• Structural Engineering and Mechanics
• /
• 제32권4호
• /
• pp.531-547
• /
• 2009

This paper presents the experimental results on the strength behavior and failure modes of box beam-to-circular column connections in steel piers. Previous research introduced parameters such as joint central angles, extension of horizontal stiffeners, and use of equivalent web depth, which ignored strength behavior and failure modes of box beam-to-circular column connections. The use of equivalent web depth $d_2$ is not reasonable when central angle ${\alpha}$ is closer to $90^{\circ}$; therefore, a monotonic loading test has been performed for eight connection specimens. From the test, it is identified that the connection with the circular column is stronger than the connection with the box-sectioned substitution column. Also, the strength of the beam-to-column connections with horizontal stiffeners is higher than the one of the no column stiffeners. The concrete-filled effect of box beam-to-circular column connection is also investigated, and the experimental yield strength of the connection is compared with the theoretical one. Also, more a reasonable equivalent web depth is suggested. The failure modes of connection are clearly defined.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.586-589
• /
• 1999

Organic semiconductors based on conjugated thiophene oligomer have great potential to be utilized as an active layer far electronic and optoelectronic devices. In this study, $\alpha$ -sexithiophene($\alpha$-6T) thin films and various electrode materials were deposited by Organic Molecular Beam Deposition(OMBD) and vacuum evaporation respectively. Those films were photolithographically patterned fur measurements. Electrical characterization of the thin film transistor with various channel length were measured, and field effect mobility is calculated by formula.

• 한국재료학회지
• /
• 제21권10호
• /
• pp.563-567
• /
• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• 대한기계학회논문집A
• /
• 제23권6호
• /
• pp.1026-1038
• /
• 1999

Interlaminar fracture toughness of carbon/epoxy composite materials has been studied under tensile and flexural loading by the use of width tapered double cantilever beam(WTDCB) and end notched flexure(ENF) specimens. This study has significantly examined the effect of various interfacial ply orientation, ${\alpha}(0^{\circ},\;45^{\circ}\;and\;90^{\circ})$ and crack propagation direction, ${\theta}(0^{\circ},\;15^{\circ},\;30^{\circ}\;and\;45^{\circ})$ in terms of critical strain energy release rate through experiments. Twelve differently layered laminates were investigated. The data reduction for evaluating the fracture energy is based on compliance method and beam theory. Beam theory is used to analyze the effect of crack propagation direction. The geometry and lay-up sequence of specimens are considered various conditions such as skewness parameter, beam volume, and so on. The results show that the fiber bridging occurred due to the non-midplane crack propagation and causes the difference of fracture energy evaluated by both methods. For safer and more reliable composite structures, we obtain the optimal stacking sequence from initial fracture energy in each mode.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.409-414
• /
• 1999

The influence of ion beam energy and reactive oxygen partial pressure on the electrical and crystallographic characteristics of transition metal oxide compound(Cr0x) film was studied in this paper. Chromium oxide films were prepared onto the coverglass using Ion Beam Sputter Deposition(1BSD) technique according to the processing conditions of the partial pressure of reactive oxygen gas and ion beam energy. Crystallinity and grain size of as-deposited films were analyzed using XRD analysis. Thickness and Resistivity of the films were measured by $\alpha$-step and 4-point probe measurement. As results, according to the XRD, XPS and resistivity measurement, the deposited films were the cermet type films which has a crystal structure including amorphous oxide(a-oxide) phase and metal Cr phase simultaneously. The increasernent of the ion b m energy during the deposition process happened to decreasernent of metal Cr grain size and the rapid change of resistivity above the critical $O_2$ partial pressure.

• 방사선산업학회지
• /
• 제6권1호
• /
• pp.17-21
• /
• 2012

The effects of gamma ray or electron beam irradiation on herbaceous medicinal plants were investigated in terms of the composition of volatile constituents using the aerial parts or leaves of Artemisia princeps Pamp. cv. Ganghwayakssuk and Artemisia argyi cvs. Namhaeyakssuk and Hwanghaessuk. The composition of volatile constituents in leaves was clearly distinguishable among the three Artemisia cultivars. However, the relative proportions of the major volatile constituents such as 1,8-cineole, ${\alpha}$-pinene, camphene, santolina triene, and artemesia triene, were similarly changed in two or three cultivars by gamma ray or electron beam irradiation. In particular, the proportion of 1,8-cineole was increased up to 1.29- to 1.71-fold in the three cultivars after irradiation with gamma ray. These results suggest that gamma ray or electron beam irradiation can be applied to modulate the composition of volatile constituents in the leaves of Artemisia plants.

• 대한기계학회논문집A
• /
• 제26권11호
• /
• pp.2270-2276
• /
• 2002

Dynamic stability of a rotary oscillating cantilever beam is presented in this study. Using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton's principle and transformed into dimensionless forms. Stability diagrams of the first order approximate solutions are obtained by using the multiple scale perturbation method. The stability diagrams show that relatively large unstable regions exist near the combination of the first chordwise bending natural frequency and the first stretch natural frequency. This result is verified by using the generalized -$\alpha$ method.

• 반도체디스플레이기술학회지
• /
• 제5권1호
• /
• pp.51-55
• /
• 2006

MgO thin films were prepared through electron-beam deposition onto ITO-coated glass substrates in order to measure electrical, dielectric, and microstructural properties. Design of experiments was performed in this study with the aim to understanding of the effects of processing variables, e.g., substrate temperature and filament current of an e-beam evaporator statistically. Leakage currents, relative dielectric constants, and diffraction intensities of MgO thin films were analyzed statistically, following the analysis procedure provided in the design of experiments. The leakage current level of MgO thin films has been found to be statistically significant at the level of $\alpha=0.1$.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 I
• /
• pp.335-340
• /
• 2001

Dynamic stability of a rotary oscillating cantilever beam is presented in this study. Using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton's principle and transformed into dimensionless forms. Stability diagrams of the first order approximate solutions are obtained by using the multiple scale perturbation method. The stability diagrams show that relatively large unstable regions exist near the combination of the first chordwise bending natural frequency and the first stretch natural frequency. This result is verified by using the generalized-${\alpha}$ method.

• 한국식품과학회지
• /
• 제30권6호
• /
• pp.1312-1320
• /
• 1998

실험재료는 시중에서 판매되는 우육(등심) 부위를 이용하였으며, 생육 시료의 함기포장과 진공포장은 폴리에틸렌 필름을 이용하였고, 전자선 조사(0, 1, 2, kGy)를 실시한 후 $2{\sim}4^{\circ}C$의 냉장실에서 보관하면서 저장기간 별(0, 7, 14일) 실험에 사용하였다. 가열 시료는 oven에서 육 내부가 $70^{\circ}C$가 될 때까지 가열한 다음 함기 포장과 진공포장을 즉시 실시한 후 생육 시료와 같은 조건으로 전자선 조사를 실시한 다음 $2{\sim}4^{\circ}C$의 냉장실에서 보관하면서 생육 시료와 같은 저장기간별 콜레스테롤 산화물의 발생 종류와 발생량을 조사한 결과는 다음과 같다. 가열하지 않은 우육 등심의 함기 포장에서는 $7{\alpha}-hydroxycholesterol,\;{\beta}-epoxide,\;7{\beta}-hydroxycholesterol$, 7-ketocholesterol이 $0.5{\mu}g/g$ 이상 발생하였으며, 전 저장기간 동안 cholestanetriol과 ${\alpha}-epoxide$은 극소량($0.5\;{\mu}g/g$ 이하)발생하였다. 가열하지 않은 우육 등심의 진공포장에서는 전 저장기간 동안 $7{\alpha}-hydroxycholesterol$, 7-ketocholesterol, cholestanetriol과 ${\alpha}-epoxide$은 극소량$(0.5\;{\mu}g/g$ 이하) 발생하였다. 우육 등심을 가열한 후 함기포장에서는 전 저장기간 동안 cholestanetriol과 ${\alpha}-epoxide$은 극소량$(0.5\;{\mu}g/g$ 이하)였지만, $7{\alpha}-hydroxycholesterol\;(1.53{\sim}26.81),\;{\beta}-epoxide\;(1.07{\sim}5.23),\;7{\beta}-hydroxycholesterol\;(40.64{\sim}101.30)$, 7-ketocholesterol $(7.16{\sim}33.91)$. 모든 결과에서 처리구에 따른 콜레스테롤 산화물의 전체 발생량은 조사 수준이 증가할수록 유의적으로 증가하였으며(P<0.05), 저장기간이 경과함에 따라 전체 발생량이 유의적으로 증가하였다(P<0.05).