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이성재,형식,김미혜 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.3
Using the spectroscopic data secured with the Hamilton Echelle Spectrograph attached to a 3-m telescope at the Lick Observatory, we derived the expansion velocities from various line profiles of Hi, He i, Ciii, Nii, Niii, [N ii], Oii, [O i], [Oii], [Oiii], [Ne iii], [Ar iii], [Ar iv], [S ii], [S iii], [Cl iii], and [Cl iv] in the 3600 °A to 10,000 °A wavelength range based on the full width at half maximum and the double peak. Using the recombination or permitted lines, we also derived elemental abundances and compared them with other values derived with forbidden lines and those found in the literature. The faster expansion velocities of the permitted Oii, Nii, Niii and perhaps Cii lines imply the existence of a somewhat smaller inner shell inside the outer main shell. The symmetrical shape of the permitted line profiles also indicates that these permitted line zone is symmetrical, e.g., a spherical shell or bipolar + torus structures, which might be evidence of relatively recent ejection from the central star. The nebular shell likely consists of a swiftly expanding inner shell and an outer normal shell excited by a central star of about 55,000 K. The former compact zone appears to be responsible for the permitted C, N, and O lines while the latter extended shell appears to be responsible for H, He, and forbidden lines. The location, large radial velocity, and less-enhanced C, N, and O abundances imply that NGC 6833 is likely to be a halo planetary nebulae.
Supersonic, Rotating Accretion Flows around Black Holes in a Two-Dimensional Cylindrical Geometry
이성재,류동수 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.4
We developed a new code that calculates the evolution of the angular momentum accurately in accretion °ows in a two-dimensional cylindrical geometry. With the code, supersonic accretion °ows with small amounts of angular momentum were simulated. Our simulations showed that an accretion shock formed and that the structure with the shock was dynamically unstable. The instability could provide an explanation for quasi-periodic oscillations in the black holes of galactic microquasars.`孤
Electrical Width Determination of Silicon Nanowires Prepared by Using the Top-Down Method
이성재 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6
High-aspect-ratio nanowires of various widths and lengths (105 nm ∼ 20 μm and 2 ∼ 20 μm, respectively), but of fixed thickness (40 nm), were prepared by using the top-down method, and their resistances were measured in the two-terminal configuration. By taking into account the series resistance corresponding to the trapezoidal section of the channel connecting a nanowire to a wider electrode region, we obtained a sheet resistance and a source/drain resistance of 16.81 and 11.17 kΩ, respectively, in a consistent manner. We also determined the effective electrical widths, which are different from the physical widths by as much as 40 nm for a 105-nm-wide nanowire, and found a linear dependence of the surface depletion layer’s thickness at the side walls on their physical width, which was attributed to structural damage that occurred during the plasma etch process.
Size Dependence of the Transport Properties of Silicon Nanostructures
이성재 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6
Silicon devices involving various p-type silicon nanostructures with a fixed length 20 μm and thickness 40 nm, but with varying width in the range from ∼ 100 nm to 20 μm, were prepared by using the top-down method in order to systematically study the width dependence of their intrinsic transport property. Based on the Id-Vg characteristic measurements, the hole mobility (μh) and concentration (nh) were extracted for all nanostructures. For structures of large widths (w > 1.0 μm, nanoribbon-type), nh decreases from 5.5 to 2.4 × 1017 cm−3 while μh increases from 160 to 380 cm2V−1s−1 as the width narrows down from 20 to 1.0 μm. Interestingly, however, nh and μh are found to be correlated such that their product remains nearly constant for this width region, the origin of which is unclear. For structures of small widths (w ≤ 500 nm, nanowire-type), nh remains more or less constant at about 2.4 × 1017 cm−3 while μh decreases steadily from 340 to 240 cm2V−1s−1 as the width narrows down from 500 to 96 nm. This behavior of mobility degradation with width narrowing in the nanowire region is likely to originate from the enhanced surface scattering effect, but a detailed microscopic theory should be developed to explain this effect quantitatively.
이성재,마호섭 경상대학교 농업생명과학연구원 2018 농업생명과학연구 Vol.52 No.4
본 연구는 최근 국내에서 발생한 산사태를 중심으로 수량화이론을 이용하여 산림환경인자가 발생면적에 미치는 영향 분석을 통해 예방적인 측면에서 산사태 발생 위험성에 대한 예측기준을 작성하였다. 산사태 재해로 발생면적에 영향을 미치는 각 인자의 기여도는 토심(0.3350)로서 가장 높았으며, 다음으로 임상(0.1741), 표고(0.1416), 사면위치(0.1266), 종단사면(0.1236), 모암(0.1146), 경사(0.1133), 방위(0.1084)으로 높게 나타났다. 산사태 발생 위험 기여도가 높은 8개 인자의 category별 상대점수 범위는 0점에서 1.2372점 사이에 분포하고 있었고 중앙값은 0.6186점이었다. 이 점수를 기준으로 산사태 발생 위험성을 4개 등급으로 구분한 예측 판정표를 작성하였다. Ⅰ등급의 점수는 0.9280 이상, Ⅱ등급은 0.6187∼0.9279, Ⅲ등급은 0.3094∼0.6186, IV등급은 0.3093 이하로 나타나 Ⅰ등급, Ⅱ등급, Ⅲ등급에서 산사태 발생 비율이 97.4%로서 비교적 높은 적중률을 보였다. 따라서 본 판정표는 산사태발생 위험도 판정에 유용하게 활용할 수 있을 것으로 판단된다. This study was carried out to analyze the impacts of each factors by using the quantification theory(I) for the prediction of Landslide hazard areas. The results obtained from this study are summarized as follows. According to the range by the stepwise regression analysis, it was shown in order of soil depth(0.3350) was the highest. forest type(0.1741), altitude(0.1416), position(0.1266) vertical slope(0.1236), parent rock(0.1146), slope gradient(0.1133), aspect(0.1084). The extent of the normalized score by category of 8 factors was 0 to 1.2372, and the middle score was 0.6186. The prediction criteria on Landslide occurrence based on the normalized score divided into 4 grade. It was over 0.9280 for class I, class Ⅱ was 0.6187 to 0.9279, class Ⅲ 0.3094 to 0.6186 and class Ⅳ was below 0.3093. The prediction on Landslide occurrence appeared relatively high accuracy rate as 97.4% for class I, II and III. Therefore, this prediction criteria for Landslide will be very useful for judgement of dangerous slope.