Study on the influence of retroreflective materials on the“secondary reflection”on the room above the horizontal sunshade

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.

Angle-independent responsive organogel retroreflective structural color film for colorimetric sensing of humidity and organic vapors

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.

Retro-Reflective Fiber Optic Displacement Sensor for Performance Optimization Using Taguchi Method

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.

Light-modulated electron retroreflection and Klein tunneling in a graphene-based n-p-n junction

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.

Establishment of a metric to characterize retroreflector properties using a consumer-grade colour camera

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.

The effects of damage on sign visibility:An assist in traffic sign replacement

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.