• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.191-196
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• 1997

As a part of International Criticality Safety Benchmark Evaluation Project (ICSBEP), SAXTON critical experiments were reevaluated. The effects on $K_{eff}$ of the uncertainties in experiment parameters, fuel rod characterization, soluble boron, critical water level, core structure, $^{241}$ Am and $^{241}$ Pu isotope number densities, random pitch error, duplicated experiment, axial fuel position, model simplification, etc., were evaluated and added in benchmark-model $k_{eff}$. In addition to detailed model, the simplified model for Saxton critical experiments was constructed by omitting the top, middle, and bottom grids and ignoring the fuel above water.r.r.

• 한국기계가공학회지
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• 제9권1호
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• pp.93-98
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• 2010

The metal fastening method is the new technology to repair cracks in the casting material using specially designed reverse screws. In this study, we conduct the finite element analysis to analyze the pulling force characteristic of a reverse screw, the core component of the metal fastening method, with respect to the change of the applying torque, frictional coefficient and front screw angle. The simplified analysis model with single screw pitch is proposed for convergency of the non-linear contact analysis. As a results, the pulling force of a reverse screw increase in proportion to the applying torque but exponentially decrease according to frictional coefficient. And also we can find the optimum front screw angle with the largest pulling force is $20^{\circ}$.

• Design & Manufacturing
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• 제11권2호
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• pp.9-14
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• 2017

The design and manufacturing tehcnology of IC sockets beyond 0.3mm pitch were presented. We compared the developed IC socket with the conventional one especially on the core metal-insulation part. Advanced machining techniques were employed to provide high precision. Our wire electrodischarge machining and high speed machining centers were able to maintain the micro-scale precision. We performed an injection molding analysis using a commercial analysis tool to predict the performance of the developed IC socket. We found that the solidification of the plastic resin and the high level of the clamping force are responsible for the defects such as incomplete filling and short shot. From these results, we modified the IC socket and successfully remove the defects. We were also able to find out that the new design socket needs less maintenance cost.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1267-1269
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• 2005

This paper presents the design for improving performance of the high-precision Magnetic levitation system. Motor performance on various design schemes such as thickness and magnetizing patterns of the permanent magnets, pole pitch, length of air gap, turn number of windings, and thickness of the aluminum-core has been investigated in detail by using FEM(Finite Element Method) Simulation-based DOE(Design of Experiments) method is also applied in order to reduce the large number of analysis according to each design variable and consider the effect among variables. The design in all aspects is proposed by an optimization algorithm using regression equation derived from the simulation-based DOE.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.32-39
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• 2023

One of the main problems faced in developing India's first HTS power cable was that of shrinkage in length of the double-walled vacuum-insulated cryostat. The shrinkage was due to the evacuation of the annular vacuum space which results in a shorter working cable length. This work reports experimentally observed contraction during evacuation and analyses corrugated pipes/bellows which house the cable core of HTS cables. The effect of corrugation geometry including length, corrugation pitch and depth, diameters of corrugated pipes and thicknesses of pipes is studied numerically to realize the degree of shrinkage due to vacuum as well as chill down. Finally, necessary length compensation and associated cost is determined to tackle the shrinkage issue.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2474-2479
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• 2024

In-Vessel Retention (IVR) is a key technology to retain the molten core in the reactor vessel during severe accidents of Pressurized-water reactors (PWRs). In order to gain the safety margin of IVR, it is crucial to enhance the critical heat flux (CHF) of the reactor vessel, which is submerged in a water pool. To enhance the CHF, we have designed and additive-manufactured porous grid plates with a 3-D printer for design flexibility. We measured the CHF for the porous grid plate on the boiling heat transfer surface and found that the CHF was enhanced by 50 % more than that of the bare surface. The CHF enhanced more with a narrower grid pitch and a lower grid height. The visual observation study revealed that the vapor film was formed at the bottom of the grid plate.

• 한국항공우주학회지
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• 제44권5호
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• pp.439-446
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• 2016

이 논문에서는 무베어링 로터의 동특성을 비회전 강성 및 진동수 측정 시험과 회전 훨타워 시험을 통해 살펴보았다. 무베어링 로터의 주요 구성품인 블레이드, 유연보, 토크튜브에 대해 강성 및 고유진동수를 측정하여 해석을 위한 물성치를 확보하였고, 훨타워 시험 전에 댐퍼와 스너버를 장착한 무베어링 로터를 조립하여 지상에서 하중이 부가되는 조건하에 기능시험을 수행하여 로터 구성품간의 간섭 여부, 기구학적 거동 등을 확인하였다. 4개의 블레이드를 가지고 회전반경이 5.82m인 무베어링 로터의 회전 동특성시험을 회전면 높이가 9.65m인 훨타워에서 수행하였다. 정지비행성능을 확인하기 위해 추력과 사용동력을 측정하였으며, 회전시 블레이드의 고유진동수 및 감쇠를 측정하기 위해 유압 가진기를 통하여 사이클릭 가진을 하였다.

• 대한조선학회논문집
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• 제53권1호
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• pp.37-44
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• 2016

Recently researchers are conducting a lot of research related to EEDI in order to satisfy IMO resolution MEPC. Especially they are interested in design of energy saving device. This paper is to design the asymmetric pre-swirl stator for 160K LNG carrier in order to reduce energy. Two types of the asymmetric pre-swirl stator are taken into account; constant and variable pitch angle stators. “constant” and “variable” mean state that the pitch of stators change by radius. The dimensions of the stators are initially determined using potential-flow code. The propulsion performances of the stators are predicted using viscous-flow code. The model test is carried out in towing tank in PNU. Prediction of ship performance generally follow ITTC recommended. Ship wake prediction was done by two method, ITTC 1978 and ITTC 1999. Therefore propulsion performances were compared ITTC 1978 with ITTC 1999 methods. Comparison components are delivered power and thrust deduction coefficient of the model. Final pre-swirl stator is selected by comparing experiment and CFD.

• Smart Structures and Systems
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• 제17권4호
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• pp.593-610
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• 2016

In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

• 대한전자공학회논문지SD
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• 제47권11호
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• pp.1-5
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• 2010

본 논문에서는 외팔보 배열 구조를 가지는 MEMS 테스트 소켓을 SOI 웨이퍼를 이용하여 개발하였다. 외팔보는 연결부분의 기계적 취약점을 보완하기 위해 모서리가 둥근 형태를 가지고 있다. 측정에 사용 된 BGA IC 패키지는 볼 수 121개, 피치가 $650{\mu}m$, 볼 직경 $300{\mu}m$, 높이 $200{\mu}m$ 을 가지고 있다. 제작된 외팔보는 길이 $350{\mu}m$, 최대 폭 $200{\mu}m$, 최소 폭 $100{\mu}m$, 두께가 $10{\mu}m$인 곡선 형태의 외팔보이다. MEMS 테스트 소켓은 lift-off 기술과 Deep RIE 기술 등의 미세전기기계시스템(MEMS) 기술로 제작되었다. MEMS 테스트 소켓은 간단한 구조와 낮은 제작비, 미세 피치, 높은 핀 수와 빠른 프로토타입을 제작할 수 있다는 장점이 있다. MEMS 테스트의 특성을 평가하기 위해 deflection에 따른 접촉힘과 금속과 팁 사이의 저항과 접촉저항을 측정하였다. 제작된 외팔보는 $90{\mu}m$ deflection에 1.3 gf의 접촉힘을 나타내었다. 신호경로저항은 $17{\Omega}$ 이하였고 접촉저항은 평균 $0.73{\Omega}$ 정도였다. 제작된 테스트 소켓은 향 후 BGA IC 패키지 테스트에 적용 가능 할 것이다.