We investigate the electron retroreflection and the Klein tunneling across a graphene-based n-p-n junction irradiated by linearly polarized off-resonant light with the polarization along the x direction.The linearly p...We investigate the electron retroreflection and the Klein tunneling across a graphene-based n-p-n junction irradiated by linearly polarized off-resonant light with the polarization along the x direction.The linearly polarized off-resonant light modifies the band structure of graphene,which leads to the anisotropy of band structure.By adjusting the linearly polarized light and the direction of n-p-n junction simultaneously,the electron retroreflection appears and the anomalous Klein tunneling,the perfect transmission at a nonzero incident angle regardless of the width and height of potential barrier,happens,which arises from the fact that the light-induced anisotropic band structure changes the relation of wavevector and velocity of electron.Our finding provides an alternative and flexible method to modulate electron retroreflection and Klein tunneling.展开更多
Passive optical motion capture technology is an effective mean to conduct high-precision pose estimation of small scenes of mobile robots;nevertheless,in the case of complex background and stray light interference in ...Passive optical motion capture technology is an effective mean to conduct high-precision pose estimation of small scenes of mobile robots;nevertheless,in the case of complex background and stray light interference in the scene,due to the infuence of target adhesion and environmental reflection,this technology cannot estimate the pose accurately.A passive binocular optical motion capture technology under complex illumination based on binocular camera and fixed retroreflective marker balls has been proposed.By fixing multiple hemispherical retrorefective marker balls on a rigid base,it uses binocular camera for depth estimation to obtain the fixed position relationship between the feature points.After performing unsupervised state estimation without manual operation,it overcomes the infuence of refection spots in the background.Meanwhile,contour extraction and ellipse least square fitting are used to extract the marker balls with incomplete shape as the feature points,so as to solve the problem of target adhesion in the scene.A FANUC m10i-a robot moving with 6-DOF is used for verification using the above methods in a complex lighting environment of a welding laboratory.The result shows that the average of absolute position errors is 5.793mm,the average of absolute rotation errors is 1.997°the average of relative position errors is 0.972 mm,and the average of relative rotation errors is 0.002°.Therefore,this technology meets the requirements of high-precision measurement in a complex lighting environment when estimating the 6-DOF-motion mobile robot and has very significant application prospects in complex scenes.展开更多
Fiber optic displacement sensors are widely used in industry. Retro reflective fiber optic displacement sensor consists of parallel fibers with a reflector at a distance. Light is launched into the transmitting fiber ...Fiber optic displacement sensors are widely used in industry. Retro reflective fiber optic displacement sensor consists of parallel fibers with a reflector at a distance. Light is launched into the transmitting fiber which gets reflected by reflector. This reflected light is collected by the receiving fiber. The received light is function of the displacement of the reflector from the fiber end faces. This paper is targeted to obtain a robust design for the fiber optic displacement sensor (FODS) using well known Taguchi method. The design takes care of all noise parameters within constraints of manufacturing tolerances. The statistical data analysis is performed on the simulated results. The larger the better signal to noise quality characteristics is used to find the effect of control parameters in the data analysis. Taguchi analysis suggests dominant parameters, which affects the sensitivity of the FODS and causes immunity to noise. A source fiber inclination angle is chosen as an adjustment parameter. Other control parameters are used for fine tuning of the FODS design for achieving three qualities viz. best robustness, optimized sensitivity and robustness and best sensitivity.展开更多
The formation of the retroreflected light field is introduced in the paper and the components of the retroreflected light field are analyzed.Furthermore,a deep analysis of the factors affecting energy distribution of ...The formation of the retroreflected light field is introduced in the paper and the components of the retroreflected light field are analyzed.Furthermore,a deep analysis of the factors affecting energy distribution of the retroreflected light,such as design deviation,angle of incidence,was made.The simulation of the retroreflected light field was done.Recommendation is made in detail on both the energy distribution of the retroreflected light field at different working distances and the energy distribution of the retroreflected light field at a short distance when the diverging light comes.At last,two kinds of measuring instrument for the retroreflector are introduced,one is the long tunnel measuring instrument,the other is the minitype measuring instrument based on the character of the retroreflector when the diverging light comes.展开更多
The angle dependence of photonic crystals(PCs)dramatically limits their practical applications in the colorimetrical sensing of humidity and volatile organic compound(VOC)vapors.In addition,it is challenging for inver...The angle dependence of photonic crystals(PCs)dramatically limits their practical applications in the colorimetrical sensing of humidity and volatile organic compound(VOC)vapors.In addition,it is challenging for inverse opal PCs to colorimetrically distinguish between vapors with similar refractive indices.Different from the mechanism of PC-based sensors,here,we report an angle-independent polyacrylamide(PAAm)organogel structural color film based on the mechanisms of retroreflection,total internal reflection(TIR)and interference with a shape similar to a single-sided“egg waffle”.During the process of responding to humidity and VOC vapors,the color of the film remains angle-independent in the normal angle range of 0°to 45°under coaxial illumination and observation conditions.At the same time,the film can colorimetrically distinguish between vapors with similar refractive indices,such as methanol and ethanol,which is mainly due to the differences in their polarity and solubility parameters.The film shows good stability,reversibility and selectivity when exposed to vapors.A colorimetric sensor with a new response mechanism is proposed and has the potential to effectively distinguish between vapors with similar refractive indices.Furthermore,this responsive retroreflective structural color film(RRSCF)provides a universal strategy to develop targeted angle-independent structural color sensors by selecting optimized materials.展开更多
Metagratings(MGs)have emerged as a promising platform for manipulating the anomalous propagation of electromagnetic waves.However,traditional methods for designing functional MG-based devices face significant challeng...Metagratings(MGs)have emerged as a promising platform for manipulating the anomalous propagation of electromagnetic waves.However,traditional methods for designing functional MG-based devices face significant challenges,including complex model structures,time-consuming optimization processes,and specific polarization requirements.In this work,we propose an inverse-design approach to engineer simple MG structures comprising periodic air grooves on a flat metal surface,which can control anomalous reflection without polarization limitations.Through rigorous analytical methods,we derive solutions that achieve perfect retroreflection and perfect specular reflection,thereby leading to functional control over the linearly-polarized electromagnetic waves.Such capabilities enable intriguing functionalities including polarization-dependent retroreflection and polarization-independent retroreflection,as confirmed through fullwave simulations.Our work offers a simple and effective method to control freely electromagnetic waves,with potential applications spanning wavefront engineering,polarization splitting,cloaking technologies,and remote sensing.展开更多
The coefficients of retroreflection and chromaticity coordinates are critical metrics for determining the quality of a retroreflector.However,conventional retroreflection measurement techniques rely heavily on the nig...The coefficients of retroreflection and chromaticity coordinates are critical metrics for determining the quality of a retroreflector.However,conventional retroreflection measurement techniques rely heavily on the night-time colour,size and characteristics of thesample being measured.This complicates the measurement process and leads to deviations in the test results.In addition,chromaticitycannot be determined using this approach.Therefore,it is necessary to improve the measurement accuracy,simplify themeasurement process and achieve themeasurement of the traffic sign RA and chromaticity coordinates simultaneously.In this study,an improved method for retroreflector characterization using imaging was proposed.This allowed for the measurement of the coefficientsof retroreflection and the chromaticity coordinates simultaneously,and only a white standard sample was required for calibration.The primary components of the proposed system included a lighting projector,a receiver,two motorized rotational stages,a retroreflective sample holder and customized software that using scaling factors to convert a digital signal into sample retroreflectioncoefficients and retroreflective chromaticity coordinates.The experimental results indicated that the raw data output from thecamera exhibited a positive correlation relationship with the luminous flux from the surface of the retroreflector.The maximummeasurementerrors for the retroreflection and chromaticity were−12.2 cd/(lx·m2)and−2.09%,respectively.Thismethod was inexpensiveand convenient,used a commercially available digital camera,could help to identify defects in retroreflection and chromaticity forretroreflective sheeting and led to increased accessibility for the quality control of retroreflective sheeting.展开更多
Traffic signs often convey critical information to drivers. To ensure visibility in nighttime or low light conditions, traffic signs must be in compliance with the minimum retrore- flectivity standards outlined by the...Traffic signs often convey critical information to drivers. To ensure visibility in nighttime or low light conditions, traffic signs must be in compliance with the minimum retrore- flectivity standards outlined by the manual on uniform traffic control devices （MUTCD）. Among all of the assessment methods （visual nighttime inspection, retroreflectivity measurement） and management methods （expected life, blanket replacement, and control signs） outlined in the MUTCD, expected sign life has been the most selected by agencies for maintaining compliance. In current literature, little research exists with regard to schedule sign replacement, focusing rather on the current favorite predictor, sign age. However, after collecting data on 1683 in-service traffic signs across the state of Utah, this study primarily concluded that not only sign age, but other contributing factors affect sign retroreflective performance. Aiming to determine the effects of various damage forms on sign retroreflectivity, statistical methods, including regression models, chi-square test, t- test, and odds ratio were employed to analyze traffic sign data. At the conclusion, the strong association between damage and retroreflectivity compliance of traffic signs was evident. In addition, to identify more critical damage forms, the effects of various forms on traffic sign retroreflectivity were compared. These conclusions provide insight to inform transportation agencies in the development of sign management plans and schedule sign replacement.展开更多
Existing studies on horizontal sunshade systems mainly focus on the influence of the sunshade on the room under or inside the sunshade systems.Meanwhile,the top surface of horizontal sunshade,especially those with mir...Existing studies on horizontal sunshade systems mainly focus on the influence of the sunshade on the room under or inside the sunshade systems.Meanwhile,the top surface of horizontal sunshade,especially those with mirror surface or made of metal,reflects solar radiation into the indoor and surroundings,resulting in“secondary reflection”.This paper mainly focuses on the influence of secondary reflection on the room above the sunshade,using DesignBuilder software to conduct numerical simulation analysis and building architectural model for field measurement.Results from simulation and field measurement both prove that mirror materials increase secondary reflection reflected into the indoor.Moreover,results from experiments show that retroreflective materials decrease secondary reflection reflected into the indoor.At low latitude,the application of retroreflective materials on the top surface of horizontal sunshade effectively reduces the adverse influence of secondary reflection on the room above the sunshade.展开更多
This study addresses the critical safety issue of declining retroreflectivity values of road traffic signs,which can lead to unsafe driving conditions,especially at night.The paper aims to predict the retroreflectivit...This study addresses the critical safety issue of declining retroreflectivity values of road traffic signs,which can lead to unsafe driving conditions,especially at night.The paper aims to predict the retroreflectivity coefficient values of these signs and to classify their status as acceptable or rejected(in need of replacement)using machine learning models.Moreover,logistic regression and survival analysis are used to predict the median lifespans of road traffic signs across various geographical locations,focusing on signs in Croatia and Sweden as case studies.The results indicate high accuracy in the predictive models,with classification accuracy at 94%and an R2 value of 94%for regression analysis.A significant finding is that a considerable number of signs maintain acceptable retroreflectivity levels within their warranty period,suggesting the feasibility of extending maintenance checks and warranty periods to 15 years which is longer than the current standard of 10 years.Additionally,the study reveals notable variations in the median lifespans of signs based on color and location.Blue signs in Croatia and Sweden exhibit the longest median lifespans(28 to 35 years),whereas white signs in Sweden and red signs in Croatia show the shortest(16 and 10 years,respectively).The high accuracy of logistic regression models(72-90%)for lifespan prediction confirms the effectiveness of this approach.These findings provide valuable insights for road authorities regarding the maintenance and management of road traffic signs,enhancing road safety standards.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11804167,11804291,and 11904175)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20180739,BK20180740,and BK20180890)+2 种基金the Innovation Research Project of Jiangsu Province,China(Grant No.CZ0070619002)NJUPT-SF(Grant Nos.NY218128 and NY218135)NJUPT-STITP(Grant No.XYB2020301)。
文摘We investigate the electron retroreflection and the Klein tunneling across a graphene-based n-p-n junction irradiated by linearly polarized off-resonant light with the polarization along the x direction.The linearly polarized off-resonant light modifies the band structure of graphene,which leads to the anisotropy of band structure.By adjusting the linearly polarized light and the direction of n-p-n junction simultaneously,the electron retroreflection appears and the anomalous Klein tunneling,the perfect transmission at a nonzero incident angle regardless of the width and height of potential barrier,happens,which arises from the fact that the light-induced anisotropic band structure changes the relation of wavevector and velocity of electron.Our finding provides an alternative and flexible method to modulate electron retroreflection and Klein tunneling.
基金the National Key Research and Development Program of China(No.2018YFB1305005)。
文摘Passive optical motion capture technology is an effective mean to conduct high-precision pose estimation of small scenes of mobile robots;nevertheless,in the case of complex background and stray light interference in the scene,due to the infuence of target adhesion and environmental reflection,this technology cannot estimate the pose accurately.A passive binocular optical motion capture technology under complex illumination based on binocular camera and fixed retroreflective marker balls has been proposed.By fixing multiple hemispherical retrorefective marker balls on a rigid base,it uses binocular camera for depth estimation to obtain the fixed position relationship between the feature points.After performing unsupervised state estimation without manual operation,it overcomes the infuence of refection spots in the background.Meanwhile,contour extraction and ellipse least square fitting are used to extract the marker balls with incomplete shape as the feature points,so as to solve the problem of target adhesion in the scene.A FANUC m10i-a robot moving with 6-DOF is used for verification using the above methods in a complex lighting environment of a welding laboratory.The result shows that the average of absolute position errors is 5.793mm,the average of absolute rotation errors is 1.997°the average of relative position errors is 0.972 mm,and the average of relative rotation errors is 0.002°.Therefore,this technology meets the requirements of high-precision measurement in a complex lighting environment when estimating the 6-DOF-motion mobile robot and has very significant application prospects in complex scenes.
文摘Fiber optic displacement sensors are widely used in industry. Retro reflective fiber optic displacement sensor consists of parallel fibers with a reflector at a distance. Light is launched into the transmitting fiber which gets reflected by reflector. This reflected light is collected by the receiving fiber. The received light is function of the displacement of the reflector from the fiber end faces. This paper is targeted to obtain a robust design for the fiber optic displacement sensor (FODS) using well known Taguchi method. The design takes care of all noise parameters within constraints of manufacturing tolerances. The statistical data analysis is performed on the simulated results. The larger the better signal to noise quality characteristics is used to find the effect of control parameters in the data analysis. Taguchi analysis suggests dominant parameters, which affects the sensitivity of the FODS and causes immunity to noise. A source fiber inclination angle is chosen as an adjustment parameter. Other control parameters are used for fine tuning of the FODS design for achieving three qualities viz. best robustness, optimized sensitivity and robustness and best sensitivity.
文摘The formation of the retroreflected light field is introduced in the paper and the components of the retroreflected light field are analyzed.Furthermore,a deep analysis of the factors affecting energy distribution of the retroreflected light,such as design deviation,angle of incidence,was made.The simulation of the retroreflected light field was done.Recommendation is made in detail on both the energy distribution of the retroreflected light field at different working distances and the energy distribution of the retroreflected light field at a short distance when the diverging light comes.At last,two kinds of measuring instrument for the retroreflector are introduced,one is the long tunnel measuring instrument,the other is the minitype measuring instrument based on the character of the retroreflector when the diverging light comes.
基金supported by National Key Research and Development Program of China(Nos.2017YFA0204600,2018YFE0201701)National Natural Science Foundation of China(No.51673041).
文摘The angle dependence of photonic crystals(PCs)dramatically limits their practical applications in the colorimetrical sensing of humidity and volatile organic compound(VOC)vapors.In addition,it is challenging for inverse opal PCs to colorimetrically distinguish between vapors with similar refractive indices.Different from the mechanism of PC-based sensors,here,we report an angle-independent polyacrylamide(PAAm)organogel structural color film based on the mechanisms of retroreflection,total internal reflection(TIR)and interference with a shape similar to a single-sided“egg waffle”.During the process of responding to humidity and VOC vapors,the color of the film remains angle-independent in the normal angle range of 0°to 45°under coaxial illumination and observation conditions.At the same time,the film can colorimetrically distinguish between vapors with similar refractive indices,such as methanol and ethanol,which is mainly due to the differences in their polarity and solubility parameters.The film shows good stability,reversibility and selectivity when exposed to vapors.A colorimetric sensor with a new response mechanism is proposed and has the potential to effectively distinguish between vapors with similar refractive indices.Furthermore,this responsive retroreflective structural color film(RRSCF)provides a universal strategy to develop targeted angle-independent structural color sensors by selecting optimized materials.
基金supported by the National Natural Science Foundation of China(No.12274225)the Natural Science Foundation of Jiangsu Province(No.BK20230089)+1 种基金the Science and Technology Plan Special Foundation of Jiangsu Province(No.ZAG23009)the Fundamental Research Funds for the Central Universities(Nos.NE2022007 and NS2023056).
文摘Metagratings(MGs)have emerged as a promising platform for manipulating the anomalous propagation of electromagnetic waves.However,traditional methods for designing functional MG-based devices face significant challenges,including complex model structures,time-consuming optimization processes,and specific polarization requirements.In this work,we propose an inverse-design approach to engineer simple MG structures comprising periodic air grooves on a flat metal surface,which can control anomalous reflection without polarization limitations.Through rigorous analytical methods,we derive solutions that achieve perfect retroreflection and perfect specular reflection,thereby leading to functional control over the linearly-polarized electromagnetic waves.Such capabilities enable intriguing functionalities including polarization-dependent retroreflection and polarization-independent retroreflection,as confirmed through fullwave simulations.Our work offers a simple and effective method to control freely electromagnetic waves,with potential applications spanning wavefront engineering,polarization splitting,cloaking technologies,and remote sensing.
基金funded by the Central Public-Interest Scientific Institution Basal Research Fund(Grant Nos.2020–9021 and 2021–9021b)the National Key Research and Development Program of China(Grant No.2021YFF0600205).
文摘The coefficients of retroreflection and chromaticity coordinates are critical metrics for determining the quality of a retroreflector.However,conventional retroreflection measurement techniques rely heavily on the night-time colour,size and characteristics of thesample being measured.This complicates the measurement process and leads to deviations in the test results.In addition,chromaticitycannot be determined using this approach.Therefore,it is necessary to improve the measurement accuracy,simplify themeasurement process and achieve themeasurement of the traffic sign RA and chromaticity coordinates simultaneously.In this study,an improved method for retroreflector characterization using imaging was proposed.This allowed for the measurement of the coefficientsof retroreflection and the chromaticity coordinates simultaneously,and only a white standard sample was required for calibration.The primary components of the proposed system included a lighting projector,a receiver,two motorized rotational stages,a retroreflective sample holder and customized software that using scaling factors to convert a digital signal into sample retroreflectioncoefficients and retroreflective chromaticity coordinates.The experimental results indicated that the raw data output from thecamera exhibited a positive correlation relationship with the luminous flux from the surface of the retroreflector.The maximummeasurementerrors for the retroreflection and chromaticity were−12.2 cd/(lx·m2)and−2.09%,respectively.Thismethod was inexpensiveand convenient,used a commercially available digital camera,could help to identify defects in retroreflection and chromaticity forretroreflective sheeting and led to increased accessibility for the quality control of retroreflective sheeting.
文摘Traffic signs often convey critical information to drivers. To ensure visibility in nighttime or low light conditions, traffic signs must be in compliance with the minimum retrore- flectivity standards outlined by the manual on uniform traffic control devices （MUTCD）. Among all of the assessment methods （visual nighttime inspection, retroreflectivity measurement） and management methods （expected life, blanket replacement, and control signs） outlined in the MUTCD, expected sign life has been the most selected by agencies for maintaining compliance. In current literature, little research exists with regard to schedule sign replacement, focusing rather on the current favorite predictor, sign age. However, after collecting data on 1683 in-service traffic signs across the state of Utah, this study primarily concluded that not only sign age, but other contributing factors affect sign retroreflective performance. Aiming to determine the effects of various damage forms on sign retroreflectivity, statistical methods, including regression models, chi-square test, t- test, and odds ratio were employed to analyze traffic sign data. At the conclusion, the strong association between damage and retroreflectivity compliance of traffic signs was evident. In addition, to identify more critical damage forms, the effects of various forms on traffic sign retroreflectivity were compared. These conclusions provide insight to inform transportation agencies in the development of sign management plans and schedule sign replacement.
基金supported by Guangdong Provincial Science Foundation Project(2022A1515011298)Collaborative Education Project of Industry-University Cooperation of the Ministry of Education(202102067007)National Social Science Fund of China(20BZJ026).Gratitude should also be extended to Yu Dufeng.
文摘Existing studies on horizontal sunshade systems mainly focus on the influence of the sunshade on the room under or inside the sunshade systems.Meanwhile,the top surface of horizontal sunshade,especially those with mirror surface or made of metal,reflects solar radiation into the indoor and surroundings,resulting in“secondary reflection”.This paper mainly focuses on the influence of secondary reflection on the room above the sunshade,using DesignBuilder software to conduct numerical simulation analysis and building architectural model for field measurement.Results from simulation and field measurement both prove that mirror materials increase secondary reflection reflected into the indoor.Moreover,results from experiments show that retroreflective materials decrease secondary reflection reflected into the indoor.At low latitude,the application of retroreflective materials on the top surface of horizontal sunshade effectively reduces the adverse influence of secondary reflection on the room above the sunshade.
文摘This study addresses the critical safety issue of declining retroreflectivity values of road traffic signs,which can lead to unsafe driving conditions,especially at night.The paper aims to predict the retroreflectivity coefficient values of these signs and to classify their status as acceptable or rejected(in need of replacement)using machine learning models.Moreover,logistic regression and survival analysis are used to predict the median lifespans of road traffic signs across various geographical locations,focusing on signs in Croatia and Sweden as case studies.The results indicate high accuracy in the predictive models,with classification accuracy at 94%and an R2 value of 94%for regression analysis.A significant finding is that a considerable number of signs maintain acceptable retroreflectivity levels within their warranty period,suggesting the feasibility of extending maintenance checks and warranty periods to 15 years which is longer than the current standard of 10 years.Additionally,the study reveals notable variations in the median lifespans of signs based on color and location.Blue signs in Croatia and Sweden exhibit the longest median lifespans(28 to 35 years),whereas white signs in Sweden and red signs in Croatia show the shortest(16 and 10 years,respectively).The high accuracy of logistic regression models(72-90%)for lifespan prediction confirms the effectiveness of this approach.These findings provide valuable insights for road authorities regarding the maintenance and management of road traffic signs,enhancing road safety standards.
