• Journal of the Society of Naval Architects of Korea
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• v.58 no.5
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• pp.314-321
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• 2021

In the existing whole ship analysis, topside was modeled as mass element. However recently, the topside is modeled as beam element due to the owner's requirement to improve the maturity of the whole ship FE model. To follow the owner'srequirement, detailed information for topside drawing and modeling, which may delay analysis schedule, is needed. However, it is hard to respond effectively to this matter due to the lack of study on the topside from the hull perspective. Therefore in this study, the effect of the topside on the hull is investigated when the topside is modeled as a mass element or beam element respectively. In addition, the interface modeling method is analyzed to verify modeling method used in the existing whole ship analysis. The results indicate that the interface and topside modeling method used in existing whole ship analysis are appropriate. This conclusion will be the technical basis for responding to owner's requirement about the topside modeling method.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.221-223
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• 2020

반도체 기반 고전압 펄스 발생장치에 적용 가능한 고전압 스위치는 주로 수 kV 정격의 반도체 스위치를 직렬로 스태킹하여 구성되며, 이때 각 스위치 소자에는 절연과 동기화된 각각의 게이트 신호가 인가되어야 한다. 본 논문에서는 짧은 펄스 폭의 온, 오프 게이트 펄스와, 단일 턴의 고전압 전선을 일차측으로 갖는 게이트 변압기를 통해 직렬로 구성된 반도체 스위치 스택 기반의 펄스 모듈레이터에 적용 가능한 간단한 구조의 게이트 구동회로가 설계되었다. 각 스위치에 게이트 신호를 전달하기 위해 온, 오프 게이트 펄스를 사용함으로써 게이트 변압기의 포화를 방지할 수 있으며, 이때 각 스위치의 게이트 턴-온, 오프 전압은 변압기 이차측의 제너 다이오드와 스토리지 커패시터를 통해 유지된다. Pspice 시뮬레이션을 통해 12개의 IGBT를 직렬로 구성하여 설계된 구조의 게이트 회로를 적용, 최대 10kV 펄스 출력 조건에서 안정적인 동작을 확인하고 설계를 검증하였으며 1200V 급 IGBT를 사용하여 실제 스위치 스택과 게이트 구동회로 모듈을 1리터 이내의 부피로 고밀도화하여 제작하였다.

• Fire Science and Engineering
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• v.25 no.6
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• pp.83-88
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• 2011

This study presented the structure and characteristics of vinyl cords used for wiring electric equipment and appliances and analyzed the photographs of damaged flat-type vinyl cords (VFF, $1.25mm^2$) and the metallic cross-sectional structure of melted conductors. Normal VFFs were made by twisting several strands together and the surface of the conductor was red brown. In addition, from the analysis of the metallic structure of the conductor, it was found that its grains had been elongated. The surface of a VFF damaged by normal flame showed no sheen with carbonized insulation material fused on the conductor surface. In addition, from the analysis of the cross-sectional structure of the melted area, it was found that voids of a certain shape were formed on it but that the cord's own elongation structure could not be checked. The cross-sectional analysis of the melted conductor damaged by the external flame applied to a VFF to which electric current was being applied showed no elongation structure for each cord, and revealed that irregular voids and a columnar structure had grown. The surface of the VFF damaged by overcurrent was uniformly carbonized and the cross-sectional structure analysis of the melted conductor revealed that the dendritic structure had grown. The analysis of the characteristics of the VFF melted by short-circuit showed that even though some part of the surface was contaminated, it showed little sheen and that the area rebounded by melting was round in shape. In addition, the cross-sectional structure analysis using a metallurgical microscope showed the boundary surface and columnar structure and revealed an amorphous structure like normal copper at areas other than the melted conductor.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.173-176
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• 2008

Use of concrete has undoubtedly become widespread in construction. Sensors are used to add functional characteristics to concrete. Self-diagnosing, smart concrete is also being developed. Development of these functional materials and structures will play an important role in protecting buildings and structures against external factors brought about by unusual weather among others. In this study, the innovative measurement system is presented where material damages and internal stress can simply be detected against the compressive and bending force of the structure using light-emitting diode and the resistance property of electric fuse.

• Computational Structural Engineering
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• v.3 no.3
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• pp.133-140
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• 1990

Analysis of cable structures is complex because their force - displacement relationships are highly nonlinear and also because large deformations introduce geometric nonlinearity. Therefore, we must take account their geometric nonlinearity in the analysis and find the equilibrated shape of cable structures. In this paper, to slove these problems, numerical procedures involving geometrical nonlinearity are introduced. They are applicable to general cable net, flexible transmission lines and suspended cable roof. These procedures are divided into two parts; one is to obtain the equilibrated shapes and stresses of the cable structures with uniform load by flexibility iteration method, the other is to analyse the equilibrated structures subjected to nodal external forces by nonlinear finite element method.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.237-247
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• 1991

To characterize the community structure and spatial distribution of phytoplankton, observations on seawater temperature, salinity, nutrients, primary productivity and abundance and species composition of phytoplankton were made in the polar front region and its neighborhood off the east coast of Korea in summer 1990. Among the 96 taxa identified, Rhizosolenia setigera and Thalassionema nitzschioides were the most dominant species. The assemblage at the surface and 50 m depth was quite different in the northern inshore part of the study area but similar in the southern and offshore part. Principal component analysis by the species abundance showed that the phytoplankton consisted of the communities representing the surface of the northern inshore part with the neritic-warm dinoflagellates, the Northern Korean Cold Water with the cold water diatoms and the southern and offshore part, which seems to represent the Eastern Korean Warm Water, with the warm water diatoms. At the frontal region, diatoms were mixed with warm and cold water species. Primary productivity and phytoplankton standing crops were higher at the front than the neighboring waters. Nutrients were markedly high at the Northern Korean Cold Water. Horizontal advection of the Northern Korean Cold Water accompanied by nutrient supply seems to contribute to the high phytoplankton biomass at the front.

• Bulletin of the Society of Naval Architects of Korea
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• v.54 no.4
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• pp.39-46
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• 2017

Jack-up drilling rigs are widely used in offshore oil and gas exploration industry. It is originally designed for use in the shallow waters less than 60m of water depth; there is growing demand for their use in deeper water depth over 150m and harsher environmental conditions. In this study, global in-place analysis of jack-up rig leg for North-sea oil well is performed through numerical analysis. Firstly, environmental conditions and seabed characteristics at the North-sea are collected and investigated measurements from survey report. Based on these data, design specifications are established and the overall basic design is performed. Dynamic characteristics of the jack-up rig for North-sea are considered in the global in-place analysis both leg and hull and the basic stability against overturning moment is also analyzed. The structural integrity of the jack-up rig leg/hull is verified through the code checks and the adequate safety margin is observed. The uncertainty in jack-up behaviour is greatly influenced by the uncertainties in the soil characteristics that determine the resistance of the foundation to the forces imposed by the jack-up structure. Among the risks above mentioned, the punch-through during pre-loading is the most frequently encountered foundation problem for jack-up rigs. The objective of this paper is to clarify the detailed structure and installation engineering matters for prove the structural safety of jack-up rigs during operation. With this intention the following items are addressed; - Characteristics of structural behavior considering soil effect against environmental loads - Modes of failure and related pre-loading procedure and parameters - Typical results of structural engineering and verification by actual measurement.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.71-73
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• 2006

본 논문은 단상 1MVA 22.9kV/220V 케이블 변압기의 설계, 제작 및 시험 결과를 서술한다. 케이블 변압기는 유입변압기의 폭발위험성과 환경오염 가능성이 없으므로, 인구밀집지역, 지하장소등 설치장소의 제한이 없는 장점이 있다. 제작된 케이블 변압기는 22.9kV급의 XLPE 케이블 전선을 사용하여 1차 권선을 제작하였으며, 2차측 권선은 내 단락시 특성이 우수한 몰드 권선 형태로 제작하였다. 사용된 XLPE 케이블은 도체-내부반도전층-XLPE-외부반도전층으로 구성되어 있으며, 외부반도전층은 접지된 구조이다. 철심은 단상 3각 구조로써 방향성 규소강판을 사용하였으며, 냉각방식은 공기 자연냉각방식이다. 제작된 변압기의 신뢰성을 확보하기 위하여, 특성시험과 절연시험을 실시하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.131-132
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• 2015

현대 사회의 기술 발달에 따라서 회로의 집적도 대비 이용하는 주파수가 매우 높아지고 있다. 즉, 회로의 이용 주파수가 높아짐에 따라서 파장이 신호를 전달하는 전선만큼 짧아져 기존의 회로이론을 기반으로 하는 집중 정수 회로적 관점으로 해석할 수 없다. 따라서 전송선로 이론에 따라 해석하여야 하지만, 최근 전자기기들은 높은 집적도나 여러 모듈(Module)을 종합해서 만들기 때문에 전기적 특성이 일정한 전송선로의 이론을 적용하기가 힘들며, 따라서 이는 불연속을 고려한 전송선로의 분석이 이루어져야 함을 시사한다. 이에 본 논문에서는 전송선로에서 불연속 구간이 존재할 경우 기존의 전송선로 이론을 적용한 전기파라미터 변환에 미치는 영향을 알아보기 위해서 불연속 구간이 존재하는 마이크로 스트립 구조를 설계해 VNA(Vector Network Analyzer)를 이용해서 산란계수(S-Parameter)를 측정 및 분석하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.211-211
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• 2008

태양열, 바람, 지열, 진동 등의 우리주변에서 쉽게 얻을 수 있는 에너지를 모아서 필요로 하는 전자기기의 에너지원으로 사용하는 개념의 에너지하비스팅에 대한 연구가 활발히 진행되고 있다. 기계적인 변경으로 전압이 발생하는 압전체는 오래전 알려져 있었지만 발생전압이 낮아 에너지발전용으로 적용이 힘들었다. 하지만 전자기기의 소형화와 함께 필요로 하는 전력도 수 ${\mu}W$로 낮아짐으로 압전체를 이용한 에너지하비스팅이 주목 받고 있다. 전선으로 연결하여 전원을 공급하기 힘든 위치에 있는 전자기기는 주기적으로 배터리를 교환해 주어야한다. 이는 시간적, 금전적, 인적자원의 낭비이며 반영구적으로 전원을 공급할 장치개발이 필요하다. 구조물은 수~ 수십 Hz로 진동을 하며 이 진동으로 압전체에 변형을 주어 전압을 발생시킨다. 변형이 클 때 발생전압도 크게 되므로 압전체를 칸틸레버형태로 제작했다. 더 큰 전압발생을 위해 메탈을 사이에 두고 양면에 압전체를 둔 바이몰프 형태로 캔틸레버를 제작했다. 이때 진동의 충격을 완화시켜 압전체에 인가되도록 하고 구조물의 고유진동수모다 큰 진동수로 압전체가 진동하도록 하기위해 스프링을 사용하여 제작하였다. 이 스프링 지지구조 및 가진 조건에 따른 발전특성을 알아보았다.