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정동호(DongHo Jung),송제하(JaeHa Song),신승호(SeungHo Shin) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.6
In this paper, the mooring system for a floating wave energy farm is designed based on a two-dimensional analysis. The mooring system uses an anchorless mooring line linking two floaters in a floating wave energy farm. The basic equation to determine the length of the mooring line between the two floaters is proposed. The other properties such as the diameter and pretension are taken from the mooring line for a single floater. The dynamic behavior and safety of the designed mooring system under extreme ocean conditions are analyzed with the commercial software Orcaflex. A numerical study shows the stability and high safety in tension of the designed mooring lines for a floating wave energy farm. The proposed anchorless mooring system for a floating wave energy farm results in a considerable reduction in the length of the mooring line, contributing to the economics of a floating wave energy farm.
KSLV-I 나로 우주센터 조립동 및 발사대 파티클 검사
정동호(Dongho Jung),임하영(Hayoung Lim),이무근(Mukun Yi),이수진(Soojin Lee) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
나로호의 3차례 운용을 위해 우주센터 조립동과 발사대의 가스품질 검사를 수행했다. 설비 구축후 초기에는 많은 시행착오를 겪었으나, 시간이 지날수록 설비도 깨끗해지고, 검사 방법도 개선되어 실제 운용시점에는 불합격을 찾아보기 힘들었다. 가스품질 검사는 단순하게 검사만 하는 것이 아니고, 이 검사를 통해 발사체에 가스를 공급할 준비가 되었다는 선언적 의미를 가진다. For the three times launch operation of the NARO, the gas quality check was perfumed at assembly building and launch pad in NARO space center. after much trail and error, the gas supply system and the gas quality check methodology was improved. we can controlled gas supply facility and gas quality when is the real launch operation. the gas quality check is not a simple inspection, it has a meaning to conform the state of ground gas supply system ready to supply gas to the launch vehicle.
그래프 이론 기반 적층제조 온톨로지 데이터베이스 개발과 활용
정동호(Dongho Jung),안재승(Jaeseung Ahn),유현재(Hyunjae Yoo),박여춘(Yeochoon Park),박상인(Sang-in Park) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The ontology is a knowledge representation method by defining a set of concepts in a certain domain and abstracting relationship among concepts. In recent research, the ontology scheme has been applied to establish knowledgebase of additive manufacturing (AM) systems because AM processes utilize various physical phenomena resulting complex relationships among diverse parameters across modeling, material, and process domains. The goal of this research is to construct an additive manufacturing knowledgebase using the ontology scheme with graph representation. To do this, we firstly developed the class structure and defined relationships among the classes based on a structure of working principles structure for given additive manufacturing device. Next, we employ concept of a weight factor, which is a measure for a level of importance or impact of relationships. Finally, we convert the developed ontology representation to graph representation with proposed weight factors. The developed knowledge presentation approach is applied to construct knowledge-base for a material extrusion additive manufacturing system and verified using examples.
정동호(Dongho Jung),조기주(Kiejoo Cho),오승협(Seunghyub Oh) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11
추진제 탱크와 배관의 연결부에 대한 개념 설계단계로 해외 발사체의 배관 연결부를 조사하였고, 그 결과를 토대로 몇가지 대표 형상을 선정하여 유동해석을 수행하였다. 유동해석 결과 배관의 연결부 중 제일 유동특성이 좋은 것을 찾을 수 있었다, 하지만 큰 차이는 없었다. 그 이유는 배관이 길어서 배관 내부를 유체가 흐르면서 배관 내부 유동이 안정되는 것으로 판단된다. The concept design of joint part between propellant tank and feeding line for launch vehicle has been performed with the case study of oversea launch vehicles. we carried out, for the several configurations, numerical flow analyses to find the joint configuration which promises high flow uniformity at the outlet. There were a little difference in the numerical results, because the length of feeding lines are sufficiently long to stabilize the flow field.
정동호(Dongho Jung),오승협(Seunghyub Oh) (사)한국CDE학회 2013 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2013 No.1
There are a lot of method in pipes connecting but, most widely use weld. Not only general industry but space launch vehicle use to connecting pipes welding. To extend pipes many choices are available but welding is permanently join the pipes without leak. However pipe welding is not easy to install. During the welding if occur welding part stress concentration and a blow hole will be developed critical defect. Beside welding the pipes naturally grows welding beads It’s inside and outside. Accidentally welding back bead bigger than expect. It will be orifice not intentionally. On this paper deal with flow influence in pipe welding joint back bead and check the optimal point of back bead status a point of view flow.
지반보강용 수용성파우치(PVP)의 활용을 위한 기초적 연구
정동호(Dongho Jung),김기호(Kiho Kim),김주헌(Joo-Hyun Kim),한중근(Jung-Geun Han) 한국지반신소재학회 2017 한국지반신소재학회 논문집 Vol.16 No.2
도시의 노후화에 따른 상하수도관의 파손사례가 점차 증가하면서 지반함몰의 발생도 크게 증가하고 있고 도시과밀화에 따른 건설과 굴착공사들이 빈번해지고 있다. 특히, 도심에서는 lifeline이 지하화 되면서 지중에서 굴착과 되메움에 따라 원지반의 안정상태가 불안정한 상태를 갖게 된다. 이를 해결하기 위한 방법으로 양호한 토사다짐이나 그라우팅에 의한 지반보강법이 적용되고 있지만 지하매설물의 파손에 따른 시기를 예측키 어렵고, 지반내 구조물의 탐사방법도 한계가 있어 지반함몰과 같은 위험요소를 해결하기는 어려움이 있다. 따라서, 본 연구에서는 사전에 위험요소를 제거하기 위한 방법의 일환으로 개발된 빈배합상태의 혼화재를 포함한 수용성폴리머파우치에 대해 지반보강 적용성을 평가하였다. 대기속에 보관가능한 파우치의특성과 지하수위내부에서의 수용성 및 일정시간내 융해됨에 따른 보강강도의 발현을 확인할 수 있었다. 이를 통해 상하수도관 매설시 뒤채움재에 혼합매설하는 경우, 지반내 물의상태에 따라 지반의 연약화를 방지가능할 수 있게 되었다. There have been a number of water and sewer pipe breakdown reports followed by ground subsidence. Also, the excavating works for construction due to overcrowding of city have been common. Particularly, in urban areas ground becomes unstable because of the lowered lifeline sinkage followed excavation and backfilling. In order to solve the problem, some reinforcement works for ground by rod tamping or grouting have been applied. However, it is hard to predict when the buried utilities in underground will be damaged. Also, there is a limit for the underground exploration and investigation methods. Therefore, in this study, the estimated about the water soluble polymer pouch including poor mixed admixture which is designed to eliminate the dangerous factors. The reinforcement strength of this method was confirmed by verifying three points: meltiness in a certain period, water solubility in the ground water level, and characteristics of the pouch, which can be stored in daily conditions. It is also proved that this method allows to keep the ground from getting weakened in the installation of water and sewer pipe along with back filling materials.