히트파이프 모세관 성능 개선을 위한 스크린-메쉬 윅의 표면 개질

정지윤,임혜원,김혜원,이상민,김형모,Jeong, Jiyun,Lim, Hyewon,Kim, Hyewon,Lee, Sangmin,Kim, Hyungmo 한국트라이볼로지학회 2022 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.38 No.5

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

APR1400 원자로와 원자로 헤드 결합 부위의 스터드볼트 나사산 여부에 따른 응력 상태 분석

정지윤(Jiyun Jeong),남궁인(Ihn Namgung) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

In NPP, reactors are consisted of reactor vessels, closure head, upper guide structure and internal structures. The reactor vessel is fastened with stud bolts and seal ring to prevent leakage of high-temperature and high-pressure coolant. In this study, stresses at the reactor vessel and the closure head assembly area were studied. The stud bolts were modeled in two ways: 1) a simplified model with a thread removed, and 2) a more detailed model including bolt threads to consider the thread effect. The maximum stress near bolt thread area was found to be about 3 times bigger than the model without thread. Stresses of other parts of models showed similar values. This study showed that the importance of detailed modeling of bolts in general and it makes significant difference. If the area of interests do not include stud bolt, a simplified model is enough to calculate RV and closure head assembly.

패턴 형상 및 입사각에 따른 Wire Grid Polarizer의 편광 특성 해석

정지윤(JiYun Jeong),조영태(YoungTae Cho),정윤교(Yoon-Gyo Jung) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.3

With the development of technology, the display industry has been focusing on the development of new types of displays, such as bendable and wearable displays. However, the PVA/TAC polarizing film used in the manufacturing of a normal display is associated with low luminance and low efficiency. If the existing polarization film is replaced with a wire grid polarizer, it is possible to reduce the thickness significantly. Moreover enhanced brightness can also be expected. This study confirms the optical properties of the WGP through a simulation.

원자로 및 원자로 덮개의 운전 상태에 따른 조립 하중 변화 분석

정지윤(Jeong Jiyun),남궁인(Namgung Ihn) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

원자력발전소의 원자로는 노심에 핵연료를 설치하여, 핵분열을 통해 열을 발생하는 중요한 장치로서 노심을 안전하게 방사성물질의 누출을 방지하는 압력경계를 이루는 핵심적인 부분이다. 원자로압력용기는 원자로와 덮개로 이루어지며, 고온·고압의 냉각재가 새지 않도록 스터드 볼트와 실링으로 체결되어 있다. 원자로는 정지상태에서 정상상태로 운전상태가 변동되며, 스터드 볼트에 작용하는 체결력에 변동이 발생한다. 즉 원자로 조립부 주위의 온도 및 압력 변화에 따라 압력용기(RV)와 덮개(Closure Head Assembly) 사이의 체결력에 변화가 발생한다. 본 연구에서는 원자로와 덮개의 조립부위 체결력의 변화를 연구하였다. APR1400 원자로는 54개의 스터드 볼트로 덮개와 원자로를 조립한다. 스터드 볼트는 원주방향으로 패턴을 이루므로, 1/54 축대칭 3차원 FEM 모델을 개발하였다. 원자로 플랜지 조립부의 원자로 플랜지, 상부안내구조물 플랜지, 압축링, 노심지지구조물 플랜지, 스터드 및 너트에 대한 모델을 개발하였고, 각 부품 사이의 하중전달경로 해석을 통해 경계조건을 구하였다. 열해석-구조해석을 연계한 연성 FEM 해석을 원자로의 정지상태에서 정상운전상태로 변화에 대해 해석하여 원자로 조립부의 하중변화를 구하였다. 이 해석을 통해 원자로 덮개와 원자로 간의 조립하중과 내부구조물의 조립하중의 분배를 분석하였다. In Nuclear Power Plant, reactor contains nuclear fuels that produces heat through fission reaction and acts as important pressure boundary to prevent leakage of radioactive material. Reactor pressure vessel consists of reactor and closure head and is assembled by stud and nut and seal ring to prevent leakage of high-temperature and high-pressure coolant. Reactor operates between shut-down to normal operation, as a result the stud-bolt assembly load also experiences assembly load changes. In other word, at the assembly of reactor and closure, the assembly load changes due to temperature and pressure changes. In this study, we assess the pattern of assembly load change at the reactor and closure head assembly region. In APR1400, 54 stud bolts are installed to assemble closure head to reactor vessel. To take advantage of the rotational pattern of stud installation, we developed 1/54 axis symmetry 3D FEM model. Within reactor flange region of assembly, RV flange, UGS flange, HDR, CSB flange, stud and nut are modeled and performed load path analysis to get load boundary condition. A thermal-structural analysis was done to simulate assembly loading of reactor from shutdown to normal operation. The analysis reveals change of load sharing of internals and closure head to vessel.

Variation of a Triangular Pattern Shape due to Shrinkage in the Repeated UV Imprint Process

Jiyun Jeong(정지윤),Su Hyun Choi(최수현),Young Tae Cho(조영태) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.7

Shrinkage is inevitable in the curing of resins during the nanoimprint process. The degree of shrinkage that occurs as the resin transforms from a viscous liquid to solid differs depending on the type of resin. However, if the cured material is repeatedly cured using the same material, constant shrinkage can be confirmed. In this study, the pattern of change was observed by repeatedly performing the nanoimprint process using a resin with a constant shrinkage rate. The observed pattern for the change of shape was made using a triangular pyramid-shaped aluminum master mold and a flexible replica mold made from the master. Shrinkage that results from the nanoimprint process occurs linearly in the longitudinal direction of the pattern and can be predicted by simple calculations. The change of the pattern due to shrinkage occurred as expected. If the shrinkage rate remains constant, various patterns can be manufactured with high accuracy by correcting these changes before producing a specific shape. This study confirms that the pattern of the desired angle can be obtained by performing the repeated imprint without having to manufacture a master mold.

미세 표면 구조에 의한 스테인리스 스틸 스크린-메쉬 윅의 모세관 성능 향상

정지윤(Jiyun Jeong),임혜원(Hyewon Lim),김혜원(Hyewon Kim),김형모(Hyungmo Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

미세 표면 구조에 의한 스테인리스 스틸 스크린-메쉬 윅의 모세관 성능 향상

정지윤(Jiyun Jeong),임혜원(Hyewon Lim),김혜원(Hyewon Kim),김형모(Hyungmo Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

응급환자 추이예측 분석 : AMI, Stroke, ICISS 기반 중증질환자

정재연 ( Jeong Jaeyeon ),정지윤 ( Jeong Jiyun ),이해종 ( Lee Haejong ) 경희대학교 경영연구원 2021 의료경영학연구 Vol.15 No.1

Purpose: The purpose of this study is to identify the trends and seasonality of the three major emergency diseases(Acute myocardiac infarction, Stroke, Severe trauma) and to use them to establish efficient resources and evidence-based physicians to predict the number of patients. Methodology: From 2014 to 2018, the number of patients who received emergency medical care for acute myocardial infarction, stroke, and severe trauma (based on ICISS 2008) was predicted using Emergency Medical Status Statistics provided by the National Medical Center. Based on the Autoregressive integrated moving average model, the increasing trend and seasonality of patients by disease were confirmed and the number of patients was predicted. Findings: Since 2014, the number of patients with emergency diseases has steadily increased, with the highest number of patients in the order of Severe trauma (based on ICISS 2008), Stroke, and Acute myocardiac infarction. Patients with cerebrovascular disease, such as Acute myocardiac infarction and stroke, increased rapidly in winter(Oct-Jan), and patients with severe trauma increased mainly in summer or autumn(May-Oct) and number of patients will increase with seasonality. Practical Implications: The number of major emergency patients is expected to increase steadily over time, so it is important to be prepared for this. Therefore, providing emergency care with limited resources is a very important issue, and in order to prepare for the growing elderly population, emergency medical patients, and unpredictable infectious diseases, it is necessary to keep track of the number of patients for each emergency disease.

지장물 존치 농경지 토양개량 및 복원방안 고찰

인현진 ( Hyunjin In ),정지윤 ( Jiyun Jeong ),고석호 ( Seokho Goh ),하지연 ( Jiyeon Ha ),김현진 ( Hyeonjin Kim ),고주인 ( Juin Ko ),박관인 ( Kwanin Park ),유찬 ( Chan Yu ) 한국농공학회 2022 한국농공학회 학술대회초록집 Vol.2022 No.-

우리나라에서는 체계적인 광해방지사업 추진을 위하여 전국의 폐광산 및 휴지광산, 가행광산에 대해 5년마다 실태조사를 실시하여 광해방지기본계획 및 사업계획에 반영하고 있다. 한국광해광업공단의 22021년 광해실태조사 결과에 의하면 전국 5,475개 휴·폐광산 중 3,300개 광산에서 광해가 발생하는 것으로 파악되고 있다. 한편 한국광해광업공단에서는 2007년부터 광산 주변 광해 오염 농경지에 대한 토양개량 및 복원 사업을 지속적으로 추진해 왔는데, 2021년까지 3차에 걸쳐서 약 3,000여개소에 대한 복원이 완료된 것으로 보인다. 그런데 광산 주변 토양오염 농경지 중 과수 및 시설재배 농지의 경우에는 현장의 농업용 수목 및 시설 지장물로 인하여 경작자 혹은 소유주의 동의가 없으면 원활한 복원사업의 진행이 어려운 문제점이 있었다. 즉 최근까지는 소유주가 지장물 자가철거 및 재설치를 할 경우에만 사업이 진행되고 있었다. 물론 전체 복원사업에서 지장물이 포함된 경우는 비중이 높지는 않았다. 그러나 한편으로는 그 비중이 높은 경우 사업지구도 있고 특히 유독한 성분으로 오염되어 적극적인 복원이 필요한 경우에는 대안 마련이 필요하였다. 이와 관련하여 광산피해방지법 개량(2020.3)으로 토양개량·복원사업을 위해 토지사용이 가능(강제)하게 되어 보다 적극적인 복원사업의 진행이 가능한 여건이 마련되었다고 볼 수 있다. 따라서 본 발표에서는 지장물이 존치될 수 밖에 없는 과수 농지 및 시설재배 농지복원을 위한 현황조사 및 국내외 관련 기술을 정리하여 발표하였다.

60mm수형박격포 개발

김영섭 ( Youngseop Kim ),정지윤 ( Jiyun Jeong ),홍창기 ( Changki Hong ) 한국국방기술학회 2022 한국국방기술학회 논문지 Vol.4 No.4

본 연구는 60mm수형박격포 개발에 대한 연구이다. 60mm수형박격포의 운용방식을 분석하였으며, 기존 일반적인 박격포와의 차이점을 검토하였다. 세계적으로 주요한 수형박격포에 대해 장단점을 분석하였다. 대한민국형 60mm수형박격포 시제품을 개발하였으며, 실제 사격시험을 수행하여 그 결과를 기술하였다. 또한 대한민국 육군과 해병대의 전술적 운용개념을 제안하였다. This study is a on the development of a 60mm handheld(Commando) mortar. The operation method of the 60mm handheld(Commando) mortar was analyzed, and the difference between the operation method of the conventional 60mm mortar and the operation method was examined. We reviewed the world's major 60mm handheld(Commando) mortars and analyzed their advantages and disadvantages. A prototype model of the Korean handheld(Commando) mortar was developed, and the actual shooting test results were described. In addition, we will present tactical operation plans for the Republic of Korea Army and Marine Corps.