Search Results (1,428)

Polarized side-scattering techniques are widely used in aerosol detection, oceanographic optics, and biomedical sensing due to their high sensitivity to weak optical signals in low-scattering coefficient media. Conventional polarized Monte Carlo methods face significant challenges in such regimes due to geometric mismatch, where photon exit positions deviate substantially from the detector plane. This study addresses the geometric mismatch issue in polarized Monte Carlo simulations for side scattering in low-scattering media (scattering coefficient ${\mu }_s=$ 1 cm⁻¹), where photon exit positions often deviate from the detector plane. We propose a novel algorithm incorporating backward ray tracing with geometric projection correction to enhance simulation accuracy. Experimental validation was conducted using 532 nm laser illumination on both 500 nm polystyrene microspheres (${\mu }_s=$ 0.21 cm⁻¹) and 5 nm TiO₂ nanoparticles (${\mu }_s=$ 1.06 × 10⁻⁶–1.06 × 10⁻⁵ cm⁻¹). The results demonstrate excellent agreement between simulations and experiments, confirming the algorithm’s capability to accurately capture the polarization characteristics of side-scattered light. This work provides a high-fidelity simulation tool for designing optical sensors in low-scattering media and holds direct applicability in nanoparticle concentration sensing and aerosol monitoring. Full article

Virtual plant models combined with ray-tracing simulations are an established tool for evaluating plant–light interactions. Current approaches often simplify leaf surface properties by assuming diffuse reflectance behavior, despite experimental evidence that leaf reflectance is direction-dependent across much of the visible spectrum. This study investigates whether incorporating measured, spectrally resolved and direction-dependent (BRDF) reflectance properties into these models affects simulation outcomes. Using virtual 3D cucumber (Cucumis sativus) plant models with PhongShader-based optical leaf characteristics for BRDF consideration, light absorption and local photon flux densities were simulated under a wide range of lighting conditions, including diffuse and directed sunlight scenarios. While total light absorption at the leaf level is only marginally affected (mean absolute percentage error, MAPE < 2%), spectral distortions in leaf surroundings, especially under direct light, exceeded 8% in the blue wavelength range. Beyond their relevance for estimating photosynthetic rates, such distortions directly affect the spectral composition within the canopy, which is particularly critical in greenhouse applications where optical sensors are used to monitor spectral ratios and, therefore, require the accurate prior simulation of canopy light conditions. This is particularly relevant for setups with directional artificial lighting. The findings suggest that BRDF modeling is not critical for calculating photosynthetic rates under most conditions, but is required in spectral analyses or for optimizing artificial lighting designs. Full article

Data-centric approaches are increasingly shaping wireless communication research, where the availability and quality of datasets directly influence the reliability of learning-based and model-driven methods. In this context, unmanned aerial vehicle (UAV) communication poses unique challenges, as it requires datasets that jointly capture geometric information, propagation conditions, and diverse link configurations. This work introduces a geometry-aware UAV communication dataset designed to support research on controlled UAV communication link directions and propagation scenarios. The dataset is generated using standardized 3GPP and ITU-R channel models across multiple urban, suburban, and rural regions, accounting for variations in altitude, carrier frequency, and node distribution. The dataset provides spatially resolved channel parameters along with geometry-rich files containing environmental features, which can be used to extract relevant parameters for UAV communication studies. These data support reproducible research in geometry-aware channel modelling, path-loss prediction, LOS/NLOS analysis, delay-related modelling, and trajectory-conditioned link-quality analysis. Full article

Parabolic trough collectors (PTCs) are highly sensitive to receiver positioning accuracy; however, most existing studies report optical efficiency degradation without formally defining alignment tolerance limits. This study proposes a tolerance-based thermo-optical risk framework to quantify allowable receiver misalignment envelopes for reliable PTC operation. A Monte Carlo Ray Tracing (MCRT) methodology is employed to evaluate the impact of angular receiver misalignment on optical efficiency and circumferential heat flux redistribution. Beyond conventional efficiency metrics, normalized flux-based thermal non-uniformity indicators are introduced to assess thermo-mechanical risk without requiring full thermo-fluid modeling. The results reveal a nonlinear decoupling between optical acceptability and thermal safety. While optical efficiency remains above 0.80 up to approximately ±6°, pronounced flux localization and rapid growth of thermal stress indicators occur beyond ±4°, marking the onset of thermally critical behavior. The identified ±4° threshold corresponds to approximately twice the collector half-acceptance angle (θ_(crit)/δ ≈ 2), demonstrating geometry-dependent scaling characteristics. The proposed framework formalizes the optical–thermal decoupling phenomenon and transforms conventional efficiency-based evaluation into a reliability-informed alignment tolerance assessment tool applicable to manufacturing precision, installation control, and operational quality management in CSP systems. Full article

Trace quantifications of arsenic (As) in foods by energy-dispersive X-ray fluorescence (ED-XRF) spectrometry are hindered by spectral overlap from lead (Pb) at characteristic emission lines. This study employed artificial neural networks (ANN) to statistically model and correct for As/Pb spectral overlap, enabling accurate As quantifications in rice-based foods. Calibration standards were prepared by pelletizing milled rice spiked with As and Pb, and validation was performed using a certified reference material, commercial rice-based foods, and Pb-spiked commercial foods. As calibration metrics were great (R² = 0.92, standard error in calibration = 41.20 µg kg⁻¹). The validation assessment achieved acceptable error using the As reference material (−19.43% error) and in commercial rice-based foods containing low Pb content (6 of 11 As determinations in agreement with the reference method). Additionally, accurate predictions of As were found in the presence of significant Pb interference (absolute mean error = 14.11% in Pb-spiked commercial foods). Overall, ANN modeling for Pb exhibited poor performance during both calibration and validation. This work demonstrates the usability of an ANN to address the As/Pb overlapping issue while offering insights into the strengths and weaknesses of ANNs when coupled with ED-XRF for trace elemental quantifications in foods. Full article

Photovoltaic thermal concentration has emerged as a method to enhance the energy efficiency and performance of photovoltaic installations. This approach addresses the growing demand for renewable energy aimed at reducing emissions and mitigating climate change. It represents a significant solution for applications requiring both thermal and electrical energy under constraints of a limited available area for solar energy harvesting. However, currently developed devices rely on expensive photovoltaic cells, incorporate complex geometries that are difficult to manufacture and maintain, and employ tracking systems that complicate interconnection with similar units. The objective of this study is to design and numerically evaluate a hybrid thermal–photovoltaic modular linear Fresnel solar concentrator (H-MLFRC) based on commercial silicon cells. The proposed system allows series and parallel interconnection and is suitable for both islanded and grid-connected configurations. Its development was guided by integrated optical, photovoltaic, and thermal analyses, which defined the system geometry, characteristic parameters, and operating conditions. The results indicate that the maximum operating temperature of the device is 70 °C under a nominal operating mass flow rate of 0.45 kg/s. Additionally, the thermal and photovoltaic efficiencies are 49% and 16%, respectively, resulting in a combined efficiency of 65%. Full article

Accurate identification and spatial localization of hidden hazards in embankments are essential for the reinforcement and safety management of defective structures. However, conventional drilling and single geophysical methods are often insufficient for fine-scale detection due to the strong heterogeneity of embankment materials, complex internal structures, and diverse forms of leakage-related defects. To address these challenges, this study establishes conceptual models for two representative embankment types, namely homogeneous embankments and core-wall embankments, based on reflection-wave imaging theory. The propagation characteristics and imaging responses of reflection waves in embankment media are systematically investigated. A forward-modeling approach based on the shortest-path ray tracing method is developed, and reflection-wave imaging is achieved through travel-time tomography inversion. The diagnostic results show that the proposed reflection-wave imaging method can effectively delineate the spatial distribution and geometric morphology of internal defects, demonstrating strong capability in identifying leakage channels and loose zones. The research provides a theoretical basis and technical support for nondestructive detection and comprehensive diagnosis of embankment hazards. Full article

The concentration of heavy metals in the environment has been steadily increasing, raising concerns about their adverse effects on ecosystems and human health. Fine-grained particulate matter is of particular concern due to its enhanced mobility, bioavailability, and potential for inhalation exposure. Facilities involved in the mechanical processing of electronic waste (e-waste) represent a significant potential source of metal-containing fine particles. In this study, crushed e-waste components containing precious metals were separated into particle-size fractions ranging from 3.0 to 0.15 mm using a vibratory sieving system. The elemental composition of the individual fractions was determined by energy-dispersive X-ray fluorescence spectrometry (ED-XRF), while the spatial distribution of selected metals in fine fractions was further investigated using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM–EDS). The results demonstrate that e-waste contains a wide range of heavy non-ferrous metals whose distribution is strongly dependent on particle size. A pronounced enrichment of metals was observed in the finest fractions, particularly below 0.25 mm. Compared to the coarse fraction (>3 mm), the zinc concentration increased by approximately one order of magnitude, while chromium, nickel, and cadmium exhibited increases of up to approximately 20-fold. Lead showed particularly high enrichment, reaching approximately 2 wt.% in the finest fraction (<0.15 mm), corresponding to nearly fiftyfold enrichment relative to the coarse fraction. Tin concentrations also increased markedly, in some cases by up to two orders of magnitude. Trace amounts of arsenic and selenium were detected in the finest fractions, whereas mercury was not detected. The combined ED-XRF and SEM–EDS results confirm that fine-grained e-waste fractions are the dominant carriers of hazardous metals and respirable particles generated during mechanical processing. These findings highlight the dual character of fine fractions as both a critical environmental and occupational risk and a potentially valuable secondary resource. The study emphasizes the importance of controlled handling, effective dust management, and targeted processing strategies to minimize human exposure while enabling efficient recovery of valuable metals from e-waste. Full article

The modification of road bitumen using micro-sized carbonaceous materials offers a promising route to enhance pavement performance; however, the influence of microdispersed coke derived from coal and petroleum sources has not been sufficiently clarified. In this study, coal and petroleum coke from Pavlodar Petrochemical Plant LLC (Pavlodar, Kazakhstan) were mechanochemically activated and used as the modifiers for BND 100/130 bitumen, produced by Asphaltbeton 1 LLC (Almaty, Kazakhstan). X-ray diffraction and scanning electron microscopy were used to determine the structure and morphology of the resulting coke powders. Standard tests and the Superpave Multiple Stress Creep and Recovery (MSCR) methodology were used to determine the physico-mechanical and rheological properties of the modified binders. Microdispersed granular coke powders produced after mechanochemical activation had a minimum average particle diameter of 8.28 µm (petroleum coke) and 16.64 µm (coal coke), and were mainly an amorphous carbon phase with traces of graphite. Addition of 1 wt.% microdispersed coke resulted in better performance of binder and an enhancement in grades of BND 100/130 to BND 70/100, in line with ST RK 1373-2013. MSCR testing showed that Jnr_3.2 is between 2.0–3.0 kPa⁻¹, which is in the S category of AASHTO M 332-20. This study showed how micro-sized coal and petroleum coke can be effectively used as a high-carbon modifier in bitumen, which reflects the possibility of their practical use in asphalt pavements that are subjected to normal traffic conditions. Full article

Abnormal refraction phenomena such as atmospheric ducts due to temperature inversions or rapid decreases in humidity often happen in the lower troposphere over the sea and coastal area, which can make low-elevation signals in the duct layer propagate beyond the horizon, and the ray trajectories extend horizontally over long distances. This paper uses ray tracing technology based on a second-order Taylor approximation to accurately predict the low-elevation ray trajectories within atmospheric ducts. The meteorologic parameters at the heights traversed by the rays are extracted to accumulate atmospheric absorption attenuation by line-by-line calculations, and a high-precision prediction method for atmospheric absorption attenuation in over-the-horizon propagation links is established; meanwhile, we also implement visualization of atmospheric absorption attenuation changes along the ray trajectories in atmospheric duct environments. By comparing the results of the atmospheric absorption attenuation models for horizontal terrestrial paths in the ITU-R P.676 recommendation and GJB Z87-1997 in atmospheric duct environments, we found that the high-precision model proposed in this paper can improve the prediction accuracy of atmospheric absorption attenuation by about 15% in surface ducts and 28% in elevated ducts, significantly improving the propagation performance of low-elevation signals under atmospheric ducts and other abnormal refraction conditions for electronic systems such as surveillance, detection, communication, and navigation. Full article

This study investigates four rock–soil profiles developed from Proterozoic intermediate–acid rocks in the Maoniushan area of Xichang, Sichuan Province. Through systematic geochemical analysis of major and trace elements and X-ray diffraction analysis of clay minerals, we aim to clarify the dominant controlling factors and environmental response mechanisms of chemical weathering under similar lithological and soil-forming age conditions. The results indicate the following: (1) Major element geochemistry shows that the Chemical Index of Alteration (CIA) of all profiles ranges from 61 to 74, while Na/K ratios and A-CN-K diagrams collectively reveal that the profiles are in a transitional stage from weak weathering (Ca and Na depletion) to moderate weathering (K depletion), with the weathering intensity ranking in the order TP1711 > TP1709 > TP1714 ≈ TP2801. (2) Trace elements exhibit significant differences among profiles: Cu, Zn, and Pb are significantly leached relative to Al₂O₃ in the TP1711 profile, whereas most trace elements are enriched in the TP1714, TP1709, and TP2801 profiles. Variations in ∑LREE/∑HREE ratios further support differences in the weathering stages of the profiles. (3) The clay mineral assemblages are dominated by illite, chlorite, and vermiculite. The TP1714 profile lacks vermiculite and has the highest illite content (54–60%), reflecting a relatively cold and dry local microclimate. In contrast, the other profiles show widespread vermiculite development, accompanied by minor kaolinite, indicating moderate weathering intensity under warm and humid climatic conditions. This study confirms that under similar lithological and soil-forming age conditions, the microclimatic differentiation induced by altitude variation is the key external controlling factor leading to spatial differences in the chemical weathering intensity of granite–soil profiles in the Maoniushan area. Full article

This study investigates radio-frequency signal propagation in underground metro tunnels with a focus on distributed antenna system (DAS) deployment. Deterministic simulations were performed using Altair WinProp 2024.1 (ProMan) with a 3D ray-tracing engine (GO + UTD) at 2.4 GHz in a reinforced concrete tunnel model of 900 m length. Two antenna configurations (B3: 8 dBi directional; B8: 5 dBi wide-beam) were evaluated under identical geometric and material conditions. Results show that path loss varies from 42 to 65 dB over 850 m, with estimated attenuation exponents lower than free-space values due to quasi-waveguide effects. The B3 configuration provides higher near-field received power (up to −7.5 dBm) but exhibits stronger attenuation over long distances. In contrast, the B8 configuration ensures a more uniform spatial power distribution and a reduced path-loss growth rate beyond 500 m. The findings confirm that antenna radiation pattern significantly influences underground communication performance and demonstrate the engineering suitability of distributed antenna systems for stable metro tunnel coverage. Full article

Neural interfaces created using thin-film fabrication rely primarily on conductive metal traces for electrical interconnects. Here, we explore the use of tantalum (Ta) metal interconnects as a replacement for noble-metal interconnects such as Au, Pt or Ir. Ta has been investigated previously for interconnect metallization in flexible silicon ribbon cables, but the structure and properties of tantalum for neural device metallization have not been extensively reported. In the present work, Ta metal was sputter-deposited onto amorphous silicon carbide (a-SiC), with and without a base titanium (Ti) adhesion layer, and investigated as interconnect metallization. In the absence of a Ti adhesion layer, resistivity measurements revealed a factor of six difference between Ta resistivity depending on the presence of the Ti base layer, with direct deposition on a-SiC nucleating high resistivity β-Ta (ρ = 197 ± 31 µΩ·cm, mean ± standard deviation) and Ta deposited on Ti nucleating low resistivity α-Ta (ρ = 35 ± 6 µΩ·cm). X-ray diffraction confirmed the existence of the two crystal structures. Ta feature sizes of 2 µm were created using photolithography and reactive ion etching (RIE). Finally, planar microelectrode array test structures using α-Ta and Au trace metallization with low-impedance ruthenium oxide (RuO_x) electrodes were fabricated and investigated by cyclic voltammetry (CV) and current pulsing in saline. These devices underwent 500 CV cycles between −0.6 and +0.6 V without evidence of degradation. In response to charge-balanced, biphasic current pulses at 4 nC/phase, a 21 mV increase in access voltage was observed with α-Ta metallization compared to Au. These results warrant further investigation of Ta as thin-film metallization interconnects for neural interface devices. Full article

The Cândești necropolis is currently the largest excavated Bronze Age necropolis in Romania, with approximately 800 graves. Notably, one grave from an earlier phase of the Monteoru culture (c. 2200–1850 BC) contained a remarkable necklace composed of 22 perforated gastropod shells and a metal pendant. Our investigation adopted an integrated approach, including taxonomic identification, taphonomic, technological and functional analyses, experimental studies, and physico-chemical investigations (Fourier Transform Infrared Spectroscopy and Raman spectroscopy) of the pigment traces present on the shells’s surface. For the metal pendant, X-Ray Fluorescence analysis was conducted to ascertain its elemental composition. The combined analysis yielded unexpected insights: the shells, belonging to the genus Conus, originated from the Mediterranean region. The perforations were not the result of anthropic intervention; rather, they were the result of natural processes, indicating that the shells were collected from thanatocoenoses. The shells were assembled into the necklace using a thread colored with a red pigment. The perforations show signs of prolonged use, suggesting that the necklace was not only a funerary offering. In conclusion, our study indicated that these exotic shells were collected post-mortem already perforated through a rubbing process in the seashore sediments, transported to the site from a distance, and prior to the death of the owner, had been previously worn as personal adornment before being deposited as grave goods. Full article

Granitic soils in the Highlands support the cultivation of Arabica coffee in northern Thailand; however, their geochemical and radiological properties are inadequately defined. This study examined major oxides, trace elements, natural radionuclides, and extractable phosphorus in granitic-derived coffee soils from the Agricultural Innovation Research, Integration, Demonstration, and Training Center (AIRID) in Chiang Mai. Twenty soil samples were obtained from 10 locations at two depth intervals (0–30 cm and 30–60 cm). Major and trace elements were analyzed via X-ray fluorescence (XRF), natural radionuclides were analyzed through high-purity germanium (HPGe) gamma spectrometry, and extractable phosphorus was determined using the Bray II method. The soils demonstrate remarkably high ⁴⁰K activity concentrations (1.2–1.9 kBq kg⁻¹) and increased K₂O contents (4.9–7.8 wt%), about three to five times more than worldwide soil averages according to Reimann & de Caritat, indicating enrichment from potassium-rich granitic rocks. Major oxide compositions suggest extensive tropical weathering, characterized by elevated SiO₂ (>60 wt%) and Al₂O₃ (>14 wt%), alongside significant depletion of CaO and MgO (<1 wt%). In topsoil, Bray II–extractable phosphorus constitutes 10–25% of total phosphorus and has a robust positive connection with P₂O₅ (R² = 0.95, p < 0.001), signifying surface accumulation and restricted vertical mobility. Multivariate analysis indicates lithogenic grouping of trace elements with negligible vertical redistribution. These findings establish a geochemical and radiological baseline for highland coffee soils in northern Thailand, with implications for soil fertility assessment, soil–plant transfer research, and evaluations of natural radioactive exposure related to coffee production. Full article