Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiom...Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index(MODIS NDVI)and climate data,a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land.Data were collected during the growing season between 2001 and 2020.Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes.Results revealed a predominantly increasing trend for average NDVI.The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences.The area with improved vegetation was greater than that of the degraded region.Climate variability and human activities were driving forces controlling vegetation cover changes,and their effects on vegetation dynamics varied by region.The response of vegetation dynamics was stronger for precipitation than temperature,indicating that precipitation was the main climate variable influencing the NDVI changes.The relative role of human activities was responsible for>70%of the changes,demonstrating that human activities were the main driving factor of the NDVI changes.The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality.These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.展开更多
Climate,land use and land cover(LULC)changes are among the primary driving forces of soil loss.Decoupling their effects can help in understanding the magnitude and trend of soil loss in response to human activities an...Climate,land use and land cover(LULC)changes are among the primary driving forces of soil loss.Decoupling their effects can help in understanding the magnitude and trend of soil loss in response to human activities and ecosystem management.Here,the RUSLE model was applied to estimate the spatial-temporal variations of soil loss rate in the Three Gorges Reservoir(TGR)area during 2001-2015,followed by a scenario design to decouple the effects of climate and LULC changes.The results showed that increasing rainfall generated as much as 2.90×10^(7)t soil loss in the TGR area.However,such effect was offset by changes in LULC particularly afforestation,which retained about 1.10×10^(7)t soil annually.Other human activities such as dam development and urbanization aggravated soil loss by as much as 1.40×10^(6)t annually.Because of land use policies that favor economic development,distinct spatial variances of soil loss were observed in TGR area.Soil loss in some counties located downstream of the TGR area(i.e.,close to the dam)was more influenced by dam development,but soil loss in the other counties was more influenced by urbanization.As climate change(i.e.,increasing rainfall)did not affect plant performance in TGR area,our findings suggested that ecological restoration was more beneficial to curb the amount of soil loss caused by urbanization and dam construction.展开更多
Roots and shells are two potential organs through which peanut plants absorb cadium(Cd)from soils;however,the relative contributions of the two uptake pathways(root uptake and shell absorption)to kernel Cd accumulatio...Roots and shells are two potential organs through which peanut plants absorb cadium(Cd)from soils;however,the relative contributions of the two uptake pathways(root uptake and shell absorption)to kernel Cd accumulation and their translocation characteristics are poorly understood.In this study,the relative contributions of the two pathways to Cd accumulation in two peanut cultivars,Xianghua2008(XH)and Yueyou43(YY),were accurately assessed by labeling rooting and podding zone soils with 113Cd and 111Cd isotopes(0.3 mg kg^(-1) dry soil),respectively,in a split-pot design.The results showed that approximately 96%of the Cd accumulated in the peanut kernels was derived from root uptake,while only 4%originated from shell absorption.Only 1%of the Cd accumulated in whole peanut plants was attributed to shell absorption,of which 41%–44%was retained in shells and 56%–59%was translocated to kernels.In contrast,the Cd absorbed by roots was efficiently translocated into all plant organs,of which 80%–84%was distributed in shoots.Although YY accumulated 1.3 times more Cd in whole plants than XH,the relative contributions of the two pathways to Cd accumulation in each plant organ were barely affected by peanut cultivars.Due to the strong retention effect of shells,shell-derived Cd was approximately 2 times higher than root-derived Cd in shells.These results would improve the understanding of Cd accumulation processes in peanut plants,revealing that the root uptake pathway contributes predominantly to the Cd concentration in peanut kernels,based on which strategies and technology for the reduction of Cd in peanut plants could be designed and developed.展开更多
As a critical region sensitive to global warming,the ecosystem dynamics of the Tibetan Plateau are regulated by the interaction between the westerlies and monsoon circulation systems.Utilizing remote sensing observati...As a critical region sensitive to global warming,the ecosystem dynamics of the Tibetan Plateau are regulated by the interaction between the westerlies and monsoon circulation systems.Utilizing remote sensing observations,this study quantifies the relative contributions of three climatic zones(monsoon,transition,and westerlies)to the evolution of gross primary productivity(GPP)and identifies their respective climatic drivers.Results reveal that while the monsoon zone dominates the plateau-wide GPP for the mean state(86.07%),long-term trend(69.84%),and interannual variability(81.80%),its relative contributions to GPP changes(i.e.,long-term trends and interannual variability)are proportionally lower than to the mean state.Conversely,both the transition and westerlies zones exhibit proportionally higher contributions to GPP changes relative to their mean-state contributions.Temperature is the primary driver of the long-term GPP increase across the Tibetan Plateau and its subregions,though with a weaker contribution rate(57.26%)in the transition zone compared with the monsoon(77.88%)and westerlies zones(71.35%).The interannual variability of GPP across both the entire plateau and its subregions is also dominated by temperature,yet process-based ecosystem models fail to replicate this dominant temperature control.Our study elucidates complex GPP-climate interactions under the westerlies-monsoon synergy,highlighting the imperative to improve model parameterization for accurately capturing interannual variability in alpine ecosystem dynamics.展开更多
A decline in atmospheric oxygen concentration is projected in the 21st century given the background of global warming.The Qinghai-Tibetan Plateau is located at a high altitude,and thus,it faces a hypoxia challenge;how...A decline in atmospheric oxygen concentration is projected in the 21st century given the background of global warming.The Qinghai-Tibetan Plateau is located at a high altitude,and thus,it faces a hypoxia challenge;however,knowledge of the factors contributing to its atmospheric oxygen concentration is still lacking.Here,we conducted joint observations of ecosystem oxygen production and carbon sinks and near-surface atmospheric oxygen concentrations on the Qinghai-Tibetan Plateau and meteorological elements at Beijing Fangshan Station.Using seasonal differences and statistical methods,we calculated the relative contribution rates of vegetation to changes in atmospheric oxygen concentration.Our results indicate that solar radiation,atmospheric humidity,and ecosystem oxygen consumption and production have a significant impact on the atmospheric oxygen concentration,and the impact shows temporal and spatial differences.Vegetation significantly impacts the oxygen concentration,with a contribution rate of 16.7%–24.5%,which is underestimated in existing research.Our findings provide important insights into the factors that influence atmospheric oxygen concentration and highlight the contribution of vegetation.To better understand the oxygen dynamics of the Qinghai-Tibetan Plateau,we recommend further field observations of soil respiration and vegetation photosynthesis to clarify the contributions of carbon storage,carbon sinks and other factors to the near-surface atmospheric oxygen concentration.展开更多
Sustaining or enhancing nature's contributions to people(NCPs)requires a comprehensive understanding of both nature's contributions and people's needs.However,the 2 aspects for water-related NCPs are spati...Sustaining or enhancing nature's contributions to people(NCPs)requires a comprehensive understanding of both nature's contributions and people's needs.However,the 2 aspects for water-related NCPs are spatially mismatched.We introduced an assessment framework for water-related NCPs from a spatial flow perspective,considering the local nature's contributions assessed using the In VEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model,as well as people's needs in the downstream assessed via a distance decay method.We assessed 3 water-related NCPs'spatial distribution and correlation on the Loess Plateau from 2000 to 2020,where a large-scale ecological restoration was implemented that may affect downstream people.The results showed that NCP6(downstream needs from water yield)showed no increasing trend in the majority watersheds over the past 20 years,in contrast to NCP7(downstream needs from water purification)and NCP8(downstream needs from soil conservation).There are spatial synergies among NCP6,NCP7,and NCP8.From 2000 to 2020,the spatial synergy between NCP7 and NCP8 increased while decreased between other NCPs.The temporal dynamics of NCP6 and NCP8 showed a trade-off,while NCP6 and NCP7 showed a synergy.NCP7 and NCP8,in turn,showed a transition from synergy to trade-off.Guided by nature's contributions and people's needs,we proposed 3 ecological measures:thinning and intermediate cutting measures,control nonpoint source pollution,and soil and water conservation projects to promote ecological restoration.This assessment can offer multifunctional guidance for planning ecological conservation and restoration in the upstream based on people's needs in the downstream.展开更多
Crop yields are affected by climate change and technological advancement.Objectively and quantitatively evaluating the attribution of crop yield change to climate change and technological advancement will ensure susta...Crop yields are affected by climate change and technological advancement.Objectively and quantitatively evaluating the attribution of crop yield change to climate change and technological advancement will ensure sustainable development of agriculture under climate change.In this study,daily climate variables obtained from 553 meteorological stations in China for the period 1961-2010,detailed observations of maize from 653 agricultural meteorological stations for the period 1981-2010,and results using an Agro-Ecological Zones（AEZ） model,are used to explore the attribution of maize（Zea mays L.） yield change to climate change and technological advancement.In the AEZ model,the climatic potential productivity is examined through three step-by-step levels：photosynthetic potential productivity,photosynthetic thermal potential productivity,and climatic potential productivity.The relative impacts of different climate variables on climatic potential productivity of maize from 1961 to 2010 in China are then evaluated.Combined with the observations of maize,the contributions of climate change and technological advancement to maize yield from 1981 to 2010 in China are separated.The results show that,from 1961 to 2010,climate change had a significant adverse impact on the climatic potential productivity of maize in China.Decreased radiation and increased temperature were the main factors leading to the decrease of climatic potential productivity.However,changes in precipitation had only a small effect.The maize yields of the 14 main planting provinces in China increased obviously over the past 30 years,which was opposite to the decreasing trends of climatic potential productivity.This suggests that technological advancement has offset the negative effects of climate change on maize yield.Technological advancement contributed to maize yield increases by 99.6%-141.6%,while climate change contribution was from-41.4%to 0.4%.In particular,the actual maize yields in Shandong,Henan,Jilin,and Inner Mongolia increased by 98.4,90.4,98.7,and 121.5 kg hm^（-2） yr^（-1） over the past 30 years,respectively.Correspondingly,the maize yields affected by technological advancement increased by 113.7,97.9,111.5,and 124.8 kg hm^（-2） yr^（-1）,respectively.On the contrary,maize yields reduced markedly under climate change,with an average reduction of-9.0 kg hm^（-2） yr^（-1）.Our findings highlight that agronomic technological advancement has contributed dominantly to maize yield increases in China in the past three decades.展开更多
The NO formation experiments simulating moderate and intense low-oxygen dilution(MILD)oxy-coal combustion conditions were conducted on a laminar diffusion flame burner with the coflow temperatures of 1473-1873 K and t...The NO formation experiments simulating moderate and intense low-oxygen dilution(MILD)oxy-coal combustion conditions were conducted on a laminar diffusion flame burner with the coflow temperatures of 1473-1873 K and the oxygen volume fractions of 5%-20%in O_(2)/CO_(2),O_(2)/Ar and O_(2)/N_(2)atmospheres.The flame images of pulverized coal combustion were captured to obtain the ignition delay distances,and the axial species concentrations were measured to obtain the variation of NO formation and reduction.The NO yield in O_(2)/Ar atmosphere decreased by nearly 0.2 when the oxygen volume fraction decreased from 20%to 5%and by about 0.05 when the coflow temperature decreased from 1873 K to 1473 K.The NO yield in O_(2)/CO_(2)atmosphere was 0.1-0.15 lower than that in O_(2)/Ar atmosphere.The optimal kinetic parameters of thermal NO and fuel NO formation rate were obtained by a nonlinear fit of nth-order Arrhenius expression.Finally,the relative contribution rates of thermal NO to total NO(Rth)and NO reduction to fuel NO(Rre)were quantitatively separated.Rth decreases with the increase of oxygen volume fraction,below 6%at 1800 K,25%at 2000 K.Rre is almost unaffected by the coflow temperature and affected by the oxygen volume fraction,reaching 30%at 5%O_(2).展开更多
An India-China Joint Medical Mission was launched on January 14 to help improve rural public health in the two countries.The joint mission was set up to commemorate the 70th anniversary of the Indian Medical Mission.T...An India-China Joint Medical Mission was launched on January 14 to help improve rural public health in the two countries.The joint mission was set up to commemorate the 70th anniversary of the Indian Medical Mission.The mission was sent to China in 1938 to provide medical assistance during China’s War of Resistance Against Japanese Aggression(1937-45). Chinese Premier Wen J iabao and visiting Indian Prime Minister Manmohan Singh attended the launch ceremony of the joint medical mission in the Great Hall of the People in Beijing and presented certificates to the mission mem-展开更多
基金National Natural Sciences Foundation of China,No.41871021。
文摘Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index(MODIS NDVI)and climate data,a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land.Data were collected during the growing season between 2001 and 2020.Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes.Results revealed a predominantly increasing trend for average NDVI.The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences.The area with improved vegetation was greater than that of the degraded region.Climate variability and human activities were driving forces controlling vegetation cover changes,and their effects on vegetation dynamics varied by region.The response of vegetation dynamics was stronger for precipitation than temperature,indicating that precipitation was the main climate variable influencing the NDVI changes.The relative role of human activities was responsible for>70%of the changes,demonstrating that human activities were the main driving factor of the NDVI changes.The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality.These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.
基金the National Key R&D Program of China(Grant No.2017YFC0505603)the Special Fund for Basic Scientific Research of Central Colleges,China University of Geosciences,Wuhan.
文摘Climate,land use and land cover(LULC)changes are among the primary driving forces of soil loss.Decoupling their effects can help in understanding the magnitude and trend of soil loss in response to human activities and ecosystem management.Here,the RUSLE model was applied to estimate the spatial-temporal variations of soil loss rate in the Three Gorges Reservoir(TGR)area during 2001-2015,followed by a scenario design to decouple the effects of climate and LULC changes.The results showed that increasing rainfall generated as much as 2.90×10^(7)t soil loss in the TGR area.However,such effect was offset by changes in LULC particularly afforestation,which retained about 1.10×10^(7)t soil annually.Other human activities such as dam development and urbanization aggravated soil loss by as much as 1.40×10^(6)t annually.Because of land use policies that favor economic development,distinct spatial variances of soil loss were observed in TGR area.Soil loss in some counties located downstream of the TGR area(i.e.,close to the dam)was more influenced by dam development,but soil loss in the other counties was more influenced by urbanization.As climate change(i.e.,increasing rainfall)did not affect plant performance in TGR area,our findings suggested that ecological restoration was more beneficial to curb the amount of soil loss caused by urbanization and dam construction.
基金supported by the National Natural Science Foundation of China(No.42077151)the Earmarked Fund for China Agriculture Research System(No.CARS-13).
文摘Roots and shells are two potential organs through which peanut plants absorb cadium(Cd)from soils;however,the relative contributions of the two uptake pathways(root uptake and shell absorption)to kernel Cd accumulation and their translocation characteristics are poorly understood.In this study,the relative contributions of the two pathways to Cd accumulation in two peanut cultivars,Xianghua2008(XH)and Yueyou43(YY),were accurately assessed by labeling rooting and podding zone soils with 113Cd and 111Cd isotopes(0.3 mg kg^(-1) dry soil),respectively,in a split-pot design.The results showed that approximately 96%of the Cd accumulated in the peanut kernels was derived from root uptake,while only 4%originated from shell absorption.Only 1%of the Cd accumulated in whole peanut plants was attributed to shell absorption,of which 41%–44%was retained in shells and 56%–59%was translocated to kernels.In contrast,the Cd absorbed by roots was efficiently translocated into all plant organs,of which 80%–84%was distributed in shoots.Although YY accumulated 1.3 times more Cd in whole plants than XH,the relative contributions of the two pathways to Cd accumulation in each plant organ were barely affected by peanut cultivars.Due to the strong retention effect of shells,shell-derived Cd was approximately 2 times higher than root-derived Cd in shells.These results would improve the understanding of Cd accumulation processes in peanut plants,revealing that the root uptake pathway contributes predominantly to the Cd concentration in peanut kernels,based on which strategies and technology for the reduction of Cd in peanut plants could be designed and developed.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0106)the National Natural Science Foundation of China(Grant No.42141007)。
文摘As a critical region sensitive to global warming,the ecosystem dynamics of the Tibetan Plateau are regulated by the interaction between the westerlies and monsoon circulation systems.Utilizing remote sensing observations,this study quantifies the relative contributions of three climatic zones(monsoon,transition,and westerlies)to the evolution of gross primary productivity(GPP)and identifies their respective climatic drivers.Results reveal that while the monsoon zone dominates the plateau-wide GPP for the mean state(86.07%),long-term trend(69.84%),and interannual variability(81.80%),its relative contributions to GPP changes(i.e.,long-term trends and interannual variability)are proportionally lower than to the mean state.Conversely,both the transition and westerlies zones exhibit proportionally higher contributions to GPP changes relative to their mean-state contributions.Temperature is the primary driver of the long-term GPP increase across the Tibetan Plateau and its subregions,though with a weaker contribution rate(57.26%)in the transition zone compared with the monsoon(77.88%)and westerlies zones(71.35%).The interannual variability of GPP across both the entire plateau and its subregions is also dominated by temperature,yet process-based ecosystem models fail to replicate this dominant temperature control.Our study elucidates complex GPP-climate interactions under the westerlies-monsoon synergy,highlighting the imperative to improve model parameterization for accurately capturing interannual variability in alpine ecosystem dynamics.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(Grant Nos.2019QZKK0606&2019QZKK0906)。
文摘A decline in atmospheric oxygen concentration is projected in the 21st century given the background of global warming.The Qinghai-Tibetan Plateau is located at a high altitude,and thus,it faces a hypoxia challenge;however,knowledge of the factors contributing to its atmospheric oxygen concentration is still lacking.Here,we conducted joint observations of ecosystem oxygen production and carbon sinks and near-surface atmospheric oxygen concentrations on the Qinghai-Tibetan Plateau and meteorological elements at Beijing Fangshan Station.Using seasonal differences and statistical methods,we calculated the relative contribution rates of vegetation to changes in atmospheric oxygen concentration.Our results indicate that solar radiation,atmospheric humidity,and ecosystem oxygen consumption and production have a significant impact on the atmospheric oxygen concentration,and the impact shows temporal and spatial differences.Vegetation significantly impacts the oxygen concentration,with a contribution rate of 16.7%–24.5%,which is underestimated in existing research.Our findings provide important insights into the factors that influence atmospheric oxygen concentration and highlight the contribution of vegetation.To better understand the oxygen dynamics of the Qinghai-Tibetan Plateau,we recommend further field observations of soil respiration and vegetation photosynthesis to clarify the contributions of carbon storage,carbon sinks and other factors to the near-surface atmospheric oxygen concentration.
基金supported by the National Natural Science Foundation of China(Nos.42041007,U2243601,and 42201306)the Fundamental Research Funds for the Central Universities of China
文摘Sustaining or enhancing nature's contributions to people(NCPs)requires a comprehensive understanding of both nature's contributions and people's needs.However,the 2 aspects for water-related NCPs are spatially mismatched.We introduced an assessment framework for water-related NCPs from a spatial flow perspective,considering the local nature's contributions assessed using the In VEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model,as well as people's needs in the downstream assessed via a distance decay method.We assessed 3 water-related NCPs'spatial distribution and correlation on the Loess Plateau from 2000 to 2020,where a large-scale ecological restoration was implemented that may affect downstream people.The results showed that NCP6(downstream needs from water yield)showed no increasing trend in the majority watersheds over the past 20 years,in contrast to NCP7(downstream needs from water purification)and NCP8(downstream needs from soil conservation).There are spatial synergies among NCP6,NCP7,and NCP8.From 2000 to 2020,the spatial synergy between NCP7 and NCP8 increased while decreased between other NCPs.The temporal dynamics of NCP6 and NCP8 showed a trade-off,while NCP6 and NCP7 showed a synergy.NCP7 and NCP8,in turn,showed a transition from synergy to trade-off.Guided by nature's contributions and people's needs,we proposed 3 ecological measures:thinning and intermediate cutting measures,control nonpoint source pollution,and soil and water conservation projects to promote ecological restoration.This assessment can offer multifunctional guidance for planning ecological conservation and restoration in the upstream based on people's needs in the downstream.
基金Supported by the National Natural Science Foundation of China(31371530)China Meteorological Administration Special Public Welfare Research Fund(GYHY201106020)China Meteorological Administration Special Climate Change Research Fund(CCSF201346)
文摘Crop yields are affected by climate change and technological advancement.Objectively and quantitatively evaluating the attribution of crop yield change to climate change and technological advancement will ensure sustainable development of agriculture under climate change.In this study,daily climate variables obtained from 553 meteorological stations in China for the period 1961-2010,detailed observations of maize from 653 agricultural meteorological stations for the period 1981-2010,and results using an Agro-Ecological Zones（AEZ） model,are used to explore the attribution of maize（Zea mays L.） yield change to climate change and technological advancement.In the AEZ model,the climatic potential productivity is examined through three step-by-step levels：photosynthetic potential productivity,photosynthetic thermal potential productivity,and climatic potential productivity.The relative impacts of different climate variables on climatic potential productivity of maize from 1961 to 2010 in China are then evaluated.Combined with the observations of maize,the contributions of climate change and technological advancement to maize yield from 1981 to 2010 in China are separated.The results show that,from 1961 to 2010,climate change had a significant adverse impact on the climatic potential productivity of maize in China.Decreased radiation and increased temperature were the main factors leading to the decrease of climatic potential productivity.However,changes in precipitation had only a small effect.The maize yields of the 14 main planting provinces in China increased obviously over the past 30 years,which was opposite to the decreasing trends of climatic potential productivity.This suggests that technological advancement has offset the negative effects of climate change on maize yield.Technological advancement contributed to maize yield increases by 99.6%-141.6%,while climate change contribution was from-41.4%to 0.4%.In particular,the actual maize yields in Shandong,Henan,Jilin,and Inner Mongolia increased by 98.4,90.4,98.7,and 121.5 kg hm^（-2） yr^（-1） over the past 30 years,respectively.Correspondingly,the maize yields affected by technological advancement increased by 113.7,97.9,111.5,and 124.8 kg hm^（-2） yr^（-1）,respectively.On the contrary,maize yields reduced markedly under climate change,with an average reduction of-9.0 kg hm^（-2） yr^（-1）.Our findings highlight that agronomic technological advancement has contributed dominantly to maize yield increases in China in the past three decades.
基金supported by the National Natural Science Foundation of China(grant number:51976120).
文摘The NO formation experiments simulating moderate and intense low-oxygen dilution(MILD)oxy-coal combustion conditions were conducted on a laminar diffusion flame burner with the coflow temperatures of 1473-1873 K and the oxygen volume fractions of 5%-20%in O_(2)/CO_(2),O_(2)/Ar and O_(2)/N_(2)atmospheres.The flame images of pulverized coal combustion were captured to obtain the ignition delay distances,and the axial species concentrations were measured to obtain the variation of NO formation and reduction.The NO yield in O_(2)/Ar atmosphere decreased by nearly 0.2 when the oxygen volume fraction decreased from 20%to 5%and by about 0.05 when the coflow temperature decreased from 1873 K to 1473 K.The NO yield in O_(2)/CO_(2)atmosphere was 0.1-0.15 lower than that in O_(2)/Ar atmosphere.The optimal kinetic parameters of thermal NO and fuel NO formation rate were obtained by a nonlinear fit of nth-order Arrhenius expression.Finally,the relative contribution rates of thermal NO to total NO(Rth)and NO reduction to fuel NO(Rre)were quantitatively separated.Rth decreases with the increase of oxygen volume fraction,below 6%at 1800 K,25%at 2000 K.Rre is almost unaffected by the coflow temperature and affected by the oxygen volume fraction,reaching 30%at 5%O_(2).
文摘An India-China Joint Medical Mission was launched on January 14 to help improve rural public health in the two countries.The joint mission was set up to commemorate the 70th anniversary of the Indian Medical Mission.The mission was sent to China in 1938 to provide medical assistance during China’s War of Resistance Against Japanese Aggression(1937-45). Chinese Premier Wen J iabao and visiting Indian Prime Minister Manmohan Singh attended the launch ceremony of the joint medical mission in the Great Hall of the People in Beijing and presented certificates to the mission mem-
