To promote the application of far-infrared technology,functional far-infrared devices with high performance are needed.Here,we propose a design scheme to develop a wide-incident-angle far-infrared absorber,which consi...To promote the application of far-infrared technology,functional far-infrared devices with high performance are needed.Here,we propose a design scheme to develop a wide-incident-angle far-infrared absorber,which consists of a periodically semicircle-patterned graphene sheet,a lossless inter-dielectric spacer and a gold reflecting film.Under normal incidence for both TE-and TM-polarization modes,the bandwidth of 90%absorption of the proposed far-infrared absorber is ranging from 6.76 THz to 11.05 THz.The absorption remains more than 90%over a 4.29-THz broadband range when the incident angle is up to 50◦for both TE-and TM-polarization modes.The peak absorbance of the absorber can be flexibly tuned from 10%to 100%by changing the chemical potential from 0 eV to 0.6 eV.The tunable broadband far-infrared absorber has promising applications in sensing,detection,and stealth objects.展开更多
This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic ch...This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic characteristics of this perfect metamaterial absorber(PMA)for microwave wireless communications.The fundamental unit cell of the proposed MA consists of two pentagonal-shaped resonators and two inverse C-shaped metallic components surrounded by a split ring resonator(SRR).The bottom thin copper deposit and upper metallic resonator surface are disjoined by an FR-4 dielectric substrate with 1.6 mm thickness.The CST MW studio,a high-frequency electromagnetic simulator has been deployed for numerical simula-tion of the unit cell in the frequency range of 4 to 14 GHz.In the TE mode,the offered MA structure demonstrated three different absorption peaks at 6.85 GHz(C-band),8.87 GHz(X-band),and 12.03 GHz(Ku-band),with 96.82%,99.24%,and 99.43%absorptivity,respectively.The electric field,magnetic field,and surface current distribution were analysed using Maxwell’s-Curl equations,whereas the angle sensitivity was investigated to comprehend the absorption mechanism of the proposed absorber.The numerical results were verified using the Ansys HFSS(high-frequency structure simulator)and ADS(advanced design system)for equivalent circuit models.Moreover,the proposed MA is polarisation and incident angle independent.Hence,the application of this MA can be extended to a great extent,including airborne radar applications,defence,and stealth-coating technology.展开更多
Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great impo...Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.展开更多
Squealer tip is widely used in turbines to reduce tip leakage loss.In typical turbine environment,the squealer tip leakage flow is affected by multiple factors such as the relative casing motion and the wide range of ...Squealer tip is widely used in turbines to reduce tip leakage loss.In typical turbine environment,the squealer tip leakage flow is affected by multiple factors such as the relative casing motion and the wide range of variable incidence angles.The development of experimental methods which can accurately model the real turbine environment and influencing factors is of great significance to study the squealer tip leakage flow mechanism.In the present paper,a low-speed turbine cascade test facility which can model the relative casing motion and wide range of variable incidence angles(-25°to 55°)is built.Based on the similarity criteria,a high-low speed similarity transformation method of the turbine cascade is established by considering the thickness of the turbine blade.A combined testing method of Particle Image Velocimetry(PIV)and local pressure measurement is proposed to obtain the complex flow structures within the tip cavity.The results show that the experimental method can successfully model the relative casing motion and the wide range of variable incidence angles.The low-speed cascade obtained by the similarity transformation can model the high-speed flow accurately.The measurement technique developed can obtain the complex flow field and successfully capture the scraping vortex within the squealer tip.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF0200306)the National Natural Science Foundation of China(Grant Nos.61871355 and 61831012).
文摘To promote the application of far-infrared technology,functional far-infrared devices with high performance are needed.Here,we propose a design scheme to develop a wide-incident-angle far-infrared absorber,which consists of a periodically semicircle-patterned graphene sheet,a lossless inter-dielectric spacer and a gold reflecting film.Under normal incidence for both TE-and TM-polarization modes,the bandwidth of 90%absorption of the proposed far-infrared absorber is ranging from 6.76 THz to 11.05 THz.The absorption remains more than 90%over a 4.29-THz broadband range when the incident angle is up to 50◦for both TE-and TM-polarization modes.The peak absorbance of the absorber can be flexibly tuned from 10%to 100%by changing the chemical potential from 0 eV to 0.6 eV.The tunable broadband far-infrared absorber has promising applications in sensing,detection,and stealth objects.
基金supported by Fundamental Research Grant Scheme(FRGS),MOE,Malaysia,Code:FRGS/1/2022/TK07/UKM/02/22.
文摘This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic characteristics of this perfect metamaterial absorber(PMA)for microwave wireless communications.The fundamental unit cell of the proposed MA consists of two pentagonal-shaped resonators and two inverse C-shaped metallic components surrounded by a split ring resonator(SRR).The bottom thin copper deposit and upper metallic resonator surface are disjoined by an FR-4 dielectric substrate with 1.6 mm thickness.The CST MW studio,a high-frequency electromagnetic simulator has been deployed for numerical simula-tion of the unit cell in the frequency range of 4 to 14 GHz.In the TE mode,the offered MA structure demonstrated three different absorption peaks at 6.85 GHz(C-band),8.87 GHz(X-band),and 12.03 GHz(Ku-band),with 96.82%,99.24%,and 99.43%absorptivity,respectively.The electric field,magnetic field,and surface current distribution were analysed using Maxwell’s-Curl equations,whereas the angle sensitivity was investigated to comprehend the absorption mechanism of the proposed absorber.The numerical results were verified using the Ansys HFSS(high-frequency structure simulator)and ADS(advanced design system)for equivalent circuit models.Moreover,the proposed MA is polarisation and incident angle independent.Hence,the application of this MA can be extended to a great extent,including airborne radar applications,defence,and stealth-coating technology.
基金Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515011071,2019A1515111093,and 2022A1515011614)the National Natural Science Foundation of China(Nos.62122034,61875082,61905107,62204107,and 62205138)+2 种基金Innovation Project of Department of Education of Guangdong Province(No.2019KTSCX157)Shenzhen Innovation Project(Nos.JCYJ20210324104413036 and JCYJ20190809152411655)Q.Q.W.and H.M.Z.acknowledge the support from China Postdoctoral Science Foundation(Nos.2021M691397 and 2021M691411).
文摘Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.
基金supported by the National Natural Science Foundation of China(No.51676005)。
文摘Squealer tip is widely used in turbines to reduce tip leakage loss.In typical turbine environment,the squealer tip leakage flow is affected by multiple factors such as the relative casing motion and the wide range of variable incidence angles.The development of experimental methods which can accurately model the real turbine environment and influencing factors is of great significance to study the squealer tip leakage flow mechanism.In the present paper,a low-speed turbine cascade test facility which can model the relative casing motion and wide range of variable incidence angles(-25°to 55°)is built.Based on the similarity criteria,a high-low speed similarity transformation method of the turbine cascade is established by considering the thickness of the turbine blade.A combined testing method of Particle Image Velocimetry(PIV)and local pressure measurement is proposed to obtain the complex flow structures within the tip cavity.The results show that the experimental method can successfully model the relative casing motion and the wide range of variable incidence angles.The low-speed cascade obtained by the similarity transformation can model the high-speed flow accurately.The measurement technique developed can obtain the complex flow field and successfully capture the scraping vortex within the squealer tip.