• 산업융합연구
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• 제21권8호
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• pp.43-49
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• 2023

2018년부터 기후변화에 따른 폭염과 한파에 의해 사회기반시설에 점증적으로 많은 피해를 미치고 있다. 최근 4년간 기후변화에 따른 영향 중에 냉해에 대한 피해가 매년 증가하여 특정 지역에 국한되었던 피해가 이제는 전국에 걸쳐서 나타나고 있으며, 이를 최소화하기 위한 각계각층의 전문가들에 의한 노력이 집중되고 있다. 그러나 불연속적으로 측정되는 데이터들 속에서 지역 특색을 반영하고자 하는 기존 연구들에서는 갑작스럽게 발생하는 이상 저온에 대한 실시간 관측 연구는 쉽지 않은 상황이다. 본 연구에서는 냉해 발생에 영향을 미치는 기상 데이터를 기준으로 냉해 피해가 발생하였던 시점의 기상 패턴을 탐색한 후 이상저온 발생 시점을 확인할 수 있는 알고리즘 패턴 개발을 하였다. 본 연구의 결과물은 과거의 데이터에 의존하지 않고 실시간으로 발생하는 데이터에 의한 이상저온이 발생한 시점을 시간 시점에서 확인할 수 있다는 점에서 지역적 기상 편차를 의식하지 않고 확인이 가능하다는 점에서, 이상저온 발생 시점 데이터를 확보할 수 있다는 점에서 관련 분야에 많은 도움이 될 것으로 기대할 수 있다.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.70-74
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• 2023

The Small Punch Test (SPT) was developed to evaluate the softening and embrittlement of materials such as power plants and nuclear fusion reactors by taking samples in the field. Specimens used in the SPT are very thin and small disk-shaped compared to specimens for general tensile test, and thus have economic advantages in terms of miniaturization and repeatability of the test. The cryogenic SPT can also be miniaturized and has a significantly lower heat capacity than conventional universal test machines. This leads to reduced cooling and warm-up times. In this study, the cryogenic SPT was developed by modifying the existing room temperature SPT to be cooled by liquid nitrogen using a super bellows and a thermal insulation structure. Since the cryogenic SPT was first developed, basic experiments were conducted to verify the effectiveness of it. For the validation, aluminum alloy 6061- T6 specimens were tested for mechanical properties at room and cryogenic temperature. The results of the corrected tensile properties from the SPT experiment results were compared with known room temperature and cryogenic properties. Based on the correction results, the effectiveness of the cryogenic SPT test was confirmed, and the surface fracture characteristics of the material were analyzed using a 3d image scanner. In the future, we plan to conduct property evaluation according to the development of various alloy materials.

• 한국분말재료학회지
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• 제30권5호
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• pp.387-393
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• 2023

Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni₃Co₆S₈-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni₃Co₆S₈@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni₃Co₆S₈@C-YS exhibited an impressive reversible capacity of 525.2 mA h g^-1 at a current density of 0.5 A g^-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni₃Co₆S₈ yolk shell nanopowder (Ni₃Co₆S₈-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni₃Co₆S₈@C-YS were attributed to the pitch-derived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

• 한국산업융합학회 논문집
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• 제26권6_2호
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• pp.1019-1024
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• 2023

Ceramic materials have excellent material properties such as stability at high temperatures, chemical stability, corrosion resistance, and wear resistance, so they are applicable even in extreme environments of high temperature and pressure. In particular, silicon carbide can be applied in the field of structural ceramics due to its characteristics of high strength, hardness, corrosion resistance, and heat resistance even at high temperatures. In this study, considering the application of silicon carbide materials to next-generation turbines, silicon carbide materials were manufactured using a liquid phase sintering method. When manufacturing liquid phase sintered silicon carbide, sintering additives were added to lower the sintering temperature and densify the material. In Al₂O₃-SiO₂, it was confirmed that the secondary product of the sintering additive was observed as a slightly dark area and was evenly distributed overall, and the fracture surface of Al₂O₃-SiO₂ was in the form of transgranular fracture in which cracks progressed along the crystal plane, and the flexural strength for Al₂O₃-SiO₂ was about 445.6 MPa.

• 한국표면공학회지
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• 제56권6호
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• pp.437-442
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• 2023

This research aims to enhance the efficiency of Pt/C catalysts due to the limited availability and high cost of platinum in contemporary fuel cell catalysts. Nano-sized platinum particles were distributed onto a carbon-based support via the polyol process, utilizing the metal precursor H₂PtCl₆·6H₂O. Key parameters such as pH, temperature, and RPM were carefully regulated. The findings revealed variations in the particle size, distribution, and dispersion of nano-sized Pt particles, influenced by temperature and pH. Following sodium hydroxide treatment, heat treatment procedures were systematically executed at diverse temperatures, specifically 120, 140, and 160 ℃. Notably, the thermal treatment at 140 ℃ facilitated the production of Pt/C catalysts characterized by the smallest platinum particle size, measuring at 1.49 nm. Comparative evaluations between the commercially available Pt/C catalysts and those synthesized in this study were meticulously conducted through cyclic voltammetry, X-ray diffraction (XRD), and field-emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM EDS) methodologies. The catalyst synthesized at 160 ℃ demonstrated superior electrochemical performance; however, it is imperative to underscore the necessity for further optimization studies to refine its efficacy.

• 한국표면공학회지
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• 제56권6호
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• pp.380-385
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• 2023

In this study, an MPB PMNT system containing 0.05 to 0.10 wt.% BaTiO₃ was synthesized using a traditional chemical method and its pyroelectricity was investigated. Pyroelectricity, dielectricity, and ferroelectricity of the synthesized BaTiO₃-PMNT system were analyzed by heat treatment at 1240~1280 ℃ for 4 hours to evaluate its applicability as a pyroelectric sensor. Unlike the simple ABO₃ ferroelectric, the BaTiO₃-doped PMNT system exhibited phase transition characteristics over a wide temperature range typical of complex perovskite structures. Although no dramatic change could be confirmed depending on the amount of BaTiO₃ added, stable pyroelectricity was maintained near room temperature and over a wide temperature range. When the amount of BaTiO₃ added increased from 0.05BaTiO₃-PMNT to 0.10BaTiO₃-PMNT, the electric field slightly increased from 5.00×10³ kV/m to 6.75×10³ kV/m, and the maximum value of remanent polarization slightly increased from 0.223 C/m² to 0.234 C/m². The pyroelectric coefficients of 0.05BaTiO₃-PMNT and 0.10BaTiO₃- PMNT at room temperature were measured to be ~0.0084 C/m²K and ~0.0043 C/m²K, respectively. The relaxor ferroelectric properties of the BaTiO₃-PMNT system were confirmed by analyzing the plot of K_max/K versus (T-T_max)^γ. The BaTiO₃-doped MPB PMNT system showed a distinct pyroelectric performance index at room temperature, and the values were F_v ~ 0.0362 m²/C, F_d ~ 0.575×10^-4 Pa^-1/2.

• 한국안전학회지
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• 제39권1호
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• pp.55-61
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• 2024

In response to the COVID-19 pandemic, the logistics industry in Korea has rapidly been expanding, with offline demand concentrating on online platforms owing to the development of digital infrastructure. This has increased the workload of courier drivers considerably, along with labor intensity. A delivery driver died recently from overwork due to the continuous increase in delivery volume, which raises social concerns. Delivery drivers work long hours, (over 12 hours) and are greatly affected by weather conditions, such as snow, rain, heat waves, and cold waves. In addition, they lack a fixed workplace; perform atypical work handling workpieces of various sizes, weights, and shapes; and spend a large amount of time driving as part of their work. This work involves a high level of tension and requires attention and concentration. Despite the frequency of industrial accidents in the courier industry, studies on safety and health to quantitatively analyze and systematize the work of courier workers are very scarce. Therefore, to define the work process necessary for investigating the harmful factors in delivery service and the work analysis, this study conducted interviews and on-site surveys to analyze the unit work of the delivery service by targeting delivery workers. In other words, a framework of unit work for work analysis was presented to enable research and analysis by considering the aforementioned characteristics of the courier industry. The process was broadly divided into work, transport, storage, delay, and inspection. Work was divided into loading, sorting, unloading, and door subcategories, and transportation was divided into vehicle, cart, and walking subcategories as well as 10 small processes. Moreover, 22 unit works were again drawn by conducting field surveys and interviews. The risk of unit work derived from this study was ergonomically evaluated, and the ergonomic analysis revealed that uploading and transportation were the most dangerous. The results of this study could be used as basic data for preventing industrial accidents among courier workers, whose work has increased with the logistics volume and the development of the logistics industry.

• 풍력에너지저널
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• 제14권4호
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• pp.50-56
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• 2023

With the abnormal weather phenomena caused by global warming, the frequency and intensity of lightning strikes are increasing, and lightning accidents are becoming one of the biggest causes of failures and accidents in offshore wind turbines. In order to secure generator operation reliability, effective and practical measures are needed to reduce lightning damage. Because offshore wind turbines are tall structures installed at sea, the possibility of direct lightning strikes is very high compared to other structures, and the role of surge protection devices to minimize damage to the electrical and electronic circuits inside the wind turbine is very important. In this study, a varistor, which is a key element for a class 1 surge protection device for direct lightning protection, was developed. The current density was improved by changing the varistor composition, and the distance between the electrode located on the varistor surface and the edge of the varistor was optimized through a simulation program to improve the fabrication process. Considering the combined effects of heat distribution, electric field distribution, and current density on the optimized varistor surface, silver electrodes were formed with a gap of 0.5 mm. The varistor developed in this study was confirmed to have an energy tolerance of 10/350 ㎲, 50kA, which is a representative direct lightning current waveform, and good protection characteristics with a limiting voltage of 2 kV or less.

• Radiation Oncology Journal
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• 제9권1호
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• pp.27-35
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• 1991

8MHz 라디오파를 이용한 자입식 온열치료를 위한 기초실험의 일환으로 조직등가물을 이용하여 다양한 needle electrode의 배열을 통한 적정 온도분포를 규명하고자 하였고, 직접 개의 뇌실질에 자입 온열요법을 시도하여 이에 따른 조직 병리학적 소견을 관찰하고자 하였다. 조직등가물 실침에서 저자들은 needle electrode 1 cm 간격의 정방형 배치에서 횡단면상 $90\%$ relative SAR 분포가 약 1.25 cm 반경의 균일한 원형으로 관찰됨을 알 수 있었고 종단면상 needle electrode의 길이에 따라 균일한 온도분포가 이루어짐을 관찰할 수 있었다. 정상 개의 뇌실질에 자입하여 직접 정방형의 중심을 $43^{\circ}C$로 유지하며 50분간 온열요법을 시행한 후 관찰한 조직 병리학적 소견은 liquefactive necrosis, pyknosis of neuronal element 및 Polymorphonuclear leukocytes들이 회백질에서 급성기에 관찰 되었고 liquefactive necrosis 주위에 lipid-laden macrophage들이 관찰됨이 공통적인 특징 이었으며 후기 변화로 괴사조직 주위로 신경교세포의 증식이 관찰되었다.

• 한국작물학회지
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• 제47권6호
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• pp.395-401
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• 2002

보리의 조숙 품종을 육성하기 위해서는 조기 출수인자에 단기 등숙성 인자를 도입하는 것이 중요하므로 출수기, 성숙기 및 등숙기간의 유전에 관한 정보를 얻고자 4개 품종(사천6호, 오월보리, 동보리1호, Reno), F$_1$, F$_2$세대의 종자를 포장에 파종, 재배하여 출수기, 성숙기 및 등숙기간을 조사하였다. 1. 출수기는 4월 3일-4월 26일, 성숙기는 5월 15일-5월 27일, 등숙기간은 31일-42일로 교배친 및 F$_1$ 조합간 차이가 현저하였다. 2. 부분 이면교잡에 의한 분산분석 결과, 출수기에 대해서 동보리1호(출수기 늦음)는 우성으로, 오월보리는(출수기 빠름) 열성으로, 출수기 유전은 유전자의 상가적 작용이 큰 부분우성으로 나타났다. 3. 성숙기에 대해서 동보리 1호가 우성으로, 오월보리가 열성으로, 성숙기 유전은 유전자의 상가적 작용 큰 부분우성으로 나타났다. 4. 등숙기간에 대해서 Reno(등숙기간이 짧음)가 우성으로 오월보리(등숙기간이 길음)은 열성으로 유전자의 상가적 작용이 큰 부분우성으로 나타났다. 5. 출수기, 성숙기에 대한 일반조합능력의 분산량은 고도의 유의성이 인정되고, GCA분산이 SCA분산보다 출수기는 10.1-29.5배, 성숙기는 9.9-121배 높아서 유전자의 상가적 작용이 컸으며, 사천6호와 오월보리는 출수와 성숙이 빠른 방향으로, 동보리 1호와 Reno은 늦어지는 방향으로 효과를 보였다. 6. 등숙기간에 대해선 GCA 효과는 F$_1$과 F$_2$ 세대간 유의적 차이가 있었고 GCA/SCA비가 크므로 유전자의 상가적 작용이 현저하였다. 7 포장 출수기, 성숙기는 결빙방지 단백질의 농도, 광합성의 광저해에 대한 내성, 포장 내동성과 고도의 정의 상관을, 등숙기간은 각 형질들과 부의 상관을 보였다. was "glossy and smooth" in all cases and preference about the texture was high. The Doenjang with added P. japonica Powder had a saltier taste and the Doenjang with P. japonica Powder had the least sweet taste. In the flavor and overall Preference, the Doenjang with P. japonica powder was the lowestEX>로 측정되었고, 계사내 지붕의 표면 온도는 최고 $29^{\circ}C$가 측정되었다. 계사 내 표면 온도 및 닭의 표면 온도는 계사내 공기온도의 영향을 많이 받는 것으로 나타났다.ill in a good agreement with those predicted by Rohsenow's formula, which was based on nucleate boiling. For the condenser, the wall temperatures were practically uniform, and the measured values of condensation heat transfer coefficient were 1.7 times higher than the predicted values obtained from Nusselt's film condensation theory on tilted plate. Using those two expressions, a correlation was formulated as a function of heat flux and tilt angle, to determine the total thermal resistance of a tilted thermosyphon.