With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbi...With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbial decomposition of large amounts of frozen organic carbon (C), releasing greenhouse gases such as carbon dioxide (CO_(2)) and methane (CH4). However, little research has been done on the thermo-water-vapor-carbon coupling process in permafrost, and the interactions among hydrothermal transport, organic matter decomposition, and CO_(2) transport processes in permafrost remain unclear. We considered the decomposition and release of organic C and established a coupled thermo-water-vapor-carbon model for permafrost based on the study area located in the Beiluhe region of the Qingzang Plateau, China. The model established accurately reflected changes in permafrost temperature, moisture, and C fluxes. Dramatic changes in temperature and precipitation in the warm season led to significant soil water and heat transport, CO_(2) transport, and organic matter decomposition. During the cold season, however, the soil froze, which weakened organic matter decomposition and CO_(2) transport. The sensitivity of soil layers to changes in the external environment varied with depth. Fluctuations in energy, water, and CO_(2) fluxes were greater in shallow soil layers than in deeper ones. The latent heat of water-vapor and water-ice phase changes played a crucial role in regulating the temperature of frozen soil. The low content of soil organic matter in the study area resulted in a smaller influence of the decomposition heat of soil organic matter on soil temperature, compared to the high organic matter content in other soil types (such as peatlands).展开更多
The deep underground engineering will face high-temperature and ultrahigh-pressure(HTUP)condition.Indoor triaxial testing is an important means to investigate this challenge in rock mechanics and rock engineering.Heat...The deep underground engineering will face high-temperature and ultrahigh-pressure(HTUP)condition.Indoor triaxial testing is an important means to investigate this challenge in rock mechanics and rock engineering.Heat-shrinkable tubing,as a seal on the rock surface,is crucial for reconstructing deep rock in situ conditions(ensuring the accuracy and effectiveness of confining pressure and pore pressure).However,there are few reports on testing such material under HTUP condition.Thus,the mechanical and sealing performances of existing heat-shrinkable tubing under HTUP condition is still immature.The motivation of this study is to advance deep rock mechanics and engineering by developing a polymer heat-shrinkable tubing(pressure larger than 140 MPa and temperature greater than 150℃).Experiments using the deep rock in situ thermal insulation coring test system were conducted and compared with conventional heat-shrinkable tubing.The sealing performance of the polymer heat-shrinkable tubing was investigated.The results indicated that deep rock ultrahigh-pressure condition and natural damage to the rock surface are the main causes of conventional heat-shrinkable tubing failure.In contrast,the damage rate of the proposed polymer heat-shrinkable tubing is extremely low,indicating that incorporating base material with high-performances can significantly enhance the pressure resistance of polymer heat-shrinkable tubing.Additionally,through the analysis of experimental results and the three-dimensional(3D)morphology of rock surfaces,the failure behavior of heat-shrinkable tubing under HTUP condition was revealed at the meso-structural level,and the proposed failure criteria,taking into account 3D morphology of rock surfaces and applicable to HTUP condition,have been advanced.The findings offer possibilities for triaxial rock mechanics testing in HTUP condition,providing theoretical and technical support for experiments and engineering applications in deep rock mechanics.展开更多
Chestnut is a high nutritional value food that has been widely used as a tonic in traditional Chinese medicine.As an emerging functional food ingredient,Chinese chestnuts are rich in a range of bioactive nutrients suc...Chestnut is a high nutritional value food that has been widely used as a tonic in traditional Chinese medicine.As an emerging functional food ingredient,Chinese chestnuts are rich in a range of bioactive nutrients such as starch,dietary fiber,fat,protein,trace metal element and vitamins A,B,C,D and other nutrients.In our study,Chinese chestnut powder(CCP)were added into bread formulation at 2%-6%levels(based on flour weight)to produce fresh bread with enhanced anti-staling characteristics and starch digestion inhibitory ability.The texture properties,retrogradation enthalpy,water distribution,and estimated glycemic index(eGI)of wheat bread containing CCP as a functional additive were also investigated.The results showed that incorporation of CCP apparently affected bread texture,resulting in increased hardness,as well as decreased the specific volume of wheat bread.These influences were generally proportional to the amount of CCP used.It was found that adding too much CCP resulted in a dark red color,showing increased significantly higher total color difference(ΔE)and L values.Conversely,addition of CCP significantly reduced starch digestion rate and digestion extent in bread,and the reduction degree was positively related to the amount of CCP applied.The greatest reduction in eGI value from 79.40(control)to 75.02(6%CPP bread)was observed.Meanwhile,the content of resistant starch of 6%CPP bread was about 1.36 times higher than that of control bread.CCP also reduced crumb water loss and drove the water shift from the bound to the mobile state after stored for 7 days.The retrogradation enthalpy analyses further confirmed that CCP inhibited starch retrogradation and recrystallization.These results suggested that Chinese chestnut powder could be incorporated into fresh bread to provide health functions,such as lowering potential glycaemic response and improving anti-staling characteristics of bread.展开更多
Offshore structures are generally classified as small-scale structures or large-scale structures.Their wave forces are then estimated by Morison equation and diffraction/radiation theories,respectively.However,the cla...Offshore structures are generally classified as small-scale structures or large-scale structures.Their wave forces are then estimated by Morison equation and diffraction/radiation theories,respectively.However,the classification criterion is not well quantified.In the present paper,a numerical wave flume is established to simulate the wave forces acting on a fixed and vertical surface-piercing circular cylinder under linear waves.By solving Navier–Stokes equation and Euler equation with free surface involved,respectively,the viscous force and inertia force are separated accurately.The variation of viscous force and inertia force with the cylinder diameter to wave length ratio is discussed in detail.The scale intervals for significant viscous and diffraction effects are given.The error caused by neglecting viscous and diffraction forces is quantitatively analyzed.Based on these analysis,the concept of medium-scale structure is proposed and the classification criteria for small-,medium-and large-scale structures are given.In the meantime,the estimation methods of wave forces for different scales of structures are suggested.展开更多
Background:Digital hemispherical photography(DHP)is widely used to estimate the leaf area index(LAI)of forest plots due to its advantages of high efficiency and low cost.A crucial step in the LAI estimation of forest ...Background:Digital hemispherical photography(DHP)is widely used to estimate the leaf area index(LAI)of forest plots due to its advantages of high efficiency and low cost.A crucial step in the LAI estimation of forest plots via DHP is choosing a sampling scheme.However,various sampling schemes involving DHP have been used for the LAI estimation of forest plots.To date,the impact of sampling schemes on LAI estimation from DHP has not been comprehensively investigated.Methods:In this study,13 commonly used sampling schemes which belong to five sampling types(i.e.dispersed,square,cross,transect and circle)were adopted in the LAI estimation of five Larix principis-rupprechtii plots(25m×25 m).An additional sampling scheme(with a sample size of 89)was generated on the basis of all the sample points of the 13 sampling schemes.Three typical inversion models and four canopy element clumping index(Ωe)algorithms were involved in the LAI estimation.The impacts of the sampling schemes on four variables,including gap fraction,Ωe,effective plant area index(PAIe)and LAI estimation from DHP were analysed.The LAI estimates obtained with different sampling schemes were then compared with those obtained from litter collection measurements.Results:Large differences were observed for all four variable estimates(i.e.gap fraction,Ωe,PAIe and LAI)under different sampling schemes.The differences in impact of sampling schemes on LAI estimation were not obvious for the three inversion models,if the fourΩe algorithms,except for the traditional gap-size analysis algorithm were adopted in the estimation.The accuracy of LAI estimation was not always improved with an increase in sample size.Moreover,results indicated that with the appropriate inversion model,Ωe algorithm and sampling scheme,the maximum estimation error of DHP-estimated LAI at elementary sampling unit can be less than 20%,which is required by the global climate observing system,except in forest plots with extremely large LAI values(~>6.0).However,obtaining an LAI from DHP with an estimation error lower than 5%is impossible regardless of which combination of inversion model,Ωe algorithm and sampling scheme is used.Conclusion:The LAI estimation of L.principis-rupprechtii forests from DHP was largely affected by the sampling schemes adopted in the estimation.Thus,the sampling scheme should be seriously considered in the LAI estimation.One square and two transect sampling schemes(with sample sizes ranging from 3 to 9)were recommended to be used to estimate the LAI of L.principis-rupprechtii forests with the smallest mean relative error(MRE).By contrast,three cross and one dispersed sampling schemes were identified to provide LAI estimates with relatively large MREs.展开更多
[Objectives]This study aims to investigate the effects of Dachengqi decoctions made from different processed products of rhubarb on water intake,defecation amount,urination amount,urination volume,dryness of stool,men...[Objectives]This study aims to investigate the effects of Dachengqi decoctions made from different processed products of rhubarb on water intake,defecation amount,urination amount,urination volume,dryness of stool,mental state and activity of ABP mice.[Methods]Total 165 mice were randomly divided into Dachengqi decoction groups(made from different processed products of rhubarb,6 and 10 g/kg),positive control group,blank control group and model group.The administration dosage was 20 mL/kg.With the metabolic cage integral method,the effects of Dachengqi decoctions made from different processed products of rhubarb on the water intake,defecation amount,urination volume,dryness of stool,mental state and activity of ABP mice were compared.[Results]Dachengqi decoctions all could soften stool and promote rapid defecation of the mice with fecal peritonitis of excess heat stagnation type except that made from carbonized rhubarb.The water intakes of all the Dachengqi decoction groups were higher than those of the positive control group and the model group,except the carbonized rhubarb-made Dachengqi decoction groups.[Conclusions]Dachengqi decoctions all have obvious purgative effect except those made from carbonized rhubarb.展开更多
基金the financial support from the National Natural Science Foundation of China(No.U22A20596).
文摘With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbial decomposition of large amounts of frozen organic carbon (C), releasing greenhouse gases such as carbon dioxide (CO_(2)) and methane (CH4). However, little research has been done on the thermo-water-vapor-carbon coupling process in permafrost, and the interactions among hydrothermal transport, organic matter decomposition, and CO_(2) transport processes in permafrost remain unclear. We considered the decomposition and release of organic C and established a coupled thermo-water-vapor-carbon model for permafrost based on the study area located in the Beiluhe region of the Qingzang Plateau, China. The model established accurately reflected changes in permafrost temperature, moisture, and C fluxes. Dramatic changes in temperature and precipitation in the warm season led to significant soil water and heat transport, CO_(2) transport, and organic matter decomposition. During the cold season, however, the soil froze, which weakened organic matter decomposition and CO_(2) transport. The sensitivity of soil layers to changes in the external environment varied with depth. Fluctuations in energy, water, and CO_(2) fluxes were greater in shallow soil layers than in deeper ones. The latent heat of water-vapor and water-ice phase changes played a crucial role in regulating the temperature of frozen soil. The low content of soil organic matter in the study area resulted in a smaller influence of the decomposition heat of soil organic matter on soil temperature, compared to the high organic matter content in other soil types (such as peatlands).
基金funding provided by the National Natural Science Foundation of China(Grant Nos.51827901 and 52174084)the Natural Science Foundation of Sichuan Provence,China(Grant No.2022NSFSC0005).
文摘The deep underground engineering will face high-temperature and ultrahigh-pressure(HTUP)condition.Indoor triaxial testing is an important means to investigate this challenge in rock mechanics and rock engineering.Heat-shrinkable tubing,as a seal on the rock surface,is crucial for reconstructing deep rock in situ conditions(ensuring the accuracy and effectiveness of confining pressure and pore pressure).However,there are few reports on testing such material under HTUP condition.Thus,the mechanical and sealing performances of existing heat-shrinkable tubing under HTUP condition is still immature.The motivation of this study is to advance deep rock mechanics and engineering by developing a polymer heat-shrinkable tubing(pressure larger than 140 MPa and temperature greater than 150℃).Experiments using the deep rock in situ thermal insulation coring test system were conducted and compared with conventional heat-shrinkable tubing.The sealing performance of the polymer heat-shrinkable tubing was investigated.The results indicated that deep rock ultrahigh-pressure condition and natural damage to the rock surface are the main causes of conventional heat-shrinkable tubing failure.In contrast,the damage rate of the proposed polymer heat-shrinkable tubing is extremely low,indicating that incorporating base material with high-performances can significantly enhance the pressure resistance of polymer heat-shrinkable tubing.Additionally,through the analysis of experimental results and the three-dimensional(3D)morphology of rock surfaces,the failure behavior of heat-shrinkable tubing under HTUP condition was revealed at the meso-structural level,and the proposed failure criteria,taking into account 3D morphology of rock surfaces and applicable to HTUP condition,have been advanced.The findings offer possibilities for triaxial rock mechanics testing in HTUP condition,providing theoretical and technical support for experiments and engineering applications in deep rock mechanics.
基金This research has been financially supported by National Key R&D Program of China(2019YFD1002300)Open Project Program of Grain,Oil and Food Engineering Technology Research Center of the State Grain and Reserves Administration/Key Laboratory of Henan Province,Henan University of Technology(GO202216)+1 种基金Doctor Foundation of Henan University of Technology(2019BS057)Cultivation Programme for Young Backbone Teachers in Henan University of Technology for financial support(21420187).
文摘Chestnut is a high nutritional value food that has been widely used as a tonic in traditional Chinese medicine.As an emerging functional food ingredient,Chinese chestnuts are rich in a range of bioactive nutrients such as starch,dietary fiber,fat,protein,trace metal element and vitamins A,B,C,D and other nutrients.In our study,Chinese chestnut powder(CCP)were added into bread formulation at 2%-6%levels(based on flour weight)to produce fresh bread with enhanced anti-staling characteristics and starch digestion inhibitory ability.The texture properties,retrogradation enthalpy,water distribution,and estimated glycemic index(eGI)of wheat bread containing CCP as a functional additive were also investigated.The results showed that incorporation of CCP apparently affected bread texture,resulting in increased hardness,as well as decreased the specific volume of wheat bread.These influences were generally proportional to the amount of CCP used.It was found that adding too much CCP resulted in a dark red color,showing increased significantly higher total color difference(ΔE)and L values.Conversely,addition of CCP significantly reduced starch digestion rate and digestion extent in bread,and the reduction degree was positively related to the amount of CCP applied.The greatest reduction in eGI value from 79.40(control)to 75.02(6%CPP bread)was observed.Meanwhile,the content of resistant starch of 6%CPP bread was about 1.36 times higher than that of control bread.CCP also reduced crumb water loss and drove the water shift from the bound to the mobile state after stored for 7 days.The retrogradation enthalpy analyses further confirmed that CCP inhibited starch retrogradation and recrystallization.These results suggested that Chinese chestnut powder could be incorporated into fresh bread to provide health functions,such as lowering potential glycaemic response and improving anti-staling characteristics of bread.
基金This work was supported by the National Key R&D Program of China(Grant 2017yfc1404200)the National Natural Science Foundation of China(Grant 11572332)and the Strategic Priority Research Program of the Chinese Academy of Sciences(Grants xdb22040203 and xda22OOOOOO).
文摘Offshore structures are generally classified as small-scale structures or large-scale structures.Their wave forces are then estimated by Morison equation and diffraction/radiation theories,respectively.However,the classification criterion is not well quantified.In the present paper,a numerical wave flume is established to simulate the wave forces acting on a fixed and vertical surface-piercing circular cylinder under linear waves.By solving Navier–Stokes equation and Euler equation with free surface involved,respectively,the viscous force and inertia force are separated accurately.The variation of viscous force and inertia force with the cylinder diameter to wave length ratio is discussed in detail.The scale intervals for significant viscous and diffraction effects are given.The error caused by neglecting viscous and diffraction forces is quantitatively analyzed.Based on these analysis,the concept of medium-scale structure is proposed and the classification criteria for small-,medium-and large-scale structures are given.In the meantime,the estimation methods of wave forces for different scales of structures are suggested.
基金the National Science Foundation of China(Grant Nos.41871233,41371330 , 41001203).
文摘Background:Digital hemispherical photography(DHP)is widely used to estimate the leaf area index(LAI)of forest plots due to its advantages of high efficiency and low cost.A crucial step in the LAI estimation of forest plots via DHP is choosing a sampling scheme.However,various sampling schemes involving DHP have been used for the LAI estimation of forest plots.To date,the impact of sampling schemes on LAI estimation from DHP has not been comprehensively investigated.Methods:In this study,13 commonly used sampling schemes which belong to five sampling types(i.e.dispersed,square,cross,transect and circle)were adopted in the LAI estimation of five Larix principis-rupprechtii plots(25m×25 m).An additional sampling scheme(with a sample size of 89)was generated on the basis of all the sample points of the 13 sampling schemes.Three typical inversion models and four canopy element clumping index(Ωe)algorithms were involved in the LAI estimation.The impacts of the sampling schemes on four variables,including gap fraction,Ωe,effective plant area index(PAIe)and LAI estimation from DHP were analysed.The LAI estimates obtained with different sampling schemes were then compared with those obtained from litter collection measurements.Results:Large differences were observed for all four variable estimates(i.e.gap fraction,Ωe,PAIe and LAI)under different sampling schemes.The differences in impact of sampling schemes on LAI estimation were not obvious for the three inversion models,if the fourΩe algorithms,except for the traditional gap-size analysis algorithm were adopted in the estimation.The accuracy of LAI estimation was not always improved with an increase in sample size.Moreover,results indicated that with the appropriate inversion model,Ωe algorithm and sampling scheme,the maximum estimation error of DHP-estimated LAI at elementary sampling unit can be less than 20%,which is required by the global climate observing system,except in forest plots with extremely large LAI values(~>6.0).However,obtaining an LAI from DHP with an estimation error lower than 5%is impossible regardless of which combination of inversion model,Ωe algorithm and sampling scheme is used.Conclusion:The LAI estimation of L.principis-rupprechtii forests from DHP was largely affected by the sampling schemes adopted in the estimation.Thus,the sampling scheme should be seriously considered in the LAI estimation.One square and two transect sampling schemes(with sample sizes ranging from 3 to 9)were recommended to be used to estimate the LAI of L.principis-rupprechtii forests with the smallest mean relative error(MRE).By contrast,three cross and one dispersed sampling schemes were identified to provide LAI estimates with relatively large MREs.
基金Supported by National Natural Science Foundation of China(81360524)National Traditional Chinese Medicine Characteristic Technology Inheritance Talent Training Project(20184828005)+2 种基金Youth Foundation of Guangxi University of Chinese Medicine(2019QN036)Natural Science Foundation of Guangxi(2020GXNSFAA259059)In-hospital Preparation Development Project of the First Affiliated Hospital of Guangxi University of Chinese Medicine(2017ZJ001).
文摘[Objectives]This study aims to investigate the effects of Dachengqi decoctions made from different processed products of rhubarb on water intake,defecation amount,urination amount,urination volume,dryness of stool,mental state and activity of ABP mice.[Methods]Total 165 mice were randomly divided into Dachengqi decoction groups(made from different processed products of rhubarb,6 and 10 g/kg),positive control group,blank control group and model group.The administration dosage was 20 mL/kg.With the metabolic cage integral method,the effects of Dachengqi decoctions made from different processed products of rhubarb on the water intake,defecation amount,urination volume,dryness of stool,mental state and activity of ABP mice were compared.[Results]Dachengqi decoctions all could soften stool and promote rapid defecation of the mice with fecal peritonitis of excess heat stagnation type except that made from carbonized rhubarb.The water intakes of all the Dachengqi decoction groups were higher than those of the positive control group and the model group,except the carbonized rhubarb-made Dachengqi decoction groups.[Conclusions]Dachengqi decoctions all have obvious purgative effect except those made from carbonized rhubarb.
