In this study,the super typhoon KROSA(2007)was simulated using a mesoscale numerical model Global and Regional Assimilation and Prediction System(GRAPES)with a two-moment mixed-phase microphysics scheme.Local rainfall...In this study,the super typhoon KROSA(2007)was simulated using a mesoscale numerical model Global and Regional Assimilation and Prediction System(GRAPES)with a two-moment mixed-phase microphysics scheme.Local rainfall observations,radar and satellite data were also used to analyze the precipitation structure and microphysical features.It was shown that low-level jets and unstable temperature stratification provided this precipitation process with favorable weather condition.Heavy rainfall centers were located in the north and east part of KROSA with the maxima of 6-hourly total rainfall during the simulation more than 100 mm.The quantities of column solid water and column liquid water were generally equivalent,indicating the important role of ice phase in precipitation formation.Results of CloudSat showed that strong convection occurred in the eyewall around the cyclonic center.According to the simulation results,heavy precipitation in the northeast part of the typhoon was mainly triggered by convective clouds,accompanied by the strongest updraft under the melting level.In the southwest part of KROSA,precipitation intensity was rather homogeneous.The ascending center occurred in high-level cold clouds,favoring the formation and growth of ice particles.展开更多
Electrochemical conversion of CO_(2)(CO_(2)RR)into high-value fuel is identified as one of the promising approaches to achieve carbon neutrality.The synthesis of high-efficiency CO_(2)reduction electrocatalysts with h...Electrochemical conversion of CO_(2)(CO_(2)RR)into high-value fuel is identified as one of the promising approaches to achieve carbon neutrality.The synthesis of high-efficiency CO_(2)reduction electrocatalysts with high C_(2):C_(1) selectivity remains a field of intense interest.Previous studies have shown that the presence of Cu(I)is beneficial for the reduction of CO_(2)into C_(2)products.However,the stable presence of Cu(I)remains controversial,especially in the negative potential window.Here we report a simple and easily scalable catalyst precursor Cu_(2)(OH)_(3)Cl/C,which automatically forms in-situ chlorine-doped Cu/Cu_(2)O heterointerface during electrocatalysis.The catalyst not only exhibits a Faradaic efficiency of 33.03%but also provides a long-term stability of Cu^(+),gaining a stable electrolysis of 11 h,with an ethylene/methane ratio over 50.The experimental results and mechanistic studies confirm that the presence of Cl^(-)inhibits the reduction of Cu^(+),inducing the formation of Cu^(0)/Cu^(+),and reduces the reaction energy of the intermediate ^(*)CO dimerization,thereby facilitating the formation of C_(2)products.This work provides a feasible way to synthesize copper ions with long-term and stable positive charge in CO_(2)RR and expands a new way to synthesize ethylene industrial products in the future.展开更多
The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer （MODIS） and Cloud-Aerosol Lidar with Orthogonal Polarization （CAL...The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer （MODIS） and Cloud-Aerosol Lidar with Orthogonal Polarization （CALIOP） instruments for the period 2000-2006. We used the averaged fraction of liquid-phase clouds out of the total cloud amount at the cloud tops since the value is comparable in the two measurements. MODIS data for the winter months （June, July, and August） reveal liquid cloud fraction out of the total cloud amount significantly decreases with decreasing cloud-top temperature below 0°C. In addition, the CALIOP vertical profiles show that below the ice clouds, low-lying liquid clouds are distributed over ～20% of the area. With increasing latitude, the liquid cloud fraction decreases as a function of the local temperature. The MODIS-observed relation between the cloud-top liquid fraction and cloud-top temperature is then applied to evaluate the cloud phase parameterization in climate models, in which condensed cloud water is repartitioned between liquid water and ice on the basis of the grid point temperature. It is found that models assuming overly high cut-offs （ -40°C） for the separation of ice clouds from mixed-phase clouds may significantly underestimate the liquid cloud fraction in the winter Antarctic atmosphere. Correction of the bias in the liquid cloud fraction would serve to reduce the large uncertainty in cloud radiative effects.展开更多
The crystal form of TiO_2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO_2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO_2 on...The crystal form of TiO_2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO_2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO_2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO_2 nanoparticles with controllable phase ratios. We explored the role of the TiO_2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol(IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer-Emmett-Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants.展开更多
Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α...Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α and β phases can be obtained, and on the basis of this, mixed-phase Ga_2O_3 thin film solar-blind photodetectors(SBPDs) were prepared.Comparing the responsivities of the mixed-phase Ga_2O_3 SBPDs and the single β-Ga_2O_3 SBPDs at a bias voltage of 25 V,it is found that the former has a maximum responsivity of approximately 12 A/W, which is approximately two orders of magnitude larger than that of the latter. This result shows that the mixed-phase structure of Ga_2O_3 thin films can be used to prepare high-responsivity SBPDs. Moreover, the cause of this phenomenon was investigated, which will provide a feasible way to improve the responsivity of Ga_2O_3 thin film SBPDs.展开更多
Cloud microphysical properties including liquid and ice particle number concentration （NC）, liquid water content （LWC）, ice water content （IWC） and effective radius （RE） were retrieved from CloudSat data for a...Cloud microphysical properties including liquid and ice particle number concentration （NC）, liquid water content （LWC）, ice water content （IWC） and effective radius （RE） were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear （Pl） and two exponential （P2 and P3） functions, which estimate the liquid-phase fraction as a function of subfreezing temperature （from -20℃ to 0℃）, were tested. The retrieved NC, LWC, IWC and RE using Pl were on average larger than airplane measurements in the same cloud layer, Function P2 performed better than p1 or P3 in retrieving the NCs of cloud droplets in the convective cloud, while function Pl performed better in the stratus cloud. Function P3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the Pl function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function P1.展开更多
A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O...A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O3 nanofibers could be fabricated successfully by changing the synthesis parameters. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Raman spectroscopy, and nitrogen adsorption-desorption analyses were used to characterize the structures of the synthesized products. The optimal calcination conditions for preparing α-/γ-FeaO3 nanofibers with the highest ethanol response were determined through ethanol-sensing measurements. The mixed-phase material exhibited a significantly higher sensitivity than the corresponding purephase ones. The superior ethanol-sensing performance of the α-/γ-Fe2O3 nanofibers suggested that they may be suitable for use in alcohol sensing. Hence, a novel strategy for improving the sensing performance of metal oxide semiconductors is to assemble the different crystalline forms of the same metal oxide in one structure. Finally, the mechanism responsible for the sensing performance of α-/γ-Fe2O3 being higher than those of γ-Fe2O3 and α-Fe2O3 was elucidated on the basis of data from X-ray photoelectron spectroscopy and resistance measurements.展开更多
An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） a...An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） and using air as the working gas. The influences of the discharge voltage, IL and the amount of copper nitrite were investigated. X-ray diffraction, N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples. The results showed that the specific surface area of TiO2 was promoted with Cu-doping （from 57.6 m^2.g^-1 to 106.2 m^2.g^-1 with 3% Cu-doping）, and the content of anatase was increased. Besides, the band gap energy of TiO~ with Cu-doping decreased according to the UV-Vis spec- troscopy test. The 3%Cu-IL-TiO2 samples showed the highest eificiency in degrading methylene blue （MB） dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1, which was 1.2 times higher than that of non-doped samples. According to the characterization results, the reasons for the high photocatalytic activity were discussed.展开更多
Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of...Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of the SAP and soaked conditions on the surface morphology and photocatalytic activity of TiO2 on Ti coatings was investigated. With different SAP conditions,the surface morphologies of the TiO2 on Ti coatings clearly show the formed porous-like structure. With higher SA concentration,the porous-like structure becomes obviously. With extending soaked time,the porous-like structure tends to disappear. Raman spectroscopy reveals that the formed TiO2 coatings are with mixed-phase of anatase and rutile. Compared with those of SA concentration and SAP time,the influence of the soaked time on the phase transformation is obvious. Notably,the photocatalytic activity of TiO2 on Ti coatings had been efficiently enhanced by extending the soaked time,compared with those of higher SA concentration and longer SAP time. The enhanced photocatalytic activity of TiO2 on Ti coatings could be related with the changed surface morphology,mixed-phase of anatase and rutile,and formed hydroxyl groups.展开更多
基金"Abnormal Changes and Mechanism Study Before and After Typhoon Landing"(2009CB421500)from the National Key Basic Research Program(973 Program)
文摘In this study,the super typhoon KROSA(2007)was simulated using a mesoscale numerical model Global and Regional Assimilation and Prediction System(GRAPES)with a two-moment mixed-phase microphysics scheme.Local rainfall observations,radar and satellite data were also used to analyze the precipitation structure and microphysical features.It was shown that low-level jets and unstable temperature stratification provided this precipitation process with favorable weather condition.Heavy rainfall centers were located in the north and east part of KROSA with the maxima of 6-hourly total rainfall during the simulation more than 100 mm.The quantities of column solid water and column liquid water were generally equivalent,indicating the important role of ice phase in precipitation formation.Results of CloudSat showed that strong convection occurred in the eyewall around the cyclonic center.According to the simulation results,heavy precipitation in the northeast part of the typhoon was mainly triggered by convective clouds,accompanied by the strongest updraft under the melting level.In the southwest part of KROSA,precipitation intensity was rather homogeneous.The ascending center occurred in high-level cold clouds,favoring the formation and growth of ice particles.
基金This work was financially supported by the Natural Science Foundation of Henan province(No.212300410281)the National Key Research and Development Program of China(No.2020YFA0406104)the National Natural Science Foundation of China(No.22001263).
文摘Electrochemical conversion of CO_(2)(CO_(2)RR)into high-value fuel is identified as one of the promising approaches to achieve carbon neutrality.The synthesis of high-efficiency CO_(2)reduction electrocatalysts with high C_(2):C_(1) selectivity remains a field of intense interest.Previous studies have shown that the presence of Cu(I)is beneficial for the reduction of CO_(2)into C_(2)products.However,the stable presence of Cu(I)remains controversial,especially in the negative potential window.Here we report a simple and easily scalable catalyst precursor Cu_(2)(OH)_(3)Cl/C,which automatically forms in-situ chlorine-doped Cu/Cu_(2)O heterointerface during electrocatalysis.The catalyst not only exhibits a Faradaic efficiency of 33.03%but also provides a long-term stability of Cu^(+),gaining a stable electrolysis of 11 h,with an ethylene/methane ratio over 50.The experimental results and mechanistic studies confirm that the presence of Cl^(-)inhibits the reduction of Cu^(+),inducing the formation of Cu^(0)/Cu^(+),and reduces the reaction energy of the intermediate ^(*)CO dimerization,thereby facilitating the formation of C_(2)products.This work provides a feasible way to synthesize copper ions with long-term and stable positive charge in CO_(2)RR and expands a new way to synthesize ethylene industrial products in the future.
基金funded by Ko-rean Center for Atmospheric Sciences and Earthquake Re-search 2010–1178, and US Department of Energy grantDE-FG02-01ER63257
文摘The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer （MODIS） and Cloud-Aerosol Lidar with Orthogonal Polarization （CALIOP） instruments for the period 2000-2006. We used the averaged fraction of liquid-phase clouds out of the total cloud amount at the cloud tops since the value is comparable in the two measurements. MODIS data for the winter months （June, July, and August） reveal liquid cloud fraction out of the total cloud amount significantly decreases with decreasing cloud-top temperature below 0°C. In addition, the CALIOP vertical profiles show that below the ice clouds, low-lying liquid clouds are distributed over ～20% of the area. With increasing latitude, the liquid cloud fraction decreases as a function of the local temperature. The MODIS-observed relation between the cloud-top liquid fraction and cloud-top temperature is then applied to evaluate the cloud phase parameterization in climate models, in which condensed cloud water is repartitioned between liquid water and ice on the basis of the grid point temperature. It is found that models assuming overly high cut-offs （ -40°C） for the separation of ice clouds from mixed-phase clouds may significantly underestimate the liquid cloud fraction in the winter Antarctic atmosphere. Correction of the bias in the liquid cloud fraction would serve to reduce the large uncertainty in cloud radiative effects.
基金supported by the National Natural Science Foundation of China (Nos.21406164,21466035,51203111)the National Basic Research Program of China("973" program,Nos.2012CB720100,2014CB239300)
文摘The crystal form of TiO_2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO_2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO_2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO_2 nanoparticles with controllable phase ratios. We explored the role of the TiO_2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol(IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer-Emmett-Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51872187,51302174,11774241,and 61704111)the National Key Research and Development Program of China(Grant No.2017YFB0400304)+3 种基金the Natural Science Foundation of Guangdong Province,China(Grant Nos.2016A030313060 and 2017A030310524)the Project of Department of Education of Guangdong Province,China(Grant No.2014KTSCX110)the Fundamental Research Project of Shenzhen,China(Grant No.JCYJ20180206162132006)the Science and Technology Foundation of Shenzhen,China(Grant No.JCYJ2015-2018)
文摘Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α and β phases can be obtained, and on the basis of this, mixed-phase Ga_2O_3 thin film solar-blind photodetectors(SBPDs) were prepared.Comparing the responsivities of the mixed-phase Ga_2O_3 SBPDs and the single β-Ga_2O_3 SBPDs at a bias voltage of 25 V,it is found that the former has a maximum responsivity of approximately 12 A/W, which is approximately two orders of magnitude larger than that of the latter. This result shows that the mixed-phase structure of Ga_2O_3 thin films can be used to prepare high-responsivity SBPDs. Moreover, the cause of this phenomenon was investigated, which will provide a feasible way to improve the responsivity of Ga_2O_3 thin film SBPDs.
基金funded by the National Natural Science Foundation of China(Grant No.41475035)the Natural Science Foundation of Jiangsu Province(Grant No.BK20131433)+1 种基金the Foundations from KLME of NUIST(Grant No.KLME1206)the Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration of NUIST(Grant No.KDW1203)
文摘Cloud microphysical properties including liquid and ice particle number concentration （NC）, liquid water content （LWC）, ice water content （IWC） and effective radius （RE） were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear （Pl） and two exponential （P2 and P3） functions, which estimate the liquid-phase fraction as a function of subfreezing temperature （from -20℃ to 0℃）, were tested. The retrieved NC, LWC, IWC and RE using Pl were on average larger than airplane measurements in the same cloud layer, Function P2 performed better than p1 or P3 in retrieving the NCs of cloud droplets in the convective cloud, while function Pl performed better in the stratus cloud. Function P3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the Pl function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function P1.
基金Acknowledgements This work is supported by the National Natural Science Foundation of China （No. 21471114）, the State Major Research Plan （973） of China （No. 2011CB932404） and the Key Laboratory of Tobacco Industry Cigarette Smoke （Shanghai Tobacco Group Co., Ltd. No. 00592）.
文摘A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O3 nanofibers could be fabricated successfully by changing the synthesis parameters. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Raman spectroscopy, and nitrogen adsorption-desorption analyses were used to characterize the structures of the synthesized products. The optimal calcination conditions for preparing α-/γ-FeaO3 nanofibers with the highest ethanol response were determined through ethanol-sensing measurements. The mixed-phase material exhibited a significantly higher sensitivity than the corresponding purephase ones. The superior ethanol-sensing performance of the α-/γ-Fe2O3 nanofibers suggested that they may be suitable for use in alcohol sensing. Hence, a novel strategy for improving the sensing performance of metal oxide semiconductors is to assemble the different crystalline forms of the same metal oxide in one structure. Finally, the mechanism responsible for the sensing performance of α-/γ-Fe2O3 being higher than those of γ-Fe2O3 and α-Fe2O3 was elucidated on the basis of data from X-ray photoelectron spectroscopy and resistance measurements.
基金supported by National Natural Science Foundation of China(Nos.21173028,11505019)the Science and Technology Research Project of Liaoning Provincial Education Department(No.L2013464)+2 种基金the Scientific Research Foundation for the Doctor of Liaoning Province(No.20131004)the Program for Liaoning Excellent Talents in University(No.LR2012042)Dalian Jinzhou New District Science and Technology Plan Project(No.KJCX-ZTPY-2014-0001)
文摘An atmospheric-pressure dielectric barrier discharge （DBD） gas-liquid cold plasma was employed to synthesize Cu-doped TiO~ nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid （IL） and using air as the working gas. The influences of the discharge voltage, IL and the amount of copper nitrite were investigated. X-ray diffraction, N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples. The results showed that the specific surface area of TiO2 was promoted with Cu-doping （from 57.6 m^2.g^-1 to 106.2 m^2.g^-1 with 3% Cu-doping）, and the content of anatase was increased. Besides, the band gap energy of TiO~ with Cu-doping decreased according to the UV-Vis spec- troscopy test. The 3%Cu-IL-TiO2 samples showed the highest eificiency in degrading methylene blue （MB） dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1, which was 1.2 times higher than that of non-doped samples. According to the characterization results, the reasons for the high photocatalytic activity were discussed.
文摘Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of the SAP and soaked conditions on the surface morphology and photocatalytic activity of TiO2 on Ti coatings was investigated. With different SAP conditions,the surface morphologies of the TiO2 on Ti coatings clearly show the formed porous-like structure. With higher SA concentration,the porous-like structure becomes obviously. With extending soaked time,the porous-like structure tends to disappear. Raman spectroscopy reveals that the formed TiO2 coatings are with mixed-phase of anatase and rutile. Compared with those of SA concentration and SAP time,the influence of the soaked time on the phase transformation is obvious. Notably,the photocatalytic activity of TiO2 on Ti coatings had been efficiently enhanced by extending the soaked time,compared with those of higher SA concentration and longer SAP time. The enhanced photocatalytic activity of TiO2 on Ti coatings could be related with the changed surface morphology,mixed-phase of anatase and rutile,and formed hydroxyl groups.
