• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.109-118
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• 2001

대구지역은 광범위한 층리가 균일한 형태로 발견되는 지역으로 역학적인 이방성을 나타내고 있다. 이러한 이방성을 가진 지반은 지하 구조물의 거동이 등방과 다른 양상을 보이므로 이방성해석이 수행되어야 한다. 이에 본 연구에서 대구지역 셰일에 대해 암판정상 경암과 보통암에 대해 동일한 시료에서 등방과 이방상태의 탄성정수를 층리각도($\beta$)별로 산출하였고 이것을 바탕으로 하여 유한 요소법을 사용한 이방성 해석을 수행하였다. 해석결과 이방상태의 응력과 변위의 결과는 등방과 다름을 알 수 있었다. 변위는 층리각에 따라 등방에 비해 지표면에서 약 3배까지 증가하며, 록볼트는 최대 2.04배, 숏크리트는 2.93배 증가하게 나타난다. 또한, 측압계수(K$_{0}$)가 이방성 암반과 터널구조물에 미치는 영향을 알 수 있었다. 따라서, 본 지역과 같은 층리가 존재하는 지반의 구조물 건설에서 이방성해석이 필수적임을 알 수 있다.

• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.783-797
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• 2019

In this paper, we introduce and investigate a subclass ${\Im}_{\Sigma}({\alpha},{\beta},{\gamma})$ of analytic and bi-univalent functions of complex order in the open unit disk U in complex plane. Here, we obtain an upper bound for the second Hankel determinant of the functions belonging to this class. Moreover, several interesting conclusions of the results obtained here are also discussed.

• Bulletin of the Korean Chemical Society
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• v.16 no.3
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• pp.256-260
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• 1995

Laser induced fluorescence spectra of OH produced from photodissociation of $H_2O_2$ at 280-290 nm in the gas phase have been observed. By analyzing the Doppler profiles, the anisotropy parameter($\beta$ =-0.7) and the center of mass translational energy of the fragments have been measured. The measured energy distribution is well described by an impulsive model. The excited state leading to dissociation is found to be of 1Au symmetry. The dissociation from this state is prompt and direct with the fragment OH rotating in the plane perpendicular to the O-O bond axis.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.55-59
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• 2010

$Na^+$ ion conductivity can be improved by the substitution of an Mg atom for an Al atom to form a nonstoichiometric $Na^+$ $\beta$-alumina. We performed a first principles study to investigate the most stable substitution site of an Mg atom and the resulting structural change of the nonstoichiometric $Na^+$ $\beta$-alumina. Al atoms were classified as four different layers in the spinel block that are separated by conduction planes in the nonstoichiometric $Na^+$ $\beta$-alumina. The substitution of an Mg atom for an Al atom at a tetragonal site was more favorable than that at an octahedral site. The substitution in the spinel block was more favorable than that close to the conduction plane. This result was well explained by the volume changes of the polyhedrons, by the standard deviation of the Mg-O distance, and by the comparison with bulk MgO structure. Our result indicates that the most preferable site for the Mg atom was the tetrahedral site at the spinel block in the nonstoichiometric $Na^+$ $\beta$-alumina.

• Korean Journal of Optics and Photonics
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• v.20 no.4
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• pp.241-248
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• 2009

We suggest a new method to determine the off-alignment error of the composite film, together with in-plane($R_{in}$) and out-of-plane retardation($R_{th}$) of the compensation film, simultaneously. The composite film consists of a polarizing film and a compensation film for improvement of viewing angle of a liquid crystal display. We regarded the compensation film as o-plate with its optic axis along an arbitrary direction. By using an extended Jones matrix method, the polarization characteristics of the composite film are examined. The calculated Fourier constants, ($\alpha$, $\beta$) curves of the composite film as the azimuth angle is varied at the incident angles of $0^{\circ}$ and $50^{\circ}$, respectively, are used to determine the axis misalignment, the tilt angle and the azimuth angle of the compensation film by adopting the linear regressional analysis technique. Since this method can be applied for the inspection of the composite film even after laminating the polarizing film and the compensation film, it will be useful for simplifying the manufacturing process and reducing the production cost of liquid crystal display panels.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.193-197
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• 2013

In this study, ultrasonic nonlinear characteristics in the heat-treated aluminum alloy have been evaluated. The nonlinearity of ultrasonic wave has been measured as the acoustic nonlinear parameter ${\beta}$, depending upon the amplitude ratio of the second-order harmonic and the fundamental frequency component of ultrasonic wave propagating through the materials. The parameter ${\beta}$ measurement has been carried out with the reflected signals from the back-wall of specimens at the same plane using the contact-type transducers. The heat-treatment, aging, has been achieved at $300^{\circ}C$ for various durations in the range of 1 to 50 hours. The tensile strength and elongation are obtained by the tensile test and then compared with the parameter ${\beta}$. There is a peak of the acoustic nonlinear parameter ${\beta}$ on 5 hours aging and the ${\beta}$ decreases thereafter, exhibiting closed relations with tensile strength and elongation. Also, the heat-treatment time showing peak in the parameter ${\beta}$ was identical to that showing severe change in the ${\sigma}-{\varepsilon}$ curve. These results suggest that the acoustic nonlinear parameter ${\beta}$ can be used for monitoring the strength variations with aging of aluminum alloys.

• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.127-134
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• 2010

The dynamic instability for snapping phenomena has been studied by many researchers. Few paper deal with the dynamic bucking under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of dynamic instability when shallow EP(Elliptic Paraboliodal) shell of two degree of freedom are subjected to sinusoidal excitation with direct snapping and indirect snapping. By using Newmark-$\beta$ method, we can get the nonlinear response, and characteristics of the dynamic instability through the running response spectrum by FFT(fast Fourier Transform) and attractors are compared in the phase plane. Dynamic buckling loads are strongly influenced by the relationships between the natural frequency of structures and the dominant frequency of incident excitations.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.644-651
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• 1999

In this experiment the Iron phthalocyanine (FePc) films on Si-wafer and alumina pallet were prepared using vacuum sublimation with conditions of changing reaction time, temperature, and deposition rate. Then, some samples were annealed following annealing. Techniques such as XRD, SEM, and resistance measurement method, were dedicated to characterize the changes of surface structure, phase transformation and electric resistance sensitivity in accordance with change of film thickness. In proportion to the decrease of deposition temperature from $370^{\circ}C$ to $350^{\circ}C$, intensities of (200), (011), (211) and (114) planes of $\alpha$-phase were decreased and (100) plane of $\beta$-phase were appeared. The film thickness were controlled by regulating the volume of precursor material during rapid deposition. As a result, it was observed that crystalline particle size had been increased according to the increase of film thickness and $\alpha$-phase transformed to $\beta$-phase. In consequence of measuring the crystallinity of films annealed between $150^{\circ}C$ and $350^{\circ}C$, $\alpha$- to $\beta$-phase transformation was appeared to begin at $150^{\circ}C$ and completely transformed to $\beta$-phase at $350^{\circ}C$. Electric resistance sensitivity of FePc film to $NO_x$ gas along temperature change of FePc films was observed to be more stable with the decrease of the film thickness.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.111-114
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• 2011

As a growth-template of ZnO nanorods (NR), a hexagonal $\beta-Ni(OH)_2$ nanosheet (NS) was synthesized with the low temperature hydrothermal process and its microstructure was investigated using a high resolution scanning electron microscope and transmission electron microscope. Zinc nitrate hexahydrate was hydrolyzed by hexamethylenetetramine with the same mole ratio and various temperatures, growth times and total concentrations. The optimum hydrothermal processing condition for the best crystallinity of hexagonal $\beta-Ni(OH)_2$ NS was determined to be with 3.5 mM at $95^{\circ}C$ for 2 h. The prepared $Ni(OH)_2$ NSs were two dimensionally arrayed on a substrate using an air-water interface tapping method, and the quality of the array was evaluated using an X-ray diffractometer. Because of the similarity of the lattice parameter of the (0001) plane between ZnO (wurzite a = 0.325 nm, c = 0.521 nm) and hexagonal $\beta-Ni(OH)_2$ (brucite a = 0.313 nm, c = 0.461 nm) on the synthesized hexagonal $\beta-Ni(OH)_2$ NS, ZnO NRs were successfully grown without seeds. At 35 mM of divalent Zn ion, the entire hexagonal $\beta-Ni(OH)_2$ NSs were covered with ZnO NRs, and this result implies the possibility that ZnO NR can be grown epitaxially on hexagonal $\beta-Ni(OH)_2$ NS by a soluble process. After the thermal annealing process, $\beta-Ni(OH)_2$ changed into NiO, which has the property of a p-type semiconductor, and then ZnO and NiO formed a p-n junction for a large area light emitting diode.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.236-237
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• 2012

ZnO nanorods were grown on R-plane sapphire substrates with the seed layers annealed at different temperature. The effects of annealing temperature for the seed layers on the properties of the ZnO nanorods were investigated by scanning electron microscopy, X-ray diffraction, UV-visible spectroscopy, and photoluminescence. For the as-prepared seed layers, the ZnO nanorods and the ZnO nanosheets were observed. Only the ZnO nanorods were grown as the annealing temperature was above $700^{\circ}C$. The optical transmittance in the UV region was almost zero while that in the visible region was gradually increased as the annealing temperature increased to $700^{\circ}C$. The optical band gap of the ZnO nanorods was increased as the annealing temperature increased to $700^{\circ}C$. In the visible region, the refractive index was decreased with increasing the wavelength, and the extinction coefficient was decreased as the annealing temperature increased to $700^{\circ}C$. The non-linear exciton radiative life time of the FX emission peak was established by cubic equation. The values of Varshni's empirical equation fitting parameters were ${\alpha}=4{\times}10^{-3}eV/K$, ${\beta}=1{\times}10^4K$, and $E_g(0)=3.335eV$ and the activation energy was found to be about 94.6 meV.