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"Light reflection"
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Reflecting light
\"This book looks at what reflections are and how we can use them. - Mirrors reflect light back at exactly the same angle. You can make a \"mirror book\" to explore symmetry and multiple reflections. - Why does a straight straw look bent in a glass of water? Experiment using air, oil, and water to see how different materials affect the speed of light. - Look at how our eyes use reflected light to see and make a pinhole camera to show how the eye works. And much more!\"-
Book
Evaluation of Color and Spectral Behavior of a Novel Flowable Resin Composite after Water Aging: An In Vitro Study
Background: This study aimed to evaluate the color matching, light transmittance, and reflectance characteristics of the novel flowable resin composite OCF-001 (OCF). Methods: Fifty-four resin composite molds were made with simulated class I cavities of A2, A3, and A4 shades by filling the rubber mold interspace with Estelite Sigma Quick (ESQ), Gracefil Putty (GP) and Filtek Supremme Ultra (FSU). After applying the adhesive, three different flowable resin composites (n = 6), OCF, Gracefil LoFlo (GLF), and Supreme Ultra Flowable (SUF), were used to fill the cavities. A colorimeter was used to measure the color parameters (CIEDE2000). The color measurements were taken immediately and after 28 days. Data were analyzed using the nonparametric Kruskal–Wallis (α = 0.05) and Wilcoxon tests. The light transmittance and reflection characteristics were measured with a black background using a spectrophotometer under D65 illumination. Results: The ΔE00, and ΔC of OCF was lower than other tested materials in A2 and A3 shades both immediately and after 28 days. OCF showed the highest transmittance characteristic, and a relatively stable reflectance curve in all the wavelengths. Conclusions: OCF showed better shade matching with the surrounding shades of A2 and A3, a relative uniform reflectance and higher light transmission properties.
Journal Article
What are shadows and reflections?
\"What happens when light is blocked? How can we redirect light? Readers will discover the answers to these questions and more in this fact-filled title. Readers will explore the properties of transparent, translucent, opaque, and reflective materials, and learn how to redirect light beams and create shadows\"-- Provided by publisher.
Book
Mobile anchor node assisted node collaborative localization based on light reflection in WSN
Real-time and accurate location detection is a key link to ensure the safety of operating machines and workers in production and life. Compared with traditional static multi-anchor nodes, mobile anchor node assisted localization is greener and more energy-saving. In this paper, we first propose a static trajectory based on a light reflection model. Compared with other static models, this model has fewer times in the field, overcomes the collinearity problem and uniform beacon distribution, and ensures that all sensor nodes can receive good enough beacon quality for localization. Secondly, an RSSI-based improved weighted centroid localization algorithm and an RSSI-based improved weighted centroid collaborative localization algorithm are proposed. The two-strategy optimal location beacon set screening method is used to reduce location misjudgment. In order to improve the accuracy of centroid localization, a weighted centroid localization algorithm based on distance and hop number is designed. Moreover, a collaborative localization strategy is aiming at improving beacon density. Experimental results show that both the algorithm and static trajectory can guarantee better beacon coverage rate and localization success rate under different experimental conditions, and at the same time have higher accuracy.
Journal Article
Reliable and broad-range layer identification of Au-assisted exfoliated large area MoS2 and WS2 using reflection spectroscopic fingerprints
The emerging Au-assisted exfoliation technique enables the production of a wealth of large-area and high-quality ultrathin two dimensional (2D) crystals. Fast, damage-free, and reliable determination of the layer number of such 2D films can greatly promote layer-dependent physical studies and device applications. Here, an optical method has been developed for simple, high throughput, and accurate determination of the layer number for Au-assisted exfoliated MoS
2
and WS
2
films in a broad thickness range. The method is based on quantitative analysis of layer-dependent white light reflection spectra (WLRS), revealing that the intensity of exciton-induced reflection peaks can be used as a clear indicator for identifying the layer number. The simple yet robust method will facilitate fundamental studies on layer-dependent optical, electrical, and thermal properties and device applications of 2D materials. The technique can also be readily combined with photoluminescence (PL) and Raman spectroscopies to study other layer-dependent physical properties of 2D materials.
Journal Article
Temperature-Dependent Circularly Polarized Luminescence of a Cholesteric Copolymer Doped with a Europium Complex
The design of new materials for non-contact temperature sensors is an important task for scientists working in the fields of chemistry, physics, and materials science. In the present paper, a novel cholesteric mixture based on a copolymer doped with a highly luminescent europium complex was prepared and studied. It was found that the spectral position of the selective reflection peak strongly depends on temperature and a shift towards shorter wavelengths is observed upon heating with an amplitude of more than 70 nm, from the red to green spectral range. This shift is associated with the existence and melting of clusters of smectic order, as confirmed by X-ray diffraction investigations. The extreme temperature dependence of the wavelength of selective light reflection provides a high thermosensitivity of the degree of circular polarization of the europium complex emission. The highest values of the dissymmetry factor are observed when the peak of selective light reflection fully overlaps with the emission peak. As a result, the highest sensitivity of 65%/K for luminescent thermometry materials was obtained. In addition, the ability of the prepared mixture to form stable coatings was demonstrated. The obtained experimental results, i.e., the high thermosensitivity of the degree of circular polarization, and the ability to form stable coatings allow us to consider the prepared mixture as a promising material for luminescent thermometry.
Journal Article
Concomitant Thermochromic and Phase‐Change Effect in a Switchable Spin Crossover Material for Efficient Passive Control of Day and Night Temperature Fluctuations
The increasing environmental protection demand has prompted the development of passive thermal regulation systems that reduce temperature fluctuations in buildings. Here, it is demonstrated that the heat generated by the sun can trigger a spin crossover (SCO) in a molecule‐base material, resulting in a concomitant color variation (from pink to white) and a phase transition. This leads to a cooling effect with respect to other thermochromic materials. In addition, when the material is cooled, a dampening of the temperature decrease is produced. Therefore, these materials can potentially be implemented for passive temperature control in buildings. Furthermore, SCO materials are remarkably stable upon cycling and highly versatile, which allows for the design of compounds with properties tailored for the desired climatic conditions and comfortable temperature. The heat produced by the sun can induce a spin transition in a spin‐crossover material, leading to a color change coupled with the absorption/release of energy, which results in a cooling effect at high temperatures and a dampening of the temperature decrease at low temperatures. Hence, these materials can potentially be applied for passive temperature control in buildings.
Journal Article
Diesel Adulteration Detection with a Machine Learning-Enhanced Laser Sensor Approach
This paper introduces a novel and cost-effective method for detecting adulterated diesel, specifically targeting contamination with kerosene, by leveraging machine learning and the refractive index values of mixed diesel samples. It proposes a laser-based sensor, employing COMSOL simulations for synthetic data generation to facilitate machine learning training. This innovative approach not only streamlines the detection process by eliminating the need for expensive equipment and specialized personnel but also enables on-site testing without extensive sample preparation. The sensor’s design, utilizing light refraction and reflection principles, allows for the accurate measurement of diesel adulteration levels. Validation results showcase the machine learning models’ high precision in predicting adulteration percentages, as evidenced by an R-squared value of 0.999 and a mean absolute error of 0.074. This research signifies a leap in sensor technology, offering a practical solution for rapid diesel adulteration detection, especially in developing countries, by minimizing reliance on advanced laboratory analyses. The sensor’s design aligns with the requirements for low-cost IoT technology, presenting a versatile tool for various applications.
Journal Article
Design and Analysis of Nano-Structured Gratings for Conversion Efficiency Improvement in GaAs Solar Cells
This paper presents the design and analysis of nano-structured gratings to improve the conversion efficiency in GaAs solar cells by reducing the light reflection losses. A finite-difference time domain (FDTD) simulation tool is used to design and simulate the light reflection losses of the subwavelength grating (SWG) structure in GaAs solar cells. The SWG structures perform as an excellent alternative antireflective (AR) coating due to their capacity to reduce the reflection losses in GaAs solar cells. It allows the gradual change in the refractive index that confirms an excellent AR and the light trapping properties, when compared with the planar thin film structures. The nano-rod structure performs as a single layer AR coating, whereas the triangular (i.e., conical or perfect cone) and parabolic (i.e., trapezoidal/truncated cone) shaped nano-grating structures perform as a multilayer AR coating. The simulation results confirm that the reflection loss of triangular-shaped nano-grating structures having a 300-nm grating height and a 830-nm period is about 2%, which is about 28% less than the flat type substrates. It also found that the intermediate (i.e., trapezoidal and parabolic)-shaped structures, the light reflection loss is lower than the rectangular shaped nano-grating structure, but higher than the triangular shaped nano-grating structure. This analysis confirmed that the triangular shaped nano-gratings are an excellent alternative AR coating for conversion efficiency improvement in GaAs solar cells.
Journal Article
Modelling and Analysis of Vector and Vector Vortex Beams Reflection for Optical Sensing
Light Detection and Ranging (LiDAR) sensors can precisely determine object distances using the pulsed time of flight (TOF) or amplitude-modulated continuous wave (AMCW) TOF methods and velocity using the frequency-modulated continuous wave (FMCW) approach. In this paper, we focus on modelling and analysing the reflection of vector beams (VBs) and vector vortex beams (VVBs) for optical sensing in LiDAR applications. Unlike traditional TOF and FMCW methods, this novel approach uses VBs and VVBs as detection signals to measure the orientation of reflecting surfaces. A key component of this sensing scheme is understanding the relationship between the characteristics of the reflected optical fields and the orientation of the reflecting surface. To this end, we develop a computational model for the reflection of VBs and VVBs. This model allows us to investigate critical aspects of the reflected field, such as intensity distribution, intensity centroid offset, reflectance, and the variation of the intensity range measured along the azimuthal direction. By thoroughly analysing these characteristics, we aim to enhance the functionality of LiDAR sensors in detecting the orientation of reflecting surfaces.
Journal Article