Search Results (721)

The distribution and spectral properties of colored dissolved organic matter (CDOM) in the northern Bay of Bengal were investigated in June 2016. Based on in situ data collected from 100 CDOM samples at 25 stations, the distribution characteristics of CDOM in the surface layer differed markedly from those at 30 m, 75 m, and 100 m. The CDOM spectral slope ($S_{350-500}$) exhibited a broad range, varying from 0.0026 to 0.0300 nm${}^{-1}$, and showed a significant negative correlation with the absorption coefficient $a_{\mathrm{CDOM}}\left(443\right)$. Analysis of salinity and temperature profiles revealed no obvious correlation between the distribution of $a_{\mathrm{CDOM}}\left(443\right)$ and these physical parameters. A comparative analysis with satellite-derived wind and current data indicated that elevated $a_{\mathrm{CDOM}}\left(443\right)$ values in the northeastern surface waters were primarily associated with the southwest monsoon. In contrast, $a_{\mathrm{CDOM}}\left(443\right)$ values in the lower mixed layer were mainly influenced by the combined effects of geostrophic and eddy currents. Full article

Accurate detection of chlorophyll-a (Chl-a) is critical for monitoring water quality in inland waters, where high concentrations of coloured dissolved organic matter (CDOM) complicate retrieval process. Reliable Chl-a estimation depends on the precise determination of the phytoplankton absorption coefficient (a_ph). This study evaluates Chl-a detection from in situ a_ph measurements and assesses the accuracy of phytoplankton absorption retrieval from Sentinel-2/MSI (S2) and Sentinel-3/OLCI (S3) using the Case-2-Regional-Coast-Colour (C2RCC) processor across diverse optical water types (OWTs) in boreal lakes. OWTs were classified based on remote sensing reflectance features, representing Clear, Moderate, Turbid, Very Turbid, and Brown conditions. CDOM absorption strongly influenced the underwater light field, particularly in Brown and Turbid waters. Linear relationships between a_ph and Chl-a were generally strong across OWTs, with improved relationships in the red spectral region (670 nm). Satellite-derived a_pig estimates showed a weak relationship with in situ data (R² = 0.26–0.45). Both sensors overestimated small a_ph values, while S3 underestimated larger ones. S2 underestimated a_ph in Clear and Brown OWTs, with median absolute percentage differences near 100% for all OWTs. These findings emphasize the challenges posed by bio-optical complexity in boreal lakes and highlight the need for OWT-specific algorithms to improve satellite-based absorption and Chl-a retrieval accuracy. Full article

Mycelium-based composites (MBCs) have already been applied in various fields, like construction, architecture, packaging, waste management and many others, as sustainable replacement materials. The composites created from such materials are lightweight, biodegradable and can take many different geometrical shapes. As there are many different combinations of fungal mycelium and organic substrates, it is not only important to investigate and determine which of these combinations perform best from an acoustic perspective but also from an environmental point of view. The sound absorption qualities of these biocomposites have been investigated. It was found that the sound absorption coefficients range from 0.33 to 0.49 in the mid-high frequency range for the four different mixtures of substrate and oyster mushroom (Pleurotus ostreatus). The results from the acoustic testing are promising, but the environmental impact of these mycelium-based composites also needs to be determined. The impacts from water and especially from energy, used during the growth and preparation cycles, are the main contributors to the environmental impact of MBCs, which is also confirmed by the relevant literature. A cradle-to-grave life cycle assessment (LCA) was conducted, utilizing the ReCiPe method, with selected environmental impact categories, based on real-world production data and the scientific literature. The results obtained were also compared with a commercially produced acoustical stone wool panel. The influence on environmental impact of the different substrates is also analyzed, determining which MBC is the most environmentally friendly and has the best acoustical properties. Full article

Moisture content is a key quality attribute in dried areca nuts, affecting subsequent processing performance and storage stability, yet routine measurement by oven-drying is time-consuming and destructive. This study developed a rapid and non-destructive method for determining moisture content in dried areca nuts by integrating near-infrared spectroscopy with chemometric and machine learning-assisted methodologies. Various spectral preprocessing methods, feature wavelength selection algorithms, and modeling approaches were compared. The results indicated that Multiplicative Scatter Correction (MSC) most effectively eliminated physical scattering interference. The Partial Least Squares Regression (PLSR) model established using full-wavelength spectra demonstrated optimal predictive performance. It achieved a coefficient of determination for the prediction set (Rp²), root mean square error of prediction (RMSEP), and residual predictive deviation (RPD) of 0.9639, 0.1960, and 10.3461, respectively, indicating excellent predictive accuracy and robustness. Feature wavelength selection did not enhance model performance in this study, which can be attributed to the broad absorption bands of water in the near-infrared spectrum and its complex interactions with the sample matrix where the full spectrum data retains essential information more comprehensively. This research provides a reliable and practical technical means for moisture management in areca nuts, offering important support for quality assurance and standardized production practices within the areca industry. Full article

This study presents the results of research on the modification of gypsum with bio-waste to improve its thermal insulation properties and to evaluate the influence of the type and amount of the additive on the physical, mechanical, and microstructural properties of the composite. Various fractions of plant-based bio-waste were used in amounts ranging from 0.75 to 10% by weight. The thermal conductivity coefficient and thermal diffusivity were determined. Additionally, analyses of dimensional stability over time, visual appearance, and phase distribution uniformity were conducted. Mechanical tests included surface hardness measurements. In order to determine the material’s durability, water absorption and frost resistance tests were performed, and structural changes and properties after these cycles were analyzed. It was found that selecting the appropriate type and proportion of additive makes it possible to obtain composites with a favorable balance between thermal insulation, dimensional stability, and mechanical performance. The conducted research confirms the potential for effective use of bio-waste as a gypsum-modifying raw material, contributing to the development of sustainable building materials with a reduced environmental footprint and improved functional parameters. Full article

Integrating sphere measurements are a well-established method for determining the optical properties of planar samples. In this study, the approach was expanded from slab geometry to cylindrical geometry illuminating the cylinder barrel, thereby demonstrating its applicability for determining the optical properties of human fingers. By adapting existing integrating sphere theory to cylindrical samples, the method was systematically validated using phantoms and subsequently applied to human fingers. It has been demonstrated that the absorption coefficient ${\mu }_{\mathrm{a}}$ and the reduced scattering coefficient ${\mu }_{\mathrm{s}}^{\prime }$ of cylindrical and 3D finger phantoms can be determined with a high degree of agreement to those of slab phantoms. Moreover, this approach facilitates the quantification of tissue components in human fingers, including fat, water and collagen content, total haemoglobin concentration and tissue oxygenation. Full article

Ultrasound propagation velocity was investigated as a non-destructive predictor of open porosity (${\rho }_0$) and water absorption ($A_w$) in volcanic rocks (two ignimbrites, a trachyte, and a basalt). Six velocity measurements were obtained under dry and saturated conditions along three orthogonal directions, and the dry Z-axis velocity was selected as the reference univariate predictor because it provided the highest explanatory power and the best cross-validated performance among the tested ultrasound variables. Four univariate regressions (linear, exponential, power law, and second-order polynomial), parametric multivariable linear regression, and five machine learning regressors were compared using lithology-stratified 5-fold cross-validation, grouping both ignimbrites as a single lithology. Univariate models showed moderate predictive capability for ${\rho }_0$ (cross-validated coefficient of determination $R^2\approx$ 0.506 to 0.580), whereas $A_w$ was captured more accurately, with the power law model reaching 0.923 ± 0.008. Multivariable linear regression improved ${\rho }_0$ when lithology was included (0.803 ± 0.084), while changes for $A_w$ were small. The highest accuracy was achieved by ensemble tree methods: extremely randomized trees with lithology yielded 0.949 ± 0.015 for ${\rho }_0$ (root mean square error 2.16 ± 0.38 percentage points), and Gradient Boosting with lithology yielded 0.976 ± 0.006 for $A_w$ (0.80 ± 0.12 percentage points). Full article

This study presents the development and experimental evaluation of an impregnation composition for cement concrete pavements aimed at improving ice-phobic performance while preserving tire–pavement adhesion characteristics. The formulation is based on a combination of keratin-containing raw materials and water-soluble polymer components. Optimization showed that a polymer concentration of 2.5% reduces concrete water absorption by 49–53% compared with untreated specimens. Freezing tests conducted at temperatures of 0 to −5 °C demonstrated an additional reduction in water absorption of treated specimens by 33–40% relative to uncoated concrete and improved resistance to ice formation. The influence of the impregnation on tire–pavement interaction was assessed using a direct shear method, revealing minor changes in friction coefficients of up to ~6% for polished and less than 1% for rough surfaces, remaining within acceptable safety limits. Wear resistance was evaluated through rolling tests with model vehicle wheels, where laboratory abrasion occurred after several thousand loading cycles, while probabilistic correction accounting for trajectory variability indicated an extension of service life to the order of tens of thousands of vehicle passes. The results confirm the potential of the keratin–polymer impregnation as an effective approach for enhancing the durability and operational safety of concrete pavements in cold climates. Full article

Conventional admixture-based self-healing technologies are often limited by inadequate internal water supply and a scarcity of unhydrated gel particles. Therefore, this study proposes a new self-healing method that leverages the synergistic interplay between the chemical repair of sodium silicate and the physical clogging of superabsorbent polymers (SAPs) to overcome the aforementioned limitations. The healing efficiency of cement mortar was assessed through compressive strength recovery, capillary water absorption, and ultrasonic pulse velocity (UPV). Microstructural evolution and healing mechanisms were elucidated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicate that at an optimal dosage (0.5 wt.% for both admixtures), the healing performance is significantly enhanced: the compressive strength recovery rate reaches 103.1%, the capillary water absorption coefficient decreases by 16.57 × 10⁻³, and the UPV recovery achieves 95.4%. Microstructural analysis reveals that sodium silicate facilitates the reaction between ${\mathrm{Ca}}^{2+}$ and ${\mathrm{S}\mathrm{i}\mathrm{O}}_3^{2-}$ ions, leading to the in situ precipitation of dense C-S-H gel at the crack interface, thereby enabling chemical repair. In contrast, SAP contributes to physical sealing via a swelling and release mechanism. Full article

This study presents an improved methodology for assessing the environmental sensitivity of the host rock in Huashan art paintings. A hygroscopic experiment was first designed to determine the moisture diffusion coefficient of the rock mass preserving the Huashan rock paintings, as verified by hygroscopic kinetics. Additionally, variations in color difference values were simultaneously used to quantitatively evaluate moisture absorption characteristics. Subsequently, a finite element (FE) simulation was conducted to assess potential damage to the rock art system with respect to varying environmental conditions. Regarding the correlated functions with consideration of the influencing factors, the environmental sensitivity of the host rock in Huashan art paintings was clarified to illustrate the deterioration process resulting from the combined effects of temperature and humidity. It is found that the deformation gradient (F) and maximum tensile stress (σ_max) exhibit a linear relationship with ambient temperature (T_a), and an exponential relationship with heat transfer coefficient (h). The ambient humidity (H_en) and surface humidity exchange coefficient (f) primarily influence the water content of the rock mass. This insight into the host rock in Huashan art paintings provides a valuable approach to highlight the active role of environmental conditions and offers an additional methodology to understand the detachment of large superficial rock flakes and the granular disintegration of the rock. Full article

In this study, by using four different silicon sources obtained from Konya, Turkey, and its surroundings and employing the sol–gel method, we aim to synthesize silica-based aerogel, characterize it, and improve the use of the innovative building material as a thermal insulator in architectural applications. In this direction, silica aerogel production was carried out using four different starting materials (commercial casting sand, waste casting sand, radiolarite, and quartz) and five different pH values (2–4–6–8–9) by the sol–gel method. The produced silica aerogels were subjected to a surface modification process with Trimethylchlorosilane (TMCS), a modification chemical, and then superhydrophobic silica aerogel powder was obtained. In terms of characterization of the obtained final silica aerogels, XRF, XRD, ICP-OES, density study, FT-IR, BET, FESEM, and contact angle studies were performed. In terms of application of the architectural building material, plasterboard experimental samples were produced using low reinforcement rates (0 wt%, 0.5 wt%, 1 wt%, 2 wt%, and 5 wt%) of silica aerogel. To determine the mechanical and physical properties of the produced silica-aerogel-reinforced plasterboard samples, three-point bend (flexural) strength, compressive strength, thermal conductivity, and water absorption tests were applied. After surface modification, the lowest density value was 0.340 g/cm³, the highest surface area was 311.161 m²/g, and the lowest thermal conductivity coefficient was 0.29 W/mK in silica aerogel material containing radiolarite. In addition to high reinforcement contents in the literature, when it comes to silica aerogel low-reinforcement material and mechanical properties, it can be stated that increasing reinforcement contents negatively affects the mechanical behavior of the material after a certain value. Full article

A composite meeting the UL94 V-0 rating was produced by adding 30 wt% epoxy silane-modified aluminum trihydrate (EPATH) to a 60/40 epoxy/benzoxazine matrix. Various bimodal and trimodal composites containing 20–40 wt% of three types of ceramic fillers, i.e., aluminum oxide (Al₂O₃), boron nitride (BN), and magnesium oxide (MgO), were prepared to simultaneously achieve flame-retardant and thermal conductive properties. The bimodal composites with 40 wt% of Al₂O₃ and MgO exhibited thermal conductivities of 1.22 W/m∙K and 1.29 W/m∙K, respectively, which were superior to that of the composite containing the same amount of ATH (1.0 W/m∙K). In contrast, both the coefficient of thermal expansion (CTE) and shear strength decreased with increasing ceramic filler content. For agglomerated BN, the filler loading was constrained above 30 wt% because its high specific volume caused a significant rise in the viscosity. In the trimodal composites with a total filler content of 40 wt% of Al₂O₃ and BN, a BN fraction of 7.5 wt% yielded the highest thermal conductivity of 1.64 W/m∙K and the lowest water absorption of 0.69%. When the trimodal composites were exposed to −55 °C and 150 °C for 1000 h, they exhibited a reduction in shear strength of less than 30% compared to their initial values. Full article

The interaction between plasmonic nanoparticles and organic dye molecules plays an important role in varied photonic and optoelectronic applications. In this work, we systematically investigate the optical properties of a water-soluble perylenediimide derivative, N,N′-di(2-(trimethylammonium iodide) ethylene) perylenediimide (TAIPDI), in the presence of different concentrations of silver nanoparticles (AgNPs) under femtosecond (fs) laser excitation. The AgNPs were synthesized via the laser ablation technique. The influence of AgNP concentration on the linear, fluorescence, and nonlinear optical properties of the TAIPDI dye was explored through UV–visible absorption spectroscopy, fluorescence emission measurements, and open- and closed-aperture Z-scan techniques. The Ag NP–TAIPDI dye hybrid systems (Ag@TAIPDI nanocomposites) exhibited pronounced reverse saturable absorption and self-defocusing behavior, indicating a negative nonlinear refractive index. Both the nonlinear absorption coefficient and refractive index increased markedly with rising AgNP concentration, leading to a significant enhancement in the third-order nonlinear susceptibility. Fluorescence studies further revealed a concentration-dependent emission enhancement due to metal-enhanced fluorescence arising from surface plasmon resonance-induced local field amplification. The Ag@TAIPDI nanocomposites also demonstrated strong optical limiting performance, with the limiting threshold decreasing as the AgNP concentration increased. These findings highlight the synergistic role of plasmon–exciton coupling and thermal lensing in enhancing the nonlinear response of such nanocomposites. The results establish AgNPs–TAIPDI dye hybrid systems as promising materials for all-optical switching, optical limiting, and photonic device applications. Full article

The anti-seepage performance of concrete directly affects the anti-seepage effect and durability of the concrete face slab of the rockfill dam. Since the panel concrete is often in a complex stress state in practical engineering, its permeability coefficient will be significantly affected by the stress state. In this paper, the fixture is designed to apply different levels of axial compression and axial tensile load to concrete specimens, and the air-void structure, water absorption, and permeability coefficient are measured under sustained load. The results show that with the increase in axial compressive load, the air-void spacing, capillary water absorption and permeability coefficient decrease first and then increase, and the critical stress threshold is 0.38 f_c. For the specimen with a water-cement ratio of 0.35, the permeability coefficient decreases by 45.1% and then increases by 802.4%. However, when the axial compressive load exceeds a certain threshold, the internal structure is damaged, and the permeability increases again. With the increase in axial tensile load, the air-void spacing, capillary water absorption, and permeability coefficient continue to increase, indicating that axial tensile stress will aggravate the expansion of micro-cracks in concrete and significantly increase the permeability coefficient. For the specimen with a water-cement ratio of 0.35, the permeability coefficient increases by 197.9% and then increases by 734.3% with the increase in tensile stress. The concrete with a water-cement ratio of 0.5 is more sensitive to the change in stress state than 0.35, showing a greater change in permeability coefficient and capillary water absorption. The research can provide an important basis for the design and construction of concrete face rockfill dam panel. Full article

Cyanobacterial blooms pose a serious threat to freshwater ecosystems, necessitating accurate remote sensing monitoring. Although red-edge bands show potential in terrestrial monitoring, their multi-dimensional features (i.e., spectral, textural, and index-based characteristics) remain underutilized for aquatic blooms. This study leverages the dual red-edge bands (710 nm and 750 nm) of GF-6/WFV to enhance cyanobacterial bloom identification in Lake Taihu. Multi-temporal images from 2019–2023 were used to construct red-edge features in three dimensions: spectral (evaluated via adaptive band selection method) and Jeffries–Matusita–Bhattacharyya distance), texture (based on Gray Level Co-occurrence Matrix and principal component analysis), and indices (nine vegetation indices ranked by Random Forest importance). Twelve feature-combination schemes were designed and implemented with a Random Forest classifier. Results show that red-edge features consistently improve identification accuracy. Quantitatively, compared to the basic four-band (RGBN) combination, the 710 nm band improved spectral separability by an average of 9.63%, whereas the 750 nm band yielded a lower average improvement of 5.69%. Red-edge indices, especially the modified chlorophyll absorption reflectance index 1 (MCARI1) and normalized difference red-edge index (NDRE), exhibited higher importance than non-red-edge indices. All schemes incorporating red-edge features achieved mean overall accuracies of 92.8–94.9% and Kappa coefficients of 0.86–0.94, surpassing the basic four-band scheme. Among these features, red-edge indices contributed most significantly to accuracy gains, increasing the overall accuracy by an average of 0.36–6.06% and the Kappa coefficient by up to 0.06. The enhancement effect of the red-edge 710 nm band features was superior to that of the 750 nm band. This study demonstrates that multi-dimensional red-edge features effectively enhance the identification accuracy of cyanobacterial blooms and provides a methodological reference for operational GF-6 applications in water quality monitoring. Full article