Search Results (134)

Continuous global monitoring of volcanic activity from space requires balancing spatial and temporal resolution, a long-standing trade-off between polar-orbiting and geostationary satellites. Polar sensors such as MODIS, VIIRS, and SLSTR provide high spatial resolution (375 m–1 km) but with limited temporal coverage. In contrast, geostationary sensors like SEVIRI offer high temporal resolution (5–15 min) but with coarser spatial detail (~3 km), often missing lower-intensity thermal events. The recently launched Flexible Combined Imager (FCI) aboard the geostationary Meteosat Third Generation (MTG-I) satellite represents a major improvement, providing images every 10 min with a spatial resolution of 1–2 km, comparable to that of polar orbiters. Here, we adapted the established Remote Sensing Data Fusion (RSDF) algorithm to exploit the enhanced capabilities of FCI for detecting volcanic thermal anomalies and estimating Volcanic Radiative Power (VRP). The algorithm was applied to Mount Etna during three different eruptive phases that occurred in 2025. The VRP derived from FCI data was compared with that obtained from the geostationary SEVIRI and the polar-orbiting MODIS, SLSTR, and VIIRS sensors. The results show that FCI provides a more detailed and continuous characterization of volcanic thermal output than SEVIRI, while maintaining close agreement with polar sensors. These findings confirm the capability of FCI to deliver high-frequency, high-resolution thermal monitoring, representing a major step toward operational, near-real-time volcanic surveillance from space. Full article

Corrosion of carbon steel in acidic media remains a critical challenge during acidizing operations. This study evaluates carrot and rosemary extracts—individually and in combination—as green corrosion inhibitors for carbon steel in 1 M HCl. Inhibition performance was assessed using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), SEM/EDS, and adsorption isotherms. Weight-loss measurements showed inhibition efficiencies of 59.5% (carrot) and 85.7% (rosemary) at 800 ppm, while their 30/70 mixture achieved a markedly higher efficiency of 99.6%. PDP results confirmed this trend, with corrosion current density decreasing from 892 μA/cm² (blank) to 13.4 μA/cm² for the mixture, corresponding to 98.5% efficiency. In addition, EIS analysis revealed a substantial increase in charge-transfer resistance from 41.1 ohm·cm² (blank) to 174.9 ohm·cm² (carrot), 266.9 ohm·cm² (rosemary), and 1868.1 ohm·cm² for the 30/70 mixture, confirming superior barrier formation. Moreover, temperature-dependent tests showed only a 5% efficiency loss for the mixture and an average 6% decrease for the single extracts between 25–45 °C, indicating good thermal stability. Also, SEM images demonstrated severe surface damage in the blank sample, while carrot-, rosemary-, and mixture-treated surfaces showed progressively smoother morphologies. EDS analysis confirmed this trend, with Fe content increasing from 65.78% (blank) to 90.16% (carrot), 91.88% (rosemary), and 94.59% for the mixture. Furthermore, FTIR and GC–MS identified oxygenated functional groups and major phytochemicals responsible for adsorption. Adsorption data followed the Langmuir model, and Gibbs free energy values from −25 to −31 KJ/mol indicated spontaneous mixed physisorption–chemisorption. Overall, the 30/70 carrot–rosemary mixture consistently achieved the highest corrosion protection across all tests, confirming strong synergistic adsorption and demonstrating its potential as a high-performance, eco-friendly inhibitor for acidic environments. Full article

Unsaturated polyester resins (UPRs) were synthesized from camphoric acid and diluted with styrene, partially replaced (up to 30%) by trimethylolpropane triacrylate (TMPTA). Rheological tests showed increased but sustainable viscosity due to TMPTA’s higher polarity. These UPRs served as matrices for composites reinforced with non-woven bamboo and flax mats from recycled waste. Mechanical testing revealed that C_f-UPR/TMPTA30 exhibited the highest tensile strength (25.2 MPa) and modulus (0.96 GPa), compared to 18.7 MPa and 0.74 GPa for the styrene-based resin, respectively, attributed to greater cross-link density. Bamboo composites showed lower tensile properties (13.6 MPa) due to random fiber orientation and porosity, while flax-reinforced systems, especially C_f-UPR/TMPTA30–FLAX, reached 42.7 MPa tensile and 95.5 MPa flexural strength, indicating synergy between TMPTA-modified resin and flax fibers. Dynamic-mechanical analysis confirmed stable thermo-mechanical behavior, and water uptake tests showed reduced absorption (by ~10%), suggesting improved fiber/matrix adhesion. SEM images revealed brittle fracture and fiber pull-out in styrene systems, but fiber breakage and ductile textures in TMPTA-based ones, proving better stress transfer. Thermal analysis indicated slightly earlier degradation onset for TMPTA-modified resins but higher char yield in fiber composites. Overall, TMPTA substitution and flax reinforcement enhance the mechanical, interfacial, and thermal properties of bio-based UPRs, supporting sustainable high-performance composites. Full article

This paper explores the structural, mechanical, thermal, and electrochemical properties of copper matrix composites (CMCs) enhanced by Crassostrea madrasensis seashell powder, which were produced via powder metallurgy and resistance sintering. FESEM images showed a uniform distribution of bio-ceramic particles in the copper matrix composites (CMCs), leading to an improved microstructure and enhanced mechanical behavior. Mechanical tests showed that after incorporating 12 wt.% seashell powder, the average hardness increased to 56 HV, and compressive strength improved to 686 MPa. Density analysis showed a decrease in porosity, which was attributed to better particle diffusion during sintering. The corrosion resistance was evaluated using electrochemical techniques, including OCPT, Tafel polarization, EIS, LSV, and chronocoulometry, which were employed in 3.5 wt.% NaCl media with varying concentrations of the extract of Allium sativum (garlic) as a green inhibitor. Garlic-derived phytochemicals facilitated surface passivation, which was proven by shifts in potential, reduced corrosion rates, and minor charge transfer. The findings confirm that Crassostrea madrasensis bio-ceramic reinforcements and garlic extract-based corrosion inhibition provide a sustainable method for improving the performance and durability of copper matrix composites. Full article

Eleven novel asymmetric pyrimidine derivatives were synthesized. The pyrimidine core was functionalized with a coumarin chromophore and a pro-mesogenic fragment bearing either chiral or linear alkyl chains of variable length and substitution patterns. The thermal properties were investigated using polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering, revealing that only selected derivatives exhibited liquid crystalline phases with ordered columnar or smectic organizations. Linear and nonlinear optical properties were characterized by UV–Vis absorption, fluorescence spectroscopy, two-photon absorption, and second-harmonic generation. Optical responses were found to be highly sensitive to the substitution pattern: derivatives functionalized at the 4 and 3,4,5 positions exhibited enhanced 2PA cross-sections and pronounced SHG signals, whereas variations in alkyl chain length exerted only a minor influence. Notably, compounds forming highly ordered non-centrosymmetric mesophases produced robust SHG-active thin films. Importantly, strong SHG responses were obtained without the need for a chiral center, as the inherent asymmetry of the linear alkyl chain derivatives was sufficient to drive self-organization into non-centrosymmetric materials. These results demonstrate that asymmetric pyrimidine-based architectures combining π-conjugation and controlled supramolecular organization are promising candidates for nonlinear optical applications such as photonic devices, multiphoton imaging, and optical data storage. Full article

We present a compact hybrid imaging system operating in the 3–5 μm spectral band that combines refractive optics with a dispersion-engineered metasurface to overcome the longstanding trade-off between wide field of view (FOV), system size, and thermal stability. The system achieves an ultra-wide 178° FOV within a total track length of only 28.25 mm, employing just three refractive lenses and one metasurface. Through co-optimization of material selection and system architecture, it maintains the modulation transfer function (MTF) exceeding 0.54 at 33 lp/mm and the geometric (GEO) radius below 15 μm across an extended operational temperature range from –40 °C to 60 °C. The metasurface is designed using a propagation phase approach with cylindrical unit cells to ensure polarization-insensitive behavior, and its broadband dispersion-free phase profile is optimized via a particle swarm algorithm. The results indicate that phase-matching errors remain small at all wavelengths, with a mean value of 0.11068. This design provides an environmentally resilient solution for lightweight applications, including automotive infrared night vision and unmanned aerial vehicle remote sensing. Full article

The study investigates the interaction of humic acids (HAs) with road petroleum bitumen to enhance its performance and resistance to technological aging. It addresses a critical gap in understanding the modification mechanisms. The research is motivated by the need for sustainable and effective bitumen modifiers to improve the durability of asphalt pavements. The primary objective was to characterize the interaction between HA and bitumen using advanced analytical techniques, including complex thermal analysis (DTA/DTG), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrated that adding two wt.% HA to bitumen BND 70/100 increased its thermal stability, raising the onset temperature of thermo-oxidative processes from 214 to 237 °C and reducing the mass loss rate during heating from 2.5 to 1.9%·min⁻¹. FTIR analysis revealed chemical interactions between polar groups of humic acids (e.g., –COOH, –OH) and bitumen components, forming a denser structure. SEM images confirmed a more homogeneous microstructure with fewer microcracks in the modified bitumen. Practical improvements included a higher softening point (52.6 to 54 °C) and enhanced elastic recovery (17.5 to 28.7%). However, the study noted limitations such as reduced ductility (from 58 to 15 cm) and penetration (from 78 to 72 dmm), indicating increased stiffness. The findings highlight the potential of humic acids as eco-friendly modifiers to improve bitumen’s aging resistance and thermal performance, offering practical value for extending pavement lifespan. The effective use of HA will, in turn, allow the use of Ukrainian lignite, the balance reserves of which are estimated at 2.0–2.9 billion tons, in non-fuel technologies. Full article

Encapsulation of fish oil within oleogels can potentially prevent oxidation and enable its use in food with programmable release within the gastrointestinal tract. Here, we report on the formation of oleogels from two different fish oils—salmon oil (SO) and cod liver oil (CLO)—using different concentrations of either rice bran wax (RBW) or myristic acid (MA) as gelators. The gels were assessed with respect to their structural, thermal, viscosity, digestive, and oxidative properties. Polarized light microscopy (POM) revealed that RBW consistently produced dense, interconnected crystalline networks across both oils, while MA formed larger, spherulitic crystals that were more sensitive to the oil type. This was further supported by time-lapse imaging, showing faster crystal growth of MA in cod liver oil. Viscosity studies indicate that the molecular weight and concentration of gelator, as well as the type of fish oil (SO vs. CLO), significantly impact the shear stability of the oleogels. Thermal and viscosity analyses confirmed that RBW-based oleogels exhibited higher crystallization temperatures and stronger viscoelastic behaviour. Based on oxidative stability measurements—as measured by peroxide value (PV) analysis—encapsulation within oleogels does not lead to significant oxidation of the fish oils and also attenuates further oxidation upon storage. The fish oil oleogels were stable when exposed to either simulated gastric or intestinal fluids (SGF and SIF, respectively), but decomposed after sequential exposure first to SGF and then to SIF. These findings could broaden the range of food products which can be fortified with fish oils. Full article

A continuous-wave (CW) orthogonally polarized single-wavelength red laser (OPSRL) at 698 nm with a tunable power ratio within a wide range between the two polarized components was demonstrated using two Pr³⁺:LiLuF₄ (Pr:LLF) crystals for the first time. Through control of the waist location of the pump beam in the active media, the output power ratio of the two polarized components of the OPSRL could be adjusted. Under pumping by a 20 W, 444 nm InGaN laser diode (LD), a maximum total output power of 4.12 W was achieved with equal powers for both polarized components, corresponding to an optical conversion efficiency of 23.8% relative to the absorbed pump power. Moreover, by a type-II critical phase-matched (CPM) BBO crystal, a CW ultraviolet (UV) second-harmonic generation (SHG) at 349 nm was also obtained with a maximum output power of 723 mW. OPSRLs can penetrate deep tissues and demonstrate polarization-controlled interactions, and are used in bio-sensing and industrial cutting with minimal thermal distortion, etc. The dual-polarized capability of OPSRLs also supports multi-channel imaging and high-speed interferometry. Full article

In this work, we propose and analyze a thermally tunable metasurface based on indium antimonide (InSb), designed to operate in the terahertz (THz) frequency range. The metasurface exhibits dual functionalities: single-band perfect absorption and efficient polarization conversion, enabled by the temperature-dependent permittivity of InSb. At approximately 280 K, InSb transitions into a metallic state, enabling the metasurface to achieve near-unity absorptance (100%) at 0.408 THz under normal incidence, independent of polarization. Conversely, when InSb behaves as a dielectric at 200 K, the metasurface operates as an efficient polarization converter. By exploiting structural anisotropy, it achieves a polarization conversion ratio exceeding 85% over the frequency range from 0.56 to 0.93 THz, while maintaining stable performance for incident angles up to 45°. Parametric analyses show that the resonance frequency and absorption intensity can be effectively tuned by varying the InSb square size and the silica (SiO₂) layer thickness, achieving maximum absorptance at a SiO₂ thickness of 16 μm. The proposed tunable metasurface offers significant potential for applications in THz sensing, imaging, filtering, and wavefront engineering. Full article

Long-wave infrared (LWIR) broadband absorption is of great significance in science and technology. The electromagnetic field energy is absorbed by the metamaterials material, leading to the enhanced light absorption, from which the Metal–Dielectric–Metal (MDM) structure is designed. FDTD simulation calculation indicate that the bandwidth within which the absorber absorption ratio greater than 90% is 11.04 μm, and the average absorption rate (9.10~20.14 μm) is 93.6%, which can be accounted for by the impedance matching theory. Upon the matching of the impedance of the metamaterial absorber with the impedance of the incident light, the light reflection is reduced to a minimum, and increase the absorption ratio. Meanwhile, the good incidence angle unsensitivity due to the metasurface structural symmetry and the characteristics of the electromagnetic field distribution at different incidence angles. Due to the form regularity of the nanoring–nanowire metasurface structure, the light acts similar in different polarization directions, and the surface plasmon resonance plays a key role. Using FDTD electromagnetic field analysis to visualize the electric field and magnetic field strength distribution within the absorber, the electromagnetic field at the interface in the nanoring–nanowire metasurface structure, promote the surface plasmon resonance and interaction with damaged materials, and improve the light absorption efficiency. Moreover, the different microstructures and the electrical and optical properties of different top materials affect the light absorption. Meanwhile, adjusting the absorption layer thickness and periodic geometry parameters will also change the absorption spectrum. The absorber has high practical value in thermal electronic devices, infrared imaging, and thermal detection. Full article

Spectrally selective infrared absorbers play a pivotal role in enabling optoelectronic applications such as infrared detection, thermal imaging, and photothermal conversion. In this paper, a dual-band wide-spectrum infrared selective absorber based on a metal–dielectric multilayer structure is designed. Through optimized design, the absorptance of the absorber reaches the peak values of 0.87 and 1.0 in the target bands (3–5 μm and 8–14 μm), while maintaining a low absorptance of about 0.2 in the non-working bands of 5–8 μm, with excellent spectral selectivity. By analyzing the Poynting vector and loss distribution, the synergistic mechanism of the ultra-thin metal localized enhancement effect, impedance matching, and intrinsic absorption of the material is revealed. This structure exhibits good polarization-insensitive characteristics and angle robustness within a large incident angle range, showing strong adaptability to complex optical field environments. Moreover, the proposed planarized structure design is compatible with standard fabrication processes and has good scalability, which can be applied to other electromagnetic wave bands. This research provides new design ideas and technical solutions for advanced optoelectronic applications such as radiation cooling, infrared stealth, and thermal radiation regulation. Full article

In this study, the γ → α phase transition and decomposition of AlH₃ were probed using integrated hot-stage polarized microscopy, in situ XRD, DSC, and fluorescence analysis. Phase coexistence at 100 °C and complete transition at 140 °C were demonstrated by in situ XRD. Meanwhile, synchronized fluorescence decay (ImageJ-quantified) and XRD evolution analysis confirmed the temperature-dependent kinetics, with the isothermal γ → α durations decreasing from 225 min (100 °C) to 5 min (180 °C). The transition involved competing surface nucleation and bulk diffusion, which was accelerated by the reduced diffusion resistance at elevated temperatures. Above 160 °C, α → Al decomposition dominated via interfacial reactions and H₂ release, accompanied by gas-induced crystalline fracturing. DSC analysis revealed heating-rate-dependent core–shell thermal gradients, which caused hysteresis. At the same time, the experiment also shows that the surface oxidation of γ-AlH₃ may have hindered transitions through passivation layer formation. This work validates Gao et al.’s core–shell model, demonstrating that combined fluorescence and conventional techniques elucidate kinetic laws in metastable systems. Full article

Three-dimensional topological insulators possess surface-conducting states in the bulk energy gap, which are topologically protected and can be well described as helical 2 + 1 Dirac fermions. The electromagnetic response is given by axion electrodynamics in the bulk, leading to a Maxwell–Chern–Simons theory at the boundary, which is the source of the Hall conductivity. In this paper, we extend the formulation of axion electrodynamics such that it captures higher-derivative corrections to the Hall conductivity. Using the underlying 2 + 1 quantum field theory at the boundary, we employ thermal field theory techniques to compute the vacuum polarization tensor at finite chemical potential in the zero-temperature limit. Applying the derivative expansion method, we obtain higher-order derivative corrections to the Chern–Simons term in 2 + 1 dimensions. To first order the corrections, we find that the Hall conductivity receives contributions proportional to ${\omega }^2$ and ${\mathbf{k}}^2$ from the higher-derivative Chern–Simons term. Finally, we discuss the electrodynamic consequences of these terms on the topological Faraday and Kerr rotations of light, as well as on the image monopole effect. Full article

Following the success of Visible Infrared Imaging Radiometer Suite (VIIRS) instruments currently operating onboard the Suomi-NPP, NOAA-20, and NOAA-21 spacecraft, preparations are underway for the final two VIIRS instruments for the Joint Polar Satellite System 3 (JPSS-3) and 4 (JPSS-4) platforms. To that end, each instrument underwent a comprehensive sensor-level test campaign at the Raytheon Technologies, El Segundo facility, in both ambient and thermal-vacuum environments. Unique among the 22 VIIRS sensing bands is the day-night band (DNB)—a panchromatic imager that leverages multiple CCD detectors set at different gain levels to make continuous (day and night) radiometric observations of the Earth. The results from the JPSS-3 and JPSS-4 VIIRS DNB pre-launch testing are presented and compared against the design specifications in this paper. Characterization parameters include dark offset, gain, linearity, uniformity, SNR, and uncertainty. Performance relative to past builds is also included where appropriate. Full article