Diffuse Transmission Research Articles

Non-Destructive Discrimination of Sunflower Seeds with Different Internal Mildew Grades by Fusion of Near-Infrared Diffuse Reflectance and Transmittance Spectra Combined with 1D-CNN.

Internally mildewed sunflower seeds, which cannot be recognized and discarded based on their appearance, pose a serious risk to human health. Thus, there is a need for a rapid non-destructive mildew grade discrimination method. Currently, few reports are available regarding this process. In this study, a method based on the combination of the near-infrared diffuse reflectance and near-infrared diffuse transmission (NIRr-NIRt) fusion spectra and a one-dimension convolutional neural network (1D-CNN) is proposed. The NIRr-NIRt fusion spectra can provide more complementary and comprehensive information, and therefore better discrimination accuracy, than a single spectrum. The first derivative (FD) preprocessing method could further improve the discrimination effect. By comparison against three conventional machine learning algorithms (artificial neural network (ANN), support vector machine (SVM), and K-nearest neighbor (KNN)), the 1D-CNN model based on the fusion spectra was found to perform the best. The mean prediction accuracy was 2.01%, 5.97%, and 10.55% higher than that of the ANN, SVM, and KNN models, respectively. These results indicate that the CNN model was able to precisely classify the mildew grades with a prediction accuracy of 97.60% and 94.04% for the training and test set, respectively. Thus, this study provides a non-destructive and rapid method for classifying the mildew grade of sunflower seeds with the potential to be applied in the quality control of sunflower seeds.

Achieving robustness to temperature change of a NIR model for apple soluble solids content

AbstractThe temperature difference of fruit itself will affect its near infrared spectrum and the accuracy of its soluble solids content (SSC) prediction model. To eliminate the influence of apple temperature difference on the SSC model, a diffuse transmission dynamic online detection device was used to collect the spectral data of apples at different temperatures, and four methods were used to establish partial least squares correction models: global correction, orthogonal signal processing, generalized least squares weighting and external parameter orthogonal (EPO). The results show that the temperature has a strong influence on the diffuse transmission spectrum of apples. The 20 ºC model can get a satisfactory prediction result when the temperature is constant, and there will be great errors when detecting samples at other temperatures. The effect of temperature must be corrected to establish a more general model. These methods all improve the accuracy of the model, with the EPO method giving the best results; the prediction set correlation coefficient is 0.947, the root mean square error of prediction is 0.489%, and the prediction bias is 0.009%. The research results are of great significance to the practical application of SSC prediction of fruits in sorting workshops or orchards.

Diffusion of light in turbid media with internal reflections

We relate the the Kubelka-Munk equations for the description of the intensity transfer of light in turbid media to a one-dimensional diffusion equation, which is obtained by averaging the three-dimensional diffusion equation over the lateral directions. This enables us to identify uniquely the Kubelka-Munk parameters and derive expressions for diffuse reflection and transmission coefficients including the effect of internal reflections. Without internal reflections we recover the Kubelka-Munk formulae for these coefficients. We show that the Kubelka-Munk equations are the proper radiative-transfer equations for the one-dimensional diffusion problem.

Uncertainty quantification of diffuse sound insulation values

The sound transmission loss of a partitioning structure depends on the nature of the sound fields in the source and receiver spaces. In an indoor setting, both sound fields are often taken to be diffuse. A diffuse field may represent the sound field of a conceptual ensemble of rooms with the same volume and reverberation time, but otherwise any possible arrangement of boundaries and small objects that have a wave scattering effect. Uncertainty due to random wave scattering is therefore inherently present in the diffuse transmission loss values. In this paper, closed-form expressions are derived for quantifying this uncertainty, such that it becomes possible to estimate by how much the transmission loss of a particular room–wall–room system may deviate from the nominal, ensemble-averaged diffuse value which corresponds to omni-directional incidence and halfspace radiation. First, an exact expression is derived for the harmonic or band-averaged diffuse transmission loss variance, based on hybrid deterministic–statistical energy analysis theory. Its evaluation requires knowledge of the dynamic stiffness of the partitioning structure and of the radiation impedances of the surrounding fluids. Subsequently, an approximate expression is derived, which depends on energy-related quantities only, making it also applicable in an experimental setting. Furthermore, it is demonstrated that the diffuse transmission loss is approximately normally distributed, such that a complete uncertainty quantification is possible from the mean and variance values. The expressions are verified in a Monte-Carlo simulation study involving a single wall and then validated with experimental data of double-leaf plasterboard walls containing flexible steel studs.

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette.

Many applications seek to measure a sample's absorption coefficient spectrum to retrieve the chemical makeup. Many real-world samples are optically turbid, causing scattering confounds which many commercial spectrometers cannot address. Using diffusion theory and considering absorption and reduced scattering coefficients on the order of 0.01 mm-1 and 1 mm-1, respectively, we develop a method which utilizes frequency-domain to measure absolute optical properties of turbid samples in a standard cuvette (45 mm × 10 mm × 10 mm). Inspired by the self-calibrating method, which removes instrumental confounds, the method uses measurements of the diffuse complex transmittance at two sets of two different source-detector distances. We find: this works best for highly scattering samples (reduced scattering coefficient above 1 mm-1); higher relative error in the absorption coefficient compared to the reduced scattering coefficient; accuracy is tied to knowledge of the sample's index of refraction. Noise simulations with 0.1 % amplitude and 0.1° = 1.7 mrad phase uncertainty find errors in absorption and reduced scattering coefficients of 4 % and 1 %, respectively. We expect that higher error in the absorption coefficient can be alleviated with highly scattering samples and that boundary condition confounds may be suppressed by designing a cuvette with high index of refraction. Further work will investigate implementation and reproducibility.

Integrated genomic surveillance enables tracing of person-to-person SARS-CoV-2 transmission chains during community transmission and reveals extensive onward transmission of travel-imported infections, Germany, June to July 2021.

BackgroundTracking person-to-person SARS-CoV-2 transmission in the population is important to understand the epidemiology of community transmission and may contribute to the containment of SARS-CoV-2. Neither contact tracing nor genomic surveillance alone, however, are typically sufficient to achieve this objective.AimWe demonstrate the successful application of the integrated genomic surveillance (IGS) system of the German city of Düsseldorf for tracing SARS-CoV-2 transmission chains in the population as well as detecting and investigating travel-associated SARS-CoV-2 infection clusters.MethodsGenomic surveillance, phylogenetic analysis, and structured case interviews were integrated to elucidate two genetically defined clusters of SARS-CoV-2 isolates detected by IGS in Düsseldorf in July 2021.ResultsCluster 1 (n = 67 Düsseldorf cases) and Cluster 2 (n = 36) were detected in a surveillance dataset of 518 high-quality SARS-CoV-2 genomes from Düsseldorf (53% of total cases, sampled mid-June to July 2021). Cluster 1 could be traced back to a complex pattern of transmission in nightlife venues following a putative importation by a SARS-CoV-2-infected return traveller (IP) in late June; 28 SARS-CoV-2 cases could be epidemiologically directly linked to IP. Supported by viral genome data from Spain, Cluster 2 was shown to represent multiple independent introduction events of a viral strain circulating in Catalonia and other European countries, followed by diffuse community transmission in Düsseldorf.ConclusionIGS enabled high-resolution tracing of SARS-CoV-2 transmission in an internationally connected city during community transmission and provided infection chain-level evidence of the downstream propagation of travel-imported SARS-CoV-2 cases.

Plasmonic and Conductive Structures of TCO Films with Embedded Cu Nanoparticles.

Cu nanoparticles were produced by using solid-state dewetting (dry) of a 1.3 nm Cu layer or laser ablation of a Cu solid target (wet) in acetone and methanol. The morphology and chemical composition of the nanoparticles were investigated as a function of the synthesis methods and their key parameters of the annealing temperature (200–500 °C) and the liquid environment during the ablation. Cu nanoparticles were then embedded in transparent conductive oxide (TCO) films as aluminum-doped zinc oxide (AZO) or zirconium-doped indium oxide (IZrO); the TCObott/Cu nanoparticle/TCOtop structures were synthesized with all combinations of AZO and IZrO as the top and bottom layers. The goal was to achieve a plasmonic and conductive structure for photovoltaic applications via a comparison of the involved methods and all fabricated structures. In particular, solid-state dewetting produced faceted or spherical (depending on the annealing temperature) nanoparticles with an average size below 150 nm while laser ablation produced spherical nanoparticles below 250 nm. Dry and wet plasmonic conductive structures as a function of the TCOs employed and the temperature of annealing could reach a sheet resistance of 86 Ω/sq. The energy band-gap Egap, absorbance, transmittance, and reflectance of the plasmonic conductive structures were investigated in the UV–vis–NIR range. They showed a dependence on the sequence of the top and bottom TCO, with best transmittances of 89.4% for the dry plasmonic conductive structure and 84.7% for the wet plasmonic conductive structure. The latter showed a higher diffused transmittance of between 10–20% in the visible range.

Palladium-modified TiO2 films in a photocatalytic microreactor: evaluation of radiation absorption properties and pollutant degradation efficiency.

Pure (TiO2) and 0.1 nominal atomic percent of palladium-modified TiO2 (Pd-TiO2) films were synthesized via a sol-gel method and compared through their physicochemical properties and photocatalytic activity in the degradation of an emerging contaminant, 17-α-ethinylestradiol (EE2). The activity of the films was studied using a continuous flow, planar microreactor under simulated sunlight. Catalysts characterization included X-ray diffraction, UV-Visible diffuse reflectance and transmittance spectroscopy, atomic force microscopy, transmission electron microscopy, Raman spectroscopy, N2 physisorption analysis, and X-ray photoelectron spectroscopy. The modification of TiO2 with palladium confined the size of anatase phase crystallites, increased the specific surface area and improved radiation absorption. PdO domains on TiO2 were observed. In all the tested conditions, higher conversion of EE2 was achieved with the Pd-TiO2 film compared with the TiO2 film, presenting an 80% increase in the reaction rate. The performance of the catalytic films was also assessed by the calculation of two efficiency parameters: radiation absorption efficiency and quantum efficiency of reaction. The Pd-TiO2 film showed a notable enhancement of the absorption of the incident radiation and a more efficient utilization of the absorbed photons to degrade the target pollutant.

Synthesis of Tb-doped SiO2 glasses by spark plasma sintering method and evaluation of photoluminsecence and thermally stimulated luminescence properties

Tb-doped SiO2 glasses were synthesized by the spark plasma sintering (SPS) method, and optical and thermally stimulated luminescence (TSL) properties were investigated. The diffuse transmittance spectra of the 0.01, 0.05, and 0.1% Tb-doped SiO2 samples included the absorption due to the 4f-5d transitions of Tb3+ ions. In photoluminescence properties, all the Tb-doped SiO2 samples showed several emission peaks due to the 4f-4f transitions of Tb3+ ions and oxygen deficiency vacancy (ODC). The TSL glow curves indicated the glow peak at 140 °C, and only the emission peaks attributed to the 4f-4f transition of Tb3+ ions were observed in TSL spectra of the 0.01, 0.05, and 0.1% Tb-doped SiO2 samples. The integrated TSL intensity of the 0.1% Tb-doped samples had a proportional relationship in the range of 0.01–1000 mGy. The TSL intensity of the 0.05% Tb-doped glass after 72 h from X-ray irradiation was about 69% with respect to the one immediately after X-ray irradiation. In addition, the 0.05% Tb-doped SiO2 glass could use the multiple time for TSL dosimetry.

Scintillation property of undoped NaI transparent ceramics

In this study, NaI transparent ceramics were synthesized by the spark plasma sintering method, also optical and scintillation properties were investigated. To evaluate the potential of the transparent ceramics, a NaI single crystal was also prepared by the vertical Bridgman–Stockbarger method. The diffuse transmittance of the transparent ceramic fabricated at 470 °C was equivalent to that of the single crystal. All the samples showed scintillation peaking at 320 nm due to self-trapped exciton. In addition, scintillation peaks ascribed from lattice defects were detected at 450 nm for the transparent ceramics and 540 nm for the single crystal. The scintillation decay time constants of the transparent ceramic fabricated at 440 °C were 5.7, 18, and 189 ns. The light yield of the transparent ceramic turned out to be 910 photons MeV−1 and was two-thirds of the single crystal.

A facile synthesis of visible light driven Ni3V2O8 nano-cube/BiVO4 nanorod composite photocatalyst with enhanced photocatalytic activity towards degradation of acid orange 7

Photocatalysis is one of the promising method to degrade harmful organic pollutants under visible light exposure. In this work, a novel Ni3V2O8/BiVO4 nanocomposite has been prepared by one-pot hydrothermal method, and investigated through X-ray diffraction, FT-IR, UV–visible diffuse reflectance spectroscopy, scanning and transmission electron microscopy and photoluminescence techniques. Subsequently, the photocatalytic performance of Ni3V2O8/BiVO4 nanocomposite has been examined by degrading AO7 under visible light illumination. The photocatalytic efficiency of the optimized 1:2 ratio of Ni3V2O8/BiVO4 nanocomposite photocatalyst is found to be 87% with a rate constant value of 0.03387 min−1 which are higher than those of other prepared photocatalysts. This nanocomposite exhibits excellent stability even after 3 three cycles, and shows 1.135- and 1.17-times higher photocurrent intensity than pure BiVO4 and Ni3V2O8 respectively. The mechanism for the degradation of AO7 over Ni3V2O8/BiVO4 nanocomposite photocatalyst has been proposed.

An Automated Hemispherical Scanner for Monitoring the Leaf Area Index of Forest Canopies

The leaf area index (LAI) is an important structural parameter of plant canopies used in terrestrial biosphere models. Optical methods are commonly used for measuring LAI due to their non-destructive nature, convenience, and rapidity. In the present study, a novel instrument, named the Automated Hemispherical Scanner (AHS), was developed to measure plant area index (PAI) for monitoring daily changes in LAI in forest ecosystems. In the AHS, an optical sensor driven by a pair of servomotors is used to observe hemispherical light transmission continuously at adjustable intervals, and a blue filter is used to reduce the multiple scattering effect of light on the measured transmission. A set of algorithms was developed to screen the direct radiation transmitted through the canopy and to compute the transmissions from the diffuse radiation at seven zenith (0–60) and seven azimuth (0–150) angles for calculating PAI. Field experiments were conducted to verify the reliability of the AHS in three forests of Northeast China against an existing instrument named the LAI-2200 Plant Canopy Analyzer. The PAI values obtained using the AHS agreed well (R2 = 0.927, root mean square error = 0.41) with those from the LAI-2200. Since both instruments use the same gap fraction theory for calculating the PAI from diffuse radiation transmissions obtained from multiple angles, the agreement of these two instruments means that the AHS can reliably measure the transmittance of diffuse radiation and the theory has been implemented correctly. Compared with LAI-2200, the AHS has the advantage of automated and continuous measurements, and therefore it is suitable for monitoring variations in PAI over extended periods, such as the whole growing season. Compared with widely used digital photographic techniques, the AHS also avoids the requirement of determining a suitable photographic exposure, which is often problematic in the field with variable sky conditions. With these advantages, the AHS could be deployed in forest growth monitoring networks.

Establishment of Non-Destructive Methods for the Detection of Amylose and Fat Content in Single Rice Kernels Using Near-Infrared Spectroscopy

For the efficient selection of high-quality rice varieties, the near-infrared spectroscopy (NIRS) technique has been widely applied to detect constituents in single rice kernels. Compared with other constituents, amylose content (AC) and fat content (FC) are the key parameters that can affect the quality of rice. Based on two modified AC and FC trace detection methods, two NIRS methods to detect AC and FC in single rice kernels were developed. Using the proposed methods, the AC and FC in two groups of rice kernel datasets were measured. The datasets were collected on two spectrometers with different sample movement states (static and dynamic) and measurement modes (diffuse reflectance (NIRr) and diffuse transmission (NIRt)). By optimizing the pre-treatment method and spectral range, the determination coefficients of cross-validation (R2cv) and prediction (R2p) of the NIRS models under different measurement conditions were all above 0.6. The results indicated that the proposed methods were applicable to the rapid, non-destructive detection and sorting of individual rice seeds with different AC and FC, and it was shown that these methods can meet the requirements of the rough screening of rice seed varieties.

Optical Properties and Fluence Distribution in Rabbit Head Tissues at Selected Laser Wavelengths.

The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka–Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo simulation was implemented for estimating the optical fluence distribution through a model containing the three tissue layers. The scattering coefficient decreased at longer wavelengths, leading to an increase in optical fluence inside the tissue samples, indicating a higher penetration depth, especially at 980 nm. In general, the obtained results show good agreement with relevant literature.

Online soluble solids content (SSC) assessment of multi-variety tomatoes using Vis/NIRS diffuse transmission

This study investigates the potential of the online diffuse transmission Vis/NIRS technology for quantitative soluble solids content (SSC) assessment of multi-variety tomatoes. For every single-variety tomato, the stem-calyx axis horizontal with stem towards (T1 orientation) is verified to be the best detection orientation with the simpler propagation light path or shorter light path distance. Compared to the full wavelength after Savitzky-Golay smoothing (SGS) pretreatment, the partial least squares regression (PLSR) model performance can be further improved by the selected Competitive Adaptive Reweighted Sampling (CARS) key wavelengths. The best CARS-PLSR model performances are Tianci-595 (Rp = 0.85, RMSEp = 0.21), Xianke-No.8 (Rp = 0.87, RMSEp = 0.20), and Yuanwei-No.1 (Rp = 0.87, RMSEp = 0.35), respectively. For multi-variety tomatoes, it is difficult to find a universal SSC prediction method regardless of mutual prediction between different models or mixed models of different tomato varieties. Our results in the present study reveal the potential for online diffuse transmission Vis/NIRS technology as a valuable method for tomato SSC assessment. The potential of key wavelengths in multi-variety tomatoes' universal SSC prediction requires further experimental verification and optimization.

Dy-concentration dependence on dosimetric properties of CaF2 transparent ceramics

In this study, we synthesized Dy-doped CaF2 transparent ceramics with several concentrations and evaluated optical, thermally stimulated luminescence (TSL), and optically stimulated luminescence (OSL) properties. The 0.05, 0.1, and 0.5% Dy-doped samples had diffuse transmittance of approximately 60% at 500 nm, and the absorption band appeared at around 280 nm after X-ray irradiation. The photoluminescence (PL) excitation wavelengths were 255, 295, 325, 350, 360, and 390 nm. When Dy concentration was 0.1%, the PL quantum yield was maximum. The OSL peaks of the Dy-doped samples was observed at 480, 570, and 660 nm by the optical stimulation at 280 nm. The TSL glow curves of the 0.5 and 1.0% Dy-doped samples consisted of the glow peaks at 75, 160, and 200 °C. The minimum detectable dose of the 0.5% Dy-doped sample as the OSL and TSL dosimeters was 15 mGy and 0.28 μGy, respectively.

Thermally-stimulated luminescence and optical properties of Eu-doped MgAl2O4 transparent ceramics

Eu-doped MgAl2O4 transparent ceramics were synthesized by the spark plasma sintering technique as a new dosimetric material. The MgAl2O4 ceramics doped with Eu had the diffuse transmittance of 40–60% at longer wavelengths than 500 nm. The 0.01% Eu-doped MgAl2O4 showed the photoluminescence (PL) emission peak at 500 nm under the excitation at 300 nm, while the 0.1% Eu-doped MgAl2O4 clearly showed the PL emission peak at 600 nm under the excitation at 400 nm. These PL were due to 5d-4f transitions of Eu2+ ions and decayed within a few microseconds. The Eu-doped MgAl2O4 exhibited TSL glow peaks at 70, 250, 300, and 440 °C. The relative TSL intensity decreased to 95% within 1 day and was stable for 5 days. The TSL intensity of the 0.01 and 0.1% Eu-doped MgAl2O4 was detectable from 0.01 mGy and increased up to 1000 mGy with a linear relation.

Atmospheric diffuse transmittance of the linear polarization component of water-leaving radiation.

The polarization characteristics of water-leaving radiation contain rich information on oceanic constituents. Determining the atmospheric diffuse transmittance is crucial for extracting the polarization information of water-leaving radiation from the radiation acquired by polarimetry satellites at the top of the atmosphere. However, there is still a lack of understanding of the atmospheric diffuse transmittance of the linear polarization component of water-leaving radiation. Here, we first evaluated the difference between the atmospheric diffuse transmittance of the linear polarization component (TQ, TU) and the intensity component (TI) of the water-leaving radiation based on the Ocean Successive Orders with Atmosphere Advanced radiative transfer model. As a consequence, there were apparent differences between TQ, TU and TI. In the case of a large solar zenith angle and a large viewing zenith angle, the difference between TQ, TU and TI will exceed 1. Meanwhile, compared with TI, the oceanic constituents had a prominent interference with TQ and TU, and the sediment concentration had little interference with TQ and TU in low- and medium-turbidity water with respect to the aerosol model, optical thickness, observation geometry, and phytoplankton. Moreover, TQ and TU lookup tables were generated for medium- and low-turbidity water, which laid the foundation for extracting the water-leaving radiation polarization information from the satellite observation polarization signal.

The impact of the global and local awareness diffusion on epidemic transmission considering the heterogeneity of individual influences.

In this paper, we propose a coupled awareness—epidemic spreading model considering the heterogeneity of individual influences, which aims to explore the interaction between awareness diffusion and epidemic transmission. The considered heterogeneities of individual influences are threefold: the heterogeneity of individual influences in the information layer, the heterogeneity of individual influences in the epidemic layer and the heterogeneity of individual behavioral responses to epidemics. In addition, the individuals’ receptive preference for information and the impacts of individuals’ perceived local awareness ratio and individuals’ perceived epidemic severity on self-protective behavior are included. The epidemic threshold is theoretically established by the microscopic Markov chain approach and the mean-field approach. Results indicate that the critical local and global awareness ratios have two-stage effects on the epidemic threshold. Besides, either the heterogeneity of individual influences in the information layer or the strength of individuals’ responses to epidemics can influence the epidemic threshold with a nonlinear way. However, the heterogeneity of individual influences in the epidemic layer has few effect on the epidemic threshold, but can affects the magnitude of the final infected density.

Visible light-enable oxidation and antibacterial of zinc oxide hybrid chitosan photocatalyst towards aromatic compounds treatment

A solar-driven, ZnO-supported chitosan (ZnO/CS) photocatalyst has been formulated, with the aim of enhanced photocatalytic activities with a simple acidic mixing process and the gel solidification method. ZnO/CS, with a narrow band gap (2.89 eV) and macro-porous structure was confirmed under Ultra Violet Diffuse Reflection Spectra (UV DRS) and Transmission Electron Microscopy (TEM), respectively. The Field Emission Scanning Electron Microscopy (FESEM) revealed that average bead size of 100–250 µm of the photocatalyst with ZnO stayed in the hexagonal phase, dispersed, and embedded into CS. The adsorption and photocatalyst activity of the hybrid catalyst was investigated regarding the composition of the catalyst, catalyst dosage, pH of the solution, and concentration of the solution. The catalyst with a composition of 2:1 (ZnO/CS) demonstrates the optimum decolarization properties. Catalytic performances were recorded at up to 89% photodecolarization at pH 12 with 10 ppm of methylene blue under visible irradiation. This has brought a new approach for a highly efficient, stable, sustainable, and low-cost dye water treatment technology.