Passive cooling holds tremendous potential in improving thermal comfort because of its zero energy consumption and cost-effectiveness.However,currently reported radiative cooling materials primarily focus on hydrophob...Passive cooling holds tremendous potential in improving thermal comfort because of its zero energy consumption and cost-effectiveness.However,currently reported radiative cooling materials primarily focus on hydrophobic polymer films,inevi-tably leading to sweat accumulation and limited cooling efficiency in hot-humid environments.Herein,an advanced Janus membrane with excellent temperature-moisture management capabilities is developed,which combines radiative cooling and evaporative heat dissipation.Modification with Calcium sulfite(CaSO3)nanoparticles not only enhances the optical properties(state-of-the-art solar reflectance of 96.6%,infrared emittance of 96.1%)but also improves the wettability of the polylactic acid fiber membrane.Especially 15%emittance improvement is achieved due to the strong infrared radiation ability of CaSO3.The membranes with opposite wettability realize the directional sweat transport(high one-way transport index of 945%).Excellent radiative cooling capability is demonstrated with sub-ambient cooling of 5.8°C in the dry state.The Janus membranes covering sweaty skin exhibit a 46%shorter drying time and a 2°C lower average evaporation temperature compared to cotton fabric,indicating highly efficient thermal and moisture management.This work provides an efficient route to achieving smart textiles that enable the human body to adapt to complex environmental conditions.展开更多
Free manipulation of electromagnetic waves in the terahertz(THz)band based on metasurface functional devices has been the focus of research in recent years.Among these devices,active metasurfaces have generated extens...Free manipulation of electromagnetic waves in the terahertz(THz)band based on metasurface functional devices has been the focus of research in recent years.Among these devices,active metasurfaces have generated extensive research interest due to their reconfigurability.In this work,we demonstrate a mechanically reconfigurable THz polarization converter that consists of two parallel transmissive metasurfaces with a tunable spacing.By mechanically adjusting the coupling strength between the metasurfaces,the orthogonal polarization conversion of the incident linearly polarized THz waves can be tuned.Specifically,the device can be tuned from efficient dual-frequency orthogonal polarization conversion to efficient single-frequency orthogonal polarization conversion.After a gradual decrease in efficiency,it is finally changed to a low transmission state as the gap distance increases from 150 to 800μm.We theoretically analyze the tuning process under different spacings and experimentally verify it using a vector network analyzer.Our proposed design is straightforward and robust,with the potential to find wide applications in THz science and technology.展开更多
The development of high-performance and low-cost oxygen reduction and evolution catalysts that can be easily integrated into existing devices is crucial for the wide deployment of energy storage systems that utilize O...The development of high-performance and low-cost oxygen reduction and evolution catalysts that can be easily integrated into existing devices is crucial for the wide deployment of energy storage systems that utilize O2-H2O chemistries, such as regenerative fuel cells and metal-air batteries. Herein, we report an NHB-activated N-doped hierarchical carbon （NHC） catalyst synthesized via a scalable route, and demonstrate its device integration. The NHC catalyst exhibited good performance for both the oxygen reduction reaction （ORR） and the oxygen evolution reaction （OER）, as demonstrated by means of electrochemical studies and evaluation when integrated into the oxygen electrode of a regenerative fuel cell. The activities observed for both the ORR and the OER were comparable to those achieved by state-of-the-art Pt and Ir catalysts in alkaline environments. We have further identified the critical role of carbon defects as active sites for electrochemical activity through density functional theory calculations and high-resolution TEM visualization. This work highlights the potential of NHC to replace commercial precious metals in regenerative fuel cells and possibly metal-air batteries for cost-effective storage of intermittent renewable energy.展开更多
The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles.This research introduced a validated computational fluid dynamics(CFD)model regard...The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles.This research introduced a validated computational fluid dynamics(CFD)model regarding this concern.Such an aerodynamic impact mechanism was explored;a relationship between the transverse distance between train and motor-van(hereinfafter referred to as van)and the aerodynamic effects on the van was explored to help the optimization of bridge decks,and the relationship between the automobile speed and aerodynamic variations of a van was fitted to help traffic control.The fitting results are accurate enough for further research.It is noted that the relative speed of the two automobiles is not the only factor that influences the aerodynamic variations of the van,even at a confirmed relative velocity,the aerodynamic variations of the van vary a lot as the velocity proportion changes,and the most unfavorable case shows an increase of over 40%on the aerodynamic variations compared to the standard case.The decay of the aerodynamic effects shows that not all the velocity terms would enhance the aerodynamic variations;the coupled velocity term constrains the variation amplitude of moments and decreases the total amplitude by 20%–40%.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFA1602700 and 2022YFB2502104)the National Natural Science Foundation of China(22375089)+1 种基金the Key Research and Development Program of Jiangsu Provincial Department of Science and Technology of China(BE2022332)Jiangsu Carbon Peak Carbon Neutralization Science and Technology Innovation Special Fund(BE2022605).
文摘Passive cooling holds tremendous potential in improving thermal comfort because of its zero energy consumption and cost-effectiveness.However,currently reported radiative cooling materials primarily focus on hydrophobic polymer films,inevi-tably leading to sweat accumulation and limited cooling efficiency in hot-humid environments.Herein,an advanced Janus membrane with excellent temperature-moisture management capabilities is developed,which combines radiative cooling and evaporative heat dissipation.Modification with Calcium sulfite(CaSO3)nanoparticles not only enhances the optical properties(state-of-the-art solar reflectance of 96.6%,infrared emittance of 96.1%)but also improves the wettability of the polylactic acid fiber membrane.Especially 15%emittance improvement is achieved due to the strong infrared radiation ability of CaSO3.The membranes with opposite wettability realize the directional sweat transport(high one-way transport index of 945%).Excellent radiative cooling capability is demonstrated with sub-ambient cooling of 5.8°C in the dry state.The Janus membranes covering sweaty skin exhibit a 46%shorter drying time and a 2°C lower average evaporation temperature compared to cotton fabric,indicating highly efficient thermal and moisture management.This work provides an efficient route to achieving smart textiles that enable the human body to adapt to complex environmental conditions.
基金supported by the National Natural Science Foundation of China(Nos.61935015,62375203,62335011,62075158,62025504,62175083)the Yunnan Expert Workstation(No.202205AF150008)+2 种基金the Independent Innovation Fund of Tianjin University(No.2024XPD-0012)the NaturalScienceFoundationofJilinProvince(No.20230101359JC)the Fundamental Research Funds for Central Universities。
文摘Free manipulation of electromagnetic waves in the terahertz(THz)band based on metasurface functional devices has been the focus of research in recent years.Among these devices,active metasurfaces have generated extensive research interest due to their reconfigurability.In this work,we demonstrate a mechanically reconfigurable THz polarization converter that consists of two parallel transmissive metasurfaces with a tunable spacing.By mechanically adjusting the coupling strength between the metasurfaces,the orthogonal polarization conversion of the incident linearly polarized THz waves can be tuned.Specifically,the device can be tuned from efficient dual-frequency orthogonal polarization conversion to efficient single-frequency orthogonal polarization conversion.After a gradual decrease in efficiency,it is finally changed to a low transmission state as the gap distance increases from 150 to 800μm.We theoretically analyze the tuning process under different spacings and experimentally verify it using a vector network analyzer.Our proposed design is straightforward and robust,with the potential to find wide applications in THz science and technology.
文摘The development of high-performance and low-cost oxygen reduction and evolution catalysts that can be easily integrated into existing devices is crucial for the wide deployment of energy storage systems that utilize O2-H2O chemistries, such as regenerative fuel cells and metal-air batteries. Herein, we report an NHB-activated N-doped hierarchical carbon （NHC） catalyst synthesized via a scalable route, and demonstrate its device integration. The NHC catalyst exhibited good performance for both the oxygen reduction reaction （ORR） and the oxygen evolution reaction （OER）, as demonstrated by means of electrochemical studies and evaluation when integrated into the oxygen electrode of a regenerative fuel cell. The activities observed for both the ORR and the OER were comparable to those achieved by state-of-the-art Pt and Ir catalysts in alkaline environments. We have further identified the critical role of carbon defects as active sites for electrochemical activity through density functional theory calculations and high-resolution TEM visualization. This work highlights the potential of NHC to replace commercial precious metals in regenerative fuel cells and possibly metal-air batteries for cost-effective storage of intermittent renewable energy.
基金The writers are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.51778544,51978589)the Fundamental Research Funds for the Central Universities(No.2682021CG014).
文摘The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles.This research introduced a validated computational fluid dynamics(CFD)model regarding this concern.Such an aerodynamic impact mechanism was explored;a relationship between the transverse distance between train and motor-van(hereinfafter referred to as van)and the aerodynamic effects on the van was explored to help the optimization of bridge decks,and the relationship between the automobile speed and aerodynamic variations of a van was fitted to help traffic control.The fitting results are accurate enough for further research.It is noted that the relative speed of the two automobiles is not the only factor that influences the aerodynamic variations of the van,even at a confirmed relative velocity,the aerodynamic variations of the van vary a lot as the velocity proportion changes,and the most unfavorable case shows an increase of over 40%on the aerodynamic variations compared to the standard case.The decay of the aerodynamic effects shows that not all the velocity terms would enhance the aerodynamic variations;the coupled velocity term constrains the variation amplitude of moments and decreases the total amplitude by 20%–40%.
