• Nuclear Engineering and Technology
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• 제20권4호
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• pp.233-240
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• 1988

KMRR은 잉여반응도 및 출력분포조절을 위하여 Hafnium관을 사용한다. 현재 노심해석은 핵연료집합체 단위로 균질화된 5군 군정수를 이용하여 중성자 확산코드인 VENTURE을 이용한다. Hafnium관내에 핵연료가 들어있는 특수한 조정 집합체에 대해서도 이러한 균질화된 군정수를 사용한 중성자 확산계산이 적용될 수 있는가를 조사하였다. 비교계산은 중성자 수송코드인 TWOTRAN을 사용하여 잉여반응도 및 출력 준위에 대해 수행하였다. 계산결과 현재의 균질화된 군정수를 사용하는 중성자 확산계산이 큰 오차없이 적용할 수 있는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제63권5호
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• pp.585-595
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• 2017

This study aimed to presents a simple analytical approach to investigate the thermal buckling behavior of thick functionally graded sandwich by employing both the sinusoidal shear deformation theory and stress function. The material properties of the sandwich plate faces are continuously varied within the plate thickness according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are considered as uniform, linear and non-linear temperature rises across the thickness direction. Numerical examples are presented to prove the effect of power law index, loading type and functionally graded layers thickness on the thermal buckling response of thick functionally graded sandwich.

• 대한기계학회논문집B
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• 제32권5호
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• pp.359-366
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• 2008

A two-dimensional thermal model of proton exchange membrane fuel cell with large active area is developed to investigate the performance of fuel cell with large active area over various thermal management conditions. The core sub-models of the two-dimensional thermal model are one-dimensional agglomerate structure electrochemical reaction model, one-dimensional water transport model, and a two-dimensional heat transfer model. Prior to carrying out the simulation, this study is contributed to set up the operating temperature of the fuel cell with large active area which is a maximum temperature inside the fuel cell considering durability of membrane electrolyte. The simulation results show that the operating temperature of the fuel cell and temperature distribution inside the fuel cell can affect significantly the total net power at extreme conditions. Results also show that the parasitic losses of balance of plant component should be precisely controlled to produce the maximum system power with minimum parasitic loss of thermal management system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1015-1017
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• 2003

In a research and development team of high temperature superconducting (HTS) transformer for power distribution, prior to manufacture a single phase 1MVA 22.9 kV/6.6 kV HTS transformer, a 1MVA transformer for insulation test with windings made of copper tapes with the same size as BSCCO-2223 HTS tape was manufactured. The test transformer was composed of both the copper windings of double pancake type and the shell type core of laminated silicon steel plates. The characteristics tests of the test transformer were performed, such as no load test, load test and short test at 77k using liquid nitrogen. Insulation tests, lightning impulse test, power-frequency voltage test and external insulation test, were accomplished also.

• 한국산업융합학회 논문집
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• 제22권6호
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• pp.711-719
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• 2019

At present, wind power is the fastest growing technology in the world. The domestic market depends heavily on imports for wind tower lift. so it manage through the overseas maker. The lift manufacture, establishment and maintenance utility is increasing, localization development of one wind tower lift is necessary with domestic fundamental base technique. In this paper, we will study the components necessary for the development of onshore offshore wind tower elevators, which are currently dependent on total imports, in line with the high growth of the wind market and the enlargement of the wind power generators. First of all, endless winders and cabins, which are the core components of the offshore wind tower lift, were examined for the components that affect the structural safety. Structural analysis was performed on Sheave, which is responsible for most of the lift lifting loads, and Block Stop, a safety device that prevents the cabin from falling in an emergency. The structural suitability was evaluated by comparing with the safety factor. In addition, the on-board control panel combines the control panel of the elevator and the drive motor driving the endless winder for efficient control of the offshore wind tower lift. The addition of features improves ride comfort at departure.

• 유공압시스템학회논문집
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• 제3권4호
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• pp.14-20
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• 2006

Recently, the on-off solenoid valves have been focused on core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for bio-medical applications. A key characteristics for on-off solenoid valve, operated by compressed air, are high speed response and great repeatability. Indeed, it is also important to keep the pressure on the cross-sectional area of the poppet to be constant regardless of the fluctuation of the pressure exerted on the ports. In this study, we have designed and analysed the high-speed and high flow rate on-off solenoid valve using the analogy of equivalent magnetic circuit and Finite Element Method (FEM) respectively. In case of poppet, flow field characteristics was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D simulation using distribution curve of the force by working the front poppet.

• Structural Engineering and Mechanics
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• 제84권6호
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• pp.813-822
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• 2022

In this article, the buckling and free vibration of multi-directional FGM sandwich plates are investigated. The material properties of FGM sandwich plates are assumed to be varying continuously in the in the longitudinal, transverse and thickness directions. The material properties are evaluated based on Voigt's micro-mechanical model considering power law distribution method with arbitrary power index. Equations of motion for the buckling and vibration analysis of multi-directional FGM sandwich plate are obtained based on refined shear deformation theory. Analytical solution for simply supported multidirectional FGM sandwich plate is carried out using Navier's solution technique. The FGM sandwich plate considered in this work has a homogeneous ceramic core and two functionally graded face sheets. Influence of volume fraction index in the longitudinal, transverse and thickness direction, layer thickness, and geometrical parameter over natural frequency and critical buckling load of multi-directional FGM sandwich plate is investigated. The finding shows a multi-directional functionally graded structures perform better compared to uni-directional gradation. Hence, critical grading parameters have been identified which will guide researchers in selecting fabrication routes for improving the performance of such structures.

• 멤브레인
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• 제33권1호
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• pp.46-51
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• 2023

본 연구의 목적은 스마트시티 구축의 핵심인 수소연료전지의 활용형태를 분석하고 해결방안을 제시하는 것이다. 수소연료전지를 활용하는 발전소의 경우 간헐성 문제가 없다는 장점 때문에 향후 가장 유망한 사용 형태로 분석됐다. 다만 많은 장점에도 불구하고 폭발 우려와 특정 수소 생산방식의 경우 이산화탄소 발생 문제 등으로 지역주민들의 반발이 지속적으로 나타나고 있어 이를 해결하는 것이 스마트시티 구축의 주요 관건이 될 것으로 분석된다. 마지막으로 현재의 수소 생산방식을 분석하고 이에 따른 문제점을 파악하여 스마트시티의 완전한 구축을 위한 해결책을 제시하였다.

• 조명전기설비학회논문지
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• 제14권6호
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• pp.35-42
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• 2000

본 연구에서는 몰드형 전력변압기의 절연열화 상태를 진단하기 위해 에폭시 수지의 보이드방전에 의한 절연열 화의 상태를 트리의 길이에 따라 열화 초기, 중기 및 말기로 구분하고 이때 방출된 음향선호흘 분석하였다. 또한 보이드방전에 의한 음향선호를 측정할 때 몰드변압기의 철심에서 발생되는 자기적 음향 노이즈가 중첩됨으로 이를 구분하기 위해 용량 500[kVA]인 실용 몰드변압기를 배전 계통 22.9[kV]의 선로에 접촉하였을 때, 자화전류 및 부하전류에 의해 각 상에서 발생되는 음향 노이즈 신호의 주파수 스펙트럼올 분석하였다. 실행 결과, 에폭시수지의 보이드방전애 의해 발생된 음향방출신호의 주파수 스펙트럼은 열화상태에 따라 약 50-230[kHz] 범위에서 측정되었으나, 배잔계동에 접속된 실용 몰드변압기의 자화전류 및 부하전류에 의해 발생된 자기회로의 음향 노이즈에 대한 주파수 스펙드럼은 약 4O-120[kHz] 대역인 것으로 나타났다.

• 지구물리와물리탐사
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• 제7권1호
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• pp.62-69
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• 2004

The objective of this study is to estimate the distribution of a zone disturbed by excavation (EDZ) around tunnels that have been excavated at about 500 m depth in pre-Tertiary hard sedimentary rock. One of the most important tasks is to evaluate changes in the dynamic stability and permeability of the rock around the tunnels, by investigating the properties of the rock after the excavation. We performed resistivity and acoustic tomography using two boreholes, 5 m in length, drilled horizontally from the wall of a tunnel in pre-Tertiary hard conglomerate. By these methods, we detected a low-resistivity and low-velocity zone 1 m in thickness around the wall of the tunnel. The resulting profiles were verified by permeability and evaporation tests performed at the same boreholes. This anomalous zone matched a high-permeability zone caused by open fractures. Next, we performed resistivity monitoring along annular survey lines in a tunnel excavated in pre-Tertiary hard shale by a tunnel-boring machine (TBM). We detected anomalous zones in 2D resistivity profiles surrounding the tunnel. A low-resistivity zone 1 m in thickness was detected around the tunnel when one year had passed after the excavation. However, two years later, the resistivity around the tunnel had increased in a portion, about 30 cm in thickness, of this zone. To investigate this change, we studied the relationship between groundwater flow from the surroundings and evaporation from the wall around the tunnel. These features were verified by the relationship between the resistivity and porosity of rocks obtained by laboratory tests on core samples. Furthermore, the profiles matched well with highly permeable zones detected by permeability and evaporation tests at a horizontal borehole drilled near the survey line. We conclude that the anomalous zones in these profiles indicate the EDZ around the tunnel.