• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.567-568
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• 2006

We investigate the structures and the formation energy of inversion domain boundaries (IDBs) using the Tersoff empirical potential. Four kinds of IDBs ( A and B types for IDB* and Holt ) are considered. The IDBs with A type are energetically favorable compared to B type with the structural instability. The IDB* is also more stable than the Holt type in spite of fourfold and eightfold rings of bonds. We calculate the atomic configurations of the Holt IDBs induced by the interactions of the IDB* with the stacking faults $I_1$ and $I_2$. The stacking fault $I_2$ interacted with $I_1$ on the IDB induces the structural transformation from IDB* to Holt type.

• Applied Microscopy
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• 제50권
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• pp.17.1-17.9
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• 2020

Recent advances in fabrication have enabled radial-junction architectures for cost-effective and high-performance optoelectronic devices. Unlike a planar PN junction, a radial-junction geometry maximizes the optical interaction in the three-dimensional (3D) structures, while effectively extracting the generated carriers via the conformal PN junction. In this paper, we report characterizations of radial PN junctions that consist of p-type Si micropillars created by deep reactive-ion etching (DRIE) and an n-type layer formed by phosphorus gas diffusion. We use electron-beam induced current (EBIC) microscopy to access the 3D junction profile from the sidewall of the pillars. Our EBIC images reveal uniform PN junctions conformally constructed on the 3D pillar array. Based on Monte-Carlo simulations and EBIC modeling, we estimate local carrier separation/collection efficiency that reflects the quality of the PN junction. We find the EBIC efficiency of the pillar array increases with the incident electron beam energy, consistent with the EBIC behaviors observed in a high-quality planar PN junction. The magnitude of the EBIC efficiency of our pillar array is about 70% at 10 kV, slightly lower than that of the planar device (≈ 81%). We suggest that this reduction could be attributed to the unpassivated pillar surface and the unintended recombination centers in the pillar cores introduced during the DRIE processes. Our results support that the depth-dependent EBIC approach is ideally suitable for evaluating PN junctions formed on micro/nanostructured semiconductors with various geometry.

• 국제강구조저널
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• 제18권5호
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• pp.1525-1540
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• 2018

A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord-brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load-stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord-brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.

• Journal of Photoscience
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• 제7권2호
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• pp.67-71
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• 2000

A quantum-chemical investigation on the conformations and electronic properties of trans(diphenyl-diheterocyclic) ethenes(t-PHEs) as building block for fully $\pi$-conjuated polymer are performed in order to display the effects of heterocyclic ring substitution. Structures for the molecules, t-PHEs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF methods, with 6-31G basic set. The potential energy curves with respect to the change of single are obtained by using ab initio HF/6-31G basic set. The curves are not similar shapes in the molecules with respect to heterocyclic rings. It is shown that the steric repulsion interactions between phenyl ring and heterocyclic ring are subjected to different type with the respect to each heterocyclic ring. Electronic properties of the molecules were molecules were obtained by applying the optimized structures and selected geometries to the extended Huckel method. To investigate the change of HOMO-LUMO gap with respedt to the torsion angle, we select the optimized structures. By using the results, the dependency of conjugation for the energy gaps is analyzed. For t-PHE the energy gap increase up to 0.52 eV compared with its planar structure. In the cases of t-PHE and t-PHE, the energy gap increase by 1.29 and 1.15 eV, respectively, compared with its planar structure.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.267-272
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• 2006

Optical waveguide based on symmetric and asymmetric Mach-Zehnder interferometer(MZI) type was designed, fabricated and measured the optical characteristics for the application of biosensor. The wavelength of the input optical signal for the device was 1550 nm. And the difference of refractive index was $0.45\;{\Delta}\%$ between core and cladding of the device. The TM(Transverse Magnetic) mode optical properties of the biosensor were analyzed with the refractive index variation of gold thin film deposited for overclad. Nowadays, nano-photonic crystal structures have been paied much attention for its high optical sensitivity. There is a technique to realize the structure, which is called Dip-Pen Nanolithography(DPN) process. The process requires a nano-scale process patterning resolution and high reliability. In this paper, two dimensional nano-photonic crystal array on the surface was proposed for improving the sensitivity of optical biosensor. And the Dip-Pen Nanolithogrphy process was investigated to realize it.

• Earthquakes and Structures
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• 제8권3호
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• pp.555-572
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• 2015

This paper presents an experimental study of three two-dimensional (2D/planar) steel reinforced concrete (SRC) T-shaped column-RC beam hybrid joints and six 3D SRC T-shaped column-steel beam hybrid joints under low cyclic reversed loads. Considering different categories of steel configuration types in column cross section and horizontal loading angles for the specimens were selected, and a reliable structural testing system for the spatial loading was employed in the tests. The load-displacement curves, carrying capacity, energy dissipation capacity, ductility and deformation characteristics of the test subassemblies were analyzed. Especially, the seismic performance discrepancies between planar hybrid joints and 3D hybrid joints were intensively compared. The failure modes for planar loading and spatial loading observed in the tests showed that the shear-diagonal compressive failure was the dominating failure mode for all the specimens. In addition, the 3D hybrid joints illustrated plumper hysteretic loops for the columns configured with solid-web steel, but a little more pinched hysteretic loops for the columns configured with T-shaped steel or channel-shaped steel, better energy dissipation capacity & ductility, and larger interlayer deformation capacity than those of the planar hybrid joints. Furthermore, it was revealed that the hysteretic loops for the specimens under $45^{\circ}$ loading angle are generally plumper than those for the specimens under $30^{\circ}$ loading angle. Finally, the effects of steel configuration type and loading angle on the seismic damage for the specimens were analyzed by means of the Park-Ang model.

• Structural Engineering and Mechanics
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• 제9권2호
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• pp.111-126
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• 2000

Truss type structures are attractive to a variety of engineering applications on earth as well as in space due to their high stiffness to mass ratios and ease of construction and fabrication. During the service life, an individual member of a truss structure may lose load carrying capacity due to many reasons, which may lead to collapse of the structure. An analytical and computational procedure has been developed to study the response of truss structures subject to member failure under static and dynamic loadings. Emphasis is given to the dynamic effects of member failure and the propagation of local damage to other parts of the structure. The methodology developed is based on nonlinear finite element analysis technique and considers elasto-plastic material nonlinearity, postbuckling of members, and large deformation geometric nonlinearity. The pseudo force approach is used to represent the member failure. Results obtained for a planar nine-bay indeterminate truss undergoing sequential member failure show that failure of one member can initiate failure of several members in the structure.

• 전기전자학회논문지
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• 제25권1호
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• pp.37-41
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• 2021

본 논문에서는 UWB 센서에 응용 가능한 다층기판을 이용한 광대역 특성을 가지는 보우타이 안테나를 설계하였다. 제안된 소형 보우타이 안테나는 2층의 기판으로 설계 및 제작되었으며 전체 안테나의 두께는 4.5mm이다. 제안된 안테나는 보우타이 모양의 방사체와 평면형 발룬으로 구성된다. 설계된 방사체와 발룬의 간단한 연결로 안테나가 설계되도록 하여 다양한 구조로 쉽게 구현 가능하도록 하였다. 제작된 안테나는 6.8~10 GHz의 주파수 범위에서 3~6dBi의 이득을 가졌다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2002년도 봄 학술발표논문집 Vol.29 No.1 (A)
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• pp.685-687
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• 2002

RNA pseudoknot은 RNA 삼차 구조를 형성하는 중요한 구조요소일 뿐만 아니라, RNA 분자에서 중요한 역할을 한다. 지금까지 RNA pseudoknot 구조를 시각화하는 도구는 개발되어 있지 않기 때문에 대부분의 pseudoknot 구조의 시각화 작업은 수작업으로 이루어지고 있다. 본 논문은 RNA pseudoknot을 시각화를 위한 새로운 pseudoknot 표현 기법과 시각화 알고리즘에 대해서 소개한다. 새로운 표현기법은 모든 H-type pseudoknot을 uniform planar graph로 나타내고 RNA sequence의 진행방향을 따라가기가 쉽게 되어있다. 알고리즘을 이용하여 PseudoViewer라는 프로그램을 개발하였으며 PseudoViewer는 어떠한 시스템에서도 작동할 수 있는 Java로 구현되었다. 그 결과는 pseudoknot을 명확히 구분되고 보기 쉽도록 시각화됨을 보여준다.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.403-406
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• 2011

Here we report Airy beams coupled with waveguide modes. These waveguide Airy (WAiry) beams propagate through layered planar structures inheriting the characteristics of waveguide modes as well as those of Airy beams, such as diffraction-free and accelerating features. In particular, we focus on the WAiry beams associated with backward waveguide modes, showing that the backward feature can alter the trajectories of the WAiry beams significantly. Based on this, we propose a new scheme of waveguide-type polarization/power beam splitters.