The hazard posed by volcanic ballistic projectiles (VBPs) is commonly assessed using trajectory models that estimate impact locations and energies. Recent models simulate the one-way coupling between the erupting gas–ash mixture and particles by inserting the numerically obtained flow field into the equation of particle motion. Model testing typically relies on reproducing observed travel distances in the field, but this approach is hindered by poorly constrained pre-eruptive conditions such as vent overpressure. To overcome this limitation, this study applies a trajectory model based on the steady-state supersonic jet flow field to reproduce experimental trajectory data obtained from high-speed shadowgraph imaging of spherical glass beads initially at rest and accelerated by supersonic jets from an open-ended shock tube. The model successfully reproduces the observed velocity profiles, demonstrating the viability of the one-way coupling approach for dilute particle populations accelerated by supersonic jets. The reproduced trajectories yield particle Reynolds numbers between 103 and 2 × 105. In this range, drag coefficients for both spherical and irregular-shaped particles are largely independent of particle Reynolds number and depend primarily on particle Mach number. Furthermore, an equation for the duration of steady-state supersonic flow conditions is derived, validated, and then used. The equation shows that, in many explosive eruptions, VBPs are predominantly accelerated during the period in which the supersonic jet can be approximated as steady-state. Particle acceleration is strongest near the vent and decreases rapidly with distance, implying that early jet collapse has little influence on maximum VBP velocities.
White photovoltaic modules are attractive for building-integrated photovoltaics (BIPV) because they can improve architectural compatibility, whereas the strong visible-light scattering required for whitening inevitably reduces photovoltaic power generation. In this study, the coupled optical, electrical, and thermal effects of whitening were experimentally investigated using rutile TiO2 particle scattering layers formed on glass substrates and placed over silicon heterojunction (SHJ) solar cells. TiO2 particles with an average diameter of 508 nm were dispersed in an acrylic matrix and coated onto glass substrates with nominal TiO2 volume fractions of 1–10 vol%. Increasing the TiO2 loading increased visible reflectance and CIELAB lightness L*, while reducing optical transmission, short-circuit current, and maximum power output. The improvement in lightness became relatively small above approximately 5 vol%, indicating diminishing visual benefits at higher particle loadings. When referenced to bare glass at the same incidence angle, the relative electrical loss showed only a modest incidence-angle dependence over the investigated angular range. Under continuous 1-sun illumination, whitening substantially reduced the thermal response of the cell. At 10 vol% TiO2, the maximum output power decreased by 54.5% relative to the bare-glass reference, whereas the steady-state cell backside temperature decreased by 8.3 °C and the local backside heat flux decreased by 50.0%. These results quantitatively demonstrate an electrical–thermal trade-off in white photovoltaic structures and highlight the need to optimize scattering-layer design to balance architectural appearance, photovoltaic power generation, and backside thermal transport in BIPV applications.
Effective treatment of organic dye-contaminated water is of great importance, and graphene derivatives are excellent examples for decontamination due to their exceptional properties, especially the large surface area and chemical stability. The present study focused on the utilization of orange peel extract-assisted reduced graphene oxide (rGO) as a promising adsorbent for the removal of methylene blue (MB) dye. To synthesize rGO from graphene oxide (GO), orange peel extract serves as a reducing agent, offering a cost-effective, renewable, and environmentally friendly alternative. The green-synthesized rGO was characterized using UV-vis, FTIR, EDX spectroscopy, TG analysis, XRD, and TEM. These comprehensive analyses confirmed the effective reduction of GO and the successful formation of few-layered, exfoliated rGO nanosheets. The adsorption performance of the synthesized rGO for the removal of MB was assessed. The adsorption kinetics of MB on rGO can be best described by the pseudo-second-order kinetics model and the Langmuir model, which indicates that a chemisorption process governs the adsorption through a monolayer adsorption on the homogeneous surface of rGO. The maximum adsorption capacity is 82 mg/g, and the removal efficiency is 80%, which testifies to the suitability of the synthesized rGO as a promising adsorbent material.
This study presents the design of imidazole/urethane-functionalized silsesquioxane nanoparticles (SQNPs) that enable rapid self-healing through dynamic Zn-imidazole coordination and hydrogen bonds. Methylimidazole/hydroxyl-functionalized SQNPs (MI/OH-SQNPs) were prepared using epoxy-functionalized SQNPs and reacted with structurally diverse isocyanates, phenyl isocyanate (PU), hexamethylene diisocyanate (HMU), and methylenediphenyl diisocyanate (MDU), to yield MI/PU-, MI/HMU-, and MI/MDU-SQNPs, respectively. Extensive characterization (using nuclear magnetic resonance, Fourier-transform infrared (FT-IR) spectroscopy, size-exclusion chromatography, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction analysis, transmission electron microscopy, and atomic-force microscopy) showed a uniform dispersion of approximately 10 nm, an amorphous structure, excellent solubility, and good thermal stability (>230 degrees C). The drop-cast films of the imidazole/urethane-SQNP-Zn hybrids exhibited flexural moduli of 1.52, 1.86, and 4.08 GPa for MI/PU-, MI/HMU-, and MI/MDU-SQNPs, respectively, reflecting the effects of urethane linker rigidity, crosslink density, and covalent/noncovalent interactions. MI/PU-SQNP-Zn formed dual noncovalent networks combining hydrogen bonding and metal-ligand coordination, providing moderate stiffness with increased toughness. In contrast, MI/MDU-SQNP-Zn, which contained rigid aromatic segments, exhibited the highest modulus and strength. Zn coordination was confirmed via FT-IR spectroscopy, and transparent films (up to 99.6% transmittance at 400 nm) were produced. The formation of mechanically robust hybrid networks was confirmed via dynamic mechanical analysis, highlighting its ability to maintain structural integrity while allowing dynamic bond exchange. Scanning electron microscopy-energy dispersive spectroscopy confirmed the successful incorporation and uniform distribution of Zn within all hybrid networks. These Zn-complexed systems exhibited promising self-healing performances: MI/PU-, MI/HMU-, and MI/MDU-SQNP-Zn hybrids achieved similar to 87%, similar to 78.5%, and similar to 35% recovery of their mechanical integrity, respectively, which was governed by the flexibility or rigidity of the urethane segments. Additionally, MI/PU-SQNP-Zn demonstrated rapid thermal self-healing, recovering approximately 68% of its strength within 60 min at 50 degrees C and visibly healed in 10 s at 80 degrees C. These findings indicate that Zn-coordinated imidazole-urethane SQNPs offer a versatile platform for creating mechanically robust self-healing hybrid materials with promising applications in coatings, glassy materials, and functional composites.
