In this study, the heat transfer characteristics of a liquid hydrogen (LH2) tank with multilayer insulation (MLI) were numerically investigated. The temperature distribution inside the LH2 tank and within the MLI, as well as the temperature variation according to positional changes, heat transfer rate, and boil-off rate (BOR), were compared and analyzed. The results showed a distinct stepwise temperature drop in Case 4 with 20 MLI layers and Case 8 with 40 MLI layers, where the insulation thickness was greatest. Under the same number of layers, the temperature gradient became more gradual as the MLI thickness increased. In addition, the temperature variation in the tank head region indicated that increasing the number of MLI radiation layers reduced the radiative heat flux, resulting in a gentler temperature variation and a longer temperature drop range. Furthermore, the analysis of heat transfer and BOR showed that both rates decreased under the condition with the greatest MLI thickness and number of layers, demonstrating the best insulation performance. In particular, under the same 40-layer condition, the BOR value of Case 8 was more than three times lower than that of Case 5, indicating a significant improvement in thermal insulation efficiency.

This study investigates the thermal behavior of H7 halogen headlamps through Computational Fluid Dynamics(CFD) analysis and experimental validation. Headlamp geometries were reconstructed via reverse engineering, and simulations incorporated conduction, convection, and radiation effects using the Discrete Ordinate (DO) model. Experiments were conducted using thermocouples and infrared thermography to validate the numerical predictions. The results showed good agreement, with average discrepancies of 3–5% confirming the reliability of the simulation framework. These results demonstrate that current thermo-fluid simulation can accurately capture complex thermal transport phenomena in headlamp assemblies. The proposed methodology is extendable to LED headlamps, providing a practical tool for aftermarket product design, replacement part evaluation, and optimization of next-generation automotive lighting systems.

This study investigates the flow resistance and heat transfer characteristics of a fin-and-tube heat exchanger, applied to a water-cooled thermal management system designed for a cabinet-mounted high-performance computer operating aboard naval vessels. The analysis was conducted through both experimental and numerical approaches, focusing on the evaluation of heat transfer performance (j factor) and flow resistance (f factor) under varying air flow rates, while maintaining a fixed fin geometry and arrangement. Particular emphasis was placed on assessing the variation of the j factor along the total length of the heat exchanger to understand the impact of exchanger length on thermal performance. In the numerical analysis, instead of modeling the entire heat exchanger, a representative repeated unit composed of a single fin and twelve connected tubes was simulated. The outlet temperature from each tube segment was sequentially used as the inlet condition for the subsequent segment. This methodology significantly enhances computational efficiency while providing reliable predictions of progressive thermal characteristics along the flow path.

Graphene, mechanically exfoliated as a single-atom-thick two-dimensional (2D) material, is renowned for its exceptional carrier mobility and mechanical strength, making it a highly promising material for a wide range of applications; however, following the synthesis of large-area, high-quality graphene, quality degradation, such as tearing, frequently occurs during the transfer process. Currently, chemical vapor deposition (CVD) enables reliable synthesis of large-area graphene, and both wet and dry transfer methods are widely employed to transfer graphene onto various substrates. This study focuses on the wet transfer method to improve transfer efficiency by optimizing the interfacial adhesion among graphene, the polymethyl methacrylate (PMMA) support layer, and the target substrate. To enhance the efficiency of the wet transfer process, the PMMA concentration and ultraviolet ozone (UVO) treatment time were systematically optimized. As a result, a transfer yield of up to 97.16 % was achieved under optimized conditions consisting of 6 % PMMA concentration and 15 min of UVO exposure. This research contributes to the development of highly efficient graphene transfer techniques, which are crucial for reducing production costs and processing time in a wide range of advanced applications such as electronics, energy storage, biomedical devices, environmental monitoring, and materials science.

본 연구는 고향사랑기부제가 어떤 제도적 맥락에서 도입되었으며 그 과정에서 드러난 특징과 한계 무엇인가를 분석하기 위해 정책확산과 정 책이전 이론을 활용하는데 목적이 있다. 연구 방법으로는 문헌 검토와 비교 사례분석을 병행하였으며 일본의 제도와 한국의 고향사랑기부제를 법적 근거, 제도 설계, 운영 체계 측면에서 대조하고, 관련 이론의 판정 기준을 사례에 적용하였다. 분석 결과, 첫째, 한국의 고향사랑기부제는 일본 모델을 참조하면서도 국내 재정·행정 환경에 맞게 조정된 혼합적 정책이전의 특징을 보였다. 둘째, 제도 도입 과정은 점진적 확산이 아니 라 중앙정부 주도의 전국적 동시 시행이라는 하향식 확산 경로를 보여 주었다. 셋째, 세제 혜택의 상대적 부족, 법인 기부 불허, 기부금 편중 우려 등은 제도의 효과를 제약하는 요인으로 드러났다. 분석 결과를 토 대로 연구는 첫째, 세제 인센티브 강화, 둘째, 법인 기부 허용을 통한 재 원 다변화, 셋째, 지역 간 불균형 완화를 위한 보정 장치 도입, 넷째, 성 과 중심의 평가 및 환류 체계 구축이 필요하다는 정책적 제언을 제시하 였다. 나아가 본 연구는 고향사랑기부제가 단순한 제도 수용을 넘어 정 책확산과 정책이전이 복합적으로 작동한 사례임을 확인함으로써 지방재 정 확충과 지역균형발전 논의에 의미 있는 시사점을 제공한다.

본 연구는 레벨 3 자율주행의 운전이양권(TOR) 안전성 향상을 위해, 기존 행동 기반 감지 방식의 한계를 극복하 는 운전자 모니터링 시스템(DMS)을 개발했다. 차량의 미러 내장형 RGBW 카메라를 이용한 비접촉 원격 광용적맥 파(rPPG) 기술로 운전자의 심박수를 실시간 측정하고, 심박변이도(HRV) 분석을 통해 졸음, 스트레스 등 운전자의 각성 수준을 판단한다. 딥러닝 기반 얼굴 인식, 신호 처리, 패턴 인식 알고리즘을 통합하여 시스템을 구현했다. 총 28명을 대상으로 105시간 이상의 실제 도로 환경에서 검증한 결과, 심전도(ECG) 대비 85.14%의 심박수 측정 정확 도와 90.81%의 상태 판단 정확도를 달성했다. 본 연구는 생체신호 기반의 운전자 상태 평가가 TOR 판단의 신뢰성 을 높이는 핵심 기술이 될 수 있음을 실증했다.

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.

Co-Cr alloys are widely used in cutting tools and turbine components due to their high strength and resistance against wear and corrosion. However, scrap generated during hardfacing is often discarded due to impurities and oxidation, and research on its recycling remains limited. This study aimed to optimize the recycling process of Stellite 6 scrap to reduce waste and minimize costs while maintaining material quality. Melting, casting, and powdering processes were designed using HSC Chemistry, FactSage, and COMSOL Multiphysics, with optimization of key parameters such as the crucible material and temperature control. The recycled alloy and powder were analyzed using X-ray fluorescence analysis, inductively coupled plasma optical emission spectroscopy, and X-ray diffractometry, showing mechanical and chemical properties comparable to commercial Stellite 6. The Co and Cr contents were maintained, with a slight increase in Fe. These findings demonstrate the potential for producing high-quality recycled Stellite 6 materials, contributing to the sustainable utilization of metal resources in high-performance applications.

Tracing the water snowline in low-mass young stellar objects (YSOs) is important because dust grain growth is promoted and the chemical composition varies at the water snowline, which influences planet formation and its properties. In protostellar envelopes, the water snowline can be estimated as a function of luminosity using a relation derived from radiative transfer models, and these predictions are consistent with observations. However, accurately estimating the water snowline in protoplanetary disks requires new relations that account for the disk structure. We present the relations between luminosity and water snowline using the dust continuum radiative transfer models with various density structures. We adopt two-dimensional density structures for an envelope-only model (Model E), an envelope+disk+cavity model (Model E+D), and a protoplanetary disk model (Model PPD). The relations between the water snowline, where Tdust = 100 K, and the total luminosity, ranging 0.1–1,000 L⊙, are well fitted by a power-law relation, Rsnow = a × (L/L⊙)p au. The factor a decreases with increasing disk density, while the power index p has values around 0.5 in all models. As the disk becomes denser, the water snowline forms at smaller radii even at the same luminosity, since dense dust hinders photon propagation. We also explore the effect of viscous heating on the water snowline. In Model PPD with viscous heating, the water snowline shifts outward by a few au up to 15 au, increasing the factor a and decreasing the power index p. In Model E+D with lower disk mass, the effect of viscous heating is negligible, indicating that the disk mass controls the effect. The discrepancy between our models and direct observations provides insights into the recent outburst event and the presence of a disk structure in low-mass YSOs.

Historically, there have been certain “unsolved cases” objectively, and the transmission of imperial power in the early Song Dynasty is one of them. The succession of Emperor Taizong of Song has been accompanied by numerous speculations and mysteries since ancient times, among which “the sound of an axe and the shadow of a candle”, “The Golden Cabinet Alliance”, and “the mystery of the birth mother of Tingmei” have always been research hotspots in the field of historical studies. On this series of issues, scholars have undergone continuous textual research and analysis on the truth of these “unsolved cases” over several generations, gradually forming several major academic viewpoints, such as the independent transmission theory and the three-transmission theory of “the alliance in the golden coffer”. This has gradually restored the complex political situation in the early Song Dynasty and promoted the understanding and recognition of the political culture in the early Song Dynasty. Based on the research on the issue of establishing the heir in the early Song Dynasty, which was deeply influenced by the Five Dynasties, new insights have been gained into the changes in the inheritance system during the Tang and Song dynasties, and a theory comprehensively elaborating on the inheritance system has been constructed. From an institutional perspective, this summarizes the objective patterns of change that existed during the Tang, Five Dynasties, and early Song dynasties, interprets the complex political “unsolved cases” and political culture in the early Song Dynasty, and forms a re-examination and new understanding of the issue of imperial power transfer in the early Song Dynasty.

본 연구는 국제경영전략 관점에서 해외자회사가 이전한 지식은 기업 경쟁력 강화에 언제나 긍정 적일 것이라는 가정을 비판하기 위해, 해외자회사의 역지식이전 수준과 기업성과 간 관계를 분석하 였다. 글로벌 기업 직원 256명을 대상으로 설문조사한 결과, 해외자회사가 본사로 이전한 지식 수 준이 높을수록 높은 기업성과를 보이는 것으로 나타났다. 그러나 이러한 효과는 해외자회사의 역량 및 해외자회사와 본사 간 비전공유 수준에 따라 차이를 보이는 것으로 나타났으며, 해외자회사의 역량이 낮거나, 비전공유 수준이 낮은 조직의 역지식이전은 기업성과에 부정적 영향을 제공하는 것 으로 나타났다. 이를 통해 본 연구는 역지식이전 과정에서 글로벌 기업의 형태적 통제기제와 사회 적 통제기제가 요구되고 있음을 제시하였다.

In this study, a numerical analysis study on the heat transfer characteristics according to the opening and closing of the hydrogen shut-off valve was performed, and the temperature distribution of the key components of the hydrogen shut-off valve was predicted through the result. The ANSYS CFX program was used to predict the heat transfer characteristics of the hydrogen shut-off valve. When the hydrogen shut-off valve was open, the average temperature of the O-ring, which prevents hydrogen leak inside the solenoid valve, was approximately -40℃, and the plunger showed a maximum of -40℃ and a minimum of -110℃. When the hydrogen shut-off valve was completely closed, the O-ring showed approximately 24.82℃ and the plunger showed approximately 24.71℃, which were almost at room temperature.

In four-wheel-drive vehicle, improving traction with the road surface enhances the vehicle's ability to respond to various driving conditions, increasing its overall versatility. Consequently, various studies have been conducted on four-wheel-drive vehicles that support torque distribution through electronic control. The driving unit that operates the transfer case assists in smooth torque distribution by providing high torque. Therefore, this study developed a reduction mechanism by vertically arranging a planetary gear set in the driving unit to increase the reduction ratio. To achieve this, a common ring gear with 52 teeth was used, and the design included a first-stage planetary gear with a sun gear having 18 teeth, a planet gear with 17 teeth, a second-stage sun gear with 12 teeth, and a planet gear with 20 teeth. The corresponding tooth profiles and structures were also designed. Based on this, a transfer case drive reduction module was developed, which improved torque performance: the first-stage planetary gear system provides 4.23 kgf·m of torque, and the second-stage planetary gear system achieves a final torque of 5.98 kgf·m