• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.439-448
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• 2016

Extended end-plate connections(EEPC) are a type of connection applied in Pre-Engineered Building structures comprising beam-column connections of steel structures or tapered members. Extended end-plate connections(EEPC) show different behavioral characteristics owing to the influence of plate thickness, gauge distance of high strength bolt, diameter of high strength bolt frame, and the number of high strength bolts. In the USA and Europe, extended end-plate connections(EEPC) are applied in beam-column connections of steel structures in various forms; however, these are not widely applied in structures in Korea.This can be attributed to the fact that the proposal of design strength types for extended end-plate connections(EEPC), proposal of connection specifications, evaluation of seismic performance, and are not being performed appropriately. Therefore, the purpose of this study is to provide basic data for the domestic application of Unstiffened extended endplate connections. To realize this, nonlinear finite element analysis was conducted on a 12-mm thick Unstiffened extended endplate connections.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.19-24
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• 2012

Barium zirconate exhibits good thermo-chemical stability and proton conduction at high temperatures, but shows poor electron conductivity. Therefore, for high efficiency of hydrogen separation, a very thin and dense Pd-Barium zirconate membrane has to be coated on a porous substrate. A thin and dense Pd-Barium zirconate membrane was successfully synthesized on a porous substrate by means of dual sputtering method. The structural and chemical features of the $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ membranes sputtered at $300^{\circ}C$ and $400^{\circ}C$ were investigated by X-ray diffractometry, and it was found that a well-crystallized membrane, Pm-3m space group of $BaZrO_3$, was synthesized. The surface and cross-sectional morphologies of membrane were assessed by SEM (scanning electron microscopy) and TEM(transmission electron microscopy) of the surface and of cross sections. The cross sectional observation of Pd-$BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ membrane by dual sputtering shows that the coating is quite dense with columnar structure.

• Journal of the Korean Electrochemical Society
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• v.5 no.3
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• pp.153-158
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• 2002

The effects of leveler on the copper trench filling were investigated during damascene plating process. To investigate the trench filling effect with the addition of a leveler, a cross-section images of the electroplated trenches with the width of$0.37{\mu}m,\;and\;0.18{\mu}m$ were observed by field emission scanning electron microscope (FE-SEM). Polyethylene glycol(PEG), 3-mercapto-1-propanesulfonic acid and Janus Green B were used as a carrier, an accelerator and a leveler. $0.37{\mu}m$ trenches were superfilled without voids, but there was voids formation in $0.18{\mu}m$ trenches when the leveler was not added into the electrolyte. On the other hand $0.18{\mu}m$ trenches were superfilled without voids with the addition of the leveler due to the reduction growth rate of copper at protrusions and edges, which yield smooth final deposit surface. The leverer effect becomes more significant as the width of trenches becomes smaller when trenches are filed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.310-320
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• 2009

In this paper, we estimate area-averaged solution of peening residual stress using a 3-D multi-impact symmetry-cell FE model. The symmetry-cell model includes factors reflecting peening phenomena and plastic shot. Area-averaged solution is much closer to XRD experimental solution than 4-node-averaged solution in plastic shot FE model. We then obtain FE Almen saturation curve corresponding to experimental Almen curve based on area-averaged solution. Using the curve, we obtain FE area-averaged solution in major peening materials, and compare the FE solution with experimental solution. In peening materials, surface, maximum compressive residual stress and deformation depth reach experimental solutions. Thus, FE Almen curve is useful for estimation of residual stress solution and could improve the efficiency of peening process. Consequently, it is confirmed that concept of area-averaged solution is the realistic analytical method for evaluation of peening residual stress.

• Journal of Radiation Protection and Research
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• v.9 no.2
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• pp.90-96
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• 1984

Estimated dose rates in spent fuel pool storage with the extended fuel cycle core management were reviewed and compared with design limit after calculation with the aid of DLC-23/CASK(22 n, 18 g) nuclear data and ANISN code. Radioactivity and gamma spectrum within spent fuel assemblies were calculated with ORIGEN code by extended fuel cycle model. In the calculation of dose rate, the fuel pool geometry was assumed to be infinite slab. Also, composition materials and radiation source within assemblies which are being stored in pool storage were assumed to be uniformly distributed throughout all the assemblies. As a result of culculation of dose rate from stored assemblies and waterborne radionuclides in pool water, the calculated dose rates appear to be lower than design basis limit under normal condition as well as abnormal condition.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.529-541
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• 2020

Although TBM's cutterhead requires design review for fatigue failure due to wear-induced section loss as well as heavy load during excavation, it is difficult to find a case of fatigue analysis for TBM cutterhead at present. In this study, a stress-life design review was conducted on cutter heads with a diameter of 8.2 m using S-N curves as a safety life design concept. Also, we introduced the fatigue design method of construction equipment and the method of assessing fatigue damage and explained the results of the fatigue analysis on the TBM cutter head with a diameter of 8.2 m. The S-N curve has been shown to play a key role in fatigue design and can also be used to assess how much fatigue damage a structure is suffering from at this point in time. In the future, it is necessary to find out when fatigue problems occur during using the equipment and when it is good to conduct safety inspections of the equipment.

• Clinical and Experimental Pediatrics
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• v.52 no.3
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• pp.339-345
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• 2009

Purpose : This study aimed to determine the variation in parameters according to cardiac cycle length (CL; time interval between the QRS peaks on ECG) in children by using the conventional pulsed Doppler and tissue Doppler imaging echocardiography. Methods : Eighteen children with an anatomically normal heart were enrolled for the study. All children were examined by conventional and pulsed Doppler echocardiography at Gangneung Asan hospital between July 2006 and June 2007. We measured the CLs, mitral inflow velocities (E,A) and tissue Doppler imaging (TDI) parameters (s', e', a') from apical 4-chamber view. The TDI parameters were measured at the lateral (Lat) and septal (Sep) part of the mitral valve. All parameters were measured at 6 to 18 consecutive beats from each child. We then evaluated the linear correlation between CL and each parameter. Results : The mean age was $3.6{\pm}0.5$ years (M:F=8:10). There were significantly negative linear correlations between CL and A, Lat s', Lat a', Sep s', Sep e', Sep a' (P<0.01). There were significantly positive linear correlations between CL and E/A, Lat e'/a', Sep e'/a' (P<0.01). However, the E and Lat e' were not correlated with CL (P=0.229 and 0.221, respectively). Conclusion : This study showed that the values of the left ventricular functional parameters were changed according to CL. From our results, it is imperative to carefully examine beat-to-beat variations in children.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.133-139
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• 2016

In order to obtain a reasonable value for the thermal load to use in designs, a bridge specimen of a full-size steel box girder (bridge) was manufactured. The temperature data were measured at 21 points in the bridge specimen and 19 points in the steel box bridge. The steel box bridge specimen was installed in a similar direction to a nearby real one. The maximum effective temperatures in the bridge specimen and bridge were calculated for air temperatures in the range of $24^{\circ}C{\sim}38^{\circ}C$. The maximum effective temperature of the bridge specimen and bridge showed correlations of approximately 93.2% and 87.4%, respectively, compared with the Euro code. The maximum effective temperature calculated in this study was very close to the Euro code and the maximum temperature of the Highway Bridge Design Criteria. When the effective temperature obtained in the study is combined with the highest temperature calculated from the Contour map for each region, the design criteria for the thermal load in domestic bridge design, taking into consideration the characteristics of each region, can be established.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.543-555
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• 1997

Generally, in a steel-concrete composite gilder, the shear connector which was constructed between concrete deck and steel girder should have enough stiffness to behave as one body, because the conformity between plate and concrete deck is influences by the stiffness and spacing of the shear connectors. If the stiffness of shear connectors are insufficient, slip would happen at the contact surface. Partial interaction is the case that takes account of slips. In this paper, an easy method is presented to evaluate the stiffness or spacing of the shear connector according to the degree of imperfection without difficult calculations for a composite gilder with partial interaction. Also, the horizontal shearing force applied to the shear connector and the longitudinal axial force, which is occurs at contact surface between concrete deck and steel girder, have been presented in a simple influence line that is various to the parameters of sectional properties, degree of imperfection and applied load points. Furthermore, through the case study, it determined the relationships between the degree of imperfection and the follows 1) spring constants 2) axial force and horizontal shearing force 3) stress and neutral axis by using the partial differential equation based on Newmark's Partial Interaction Theory.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.244-245
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• 2010

최근 광전자 분야에서는 미래 에너지 자원에 대한 관심과 함께 GaN 기반 발광다이오드 및 태양전지 연구가 활발히 진행되고 있다. GaN는 높은 전자 이동도와 높은 포화 속도 등의 광전자 소자에 유리한 특성을 가지고 있으나, 고 인듐 함유량과 막질의 우수한 특성을 동시에 구현하는 것은 매우 어렵다. 이를 극복하기 위한 방법으로써 선택 영역 박막 성장법(Selective Area Growth)은 마스크 패터닝을 통해 제한된 영역에서만 박막을 성장하는 방법으로써 GaN의 막질을 향상 시킬 수 있는 방법으로 주목받고 있다. 본 논문에서는 대면적 기판에서 GaN의 막질 향상뿐만 아니라 고인듐 InGaN 박막 성장을 위하여 서브마이크로미터 주기와 크기를 갖는 홀 패턴을 포토리소그라피 공정 최적화를 통해 구현할 수 있는 방법에 대해 논의한다. 그림. 1은 사파이어 기판 위에 선택 영역 박막 성장법을 이용하여 성장한 n-GaN/활성층/p-GaN의 구조를 나타낸 그림이다. 이를 통하여 서브마이크로미터 스케일의 반극성 InGaN면 위에 높은 인듐 함유량을 가지면서도 우수한 특성을 갖는 박막을 얻을 수 있다. 본 실험을 위하여 사파이어 기판 위에 SiO2를 증착한 후 포토레지스트(AZ5206)을 도포하고 포토리소그라피 공정을 진행하여 2um 크기 및 간격을 갖는 패턴을 형성했다. 그림. 2는 AZ5206에 UV를 조사(5초)하고 현상(23초)한 패턴을 윗면(그림. 2(a))과 $45^{\circ}$ 기울인 면(그림. 2(b)) 에서 본 SEM(Scanning Electron Microscope) 사진이다. 이를 통해 약 2.2um의 홀 패턴이 선명하게 형성 됨을 볼 수 있다. 그 후 수백나노 직경의 홀을 만들기 위해서 리플로우 공정을 수행한다. 그림. 3은 리플로우 온도에 따른 패턴의 홀 모양을 AFM(Atomic Force Microscope)을 이용하여 측정한 표면의 사진이다. 이를 통해 2차원 평면에서 리플로우 온도 및 시간에 따른 변화를 볼 수 있다. 그림.3의 (a)는 리플로우 공정을 진행하기 전 패턴이고, (b)는 $150^{\circ}C$에서 2분, (c)는 $160^{\circ}C$에서 2분 (d)는 $170^{\circ}C$에서 2분 동안 리플로우 공정을 진행한 패턴이다. $150^{\circ}C$와 $160^{\circ}C$에서는 직경에 큰 변화가 없었고, $160^{\circ}C$에서는 시료별 현상 시간 오차에 따라 홀의 크기가 커지는 경향이 나타났다. 그러나 $170^{\circ}C$에서 2분간 리플로우 한 시료 (그림. 3(d))의 경우는 홀의 직경이 ~970nm 정도로 줄어든 것을 볼 수 있다. 홀의 크기를 보다 명확히 표현하기 위해 그림.3에 대응시켜 단면을 스캔한 그래프가 그림.4에 나타나 있다. 그림.4의 (a) 및 (b)의 경우 포토레지스트의 높이 및 간격이 일정하므로, 리플로우에 의한 영향은 거의 없었다. 그림. 4(c)의 경우 포토레지스트의 높이가 그림.4(a)에 비해 ~25nm 정도 낮은 것으로 볼 때, 과도 현상 및 약간의 리플로우가 나타났을 가능성이 크다. 그림. 4(d)에서는 ~970nm의 홀 크기가 나타나서 본 연구에서 목표로 하는 나노 홀 크기에 가장 가까워짐을 확인할 수 있었다. 따라서, $170^{\circ}C$ 이상의 온도와 2분 이상의 리플로우 시간 조건에서 선택 영역 성장을 위한 나노 홀 마스크의 크기를 제어할 수 있음을 확인하였다.