In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were s...In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were suggested.The effects of heat treatment before forging and hydrostatic pressure during forging on the ductility were investigated in cold upsetting and cup forging.High-temperature annealing was effective to reduce the degree of the texture anisotropy of the specimen,and it was found that the forging limit of the annealed specimen was improved in cold forging.On the other hand,cold cup forging of the annealed specimen was carried out with applying counter pressure.By applying counter pressures of 100-200 MPa during forging,the critical punch stroke for forging limit of the specimen without crack was improved by 25%in punch stroke.展开更多
Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing i...Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing interest from the stand point of reducing energy consumption during dehumidification. In order to find the appropriate ionic liquids(ILs) as a desiccant for the liquid desiccant air-conditioner system, we conducted a systematic evaluation of the humidification capability of 16 types of ILs. Among the tested ILs, tributyl(methyl)phosphonium dimethyl phosphate([P4441][DMPO_4]) exhibited the best dehumidification capacity and had a less corrosive effect on four types of metals as possible piping materials. It should be noted that this [P_(4441)][DMPO_4] has a very stable nature and produced no odor while conducting the experiment and storing for over 1 year at room temperature under ambient conditions. Furthermore, it was revealed that a 77%(w/w) aqueous solution of [P4441][DMPO_4] worked as an efficient desiccant liquid for the liquid desiccant air-conditioner system.展开更多
On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai L...On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ^13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ^13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Boling and AIlerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ^13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment. Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ^13C value; meanwhile, many coarse grains appeared in sediments.展开更多
The Umitaka Spur and Joetsu Knoll region,eastern margin of the Japan Sea,has been investigated as the gas hydrate field associated with the occurrence of methane-related/induced activities.Massive to vein-like gas hyd...The Umitaka Spur and Joetsu Knoll region,eastern margin of the Japan Sea,has been investigated as the gas hydrate field associated with the occurrence of methane-related/induced activities.Massive to vein-like gas hydrates are found on/near the seafloor where huge methane plumes,reaching 600-650 m height, have been observed on the echo sounding images around the summits.Columnar chaotic gas-charged sediment structures are observed beneath the gas hydrate occurrences on the seismic images。展开更多
Study on the organic compounds and stable isotope composition of a sediment section in Dabusu Lake revealed that the organic materials in the sediments came mainly from terrestrial plants brought into the lake by runo...Study on the organic compounds and stable isotope composition of a sediment section in Dabusu Lake revealed that the organic materials in the sediments came mainly from terrestrial plants brought into the lake by runoff. The δ 13 C of the organic materials had high values during warm-dry climatic stages and decreased in cold-wet stages. Analysis of data on carbonate content and 14 C age showed that the lake basin had experienced several wet-cold and warm-dry climatic cycles since 15000 a BP. Since 6700 a BP, the climate reached a relatively stable warm-dry stage, so that the lake water was gradually condensed and finally a saline lake was formed.展开更多
Titanium carbonitride based composite （TiCN-metallic binder） was developed as die material for replacement of cemented tungsten carbide. The effects of thermal conductivity characteristic of the TiCN composite on ho...Titanium carbonitride based composite （TiCN-metallic binder） was developed as die material for replacement of cemented tungsten carbide. The effects of thermal conductivity characteristic of the TiCN composite on hot forging performances were investigated using a servo press with ram motion control. Three types of the die materials; （a） tool steel for hot working, （b） cemented tungsten carbide with high thermal conductivity and （c） TiCN composite with low thermal conductivity were compared. In hot upsetting of a chrome steel workpiece, the TiCN composite die was confirmed to reduce the forging load by approximately 20% at slow forging speed. This is because the die with low thermal conductivity could prevent the workpiece from rapid cooling induced by heat transfer at the die-workpiece interface. In addition, the material flow of the workpiece to a die cavity was improved. Furthermore, the wear depth/wear coefficient of the TiCN composite was lower than that of the tool steel and the cemented tungsten carbide in the numerical analysis of wear due to the combination of low thermal conductivity and high hardness.展开更多
Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake...Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.展开更多
Based on multi-proxy analysis of pollen, carbonate, TOC, TN and δ13C of organic matters, a high-resolution climatic evolution of Qinghai Lake since the Late Glacial Age is recon-structed. The results indicate that th...Based on multi-proxy analysis of pollen, carbonate, TOC, TN and δ13C of organic matters, a high-resolution climatic evolution of Qinghai Lake since the Late Glacial Age is recon-structed. The results indicate that the boundary between the Last Glacial Maximum and the Late Glacial Age is at about 18.2 cal.ka BP. The warm and wet period, which began at about 15.4 cal.ka BP, culminated at 7.4 cal.ka BP and came to its end at about 4.5 cal.ka BP. After that, the climate gradually became cold and dry. The multi-proxy analysis indicates that the climate fluc-tuated greatly during the transitional period from the Late glacial Age to the Holocene, and this is in good accordance with that reflected by deep sea cores of North Atlantic, ice cores of Greenland, lake sediments in Europe, loess sequences and Guliya ice core in China. The cli-matic evolutional characteristic of the Qinghai Lake since the Late Glacial Age shows that the driving force of the East-Asia Monsoon correlates with solar radiation on the ten-thousand-year scale.展开更多
By measuring Sr/Ca ratios of the ostracod shells (Limnocthere cf. inopinata) in sediments of the Daihai Lake, and combined with Sr2+/Ca2+ ratios of the lake water, this paper obtained paleosalinity of the lake water. ...By measuring Sr/Ca ratios of the ostracod shells (Limnocthere cf. inopinata) in sediments of the Daihai Lake, and combined with Sr2+/Ca2+ ratios of the lake water, this paper obtained paleosalinity of the lake water. Vaporizing experiment of the lake water in laboratory showed that there was a quantitative relationship between salinity and oxygen isotope. Using this relationship, oxygen isotope values of the paleo-lake water were calculated. By measuring the oxygen isotope of the authigenic carbonate in the lake’s sediments, and in combination with the oxygen isotope values of the paleo-lake water, the paleotemperature of the lake water was calculated. Finally, based on these proxies, the paleoclimate in the lake basin was explored.展开更多
Ostracods are small bivalved aquatic crustaceans. They secrete shells of low-Mg calcite that are often preserved in lake sediments. Recent work has shown that the uptake of trace elements (especially Mg and Sr) into t...Ostracods are small bivalved aquatic crustaceans. They secrete shells of low-Mg calcite that are often preserved in lake sediments. Recent work has shown that the uptake of trace elements (especially Mg and Sr) into the shell may be a function of the salinity and temperature of the host water. We measured Sr/Ca ratios in living ostracod valves from the species of genus Limnocythere cf. inopinata and Sr2+/Ca2+ ratios of the host water to calculate distribution coefficient of genus Limnocythere cf. inopinata in the Daihai Lake. A function for Sr2+/Ca2+ ratio and salinity was established by measuring a series of Sr2+/Ca2+ ratios and salinities of the lake water in different places of the Daihai Lake. Finally paleosalinities of the lake water were quantitatively reconstructed by the Sr/Ca ratios of ostracod shells of the same species in sediment core of the Daihai Lake.展开更多
The liquid desiccant air-conditioning system allows reducing energy consumption compared to the conventional compressor-type air conditioners.In order to develop desiccant materials for air conditioners,we have invest...The liquid desiccant air-conditioning system allows reducing energy consumption compared to the conventional compressor-type air conditioners.In order to develop desiccant materials for air conditioners,we have investigated the dehumidification capability of quaternary ammonium Ionic Liquids(ILs)and the equilibrium water vapor pressure of aqueous solutions of these ammonium salts.Among the seven tested types of ILs,2-hydroxyN,N,N-trimethylethan-1-aminium dimethylphosphate([Ch][DMPO4])displayed the best dehumidification capability and the lowest equilibrium water vapor pressure.Furthermore,the 80%aqueous solution of[Ch][DMPO4]exhibited a less corrosive effect on four types of metals,i.e.,steel(hot dip zinc-aluminum alloy plated steel),copper(C1100P),aluminum(A5052),and stainless steel(SUS:SUS304).It should be noted that this[Ch][DMPO4]is not only non-toxic but also exhibits a stable nature;the aqueous solution produced no odor after storing for over 1 year under ambient conditions.展开更多
基金supported in part by the Japan Ministry of Education,Culture,Sports,Science and Technology,with Grant-in-Aid for Young Scientists(B)
文摘In order to realize cold forging of magnesium alloys in practical application,some methods for ductility improvement of a commercial wrought AZ31B magnesium alloy(Mg-3%Al-1%Zn,mass fraction) at room temperature were suggested.The effects of heat treatment before forging and hydrostatic pressure during forging on the ductility were investigated in cold upsetting and cup forging.High-temperature annealing was effective to reduce the degree of the texture anisotropy of the specimen,and it was found that the forging limit of the annealed specimen was improved in cold forging.On the other hand,cold cup forging of the annealed specimen was carried out with applying counter pressure.By applying counter pressures of 100-200 MPa during forging,the critical punch stroke for forging limit of the specimen without crack was improved by 25%in punch stroke.
基金supported by a fund for environmental research from Tottori University
文摘Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing interest from the stand point of reducing energy consumption during dehumidification. In order to find the appropriate ionic liquids(ILs) as a desiccant for the liquid desiccant air-conditioner system, we conducted a systematic evaluation of the humidification capability of 16 types of ILs. Among the tested ILs, tributyl(methyl)phosphonium dimethyl phosphate([P4441][DMPO_4]) exhibited the best dehumidification capacity and had a less corrosive effect on four types of metals as possible piping materials. It should be noted that this [P_(4441)][DMPO_4] has a very stable nature and produced no odor while conducting the experiment and storing for over 1 year at room temperature under ambient conditions. Furthermore, it was revealed that a 77%(w/w) aqueous solution of [P4441][DMPO_4] worked as an efficient desiccant liquid for the liquid desiccant air-conditioner system.
基金Supported by National Key Basic Research Fund (No. 2004CB720205) and National Nature and Science Foundation of China (No. 40331003).
文摘On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ^13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ^13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Boling and AIlerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ^13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment. Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ^13C value; meanwhile, many coarse grains appeared in sediments.
文摘The Umitaka Spur and Joetsu Knoll region,eastern margin of the Japan Sea,has been investigated as the gas hydrate field associated with the occurrence of methane-related/induced activities.Massive to vein-like gas hydrates are found on/near the seafloor where huge methane plumes,reaching 600-650 m height, have been observed on the echo sounding images around the summits.Columnar chaotic gas-charged sediment structures are observed beneath the gas hydrate occurrences on the seismic images。
文摘Study on the organic compounds and stable isotope composition of a sediment section in Dabusu Lake revealed that the organic materials in the sediments came mainly from terrestrial plants brought into the lake by runoff. The δ 13 C of the organic materials had high values during warm-dry climatic stages and decreased in cold-wet stages. Analysis of data on carbonate content and 14 C age showed that the lake basin had experienced several wet-cold and warm-dry climatic cycles since 15000 a BP. Since 6700 a BP, the climate reached a relatively stable warm-dry stage, so that the lake water was gradually condensed and finally a saline lake was formed.
文摘Titanium carbonitride based composite （TiCN-metallic binder） was developed as die material for replacement of cemented tungsten carbide. The effects of thermal conductivity characteristic of the TiCN composite on hot forging performances were investigated using a servo press with ram motion control. Three types of the die materials; （a） tool steel for hot working, （b） cemented tungsten carbide with high thermal conductivity and （c） TiCN composite with low thermal conductivity were compared. In hot upsetting of a chrome steel workpiece, the TiCN composite die was confirmed to reduce the forging load by approximately 20% at slow forging speed. This is because the die with low thermal conductivity could prevent the workpiece from rapid cooling induced by heat transfer at the die-workpiece interface. In addition, the material flow of the workpiece to a die cavity was improved. Furthermore, the wear depth/wear coefficient of the TiCN composite was lower than that of the tool steel and the cemented tungsten carbide in the numerical analysis of wear due to the combination of low thermal conductivity and high hardness.
基金supported by National Natural Science Foundation of China(Grant No.40802084)International Science&Technology Cooperation Program of China(Grant No.2011DFA21240)the CAS/SAFEA International Partnership Program for Creative Research Teams(Grant No.KZZDEW-TZ-08)
文摘Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.
基金the National Natural Science Foundation of China(Grant No.40072056)the Knowledge Innovation Project of the Chinese Academy of Sciences(CAS)(Grant No.KZCX1-10-01)+1 种基金the Post-doctor Foundation of China the Foundation of Key Laboratory of Lake Sedimentation and Environment,Nanjing Institute of Geography and Limnology,CAS
文摘Based on multi-proxy analysis of pollen, carbonate, TOC, TN and δ13C of organic matters, a high-resolution climatic evolution of Qinghai Lake since the Late Glacial Age is recon-structed. The results indicate that the boundary between the Last Glacial Maximum and the Late Glacial Age is at about 18.2 cal.ka BP. The warm and wet period, which began at about 15.4 cal.ka BP, culminated at 7.4 cal.ka BP and came to its end at about 4.5 cal.ka BP. After that, the climate gradually became cold and dry. The multi-proxy analysis indicates that the climate fluc-tuated greatly during the transitional period from the Late glacial Age to the Holocene, and this is in good accordance with that reflected by deep sea cores of North Atlantic, ice cores of Greenland, lake sediments in Europe, loess sequences and Guliya ice core in China. The cli-matic evolutional characteristic of the Qinghai Lake since the Late Glacial Age shows that the driving force of the East-Asia Monsoon correlates with solar radiation on the ten-thousand-year scale.
文摘By measuring Sr/Ca ratios of the ostracod shells (Limnocthere cf. inopinata) in sediments of the Daihai Lake, and combined with Sr2+/Ca2+ ratios of the lake water, this paper obtained paleosalinity of the lake water. Vaporizing experiment of the lake water in laboratory showed that there was a quantitative relationship between salinity and oxygen isotope. Using this relationship, oxygen isotope values of the paleo-lake water were calculated. By measuring the oxygen isotope of the authigenic carbonate in the lake’s sediments, and in combination with the oxygen isotope values of the paleo-lake water, the paleotemperature of the lake water was calculated. Finally, based on these proxies, the paleoclimate in the lake basin was explored.
基金This work was supported bythe National Natural Science Foundation of China (Grant Nos. 49702028 and 49894170-04) and the Project of the Chinese Academy of Sciences (Grant No. KZCX1-Y-05).
文摘Ostracods are small bivalved aquatic crustaceans. They secrete shells of low-Mg calcite that are often preserved in lake sediments. Recent work has shown that the uptake of trace elements (especially Mg and Sr) into the shell may be a function of the salinity and temperature of the host water. We measured Sr/Ca ratios in living ostracod valves from the species of genus Limnocythere cf. inopinata and Sr2+/Ca2+ ratios of the host water to calculate distribution coefficient of genus Limnocythere cf. inopinata in the Daihai Lake. A function for Sr2+/Ca2+ ratio and salinity was established by measuring a series of Sr2+/Ca2+ ratios and salinities of the lake water in different places of the Daihai Lake. Finally paleosalinities of the lake water were quantitatively reconstructed by the Sr/Ca ratios of ostracod shells of the same species in sediment core of the Daihai Lake.
基金supported by National Natural Science Foundation of China(21676160,21825501,21905157,and U1801257)National Key Research and Development Program(2016YFA0202500 and 2016YFA0200102)+1 种基金China Postdoctoral Science Foundation(2018M641375 and 2019M650697)the Tsinghua University Initiative Scientific Research Program.
文摘The liquid desiccant air-conditioning system allows reducing energy consumption compared to the conventional compressor-type air conditioners.In order to develop desiccant materials for air conditioners,we have investigated the dehumidification capability of quaternary ammonium Ionic Liquids(ILs)and the equilibrium water vapor pressure of aqueous solutions of these ammonium salts.Among the seven tested types of ILs,2-hydroxyN,N,N-trimethylethan-1-aminium dimethylphosphate([Ch][DMPO4])displayed the best dehumidification capability and the lowest equilibrium water vapor pressure.Furthermore,the 80%aqueous solution of[Ch][DMPO4]exhibited a less corrosive effect on four types of metals,i.e.,steel(hot dip zinc-aluminum alloy plated steel),copper(C1100P),aluminum(A5052),and stainless steel(SUS:SUS304).It should be noted that this[Ch][DMPO4]is not only non-toxic but also exhibits a stable nature;the aqueous solution produced no odor after storing for over 1 year under ambient conditions.
