본 연구에서는 고분자 점도 조절제를 첨가하여 졸-겔법 기반 알루미나 나노여과막을 단일 공정으로 제조하고, 코 팅층의 구조 및 성능을 제어하는 방법을 제시하였다. Hydroxypropyl cellulose (HPC, Mw ~80000) 고분자를 알루미나 졸에 첨가하여 점도를 10 mPa·s에서 최대 4200 mPa·s까지 조절하였으며, 이를 통해 알루미나 중공사 지지체 표면에 균일하고 결 함이 없는 선택층을 형성하였다. HPC 함량이 증가할수록 코팅층 두께가 증가하였으나, 기공 크기 증가에 따라 분리 성능이 저하되었다. 2:1 (졸:HPC 고분자 용액) 혼합비에서 제조된 나노여과막은 두께 3.20 μm의 얇은 선택층을 형성하여 높은 수투 과도(12.9 LMH/bar)와 우수한 제거 성능(PPG 1050 Da 제거율 60%, PEG 1500 Da 제거율 90%, MgCl2 제거율 80%)을 나타 냈다. 반면, 1:2 혼합비에서는 선택층 두께가 10.2 μm로 증가하였으나, 기공 크기가 증가하여 3400 Da MWCO와 64% 염 제 거율을 보였다. HPC 고분자를 활용한 점도 제어는 졸-겔 코팅층의 두께, 기공 구조 및 분리 성능을 효과적으로 조절할 수 있 음을 입증하였다.

The development of high specific surface area and mesoporous activated carbons is required to improve the electrochemical performance of EDLC. In this study, kenaf-derived activated carbons (PK-AC) were prepared for high-power-density EDLC via phosphoric acid stabilization and steam activation. The pyrolysis behavior of kenaf with respect to the phosphoric acid stabilization conditions were examined via TGA and DTG. The textural properties of PK-AC were studied with N2/ 77 K adsorption–desorption isotherms. In addition, the crystalline structure of PK-AC was observed via X-ray diffraction. The specific surface area and mesopore volume ratio of PK-AC were determined to be 1570–2400 m2/ g and 7.7–44.5%, respectively. In addition, PK-AC was observed to have a high specific surface area and mesopore volume ratio than commercial coconut-derived activated carbon (YP-50F). The specific capacitance of PK-AC was increased from 77.0–99.5 F/g (at 0.1 A/g) to 49.3–88.9 F/g (at 10.0 A/g) with activation time increased. In particular, K-P-15-H-9–10 observed an approximately 35% improvement in specific capacitance at a higher current density of 10.0 A/g compared to YP-50F. As a result, the phosphoric acid stabilization method was confirmed to be an efficient process for the preparation of high specific surface area and mesoporous biomass-derived activated carbons, and the kenaf-derived activated carbons prepared by this process have great potential for application as electrode active materials in high-power EDLC.

This study developed a coupled fluid-thermal analysis method for a liquid hydrogen control valve system. Using ANSYS CFX, a transient CFD analysis was performed for the control valve system, including MLI, and the thermal analysis was linked to evaluate the insulation performance of MLI. The analysis examined the pressure distribution, turbulent viscosity, and heat flux at the inlet and outlet, revealing that the highest heat flux occurred in MLI 2. This research is expected to contribute to improving the thermal shielding performance and efficient insulation design of liquid hydrogen storage systems.

This study examined the quality characteristics of rice layer cakes prepared using various levels of allulose (ALL). ALL was used to substitute 0% (control group), 25% (ALL-25 group), 50% (ALL-50 group), 75% (ALL-75 group) and 100% (ALL- 100 group) of white sugar (WS) in the manufacture of rice layer cake. The substitution of WS with ALL decreased the pH of the cake batter but increased its specific gravity (p<0.001). The ALL-100 group exhibited higher moisture content than the control (p<0.05), and baking loss increased with increasing ALL levels (p<0.01). The volume index of the cake decreased significantly as the proportion of ALL increased (p<0.001). Low lightness, high redness, and high yellowness were observed in the experimental groups at higher proportions of ALL (p<0.001). The ALL-100 group exhibited significantly higher hardness, adhesiveness, cohesiveness, springiness, gumminess, and chewiness than the other groups (p<0.05). Sensory evaluation revealed that cakes with higher ALL levels had stronger perceived intensity with respect to “color,” “sweet aroma,” and “salty taste.” The acceptance test indicated that the ALL-25 group was comparable to or more acceptable than the control in all attributes except for color.

Marine biomass (MB) offers an environmentally friendly and readily available carbon source from the ocean. However, the high concentration of alkali and alkaline earth metals (AAEMs) in MB typically reduces the carbon yield and inhibits micropore formation during heat treatment due to catalytic gasification. In this study, we successfully synthesized activated carbon (AC) with a high specific surface area (> 1,500 m2/ g) and significant mesopore content (60%, mean pore size: 3.4 nm) from MB by employing preheating, controlled acid purification, and CO₂ activation. The formation of mesopores in the MB-derived AC was driven by catalytic gasification induced by intrinsic and residual AAEMs during preheating and physical activation processes. We evaluated the potential of the MB-derived AC as an electrode material for electric doublelayer capacitors (EDLCs). The material demonstrated high specific capacitance values of 25.9 F/g and 29.4 F/g at 2.7 V and 3.3 V, respectively, during charge–discharge cycles. These high capacitance values at elevated voltages were attributed to the increased number of solvated ions (e.g., 1.93 mmol/g at 3.3 V) present in the mesopores. Fluorine-19 nuclear magnetic resonance (19F solid-state NMR) analysis revealed a substantial increase in solvated ion concentration within the mesopores of the MB-derived AC electrode at 3.3 V, demonstrating enhanced ion mobility and diffusion. These findings highlight the potential of MB-derived AC as a promising electrode material for high-voltage energy storage applications.

Efforts to mass-produce high-quality graphene sheets are crucial for advancing its practical and industrial applications across various fields. In this study, we present an innovative electrochemical exfoliation method designed to enhance graphene quality and increase yield. Our approach combines two key techniques: expanding the tightly packed graphite interlayer used as the electrode medium and precisely controlling voltage polarity. The dual-exfoliation technique optimizes the use of anions and cations of varying sizes in the electrolyte to facilitate meticulous intercalation, allowing ions to penetrate deeply and evenly into the graphite interlayer. The newly designed dual-exfoliation technique using biased switching polarity minimizes the generation of oxygen-containing radicals, while the incorporation of expanded graphite accelerates exfoliation speed and reduces oxidation, maintaining high graphene purity. With these improvements, we produced 1–3 layer graphene sheets with minimal defects ( ID/IG ≈ 0.13) and high purity (C/O ratio ≈ 20.51), achieving a yield 3.1 times larger than previously reported methods. The graphene sheets also demonstrated excellent electrochemical properties in a three-electrode system, with an electrical conductivity of 92.6 S cm− 1, a specific capacitance of 207.4 F g− 1, and a retention of 94.8% after 5,000 charge/discharge cycles, highlighting their superior stability and performance.

Area-selective atomic layer deposition (AS-ALD) is a bottom-up process that selectively deposits thin films onto specific areas of a wafer surface. The surface reactions of AS-ALD are controlled by blocking the adsorption of precursors using inhibitors such as self-assembled monolayers (SAMs) or small molecule inhibitors. To increase selectivity during the AS-ALD process, the design of both the inhibitor and the precursor is crucial. Both inhibitors and precursors vary in reactivity and size, and surface reactions are blocked through interactions between precursor molecules and surface functional groups. However, challenges in the conventional SAM-based AS-ALD method include thermal instability and potential damage to substrates during the removal of residual SAMs after the process. To address these issues, recent studies have proposed alternative inhibitors and process design strategies.

본 연구의 목적은 복층 배수성·저소음 아스팔트 포장의 공용수명 예측과 경제성 분석에 있다. 성능평가를 위한 현장시 험은 투수시험 및 소음 측정을 실시하였으며, 실내시험은 반사균열, 동탄성계수, 소성변형(FN) 시험을 진행하였다. 성능 평가 결과를 기반으로 포장설계 수명 예측 및 비용 편익 분석을 수행하였으며, 이를 일반 밀입도 포장의 비용 편익과 비 교·분석하여 복층 배수성·저소음 아스팔트 포장의 경제성을 확인하고자 하였다. 성능평가 결과 복층 배수성·저소음 포장 이 일반 밀입도 포장과 비교 시 소음 저감 성능에서 매우 우수한 결과를 나타내었다. 비용 편익 분석 결과 복층 배수성· 저소음 아스팔트 포장은 높은 초기비용에도 불구하고 설계기간동안 낮은 유지보수 비용을 가지며 안전 및 소음 측면에 서 일반 밀입도 포장과 비교 시 매우 경제적인 것으로 나타났다. 총 비용과 총 편익 비용을 편익 비용 비율(BCR)로 계 산한 결과 복층 배수성·저소음 아스팔트 포장이 단위 비용 당 편익 측면에서 방음벽이 있는 다른 포장에 비해 가장 우수 한 결과를 보였다.

For the commercialization of bipolar plates, several properties must be considered together. Electrical conductivity, corrosion resistance, contact resistance, mechanical strength, and light weight are essential evaluation factors, with corrosion resistance and durability being significant for unitized regenerative fuel cells (URFCs), which must operate in electrolysis and fuel cell mode. However, improving both properties is challenging, since corrosion resistance is largely inversely proportional to conductivity. In this study, to improve both properties together, composites composed of Pb and Zn with excellent conductivity and corrosion resistance were prepared with graphite powder and formed as a coating layer on the surface of 304 stainless steel (SS304) and evaluated for electrical conductivity and corrosion resistance. Among the ZnPb/C composites prepared at various ratios, Zn8Pb2/C exhibited the lowest transmittance resistance of 1.566 Ω, and improved electrical conductivity and durability compared to bare SS304.

본 연구는 대류경계층(CBL) 구조 분석을 위해 Haar 이산 웨이블릿 변환(DWT)과 온위()-수증기 혼합비(r) 공 분산 관계를 활용하는 방법을 제시하였다. Haar DWT로 계산된 근사 계수는 연직  및 r 프로파일이 가지는 평균적인 경향성을 나타내며, 여러 규모에서의 상세 계수들 각 규모에서의 세부적인 변동성을 나타낸다. 두 변수의 상세 계수들 을 곱함으로써 각 규모에 대한 연직 -r 공분산 프로파일을 구하였다. 본 연구는 지표층 및 혼합층 상단 고도를 추정하 기 위해 가장 작은 규모, 즉 segment 길이가 약 1.5m 규모의 변동성이 제거된 공분산 프로파일을 활용하였다. CBL 내 -r 공분산 구조는 지표층에서 양의 값, 혼합층에서 0, 그리고 유입대에서 음의 값을 가진다. 이러한 구조를 바탕으 로 연구 기간 내 선정된 32개의 맑은 날 사례에 대해서 지표층 및 혼합층 상단 고도를 추정하였다. 추정된 고도는 연 직  및 r 프로파일과 비교함으로써 CBL 구조 정량화를 위한 Haar DWT와 -r 공분산 방법을 제안하였다.

This study aimed to improve the accuracy of road pavement design by comparing and analyzing various statistical and machine-learning techniques for predicting asphalt layer thickness, focusing on regional roads in Pakistan. The explanatory variables selected for this study included the annual average daily traffic (AADT), subbase thickness, and subgrade California bearing ratio (CBR) values from six cities in Pakistan. The statistical prediction models used were multiple linear regression (MLR), support vector regression (SVR), random forest, and XGBoost. The performance of each model was evaluated using the mean absolute percentage error (MAPE) and root-mean-square error (RMSE). The analysis results indicated that the AADT was the most influential variable affecting the asphalt layer thickness. Among the models, the MLR demonstrated the best predictive performance. While XGBoost had a relatively strong performance among the machine-learning techniques, the traditional statistical model, MLR, still outperformed it in certain regions. This study emphasized the need for customized pavement designs that reflect the traffic and environmental conditions specific to regional roads in Pakistan. This finding suggests that future research should incorporate additional variables and data for a more in-depth analysis.

The feeder pipes of the primary cooling system in a pressurized heavy water reactor (PHWR) are composed of carbon steel SA 106 GR.B. On the surface of this structural material, corrosion oxide layers including radionuclides are formed due to the presence of active species from water decomposition products caused by radiation, as well as the high temperature and high-pressure environment. These oxide layers decrease the heat transfer efficiency of the primary cooling system and pose a risk of radiation exposure to workers and the environment during maintenance and decommissioning, making effective decontamination essential. In this study, we simulated the formation of the corrosion oxide layer on the surface of carbon steel SA 106 GR.B, characterized the formed corrosion oxide layer, and investigated the dissolution characteristics of the corrosion oxide layer using oxalic acid (OA), a commercial chemical decontamination agent. The corrosion oxide layer formed has a thickness of approximately 4 μm and consists of hematite ( Fe2O3) and magnetite ( Fe3O4). The carbon steel coupons with formed oxide layers were dissolved in 10 mM and 20 mM OA solutions, resulting in iron ion concentrations of 220 ppm and 276 ppm in the OA respectively. In 10 mM and 20 mM OA, the corrosion depths of the coupons were 8.93 μm and 10.22 μm, with corrosion rates of 0.39 mg/cm2·h and 0.45 mg/cm2·h, respectively. Thus, this demonstrates that higher OA concentrations lead to increased dissolution and corrosion of steel.