• Structural Engineering and Mechanics
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• 제42권6호
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• pp.883-897
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• 2012

Cold-formed channel sections are used in a variety of applications in which they are required to absorb deformation energy. This paper investigates the collapse behaviour and energy absorption capability of cold-formed steel channels with flange edge stiffeners under large deformation major-axis bending. The Yield Line Mechanism technique is applied using the energy method, and based upon measured spatial plastic collapse mechanisms from experiments. Analytical solutions for the collapse curve and in-plane rotation capacity are developed, and used to model the large deformation behaviour and energy absorption. The analytical results are shown to compare well with experimental values. Due to the complexities of the yield line model of the collapse mechanism, a simplified procedure to calculate the energy absorbed by channel sections under large bending deformation is developed and also shown to compare well with the experiments.

• 천문학회보
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• 제38권1호
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• pp.41.2-41.2
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• 2013

We present the statistical properties of a volume-limited sample of 7,429 nearby (z = 0.033-0.044) galaxies from the Sloan Digital Sky Survey Data Release 7. By performing a visual inspection, we classified our sample galaxies according to the Hubble sequence (Hubble 1926, 1936). Then we excluded apparently smaller and flatter galaxies from our database because morphology classification on them turned out to be difficult. Our results cover structural (e.g. concentration index, color, magnitude, stellar mass, etc.), spectroscopic (e.g. velocity dispersion, $H{\beta}$ absorption line, Fe absorption line, Mg absorption line, accretion rate, $H{\alpha}$ emission line, etc.), and environmental (e.g. density, etc.) properties of each morphology type based on morphology distribution. For this analysis, we used the recent re-measurements of spectral line strengths by Oh and collaborators (2011). Our statistics confirm the up-to-date understanding on galaxy populations, e.g., correlations between morphology and line strengths and in turn derived ages and so on.

• 대한금속재료학회지
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• 제49권4호
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• pp.329-333
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• 2011

To develop wide-band noise absorbers with a special design for low-frequency performance, this study proposes a tin oxide (Sn-O) thin films as the noise absorbing materials in a microstrip line. Sn-O thin films were deposited on polyimide film substrates by reactive sputtering of the Sn target under flowing $O_{2}$ gas, exhibiting a wide variation of surface resistance (in the range of $10^{0}-10^{5}{\Omega}$) depending on the oxygen partial pressure during deposition. The microstrip line with characteristic impedance of $50\Omega$ was used for the measurement of noise absorption by the Sn-O films. The reflection parameter $(S_{11})$ increased with a decrease of surface resistance due to an impedance mismatch at the boundary between the film and the microstrip line. Meanwhile, the transmission parameter $(S_{21})$ diminished with a decrease of surface resistance resulting from an Ohmic loss of the Sn-O films. The maximum noise absorption predicted at an optimum surface resistance of the Sn-O films was about $150{\Omega}$. For this film, greater power absorption is predicted in the lower frequency region (about 70% at 1 GHz) than in conventional magnetic sheets of high magnetic loss, indicating that Ohmic loss is the predominant loss parameter for the conduction noise absorption in the low frequency band.

• 천문학회지
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• 제54권5호
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• pp.139-155
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• 2021

We present an updated version of the multilayer spectral inversion (MLSI) recently proposed as a technique to infer the physical parameters of plasmas in the solar chromosphere from a strong absorption line. In the original MLSI, the absorption profile was constant over each layer of the chromosphere, whereas the source function was allowed to vary with optical depth. In our updated MLSI, the absorption profile is allowed to vary with optical depth in each layer and kept continuous at the interface of two adjacent layers. We also propose a new set of physical requirements for the parameters useful in the constrained model fitting. We apply this updated MLSI to two sets of Hα and Ca II line spectral data taken by the Fast Imaging Solar Spectrograph (FISS) from a quiet region and an active region, respectively. We find that the new version of the MLSI satisfactorily fits most of the observed line profiles of various features, including a network feature, an internetwork feature, a mottle feature in a quiet region, and a plage feature, a superpenumbral fibril, an umbral feature, and a fast downflow feature in an active region. The MLSI can also yield physically reasonable estimates of hydrogen temperature and nonthermal speed as well as Doppler velocities at different atmospheric levels. We conclude that the MLSI is a very useful tool to analyze the Hα line and the Ca II 8542 line spectral daya, and will promote the investigation of physical processes occurring in the solar photosphere and chromosphere.

• ETRI Journal
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• 제46권3호
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• pp.413-420
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• 2024

A dual-band bio-implantable compact antenna with a meander-line structure is presented. The proposed meander-line antenna resonates at the industrial, scientific, and medical (2.4 GHz) and wireless medical telemetry (1.4 GHz) bands. The meander-line structure is selected as a radiating patch given its versatile and effective design. With a dimension of only 10 mm × 10 mm × 0.635 mm, the designed antenna is compact. Considering a skin phantom, the proposed antenna was designed, optimized, and simulated. The Rogers RT/duroid 6010 substrate material with high dielectric constant was used to fabricate the meander-line dual-band implantable antenna, which was validated experimentally. The superstrate was made of the same material. Experiments were conducted on skin-mimicking gel. The designed meander-line antenna has a high peak gain of -21 dBi at 2.4 GHz, and its maximum specific absorption rate is compliant with IEEE safety standards.

• 대한화학회지
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• 제21권5호
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• pp.362-371
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• 1977

이 論文에서는 NMR 吸收線과 FID 曲線의 모양을 硏究함에 있어서의 projection operation의 應用法을 探索하였다. 이 projection operator法은 NMR 吸收線과 FID 函數를 硏究하는데에 基礎가 되는 한 벌의 hierarchy equation들을 誘導하는데에 便利한 手段이 됨을 밝혔다. 逐次近似法이나 적당한 decoupling 近似를 쓰면 이들 方程式은 NMR 吸收線이나 FID 函數를 理論的으로 計算하는데에 좋은 出發點이 될 수 있을 것이다. NMR 吸收線에 對한 간단한 linear response theory의 考察과 吸收線과 FID 函數間의 關係도 記述하였다.

• 천문학회보
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• 제45권1호
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• pp.63.2-63.2
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• 2020

FLASH is a blind neutral hydrogen (HI) absorption line survey, eventually targeting about 100,000 background radio continuum sources in the entire southern sky using the full 36-antenna of the Australian Square Kilometre Array Pathfinder (ASKAP). Our primary goal is to search for associated and intervening HI absorption lines in the intermediate redshift range 0.4 < z < 1.0. The survey aims to understand the evolution of HI gas in galaxies as well as various physical mechanisms in active galactic nuclei, such as accretion and feedback processes. In this poster, we give an overview of the FLASH survey and present the preliminary results from our first 100-hrs of pilot observations. The latest survey data covers 1,000 square degrees and is ideal for validating observation and data processing in the continuous 300MHz-width low frequency ASKAP band (700-1000MHz). One of the crucial objectives of the pilot survey is to establish the analysis methodology that will be applied to upcoming large absorption surveys in the future. We discuss our data quality validation and present some detections of associated/intervening HI absorption lines. These absorption lines allow us to trace the cold gas properties of active and normal galaxies at higher redshifts where the HI emission line is too weak to be detectable.

• Journal of Astronomy and Space Sciences
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• 제16권1호
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• pp.1-10
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• 1999

The archival long-slit spectra, covering the wavelength range 4050 ~ 5150 $\AA$, have been used to investigate the radial behavior of absorption line fea-tures (G4300, Fe4383, Ca4455, Fe4531, and $H{\beta}$) of an elliptical galaxy NGC 5846A. The heliocentric recession velocity of NGC 5846 has been derived as $1949{\pm}87\;kms^{-1}$. Fe absorption lines of NGC 5846A show significant radial gradients with the mean slope of $\Delta/Delta(r")=-0.863\pm0.202$. There is also a significant radial gradient of G band with a slope of $-1.109{\pm}0.098$. On the other hand, no radial gradients has been detected on the Ca4455 and $H{\beta}$ absorptions of NGC 5846A. A metallicity gradient, which is derived from the Fe line gradients, is similar to the abundance gradient predicted by Larson's (1975) dissipative models for the formation of elliptical galaxies. We also note that a galaxy-galaxy interaction could affect the line gradients of NGC 5864A.

• 천문학논총
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• 제15권spc1호
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• pp.1-13
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• 2000

We review the early historical developement of astronomical spectrographs, properties of emission line spectra of HII regions in spiral galaxies, and absorption line features of galactic globular clusters. Emission line spectra of HII regions within three spiral galaxies NGC 300, NGC 1365, and NGC 7793, which were observed from AAT/IPCS, had been analysed, and we discuss the abundances of elements in HII regions and the radial abundace gradients through the galaxies. The radial UBV color variations of two globular clusters, NGC 1851 and NGC 2808, were examined for correlations with radial variations of several absorption lines in the integrated spectra, which were obtained from SAAO 74 inch telescope and image tube spectrograph. Nine giant star's spectra in NGC 3201 were also obtained and analysed for the radial abundance gradients in the globular cluster. The results show that the presence of a radial color gradient in a globular cluster is correlated with the presence of abundance gradients. Finally, we suggest some scientific programs for the new high dispersion spectrograph, which will be installed to the BOAO 1.8m telescope.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.435-436
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• 2009

LNG 선박에 설치된 대용량 탱크의 누출을 검사하는 방법으로 $NH_3$를 사용하고 있다. 본 논문에서는 광음향효과를 이용하여 $NH_3$의 흡수선을 조사하였고, 이를 이용하여 $NH_3$의 농도를 측정하는 방법을 실험하였다.