Impedance matching is important for achieving high-efficiency microwave absorbers. The high conductivity of dielectric loss materials such as pure metals and carbon nanomaterials generally results in poor absorption o...Impedance matching is important for achieving high-efficiency microwave absorbers. The high conductivity of dielectric loss materials such as pure metals and carbon nanomaterials generally results in poor absorption owing to the low impedance matching between the absorbers and air. Carbon nanostructures are very promising candidates for high-efficiency absorption because of their attractive features including low density, high surface area, and good stability. Herein, a new strategy is proposed to improve the impedance matching of dielectric loss materials using electrospun carbon nanofibers as an example. The carbon nanofibers are coated with specifically designed gradient multilayer nanofilms with gradually increasing electroconductibility synthesized by doping ZnO with different A1203 content （AZO） by atomic layer deposition. The gradient nanofilms are composed of five layers of dielectric films, namely, pure A1203, AZO （5：1, the pulse cycle ratio of ZnO to A1203）, pure ZnO, AZO （10：1）, and AZO （20：1）. The versatile gradient films serve as intermediate layers to tune the impedance matching between air and the carbon nanofiber surfaces. Therefore, the carbon nanofibers coated with gradient films of rationally selected thicknesses exhibit remarkably enhanced microwave absorption performance, and the optimal reflection loss reaches -58.5 dB at 16.2 GHz with a thickness of only 1.8 mm. This work can help further understand the contribution of impedance matching to microwave absorption. Our strategy is general and can be applied to improve the absorption properties of other dielectric loss materials and even for applications in other fields.展开更多
Although Sn-based catalysts have recently achieved considerable improvement in selective electro-catalyzing CO_(2)into HCOOH,the role of various valence Sn species is not fully understood due to the complexity and unc...Although Sn-based catalysts have recently achieved considerable improvement in selective electro-catalyzing CO_(2)into HCOOH,the role of various valence Sn species is not fully understood due to the complexity and uncertainty of their evolution during the reaction process.Here,inspired by the theoretical simulations that the concomitant multivalent Sn(Sn^(0),Sn^(Ⅱ)and Sn^(Ⅳ))can significantly motivate the intrinsic activity of Sn-based catalyst,the Sn/SnO/SnO_(2)nanosheets were proposed to experimentally verify the synergistic effect of multivalent Sn species on the CO_(2)-into-HCOOH conversion.During CO_(2)reduction reaction,the Sn/SnO/SnO_(2)nanosheets,which are prepared by the sequential hydrothermal reaction,calcined crystallization and low-temperature H_(2)treatment,exhibit a high FEHCOOH of 89.6%at-0.9 VRHE as well as a large cathodic current density.Systematic experimental and theoretical results corroborate that multivalent Sn species synergistically energize the CO_(2)activation,the HCOO*adsorption,and the electron transfer,which make Sn/SnO/SnO_(2)favour the conversion from CO_(2)into HCOOH in both thermodynamics and kinetics.This proof-of-concept study establishes a relationship between the enhanced performance and the multivalent Sn species,and also provides a practicable and scalable avenue for rational engineering high-powered electrocatalysts.展开更多
Plant growth rhythm in structural traits is important for better understanding plant response to the ever-changing environment.Terrestrial laser scanning(TLS)is a well-suited tool to study structural rhythm under fiel...Plant growth rhythm in structural traits is important for better understanding plant response to the ever-changing environment.Terrestrial laser scanning(TLS)is a well-suited tool to study structural rhythm under field conditions.Recent studies have used TLS to describe the structural rhythm of trees,but no consistent patterns have been drawn.Meanwhile,whether TLS can capture structural rhythm in crops is unclear.Here,we aim to explore the seasonal and circadian rhythms in maize structural traits at both the plant and leaf levels from time-series TLS.The seasonal rhythm was studied using TLS data collected at four key growth periods,including jointing,bell-mouthed,heading,and maturity periods.Circadian rhythms were explored by using TLS data acquired around every 2 hours in a whole day under standard and cold stress conditions.Results showed that TLS can quantify the seasonal and circadian rhythm in structural traits at both plant and leaf levels.(1)Leaf inclination angle decreased significantly between the jointing stage and bell-mouthed stage.Leaf azimuth was stable after the jointing stage.(2)Some individual-level structural rhythms(e.g.,azimuth and projected leaf area/PLA)were consistent with leaf-level structural rhythms.(3)The circadian rhythms of some traits(e.g.,PLA)were not consistent under standard and cold stress conditions.(4)Environmental factors showed better correlations with leaf traits under cold stress than standard conditions.Temperature was the most important factor that significantly correlated with all leaf traits except leaf azimuth.This study highlights the potential of time-series TLS in studying outdoor agricultural chronobiology.展开更多
Wheat yield and grain protein content(GPC)are two main optimization targets for breeding and cultivation.Remote sensing provides nondestructive and early predictions of yield and GPC,respectively.However,whether it is...Wheat yield and grain protein content(GPC)are two main optimization targets for breeding and cultivation.Remote sensing provides nondestructive and early predictions of yield and GPC,respectively.However,whether it is possible to simultaneously predict yield and GPC in one model and the accuracy and influencing factors are still unclear.In this study,we made a systematic comparison of different deep learning models in terms of data fusion,time-series feature extraction,and multitask learning.The results showed that time-series data fusion significantly improved yield and GPC prediction accuracy with R 2 values of 0.817 and 0.809.展开更多
Metamaterials have demonstrated exotic electromagnetic properties, which offer a good platform for realizing light absorption, photodetection, filtering, and so on. However, broadband multifunctional metamaterial abso...Metamaterials have demonstrated exotic electromagnetic properties, which offer a good platform for realizing light absorption, photodetection, filtering, and so on. However, broadband multifunctional metamaterial absorbers are restricted in cascaded structures. Here, broadband multifunctional properties were realized by introducing vanadium dioxide into a metamaterial absorber. Through the modified design and highly efficient utilization of multiple resonant modes, both plasmonic tunable color filters and near-infrared photodetectors can be simultaneously achieved by this construction. Meanwhile, active color and a photodetection band in the near-infrared range can become tunable with the insulating-metallic transition of vanadium dioxide. Thus, the variations of rendering colors could correspondingly indicate shifts of the near-infrared photodetection bands. This method theoretically confirms the feasibility of designing multifunctional devices via a terial absorber, which holds great promise for future versatile utilization of vanadium-dioxide-based metamamultiple physical mechanisms to achieve numerous functionalities in a simple nanostructure or device.展开更多
Titanium nitride(TiN) as a refractory plasmonic material is proposed to be used as an angle-insensitive integrated broadband solar absorber and narrowband near-infrared(NIR) emitter for solar thermo-photovoltaic(STPV)...Titanium nitride(TiN) as a refractory plasmonic material is proposed to be used as an angle-insensitive integrated broadband solar absorber and narrowband near-infrared(NIR) emitter for solar thermo-photovoltaic(STPV) application. By constructing TiN-nanopatterns/dielectric/TiN stack metamaterial, approximately 93% light absorption in a wavelength range of 0.3–0.9 μm and near unit narrowband(Δλ∕λ～0.3) emission in NIR(～2 μm) were demonstrated by numerical simulation. Keeping the excellent light absorption in the visible band, the emission wavelength can be easily tuned by patterning the top TiN layer into various subwavelength structures. This dual function attributes to the intrinsic absorption and plasmonic property of TiN. In such an integrated structure,broadband absorption and narrowband emission need to be balanced for an optimized power efficiency conversion. Detailed analysis has demonstrated that the STPV system based on this integrated absorber/emitter canexceed the Shockley–Queisser limit at 1000 K.展开更多
Efficient and high-quality estimation of key phenological dates in rice is of great significance in breeding work. Plant height(PH) dynamics are valuable for estimating phenological dates. However, research on estimat...Efficient and high-quality estimation of key phenological dates in rice is of great significance in breeding work. Plant height(PH) dynamics are valuable for estimating phenological dates. However, research on estimating the key phenological dates of multiple rice accessions based on PH dynamics has been limited. In 2022, field traits were collected using unmanned aerial vehicle(UAV)-based images across 435 plots, including 364 rice varieties. PH, dates of initial heading(IH) and full heading(FH), and panicle initiation(PI), and growth period after transplanting(GPAT) were collected during the rice growth stage. PHs were extracted using a digital surface model(DSM) and fitted using Fourier and logistic models. Machine learning algorithms, including multiple linear regression, random forest(RF), support vector regression, least absolute shrinkage and selection operator, and elastic net regression, were employed to estimate phenological dates. Results indicated that the optimal percentile of the DSM for extracting rice PH was the 95th(R^(2) = 0.934, RMSE = 0.056 m). The Fourier model provided a better fit for PH dynamics compared with the logistic models. Additionally, curve features(CF) and GPAT were significantly associated with PI, IH, and FH. The combination of CF and GPAT outperformed the use of CF alone, with RF demonstrating the best performance among the algorithms. Specifically, the combination of CF extracted from the logistic models, GPAT, and RF yielded the best performance for estimating PI(R^(2) = 0.834, RMSE = 4.344 d), IH(R^(2) = 0.877, RMSE = 2.721 d), and FH(R^(2) = 0.883, RMSE = 2.694 d). Overall, UAV-based rice PH dynamics combined with machine learning effectively estimated the key phenological dates of multiple rice accessions, providing a novel approach for investigating key phenological dates in breeding work.展开更多
文摘Impedance matching is important for achieving high-efficiency microwave absorbers. The high conductivity of dielectric loss materials such as pure metals and carbon nanomaterials generally results in poor absorption owing to the low impedance matching between the absorbers and air. Carbon nanostructures are very promising candidates for high-efficiency absorption because of their attractive features including low density, high surface area, and good stability. Herein, a new strategy is proposed to improve the impedance matching of dielectric loss materials using electrospun carbon nanofibers as an example. The carbon nanofibers are coated with specifically designed gradient multilayer nanofilms with gradually increasing electroconductibility synthesized by doping ZnO with different A1203 content （AZO） by atomic layer deposition. The gradient nanofilms are composed of five layers of dielectric films, namely, pure A1203, AZO （5：1, the pulse cycle ratio of ZnO to A1203）, pure ZnO, AZO （10：1）, and AZO （20：1）. The versatile gradient films serve as intermediate layers to tune the impedance matching between air and the carbon nanofiber surfaces. Therefore, the carbon nanofibers coated with gradient films of rationally selected thicknesses exhibit remarkably enhanced microwave absorption performance, and the optimal reflection loss reaches -58.5 dB at 16.2 GHz with a thickness of only 1.8 mm. This work can help further understand the contribution of impedance matching to microwave absorption. Our strategy is general and can be applied to improve the absorption properties of other dielectric loss materials and even for applications in other fields.
基金the National Natural Science Foundation of China(Nos.21631004,21901065)the Natural Science Foundation of Heilongjiang Province of China(No.LH2020B019)+1 种基金the Youth Science and Technology Innovation Team Project of Heilongjiang Province(No.RCYJTD201803)the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2018009).
文摘Although Sn-based catalysts have recently achieved considerable improvement in selective electro-catalyzing CO_(2)into HCOOH,the role of various valence Sn species is not fully understood due to the complexity and uncertainty of their evolution during the reaction process.Here,inspired by the theoretical simulations that the concomitant multivalent Sn(Sn^(0),Sn^(Ⅱ)and Sn^(Ⅳ))can significantly motivate the intrinsic activity of Sn-based catalyst,the Sn/SnO/SnO_(2)nanosheets were proposed to experimentally verify the synergistic effect of multivalent Sn species on the CO_(2)-into-HCOOH conversion.During CO_(2)reduction reaction,the Sn/SnO/SnO_(2)nanosheets,which are prepared by the sequential hydrothermal reaction,calcined crystallization and low-temperature H_(2)treatment,exhibit a high FEHCOOH of 89.6%at-0.9 VRHE as well as a large cathodic current density.Systematic experimental and theoretical results corroborate that multivalent Sn species synergistically energize the CO_(2)activation,the HCOO*adsorption,and the electron transfer,which make Sn/SnO/SnO_(2)favour the conversion from CO_(2)into HCOOH in both thermodynamics and kinetics.This proof-of-concept study establishes a relationship between the enhanced performance and the multivalent Sn species,and also provides a practicable and scalable avenue for rational engineering high-powered electrocatalysts.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA24020202)Plant Phenomics Research Program of Science and Technology Department of Jiangsu Province(No.BM2018001)Beijing Municipal Science and Technology Project(Z191100007419004).
文摘Plant growth rhythm in structural traits is important for better understanding plant response to the ever-changing environment.Terrestrial laser scanning(TLS)is a well-suited tool to study structural rhythm under field conditions.Recent studies have used TLS to describe the structural rhythm of trees,but no consistent patterns have been drawn.Meanwhile,whether TLS can capture structural rhythm in crops is unclear.Here,we aim to explore the seasonal and circadian rhythms in maize structural traits at both the plant and leaf levels from time-series TLS.The seasonal rhythm was studied using TLS data collected at four key growth periods,including jointing,bell-mouthed,heading,and maturity periods.Circadian rhythms were explored by using TLS data acquired around every 2 hours in a whole day under standard and cold stress conditions.Results showed that TLS can quantify the seasonal and circadian rhythm in structural traits at both plant and leaf levels.(1)Leaf inclination angle decreased significantly between the jointing stage and bell-mouthed stage.Leaf azimuth was stable after the jointing stage.(2)Some individual-level structural rhythms(e.g.,azimuth and projected leaf area/PLA)were consistent with leaf-level structural rhythms.(3)The circadian rhythms of some traits(e.g.,PLA)were not consistent under standard and cold stress conditions.(4)Environmental factors showed better correlations with leaf traits under cold stress than standard conditions.Temperature was the most important factor that significantly correlated with all leaf traits except leaf azimuth.This study highlights the potential of time-series TLS in studying outdoor agricultural chronobiology.
基金This study was supported by the Jiangsu Agricultural Science and Technol-ogy Independent Innovation Fund Project(No.CX(21)3107)National Natural Science Foundation of China(32030076)+3 种基金China Postdoctoral Science Foundation(No.2021M691490)Jiangsu Planned Projects for Postdoctoral Research Funds(No.2021K520C)High Level Personnel Project of Jiangsu Province(JSSCBS20210271)Collabo-rative Innovation Center for Modern Crop Production cosponsored by the Province and Ministry(CIC-MCP).
文摘Wheat yield and grain protein content(GPC)are two main optimization targets for breeding and cultivation.Remote sensing provides nondestructive and early predictions of yield and GPC,respectively.However,whether it is possible to simultaneously predict yield and GPC in one model and the accuracy and influencing factors are still unclear.In this study,we made a systematic comparison of different deep learning models in terms of data fusion,time-series feature extraction,and multitask learning.The results showed that time-series data fusion significantly improved yield and GPC prediction accuracy with R 2 values of 0.817 and 0.809.
基金973 Program of China(2013CBA01700)National Natural Science Foundation of China(NSFC)(61622509,61675208)
文摘Metamaterials have demonstrated exotic electromagnetic properties, which offer a good platform for realizing light absorption, photodetection, filtering, and so on. However, broadband multifunctional metamaterial absorbers are restricted in cascaded structures. Here, broadband multifunctional properties were realized by introducing vanadium dioxide into a metamaterial absorber. Through the modified design and highly efficient utilization of multiple resonant modes, both plasmonic tunable color filters and near-infrared photodetectors can be simultaneously achieved by this construction. Meanwhile, active color and a photodetection band in the near-infrared range can become tunable with the insulating-metallic transition of vanadium dioxide. Thus, the variations of rendering colors could correspondingly indicate shifts of the near-infrared photodetection bands. This method theoretically confirms the feasibility of designing multifunctional devices via a terial absorber, which holds great promise for future versatile utilization of vanadium-dioxide-based metamamultiple physical mechanisms to achieve numerous functionalities in a simple nanostructure or device.
基金supported by grants from the National Natural Science Foundation of China (Nos. 11274344 and 61574158)the Suzhou Science and Technology Development Program Foundation (No. ZXG201425)the general financial grant from the China Postdoctoral Science Foundation (No. 2014M560457)
文摘Titanium nitride(TiN) as a refractory plasmonic material is proposed to be used as an angle-insensitive integrated broadband solar absorber and narrowband near-infrared(NIR) emitter for solar thermo-photovoltaic(STPV) application. By constructing TiN-nanopatterns/dielectric/TiN stack metamaterial, approximately 93% light absorption in a wavelength range of 0.3–0.9 μm and near unit narrowband(Δλ∕λ～0.3) emission in NIR(～2 μm) were demonstrated by numerical simulation. Keeping the excellent light absorption in the visible band, the emission wavelength can be easily tuned by patterning the top TiN layer into various subwavelength structures. This dual function attributes to the intrinsic absorption and plasmonic property of TiN. In such an integrated structure,broadband absorption and narrowband emission need to be balanced for an optimized power efficiency conversion. Detailed analysis has demonstrated that the STPV system based on this integrated absorber/emitter canexceed the Shockley–Queisser limit at 1000 K.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFD2300700)the Open Project Program of the State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute (Grant No.2023ZZKT20402)+1 种基金the Agricultural Science and Technology Innovation Program, the Central Public-Interest Scientific Institution Basal Research Fund, China (Grant No.CPSIBRF-CNRRI-202119)the Zhejiang ‘Ten Thousand Talents’ Plan Science and Technology Innovation Leading Talent Project, China (Grant No.2020R52035)。
文摘Efficient and high-quality estimation of key phenological dates in rice is of great significance in breeding work. Plant height(PH) dynamics are valuable for estimating phenological dates. However, research on estimating the key phenological dates of multiple rice accessions based on PH dynamics has been limited. In 2022, field traits were collected using unmanned aerial vehicle(UAV)-based images across 435 plots, including 364 rice varieties. PH, dates of initial heading(IH) and full heading(FH), and panicle initiation(PI), and growth period after transplanting(GPAT) were collected during the rice growth stage. PHs were extracted using a digital surface model(DSM) and fitted using Fourier and logistic models. Machine learning algorithms, including multiple linear regression, random forest(RF), support vector regression, least absolute shrinkage and selection operator, and elastic net regression, were employed to estimate phenological dates. Results indicated that the optimal percentile of the DSM for extracting rice PH was the 95th(R^(2) = 0.934, RMSE = 0.056 m). The Fourier model provided a better fit for PH dynamics compared with the logistic models. Additionally, curve features(CF) and GPAT were significantly associated with PI, IH, and FH. The combination of CF and GPAT outperformed the use of CF alone, with RF demonstrating the best performance among the algorithms. Specifically, the combination of CF extracted from the logistic models, GPAT, and RF yielded the best performance for estimating PI(R^(2) = 0.834, RMSE = 4.344 d), IH(R^(2) = 0.877, RMSE = 2.721 d), and FH(R^(2) = 0.883, RMSE = 2.694 d). Overall, UAV-based rice PH dynamics combined with machine learning effectively estimated the key phenological dates of multiple rice accessions, providing a novel approach for investigating key phenological dates in breeding work.
