Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary ...Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.展开更多
It is known that the pore media characteristics of glutenite reservoirs are different from those of conventional sandstone reservoirs.Low reservoir permeability and naturally developed microfractures make water inject...It is known that the pore media characteristics of glutenite reservoirs are different from those of conventional sandstone reservoirs.Low reservoir permeability and naturally developed microfractures make water injection in this kind of reservoir very difficult.In this study,new exploitation methods are explored.Using a real glutenite reservoir as a basis,a three-dimensional fine geological model is elaborated.Then,combining the model with reservoir performance information,and through a historical fitting analysis,the saturation abundance distribution of remaining oil in the reservoir is determined.It is shown that,using this information,predictions can be made about whether the considered reservoir is suitable for horizontal well fracturing or not.The direction,well length,well spacing and productivity of horizontal well are also obtained.展开更多
Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications.In this paper,the energetic electron detection package(EEDP)de...Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications.In this paper,the energetic electron detection package(EEDP)deployed on three Chinese navigation satellites in medium Earth orbit(MEO)is reviewed.The instrument was developed by the space science payload team led by Peking University.The EEDP includes a pinhole medium-energy electron spectrometer(MES),a high-energy electron detector(HED)based onΔE-E telescope technology,and a deep dielectric charging monitor(DDCM).The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30°field of view(FOV).The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30°cone-angle FOV.The ground test and calibration results indicate that these three sensors exhibit excellent performance.Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer(MagEIS)of the Van Allen Probes spacecraft,with an average relative deviation of 27.3%for the energy spectra.The charging currents and voltages measured by the DDCM during storms are consistent with the highenergy electron observations of the HED,demonstrating the effectiveness of the DDCM.The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.展开更多
Resveratrol, a naturally derived stilbene that exists in various foods and beverages, has attracted extensive exploration due to its multiple biological activities, such as anticancer, antioxidant, cardiovascular prot...Resveratrol, a naturally derived stilbene that exists in various foods and beverages, has attracted extensive exploration due to its multiple biological activities, such as anticancer, antioxidant, cardiovascular protection, anti-inflammatory, antiviral, chemopreventive effect, neuroprotective effect, immunomodulation and so on. However, owing to its poor oral bioavailability, the application of resveratrol is greatly restricted. Because of that, a large amount of efforts had been made by researchers on designing its derivatives to obtain compounds with improved efficiency and low toxicity for developing more active drugs for clinical application. In this report, we review the current development of studying on resveratrol derivatives including their properties and activities. Additionally, this article also presents the synthetic routes of correlative resveratrol derivatives.展开更多
Within any scientific disciplines, a large amount of data are buried within various literature depositories and archives, making it difficult to manually extract useful information from the datum swamps. The machine-l...Within any scientific disciplines, a large amount of data are buried within various literature depositories and archives, making it difficult to manually extract useful information from the datum swamps. The machine-learning extraction of data therefore is necessary for the big-data-based studies. Here, we develop a new text-mining technique to reconstruct the global database of the Precambrian to Recent stromatolites, providing better understanding of secular changes of stromatolites though geological time. The step-by-step data extraction process is described as below. First, the PDF documents of stromatolite-containing literatures were collected, and converted into text formation. Second, a glossary and tag-labeling system using NLP(Natural Language Processing) software was employed to search for all possible candidate pairs from each sentence within the papers collected here. Third, each candidate pair and features were represented as a factor graph model using a series of heuristic procedures to score the weights of each pair feature. Occurrence data of stromatolites versus stratigraphical units(abbreviated as Strata), facies types, locations, and age worldwide were extracted from literatures, respectively, and their extraction accuracies are 92%/464, 87%/778, 92%/846, and 93%/405 from 3 750 scientific abstracts, respectively, and are 90%/1 734, 86%/2 869, 90%/2 055 and 91%/857 from 11 932 papers, respectively. A total of 10 072 unique datum items were identified. The newly obtained stromatolite dataset demonstrates that their stratigraphical occurrences reached a pronounced peak during the Proterozoic(2 500 – 541 Ma), followed by a distinct fall during the Early Phanerozoic, and overall fluctuations through the Phanerozoic(541–0 Ma). Globally, seven stromatolite hotspots were identified from the new dataset, including western United States, eastern United States, western Europe, India, South Africa, northern China, and southern China. The proportional occurrences of inland aquatic stromatolites remain rather low(~20%) in comparison to marine stromatolites from the Precambrian to Jurassic, and then display a significant increase(30%–70%) from the Cretaceous to the present.展开更多
Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this pap...Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this paper,preneutron fragment mass yields at incident energies from thermal up to 20 MeV are systematically studied using an empirical fission potential(EFP)model,the potential parameters of which are obtained from the measured data.The energy dependences of the peaks and valleys of the pre-neutron fragment mass yields are described by exponential and linear functions for the^(235)U(n,f)and^(239)Pu(n,f)reactions,respectively.The energy dependences of the evaporation neutrons,which play a crucial role in the reasonable description of pre-neutron fragment mass yields,are also obtained from the fission cross sections.The pre-neutron fragment mass yields in this study are not only consistent with the results of previous studies in regions of several Me Vs but also agree well with existing measured data at incident energies from thermal up to 20 MeV.The results show that the feasibility of this EFP model is verified in this extended energy region.展开更多
Thermal barrier coating(TBC) materials play important roles in gas turbine engines to protect the Nibased super-alloys from the high temperature airflow damage. High melting point, ultra-low thermal conductivity, larg...Thermal barrier coating(TBC) materials play important roles in gas turbine engines to protect the Nibased super-alloys from the high temperature airflow damage. High melting point, ultra-low thermal conductivity, large thermal expansion coefficient, excellent damage tolerance and moderate mechanical properties are the main requirements of promising TBC materials. In order to improve the efficiency of jet and/or gas turbine engines, which is the key of improved thrust-to-weight ratios and the energysaving, significant efforts have been made on searching for enhanced TBC materials. Theoretically, density functional theory has been successfully used in scanning the structure and properties of materials, and at the same time predicting the mechanical and thermal properties of promising TBC materials for high and ultrahigh temperature applications, which are validated by subsequent experiments. Experimentally,doping and/or alloying are also widely applied to further decrease their thermal conductivities. Now, the strategy through combining theoretical calculations and experiments on searching for next generation thermal insulator materials is widely adopted. In this review, the common used techniques and the recent advantages on searching for promising TBC materials in both theory and experiments are summarized.展开更多
Gadolinium zirconate (GZ) is a promising candidate for next-generation thermal barrier coating (TBC) materials.Its corrosion resistance against calcium-magnesium-alumino-silicate(CMAS) needs to be further increased fo...Gadolinium zirconate (GZ) is a promising candidate for next-generation thermal barrier coating (TBC) materials.Its corrosion resistance against calcium-magnesium-alumino-silicate(CMAS) needs to be further increased for enhancing its in-service life.As the Gd element plays an important role in the CMAS resistance,three GZ coatings (GZ-0.75,GZ-1.0,and GZ-1.2) with different Gd/Zr atomic ratios are designed and deposited by laser enhanced chemical vapor deposition(LCVD) in this work.It is found that the generated Gd-apatite in GZ-1.2 would block micro-cracks inside the column structure and the inter-columnar gap more efficiently.Thus,the CMAS penetration rate (5.2 μm/h) of GZ-1.2 decreases over 27% comparing with GZ-1.0 and GZ-0.75,which is even lower than the Gd_(2)Zr_(2)O_(7) coatings fabricated by electron-beam physical vapor depositions (EB-PVDs).This work provides a feasible way to adjust the coating's corrosion resistance and may guide the development of future coating for long in-service life.展开更多
Tungsten bronze coatings and films have attracted global attention for their applications in near-infrared(NIR)-shielding windows.However,they are unstable in strong ultraviolet,humid heat,alkaline and/or oxidizing en...Tungsten bronze coatings and films have attracted global attention for their applications in near-infrared(NIR)-shielding windows.However,they are unstable in strong ultraviolet,humid heat,alkaline and/or oxidizing environments and are difficult to be coated on glass surfaces with complex shape.Here,we address these limitations by doping sodium tungsten bronze(Na_(x)WO_(3))into bulk glasses using a simple glass melting method.X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,TEM and SEM-EDS characterization confirmed the presence of sodium tungsten bronze(Na_(x)WO_(3))functional units inside the 34SiO_(2)-38B_(2)O_(3)-28NaF glass matrix.Because the functional units are well protected by the glass matrix,the fabricated glasses are stable under hot,humid,oxidizing conditions,as well as under ambient conditions,with no change after 360 days.The NIR-shielding performance of these glasses can be adjusted to as high as 100%by varying WO_(x)concentration(2-8 mol%)and quenching temperature(1000-1400℃).With a content of 6 mol%WO_(x)and a quenching temperature of 1000℃,the bulk glass shows 63%transmission of visible light and only 11%transmission of NIR light at 1100 nm.Thermal insulation experiments show that the NIR-shielding performance of the glasses are far superior to commercial soda lime window glass or indium-doped tin oxide(ITO)glass,and comparable to cesium tungsten bronze coated glass.The novel bulk glasses have higher stability,simpler processing,and can be easily made into complex shapes,making them excellent alternative materials for energy-saving glasses.展开更多
Various excellent properties of rare earth zirconate and stannate pyrochlores are close related with their native point defects.First-principles calculations are performed to systematically investigate the point defec...Various excellent properties of rare earth zirconate and stannate pyrochlores are close related with their native point defects.First-principles calculations are performed to systematically investigate the point defect mechanism and the oxygen diffusion behavior of A_(2)B_(2)O_(7)(A=La,Ce,Pr,Nd,Pm,Sm,Eu,Gd;B=Zr,Sn).The possible defect complexes and their associated reactions under stoichiometric and nonstoichiometric conditions are explored.The O Frenkel pairs are the most stable defect structure in stoichiometric zirconates,whereas the cation antisite defects are the predominant one in stoichiometric stannates.In the case of BO_(2) excess zirconates and stannates,the BA cation antisite defect with the A vacancy and/or the oxygen interstitial is energetically favorable,whereas the ABantisite defect together with the oxygen vacancy and/or the A interstitial is preferable under the A_(2)O_(3) excess condition.Meanwhile,the maximum point defect concentrations of zirconates are much higher than those of stannates.Furthermore,the oxygen migration barriers are similar in these compounds,ranging in 0.68 eV–0.80 eV.The predicted point defects and oxygen diffusion mechanisms play the critical role in their engineering applications and are expected to guide the future property improvement of pyrochlores through the control of point defects and/or composition.展开更多
基金supported by the National Nature Science Foundation of China,the National Key Research and Development Program of China(302001109,2016YFD0300508,2017YFD0301602,2018YFD0301105)the Fujian and Taiwan Cultivation Resources Development and Green Cultivation Coordination Innovation Center,China(Fujian 2011 Project,2015-75)the Natural Science Foundation of Fujian Province,China(2022J01142)。
文摘Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.
文摘It is known that the pore media characteristics of glutenite reservoirs are different from those of conventional sandstone reservoirs.Low reservoir permeability and naturally developed microfractures make water injection in this kind of reservoir very difficult.In this study,new exploitation methods are explored.Using a real glutenite reservoir as a basis,a three-dimensional fine geological model is elaborated.Then,combining the model with reservoir performance information,and through a historical fitting analysis,the saturation abundance distribution of remaining oil in the reservoir is determined.It is shown that,using this information,predictions can be made about whether the considered reservoir is suitable for horizontal well fracturing or not.The direction,well length,well spacing and productivity of horizontal well are also obtained.
基金supported by the National Natural Science Foundation of China(No.41374167,41421003,41474140)China's National Basic Research and Development Program(No.2012CB825603).
文摘Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications.In this paper,the energetic electron detection package(EEDP)deployed on three Chinese navigation satellites in medium Earth orbit(MEO)is reviewed.The instrument was developed by the space science payload team led by Peking University.The EEDP includes a pinhole medium-energy electron spectrometer(MES),a high-energy electron detector(HED)based onΔE-E telescope technology,and a deep dielectric charging monitor(DDCM).The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30°field of view(FOV).The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30°cone-angle FOV.The ground test and calibration results indicate that these three sensors exhibit excellent performance.Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer(MagEIS)of the Van Allen Probes spacecraft,with an average relative deviation of 27.3%for the energy spectra.The charging currents and voltages measured by the DDCM during storms are consistent with the highenergy electron observations of the HED,demonstrating the effectiveness of the DDCM.The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.
文摘Resveratrol, a naturally derived stilbene that exists in various foods and beverages, has attracted extensive exploration due to its multiple biological activities, such as anticancer, antioxidant, cardiovascular protection, anti-inflammatory, antiviral, chemopreventive effect, neuroprotective effect, immunomodulation and so on. However, owing to its poor oral bioavailability, the application of resveratrol is greatly restricted. Because of that, a large amount of efforts had been made by researchers on designing its derivatives to obtain compounds with improved efficiency and low toxicity for developing more active drugs for clinical application. In this report, we review the current development of studying on resveratrol derivatives including their properties and activities. Additionally, this article also presents the synthetic routes of correlative resveratrol derivatives.
基金supported by three grants from the National Natural Science Foundation of China (Nos.41821001,41902315,41930322)。
文摘Within any scientific disciplines, a large amount of data are buried within various literature depositories and archives, making it difficult to manually extract useful information from the datum swamps. The machine-learning extraction of data therefore is necessary for the big-data-based studies. Here, we develop a new text-mining technique to reconstruct the global database of the Precambrian to Recent stromatolites, providing better understanding of secular changes of stromatolites though geological time. The step-by-step data extraction process is described as below. First, the PDF documents of stromatolite-containing literatures were collected, and converted into text formation. Second, a glossary and tag-labeling system using NLP(Natural Language Processing) software was employed to search for all possible candidate pairs from each sentence within the papers collected here. Third, each candidate pair and features were represented as a factor graph model using a series of heuristic procedures to score the weights of each pair feature. Occurrence data of stromatolites versus stratigraphical units(abbreviated as Strata), facies types, locations, and age worldwide were extracted from literatures, respectively, and their extraction accuracies are 92%/464, 87%/778, 92%/846, and 93%/405 from 3 750 scientific abstracts, respectively, and are 90%/1 734, 86%/2 869, 90%/2 055 and 91%/857 from 11 932 papers, respectively. A total of 10 072 unique datum items were identified. The newly obtained stromatolite dataset demonstrates that their stratigraphical occurrences reached a pronounced peak during the Proterozoic(2 500 – 541 Ma), followed by a distinct fall during the Early Phanerozoic, and overall fluctuations through the Phanerozoic(541–0 Ma). Globally, seven stromatolite hotspots were identified from the new dataset, including western United States, eastern United States, western Europe, India, South Africa, northern China, and southern China. The proportional occurrences of inland aquatic stromatolites remain rather low(~20%) in comparison to marine stromatolites from the Precambrian to Jurassic, and then display a significant increase(30%–70%) from the Cretaceous to the present.
基金Supported by the National Natural Science Foundation of China(12065003)the Natural Science Foundation of Guangxi(2019GXNSFDA185011)+2 种基金the Key Laboratory of Neutron Physics China Academy of Engineering Physics(2018BA03)the Scientific Research and Technology Development Project of Guilin(20210104-2)the Central Government Guides Local Scientic and Technological Development Funds of China(Guike ZY22096024)。
文摘Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this paper,preneutron fragment mass yields at incident energies from thermal up to 20 MeV are systematically studied using an empirical fission potential(EFP)model,the potential parameters of which are obtained from the measured data.The energy dependences of the peaks and valleys of the pre-neutron fragment mass yields are described by exponential and linear functions for the^(235)U(n,f)and^(239)Pu(n,f)reactions,respectively.The energy dependences of the evaporation neutrons,which play a crucial role in the reasonable description of pre-neutron fragment mass yields,are also obtained from the fission cross sections.The pre-neutron fragment mass yields in this study are not only consistent with the results of previous studies in regions of several Me Vs but also agree well with existing measured data at incident energies from thermal up to 20 MeV.The results show that the feasibility of this EFP model is verified in this extended energy region.
基金supported by the National Natural Science Foundation of China (No. 51602188)the Program for Professor of Special Appointment (Eastern Scholar)by Shanghai Municipal Education Commission (No. TP2015040)
文摘Thermal barrier coating(TBC) materials play important roles in gas turbine engines to protect the Nibased super-alloys from the high temperature airflow damage. High melting point, ultra-low thermal conductivity, large thermal expansion coefficient, excellent damage tolerance and moderate mechanical properties are the main requirements of promising TBC materials. In order to improve the efficiency of jet and/or gas turbine engines, which is the key of improved thrust-to-weight ratios and the energysaving, significant efforts have been made on searching for enhanced TBC materials. Theoretically, density functional theory has been successfully used in scanning the structure and properties of materials, and at the same time predicting the mechanical and thermal properties of promising TBC materials for high and ultrahigh temperature applications, which are validated by subsequent experiments. Experimentally,doping and/or alloying are also widely applied to further decrease their thermal conductivities. Now, the strategy through combining theoretical calculations and experiments on searching for next generation thermal insulator materials is widely adopted. In this review, the common used techniques and the recent advantages on searching for promising TBC materials in both theory and experiments are summarized.
基金This work was supported by the Natural Science Foundation of Shanghai(No.20ZR1419200)National Natural Science Foundation of China(Nos.52072232 and 52072231)the Program for Professor of Special Appointment(Eastern Scholar)by Shanghai Municipal Education Commission(No.TP2015040).
文摘Gadolinium zirconate (GZ) is a promising candidate for next-generation thermal barrier coating (TBC) materials.Its corrosion resistance against calcium-magnesium-alumino-silicate(CMAS) needs to be further increased for enhancing its in-service life.As the Gd element plays an important role in the CMAS resistance,three GZ coatings (GZ-0.75,GZ-1.0,and GZ-1.2) with different Gd/Zr atomic ratios are designed and deposited by laser enhanced chemical vapor deposition(LCVD) in this work.It is found that the generated Gd-apatite in GZ-1.2 would block micro-cracks inside the column structure and the inter-columnar gap more efficiently.Thus,the CMAS penetration rate (5.2 μm/h) of GZ-1.2 decreases over 27% comparing with GZ-1.0 and GZ-0.75,which is even lower than the Gd_(2)Zr_(2)O_(7) coatings fabricated by electron-beam physical vapor depositions (EB-PVDs).This work provides a feasible way to adjust the coating's corrosion resistance and may guide the development of future coating for long in-service life.
基金supported by the National Natural Science Foundation of China(Nos.52072231,51602187,52072232,51702208)the program for the Young Eastern Scholars Program(No.QD2015028)+1 种基金the Shanghai Municipal Science and Technology Commission(No.18JC1412800)Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-09-E00020)from Shanghai Municipal Education Commission(China)。
文摘Tungsten bronze coatings and films have attracted global attention for their applications in near-infrared(NIR)-shielding windows.However,they are unstable in strong ultraviolet,humid heat,alkaline and/or oxidizing environments and are difficult to be coated on glass surfaces with complex shape.Here,we address these limitations by doping sodium tungsten bronze(Na_(x)WO_(3))into bulk glasses using a simple glass melting method.X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,TEM and SEM-EDS characterization confirmed the presence of sodium tungsten bronze(Na_(x)WO_(3))functional units inside the 34SiO_(2)-38B_(2)O_(3)-28NaF glass matrix.Because the functional units are well protected by the glass matrix,the fabricated glasses are stable under hot,humid,oxidizing conditions,as well as under ambient conditions,with no change after 360 days.The NIR-shielding performance of these glasses can be adjusted to as high as 100%by varying WO_(x)concentration(2-8 mol%)and quenching temperature(1000-1400℃).With a content of 6 mol%WO_(x)and a quenching temperature of 1000℃,the bulk glass shows 63%transmission of visible light and only 11%transmission of NIR light at 1100 nm.Thermal insulation experiments show that the NIR-shielding performance of the glasses are far superior to commercial soda lime window glass or indium-doped tin oxide(ITO)glass,and comparable to cesium tungsten bronze coated glass.The novel bulk glasses have higher stability,simpler processing,and can be easily made into complex shapes,making them excellent alternative materials for energy-saving glasses.
基金supported by the National Natural Science Foundation of China(No.51602188)the Program for Professor of Special Appointment(Eastern Scholar)by Shanghai Municipal Education Commission(No.TP2015040)。
文摘Various excellent properties of rare earth zirconate and stannate pyrochlores are close related with their native point defects.First-principles calculations are performed to systematically investigate the point defect mechanism and the oxygen diffusion behavior of A_(2)B_(2)O_(7)(A=La,Ce,Pr,Nd,Pm,Sm,Eu,Gd;B=Zr,Sn).The possible defect complexes and their associated reactions under stoichiometric and nonstoichiometric conditions are explored.The O Frenkel pairs are the most stable defect structure in stoichiometric zirconates,whereas the cation antisite defects are the predominant one in stoichiometric stannates.In the case of BO_(2) excess zirconates and stannates,the BA cation antisite defect with the A vacancy and/or the oxygen interstitial is energetically favorable,whereas the ABantisite defect together with the oxygen vacancy and/or the A interstitial is preferable under the A_(2)O_(3) excess condition.Meanwhile,the maximum point defect concentrations of zirconates are much higher than those of stannates.Furthermore,the oxygen migration barriers are similar in these compounds,ranging in 0.68 eV–0.80 eV.The predicted point defects and oxygen diffusion mechanisms play the critical role in their engineering applications and are expected to guide the future property improvement of pyrochlores through the control of point defects and/or composition.
