https://scholarworks.unist.ac.kr/handle/201301/61 2026-04-19T14:10:16Z https://scholarworks.unist.ac.kr/handle/201301/91356 Title: Can the Finite Element Method Be Applied to Patient-Specific Implant Evaluation? Author(s): Lee, Suyeon; Park, Hyenmin; Kang, Hyun Guy; Kim, June Hyuk; Jung, Im Doo; Park, Jong Woong Abstract: Background: The introduction of 3-dimensional printing has revolutionized orthopedic surgery, enabling patient-customized implants to address complex bone defects. However, ensuring reliable fixation remains a considerable challenge. Herein, we developed a finite element analysis (FEA)-based flow designed to evaluate implant fixation across various anatomical sites. Methods: We applied this flow to the pelvic region to validate its fixation strategies and optimize the design across different osteointegration stages: acute, pre-, and post-osteointegration. Effects of screw-fixation methods (short screws in the cancellous bone and long screws in the cortical bone) on patient outcomes were analyzed and validated using data from 2 patients. Results: Predictive outcomes aligned closely with clinical results in terms of the location and timing of screw-fixation failure. Conclusions: The study findings affirm the potential of FEA to verify implant design and fixation strategies and to enhance surgical success rates through improved preoperative planning. 2026-03-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91351 Title: Heteroatom-Doped Nickel Oxide for Electrooxidation of Methanol Author(s): Pathak, Navanil; Sarmah, Hemanga Jyoti; Dewri, Ashawari; Kim, Donguk; Park, Young-Bin; Bania, Kusum K. Abstract: The current study emphasizes understanding the impact of impurities on the electrocatalytic efficiency of nickel oxide (NiO) for the methanol oxidation reaction (MOR) in 1 M KOH. It was evident that NiO with p-block elements, like boron (B) and sulfur (S), showed remarkable MOR activity with a low onset potential and better kinetic profile. NiO having both B and S exhibited MOR at a very low onset potential of 1.38 V vs RHE and a reduced Tafel slope of 42 mV dec-1. However, NiO having either B or S as an impurity showed onset potentials of 1.41 and 1.33 V vs RHE with higher Tafel slope values of 106 and 133 mV dec-1, respectively. The significant MOR activity of NiO with a low content of S and a slightly higher content of B was attributed to the change in the electronic structure with the reformation of the Fermi levels as evident from the density of states (DOS) and projected density of states (PDOS) calculations. Doping with B and S lowered the Fermi level of NiO from 2.196 to 2.070 eV. The doped NiO material also showed high stability and durability in an alkaline medium and retained the electrochemical activity for up to 12 h. The overall MOR process was investigated through FTIR and Raman studies. From the spectroscopic analyses, it was confirmed that the MOR proceeded via the formation of intermediates such as formate and carbonate. 2026-02-28T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91338 Title: Balancing bubble dynamics and liquid replenishment in a two-phase closed thermosyphon via geometrically tuned Bi-philic evaporator surfaces Author(s): Kim, Gyuchang; Lee, Jaeseon Abstract: Bi-philic surfaces are known to enhance pool boiling, yet their application in liquid-supply-limited systems like two-phase closed thermosyphons (TPCTs) remains underexplored. This study experimentally investigates the thermal performance and flow dynamics of a rectangular TPCT featuring vertically aligned bi-philic evaporator stripes. Using a masking technique with alkali etching and nanoparticle dip-coating, four configurations with varying hydrophilic/hydrophobic stripe widths (2/2, 2/4, 4/2, and 4/4 mm) were fabricated. High-speed visualization revealed that bubble dynamics are governed by the interplay between contact-line pinning on hydrophobic stripes and capillary-driven liquid replenishment along hydrophilic channels. The 4/2 pattern (4 mm hydrophilic / 2 mm hydrophobic) achieved optimal performance, reducing overall thermal resistance by 30% compared to a bare copper surface. Visualization results demonstrated that limiting the hydrophobic width to 2 mm induced contact-line pinning, constraining bubble growth (similar to 2.3 mm), while wider 4 mm hydrophilic stripes minimized hydraulic resistance for liquid return, preventing local dry-out. This geometric optimization shifted the system's thermal bottleneck to the condenser. These findings establish critical design criteria for bi-philic TPCTs: hydrophilic widths must be sufficient to sustain capillary supply, while hydrophobic widths must be constrained to regulate bubble growth under liquid-limited conditions. 2026-05-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91302 Title: A universal approach to understanding cryogenic quenching in pool boiling Author(s): Koo, Heeyeong; Lee, Jongbin; Jeong, Minsub; Lee, Kyungwon; Yoon, Aejung Abstract: This study experimentally and theoretically investigated the effects of material properties and geometric dimensions on quenching process of a flat plate in a liquid nitrogen pool. Quenching experiments were performed using stainless steel, aluminum, and copper plates with thicknesses ranging from 0.3 to 5.0 mm. Experimental results showed that the minimum heat flux (MHF) temperature increased as the plate heat capacity per unit area decreased. A theoretical model was developed to predict the MHF temperature and regime transition time, defined as the time required to reach the MHF point, and agreed well with experimental data, with MAPEs of 7.1% and 14.9%, respectively. The theoretical model identified three parameters governing quenching: (1) lumped capacitance time scale associated with transient heat conduction, (2) excess MHF temperature, and (3) local temperature drop resulting from liquid-solid contact. According to the first parameter, the regime transition time is linearly proportional to the heat capacity. The second one describes the dependence of MHF temperature on heat capacity, with smaller heat capacity leading to higher MHF temperature and shorter regime transition time. The third one accounts for thermal effusivity and diffusivity effects on regime transition, which are negligible when these properties are sufficiently high. Finally, a universal approach to understanding quenching is proposed: the contribution of transient conduction can first be isolated, as evidenced by the collapse of quenching curves onto a single curve independent of material and geometric parameters. This, in turn, enables a systematic analysis of the effects of individual parameters on regime transition. 2026-08-31T15:00:00Z