general kinematic model of the space robot was established based on the law of linear and angular momentum conservation. A combinational joint model was established combined with bionic joint and closed motion. The attitude transformation of planar,two DOF and three DOF is analyzed and simulated by the model,and it is verified that the feasibility of attitude transformation in three DOF space. Finally,the specific scheme of disturbance elimination in attitude transformation is presented and simulation results are obtained.Therefore,the range of application field of the bionic joint model has been expanded.展开更多
TX-80 low-transformation-temperature(LTT)welding wire was used to replace the traditional ER 307Si welding wire to realize the connection of 22SiMn2TiB armor steel in manual overlay welding.The previously existing iss...TX-80 low-transformation-temperature(LTT)welding wire was used to replace the traditional ER 307Si welding wire to realize the connection of 22SiMn2TiB armor steel in manual overlay welding.The previously existing issues,such as welding cracks,large welding deformation,and severe welding residual stress,were solved to ensure good strength and ductility requirements.In particular,with the same welding conditions,TX-80 LTT wire eliminates welding cracks.It reduces the welding deformation no matter the base pretreatment of pre-setting angle or no pre-setting angle.By comparison,it was found that the microstructure at the TX-80 weld is mainly composed of martensite and a small amount of retained austenite.In contrast,the microstructure of the ER 307Si weld consists of a large amount of austenite and a small amount of skeleton-like ferrite.The variation trend of residual stress and microhardness from the weld to the base were investigated and compared with the mechanical properties of base materials.The TX-80 and the ER 307Si tensile samples elongation is 6.76%and 6.01%,while the ultimate tensile strengths are 877 and 667 MPa,respectively.The average impact toughness at room temperature of the ER 307Si weld is 143.9 J/cm^(2),much higher than that of the TX-80 weld,which is only 36.7 J/cm^(2).The relationship between impact and tensile properties with microstructure species and distribution was established.In addition,the fracture surface of the tensile and the impact samples was observed and analyzed.Deeper dimples,fewer pores,larger radiation zone,and shear lips of TX-80 samples indicate better tensile ductility and worse impact toughness than those of ER 307Si weld.展开更多
304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained（NG/UFG）structure.Transmission electron microscopy,electro...304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained（NG/UFG）structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline（60-100 nm）and ultrafine（100-500 nm）grains,submicron size（500-1000 nm）grains and micron size（〉1000 nm）grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test.展开更多
Exchange rate functions under systems of centrallyplanned economy and market economy are quite different,and the mechanism to determine such exchange rate is alsodifferent. To adopt a socialist market economic system ...Exchange rate functions under systems of centrallyplanned economy and market economy are quite different,and the mechanism to determine such exchange rate is alsodifferent. To adopt a socialist market economic system inChina, the exchange rate mechanism of Renminbi must bethoroughly transformed. To accomplish this goal, I believethere are three problems that must be solved: first,展开更多
In this paper,including some partial differential equations with a number of independent variables, which can he reduced by the infinitesimal form of the group, we obtain the theory of similarity transformation and it...In this paper,including some partial differential equations with a number of independent variables, which can he reduced by the infinitesimal form of the group, we obtain the theory of similarity transformation and its application of the second order nonlinear partial differential equations which have two independent variables and two dependent variables in mechanics.展开更多
基金funded by the 2025 Municipal Education Science Planning Project(202418966)the 2024 University Research Project of the Guangzhou Municipal Education Bureau(2024312155,2024312416)+2 种基金the 2024 Guangzhou Higher Education Teaching Quality and Teaching Reform Project(2024XWSJJD008)Project of the Department of Education of Guangdong Province(2022WTSCX089)Guangdong Provincial Department of Education General Higher Education Accreditation Research Project(2022WTSCX090).
文摘Against the background of the integration of the digital economy and industrial intelligence,AI technology has become the core support for the logistics industry to reduce costs,improve efficiency,and break through development bottlenecks.This paper constructs a research framework of“Application Scenarios-Transformation Mechanism-Challenges-Development Path,”systematically analyzing the application value and practical issues of AI in the logistics industry.The core applications of AI are concentrated in three scenarios:intelligent customer service,logistics data analysis and decision optimization,and intelligent inventory management.Through process automation replacement,service model upgrading,and data-driven decision-making,it achieves a systematic transformation of industry operational efficiency improvement,customer experience optimization,and decision-making model transformation.At the same time,AI applications still face practical challenges such as insufficient technical integration compatibility,data security and privacy protection risks,and talent structure adaptation gaps.In the future,the logistics industry needs to fully release the value of AI technology by deepening the integration of AI with cross-technologies,promoting green and flexible development.
文摘Transformation Mechamism of RE slag containing fluoride was analyzed by using Flood’s Model.The ef-fects of slag basicity, TiO_2 content, CaF_2 content and atom ratio of O/Si+Ti+2Al on transformation of slagcontaining fluoride were also discussed.
基金This research was funded by Shaanxi Science and Technology Department(2022JQ-282)National Natural Science Foundation of China(42007415)。
文摘Ecological vulnerability refers to the degree of ecosystem disturbance,system damage,and the ability of system restoration.Although case-specific evaluations of ecological vulnerability are progressing rapidly,they have been carried out mainly in areas with intensive human activities or in harsh natural environments.Using the Web of ScienceTM core collection,this review paper summarized studies on ecological vulnerability published from 2000 to 2022 and analyzed in depth major case studies.It was found that traditional ecological vulnerability research has been addressed largely in terms of assessment models,data processing models,and analysis of influencing factors,however there was a lack of research on the process of vulnerability transformation.Because the vulnerability transformation in a hierarchical vulnerability index system is regulated by multiple factors in a heterogeneous region,it is urgent to understand how the ecological vulnerability in a region evolves from one level to another over time.Therefore this paper put forward the new perspective of research,i.e.,applying quantitative analysis to identification of regulating factors and exploring the mechanisms of ecological vulnerability transformation.This new perspective could assist in monitoring the complex spatiotemporal changes in ecological vulnerability and taking necessary measures to prevent from decline of ecological stability.
文摘This article discusses the coexistence of prostate adenocarcinoma and prostate urothelial carcinoma.Combining existing literature and research results,the potential mechanisms of the co-occurrence of these two cancers are explored,including the role of androgen receptor,gene mutations,and their complex interactions in cell signaling pathways,etc.Also,the hypothesis of prostate cancer transformation into urothelial carcinoma is explained from some perspectives,including tumor multipotent stem cell differentiation,epithelial-mesenchymal transition,mesenchymal-epithelial transition,and other mechanisms.Ultimately,the goal is to provide more accurate diagnoses and more personalized treatments in clinical practice,as well as to lay the foundation for improving patient prognoses in the future.
基金the Natural Science Foundation of China(Nos.52173224,52130105)the Natural Science Foundation of Shanghai(No.21ZR1431200)+2 种基金Shanghai Jiao Tong University-JA Solar New Energy Materials Joint Research Center.Shufen Chu is supported by the China Postdoctoral Science Foundation(No.2023M742218)Fan Zhang is supported by the National Key Lab-oratory Foundation of Science and Technology on Materials under Shock and Impact(No.WDZC2022-1)the National Natural Science Foundation of China((No.52271141).
文摘High entropy alloys(HEAs)have attracted much attention for their excellent mechanical properties stem-ming from diverse deformation mechanisms.Particularly,face-centered cubic(FCC)to body-centered cu-bic(BCC)martensitic transformation is crucial for enhancing the strength and plasticity of HEAs,partic-ularly at cryogenic temperatures.However,the fundamental atomic mechanism underlying martensitic transformation remains elusive,and the impact of martensitic transformation on the mechanical prop-erties of HEAs at room temperature is unknown.Here,we report in situ atomic-scale observation of a reversible martensitic transformation from FCC to body-centered tetragonal(BCT)and ultimately back to FCC in the nanostructured CrMnFeCoNi HEA at room temperature under deformation.This martensitic transformation is completed by the synergistic action of 90°partial dislocations slip on(111)FCC plane and atom shuffling,involving the periodic arrangement and slip of two 90°half Shockley partial disloca-tions a/12[112](111)and one 90°Shockley partial dislocation-a/6[112](111)on three successive(111)FCC atomic planes.Additionally,the reversible phase transformation induced by high stress dissipates strain energies and hinders crack propagation,thereby enhancing the fracture toughness of HEAs.Our findings contribute to a deeper comprehension of the martensitic transformation mechanisms in HEAs,offering valuable insights for improving their mechanical properties.
文摘The aged and quenched microstructures of both alloys, Ti-42at-%Al and Ti-45at -%Al,homogenized in the disordered single phase field. were investigated And the results show that the quinched microstructure is a supersaturated single phase of ordered 22. When the supersaturated phase is aged in the two phase range at 1273 and 1373 K, it will transform to a lamellar microstructure of γ+α2. with a discontinuous decomposition mechanism in Ti-42at-%Al alloy and a semicontinuous decomposition mechanism in T1-45at-%Al alloy. With the methods of quantitative metallograph examination and X-ray diffraction analysis. the relationship between the amount of γ, phase precipitation and the time of isothermal transformation is agreed
基金Financial support from the State Surface Project of National Natural Science of China (21276194)the Specialized Research Fund for the Doctoral Program of Chinese Higher Education (20101208110003)the Key Pillar Program of Tianjin Municipal Science and Technology (11ZCKGX02800)
文摘Amounts of lithium-containing salt lake brine resources are widely distributed in the four provinces named Qinghai,Tibet,Inner Mongolia and Xinjiang province,especially the salt lakes in Qinghai-Tibet Plateau are abundant of
文摘The peculiarities of energy dissipation transferred by solitary waves on defects such as freesurface, grain boundary, region with high concentration of vacancies are studied. One of theways of description of the long range effect taking place at ion implantation in metallic materialsis suggested.
文摘A diagnostic study is performed in the paper on the process of typhoon Norris (1980) transforming into an ex-tratropical cyclone after its landing over Southeast China. The main findings are as follows:The changes of kinetic energy are mainly attributed to the generation due to non-divergent wind. During the early stage of the typhoon landing, there exits only a small quantity of kinetic energy exchanging with the environment. And after it is transformed into an extratropical cyclone, a large amount of kinetic energy is exported from the system toward the environment.The horizontal and vertical flux-divergence terms of eddy available potenlial energy are the prominent sinks in the budgets of eddy kinetic energy. The generations of eddy kinetic energy due to both the barotropic and baroclinic processes are source terms. The former is remarkable during the initial stage. But after the depression is transformed into an extratropical cyclone, the roles of the generation by the barotropic and baroclinic processes are reversed, 1. e. , the latter has become more significant than the former.Diabatic heating is the most dominant heat source. The terms of vertical heat flux by cumulus and large-scale motion are the major sinks. And the latter is prominent after the system is transformed into an extratropical cycfone.
文摘According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.
基金Supported by Research on Water Quality Criteria for Aquatic Organism Protection and Water Quality Standards for Optimal Control of Pollutants in the Baiyangdian Basin(20374204D).
文摘Under the vision of development for the new era,China has entered a stage of high-quality economic development and an important window period in which we have the conditions and ability to address the prominent issue of economic development and ecological protection in a coordinated way.However,all kinds of environmental benchmark values in China are lacking and need to be constantly supplemented and improved.Therefore,exploring and putting forward a simple and efficient method for the transformation of environmental criteria into environmental standards is an important basis for the rapid establishment of relevant environmental criteria system and the effective promotion of the development of environmental standards system towards a scientific and reasonable direction.In this paper,the water environment is taken as the research object.By analyzing the research progress of environmental criteria and standards at home and abroad,and the foreign method of transforming environmental criteria into environmental standards,combined with the problems faced in the process of transforming environmental criteria into environmental standards in China,an effective method to transform China's environmental criteria into environmental standards is analyzed.After analysis and comparison,it is found that the pollution reduction accounting method could achieve their simple and efficient conversion.Under the premise of obtaining environmental criteria for certain pollutants,environmental criteria for certain pollutants could be obtained by distributing pollutants reduction costs,and accounting economic benefits after reaching standard,thus obtaining the environmental standard of this type of pollutant,which provides reference to determine the environmental standard limits of such pollutants.
基金financially supported by the National Natural Science Foundation of China (No. 51090384)the National High-Tech Research and Development Program of China (No. 2012AA062302)the Fundamental Research Funds for the Central Universities of China (Nos. N110202001 and N130602003)
文摘The reduction of high-chromium vanadium–titanium magnetite as a typical titanomagnetite containing 0.95wt% V2O5 and 0.61wt% Cr2O3 by H2–CO–CO2 gas mixtures was investigated from 1223 to 1373 K. Both the reduction degree and reduction rate increase with increasing temperature and increasing hydrogen content. At a temperature of 1373 K, an H2/CO ratio of 5/2 by volume, and a reduction time of 40 min, the degree of reduction reaches 95%. The phase transformation during reduction is hypothesized to proceed as follows： Fe2O3 → Fe3O4 → FeO → Fe; Fe9 TiO 15 ＋ Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeT iO 3 → TiO 2;（Cr0.15V0.85）2O3 → Fe2VO4; and Cr1.3Fe0.7O3 → FeC r2O4. The reduction is controlled by the mixed internal diffusion and interfacial reaction at the initial stage; however, the interfacial reaction is dominant. As the reduction proceeds, the internal diffusion becomes the controlling step.
基金Item Sponsored by National High-tech Research and Development Project of China(2012AA062302)Major Program of National Natural Science Foundation of China(51090384)Fundamental Research Funds for the Central Universities of China(N130602003)
文摘To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.
文摘The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity（TRIP） steels with polygonal ferrite matrix, but rarely studied in bainitic TRIP steels. The aim of the present study is to properly investigate the effect of Al and Si on bainite transformation, microstructure and mechanical properties in bainitic steels in order to provide guidelines for the alloying design as a function of process parameters for the 3 rd generation advanced high strength steels（AHSS）. It is shown from the dilatometry study,microstructural investigations and tensile properties measurements that the Al addition results in an acceleration whereas Si addition leads to a retardation in bainite transformation kinetics. The addition of Al retards the decomposition of austenite into pearlite and carbides at holding temperatures higher than450℃ whereas Si retards the decomposition of austenite into carbides at temperatures lower than 450℃.Consequently, the Al-added bainitic steel has a better strength-elongation combination at bainitic holding temperatures higher than 450℃ while Si-added steel has a better strength-elongation combination at temperatures lower than 450℃. The higher yield strength of Al-added steel is mainly attributed to its finer bainitic lath. The higher tensile strength of Si-added steel is not only related to the stronger contribution of Si on work hardening during deformation, but also due to the higher volume fraction of martensite or martensite/austenite（MA） blocks in all heat treatment conditions, as well as the lower mechanical stability of retained austenite in this steel.
基金National Natural Science Foundation of China under Grant No.10775097
文摘Based on our previous paper (Commun.Theor.Phys.39 (2003) 417) we derive the convolution theoremof fractional Fourier transformation in the context of quantum mechanics,which seems a convenient and neat way.Generalization of this method to the complex fractional Fourier transformation case is also possible.
文摘In order to realize the small error attitude transformation of a free floating space robot,a new method of three degrees of freedom（ DOF） attitude transformation was proposed for the space robot using a bionic joint. A general kinematic model of the space robot was established based on the law of linear and angular momentum conservation. A combinational joint model was established combined with bionic joint and closed motion. The attitude transformation of planar,two DOF and three DOF is analyzed and simulated by the model,and it is verified that the feasibility of attitude transformation in three DOF space. Finally,the specific scheme of disturbance elimination in attitude transformation is presented and simulation results are obtained.Therefore,the range of application field of the bionic joint model has been expanded.
基金sponsored by the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(2021ZX52002222019)National Natural Science Foundation of China(NSFC No.U2141216)+1 种基金the Beijing Institute of Technology Young Scholar Startup Program.The authors gratefully acknowledge financial support from the China Scholarship Council(CSC No:202106030118)technical support from the Experimental Center of Advanced Materials(ECAM)of the Beijing Institute of Technology.
文摘TX-80 low-transformation-temperature(LTT)welding wire was used to replace the traditional ER 307Si welding wire to realize the connection of 22SiMn2TiB armor steel in manual overlay welding.The previously existing issues,such as welding cracks,large welding deformation,and severe welding residual stress,were solved to ensure good strength and ductility requirements.In particular,with the same welding conditions,TX-80 LTT wire eliminates welding cracks.It reduces the welding deformation no matter the base pretreatment of pre-setting angle or no pre-setting angle.By comparison,it was found that the microstructure at the TX-80 weld is mainly composed of martensite and a small amount of retained austenite.In contrast,the microstructure of the ER 307Si weld consists of a large amount of austenite and a small amount of skeleton-like ferrite.The variation trend of residual stress and microhardness from the weld to the base were investigated and compared with the mechanical properties of base materials.The TX-80 and the ER 307Si tensile samples elongation is 6.76%and 6.01%,while the ultimate tensile strengths are 877 and 667 MPa,respectively.The average impact toughness at room temperature of the ER 307Si weld is 143.9 J/cm^(2),much higher than that of the TX-80 weld,which is only 36.7 J/cm^(2).The relationship between impact and tensile properties with microstructure species and distribution was established.In addition,the fracture surface of the tensile and the impact samples was observed and analyzed.Deeper dimples,fewer pores,larger radiation zone,and shear lips of TX-80 samples indicate better tensile ductility and worse impact toughness than those of ER 307Si weld.
基金supported by the National Natural Science Foundation of China(Grant No.51474031)
文摘304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained（NG/UFG）structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline（60-100 nm）and ultrafine（100-500 nm）grains,submicron size（500-1000 nm）grains and micron size（〉1000 nm）grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test.
文摘Exchange rate functions under systems of centrallyplanned economy and market economy are quite different,and the mechanism to determine such exchange rate is alsodifferent. To adopt a socialist market economic system inChina, the exchange rate mechanism of Renminbi must bethoroughly transformed. To accomplish this goal, I believethere are three problems that must be solved: first,
文摘In this paper,including some partial differential equations with a number of independent variables, which can he reduced by the infinitesimal form of the group, we obtain the theory of similarity transformation and its application of the second order nonlinear partial differential equations which have two independent variables and two dependent variables in mechanics.
