Reflectance Curves Research Articles

Research on the deep learning-based exposure invariant spectral reconstruction method.

The surface spectral reflectance of an object is the key factor for high-fidelity color reproduction and material analysis, and spectral acquisition is the basis of its applications. Based on the theoretical imaging model of a digital camera, the spectral reflectance of any pixels in the image can be obtained through spectral reconstruction technology. This technology can avoid the application limitations of spectral cameras in open scenarios and obtain high spatial resolution multispectral images. However, the current spectral reconstruction algorithms are sensitive to the exposure variant of the test images. That is, when the exposure of the test image is different from that of the training image, the reconstructed spectral curve of the test object will deviate from the real spectral to varying degrees, which will lead to the spectral data of the target object being accurately reconstructed. This article proposes an optimized method for spectral reconstruction based on data augmentation and attention mechanisms using the current deep learning-based spectral reconstruction framework. The proposed method is exposure invariant and will adapt to the open environment in which the light is easily changed and the illumination is non-uniform. Thus, the robustness and reconstruction accuracy of the spectral reconstruction model in practical applications are improved. The experiments show that the proposed method can accurately reconstruct the shape of the spectral reflectance curve of the test object under different test exposure levels. And the spectral reconstruction error of our method at different exposure levels is significantly lower than that of the existing methods, which verifies the proposed method's effectiveness and superiority.

Polyethylene Glycol (PEG) Non-Ionic Surfactant-Based Reverse Micellar Dyeing of Cotton Fabric with Hot Type Trichloropyrimidine (TCP)-Based Reactive Dyes

ABSTRACT This work aims to examine the feasibility of using poly(ethylene glycol) (PEG)-based reverse micellar dyeing system for dyeing cotton fabric with the use of hot type trichloropyrimidine (TCP)-based reactive dyes and to evaluate the possibility of saving the dyeing energy used during the dyeing process. Experimental results show that fabrics dyed in reverse micellar system at 90°C can achieve higher color yield than the conventional water-based system at the same temperature. Further experiments using reverse micellar system for dyeing cotton at 80°C (a reduction of working temperature of 10°C) provided color yield comparable to that of conventional water-based system except the use of yellow dye. Both water-dyed and octane-dyed samples had good to excellent levelness, washing and rubbing fastness and 98.5% of octane could be recycled after distillation. Reflectance curves were identical in shape and the SEM images showed neither of the dyeing systems caused any significant damage to cotton fibers. These findings validated the possibility of using reverse micellar dyeing system for hot type TCP-based reactive dyeing of cotton fabrics at lower coloration temperature and energy consumption.

Identification of key altered/weathered minerals near to the base metal mineral in Jahazpur, India using AVIRIS-NG data

Hydrothermally altered minerals are invariably associated with base metal mineralization. The narrow spectral resolution of Airborne Visible/Infrared Imaging spectrometer -Next Generation (AVIRIS-NG) facilitates the identification and mapping of altered minerals. Spectral angle mapper (SAM) of supervised classification technique was applied on AVIRIS-NG reflectance data for identifying and mapping altered minerals such as talc, kaolinite, soapstone, kaosmec, and montmorillonite. The identified minerals were verified during the ground-truthing survey and, lab generated spectral reflectance curve confirms the presence of minerals. During the field survey, the surface signature of base metal mineralisation was found in the form of malachite stains in the carbonaceous phyllite lithologic unit. Conventional geological technique such as transmitted light petrography and X-ray diffraction analysis confirms the occurrence of base metal mineralization in the area. Therefore, this study justified the delineation of hydrothermally altered zones using AVIRIS-NG hyperspectral data and their validation through lab-generated spectra, petrography, and X-ray diffraction analysis.

High Performance Bimetallic(Cu-Co) Surface Plasmon Resonance Sensor using Hybrid Configuration of 2D Materials

The performance of prism-based surface plasmon resonance sensor utilizing kretschmann configuration composed of thin metallic (Cu–Co) film coated with 2D material such as BP/Graphene layer is investigated theoretically based on angular interrogation method. It is observed that optimizing the thickness of bimetallic (Cu–Co) and BP/Graphene layers, the sensitivity of the sensor improved greatly and still can maintain its minimum reflectivity and line width of the SPR reflectivity curve. We also observed that addition of BP/ Graphene over the bimetallic layer, its further enhanced the sensitivity. Numerical results shows that sensitivity as high as 504deg/RIU is achieved for the well optimized bimetallic configuration consist of 45nm of Cu and 10nm of Co thickness for the analyte refractive indices ranging from 1.330 - 1.335.

Exploitation of SnO2/Polypyrrole Interface for Detection of Ammonia Vapors Using Conductometric and Optical Techniques: A Theoretical and Experimental Analysis.

This study describes the construction of a lab-built Surface Plasmon Resonance (SPR) system for gas sensing applications employing a highly sensitive and trustworthy optical approach. The nanocomposite thin film of tin oxide (SnO2) and Polypyrrole (PPy) were prepared for sensing highly toxic gas, i.e., ammonia (NH3) gas. The gas sensor was validated by both optical and conductometric techniques of gas sensing. The optical SPR gas sensor is based on the change in refractive index at the SnO2/Polypyrrole (PPy) interface with gas adsorption (NH3). The thickness of SnO2 and Polypyrrole thin films was optimised using theoretical calculations for a sharp SPR reflectance curve. The manuscript also offers theoretical SPR curves for different PPy and SnO2 layer thicknesses. To support the theoretical conclusions, the effects of NH3 gas on the prism/Au/SnO2/Polypyrrole system were also investigated experimentally. In comparison to other research described in the literature, it was observed that the constructed sensor’s sensitivity was higher. The obtained results demonstrate the utility of the SPR setup in the investigation of the interactions of adhered gas molecules with dielectrics and gas sensing. For conductometric gas sensing studies, the film having optimised thicknesses for sharp SPR reflectance curves was separately prepared on Interdigitated Electrodes. At a low working temperature of roughly 150 °C, the sensing response of the constructed film was observed and found to be maximal (60).

Unravelling the mystery of red flowers in the Mediterranean Basin: How to be conspicuous in a place dominated by hymenopteran pollinators

Abstract Red‐flowered species have traditionally been related to ornithophily, and the ‘bee avoidance’ hypothesis, that is, red flower colouration is a way to reduce visits from hymenopterans, has been proposed to explain this association. In the Mediterranean Basin, ornithophily is almost absent, and hymenopterans are the most common group of pollinators. The fact that hymenopterans are virtually red‐blind raises the question of how red‐flowered species are pollinated in this region. Are these flowers pollinated by other groups of red‐sensitive insects such as lepidopterans and coleopterans, or do they have visual cues that make them attractive to hymenopterans? We examined the reflectance spectra of 51 red‐flowered species from the Mediterranean Basin and modelled these spectra in the visual system of hymenopterans, dipterans, coleopterans and lepidopterans to obtain colour and conspicuousness. According to their reflectance curves, species were classified as pure red and UV‐red flowers, and the presence of more than one flower colour (patterned flowers) was studied. We evaluated the match between flower reflectance spectra and the maximum discrimination abilities of hymenopteran and lepidopteran visual system. All these metrics were analysed in a phylogenetically explicit framework, and a literature review of potential pollinators was performed. The vast majority of red‐flowered species in the Mediterranean Basin are potentially pollinated by hymenopterans, and only three species are exclusively visited by coleopterans. We found that 90% of these species showed at least one colour signal strategy that helps to enhance conspicuousness to hymenopterans: to produce UV‐red flower type spectra and/or patterned flowers. The UV‐red colour showed a significant phylogenetic signal, but the presence of patterned flowers did not. Even though the red‐flowered species of the Mediterranean Basin did not optimally match the colour vision of hymenopterans or lepidopterans, the presence of patterned and UV‐red colours suggests an improvement in detection and discrimination by hymenopterans. The bee‐avoidance hypothesis seems to be ruled out for the red‐flowered species of the Mediterranean Basin. Our results suggest that red‐flowered species are mostly pollinated by hymenopterans and show different flower colour signal strategies that can be interpreted as signs of adaptation to these pollinators. Read the free Plain Language Summary for this article on the Journal blog.

Analysis of the Albanian Economy through the IS-LM Model

The objective of the study is the analysis of IS-LM curves. The aim is to prove that the current theoretical models of IS-LM are not applicable in the Albanian economy. In this paper, the theoretical IS-LM model is analyzed according to the balance of I = S (investment - savings), and AE = Y (aggregate expenditure - gross domestic product). The models I + G = S + T and NX = NFI are not analyzed in this study. Two representative models were obtained, by the authors Hicks - Hansen and Dornbusch - Fischer - Startz. The theoretical and practical aspects of the application of the models are analyzed. The defect of the Dornbusch-Fischer-Startz model and the impossibility of applying it to the data of the Albanian economy is evident. The authors have proposed an improvement of the Hicks-Hansen model for the IS curve because the theoretical model is not applicable. They have replaced the half where Investment equals Savings with a reflection curve of the opportunity cost. This has made the model effective. In the analysis, two of the features of the Albanian economy were taken into consideration: the structure of the currency market where half of it is covered by foreign currency (euro and dollar), and the informal economy that affects the exchange rates and the effectiveness of the policies of the Bank of Albania. In the material, it is found that the transmission effect of the monetary policies implemented by the Bank of Albania is missing. There are weak connections between the rate of REPOs, monetary aggregates and some of the macroeconomic indicators. The rate of inflation and the rate of REPOs are strongly related to the first direction. Recommended; to apply the IS model according to the proposal made by the authors, to realize the de-euroization of the market, to change the objective of the Central Bank, putting as the main objective the preservation of the exchange rate of All in function of economic growth and financial stability. In the analysis, the method of comparison, description, analytical methods and statistical methods are used. Used Data is from INSTAT and the Central Bank of Albania.
 
 Received: 18 July 2022 / Accepted: 25 August 2022 / Published: 2 September 2022

A Simple Wide-Angular Scanning Phased Array With Wideband Filtering Response

This article presents a low-profile planar phased array with improved reflection (wideband filtering response) and radiation (wide-angular scan) performance. On one hand, the filtering response with harmonic suppression is integrated into the design of the single-layer array element without extra filtering resonators, such as external filters. As a result, the designed array possesses a reflection bandwidth of 4.6–5.3 GHz and two radiation nulls at either the upper or lower band edge of the reflection curve. On the other hand, inspired by the wide-beam radiation of a circular patch loaded with parasitic monopoles, the proposed array is able to realize its beam scanning coverage of −60°–+60° with low sidelobe levels (SLLs) in its E-plane. The reflection and radiation properties are validated by full-wave simulation and measurement of an eight-element array prototype. The filtering and low-SLL performance benefit for the array to avoid out-of-band interferences and in-band ones from other directions when it scans in a wide-angular area.

Produce feldspar mineral map using Spectral Angle Mapper (SAM) technique by hyperspectral image analysis

The analysis of the hyperspectral image is an important method used in mineral detection. A map of the Feldspar mineral will produced for the study area, which lies to the west of the holy province of Karbala and limited in image that download from USGS website (type hyperspectral image from EO-1 satellite) , by using Spectral Angle Mapper (SAM) technique in the Erdas software, which is based on calculating the spectral reflection curve of any point on the image and the spectral reflection curve of feldspar mineral that is available in the spectral library of the software. For the purpose of verifying the results of the image analysis, ground truth ( field work ) was used by collecting 12 soil samples and finding the spectral curve for each sample by the spectral analysis device (ASD) and the result show the match between image and ground, where produced Feldspar mineral map.

Surface plasmon resonance assisted optical characterization of nickel ion solution and nanocrystalline cellulose-graphene oxide thin film for sensitivity enhancement analysis

In this research, optical characterization of nickel ion solution and nanocrystalline cellulose-graphene oxide (NCC-GO) thin film has been carried out using surface plasmon resonance (SPR). The SPR experiments were carried out using bare gold thin film, in contact with deionized water and nickel ion at different concentrations, followed by the gold/NCC-GO system. Excellent agreement between the theoretical and experimental curves was observed where the real part (n) and the imaginary part (k) of the refractive index (ń) for gold thin film was n˜=0.2165+i3.8122. For nickel ion solution, the n value was similar with deionized water, i.e. 1.3333. Fitting the reflectance curves of gold/NCC-GO system revealed that ń for the NCC-GO thin film was n˜=1.4240+i0.0220. The analysis also showed the NCC-GO contributes to the sensitivity enhancement of SPR towards nickel ion sensing with a sensitivity of 10.8227°/RIU.

Z-type Bi0–BiOCl/WO3 heterojunction photocatalyst with SPR effect enhanced photocatalytic activity for the degradation of ciprofloxacin under visible light

A novel Bi0–BiOCl/WO3 Z-type heterojunction photocatalyst was successfully prepared by the solvothermal in-situ reduction method. The material composition, crystal structure, micro morphology and photocatalytic performance of the catalysts were studied. With ciprofloxacin as the target degradation product, the photocatalytic activity of the composite catalyst was significantly higher than that of the monomer catalyst under visible light irradiation. The characterization results show that the formation of Z-type heterojunction and surface plasmon resonance (SPR) effect enhance the visible light absorption of the catalyst, accelerates the electron transfer, reduces the recombination rate of electron-hole pairs, and thus improves the photocatalytic activity. In addition, Bi0-BOC/WO3 has a larger specific surface area than BiOCl and WO3 and can provide more active sites. Combined with UV–vis diffuse reflection and Mott Schottky curve, a possible electron transfer mechanism of Z-type heterojunction in accordance with Bi0-BOC/WO3 system is proposed. This provides a research idea for antibiotic wastewater treatment.

GenX 3: the latest generation of an established tool.

Since its publication more than 15 years ago the GenX software has been continuously developed and has established itself as a standard package for analyzing X-ray and neutron reflectometry data. The evolution of the software during the last two major revisions is reported here. This includes a simplified model builder for beginners, simple samples, additional sample models, statistical error analysis and the use of just-in-time compilation modules for the reflectometry kernel to achieve higher performance. In addition, the influence of experimental errors on the reflectivity curve is discussed, and new features are described that allow the user to include these in the error statistics to improve the fitting and uncertainty estimation.

Investigation of ultrasonic soft tissue-bone reflection coefficients correlating with curve severity in children with adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional curvature of spine. Children with AIS and low bone quality have higher chance to get curve progression leading to bigger spinal curvature. In addition, bone quality affects acoustic impedance of bone, thus influencing the reflection coefficient of ultrasound signal from the soft tissue–bone interface. This study aimed to estimate the bone quality of AIS patients based on the reflection coefficients to determine the correlation of the bone quality with curve severity. A simple bone model was used to develop an equation to calculate the reflection coefficient value. Experiments were conducted on five different phantoms. Acrylic was used to design a vertebral shape to study the effect of surface roughness and inclination, including: smooth flat surface (SFS), smooth curved surface (SCS), rough curved surface (RCS), and the rough curved inclined surface (RCIS). A clinical study with 37 AIS patients were recruited. The estimated reflection coefficient values of plate phantoms agreed well with the predicted values and the maximum error was 6.7%. The reflection coefficients measured from the acrylic-water interface for the SFS, SCS, RCS, RCIS (3° and 5°) were 0.37, 0.33, 0.28, (0.23 and 0.12), respectively. The surface roughness and inclination increased the reflection loss. From the clinical data, the average reflection coefficients for children with AIS were 0.11 and 0.07 for the mild curve group and the moderate curve group, respectively. A moderate linear correlation was found between the reflection coefficients and curve severity ( = 0.3). Patients with lower bone quality have observed to have larger spinal curvature.

Electric field-induced assembly of magnetic nanoparticles from dielectric ferrofluids on planar interface

Electric fields, similar to magnetic fields, could be the driving force inducing the assembling of magnetic nanoparticles at the interface. Using specular neutron reflectometry, the assembly of superparamagnetic nanoparticles of a dilute classical ferrofluid (magnetite coated with oleic acid in transformer oil) on the planar surface of a metal electrode (copper) was observed when an out-of-plane electric field was applied to the interface. Starting only from the wetting layer of magnetic nanoparticles on the electrode surface in the absence of an electric field, the evolution of the interface structure with an increase in the electric field strength is traced by analyzing changes in the scattering length density depth profiles derived from neutron reflectivity curves. At a sufficiently strong electric field, a second adsorption layer is revealed, which becomes even more saturated than the initial one. The cause of the observed effects is related to the polarization of the particles in the electric field and their interaction as dipoles. Relaxation measurements (after the field is switched off) prove that the local electric field induced by strongly interacting electric dipoles in concentrated adsorption layers is an important feature determining the enhancement of adsorption of nanoparticles.

A Self-Color-Changing Film with Periodic Nanostructure for Anti-Counterfeit Application

A self-color-changing film aimed at enhanced security and anti-counterfeit packaging is presented. Its function is to change color automatically when flipped under visible light. It is low-cost, takes a few seconds to check by the naked eye, and does not need any special tools to evaluate. The design of the color-changing, anti-counterfeiting film is based on a frequency-selective surface (FSS). The film is designed with aluminum nanocubes. They are laid out as an array in a plane with equal distance from one another. This arrangement allows us to select certain wavelengths of light to pass through by the size of the cubes and the separation distance between them. The performance is evaluated by a finite element analysis (FEA) method. The results show that the intersection of transmittance and the reflectance curves cause the film to change its color automatically when flipped. We also propose a method to predict the color of the film based on the transmittance values. The accuracy of this method is verified by actual colors from experiments with an error of no more than 12.8%, analyzed by the CIE chromaticity diagram.

APPLICATION OF MULTISPECTRAL IMAGES TO SEARCH FOR CONSTRUCTION OBJECTS ON THE SPECTRAL SIGNATURES BASE

The work is devoted to the study of Landsat-8 multispectral images of not high resolution using the spectral angle method on the base of spectral signatures libraries to detect objects under construction in an urban area. The physical basis of the research method is that all objects have different reflection coefficients depending on the wavelength. This property makes it possible to identify various substances by their spectral signatures. In the work, an automatic comparison of the curves of the spectral reflectivity of objects on a low resolution space multispectral image was made to identify the identity of the characteristic energy absorption and reflection zones for detecting objects in the construction process. The article also describes the stages of image preprocessing, cross-track illumination correction of the image, atmospheric correction, and mathematical operations of bands transformation, which provide more opportunities for analysis and recognition of objects using a spectral study of a space image. The study accurately determines the presence or absence of the desired materials, since the search is based on the molecular structure of the substance. Also, the use of multispectral images allows you to analyze the entire city at the same time. The initial data was taken from a 2021 Landsat-8 satellite image with 11 bands, with a resolution of 30 meters, which was enhanced to 15 meters during pre-processing. The results of the search and detection of objects under construction in the city are given. The detection results can be used as input data for further in-depth analysis.

A new model to describe small-angle neutron scattering from foams.

The modelling of scattering data from foams is very challenging due to the complex structure of foams and is therefore often reduced to the fitting of single peak positions or feature mimicking. This article presents a more elaborate model to describe the small-angle neutron scattering (SANS) data from foams. The model takes into account the geometry of the foam bubbles and is based on an incoherent superposition of the reflectivity curves arising from the foam films and the small-angle scattering (SAS) contribution from the plateau borders. The model is capable of describing the complete scattering curve of a foam stabilized by the standard cationic surfactant tetradecyltrimethylammonium bromide (C14TAB) with different water contents, i.e. different drainage states, and provides information on the thickness distribution of liquid films inside the foam. The mean film thickness decreases with decreasing water content because of drainage, from 28 to 22 nm, while the polydispersity increases. These results are in good agreement with the film thicknesses of individual horizontal foam films studied with a thin-film pressure balance.

Spectral analysis of soils in the lower course of the Acaraú River, Northeastern Brazil

The objective of this research was to analyze the spectral response of alluvial soils, representative of the coastal plain in the lower course of the Acaraú River, Ceará, Brazil, and to correlate with the granulometry and soil organic matter (SOM) contents, seeking to identify the best method to predict the attributes studied. In four soil profiles (n = 23 soil samples) the sand, silt, and clay and SOM contents were determined and was carried out the mineralogical characterization. Soil samples were submitted to spectral analysis using a spectroradiometer, with spectral range from visible to shortwave to near infrared (350 - 2,500 nm). It was possible to relate the soil attributes such as color, SOM contents, variation in granulometry and even mineralogy aspects, such as types of minerals in the clay fraction, with the spectral reflectance curves. Some spectral interpretations were useful in understanding aspects associated with the genesis of these soils, especially with regard to the formation environment and mineralogy. For the SOM contents, the best estimates were obtained by simple linear regression and higher correlation for the 564 nm spectrum range. Regression methods were efficient in estimating soil attributes, but the study is limited to the small sample size.

X-ray third-order nonlinear diffraction in the asymmetric reflection geometry.

X-ray third-order nonlinear asymmetrical diffraction has three independent parameters: the asymmetry angle, the incident wave intensity and the deviation from the exact Bragg orientation. In contrast to the linear case, in the nonlinear case the total reflection region does not exist for all intensity values and asymmetry angles. Theoretical consideration leads to analytical conditions of the total reflection region, and the analysis can be carried out by a graphical method. An exact solution in the total reflection region is found. The numerical solutions of the third-order nonlinear diffraction allow one to find the reflection curves for a fixed asymmetry angle or for a fixed intensity. For very large or very small asymmetry factors the third-order nonlinear effects can be observed for beams with very low intensities.

An optical sensor combining surface plasmon resonance, light extinction, and near-critical angle reflection, for thin liquid film biochemical sensing

We present a novel and low-cost optical sensor to obtain at the same time, fast and label-free optical information such as reflectivity, refractive index and extinction coefficient of biochemical samples. The sensor measures in around one minute optical internal reflectivity as a function of the angle of incidence at the interface between a glass prism covered by a gold nanofilm (≈20 nm) in contact with a liquid sample (≈10 µL). The nanofilm is thin enough that a large fraction of the incident light transmits through it at angles of incidence below the critical angle set by the prism and sample refractive indices (≈ 61°), but thick enough to present a Surface Plasmon Resonance dip for angles of incidence beyond that critical angle. The calculated sensitivity of SPR to the surface refractive index is 168.35 deg/RIU. We demonstrate that when a sample contains live bacteria (E. coli) the whole reflectivity curve including the SPR region is clearly affected, and to adjust a theoretical model to the experimental curves, it is necessary to assume a complex refractive index of the nanofilm appreciably different than that of gold. The optical curve of the sensor provides more information than a conventional SPR measurements offering a more complete strategy for the analysis of biochemical substances and bacterial cell suspensions.