Search Results (1,603)

This paper aims to review and summarize the performance assessment of PV/T modules with optical filtration layers and different materials designed to achieve full spectral utilization of sunlight through absorptive, refractive, reflective, and diffractive approaches. Different categories of optical filtration layers, including nanofluids, nano-enhanced phase change materials, the luminescent down-shifting technique, the radiative cooling technique, the colored optical technique, nanowires, and polymer materials, are examined and compared. Additionally, the cost-effectiveness of PV/T modules with optical filtration layers is evaluated by using the net present values, price-performance factor, least cost of energy, and life-cycle cost method in practical applications. This paper also discusses current challenges, future perspectives, recommendations, and potential applications aimed at overcoming the limitations for real-world implementation. Results conclude that the overall energy performance of the PV/T system with optical filtration layers can be enhanced by 85–90%, while the system payback period is reduced to less than 6 years compared to conventional PV/T modules. Full article

Accurate color measurement is crucial for ensuring reliable sensing performance in vision-based applications. However, existing color measurement methods suffer from illumination variability, operational complexity, and perceptual subjectivity. In this study, dental color measurement, with its strict perceptual and spectral fidelity demands, is adopted to validate the proposed method. Using self-made resin-permeated ceramic teeth, this study proposes a deep-learned end-to-end spectral reflectance prediction framework to achieve snapshot teeth spectral reflectance from RGB images under complex light sources in the fundamental spectral domain through the construction of a physically interpretable network that enables physically informed feature fusion. A dual-attention modular-information fusion neural network is developed to recover the spectral reflectance directly from the RGB image for natural teeth and ceramics across multiple scenarios. A dataset containing 4000 RGB–hyperspectral image pairs is built from a self-designed optical system with complex illumination conditions. Results confirm that the proposed framework demonstrates effective performance in predicting teeth spectral reflectance with an MSE of 0.0024 and an SSIM of 0.8724. This method achieves high-accuracy color measurement while avoiding the color mismatch caused by metamerism, which empowers various advanced applications including optical property characterization, 3D surface reconstruction, and computer-aided restorative design. Full article

This study evaluates the drying kinetics of banana slices sliced at various infrared powers and measurable values, as well as the spectral and microstructural changes that some physical quality parameters present. Banana slices were dried at 300, 400, and 500 W (894, 1190 and 1410 W/m² infrared radiation intensity) medium wavelength infrared (MWIR). In addition, banana samples were sliced to be 6–8 and 10 mm. The drying processes were terminated when the samples reached approximately 30% moisture level. After drying, banana samples’ quality values, such as color, shrinkage, and water loss were evaluated. FT-NIR (Fourier Transform-Near Infrared) spectroscopy and microstructure measurements were performed. For banana slices dried at different powers with medium-wavelength infrared, the shortest drying time is for 6 mm thick products and can be operated in the range of 33–36 min⁻¹. When the color values were examined, it was determined that the lowest total color changes occurred at 500 W drying power. In shrinkage measurements, samples dried at 500 W power were observed at the highest frosting. In water loss analyses, statistically similar results were obtained at 500 W drying power for various thicknesses. While the microstructural configurations of sliced banana samples were observed to be smoother during drying, samples dried at 300 W power were detected in a tighter form during drying and they were combined more regularly at 500 W power. FT-NIR spectral measurements were again expressed independently of the reflection values due to the wide pore range in high-power infrared drying (500 W). Full article

As a solid mixture discharged during coal production, coal gangue possesses comprehensive utilization potential. Efficient sorting and pre-enrichment of its classification are crucial for green mining practices. This study categorizes coal gangue into four types—residual coal (RC), gray gangue (GG), red gangue (RG), and white gangue (WG)—based on their apparent color and utilization properties. The research systematically analyzed how different light sources and illumination intensities affect the visual characteristics of these gangue types. The results indicate that white light sources most accurately reproduce the real coloration and texture features of coal gangue, with optimal textural clarity achieved at moderate illumination levels. Different colored light sources selectively enhance spectral reflectance, and red light significantly improves RG recognition. Support vector machine (SVM)-based classification experiments demonstrate that white light sources achieve optimal performance under moderate illumination (23,000 Lux) with Macro-F1 = 0.90, representing a 15.38% improvement over other conditions. These findings reveal that reasonable matching of light source and illumination intensity can substantially enhance the accuracy of the visual recognition of coal gangue, providing valuable optimization guidance for future precise classification applications. Full article

Background: The human visual system is capable of processing large quantities of visual objects with varying levels of abstraction. The brain also exhibits hierarchical integration and learning capabilities that combine various attributes of visual objects (e.g., color, shape, local features, and categories) into coherent representations. However, prevailing theories in visual neuroscience employ simple stimuli or natural images with uncontrolled feature correlations, which constrains the systematic investigation of multidimensional representation dynamics. Methods: In this study, we aimed to bridge this methodological gap by developing a novel large tangram paradigm in visual cognition research and proposing cognitive-associative encoding as a mathematical basis. Critical representation dimensions—including animacy, abstraction level, and local feature density—were computed across a public dataset of over 900 tangrams, enabling the construction of a hierarchical model of visual representation. Results: Neural responses to 85 representative images were recorded using Electroencephalography (n = 24), and subsequent behavioral analyses and neural decoding revealed that distinct representational dimensions are independently encoded and dynamically expressed at different stages of cognitive processing. Furthermore, representational similarity analysis and temporal generalization analysis indicated that higher-order cognitive processes, such as “change of mind,” reflect the selective activation or suppression of local feature processing. Conclusions: These findings demonstrate that tangram stimuli, structured through cognitive-associative encoding, provide a generalizable computational framework for investigating the dynamic stages of human visual object cognition. Full article

The harmonized multi-sensor satellite data assists users by providing seamless analysis-ready data with enhanced temporal resolution. The Harmonized Landsat Sentinel (HLS) product has gained popularity due to the seamless integration of Landsat OLI and Sentinel-2 MSI, achieving a temporal resolution of 2.8 to 3.5 days. However, applications that require monitoring intervals of less than three days or cloudy data can limit the usage of HLS data. Gaofen-1 (GF-1) Wide Field of View (WFV) data provides the capacity further to enhance the data availability by harmonization with HLS. In this study, GF-1/WFV data is harmonized with HLS by employing deep learning-based conditional Generative Adversarial Networks (cGANs). The harmonized WFV data with HLS provides an average temporal resolution of 1.5 days (ranging from 1.2 to 1.7 days), whereas the temporal resolution of HLS varies from 2.8 to 3.5 days. This enhanced temporal resolution will benefit applications that require frequent monitoring. Various processes are employed in HLS to achieve seamless products from the Operational Land Imager (OLI) and Multispectral Imager (MSI). This study applies 6S atmospheric correction to obtain GF-1/WFV surface reflectance data, employs MFC cloud masking, resamples the data to 30 m, and performs geographical correction using AROP relative to HLS data, to align preprocessing with HLS workflows. Harmonization is achieved without using BRDF normalization and bandpass adjustment like in the HLS workflows; instead, cGAN learns cross-sensor reflectance mapping by utilizing a U-Net generator and a patchGAN discriminator. The harmonized GF-1/WFV data were compared to the reference HLS data using various quality indices, including SSIM, MBE, and RMSD, across 126 cloud-free validation tiles covering various land covers and seasons. Band-wise scatter plots, histograms, and visual image color quality were compared. All these indices, including the Sobel filter, histograms, and visual comparisons, indicated that the proposed method has effectively reduced the spectral discrepancies between the GF-1/WFV and HLS data. Full article

In this study, poplar boards were bleached and treated with two types of urea–formaldehyde-coated ternary system thermochromic microcapsules (UF@TS), which were mixed with UV primer. The bleached poplar boards were manually painted with two layers of primer and topcoat. Coating samples with varying microcapsule contents were prepared and evaluated based on factors such as glossiness, reflectivity, and other surface properties. The experimental results showed that bleaching treatment significantly increased the whiteness of poplar wood, with an improvement rate of up to 17%. Among the two microcapsule types, the coating containing #2 microcapsules exhibited superior surface quality compared to #1 microcapsules. As the microcapsule content increased, the coating glossiness showed an overall decreasing trend and a certain degree of fluctuation, and the #2 microcapsule showed lower reflectivity values. The addition of UF@TS microcapsules negatively affected the coating adhesion but had little effect on hardness. The #2 microcapsule enhanced the impact resistance of the coating to a certain extent and increased surface roughness. Regarding thermochromic performance, the #1 microcapsule exhibited higher color-changing temperature and larger color difference, while the #2 microcapsule showed color-changing temperature closer to room temperature. Despite a decline in thermochromic performance and glossiness during aging, the 1# microcapsule showed slightly better stability. The coating containing 10% #2 microcapsules demonstrated the best comprehensive performance on bleached poplar wood, with glossiness of 2.1 GU, reflectivity of 67.95%, adhesion grade of 1, hardness of 6 H, impact resistance grade of 4, and surface roughness of 0.681 μm. The ΔE in the range of −20 °C to 50 °C was 7.434. After aging, ΔE was 5.846, and the light loss rate was 9%, with excellent comprehensive performance. Full article

Ten ukiyo-e woodblock prints from the collection of the Museo delle Culture in Lugano (Switzerland) were analyzed to identify the materials used in their production. These Japanese artworks were traditionally created with colors derived from minerals and plants, mixed with diluted animal glue and applied to paper using wooden matrices. Due to their fragility, non-invasive external reflection infrared spectroscopy and imaging analysis were employed. Spectral data were compared with reference samples of Japanese pigments and existing literature, reflecting the growing interest in the characterization of ukiyo-e prints. Within the limits of the non-invasive approach, several colorants were identified, including akane (madder), suo (sappanwood), yamahaji (Japanese sumac), kariyasu (Eulalia), and kio (orpiment), along with a proteinaceous binding medium. The extensive use of bero-ai (Prussian blue), applied both as a pure pigment and in mixtures, was confirmed. Notably, mica was detected in the background of one print, providing the first analytical evidence of the kirazuri decorative technique, which produces a sparkling, silver-like effect. Ultraviolet-induced fluorescence imaging further contributed to the assessment of conservation status, revealing faded decorative motifs and signs of previous water damage. Full article

Alzheimer’s disease (AD) is the leading cause of dementia worldwide and is becoming one of the most morbid diseases of this century. Recently, ocular research in AD has gained significance, as the eye, due to its close relationship with the brain, can reflect the presence of neurological disorders. Several studies have reported alterations in various ocular structures in AD, ranging from tear fluid to the retina. These changes, particularly in the retina and the optic nerve, along with cerebral atrophy affecting visual brain areas, may lead to visual dysfunctions. This narrative review summarizes and critically examines current evidence on these impairments and explores their possible underlying mechanisms. A decrease in visual acuity, contrast sensitivity, and color vision has been observed, primarily associated with retinal ganglion cell loss or damage. Furthermore, alterations in the visual field, ocular motility, and visual perception have been recorded, mainly resulting from cortical changes. These optical parameters frequently correlate with patients’ cognitive status. In conclusion, these findings highlight the importance of developing strategies to preserve visual function in these patients, helping to prevent further deterioration in their quality of life, and emphasize the potential of visual function assessment as a tool for diagnosis or predicting AD progression. Full article

Papaver rhoeas L. has four strikingly red petals with a distinctly black area bordered by a thin white line at the petal base, thus creating a color pattern that makes the center of the flower, where the pollen is located, visually stand out. This paper aims to assess the intra-petal spatial variability in P. rhoeas petal color intensity and hue and associate it with corresponding differences in the amount and type of petal pigments. The distribution of pigments in the petal epidermis was investigated in different petal segments by column chromatography. Fresh petals were extracted with deionized water during blooming, between April and June 2023, in northwestern Greece. UV–visible absorption spectra of the eluted fractions revealed five pigments, with each pigment belonging to a different elution zone. In the black spots of the petals, anthocyanin coexists with a yellow flavonol with a maximum absorption peak at 340 nm. Red petal extract in 70:30 ethanol–water showed a distinct negative Cotton effect at 284 nm, distinct from black segment extract with a negative Cotton effect at 227 nm. The uneven distribution of floral pigments along the petal epidermis creates a unique color palette, enabling UV-reflection, which is key in attracting pollinators responsible for plant reproduction. Full article

Land observation multispectral satellites (e.g., Landsat-8/9 and Sentinel-2) offer high spatial resolution but have limited spectral bands for water color observation and insufficient spectral resolution. This study proposes a spectral reconstruction model based on a residual neural network (Deep Spectral Reconstruction Learning Network, DSR-Net) to provide additional spectral bands support for nearshore water observations. The model is trained on 60 million pairs of quasi-synchronous reflectance data, and achieves stable reconstruction of 15 water color channels of the surface level reflectance for water pixels (ρ_w) from visible to near-infrared bands, considering sensor noise and atmospheric correction errors. Validation results based on AERONET-OC data show that the root mean square error of reconstructed ρ_w by DSR-Net ranges from 4.09 to 5.18 × 10⁻³, representing a reduction of 25% to 43% compared to original atmospheric correction results. The reconstruction accuracy reaches the observation level of the Sentinel-3/OLCI water color sensor and is universally applicable to different water categories, effectively supporting nearshore water color observation tasks such as colored dissolved organic matter inversion and cyanobacteria monitoring. The errors in the multispectral reflectance-based ρ_w primarily arise from sensor noise and atmospheric correction errors. After DSR-Net reconstruction, approximately 59% of the uncertainty caused by sensor noise and 38% of that caused by atmospheric correction errors are reduced. In summary, the spectral reconstruction products generated by DSR-Net not only significantly enhance the water color observation capabilities of current satellite sensors but also provide critical technical support for marine environmental monitoring and the design of next-generation sensors. Full article

The terms fillenoert, villemort, feulje mort, and fillemot are obsolete historical color names derived from the French feuille morte (dead leaf), referred to a broad spectrum of brownish, yellowish, greenish, and reddish hues in early modern textile dyeing. This study investigates the visual identity and chromatic range of dead leaf by reconstructing dye recipes from seventeenth- and eighteenth-century European dyeing manuals. Using historically accurate materials and techniques, wool samples were dyed and analyzed through CIELAB color measurements to quantify their hue values. The results reveal that dead leaf does not correspond to a single, fixed color but represents a flexible and metaphorical category, reflecting both the natural variation in dead foliage and the diversity of historical dyeing practices. In early modern Europe, colors were often descriptive, frequently referencing the natural world or objects. These descriptors offered a nuanced vocabulary that extended far beyond today’s basic chromatic terms. Reworking these recipes reveals the complex interplay between chromatic language, material practices, and color perception. Historical color names served not merely as labels but encoded information about dye sources, cultural associations, and socio-economic contexts. Understanding and reviving this terminology deepens our appreciation of early dyeing traditions and bridges past and present conceptions of color. Full article

The influence of a 1% oxygen atmosphere on the color stability of modified atmosphere packaged beef was investigated. Beef silverside slices were packed under 1%, 20%, and 70% oxygen atmospheres and stored at 2 °C for 14 days. Color and reflection data were measured non-invasively. The L*a*b* values were analyzed, the color difference ΔE₂₀₀₀, and the levels of myoglobin (Mb), deoxy-(DMb), oxy-(OMb), and metmyoglobin (MMb) were calculated. The 1% oxygen atmosphere resulted in a rapid MMb formation from 0.63 (day 0) to 1.27 (day 8) (p < 0.05). The other samples showed slight increases from 0.65 to 0.80 MMb (20%) and 0.65 to 0.79 MMb (70%). On day 10, the 20% oxygen sample showed an increased MMb formation (1.33 MMb). The 70% atmosphere resulted in a final value of 0.91 MMb after 14 days. These results show that an oxygen content of 1% accelerates the formation of MMb at an early stage. A higher oxygen content in the packaging delays MMb development through OMb formation, which masks MMb creation, to a certain extent. Measuring the packaged meat pieces over a 14-day storage period provides detailed insights into the development of Mb formation and critical points during storage. Full article

Beyond its renowned gemological value, diamond serves as a vital economic mineral and a unique messenger from Earth’s deep interior, preserving invaluable geological information. Since the Mengyin region is the source of China’s greatest diamond deposits, research on the diamonds there not only adds to our understanding of their origins but also offers an essential glimpse into the development of the North China Craton’s mantle lithosphere. In this article, 50 diamond samples from Mengyin were investigated using gemological microscopy, Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, DiamondView™, and X-ray micro-computed tomography (CT) scanning technologies. The types of Mengyin diamonds are mainly Type IaAB, Type IaB, and Type IIa, and the impurity elements are N and H. Inclusions in diamonds serve as direct indicators of mantle-derived components, providing crucial constraints on the pressure–temperature (P–T) conditions during their crystallization. Mengyin diamonds have both eclogite-type and peridotite-type inclusions. It formed at depths ranging from 147 to 176 km, which corresponds to source pressures of approximately 4.45–5.35 GPa, as determined by the Raman shifts of olivine inclusions. The discovery of coesite provides key mineralogical evidence for subduction of an ancient oceanic plate in the source region. The surface morphology of diamonds varies when they are reabsorbed by melts from the mantle, reflecting distinctive features that record subsequent geological events. Distinctive surface features observed on Mengyin diamonds include fusion pits, tile-like etch patterns, and growth steps. Specifically, regular flat-bottomed negative trigons are mainly formed during diamond resorption in kimberlite melts with a low CO₂ (X_CO2 < ~0.5) and high H₂O content. The samples exhibit varying fluorescence under DiamondView™, displaying blue, green, and a combination of blue and green colors. This diversity indicates that the diamonds have undergone a complex process of non-uniform growth. The nitrogen content of the melt composition also varies significantly throughout the different growth stages. The N3 center is responsible for the blue fluorescence, suggesting that it originated in a long-term, hot, high-nitrogen craton, and the varied ring band structure reveals localized, episodic environmental variations. Radiation and medium-temperature annealing produce H3 centers, which depict stagnation throughout the ascent of kimberlite magma and are responsible for the green fluorescence. Full article

A novel self-healing brass powder/waterborne acrylic decorative coating for wooden substrates was developed, in which γ-methacryloxypropyltrimethoxysilane (KH570)-modified brass powder (with a coupling agent concentration of 6% and reaction solution pH of 5) was employed as the filler, and melamine-formaldehyde (MF) resin-encapsulated water-based paint microcapsules were utilized as the healing agent. The brass powder content and the core–wall ratio of the topcoat microcapsules were identified as the predominant factors affecting both the optical and mechanical properties of the self-healing brass powder/waterborne acrylic coating on Basswood surfaces. Therefore, the brass powder content was selected as the primary influencing factor. With concentration gradients of 0.5%, 1%, 3%, 5%, 7%, 9%, and 10%, and under constant conditions of 3% microcapsule content and room temperature curing, the effect of brass powder content on the properties of self-healing microcapsule coatings with different core–wall ratios was investigated. The waterborne acrylic wood coating containing 3% brass powder and 3% microcapsules with a core–wall ratio of 0.58:1 exhibited superior overall performance. This optimized formulation not only maintained excellent optical properties but also significantly enhanced mechanical performance, while preserving outstanding aging resistance, liquid resistance, and self-healing capability. The coating demonstrated the following comprehensive performance metrics: a glossiness of 24.0 GU, color difference (ΔE) of 2.13, chromatic aberration (ΔE*) of 13.68, visible light reflectance of 0.5879, dominant wavelength of 587.47 nm, visible light transmittance of 74.33%, pencil hardness of H grade, impact resistance of 2 kg·cm, adhesion rating of class 2, surface roughness of 2.600 μm, along with excellent aging resistance and liquid resistance properties, while achieving a self-healing efficiency of 19.62%. The coating also exhibited a smooth and uniform microscopic morphology, with the chemical bonds of both the modified brass powder and microcapsules remaining intact within the coating matrix. Full article