• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.10 s.103
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• pp.1186-1194
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• 2005

In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.609-617
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• 2002

A three-dimensional(3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular rings with isosceles trapezoidal and triangular cross-sections. Displacement components u/sub s/, u/sub z/, and u/sub θin the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the ψ and z directions. Potential(strain) and kinetic energies of the circular ring are formulated, and upper bound values of the frequencies we obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for the circular rings with isosceles trapezoidal and equilateral triangular cross-sections having completely free boundaries. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the rings. The method is applicable to thin rings, as well as thick and very thick ones.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.297-301
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• 2002

본 논문에서는 광대역 원형 링슬롯 안테나의 광대역 특성이 일어나는 메커니즘 연구를 통해 새로운 광대역 안테나 설계 및 분석에 도움을 줄 수 있도록 하였다 먼저 기존의 광대역 안테나 및 공진회로 개념을 이용하여 새로운 광대역 안테나의 이론적인 분석을 하도록 하였으며, 기존의 광대역 안테나를 설계하는 방법(자기유사구조, 자기상보구조, 길이보다 각을 강조한 구조, 두꺼운 도체를 사용하는 구조 등)외에 최근들어 많이 연구되고 있는 안테나의 Q값을 줄이는 방법에 대해 분석 및 정리하고 본 원형 링슬롯 안테나의 복사기와 급전선사이에서 광대역이 일어나는 메커니즘에 대해서 연구하였다.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.94-99
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• 2021

It was found that mixing patterns suddenly changed at an impeller rotation speed in a dished bottom vessel with dual Rushton turbines. Two isolated mixing regions like doughnuts rings generated at a low rotational speed and three isolated mixing regions generated at a higher speed. This phenomenon was observed at the mixing condition in transition area, where the power number with baffle was the same as that without baffle. We found a phenomenon in which the flow state in a dish-bottom agitation tank equipped with a two-stage Rushton turbine blade changes at a certain rotational speed. In the laminar flow region, the isolated stable donut rings were formed even when the rotational speed was changed, and no specific variation in the mixing pattern was observed. In the transition region, the two isolated thick unmixed donut rings do not change even if the rotation speed is changed in the flat bottom vessel, whereas in the dished bottom vessel, when the rotation speed is 450 rpm, the two isolated thick unmixed donut rings are changed to three isolated thin donut rings and then improved mixing. In the dished bottom vessel, in the range of Re=138~178, the isolated ring-shaped unmixed region appeared in three places and the size was also large. But in the flat bottom vessel, the isolated thick ring-shaped unmixed region appeared in two places in Re=116~176 and the size was also small. It appeared in two places, and the size was also small. The condition in which this phenomenon is observed is a transition region, and it was found that when the baffle plate is attached, the power number starts to increase compared to when the baffle plate is not present. In addition, when the mixing Reynolds number exceeded 300 and a slight turbulence was mixed in the flow state, the disconnection of these flow pattern was resolved and the mixture was completely mixed.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.255-260
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• 2005

A Gravity characteristic of Svalbard archipelago in Arctic was studied by using ArcGP data. There are situated the Dasan science station. After bouguer correction, an edge effect of free-air anomaly, which is similar to topography, are not shown at passive continent margin, and after terrain correction with GTOPO30 data, gravity anomaly increases from continent to marine. that is deep connected with rise of Moho discontinuity. The correlation of topography and free-air anomaly shows that the isostasy of continent attains a little less than marine. After filtering, the residual anomaly are shown high and low anomalies related to fracture zone in continent and base depression or thick sedimentary layer in continental slope, marine.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.295-295
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• 2011

전하 저장 층으로 사용된 산화막-실리콘-산화막의 경우 낮은 전압에서 큰 메모리 윈도우를 가짐으로써 비휘발성 메모리에의 가능성을 확인시켜줬다. 하지만, 나쁜 전하지속시간 특성으로 인한 문제점이 있다. 따라서 이를 개선시키기 위하여 터널링 층의 두께를 증가시키고 산화막-실리콘-산화막-실리콘-산화막의 다층 구조를 이용하여 메모리 윈도우 특성의 향상 뿐만 아니라, 전하지속시간 역시 향상 시켰다. 이를 통해 산화막-실리콘-산화막-실리콘-산화막 구조의 비휘발성 메모리를 SOP 디스플레이에 적용할 수 있을 것으로 기대한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.142-142
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• 2010

본 논문은 단결정 및 다결정 실리콘 기판 상에 아산화질소 플라즈마 처리를 통하여 형성한 초박형 실리콘 옥시나이트라이드 박막의 특성과 이의 어플리케이션에 관한 것이다. 초박형 절연막은 현재 다양한 전자소자의 제작과 특성 향상을 위하여 활용되고 있으나 일반적인 화학 기상 증착 방법으로는 균일도를 확보하기 어려운 문제점을 가지고 있다. 디스플레이의 구동소자로 활용되는 박막 트랜지스터의 특성 향상과 비휘발성 메모리 소자의 터널링 박막에 응용하기 위하여 초박형 실리콘 옥시나이트라이드 박막의 증착과 이의 특성을 분석하였고, 실제 어플리케이션에 적용하였다. 실리콘 산화막과 실리콘 계면상에 존재하는 질소는 터널링 전류와 결함 형성을 감소시키며, 벌크 내에 존재하는 질소는 단일 실리콘 산화막에 비해 더 두꺼운 박막을 커패시턴스의 감소없이 이용할 수 있는 장점이 있다. 아산화질소 플라즈마를 이용하여 활성화된 질소 및 산소 라디칼들이 실리콘 계면을 개질하여 초박형 실리콘 옥시나이트라이드 박막을 형성할 수 있다. 플라즈마 처리 시간과 RF power의 변화에 따라 형성된 실리콘 옥시나이트라이드 박막의 두께 및 광학적, 전기적 특성을 분석하였다. 아산화질소 플라즈마 처리 방법을 사용한 실리콘 옥시나이트라이드 박막을 시간과 박막 두께의 함수로 전환해보면 초기적으로 증착률이 높고 시간이 지남에 따라 두께 증가가 포화상태에 도달함을 확인할 수 있다. 아산화질소 플라즈마 처리 시간의 변화에 따라 형성된 박막의 전기적인 특성의 경우, 플라즈마 처리 시간이 짧은 실리콘 옥시나이트라이드 박막의 경우 전압의 변화에 따라 공핍영역에서의 기울기가 현저히 감소하며 이는 플라즈마에 의한 계면 손상으로 계면결합 전하량이 증가에 기인한 것으로 판단된다. 또한, 전류-전압 곡선을 활용하여 측정한 터널링 메카니즘은 2.3 nm 이하의 두께를 가진 실리콘 옥시나이트라이드 박막은 직접 터널링이 주도하며, 2.7 nm 이상의 두께를 가진 실리콘 옥시나이트라이드 박막은 F-N 터널링이 주도하고 있음을 확인할 수 있다. 결론적으로 실리콘 옥시나이트라이드 박막을 활용하여 전기적으로 안정한 박막트랜지스터를 제작할 수 있었으며, 2.5 nm 두께를 경계로 터널링 메커니즘이 변화하는 특성을 이용하여 전하 주입 및 기억 유지 특성이 효과적인 터널링 박막을 증착하였고, 이를 바탕으로 다결정 실리콘 비휘발성 메모리 소자를 제작하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.1024-1035
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• 2006

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (circumferentially closed), circular rings with an elliptical or circular cross-section. Displacement components $u_r,\;u_\theta\;and\;u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the circular rings are formulated, and upper bound values of the frequencies are obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the rings. Novel numerical results are presented for the circular rings having an elliptical cross-section based upon 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and ones obtained from thin and thick ring theories, experiments, and another 3-D method.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.1-7
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• 2010

Interfacial reaction characteristics of a Bi-10Cu-20Sb-0.3Ni Pb-free alloy on Cu pad was investigated by reflow soldering at $430^{\circ}C$. The thickness of interfacial reaction layers with respect to the soldering time was also measured. After the reflow soldering, it was observed that a $(Cu,Ni)_2Sb$, a $Cu_4Sb$ intermetallic layer, and a haze layer, which is consisted of Bi and $Cu_4Sb$ phases, were successively formed at the Bi-10Cu-20Sb-0.3Ni/Cu interface. The total thickness of the reaction layers was found to be linearly increased with increasing of the reflow soldering time up to 120 s. As the added Ni element did not participate in the formation of the thickest $Cu_4Sb$ interfacial layer, suppression of the interfacial growth was not observed.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.588-596
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• 2012

This paper presents a new semi-analytical annular Mindlin plate element with which out-of-plane natural vibration of thick disks can be analyzed simply, efficiently, and accurately through FEM by including effects of rotary inertia and transverse shear deformation. Using static deformation modes which are exact solutions of equilibrium equations of annular Mindlin plate, the element interpolation functions, stiffness and mass matrices corresponding to each number of nodal diameters are derived. The element is capable of representing out-of-plane rigid-body motions exactly and free from shear locking. Natural frequencies of uniform and multi-step disks with or without concentric ring support are analyzed by applying the presented element. Such results are compared with theoretical predictions of previous works or FEA results obtained by using two-dimensional shell element to investigate the convergence and accuracy of the presented element.