In this study, porous silicon was prepared by coating SiO2 on the Mg2Si surface under controlled solvent conditions, followed by magnesiothermic reduction and etching as a high-capacity anode material for lithium-ion batteries. Porous silicon prepared using mixed solvents(ethanol/distilled water) formed a uniform porous structure with large pores. Porous silicon synthesized using distilled water exhibited a core-shell structure composed of the inner core with large pores and the shell layer with small pores. To improve the electrochemical performance, porous silicon composites were synthesized by the electrostatic assembly with MXene nanosheets and polydopamine-derived carbon coating. The W-Mg(0.1)-Si(2.6) with core-shell structure prepared using distilled water showed initial discharge capacity of 3614.6 mAh/g and high capacity of 1053.9 mAh/g at 4 C. The E-Mg(0.1)-Si(2.6)@MN(1:5) and E-Mg(0.1)-Si(2.6)@PDA(1:3) anode composites prepared by MXene nanosheets and polydopamine-derived carbon coating exhibited initial discharge capacities of 4531.6 and 3915.8 mAh/g and showed capacities of 1276.5 and 1193.1 mAh/g at 4 C.
This study investigated the effects of pretreatment conditions on the properties of kenaf/polypropylene (PP) biocomposites. Kenaf fibers were treated under alkaline conditions with moderate severity (NaOH 2-6 wt.%, Hfactor approximate to 800) and acidic conditions. The chemical composition changes were quantitatively analyzed using NREL standard methods, ensuring the reliability of the data, while the thermal and mechanical properties of the biocomposites were evaluated by thermogravimetric analysis (TGA) and tensile testing, respectively. The results showed that alkali pretreatment effectively reduced lignin and hemicellulose contents, leading to improved interfacial bonding between the fibers and the PP matrix. The tensile strength increased significantly with fiber loading up to 30 wt.%, while a decrease in the enhancement rate was observed at 40 wt.%, which could be explained by the theoretical rule of mixtures and fiber agglomeration. Thermal analysis revealed that pretreatment influenced the thermal degradation behavior of kenaf components, whereas the thermal stability of the PP matrix was largely maintained.
It is impractical to experimentally characterize hydrodynamics of molten-metal bubble columns (MMBCs) operated at high temperatures due to intrinsic opacity. This study investigated hydrodynamics of MMBCs with tertiary NiBiSe alloys and CH4 gas using a computational fluid dynamics (CFD) model based on level-set volume-of-fluid (LS-VOF), changing surface tension (sigma) and contact angle (theta). sigma of NiBiSe alloys containing 0, 1, and 5 mol% Selenium (Se) was 0.389, 0.317, and 0.31 N/m, respectively, while q was set to 120 degrees and 150 degrees. The six simulation cases were conducted in a rectangular MMBC with a centrally located bottom nozzle (diameter: 3.18 mm) at a superficial gas velocity of 0.39 mm/s under the bubbling flow regime. The time-averaged gas holdup ((alpha(G) )) overbar ranged 0.29-0.33%, the time- and volume-averaged bubble size ((d(32))) over bar was 6.54-8.05 mm, and the interfacial area ((a(s))) over bar was 1.70-2.09 m(2)/m(3). The ratio (gamma) of density to sigma was strongly related to d(32), and the minimum d(32) was observed in a Ni27Bi72Se1 MMBC exhibiting the highest gamma. Since the volume of initial bubbles formed at the column bottom increased with increasing theta, larger theta resulted in larger d(32). This study offers theoretical hydrodynamic foundation for hydrogen production in MMBCs via methane pyrolysis.
In this study, the CO2 capture characteristics of water-lean absorbents composed of 2-(ethylamino)ethanol (EAE), diethylene glycol monobutyl ether (DEGMBE), and water were investigated using a laboratory-scale packed absorption column at 40 degrees C. The effects of EAE (2-5 M) and DEGMBE (0-40 wt%) concentration on solvent viscosity, CO2 loading, absorption rate, and overall mass transfer coefficient were systematically examined. The viscosity of the solvent increased after CO2 absorption and with increasing DEGMBE content; however, the viscosity remained within the operable range for packed column operation. The rich CO2 loading increased with increasing EAE concentration due to the higher availability of reactive amine groups, whereas it decreased with increasing DEGMBE content as a result of reduced solvent polarity. The cyclic CO2 loading increased with EAE concentration, while the decrease with increasing DEGMBE content was relatively moderate. The CO2 absorption rate and overall mass transfer coefficient decreased with increasing lean CO2 loading because of the reduction in free amine concentration and the increase in liquid-phase and potential for reducing regeneration energy in CO2 capture processes.
We investigated effects of the precious metal and CeO2 loading on the performance of Pd-Rh-CeO2 based monolithic three-way catalysts. To explore the impact of aging, hydrothermal aging was also conducted at 1050 degrees C for 30 h. Under stoichiometric condition (lambda = 1.00), the performance with simulated automotive exhaust at 100-500 degrees C revealed that increase in CeO2 loading enhanced the NO and C3H8 removal. In contrast, under rich and lean conditions (lambda = 0.99 and 1.01, respectively), the overall performance was more strongly governed by precious metal loading than by CeO2 loading. In particular, excessive CeO2 loading tended to suppress C3H8 oxidation under conditions where NO2 formation or steam reforming was not favored, although the effect depended on PGM loading and A/F ratio. Simultaneously, N2O was more formed under NO reduction with lower CeO2 loading, but NH3 was more formed at higher CeO2 loading. Finally, after hydrothermal aging treatment, the deactivation of catalysts significantly occurred with increasing CeO2 loading, and the aging performance appeared similar regardless of the CeO2 content.
As interest in disposable, non-enzymatic sensors that require no pretreatment for easy use in both clinical settings and home environments, the development of cost-effective and high-performance electrode materials has become increasingly important. In this study, a high-performance non-enzymatic electrochemical sensor for glucose detection was fabricated using low-cost pencil graphite electrodes (PGEs) modified with polyaniline (PANI) and platinum nanoparticles (Pt NPs). The electrochemical properties were characterized using chronoamperometry (CA), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The Pt NPs/PANI/PGE electrode exhibited a wide linear range, enhanced sensitivity, rapid response, and excellent selectivity. This superior sensing performance was attributed to the large specific surface area of PANI, the uniform dispersion of Pt NPs, and the accelerated catalytic oxidation of glucose resulting from the formation of Pt-OH species on the Pt surface under alkaline conditions. These results demonstrate the potential of PGE-based electrodes incorporating various nanomaterials for the development of high-performance, cost-effective electrochemical sensors.
Transfer functions describing the dynamics of heat or mass diffusion from the surface of a semi-infinite medium may contain terms such as exp(- root s) and root s, which cannot be directly approximated using Pade approximation. Forexp(-root s), an approach has been proposed in which it is first expressed as a series involving the function 1/ cosh( root s), to which Pade approximation can be applied. Then, Pade approximation is applied to this series to obtain a rational transfer function in s. In this study, a method to accelerate the convergence of the series representation based on 1/ cosh( root s) is proposed and extended to the approximation of various transfer function elements that are not amenable to Pade approximation. Approximating these terms by rational transfer functions enables dynamic models originally formulated as partial differential equations to be represented in ordinary differential equation-based state-space form, facilitating simulation, analysis, and control system design. Step-response simulations demonstrate that satisfactory accuracy can be achieved with approximation orders of four or less while preserving steady-state characteristics and time-domain response accuracy.
Accurately predicting the density of deep eutectic solvents (DESs) is crucial for optimizing green separation processes. This study investigated the impact of feature representations (ChemBERTa, hybrid, and critical property models) and data partitioning (binary, ternary, and comprehensive datasets) on machine learning predictions. Evaluating RF, XGBoost, CatBoost, and ANN models revealed that tree-based ensembles were highly robust, consistently achieving R > 0.93 on limited datasets. Conversely, ANNs required explicit physical descriptors or massive datasets (>12,000 points) to prevent overfitting. Cross-domain validations demonstrated that extrapolating from simple to complex systems failed due to restricted thermodynamic diversity, whereas specializing from a comprehensive dataset ensured excellent transferability. These findings established that combining large, diverse datasets with ensemble algorithms or physics-informed features were essential for the reliable computational design of multicomponent DES properties.
This study presents a dynamic simulation of a hydrogen liquefaction process using a helium Brayton cycle under partial load conditions. Hydrogen feed flow was reduced to 90%, 80%, and 70% of the design value and temperature, pressure, and energy consumption across heat exchangers and rotating equipment were evaluated. Results showed that insufficient reduction in helium flow caused subcooling, lowering the liquid hydrogen temperature from 20.5K to 19.5K. Furthermore, due to the lower efficiency of the expander compared to the compressor, the decrease in recoverable energy exceeded the reduction in compression work, resulting in a 44.1% increased specific energy consumption. These findings emphasize the need for precise control of helium flow and operating conditions during partial load operation. Additionally, improving the performance of rotating equipment such as compressors and expanders is essential for enhancing the energy efficiency of hydrogen liquefaction systems.
Fire extinguisher placement in industrial facilities is a critical factor for effective initial fire response; however, conventional placement practices largely rely on expert experience and subjective judgment, resulting in insufficient quantitative criteria for location, quantity, and coverage. To address this limitation, this study proposes an MILP-based optimization model that simultaneously minimizes response time and the number of installed fire extinguishers. The proposed model incorporates obstacle-avoiding travel paths between workers, extinguishers, and fire locations, as well as practical operational constraints such as extinguisher coverage area, worker walking speed, and the maximum number of fires assignable to each extinguisher. The model was applied to the layout of a manufacturing facility using grid-based spatial discretization and the results demonstrate that full coverage can be achieved with approximately 30% fewer extinguishers compared to expert-based layouts, while reducing the maximum response time to within 14 seconds.
The demand for acetoacetate-based compounds has risen significantly in recent years due to their unique physicochemical properties and wide-ranging industrial applications. The critical-point, dew-point, and bubble-point equilibria data for the 3-pentyl acetoacetate + carbon dioxide (CO2) binary system in the temperature range of 313.2 K to 393.2 K and pressure limited to 20.06 MPa were measured. The mole fraction responses were acquired in the range of (0.0433 to 0.7950). The pressure-temperature diagrams indicated that the critical locus of the mixture formed a continuous boundary connecting the critical points of CO2 and pure 3-pentyl acetoacetate. The binary system 3-pentyl acetoacetate + CO2 did not display 3-phases according to the vapor-liquid equilibria research at the test temperature. At a fixed temperature, the solubility of the system was found to increase with increasing mole fraction of 3-pentyl acetoacetate. The observed phase behavior corresponded to a Type-I system according to the classification of Van Konynenburg and Scott. Additionally, the experimentally measured bubble-point pressures were correlated using the PR EoS (Peng-Robinson equation of state) combined with vdW(van der Waals) one-fluid mixing rules. The binary interaction parameters (k(i)j=0.005 and eta(i)j=-0.025) were optimized and determined for the 3-pentyl acetoacetate+CO2 system. The model predictions showed good agreement with the experimental data, yielding RMSD (root mean square deviation) values of 8.14%, 5.05%, 3.37%, 3.36%, and 2.90% across the investigated temperature range.
study was conducted to evaluate the feasibility of fatty acid (FA)-impregnated wood as a material of marine buoys for the aquaculture of seaweed. Hydrogenated castor oil (HCO) or castor oil (CAO) as an FA was treated into Japanese cedar (JAC), radiata pine (RDP) and Japanese cypress (CYP) specimens using an immersion, vacuum (Vac) and vacuum-then pressure (VAC-Pres) treatment. FA-impregnated specimens were submerged in saline water for 2 or 4 weeks, and measured subsequently its leaching resistance, TVS and bending strength. RDP (97.62%) treated with HCO (114.30%) using a Vac (113.49%) or Vac-Pres (145.82%) treatment showed the highest FA uptake and greatest resistance against saline water-leaching. Although most FA-impregnated specimens underwent shrinkage, total volumetric swelling (TVS) after saline-water submersion was lower than untreated control specimens (JAC: 3.97%; RDP: 2.97%; CYP: 2.24%), particularly TVS of Vac-treated specimens impregnated with HCO (0.34%) was lower compared to that with CAO (1.63%). Bending strength of specimens impregnated HCO using a Vac (JAC: 62 MPa; RDP: 67 MPa; CYP: 95 MPa) or VAC-Pres (JAC: 66 MPa; RDP: 73 MPa; CYP: 111 MPa) method increased significantly compared to that of control specimens (JAC: 51 MPa; RDP: 53 MPa; CYP: 76 MPa). JAC-marine buoy treated with HCO using a Vac method met the "Performance Standards of Environmental-friendly Buoys", which was designated by the Ministry of Oceans and Fisheries of the Republic of Korea, in all categories except for impact resistance. JAC marine buoy fabricated with the transverse direction, which is a perpendicular direction of wood grain, and then treated with HCO using a Vac method passed the impact-resistance test. Considering the results of this study and production factors such as domestic availability of wood raw materials, manufacturing cost and safety, it is thought that transverse-processed JAC treated with HCO using a Vac method for 15 min can be classified as the optimal combination of wood species, fatty acid, and treatment method for manufacturing wooden marine buoys. It is believed that buoys produced with the conditions can be applied for the aquaculture of seaweed.
Recently, increasing manganese (Mn) concentrations in groundwater have raised global concerns due to their potential effects on human health. In particular, Mn concentrations exceeding regulatory limits can cause neurological disorders and developmental impairments in children. Effective removal of aqueous Mn requires its oxidation to form insoluble Mn oxides. However, abiotic Mn2+(aq) oxidation proceeds very slowly under environmental dark conditions, which limits its practical applicability for water treatment. In this study, we employed goethite as a photocatalyst to demonstrate rapid Mn2+(aq) oxidation under abiotic conditions and systematically investigated the effect of temperature on the photocatalytic reaction. UV-Vis analysis revealed pronounced Mn oxidation under illuminated conditions, whereas negligible oxidation occurred in dark. In addition, Mn oxidation proceeded more rapidly in artificial groundwater than in artificial seawater, and the Mn2+(aq) oxidation rate increased with increasing temperature. XPS analysis further showed that higher temperatures led to an increase in the average oxidation state of Mn oxides formed on the goethite surface. We also calculated reaction rate constants at different temperatures and derived an activation energy of 48.71 kJ/mol and a pre-exponential factor of 0.76 M/s for the Mn2+(aq) oxidation driven by the goethite photocatalytic reaction. Overall, our results demonstrate that photocatalytic Mn2+(aq) oxidation provides an effective and sustainable approach for remediation of Mn2+(aq) contaminations under environmental aqueous conditions.
This study investigates a plasma-based process for the selective introduction of surface sulfur vacancies (S-vacancies) in molybdenum disulfide (MoS2) thin films grown by chemical vapor deposition (CVD) using argon (Ar) plasma. By varying the plasma exposure time from 2 to 16 s and employing Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES), a defect-first window was identified in the 2-8 s range, where sulfur atoms are preferentially removed without structural damage. Raman and AFM analyses confirmed defect formation, while XPS revealed a decrease in the S/Mo atomic ratio, quantitatively verifying selective sulfur removal. AES further confirmed the same trend with enhanced surface sensitivity. These conditions are consistent with literature reports on S-vacancy-induced improvements in electrochemical activity, including reduced charge transfer resistance, increased double-layer capacitance (C_dl), and enlarged electrochemically active surface area (ECSA). This approach provides an effective low-damage pretreatment strategy for MoS2 surface functionalization and enhanced catalytic reactivity.
carbon nitride (g-C3N4) photocatalyst has a relatively narrow band gap of 2.80 eV, which makes it active in the visible light range. Furthermore, the strong covalent bonds between carbon and nitrogen atoms provide excellent thermochemical stability. However, g-C3N4 photocatalyst still has a high band gap, which hinders its use as a visible light photocatalyst. To overcome this limitation, in this study, melamine was used as a starting material and the g-C3N4 photocatalyst was synthesized by a high-temperature reaction at 520 degrees C. To this, alkali metal hydroxides (LiOH, NaOH, KOH) were added, respectively, followed by heat treatment at 500 degrees C to synthesize alkali metal ion-doped M-g-C3N4 photocatalysts. The physical and chemical properties of the photocatalysts were then evaluated using various analytical equipments, including FT-IR, XPS, XRD, and UV-Vis spectrometer. XRD analysis confirmed a strong peak at 27.5 degrees, which indicated that the g-C3N4 photocatalyst was successfully synthesized. In addition, the alkali metal-doped M-g-C3N4 photocatalysts had narrower band gaps than the alkali metal-free g-C3N4 photocatalyst (2.80 eV), and among them, the band gap energy was found to be the lowest at 2.56 eV when K metal was doped. As the band gap energy decreases, electrons and holes can be easily generated by photoexcitation even with low-energy light, so it is judged that the alkali metal-doped M-g-C3N4 photocatalysts developed through this study can be used as effective visible-light photocatalysts.
capsule opacification (PCO) is a common complication after cataract surgery, and is caused by the attachment and proliferation of lens epithelial cell (LEC) that remains after intraocular lens (IOL) surgery. In this study, we examined the possibility of inhibiting PCO on the IOL surface by applying Au nanoparticle (AuNP) that can generate heat under near-infrared (NIR) irradiation on the IOL surface to kill the LEC that adheres and proliferates on the IOL surface by photothermal effect. AuNP was prepared by reducing the precursor HAuCl4 with sodium borohydride, and the prepared AuNP was applied to the surface of hydrophobic acrylic IOL. The photothermal properties were evaluated under NIR laser irradiation at a wavelength of 808 nm. Among the various compositions, the IOL coated with the AuNP synthesized under conditions of 50 mM HAuCl4 concentration and 9.0 mM dopamine concentration showed the best photothermal effect, with a temperature increase of 36 oC. In addition, IOL to which AuNP was applied showed cytotoxicity of 2% and was excellent in biocompatibility. The above results show that the AuNP synthesized in this study can kill LEC by the photothermal effect when applied on the IOL, thereby exhibiting the possibility of suppressing PCO generation on the IOL surface.
In hypersonic propulsion systems, regenerative cooling using hydrocarbon fuels is employed to manage the extreme thermal loads generated during flight. However, liquid hydrocarbon fuels undergo thermal cracking that leads to coke formation, resulting in channel blockage and performance degradation. In this study, the thermal cracking behavior of exo-THDCPD fuel was compared using stainless steel (SUS316), Inconel 600, and titanium (Grade 9) reactors, which are commonly used materials for thermal decomposition experiments. In addition, the effects of additives, dispersants, antioxidants, and metal deactivators, were quantitatively evaluated to investigate the endothermic characteristics and coke reduction performance depending on reactor material. The results showed that, compared with the stainless steel reactor, the Inconel reactor exhibited approximately a 10% increase in heat sink and an 85% reduction in coke formation, while the titanium reactor showed up to a 7% increase in heat sink and a 72% reduction in coke. When additives were applied, the coke reduction rate and heat sink increased by up to 97% and 14%, respectively, compared with the additive-free condition. These findings demonstrate that the physical properties of reactor materials significantly influence the thermal cracking behavior and coke formation of hydrocarbon fuels, emphasizing the need to consider reactor material selection in conjunction with additive optimization strategies.
This study aimed to examine the concept organization, component identification, and future recalculation direction of Atmospheric Environmental Capacity, one of the key keywords of the Comprehensive Air Quality Plan, in accordance with the current situation in Korea. In order to increase the achievement rate of South Korea's PM-2.5 environmental standards, it is believed that first of all, we need to thoroughly reset our country's atmospheric environmental capacity and atmospheric environmental carrying capacity, and develop overseas emission management methods, programs, and policies that are equivalent to the intensity of emission management methods for domestic emission sources including our country's workplaces. If an unavoidable situation arises where policies equivalent to the intensity for domestic emission sources cannot be implemented for overseas emission sources, it will be necessary to explain the reason to the South Korean people and seek their understanding, and in the future, experts from the public/private/research fields will need to continuously seek alternatives to increase the achievement rate of South Korea's PM-2.5 environmental standards.
- Nitrogen-doped porous carbons (CNx) were prepared from glucose-derived hydrochar via hydrothermal treatment followed by chemical activation with melamine, and then used as supports for Pd catalysts (Pd/CNx, where x denotes the N content in wt%) for the direct synthesis of H2O2 from H2 and O2 (DSHP). Optimal N doping played an important role in increasing the surface area and the density of pyridinic/pyrrolic sites in CNx, thereby improving Pd dispersion and reducing the mean Pd nanoparticle size. Among the Pd/CNx catalysts tested, Pd/CN0.8 exhibited the best performance, achieving 91% H2O2 selectivity and a productivity of 7056 mmol H2O2/g-Pd & centerdot;h at 39% H2 conversion. In contrast, Pd/CN1.4 and Pd/CN8.5 showed sharply decreased H2O2 selectivity and productivity due to accelerated H2O2 hydrogenation and decomposition over these catalysts. These results clearly demonstrate the importance of an optimal N-doping level for achieving high H2O2 selectivity and productivity in the DSHP reaction over Pd/CNx catalysts.
dissolution thermodynamics and preferential solvation of uracil (Ura) in aqueous mixtures of methanol and ethanol were systematically investigated over the temperature range 293.15-318.15 K. Experimental solubility data from the literature were analyzed using van't Hoff and Gibbs equations to evaluate the standard thermodynamic parameters of dissolution (Delta solH degrees, Delta solS degrees, Delta solG degrees). The results revealed that uracil dissolution was an endothermic and predominantly enthalpy-driven process across all solvent compositions, with solubility noticeably enhanced in intermediate alcohol-rich regions (x1 approximate to 0.35-0.45). The inverse Kirkwood-Buff integrals (IKBI) approach was employed to determine the preferential solvation parameter (delta x1,Ura), providing molecular-level insight into solute-solvent interactions. Positive delta x1,Ura values in water-rich mixtures indicated preferential hydration, while negative values in alcohol-rich systems reflected the progressive replacement of water by alcohol in the cybotactic region around Ura. Temperature elevation reduced the magnitude of delta x1,Ura, suggesting a weakening of solvent structural heterogeneity and hydrogen-bond networks. Overall, this combined thermodynamic and molecular interpretation enhanced understanding of nucleobase solvation in mixed solvents and provided a quantitative framework for optimizing pharmaceutical formulation design and solubility prediction.
