Discriminating internal layers by radio echo sounding is important in analyzing the thickness and ice deposits in the Antarctic ice sheet.The signal processing method of synthesis aperture radar(SAR)has been widely us...Discriminating internal layers by radio echo sounding is important in analyzing the thickness and ice deposits in the Antarctic ice sheet.The signal processing method of synthesis aperture radar(SAR)has been widely used for improving the signal to noise ratio(SNR)and discriminating internal layers by radio echo sounding data of ice sheets.This method is not efficient when we use edge detection operators to obtain accurate information of the layers,especially the ice-bed interface.This paper presents a new image processing method via a combined robust principal component analysis-total variation(RPCA-TV)approach for discriminating internal layers of ice sheets by radio echo sounding data.The RPCA-based method is adopted to project the high-dimensional observations to low-dimensional subspace structure to accelerate the operation of the TV-based method,which is used to discriminate the internal layers.The efficiency of the presented method has been tested on simulation data and the dataset of the Institute of Electronics,Chinese Academy of Sciences,collected during CHINARE 28.The results show that the new method is more efficient than the previous method in discriminating internal layers of ice sheets by radio echo sounding data.展开更多
During Antarctic region drilling,the interaction between the drilling fluid and ice layer constitutes a critical factor influencing drilling safety and efficiency.This study investigates in depth the adsorption-heat t...During Antarctic region drilling,the interaction between the drilling fluid and ice layer constitutes a critical factor influencing drilling safety and efficiency.This study investigates in depth the adsorption-heat transfer mechanism between drilling fluid(butyl acetate)and ice layer,as well as their implications for wellbore stability in the Antarctic region.To this end,a fully coupled model integrating adsorption mass transfer,fluid-solid heat transfer,and solid mechanics is developed.First,the relevant physical parameters of butyl acetate are measured experimentally.As the temperature decreases from 5℃ to-55℃,the density of butyl acetate varies from 0.88 to 0.96 g cm^(-3),the viscosity increases from 0.933 to 3.327 mPa s,the thermal conductivity rises from 0.140 to 0.157 W m^(-1)K^(-1);the enthalpy change associated with the adsorption of butyl acetate on the ice surface is 8.84 kJ mol^(-1).Then,numerical simulations of the model reveal that the heat exchange between the drilling fluid and ice layer causes an increase in the temperature of the ice layer near the wellbore,which significantly alters the physicomechanical properties of the ice layer and increases the risk of wellbore instability.Meanwhile,the adsorption of drilling fluid on the well wall proceeds as a dynamic equilibrium process that absorbs part of the heat,thereby mitigating the thermal impact and offering limited short-term protection to the wellbore.However,continued heat transfer ultimately reduces wellbore stability over time.The model is validated using a drilling case from the Antarctic Dome A area,achieving a 99%match with literature-reported failure depths.The critical wellbore failure depth decreases from 1649.02 to 1632.12 m when adsorption and heat transfer effects are accounted for.These findings provide a theoretical foundation and technical guidance for enhancing drilling safety and efficiency in the Antarctic region.展开更多
The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean(80°–88°N) are prese...The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean(80°–88°N) are presented by adopting GPS sounding data obtained by the 4th–6th Arctic expeditions of China and NCEP(National Centre for Environmental Prediction) reanalysis data. Obvious differences are observed regarding the tropopause, boundary layer height, temperature inversion, and vertical structure of wind speed and direction in the center Arctic Ocean in the summer of 2012, 2010, and 2014. These differences can be explained by the relations between temperature and changes in sea ice extent in September from 1979 to 2014. In September 2012, the Arctic sea ice extent decreased by 44% an with obvious warming process. In September 2010 and 2014, it decreased by 22.6% and 17% with an obvious cooling process, respectively. A comparison of the two processes shows that sea ice change has a significant influence on the structure of the atmospheric boundary layer. In the recent 30 years, the temperature changes of 1000 and 850 h Pa in the center of the Arctic Ocean have displayed an obvious warming trend and negative correlation with sea ice extent. These changes indicate that the continuous reduction of Arctic sea ice will continue the warming of the troposphere middle layer.展开更多
Nucleation of ice by contact takes place when an aerosol particle collides with asurface of supercooled water drop.Aerosol particle may either bounce off the watersurface or be captured on it.McCully et al.(1956) and ...Nucleation of ice by contact takes place when an aerosol particle collides with asurface of supercooled water drop.Aerosol particle may either bounce off the watersurface or be captured on it.McCully et al.(1956) and Rosinski et al.(1963) have shownthat capture of hydrophilic particles was four times larger than of hydrophobic ones.Hydrophobic aerosol particles will nucleate ice preferentially during the brief time ofcontact when they bounce off the surface.Patricles that become captured on the surfacewill float and produce clusters that may nucleate ice at some later time (delayed on surface展开更多
基金supported by the National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2011AA040202)the National Natural Science Foundation of China(Grant No.40976114)
文摘Discriminating internal layers by radio echo sounding is important in analyzing the thickness and ice deposits in the Antarctic ice sheet.The signal processing method of synthesis aperture radar(SAR)has been widely used for improving the signal to noise ratio(SNR)and discriminating internal layers by radio echo sounding data of ice sheets.This method is not efficient when we use edge detection operators to obtain accurate information of the layers,especially the ice-bed interface.This paper presents a new image processing method via a combined robust principal component analysis-total variation(RPCA-TV)approach for discriminating internal layers of ice sheets by radio echo sounding data.The RPCA-based method is adopted to project the high-dimensional observations to low-dimensional subspace structure to accelerate the operation of the TV-based method,which is used to discriminate the internal layers.The efficiency of the presented method has been tested on simulation data and the dataset of the Institute of Electronics,Chinese Academy of Sciences,collected during CHINARE 28.The results show that the new method is more efficient than the previous method in discriminating internal layers of ice sheets by radio echo sounding data.
基金supported by the National Natural Science Foundation of China(Grant No.52274021)the National Key Research and Development Program of China(Grant No.2021YFA0719102)。
文摘During Antarctic region drilling,the interaction between the drilling fluid and ice layer constitutes a critical factor influencing drilling safety and efficiency.This study investigates in depth the adsorption-heat transfer mechanism between drilling fluid(butyl acetate)and ice layer,as well as their implications for wellbore stability in the Antarctic region.To this end,a fully coupled model integrating adsorption mass transfer,fluid-solid heat transfer,and solid mechanics is developed.First,the relevant physical parameters of butyl acetate are measured experimentally.As the temperature decreases from 5℃ to-55℃,the density of butyl acetate varies from 0.88 to 0.96 g cm^(-3),the viscosity increases from 0.933 to 3.327 mPa s,the thermal conductivity rises from 0.140 to 0.157 W m^(-1)K^(-1);the enthalpy change associated with the adsorption of butyl acetate on the ice surface is 8.84 kJ mol^(-1).Then,numerical simulations of the model reveal that the heat exchange between the drilling fluid and ice layer causes an increase in the temperature of the ice layer near the wellbore,which significantly alters the physicomechanical properties of the ice layer and increases the risk of wellbore instability.Meanwhile,the adsorption of drilling fluid on the well wall proceeds as a dynamic equilibrium process that absorbs part of the heat,thereby mitigating the thermal impact and offering limited short-term protection to the wellbore.However,continued heat transfer ultimately reduces wellbore stability over time.The model is validated using a drilling case from the Antarctic Dome A area,achieving a 99%match with literature-reported failure depths.The critical wellbore failure depth decreases from 1649.02 to 1632.12 m when adsorption and heat transfer effects are accounted for.These findings provide a theoretical foundation and technical guidance for enhancing drilling safety and efficiency in the Antarctic region.
基金supported by the Program of China Polar Environment Investigation and Assessment (2016–2020)by the Project of MOST 973 (Grant No. 2015CB953900)
文摘The atmospheric vertical structure and changed characteristics of boundary layer parameters, as well as their relations with sea ice and temperature changes in the center of Arctic Ocean(80°–88°N) are presented by adopting GPS sounding data obtained by the 4th–6th Arctic expeditions of China and NCEP(National Centre for Environmental Prediction) reanalysis data. Obvious differences are observed regarding the tropopause, boundary layer height, temperature inversion, and vertical structure of wind speed and direction in the center Arctic Ocean in the summer of 2012, 2010, and 2014. These differences can be explained by the relations between temperature and changes in sea ice extent in September from 1979 to 2014. In September 2012, the Arctic sea ice extent decreased by 44% an with obvious warming process. In September 2010 and 2014, it decreased by 22.6% and 17% with an obvious cooling process, respectively. A comparison of the two processes shows that sea ice change has a significant influence on the structure of the atmospheric boundary layer. In the recent 30 years, the temperature changes of 1000 and 850 h Pa in the center of the Arctic Ocean have displayed an obvious warming trend and negative correlation with sea ice extent. These changes indicate that the continuous reduction of Arctic sea ice will continue the warming of the troposphere middle layer.
基金This work was supported by the National Natural Science Foundation of China under Project(49736200)National Basic Research 973 Project(G1999043503)
文摘Nucleation of ice by contact takes place when an aerosol particle collides with asurface of supercooled water drop.Aerosol particle may either bounce off the watersurface or be captured on it.McCully et al.(1956) and Rosinski et al.(1963) have shownthat capture of hydrophilic particles was four times larger than of hydrophobic ones.Hydrophobic aerosol particles will nucleate ice preferentially during the brief time ofcontact when they bounce off the surface.Patricles that become captured on the surfacewill float and produce clusters that may nucleate ice at some later time (delayed on surface
