Variations in Guangzhou's aerosol optical characteristics and their possible causes are studied against the large-scale background of South China Sea summer monsoons(SCSSM) using aerosol data derived from Panyu At...Variations in Guangzhou's aerosol optical characteristics and their possible causes are studied against the large-scale background of South China Sea summer monsoons(SCSSM) using aerosol data derived from Panyu Atmospheric Composition Watch Station in Guangzhou and the National Centers for Environmental Prediction/National Center for Atmospheric Research(USA). The data is reanalyzed to develop a composite analysis and perform physical diagnoses. Analysis of the results shows that aerosol extinction in Guangzhou first increases then decreases during the active period of a SCSSM, with variations in the stratification of the planetary boundary layer(PBL) and environmental winds playing important roles in affecting Guangzhou's aerosol optical characteristics. Regional diabatic heating and anomalous cyclonic circulations excited by monsoon convection induce environmental wind anomalies that significantly modify the stratification of the PBL.展开更多
As a high-resolution optical imaging technology,Optical Coherence Tomography(OCT)has been widely used in the diagnosis and treatment of cardiovascular diseases.It has played an important role in the detection and iden...As a high-resolution optical imaging technology,Optical Coherence Tomography(OCT)has been widely used in the diagnosis and treatment of cardiovascular diseases.It has played an important role in the detection and identification of atherosclerotic plaques and has significant advantages.In this paper,we realized to extract the optical characteristic parameters of the target sample based on the OCT data by establishing optical transmission models conforming to the OCT principle.The optical phantoms and coronary artery of domestic pig were used as research samples to study the difference between the optical properties of the cardiovascular tissues.It can provide a basic method for further study of optical characteristic parameters of atherosclerotic plaques,and also lay a foundation for realizing the quantitative evaluation of atherosclerotic plaques with multiple optical characteristic parameters in the future.展开更多
In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the can...In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the canonical Z-scan technique under femtosecond laser(wavelength: 800 nm, pulse width: 100 fs) excitation. Through controlling the applied femtosecond laser energy, NSA of the GO films can be tuned continuously. The GO film is placed at the focal plane as a unique amplitude filter to improve the resolution of the focused field. A multi-layer system model is proposed to present the generation of a deep sub-wavelength spot associated with the nonlinearity of GO films. Moreover, the parameter conditions to achieve the best resolution(~λ/6) are determined entirely. The demonstrated results here are useful for high density optical recoding and storage, nanolithography, and super-resolution optical imaging.展开更多
In this paper, we design a one-dimensional(1D) parity-time-symmetric periodic ring optical waveguide network(PTSPROWN) and investigate its extraordinary optical characteristics. It is found that quite different from t...In this paper, we design a one-dimensional(1D) parity-time-symmetric periodic ring optical waveguide network(PTSPROWN) and investigate its extraordinary optical characteristics. It is found that quite different from traditional vacuum/dielectric optical waveguide networks, 1D PTSPROWN cannot produce a photonic ordinary propagation mode, but can generate simultaneously two kinds of photonic nonpropagation modes: attenuation propagation mode and gain propagation mode. It creates neither passband nor stopband and possesses no photonic band structure. This makes 1D PTSPROWN possess richer spontaneous PT-symmetric breaking points and causes interesting extremum spontaneous PT-symmetric breaking points to appear, where electromagnetic waves can create ultrastrong extraordinary transmission, reflection, and localization, and the maximum can arrive at 6.6556 × 10^(12) and is more than 7 orders of magnitude larger than the results reported previously.1D PTSPROWN may possess potential in designing high-efficiency optical energy saver devices, optical amplifiers, optical switches with ultrahigh monochromaticity, and so on.展开更多
We analyzed the characteristics of cross-modulations (XM) and their recovery times in a semiconductor optical amplifier by a newly-developed TMM. The calculated results suggest faster recovery of the XMs by introducin...We analyzed the characteristics of cross-modulations (XM) and their recovery times in a semiconductor optical amplifier by a newly-developed TMM. The calculated results suggest faster recovery of the XMs by introducing a high-power assist light.展开更多
The results of the study of oscillograms of voltage,current,pulsed electric power and energy input into the plasma of an overstressed nanosecond discharge between aluminum electrodes in argon and mixtures of nitrogen ...The results of the study of oscillograms of voltage,current,pulsed electric power and energy input into the plasma of an overstressed nanosecond discharge between aluminum electrodes in argon and mixtures of nitrogen with oxygen(100-1)at pressures in the range of 13.3-103.3 kPa are presented,the emission plasma spectra are studied.It is shown that in mixtures of nitrogen with oxygen at atmospheric pressure,nanoparticles of aluminum oxide(Al2O3)are formed,the luminescence of which manifests itself in the spectral range of 200-600 nm and which is associated with the formation of F-,F+-centers and more complex aggregate formations based on oxygen vacancies.Calculations of the electron-kinetic coefficients of plasma,transport characteristics,such as mean electron energies in the range 5.116-13.41 eV,are given.The electron concentration was 1.6∙10^(20)m^(-3)-1.1∙10^(20)m^(-3)at a current density of 5.1∙10^(6)A/m^(2)and l.02∙10^(7)A/m^(2)on the surface of the electrode of the radiation source(0.196·10^(-4)m^(2)).Also drift velocities,temperatures and concentrations of electrons,specific losses of the discharge power for elastic and inelastic processes of collisions of electrons per unit of the total concentration of the mixture from the reduced electric field strength(E/N)for a mixture of aluminum,nitrogen,oxygen,rate constants of collisions of electrons with aluminum atoms on the E/N parameter in plasma on a mixture of aluminum vapor,oxygen and nitrogen=30:1000:100000 Pa at a total mixture pressure of P=101030 Pa are given.展开更多
We experimentally discussed the output characteristics of a passively mode-locked erbium-doped fiber laser using a single-mode fiber(SMF)structure as a saturable absorber(SA)based on nonlinear optic loop mirror(NOLM)....We experimentally discussed the output characteristics of a passively mode-locked erbium-doped fiber laser using a single-mode fiber(SMF)structure as a saturable absorber(SA)based on nonlinear optic loop mirror(NOLM).The NOLM acting as an SA has properties of controllable pulse interval and pulse width.Four different types of NOLMs are experimentally discussed and the results show that fine adjustment to the coupler ratio together with optimization of the SMF length inside the NOLM can simultaneously implement high pulse energy and pulse internal tunability.The laser configuration provides a method to generate well-performing mode-locked lasing,and the investigations of the effects of changing some parameters of the laser also provide some help for the development of mode-locked fiber laser based on NOLM.展开更多
Due to the combined effect of sluices and sea tide,the sluice-controlled coastal plain river would be characterized by both trophic state and salinity gradients,affecting the spatiotemporal optical properties of disso...Due to the combined effect of sluices and sea tide,the sluice-controlled coastal plain river would be characterized by both trophic state and salinity gradients,affecting the spatiotemporal optical properties of dissolved organicmatter(DOM).In this study,we investigated the spatiotemporal variation of water quality parameters and optical properties of DOM in the Haihe River,a representative sluice-controlled coastal plain river in Tianjin,China.A significant salinity gradient and four trophic states were observed in the water body of the Haihe River.Two humic-and one protein-like substances were identified from the DOM by the three-dimensional fluorescence spectra combined with the parallel factor(PARAFAC)analysis.Pearson’s correlation analysis and redundancy analysis(RDA)showed that the salinity significantly affected the abundance of chromophoric DOM(CDOM)but did not cause significant changes in the fluorescence optical characteristics.In addition,the effect of Trophic state index(TSI)on the CDOM abundance was greater than that on the fluorescence intensity of fluorescent dissolved organic matter(FDOM).In the water body with both salinity and trophic state gradients,TSI posed a greater influence than salinity on the CDOM abundance.Our results fill the research gap in spatiotemporal DOM characteristics and water quality variation in water bodies with both salinity and trophic state gradients.These results are beneficial for clarifying the joint influence of saline intrusion and sluices on the DOM characteristics and water quality in sluice-controlled coastal plain rivers.展开更多
Metallic glasses are spatially heterogeneous at the nanometer scale.However,the effects of external excitation on their structural and mechanical heterogeneity and the correlation to their properties are still unresol...Metallic glasses are spatially heterogeneous at the nanometer scale.However,the effects of external excitation on their structural and mechanical heterogeneity and the correlation to their properties are still unresolved.Nanoindentation,atomic force microscopy(AFM) and high-resolution transmis sion elec tron micro scopy(HRTEM) were carried out to explore the effects of cryogenic thermal cycling(CTC) on mechanical/structural heterogeneity,nano sc ale creep deformation and optical properties of nano structured metallic glass thin films(MGTFs).The results indicate that CTC treatment alters the distribution fluctuations of hardness/modulus and energy dissipation and results in an increase-then-decrease variation in mechanical heterogeneity.By applying Maxwell-Voigt model,it can be shown that CTC treatment results in a remarkable activation of more defects with longer relaxation time in soft regions but has only a slight effect on defects in hard regions.In addition,CTC treatment increases the transition time from primary-state stage to steady-state stage during creep deformation.The enhanced optical reflectivity of the MGTFs after 15 thermal cycles can be attributed to increased aggregation of Cu and Ni elements.The results of this study shed new light on understanding mechanical/structural heterogeneity and its influence on nanoscale creep deformation and optical characteristics of nanostructured MGTFs,and facilitate the design of high-performance nanostructured MGTFs.展开更多
While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is on...While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is one of the security issues which have negative effect on information security in optical networks.Optical fiber in optical networks has some nonlinear characteristics,such as self phase modulation(SPM),cross phase modulation(XPM),four-wave mixing(FWM)and stimulated Raman scattering(SRS).They can be used to implement high power inter-channel crosstalk attack by malicious attackers.The mechanism of high power inter-channel crosstalk attack is analyzed.When an attack occurs,attack signal power and fiber nonlinear refractive index are the main factors which affect quality of legitimate signals.The effect of high power inter-channel crosstalk attack on quality of legitimate signals is investigated by building simulation system in VPI software.The results show that interchannel crosstalk caused by high power attack signal leads to quality deterioration of legitimate signals propagated in the same fiber.The higher the power of attack signal is,the greater the fiber nonlinear refractive index is.The closer the channel spacing away from the attack signal is,the more seriously the legitimate signals are affected by attack.We also find that when attack position and power of attack signal are constant,attack signal cannot infinitely spread,while its attack ability shows a fading trend with the extension of propagation distance.展开更多
The optical and optoelectronic characteristics of SnS nanosheets with strong anisotropic crystal structure are researched.Transmission electron microscopy and polarized Raman spectra are used to determine the crystal ...The optical and optoelectronic characteristics of SnS nanosheets with strong anisotropic crystal structure are researched.Transmission electron microscopy and polarized Raman spectra are used to determine the crystal orientation of SnS nanosheets.The photodetector based on SnS nanosheets exhibits the carrier mobility of 37.75 cm^(2)/V·s,photoresponsivity of 310.5 A/W and external quantum efficiency of 8.56×10^(4)%at 450 nm.Optical absorption around the absorption edge presents obvious polarization sensitivity with the highest optical absorption dichroic ratio of 3.06 at 862 nm.Due to anisotropic optical absorption,the polarized photocurrent appears as the periodic change affected by the polarized direction of the incident light at 808 nm.Overall,SnS nanosheets show good potential in the future application of the polarized photodetectors for specific wavelength.展开更多
InGaN/GaN multiple quantum-well(MQW) structures with a wavelength range of green were successfully grown on a c-plane GaN template with SiO_2 stripe patterns along the [11-20] and [1-100] directions as a mask. The sur...InGaN/GaN multiple quantum-well(MQW) structures with a wavelength range of green were successfully grown on a c-plane GaN template with SiO_2 stripe patterns along the [11-20] and [1-100] directions as a mask. The surface morphologies of both samples were investigated using scanning electron microscopy and demonstrated anisotropic growth characteristics of GaN. The optical characteristics were investigated using Raman spectra and photoluminescence(PL). The InGaN/GaN MQW structure grown on the GaN template with SiO_2 stripes along the [1-100] orientation exhibited less stress and higher PL intensity.Transmission electron microscopy results indicated that portions of MQWs were grown on an inclined semipolar plane, and air voids occurred only when the direction of the mask stripe was along the [1-100] orientation. The enhancement of the optical characteristic was due to the air-void structure and inclined semipolar quantum-well sidewalls.展开更多
This paper focused on the impact of window shades’physical characteristics and opening modes on annual air conditioning energy consumption of residential buildings in China.Three building models with different window...This paper focused on the impact of window shades’physical characteristics and opening modes on annual air conditioning energy consumption of residential buildings in China.Three building models with different window layouts were proposed initially,and then validated by the dimensionless indicator annual energy performance(AEP)to determine the final building model adopted in this study.Harbin,Beijing,Guangzhou,Changsha and Kunming were selected to represent five different climate zones in China.The shading model has taken six physical characteristics of window shades,viz.outer emissivity,inner emissivity,solar transmittance,solar reflectance,thermal infrared transmittance,conductivity and two opening modes,viz.up&down mode as well as left&right mode,into consideration.Besides,the window shades operation schedule was summarized through 949 valid questionnaires.The annual air conditioning energy consumption was calculated via EnergyPlus software,and then the impact of the above different opening modes and parameters on energy use were investigated.The analysis results indicated that the top&bottom opening mode is better than the left&right mode when used in Harbin,and the effect of two different modes in air conditioning energy consumption in Kunming is similar.But in the other three cities,the left and right mode is preferred.Besides,the analysis results of the impact of different physical characteristics on air conditioning energy use in different climate zones could help improve the energy performance of window shades.展开更多
We propose a WDM-PON system as one of the promising candidates for next generation high capacity, cost-effective and inter-operable optical access network system and develop an ONU using reflective SOA transmitter for...We propose a WDM-PON system as one of the promising candidates for next generation high capacity, cost-effective and inter-operable optical access network system and develop an ONU using reflective SOA transmitter for the WDM-PON system.展开更多
Codoping with M^(n+) ions (M^(n+)=Li^(+),Mn^(2+) and Cu^(2+)) enhanced the blue and red upconversion (UC)emissions in TiO_(2):Yb^(3+)/Tm^(3+) nanocrystals under 980 nm excitation.The different effects of Li^(+),Mn^(2+...Codoping with M^(n+) ions (M^(n+)=Li^(+),Mn^(2+) and Cu^(2+)) enhanced the blue and red upconversion (UC)emissions in TiO_(2):Yb^(3+)/Tm^(3+) nanocrystals under 980 nm excitation.The different effects of Li^(+),Mn^(2+) and Cu^(2+) ions on the phase structures,morphologies and optical characteristics of TiO_(2):Yb^(3+)/Tm^(3+)were discussed.The minor shifting in the diffraction peaks at 25.2°was observed for TiO_(2):Yb^(3+)/Tm^(3+)/Li^(+),and adding Mn^(2+) ions remained almost the same position of diffraction peaks,while the introduction of Cu^(2+) ions resulted in the shift of the diffraction peaks towards the larger angles.TiO_(2):Yb^(3+)/Tm^(3+)/Li^(+)and TiO_(2):Yb^(3+)/Tm^(3+)/Mn^(2+) nanosheets and the sphere-like TiO_(2):Yb^(3+)/Tm^(3+)/Cu^(2+) were observed.The mechanisms for increased UC emissions caused by adding Li^(+),Mn^(2+) and Cu^(2+) ions were attributed to the tailored local environment around Tm^(3+) ions,efficient energy transition between Mn^(2+) -Yb^(3+) dimer and Tm^(3+) ions,and the localized surface plasmon resonance (LSPR) of Cu^(2+) ions,respectively.展开更多
基金Major State Basic Research Development Program(973 Program)of China(2011CB403403)Guangdong Science and Technology Planning Project(2012A061400012,2012A030200006)National Natural Science Foundation of China(41205069)
文摘Variations in Guangzhou's aerosol optical characteristics and their possible causes are studied against the large-scale background of South China Sea summer monsoons(SCSSM) using aerosol data derived from Panyu Atmospheric Composition Watch Station in Guangzhou and the National Centers for Environmental Prediction/National Center for Atmospheric Research(USA). The data is reanalyzed to develop a composite analysis and perform physical diagnoses. Analysis of the results shows that aerosol extinction in Guangzhou first increases then decreases during the active period of a SCSSM, with variations in the stratification of the planetary boundary layer(PBL) and environmental winds playing important roles in affecting Guangzhou's aerosol optical characteristics. Regional diabatic heating and anomalous cyclonic circulations excited by monsoon convection induce environmental wind anomalies that significantly modify the stratification of the PBL.
基金This work was supported by the National Natural Science Foundation of China(61975017,61905015).
文摘As a high-resolution optical imaging technology,Optical Coherence Tomography(OCT)has been widely used in the diagnosis and treatment of cardiovascular diseases.It has played an important role in the detection and identification of atherosclerotic plaques and has significant advantages.In this paper,we realized to extract the optical characteristic parameters of the target sample based on the OCT data by establishing optical transmission models conforming to the OCT principle.The optical phantoms and coronary artery of domestic pig were used as research samples to study the difference between the optical properties of the cardiovascular tissues.It can provide a basic method for further study of optical characteristic parameters of atherosclerotic plaques,and also lay a foundation for realizing the quantitative evaluation of atherosclerotic plaques with multiple optical characteristic parameters in the future.
基金supported by the National Natural Science Foundation of China(Nos.61575139,51602213 and 11604236)the Young Science Foundation of Taiyuan University of Technology(No.2015QN066)
文摘In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption(NSA) of graphene oxide(GO) membranes. The third-order optical nonlinearities are characterized by the canonical Z-scan technique under femtosecond laser(wavelength: 800 nm, pulse width: 100 fs) excitation. Through controlling the applied femtosecond laser energy, NSA of the GO films can be tuned continuously. The GO film is placed at the focal plane as a unique amplitude filter to improve the resolution of the focused field. A multi-layer system model is proposed to present the generation of a deep sub-wavelength spot associated with the nonlinearity of GO films. Moreover, the parameter conditions to achieve the best resolution(~λ/6) are determined entirely. The demonstrated results here are useful for high density optical recoding and storage, nanolithography, and super-resolution optical imaging.
基金National Natural Science Foundation of China(NSFC)(11674107,11775083,61475049,61771205,61774062)Natural Science Foundation of Guangdong Province(2015A030313374)Scientific Research Foundation of Graduate School of South China Normal University(2015lkxm27,2017lkxm091)
文摘In this paper, we design a one-dimensional(1D) parity-time-symmetric periodic ring optical waveguide network(PTSPROWN) and investigate its extraordinary optical characteristics. It is found that quite different from traditional vacuum/dielectric optical waveguide networks, 1D PTSPROWN cannot produce a photonic ordinary propagation mode, but can generate simultaneously two kinds of photonic nonpropagation modes: attenuation propagation mode and gain propagation mode. It creates neither passband nor stopband and possesses no photonic band structure. This makes 1D PTSPROWN possess richer spontaneous PT-symmetric breaking points and causes interesting extremum spontaneous PT-symmetric breaking points to appear, where electromagnetic waves can create ultrastrong extraordinary transmission, reflection, and localization, and the maximum can arrive at 6.6556 × 10^(12) and is more than 7 orders of magnitude larger than the results reported previously.1D PTSPROWN may possess potential in designing high-efficiency optical energy saver devices, optical amplifiers, optical switches with ultrahigh monochromaticity, and so on.
文摘We analyzed the characteristics of cross-modulations (XM) and their recovery times in a semiconductor optical amplifier by a newly-developed TMM. The calculated results suggest faster recovery of the XMs by introducing a high-power assist light.
文摘The results of the study of oscillograms of voltage,current,pulsed electric power and energy input into the plasma of an overstressed nanosecond discharge between aluminum electrodes in argon and mixtures of nitrogen with oxygen(100-1)at pressures in the range of 13.3-103.3 kPa are presented,the emission plasma spectra are studied.It is shown that in mixtures of nitrogen with oxygen at atmospheric pressure,nanoparticles of aluminum oxide(Al2O3)are formed,the luminescence of which manifests itself in the spectral range of 200-600 nm and which is associated with the formation of F-,F+-centers and more complex aggregate formations based on oxygen vacancies.Calculations of the electron-kinetic coefficients of plasma,transport characteristics,such as mean electron energies in the range 5.116-13.41 eV,are given.The electron concentration was 1.6∙10^(20)m^(-3)-1.1∙10^(20)m^(-3)at a current density of 5.1∙10^(6)A/m^(2)and l.02∙10^(7)A/m^(2)on the surface of the electrode of the radiation source(0.196·10^(-4)m^(2)).Also drift velocities,temperatures and concentrations of electrons,specific losses of the discharge power for elastic and inelastic processes of collisions of electrons per unit of the total concentration of the mixture from the reduced electric field strength(E/N)for a mixture of aluminum,nitrogen,oxygen,rate constants of collisions of electrons with aluminum atoms on the E/N parameter in plasma on a mixture of aluminum vapor,oxygen and nitrogen=30:1000:100000 Pa at a total mixture pressure of P=101030 Pa are given.
基金supported in part by the Zhejiang Province Science and Technology Plan Projects(No.LGG19F050001)the National Natural Science Foundation of China(No.601705055)the Zhejiang Provincial Natural Science Foundation of China(No.LY17F050012)。
文摘We experimentally discussed the output characteristics of a passively mode-locked erbium-doped fiber laser using a single-mode fiber(SMF)structure as a saturable absorber(SA)based on nonlinear optic loop mirror(NOLM).The NOLM acting as an SA has properties of controllable pulse interval and pulse width.Four different types of NOLMs are experimentally discussed and the results show that fine adjustment to the coupler ratio together with optimization of the SMF length inside the NOLM can simultaneously implement high pulse energy and pulse internal tunability.The laser configuration provides a method to generate well-performing mode-locked lasing,and the investigations of the effects of changing some parameters of the laser also provide some help for the development of mode-locked fiber laser based on NOLM.
基金This work was supported by the National Science Foundation of China(No.41807386).The authors gratefully acknowledge the warm help from Prof.Baoli Wang and PhD studentWanzhu Li during themeasurement of chlorophyll a.We greatly appreciate Prof.Wei He for his help in the use of the efc toolbox.We are deeply grateful to Prof.Jinyu Yang for her warm suggestion in the statistical analysis.We thank all staff and students that helped with sample collection and measurements.Scientific compass(www.shiyanjia.com)is gratefully appreciated for their service in the polish of manuscript.
文摘Due to the combined effect of sluices and sea tide,the sluice-controlled coastal plain river would be characterized by both trophic state and salinity gradients,affecting the spatiotemporal optical properties of dissolved organicmatter(DOM).In this study,we investigated the spatiotemporal variation of water quality parameters and optical properties of DOM in the Haihe River,a representative sluice-controlled coastal plain river in Tianjin,China.A significant salinity gradient and four trophic states were observed in the water body of the Haihe River.Two humic-and one protein-like substances were identified from the DOM by the three-dimensional fluorescence spectra combined with the parallel factor(PARAFAC)analysis.Pearson’s correlation analysis and redundancy analysis(RDA)showed that the salinity significantly affected the abundance of chromophoric DOM(CDOM)but did not cause significant changes in the fluorescence optical characteristics.In addition,the effect of Trophic state index(TSI)on the CDOM abundance was greater than that on the fluorescence intensity of fluorescent dissolved organic matter(FDOM).In the water body with both salinity and trophic state gradients,TSI posed a greater influence than salinity on the CDOM abundance.Our results fill the research gap in spatiotemporal DOM characteristics and water quality variation in water bodies with both salinity and trophic state gradients.These results are beneficial for clarifying the joint influence of saline intrusion and sluices on the DOM characteristics and water quality in sluice-controlled coastal plain rivers.
基金financially supported by the National Natural Science Foundation of China (Nos. 51971061 and 52231005)the Natural Science Foundation of Jiangsu Province (No. BK20221474)。
文摘Metallic glasses are spatially heterogeneous at the nanometer scale.However,the effects of external excitation on their structural and mechanical heterogeneity and the correlation to their properties are still unresolved.Nanoindentation,atomic force microscopy(AFM) and high-resolution transmis sion elec tron micro scopy(HRTEM) were carried out to explore the effects of cryogenic thermal cycling(CTC) on mechanical/structural heterogeneity,nano sc ale creep deformation and optical properties of nano structured metallic glass thin films(MGTFs).The results indicate that CTC treatment alters the distribution fluctuations of hardness/modulus and energy dissipation and results in an increase-then-decrease variation in mechanical heterogeneity.By applying Maxwell-Voigt model,it can be shown that CTC treatment results in a remarkable activation of more defects with longer relaxation time in soft regions but has only a slight effect on defects in hard regions.In addition,CTC treatment increases the transition time from primary-state stage to steady-state stage during creep deformation.The enhanced optical reflectivity of the MGTFs after 15 thermal cycles can be attributed to increased aggregation of Cu and Ni elements.The results of this study shed new light on understanding mechanical/structural heterogeneity and its influence on nanoscale creep deformation and optical characteristics of nanostructured MGTFs,and facilitate the design of high-performance nanostructured MGTFs.
基金the National Natural Science Foundation of China(No.61179002)the National Defence Foundation of China(No.2012JY002-260)
文摘While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is one of the security issues which have negative effect on information security in optical networks.Optical fiber in optical networks has some nonlinear characteristics,such as self phase modulation(SPM),cross phase modulation(XPM),four-wave mixing(FWM)and stimulated Raman scattering(SRS).They can be used to implement high power inter-channel crosstalk attack by malicious attackers.The mechanism of high power inter-channel crosstalk attack is analyzed.When an attack occurs,attack signal power and fiber nonlinear refractive index are the main factors which affect quality of legitimate signals.The effect of high power inter-channel crosstalk attack on quality of legitimate signals is investigated by building simulation system in VPI software.The results show that interchannel crosstalk caused by high power attack signal leads to quality deterioration of legitimate signals propagated in the same fiber.The higher the power of attack signal is,the greater the fiber nonlinear refractive index is.The closer the channel spacing away from the attack signal is,the more seriously the legitimate signals are affected by attack.We also find that when attack position and power of attack signal are constant,attack signal cannot infinitely spread,while its attack ability shows a fading trend with the extension of propagation distance.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.62004193 and 81900912)the National Key Research and Development Program of China(Grant No.2017YFA0207500)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB43000000)Beijing National Laboratory for Molecular Sciences(BNLMS201908).
文摘The optical and optoelectronic characteristics of SnS nanosheets with strong anisotropic crystal structure are researched.Transmission electron microscopy and polarized Raman spectra are used to determine the crystal orientation of SnS nanosheets.The photodetector based on SnS nanosheets exhibits the carrier mobility of 37.75 cm^(2)/V·s,photoresponsivity of 310.5 A/W and external quantum efficiency of 8.56×10^(4)%at 450 nm.Optical absorption around the absorption edge presents obvious polarization sensitivity with the highest optical absorption dichroic ratio of 3.06 at 862 nm.Due to anisotropic optical absorption,the polarized photocurrent appears as the periodic change affected by the polarized direction of the incident light at 808 nm.Overall,SnS nanosheets show good potential in the future application of the polarized photodetectors for specific wavelength.
基金supported by the Key Research and Development Program in Shaanxi Province (Grant Nos. 2018ZDCXL-GY-01-02-02 and 2018ZDCXLGY-01-07)Wuhu and Xidian University Special Fund for Industry University Research Cooperation (Grant No. XWYCXY-012020007)+2 种基金the National Natural Science Foundation of China (Grant No. 62074120)the Fundamental Research Funds for the Central Universitiesthe Innovation Fund of Xidian University。
文摘InGaN/GaN multiple quantum-well(MQW) structures with a wavelength range of green were successfully grown on a c-plane GaN template with SiO_2 stripe patterns along the [11-20] and [1-100] directions as a mask. The surface morphologies of both samples were investigated using scanning electron microscopy and demonstrated anisotropic growth characteristics of GaN. The optical characteristics were investigated using Raman spectra and photoluminescence(PL). The InGaN/GaN MQW structure grown on the GaN template with SiO_2 stripes along the [1-100] orientation exhibited less stress and higher PL intensity.Transmission electron microscopy results indicated that portions of MQWs were grown on an inclined semipolar plane, and air voids occurred only when the direction of the mask stripe was along the [1-100] orientation. The enhancement of the optical characteristic was due to the air-void structure and inclined semipolar quantum-well sidewalls.
基金the financial supports provided by the National Natural Science Foundation of China(Project no.51978252)China National Key R&D Program‘Solutions to heating and cooling of buildings in the Yangtze River region’(Grant no.2016YFC0700305).
文摘This paper focused on the impact of window shades’physical characteristics and opening modes on annual air conditioning energy consumption of residential buildings in China.Three building models with different window layouts were proposed initially,and then validated by the dimensionless indicator annual energy performance(AEP)to determine the final building model adopted in this study.Harbin,Beijing,Guangzhou,Changsha and Kunming were selected to represent five different climate zones in China.The shading model has taken six physical characteristics of window shades,viz.outer emissivity,inner emissivity,solar transmittance,solar reflectance,thermal infrared transmittance,conductivity and two opening modes,viz.up&down mode as well as left&right mode,into consideration.Besides,the window shades operation schedule was summarized through 949 valid questionnaires.The annual air conditioning energy consumption was calculated via EnergyPlus software,and then the impact of the above different opening modes and parameters on energy use were investigated.The analysis results indicated that the top&bottom opening mode is better than the left&right mode when used in Harbin,and the effect of two different modes in air conditioning energy consumption in Kunming is similar.But in the other three cities,the left and right mode is preferred.Besides,the analysis results of the impact of different physical characteristics on air conditioning energy use in different climate zones could help improve the energy performance of window shades.
文摘We propose a WDM-PON system as one of the promising candidates for next generation high capacity, cost-effective and inter-operable optical access network system and develop an ONU using reflective SOA transmitter for the WDM-PON system.
基金supported by Guangdong Natural Science Funds for Distinguished Young Scholar(No.2015A030306041)Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program(No.2015TQ01N060)Major Foundation of Guangzhou Science and Technology(No.201804020005)。
文摘Codoping with M^(n+) ions (M^(n+)=Li^(+),Mn^(2+) and Cu^(2+)) enhanced the blue and red upconversion (UC)emissions in TiO_(2):Yb^(3+)/Tm^(3+) nanocrystals under 980 nm excitation.The different effects of Li^(+),Mn^(2+) and Cu^(2+) ions on the phase structures,morphologies and optical characteristics of TiO_(2):Yb^(3+)/Tm^(3+)were discussed.The minor shifting in the diffraction peaks at 25.2°was observed for TiO_(2):Yb^(3+)/Tm^(3+)/Li^(+),and adding Mn^(2+) ions remained almost the same position of diffraction peaks,while the introduction of Cu^(2+) ions resulted in the shift of the diffraction peaks towards the larger angles.TiO_(2):Yb^(3+)/Tm^(3+)/Li^(+)and TiO_(2):Yb^(3+)/Tm^(3+)/Mn^(2+) nanosheets and the sphere-like TiO_(2):Yb^(3+)/Tm^(3+)/Cu^(2+) were observed.The mechanisms for increased UC emissions caused by adding Li^(+),Mn^(2+) and Cu^(2+) ions were attributed to the tailored local environment around Tm^(3+) ions,efficient energy transition between Mn^(2+) -Yb^(3+) dimer and Tm^(3+) ions,and the localized surface plasmon resonance (LSPR) of Cu^(2+) ions,respectively.