韓瑞大學

In this study, we successfully synthesized ZnS-MXene-TiO2 nanocomposite heterojunction to apply for photocatalytic degradation of the methylene blue dye (MB). This nanocomposite significantly improves light absorption, charge separation, and active sites area. The synthesized ternary nanocomposite is explained by X-ray diffraction (XRD), scanning electron microscopy (SEM), tunneling electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis), PL (photoluminescence spectroscopy), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photocurrent, and cyclic voltammogram (CV) test. The energy bandgap of the composite (ZnS-MXene), (MXene-TiO2), and (ZnS-MXene-TiO2) is found to be 3.20, 3.05, and 2.95 eV, respectively. The ternary composite of narrow bandgap exhibits enhanced photocatalytic activity through UV photon more excitation. Due to the high surface area, it can increase the adsorption of MB molecules onto the catalyst surface and will be cost-effective considering the synthesized materials. The photocatalytic analysis of the nanocomposite is utilized standard dyes of methylene blue (MB) degradation percentage (98.2%) and pollutant of tetracycline (TC) degradation efficiency (98.0%) under visible light. The analysis of the (ZnS-MXene-TiO2), which has good catalytic properties for the degradation of MB and TC.

This study prepared carbon nanotube-modified BiFeO₃ (CNT‑BiFeO₃) composite photocatalysts for visible‑light‑driven degradation of ammonia nitrogen. The introduction of CNTs promotes the separation of photogenerated carriers and constructs a type‑II heterojunction with an internal built‑in electric field, which effectively suppresses electron‑hole recombination and improves photocatalytic activity. The optimized CNT‑BiFeO₃ catalyst achieves an ammonia degradation efficiency of 87.43

Rotor-induced tonal noise is a major source of acoustic discomfort in Advanced Air Mobility (AAM) cabins, particularly under time-varying rotor speeds. Narrowband active noise control (ANC) is effective for mitigating such tonal components; however, its performance strongly depends on accurate and timely tracking of the blade passing frequency (BPF). This study proposes a narrowband ANC system incorporating an innovation-based adaptive Kalman filter (AKF) for real-time BPF estimation. The proposed system combines the AKF with a Momentum Filtered-x Least Mean Square (MFxLMS) controller, enabling robust frequency tracking under dynamic operating conditions through adaptive adjustment of process and measurement noise covariances. The performance of the proposed approach is experimentally evaluated using a two-bladed rotor under two representative operating scenarios: a trapezoidal rotor rotational speed profile with predictable transitions and a stochastic profile with stochastic speed fluctuations. The results show that Kalman filtering significantly improves ANC performance by suppressing reference signal jitter and preventing noise amplification in frequency bands adjacent to the target BPF. Under predictable operating conditions, a conventional Kalman filter with fixed noise covariance matrices performance is comparable to that of the AKF. In contrast, under stochastic and highly dynamic conditions, the AKF demonstrates superior robustness by reducing tracking delay and maintaining phase synchronization, leading to improved ANC stability. These findings indicate that, for rotor-based narrowband ANC, frequency mismatch caused by tracking lag is more detrimental to control stability than mismatch caused by measurement noise, highlighting the importance of estimator responsiveness in dynamic AAM environments.

Butyl levulinate (BL) is a renewable and environmentally friendly fuel additive with significant potential in sustainable biofuel applications. In this study, a series of solid acid catalysts was synthesized by impregnating silicotungstic acid (STA) onto bentonite supports activated either by acid treatment or thermal calcination. STA was incorporated using both conventional incipient wetness and ultrasound-assisted impregnation methods. The catalysts were comprehensively characterized to evaluate their structural, textural, and acidic properties, and their performance was assessed in the esterification of levulinic acid (LA) with n-butanol to produce BL. Comparative analysis revealed that acid-activated bentonite exhibited superior surface area and pore volume, while ultrasound-assisted impregnation enhanced STA dispersion and catalyst acidity. Under optimized conditions (LA:n-butanol 1:10, 20 wt% catalyst loading, 120 degrees C), the ultrasound-assisted catalyst (B2/STA/US) achieved complete LA conversion (100%) and high BL selectivity (98%). Moreover, the catalyst demonstrated excellent stability, retaining high performance over five consecutive cycles with negligible STA leaching. These findings highlight the synergistic role of acid-activated bentonite and ultrasonically dispersed STA in developing efficient, durable, and recyclable solid acid catalysts for green fuel additive production.

This study reports the synthesis of a magnetite/MXene (Fe₃O₄/MXene) nanocomposite via ball milling method for environmental remediation through the efficient degradation of methylene blue (MB) dye. Density functional theory (DFT) calculations are performed to gain insights on the structural stability and electronic properties of the composite. The nanocomposite was comprehensively characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive-X-ray spectroscopy (EDS/EDAX), and UV–Vis spectroscopy, confirming the formation of crystalline Fe₃O₄/MXene with well-defined morphology, surface functional groups, and suitable bandgap for the photocatalytic activity. Under optimized conditions, the nanocomposite has achieved an MB degradation efficiency of approximately 99.74