[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temp...[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temperature ≥35 ℃) and low(the daily lowest temperature ≤-20 ℃) temperature data in five observatories in the east of Hexi Corridor during 1960-2009,the temporal and spatial distribution,intensity,continuity and circulation situation of high and low temperature were analyzed in detail by using the statistical method.[Result] The high temperature weather in the east of Hexi Corridor mainly happened in the edge of northeast desert,and the low temperature mainly happened in the mountain zone where the altitude was higher and the edge of north desert.As the climate became warm,the high temperature days showed the weak increase trend,and the intensity strengthened.The low temperature days showed the obvious decrease trend,and the intensity weakened.The high temperature weather mainly occurred in June,August,and the low temperature mainly occurred in January,February,December.The high and low temperature weather had the durative characteristic.The strong high and low temperature mainly occurred in the durative time of high and low temperature.The high temperature weather appeared in the zone where was controlled and affected by the subtropical high.The low temperature weather appeared in the zone where the strong cold air accumulated and invaded.[Conclusion] The research had the extremely important significance on servicing for the agriculture,preventing and reducing the natural disasters,promoting the local economic development.展开更多
The comprehensive improvement strategy of intra-county environment pollution in the city and countryside was searched.By the research method which combined the microscopic view,the macroscopic view with the dynamic pe...The comprehensive improvement strategy of intra-county environment pollution in the city and countryside was searched.By the research method which combined the microscopic view,the macroscopic view with the dynamic perspective,the seriousness of rural water quality,soil and atmospheric pollution in Xiangxiang,Xiangtan and the surrounding areas in Shaoshan irrigated area was revealed.The control measure which was 'four-dimensional pollution in the city and countryside'—— low-carbon-high-value agriculture and the technology innovation was proposed.The low-carbon-high-value technology innovation industrialization demonstration in three parts which included the pre-production,mid-production and post-production deep-processing of cultivation and breeding industry in the ecological cyclic agricultural garden in Shaoshan irrigated area was the driving force.We tried to propel the low-carbon ecological cultivation and breeding industry which included the paddy rice,grass,tree,medicinal herbs and pig,cow,chick,duck,fish.We wanted to relieve the structural unbalance of previous cultivation and breeding industry,'cheap grain hurting the farmers' and the short-leg problem of social-economic-ecological benefit.The results showed that the low-carbon-high-value agricultural system was a poly-generation technology system which promoted the multi-level and grading utilization,saved the energy,reduced the consumption and cleaned the production based on the ecology.展开更多
Edward Hall offers us an effective means of examining cultural similarities and differences,that is the classification of high-context and low-context culture.The paper attempts to analyze a case of a Chinese refusal ...Edward Hall offers us an effective means of examining cultural similarities and differences,that is the classification of high-context and low-context culture.The paper attempts to analyze a case of a Chinese refusal from the perspective of highcontext and low-context communication and explores the differences between the two types of communication.展开更多
By using the routine observation data,a heavy precipitation process which happened in Guangxi on May 27,2006 was analyzed.The results that this heavy precipitation occurred in the common coordination weather system wh...By using the routine observation data,a heavy precipitation process which happened in Guangxi on May 27,2006 was analyzed.The results that this heavy precipitation occurred in the common coordination weather system which included the high-altitude trough,the shear line and the ground cold front.The ascent branch of subtropical longitude circle circulation and the polar front jet stream longitude circle circulation had the important role for the formation of rainstorm area.The coupling effect of southerly jet,low-altitude westerly jet and high-altitude westerly jet in the boundary layer was the important reason of rainstorm occurrence.展开更多
The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave ...The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave so far focused and somewhat succeeded on αat low energy. This manuscript, therefore, provides a more complete solution. That αpermeates even the golden section is not only further confirmation of the ubiquity of this constant of physics, but also leads to the inescapable conclusion that it originates in the golden section, a geometrical constant ubiquitous in physical phenomena.展开更多
The Wedding Banquet is a movie about a gay Taiwan Residents immigrant man who marries a mainland Chinese woman to placate his parents and get her a green card. His plan backfires and things get out of hand when his pa...The Wedding Banquet is a movie about a gay Taiwan Residents immigrant man who marries a mainland Chinese woman to placate his parents and get her a green card. His plan backfires and things get out of hand when his parents arrive in the United States to plan his wedding banquet. Based on Hall's theory of high-context and low-context culture, this paper analyzes the cultural conflicts in the movie from six perspectives, and offers suggestions to the harmonious development of China and America. It is hoped that the paper can help readers get an in-depth comprehension of Hall's theory of high-context and low-context culture and discover some invisible conflicts between China and the West and finally raise people's consciousness of cultural conflicts and ways of handling the conflicts. With the advancement of globalization, intercultural communicative competence is becoming more and more important, and social communication between China and the West will become more relaxed and fruitful if people acquire more knowledge in intercultural communication.展开更多
AIM:To evaluate the efficacy of high-dose proton pump inhibitors(PPIs)vs low-dose PPIs for patients with upper gastrointestinal bleeding.METHODS:PubMed,Embase,the Cochrane Library,and Web of Science were searched to i...AIM:To evaluate the efficacy of high-dose proton pump inhibitors(PPIs)vs low-dose PPIs for patients with upper gastrointestinal bleeding.METHODS:PubMed,Embase,the Cochrane Library,and Web of Science were searched to identify relevant randomized controlled trials(RCTs).Eligible trials were RCTs that compared high-dose PPI with low-dose PPI following endoscopic hemostasis.The primary endpoint was rebleeding;secondary endpoints were patient numbers that needed surgery,and mortality.The meta-analysis was performed with a fixed effects model or random effects model.RESULTS:Nine eligible RCTs including 1342 patients were retrieved.The results showed that high-dose intravenous PPI was not superior to low-dose intra-venous PPI in reducing rebleeding[odds ratio(OR)= 1.091,95%confidential interval(CI):0.777-1.532],need for surgery(OR=1.522,95%CI:0.643-3.605) and mortality(OR=1.022,95%CI:0.476-2.196).Subgroup analysis according to different region revealed no difference in rebleeding rate between Asian patients(OR=0.831,95%CI,0.467-1.480)and European patients(OR=1.263,95%CI:0.827-1.929).CONCLUSION:Low-dose intravenous PPI can achieve the same efficacy as high-dose PPI following endoscopic hemostasis.展开更多
The influence of solid solution treatments on the dissolution of carbides precipitates,the grain size,and the hardness of high strength low expansion alloy were investigated through XRD analysis,microstructure observa...The influence of solid solution treatments on the dissolution of carbides precipitates,the grain size,and the hardness of high strength low expansion alloy were investigated through XRD analysis,microstructure observations,and theoretical computation.It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ℃.When the temperature was over 1 200 ℃,the grain size increased remarkably,which led to the reduction of hardness.展开更多
The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10...The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10 s-1 using an MMS-200 thermal simulation testing machine. Based on the flow curves from the experiment, the effects of temperature and strain rate on the dynamic recrystallization behavior were analyzed. The flow stress decreased with increasing deformation temperature and decreasing strain rate. With the assistance of the process parameters, constitutive equations were used to obtain the activation energy and hot working equation. The hot deformation activation energy of HSLA steel in this work was 351.87 kJ/mol. The work hardening rate was used to determine the critical stress(strain) or the peak stress(strain). The dependence of these characteristic values on the Zener-Hollomon parameter was found. A dynamic recrystallization kinetics model of the tested HSLA steel was constructed, and the validity of the model was confirmed by the experimental results. Observation of the microstructures indicated that the grain size increased with increasing deformation temperature,which led to a lowered corrosion resistance of the specimens.展开更多
The impact of Fe concentrations on the growth of Microcystis aeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density,total and cell chlorophyll-a intr...The impact of Fe concentrations on the growth of Microcystis aeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density,total and cell chlorophyll-a intracellular Fe content and organic elemental composition of M.aeruginosa to different concentration gradients of Fe（Ⅲ） in the solutions were analysed. The results showed that the proliferation speeds of M. aeruginosa were：（1） decelerated when the Fe（Ⅲ） concentration was lower than 50 μg/L in the solutions,（2） promoted and positively related to the increase of Fe（Ⅲ） concentration from 100 to 500 μg/L in the solutions over the experimental period, and（3） promoted in the early stage but decelerated in later stages by excess adsorption of Fe by cells when the Fe（Ⅲ） concentration was higher than 500 μg/L in the solutions. The maximum cell density, total and cell chlorophyll-a were all observed at 500 μg Fe（Ⅲ）/L concentration. The organic elemental composition of M. aeruginosa was also affected by the concentration of Fe（Ⅲ） in the solutions, and the molecular formula of M. aeruginosa should be expressed as C7–7.5H14O0.8–1.3N3.5–5according to the functions for different Fe（Ⅲ）concentrations. Cell carbon and oxygen content appeared to increase slightly, while cell nitrogen content appeared to decrease as Fe（Ⅲ） concentrations increased from 100 to 500 μg/L in the solutions. This was attributed to the competition of photosynthesis and nitrogen adsorption under varying cell Fe content.展开更多
The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensiti...The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.展开更多
Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most ...Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most nickel-based superalloys. In order to add more Cr into Ni-based alloy for improving high temperature oxidation and corrosion resistance, the poor hot workability of high-Cr alloy must be first solved. Deformation characteristic of a high-Cr nickel-based alloy （40 wt% Cr） under hot compression conditions at 800-1200 ℃ has been investigated by using a Gleeble 3500 machine, and the microstructural evolution during hot working process has been observed by optical microscopy and scanning electron microscopy. The results show that a high-temperature low-plasticity （HTLP） region exists in this high-Cr nickel-based alloy. This phenomenon can be attributed to its non-uniform interdendritic microstructure at high temperatures. These results can explain the poor hot workability of high-Cr nickel-based alloy.展开更多
Low cycle fatigue behavior of a quenched and tempered high-strength steel(Q960 E) was studied in the strain amplitude ranging from ± 0.5% to ± 1.2% at room temperature. As a result of fatigue loading, the di...Low cycle fatigue behavior of a quenched and tempered high-strength steel(Q960 E) was studied in the strain amplitude ranging from ± 0.5% to ± 1.2% at room temperature. As a result of fatigue loading, the dislocation structural evolution and fracture mechanism were examined and studied by transmission electron microscopy and scanning electron microscopy(SEM). The results showed that this Q960 E steel showed cyclic softening at different strain amplitudes, and the softening tendency was more apparent at strain amplitude of ±(0.6–1.2)% than that at ± 0.5%. The reduction in dislocation density with increasing strain amplitude is responsible for the softening tendency of cyclic stress with the strain amplitude. The material illustrates near-Masing behavior at strain amplitude ranging from ± 0.6% to ± 1.2%. The near-Masing behavior of Q960 E high-strength steel can be the result of stability of martensite lath at different strain amplitudes. Partial transformation from martensite laths to dislocation cells is responsible for the derivation from ideal Masing behavior. In the SEM examination of fracture surfaces, transgranular cracks initiate on the sample surface. Striations can be found during the crack propagation stage.展开更多
The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quan...The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.展开更多
The influence of Ti on weld microstructure and mechanical properties in large heat input welding of high strength low alloy steels is investigated. The results indicate that a moderate amount of Ti is still effective ...The influence of Ti on weld microstructure and mechanical properties in large heat input welding of high strength low alloy steels is investigated. The results indicate that a moderate amount of Ti is still effective for grain refinement even under larger heat input and a large amount of acicular ferrite （AF） is formed in the weld metal when Ti content is within 0. 028%--0. 038%. With increasing Ti content, proeutectoid ferrite in the weld metal decreases, whereas bainite and M-A constituent increase. The type of inclusion in the welds varies from Mn-Si-AI-O to Ti-Mn- A1-O and finally to Ti-A1-O as Ti content increases from 0 up to 0. 064%. As for adding 0. 028%--0. 038% Ti, high weld toughness could be attained since most inclusions less than 2 tim which contain Ti20s provide the effective nu- clei for aeicular ferrite formation. However, the toughness of the weld metals severely reduces when Ti content is over the optimum ranRe of 0. 028%--0. 038%.展开更多
Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, dis...Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.展开更多
Nozzle blockage is a common problem during continuous casting of Al-killed steel, and calcium treatment is widely used to resolve it. In consideration of the production costs, the technology of nonmetallic inclusion c...Nozzle blockage is a common problem during continuous casting of Al-killed steel, and calcium treatment is widely used to resolve it. In consideration of the production costs, the technology of nonmetallic inclusion control was studied to optimize the Ca consumption. The proposed process of slag washing was employed, and the refining slag composition, deoxidation conditions and alloying systems were optimized. Using these measures, the steel cleanliness before Ca addition was improved significantly, and the corresponding Ca consumption was reduced. More- over, the continuous casting could be conducted smoothly.展开更多
The product system of high strength low alloy steels (HSLA) produced by Wuhan Iron and Steel (Group) Corporation (WISCO) was presented.A series of high performance structural steels have been developed for important c...The product system of high strength low alloy steels (HSLA) produced by Wuhan Iron and Steel (Group) Corporation (WISCO) was presented.A series of high performance structural steels have been developed for important construction projects around the world in different areas,such as bridge,pressure vessel,pipe line,shipbuilding,architecture,machinery and railway wagons.In order to promote the development of large heat input welding steel,high grade thick pipeline steel and long span bridge steel,a lot of advanced production technologies have been achieved through intensive investigation,such as the control of high purity,high homogenization and free defects in steel slabs,the rules of high melting point particle formation and distribution in micro and nano scale during steel production,and the TMCP technology for ultra low carbon bainite steel for medium and heavy plates.WISCO will carry on research and application of economic and weather-resistant steels and promote the developing and producing technologies of HSLA steel.展开更多
基金Supported by Gansu Province the Fifth Installment "Ten Plan"~~
文摘[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temperature ≥35 ℃) and low(the daily lowest temperature ≤-20 ℃) temperature data in five observatories in the east of Hexi Corridor during 1960-2009,the temporal and spatial distribution,intensity,continuity and circulation situation of high and low temperature were analyzed in detail by using the statistical method.[Result] The high temperature weather in the east of Hexi Corridor mainly happened in the edge of northeast desert,and the low temperature mainly happened in the mountain zone where the altitude was higher and the edge of north desert.As the climate became warm,the high temperature days showed the weak increase trend,and the intensity strengthened.The low temperature days showed the obvious decrease trend,and the intensity weakened.The high temperature weather mainly occurred in June,August,and the low temperature mainly occurred in January,February,December.The high and low temperature weather had the durative characteristic.The strong high and low temperature mainly occurred in the durative time of high and low temperature.The high temperature weather appeared in the zone where was controlled and affected by the subtropical high.The low temperature weather appeared in the zone where the strong cold air accumulated and invaded.[Conclusion] The research had the extremely important significance on servicing for the agriculture,preventing and reducing the natural disasters,promoting the local economic development.
基金Supported by " Research on The Control Technology of Subtropical Agriculture Pollution System" Special Project of National Environment Protection Public Welfare Industry Science Research "Research on The Construction Strategy of Ecological Civilization" Development Plan Research Project of State Development and Reform Commission+1 种基金Xiangxiang " High-output and Efficient Cultivation of High Quality Rice and Processing Technology Industrialization Demonstration " in The Plan Test Site of National Science and Technology Enriching People and Developing County Special Project Action" Xiangxiang Middle and Long-term Development Plan of Modern Agriculture" of Subtropical Agriculture Ecology Institute in Chinese Academy of Science
文摘The comprehensive improvement strategy of intra-county environment pollution in the city and countryside was searched.By the research method which combined the microscopic view,the macroscopic view with the dynamic perspective,the seriousness of rural water quality,soil and atmospheric pollution in Xiangxiang,Xiangtan and the surrounding areas in Shaoshan irrigated area was revealed.The control measure which was 'four-dimensional pollution in the city and countryside'—— low-carbon-high-value agriculture and the technology innovation was proposed.The low-carbon-high-value technology innovation industrialization demonstration in three parts which included the pre-production,mid-production and post-production deep-processing of cultivation and breeding industry in the ecological cyclic agricultural garden in Shaoshan irrigated area was the driving force.We tried to propel the low-carbon ecological cultivation and breeding industry which included the paddy rice,grass,tree,medicinal herbs and pig,cow,chick,duck,fish.We wanted to relieve the structural unbalance of previous cultivation and breeding industry,'cheap grain hurting the farmers' and the short-leg problem of social-economic-ecological benefit.The results showed that the low-carbon-high-value agricultural system was a poly-generation technology system which promoted the multi-level and grading utilization,saved the energy,reduced the consumption and cleaned the production based on the ecology.
文摘Edward Hall offers us an effective means of examining cultural similarities and differences,that is the classification of high-context and low-context culture.The paper attempts to analyze a case of a Chinese refusal from the perspective of highcontext and low-context communication and explores the differences between the two types of communication.
基金Supported by The Forecaster Special Project of New Technology Spreading Scheme of China Meteorological Administration(CMATG2008Y07)The Brainstorm Project of Guangxi Science and Technology Department(Guangxi Science and Technology Brainstorm Project 0993002-1 and 0816006-9)
文摘By using the routine observation data,a heavy precipitation process which happened in Guangxi on May 27,2006 was analyzed.The results that this heavy precipitation occurred in the common coordination weather system which included the high-altitude trough,the shear line and the ground cold front.The ascent branch of subtropical longitude circle circulation and the polar front jet stream longitude circle circulation had the important role for the formation of rainstorm area.The coupling effect of southerly jet,low-altitude westerly jet and high-altitude westerly jet in the boundary layer was the important reason of rainstorm occurrence.
文摘The fine-structure constant (α) at low and high energies is herein computed from control numbers in the theory of the golden section (φ). Countless attempts at deriving, or otherwise explaining the origin of αhave so far focused and somewhat succeeded on αat low energy. This manuscript, therefore, provides a more complete solution. That αpermeates even the golden section is not only further confirmation of the ubiquity of this constant of physics, but also leads to the inescapable conclusion that it originates in the golden section, a geometrical constant ubiquitous in physical phenomena.
文摘The Wedding Banquet is a movie about a gay Taiwan Residents immigrant man who marries a mainland Chinese woman to placate his parents and get her a green card. His plan backfires and things get out of hand when his parents arrive in the United States to plan his wedding banquet. Based on Hall's theory of high-context and low-context culture, this paper analyzes the cultural conflicts in the movie from six perspectives, and offers suggestions to the harmonious development of China and America. It is hoped that the paper can help readers get an in-depth comprehension of Hall's theory of high-context and low-context culture and discover some invisible conflicts between China and the West and finally raise people's consciousness of cultural conflicts and ways of handling the conflicts. With the advancement of globalization, intercultural communicative competence is becoming more and more important, and social communication between China and the West will become more relaxed and fruitful if people acquire more knowledge in intercultural communication.
基金Supported by First Affiliated Hospital,Guangxi Medical University
文摘AIM:To evaluate the efficacy of high-dose proton pump inhibitors(PPIs)vs low-dose PPIs for patients with upper gastrointestinal bleeding.METHODS:PubMed,Embase,the Cochrane Library,and Web of Science were searched to identify relevant randomized controlled trials(RCTs).Eligible trials were RCTs that compared high-dose PPI with low-dose PPI following endoscopic hemostasis.The primary endpoint was rebleeding;secondary endpoints were patient numbers that needed surgery,and mortality.The meta-analysis was performed with a fixed effects model or random effects model.RESULTS:Nine eligible RCTs including 1342 patients were retrieved.The results showed that high-dose intravenous PPI was not superior to low-dose intra-venous PPI in reducing rebleeding[odds ratio(OR)= 1.091,95%confidential interval(CI):0.777-1.532],need for surgery(OR=1.522,95%CI:0.643-3.605) and mortality(OR=1.022,95%CI:0.476-2.196).Subgroup analysis according to different region revealed no difference in rebleeding rate between Asian patients(OR=0.831,95%CI,0.467-1.480)and European patients(OR=1.263,95%CI:0.827-1.929).CONCLUSION:Low-dose intravenous PPI can achieve the same efficacy as high-dose PPI following endoscopic hemostasis.
文摘The influence of solid solution treatments on the dissolution of carbides precipitates,the grain size,and the hardness of high strength low expansion alloy were investigated through XRD analysis,microstructure observations,and theoretical computation.It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ℃.When the temperature was over 1 200 ℃,the grain size increased remarkably,which led to the reduction of hardness.
基金supported financially by the Fundamental Research Funds for the Central Universities (Nos. HEUCFP201719 and HEUCFP201731)
文摘The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10 s-1 using an MMS-200 thermal simulation testing machine. Based on the flow curves from the experiment, the effects of temperature and strain rate on the dynamic recrystallization behavior were analyzed. The flow stress decreased with increasing deformation temperature and decreasing strain rate. With the assistance of the process parameters, constitutive equations were used to obtain the activation energy and hot working equation. The hot deformation activation energy of HSLA steel in this work was 351.87 kJ/mol. The work hardening rate was used to determine the critical stress(strain) or the peak stress(strain). The dependence of these characteristic values on the Zener-Hollomon parameter was found. A dynamic recrystallization kinetics model of the tested HSLA steel was constructed, and the validity of the model was confirmed by the experimental results. Observation of the microstructures indicated that the grain size increased with increasing deformation temperature,which led to a lowered corrosion resistance of the specimens.
基金supported by the China National Major Project of Water Pollution Control(No.2012ZX07313001-002)JSPS Postdoctoral Fellow Program(No.P15353)+2 种基金Shaanxi Provincial Program for ScienceTechnology Development(No.2013KJXX-55)Program for Innovative Research Team(No.2013KCT-13)
文摘The impact of Fe concentrations on the growth of Microcystis aeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density,total and cell chlorophyll-a intracellular Fe content and organic elemental composition of M.aeruginosa to different concentration gradients of Fe（Ⅲ） in the solutions were analysed. The results showed that the proliferation speeds of M. aeruginosa were：（1） decelerated when the Fe（Ⅲ） concentration was lower than 50 μg/L in the solutions,（2） promoted and positively related to the increase of Fe（Ⅲ） concentration from 100 to 500 μg/L in the solutions over the experimental period, and（3） promoted in the early stage but decelerated in later stages by excess adsorption of Fe by cells when the Fe（Ⅲ） concentration was higher than 500 μg/L in the solutions. The maximum cell density, total and cell chlorophyll-a were all observed at 500 μg Fe（Ⅲ）/L concentration. The organic elemental composition of M. aeruginosa was also affected by the concentration of Fe（Ⅲ） in the solutions, and the molecular formula of M. aeruginosa should be expressed as C7–7.5H14O0.8–1.3N3.5–5according to the functions for different Fe（Ⅲ）concentrations. Cell carbon and oxygen content appeared to increase slightly, while cell nitrogen content appeared to decrease as Fe（Ⅲ） concentrations increased from 100 to 500 μg/L in the solutions. This was attributed to the competition of photosynthesis and nitrogen adsorption under varying cell Fe content.
基金performed within the VINN Excellence Center Hero-m,financed by VINNOVA,the Swedish Governmental Agency for Innovation Systems,Swedish Industry,KTH Royal Institute of Technology
文摘The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.
基金support from the National Natural Science Foundation of China, No.50771011
文摘Cr is the most important element in nickel-based alloys to prevent high temperature oxidation and corrosion. However, high-Cr content will lead to a decline of hot workability which limits the addition of Cr for most nickel-based superalloys. In order to add more Cr into Ni-based alloy for improving high temperature oxidation and corrosion resistance, the poor hot workability of high-Cr alloy must be first solved. Deformation characteristic of a high-Cr nickel-based alloy （40 wt% Cr） under hot compression conditions at 800-1200 ℃ has been investigated by using a Gleeble 3500 machine, and the microstructural evolution during hot working process has been observed by optical microscopy and scanning electron microscopy. The results show that a high-temperature low-plasticity （HTLP） region exists in this high-Cr nickel-based alloy. This phenomenon can be attributed to its non-uniform interdendritic microstructure at high temperatures. These results can explain the poor hot workability of high-Cr nickel-based alloy.
基金financial supports of the National Natural Science Foundation of China (No. 51674079)Anhui Provincial Natural Science Foundation (Nos. KJ2018A0062, KJ2017A128 and KJ2017A066)
文摘Low cycle fatigue behavior of a quenched and tempered high-strength steel(Q960 E) was studied in the strain amplitude ranging from ± 0.5% to ± 1.2% at room temperature. As a result of fatigue loading, the dislocation structural evolution and fracture mechanism were examined and studied by transmission electron microscopy and scanning electron microscopy(SEM). The results showed that this Q960 E steel showed cyclic softening at different strain amplitudes, and the softening tendency was more apparent at strain amplitude of ±(0.6–1.2)% than that at ± 0.5%. The reduction in dislocation density with increasing strain amplitude is responsible for the softening tendency of cyclic stress with the strain amplitude. The material illustrates near-Masing behavior at strain amplitude ranging from ± 0.6% to ± 1.2%. The near-Masing behavior of Q960 E high-strength steel can be the result of stability of martensite lath at different strain amplitudes. Partial transformation from martensite laths to dislocation cells is responsible for the derivation from ideal Masing behavior. In the SEM examination of fracture surfaces, transgranular cracks initiate on the sample surface. Striations can be found during the crack propagation stage.
文摘The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.
基金Item Sponsored by National High Technology Research and Development Project of China(2009AA03Z530)
文摘The influence of Ti on weld microstructure and mechanical properties in large heat input welding of high strength low alloy steels is investigated. The results indicate that a moderate amount of Ti is still effective for grain refinement even under larger heat input and a large amount of acicular ferrite （AF） is formed in the weld metal when Ti content is within 0. 028%--0. 038%. With increasing Ti content, proeutectoid ferrite in the weld metal decreases, whereas bainite and M-A constituent increase. The type of inclusion in the welds varies from Mn-Si-AI-O to Ti-Mn- A1-O and finally to Ti-A1-O as Ti content increases from 0 up to 0. 064%. As for adding 0. 028%--0. 038% Ti, high weld toughness could be attained since most inclusions less than 2 tim which contain Ti20s provide the effective nu- clei for aeicular ferrite formation. However, the toughness of the weld metals severely reduces when Ti content is over the optimum ranRe of 0. 028%--0. 038%.
基金The Director,Naval Material Research Laboratory(NMRL),Ambernath for financial support through CARS project No:G8/15250/2011 dated29.02.2012
文摘Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.
文摘Nozzle blockage is a common problem during continuous casting of Al-killed steel, and calcium treatment is widely used to resolve it. In consideration of the production costs, the technology of nonmetallic inclusion control was studied to optimize the Ca consumption. The proposed process of slag washing was employed, and the refining slag composition, deoxidation conditions and alloying systems were optimized. Using these measures, the steel cleanliness before Ca addition was improved significantly, and the corresponding Ca consumption was reduced. More- over, the continuous casting could be conducted smoothly.
文摘The product system of high strength low alloy steels (HSLA) produced by Wuhan Iron and Steel (Group) Corporation (WISCO) was presented.A series of high performance structural steels have been developed for important construction projects around the world in different areas,such as bridge,pressure vessel,pipe line,shipbuilding,architecture,machinery and railway wagons.In order to promote the development of large heat input welding steel,high grade thick pipeline steel and long span bridge steel,a lot of advanced production technologies have been achieved through intensive investigation,such as the control of high purity,high homogenization and free defects in steel slabs,the rules of high melting point particle formation and distribution in micro and nano scale during steel production,and the TMCP technology for ultra low carbon bainite steel for medium and heavy plates.WISCO will carry on research and application of economic and weather-resistant steels and promote the developing and producing technologies of HSLA steel.
