• Textile Coloration and Finishing
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• v.21 no.3
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• pp.10-18
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• 2009

Dyeing process of the natural indigo powder onto ramie and silk fabrics was investigated by using glucose and calcium hydroxide as a reducing system. Effect of reduction and dyeing conditions such as temperature and time of reduction/dyeing, and concentrations of glucose and calcium hydroxide on the dyeing process were explored. Indigo powder was obtained by drying the conventional niram paste in an oven at $50^{\circ}C$. Color strength of the dyed fabrics was evaluated by K/S value measured at the wavelength of maximum absorption(${\lamda}$max). Munsell color coordinates(H V/C) were used to compare fabric colors of ramie and silk. Ramie fabric showed purple-blue color for all the temperature and time. On the contrary, silk fabric showed wide range of color including brown, brown-green, green at the different temperature. With the increase of K/S value, the coordinate of value(lightness) decreased for both of ramie and silk fabrics. The coordinate of hue(shade) changed drastically with the increase of K/S value for silk fabric, compared with that of ramie fabric which showed nearly constant value at the whole range of K/S value. Optimum concentrations of calcium hydroxide were for 6 g/L for ramie and 4 g/L for silk at $60^{\circ}C$ and 50 min. K/S value increased with the indigo concentration. Maximum K/S value was shown at $10{\sim}12$ g/L of glucose concentration. For both of ramie and silk fabrics, the colorfastness of washing and light was lower than that of rubbing. All the colorfastness values were improved with the increase of color strength.

• Horticultural Science & Technology
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• v.16 no.3
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• pp.350-351
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• 1998

This study was conducted to investigate the effect of reflective film(RF) mulching on the growth and flowering of snapdragon 'Fujinoyuki' in greenhouse cultivation. On the spectroradiometry of mulching materials in the wavelength zone of 300nm to 1100nm, 85% of total light source was reflected from RF, while over 95% was absorbed into black polyethylene film(BL). Under plant canopy, light, air temperature, and leaf temperature were higher on the RF mulching than BL, but soil temperature and soil heat flux were higher under the BL. Primary plant growth such as dry weight, stem hardness, lodging, and transpiration was superior when using RF mulching. RF mulching accelerated the plants to bloom about 12 days earlier with admirable cut flower quality.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.140-144
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• 2012

Compared with bulk material, quantum dots have received increasing attention due to their fascinating physical properties, including optical and electronic properties, which are due to the quantum confinement effect. Especially, Luminescent CdSe quantum dots have been highly investigated due to their tunable size-dependent photoluminescence across the visible spectrum. They are of great interest for technical applications such as light-emitting devices, lasers, and fluorescent labels. In particular, quantum dot-based light-emitting diodes emit high luminance. Quantum dots have very high luminescence properties because of their absorption coefficient and quantum efficiency, which are higher than those of typical dyes. CdSe quantum dots were synthesized as a function of the synthesis time and synthesis temperature. The photoluminescence properties were found strongly to depend on the reaction time and the temperature due to the core size changing. It was also observed that the photoluminescence intensity is decreased with the synthesis time due to the temperature dependence of the band gap. The wavelength of the synthesized quantum dots was about 550-700 nm and the intensity of the photoluminescence increased about 22~70%. After the CdSe quantum dots were synthesized, the particles were found to have grown until reaching a saturated concentration as time increased. Red shift occurred because of the particle growth. The microstructure and phase developments were measured by transmission electron microscopy (TEM) and X-ray diffractometry (XRD), respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.160-164
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• 2008

Insulating and conducting 12CaO ${\cdot}7Al_2O_3$ (Cl2A7)-doped indium tin oxide (ITO) (ITO:Cl2A7 insulator and electride) thin films were deposited on glass substrates by an RF magnetron co-sputtering method with increasing number of insulating and conducting Cl2A7 target chips. The structural, electrical and optical properties of these films were investigated. The carrier concentration decreased and resistivity increased in the films with increasing number of Cl2A7 target chips. The optical transmittance of all of the thin films was above 80 % in the visible wavelength range. The structural property and surface roughness of the films were examined and the decrease of crystallinity and surface roughness was strongly dependent on the change of grain size.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.425-430
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• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.473-479
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• 2012

The influences of scatterer and absorber in turbid material by light scattering were interpreted for the scattered intensity and wavelength. The molecular properties have been studied by Monte Carlo simulation in resin of New Austria Tunnel Method. It has been found that the effects of optical properties in scattering media could be investigated by the optical parameters(${\mu}_s$, ${\mu}_a$, ${\mu}_t$). Monte Carlo Simulation method for modelling of light transport in the civil engineering and construction field was applied. The results using a phantom were discussed that the distance from source to detector is closer, and scattering intensity is stronger with those obtained through Monte Carlo Simulation. It may also aid in designing the best model for coatings and corrosion for the durability of metal constructions.

• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.57-66
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• 2015

Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calculated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the generally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of $${\sim_\sim}$$ 1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of $r{\leq}0.5$ kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of $1{\leq}r{\leq}2kpc$. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.49.1-49.1
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• 2017

Comets are one of the most primordial solar system objects that hold the information of the early days of solar system formation inside their nuclei. Orbiting the Sun, they spew such ancient materials that have been buried for many years, creating dust and gas comae. Cometary dust grains absorb and scatter sunlight radiating the continuous light, while gas molecules form the line emissions. Eachof the comets has its own light patterns, which depends on the physical and chemical properties of the dust and gas components. In this regard, spectropolarimetrycan be a powerful tool to study the properties of cometary constituents free from contamination of each other. This methodology offers a series of information on the polarization degrees of the dust and gas components as well as on wavelength dependence of the polarization degree and polarization angle of cometary dust simultaneously. Herein, we will report the results of the spectropolarimetric study of comet 2P/Encke, which is one of the well-known objects for its shortest orbital period and its prominent aging signals. We performed a spectropolarimetric observation of comet 2P/Encke in its inbound orbit using the Higashi-Hiroshima Optical and Near-Infrared Camera (HONIR) at the Higashi-Hiroshima Observatory, Japan, on UT 2017 February 21 at high phase angle of =75.7 deg. Ourstudy of this interesting comet is the first and only one done through spectropolarimetry in a referred publication. We will discuss the most recent polarimetric results of our study in terms of 2P/Encke' scurrent evolutionary status.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.2
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• pp.52-59
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• 1998

The ZnS:Mn thin film electroluminescent(TFEL) devices fabricated by ALE system were investigated. Yellow-orange light emission was observed when the applied voltage exceeded 134 V and luminance increased sharply as the applied voltage increased. Luminance of 568 Cd/c $m^{2}$ was obtained under 1 KHz sinusoidal voltage wave application at the peak applied voltage of 230 V. The peak wavelength of the emissionwas 577 nm. The C-V, Q-V, $Q_{t}$ - $F_{p}$ , L- $Q_{cond}$, and V- $Q_{pol}$ have been measured under theapplication of the trapezoidal wave with its pulse width varying 0 to 75 .mu.sec. The phoshor and the insulator capacitance of the TFEL device under test were 24.3 nF/c $m^{2}$ and 9 nF/c $m^{2}$, respectively. It was observed that the threshold voltage changed from 137V to 100V as the pulse width varied from 0 to 75 .mu.sec. The L- $Q_{cond}$ characteristics showed that the light emission increased in proportion to the $Q_{cond}$. The luminance increased from 386 Cd/ $m^{2}$ to 607 Cd/ $m^{2}$ when the $Q^{+}$$_{cond}$ increased from 1.3 .mu.C/c $m^{2}$ to 2.3 .mu.C/c $m^{2}$. The V- $Q_{pol}$ characteristics showed that the V was inversely proportional to $Q_{pol}$./. th/ was inversely proportional to $Q_{pol}$./. pol/./.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2279-2285
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• 2011

The geometries, electronic structures and absorption spectra of the two organic triphenylamine-based dyes TA-St-CA and TA-DM-CA, containing identical electron donors and acceptors but the different conjugated bridges, were studied by density functional theory (DFT) at the B3LYP and PBE1PBE levels, respectively. The influence of para-orientating methoxyl units on the electronic structures and light absorption properties of the dyes and the consequent photovoltaic performance of the dye-sensitized solar cells (DSSCs) were investigated in detail. The results indicate that the introduction of the para-orientating methoxyl units into the conjugated bridge induces the increased absorption wavelength as well as the more negative EHOMO corresponding to the bigger driving force $(E_{I^-/I^-_3}-E_{HOMO})$ for dye reduction, which together improve the photovoltaic performance of TA-DM-CA, although there is a decline of the open circuit voltage caused by the more negative $E_{LUMO}$.