Search Results (8,788)

Multispectral LiDAR can simultaneously obtain distance and spectral information and shows great potential for underwater detection. However, absorption and scattering caused by suspended particles in water lead to energy attenuation and multiple scattering, which affect echo intensity and ranging accuracy, while the propagation characteristics under multi-wavelength conditions remain insufficiently studied. In this study, a simplified underwater propagation simulation model for multispectral LiDAR is established based on the equivalent spherical-particle assumption, combining Mie scattering theory with a semi-analytical Monte Carlo method. The effects of particle size on echo intensity and ranging error are analyzed under fixed concentration conditions. Based on this model, a detection-threshold-constrained optimal wavelength selection criterion is formulated. Multi-distance analysis (3, 5, 8, and 15 m) confirms that the preferred wavelength is primarily governed by particle size and remains stable across depths. The results show that the optimal detection wavelength shifts with particle size, being about 560 nm for fine particles and gradually moving toward the 400–480 nm blue–green band for larger particles. Experimental validation shows that the simulation-based ranging correction reduces RMSE by 9.4–25.9% (average 18.1%) and MAE by 11.8–29.7% (average 22.0%) across five experimental distances. The results provide a preliminary reference for wavelength selection in multispectral LiDAR systems under simplified conditions. Full article

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

Using solid waste as supplementary cementitious materials (SCMs) is an effective strategy for promoting low-carbon construction development. However, single or binary systems often exhibit mismatched reaction kinetics, thereby limiting their performance at high cement replacement rates. This study focuses on a novel low-carbon concrete designed based on reaction sequence coordination, containing recycled brick powder (RBP), ground granulated blast-furnace slag (GGBS), and self-combusting coal gangue (SCCG). The effects of RBP, GGBS, and SCCG on the hydration process and microstructure of the novel low-carbon concrete with different replacement levels have been studied by testing compressive strength, workability, and durability and observing microstructural changes. The results showed that an optimized ternary composition with an RBP:GGBS:SCCG ratio of 4:3:1 achieves a cement replacement level of 30% while exhibiting a 28-day compressive strength of 38.26 MPa, representing a 14.2% increase compared with plain cement mortar. Microstructural analyses indicate that this enhanced performance results from a time-dependent reaction sequence, in which GGBS contributes predominantly at early ages by supplying calcium, whereas RBP and SCCG mainly participate through delayed pozzolanic reactions and pore refinement at later ages. Consequently, the optimized ternary mortar exhibits a water absorption of 11.12% and a 27.2% reduction in electrical flux. This study aims to provide practical strategies for enhancing the performance of low-carbon cementitious materials through a reaction sequence coordination design approach, thereby improving the utilization efficiency of solid waste in the production of low-carbon building materials. Full article

Polyester resin biocomposites containing biochar have attracted attention for improving mechanical strength and thermal stability while promoting sustainability. The pyrolysis temperature of biochar and its proportion in the polymer matrix are key factors affecting biocomposite performance. This study examined how biochar pyrolysis temperatures (400, 600, 800 °C) and incorporation levels (10, 20, 30 wt.%) influence the physical, chemical, mechanical, flammability, and morphological properties of polyester-based biocomposites. The samples were analyzed for density, water absorption, FTIR, XRD, flexural and tensile strength, ignition time, structural degradation, volumetric loss, and SEM microstructure. Biocomposites with 30 wt.% biochar produced at 800 °C showed the best mechanical properties, with a flexural strength of 95.3 MPa and an elastic modulus of 4417.4 MPa, representing increases of 14.5% and 45.7%, respectively, over the control. FTIR and XRD results revealed decreased aliphatic groups and increased aromaticity at higher pyrolysis temperatures, improving interactions between the matrix and biochar. These biocomposites also demonstrated enhanced thermal stability, with an ignition time of approximately 963 s, delayed structural degradation, and reduced volumetric loss (~19.3%). Overall, pyrolysis temperature and biochar content significantly influence the structural, mechanical, and thermal properties of polyester biocomposites, showing that biochar serves as a sustainable, performance-enhancing component in thermoset polymer matrices. Full article

Artificial composite stones have recently attracted attention as multifunctional materials for construction and defense-related applications. In this study, a novel composite stone was developed using waste limestone as the primary mineral filler, combined with an unsaturated polyester resin matrix and reinforced with glass powder and chopped glass fibers. The influence of binder content and reinforcement type on physico-mechanical and microstructural behavior was investigated. Experimental characterization included water absorption, compressive strength, abrasion resistance, acid resistance, and optical microscopy. The results demonstrated that fine fillers improved matrix densification and reduced porosity, while short glass fiber reinforcement enhanced load-bearing capacity. Abrasion resistance and durability were found to depend on binder content and particle packing characteristics. Overall, the developed composite material exhibits promising mechanical performance, low water absorption, and improved durability, suggesting its potential as a candidate material for applications requiring environmental resistance, including potential use in defense-related camouflage applications. Full article

This study investigates the influence of waste-based materials, namely drinking water treatment sludge (DWTS) and expanded glass production waste (EGPW), on the properties of fine-grained concrete when used as partial Portland cement replacements. Fine-grained concrete mixtures containing different proportions of DWTS and EGPW were evaluated in terms of hydration behavior, microstructural development, mechanical performance, durability, and dimensional stability. Density, ultrasonic pulse velocity, water absorption, flexural and compressive strengths, drying shrinkage, and porosity parameters were determined, while frost resistance was assessed and predicted based on porosity characteristics. Hydration kinetics were analyzed using X-ray diffraction and semi-adiabatic calorimetry. The results showed that increasing EGPW content enhanced cement hydration processes and promoted matrix densification through pozzolanic reactions, resulting in reduced water absorption and improved mechanical properties. In contrast, DWTS exhibited an inhibiting effect on hydration due to its inert nature and high Fe₂O₃ content, acting primarily as a micro-filler; however, when combined with EGPW at moderate dosages, DWTS contributed positively to flexural strength and slightly reduced drying shrinkage. The combined use of DWTS and EGPW enabled the formation of a balanced pore structure and improved the durability of fine-grained concrete. Among the tested mixtures, ED-3 (7.5% EGPW + 5% DWTS) provided the most favorable balance between hydration activation and binder reduction, while the highest frost resistance was achieved by the ED-4 mixture, reaching approximately 603 predicted freeze–thaw cycles. Overall, the results indicate that properly optimized combinations of EGPW and DWTS can significantly enhance the performance and durability of fine-grained concrete while controlling drying shrinkage. Full article

The limited availability of high-quality timber and the increasing demand for wood-based panels have encouraged the exploration of alternative and sustainable lignocellulosic resources. Rattan waste is abundant in Indonesia; however, its low mechanical strength and limited durability restrict its direct application in composite materials. This study investigated the effect of furfuryl alcohol (FA) modification and different adhesive systems on the performance of rattan-based particleboard. Rattan particles were immersed in FA for 24 h and used to produce particleboards (300 × 300 × 10 mm) bonded with phenol formaldehyde (PF), melamine formaldehyde (MF), and urea formaldehyde (UF) adhesives at a resin content of 12%. The boards were manufactured under controlled hot pressing conditions and conditioned for 14 days prior to testing. Furfurylation significantly improved dimensional stability by reducing moisture content, water absorption, thickness swelling, and leaching, with anti-swelling efficiency values ranging from 43.25% to 71.06%. Some selected mechanical properties, including internal bonding strength, hardness, and screw holding power, were also enhanced. However, the modification showed limited influence on the modulus of elasticity and, in some cases, reduced the modulus of rupture. Among the adhesive systems, MF-bonded boards exhibited the most balanced mechanical performance. Furfurylation also produced darker and more uniform board surfaces. These findings indicate that furfurylated rattan particleboards are suitable for non-structural and decorative applications. Full article

This study evaluates the performance of foamed geopolymer concrete (FGC) incorporating rigid polyurethane (PU) waste as a partial sand replacement and aluminum powder (AP, 1%) as a foaming agent. The mixtures were based on metakaolin, fly ash, and silica fume. Fresh and hardened properties were assessed, including workability, setting time, density, compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption, porosity, gas permeability, and chloride ion penetration. Microstructural characteristics were examined using scanning electron microscopy (SEM). The results show that moderate PU incorporation significantly enhances mechanical performance. The optimal mixture (PU30) achieved a compressive strength of 47.25 MPa at 180 days, representing a 15.6% increase compared to the control. Flexural and splitting tensile strengths improved by 19.9% and 16.7%, respectively, while the elastic modulus increased by 33.8% to 0.95 GPa. These improvements are attributed to enhanced particle packing and more efficient stress transfer within the matrix. In contrast, higher PU contents (>30%) reduced mechanical performance due to increased total porosity and weakened interfacial bonding. Durability-related properties indicated that mixtures PU20–PU30 exhibited reduced permeability and optimized pore structure, characterized by lower pore connectivity. SEM observations confirmed a denser matrix with uniformly distributed pores at optimal PU levels. Additionally, the integration of Random Forest regression with GLCM-based texture analysis demonstrated strong capability in predicting mechanical properties from SEM images. Overall, the combined use of PU waste and AP enables the production of lightweight, structurally efficient, and sustainable FGC with improved mechanical and durability performance. Full article

Targeting the long-term goal of synchronous acquisition of underwater terrain and material composition information, this study establishes a radiative transfer model for underwater hyperspectral LiDAR (UDHSL) and systematically verifies the effects of target reflectance, detection distance, and laser wavelength on backscattering echo intensity through controlled laboratory experiments. A wavelength-dependent water attenuation correction term incorporating absorption and scattering was introduced into the conventional LiDAR equation to derive a hyperspectral LiDAR radiative transfer equation applicable to underwater environments, and a normalized echo intensity processing method using window glass reflection as a reference was proposed. This study uses a custom-built UDHSL system (wavelength range: 450; detection range approximately 5–6 m). The echo intensity exhibits pronounced wavelength selectivity, peaking at 450–550 nm in clear water and shifting to 530–570 nm in turbid water. These experimental results are consistent with theoretical predictions of the radiative transfer model, validating its fundamental correctness and providing an experimental basis for radiometric calibration and underwater target reflectance retrieval of UDHSL systems. Full article

This study addresses the optimal scheduling of a proton exchange membrane fuel cell (PEMFC)-based building combined cooling, heating, and power (CCHP) system, aiming to improve operational efficiency and flexibility under coupled electricity–thermal–cooling demands and load uncertainty. A physics-informed scheduling environment was developed using component models and multi-energy balance constraints, including a PEMFC with waste-heat recovery, a lithium bromide absorption chiller, a reversible heat pump with condenser heat recovery to thermal storage, a battery energy storage system, and a hot-water thermal storage tank. The dispatch problem was formulated as a Markov decision process and solved using deep reinforcement learning with TD3; performance was evaluated on typical summer and winter days, and robustness was tested by generating 100 scenarios with 30% demand perturbations. The results show that TD3 learns coordinated multi-energy dispatch patterns consistent with seasonal operation and reduces hydrogen consumption relative to a rule-based strategy under uncertainty while requiring millisecond-level inference time. Dynamic programming achieved slightly lower hydrogen consumption but incurred orders-of-magnitude higher computation time. Overall, TD3 provides a practical trade-off between near-optimal performance, robustness, and real-time applicability for PEMFC-based building CCHP scheduling. Full article

In this study, the characteristics of concretes made from mixed recycled aggregate—the cheapest and most common secondary raw material in construction and demolition waste—were determined. For this study, besides experimental concretes using mixed recycled aggregate, reference compositions were developed using river gravel, recycled concrete aggregate, and recycled masonry aggregate. The workability of concrete mixtures was measured as class S1, which is acceptable for use with slipform concrete pavers, and was achieved by varying the water/cement ratio, considering the different water adsorptions of the concrete fillers. The following mechanical characteristics of the concretes were defined on the 3rd and 28th days: density, compressive strength, flexural strength, water absorption, and frost resistance. The test results showed sufficiently high indicators of strength and durability for the recycled aggregate concretes. Moreover, the strength of the concrete developed from mixed recycled aggregate was comparable with that of the reference concretes. Considering the low strength requirements for the construction of the lower layers of rigid pavements, it was established that such an application of recycled aggregate concrete, including that derived from mixed recycled aggregate, could be permitted. Full article

This study investigates the development and optimization of a multi-component modifying additive based on industrial waste for improving the mechanical and durability properties of concrete. The additive consists of microsilica (Ms), phosphogypsum (PhG), soapstock (Sp), and post-alcohol bard (PaB), and its performance was evaluated using a staged experimental approach. The results showed that the optimal content of microsilica is 20% of the cement mass; the optimal content of phosphogypsum is 15% of the combined mass of the cement and microsilica; the optimal content of soapstock is 10% of the total mass of the cement, microsilica, and phosphogypsum; and the optimal post-alcohol bard is 5% of the water mass. At these concentrations, the compressive strength increased by up to 28.3% compared to the reference sample. Soapstock significantly reduced water absorption (up to 36.8%) and improved freeze–thaw resistance due to the hydrophobization of the cement matrix. However, excessive soapstock content led to a reduction in strength. The addition of post-alcohol bard provided a plasticizing effect and reduced water absorption, with the optimal concentration for strength being 2.5%, while the highest freeze–thaw resistance was observed at 5%. The combined effect of the components resulted in the formation of a denser microstructure and improved durability of concrete. These findings demonstrate the effectiveness of industrial waste-based additives in enhancing concrete performance and durability, contributing to sustainable material development. 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

Adobe is a sustainable yet highly porous construction material, inherently vulnerable to moisture and environmental pollution, which poses challenges for both contemporary construction and heritage conservation. This study presents multifunctional coatings that combine hydrophobic/oleophobic and photocatalytic properties to enhance adobe durability. The coatings incorporate nano-heterostructured LaFeO₃ photocatalysts into water-repellent and hydro-oleo-repellent formulations, selected to preserve the characteristic dark brown color of adobe. Microstructural analyses revealed the formation of non-uniform protective layers, particularly in hydro-oleo-repellent systems, which influenced performance. The treated surfaces exhibited significant water and oil repellency, while maintaining adequate vapor permeability. Durability tests confirmed improved resistance to water ingress, reduced capillary absorption, and enhanced erosion resistance compared to untreated adobe. Sustainability assessments highlighted the environmental and economic benefits of the proposed approach, especially when using locally sourced materials. Overall, this work proposes a scalable and multifunctional strategy that integrates protective and photocatalytic functionalities to extend the service life of both historical and modern adobe structures. Full article

Fibrin gel, a protein-based polymer naturally generated during coagulation, has garnered attention in the biomedical field for applications such as fibrin glue, due to its specific physical and biological properties. Despite it, low mechanical strength and rapid degradation limited its utilization for biomedical applications. This study presents a reproducible protocol for the synthesis of pure fibrin hydrogels, aimed at achieving predictable structural properties through the precise calibration of fibrinogen and thrombin concentrations. By examining the mechanical and morphological characteristics, as well as the relationship between reagent concentrations and structural integrity, this research assesses impacts on swelling behavior, water absorption, and overall stability. Through a comprehensive analytical approach, we identified an optimal formulation, specifically 2.25 mg/mL fibrinogen and 1.375 U/mL thrombin, that effectively balances structural integrity with high cytocompatibility. The results demonstrate that this calibrated approach ensures high procedural reproducibility and a well-defined hydrogel architecture without the need for exogenous chemical cross-linkers. This work provides a robust methodological framework to overcome the common lack of reproducibility in fibrin-based hydrogel studies, positioning these materials as highly reliable candidates for advanced 3D in vitro models and biomedical applications. Full article