• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.85.2-85.2
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• 2019

We developed a new grid-based Monte Carlo code to trace far UV He II line photons that are incident on a thick H I region and subsequently transferred through Rayleigh and Raman scattering with atomic hydrogen. In particular, we consider a neutral region that is moving away from the He II emission source which is either monochromatic or is described by a Gaussian profile. The resultant Raman scattered He II line profiles from a monochromatic source are characterized by a double peaked core part with an extended Raman red tail that is attributed to multiple re-entry events. Complicated behaviors are observed in the case of a Gaussian He II source including the formation of a secondary red peak near the Balmer center dependent on the H I column density. A preliminary application of our results to the CFHT data of the planetary nebula IC 5117 is presented.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.69.2-69.2
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• 2020

Korea Astronomy and Space Science Institute (KASI) is developing a coronagraph to measure the coronal electron density, temperature, and speed utilizing spectral change of the K-corona around 400 nm. However, near UV light is more affected by atmospheric effect on the ground than visible light. For the total solar eclipse on July 2 2019, KASI organized an expedition team to test the possibility of the similar measurement scheme in the visible light. The observation site was in Las Flores, San Juan, Argentina. We built an imaging spectrograph using micro lenslet array and grism, named Coronal Integral Field Spectrograph (CorIFS). In addition, images of white light corona, wide field background, and all sky were taken with various camera settings. We present the preliminary results of the expedition.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.69.4-70
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• 2020

Raman-scattered He II features are known to be present in several young planetary nebulae (PNe) including NGC 7027, NGC 6302, IC 5117 and NGC 6790. These features provide a new spectroscopic window to probe both thick neutral regions and far UV regions near Lyman series. We carry out photoionization model calculations using 'CLOUDY' to explore He II emission strengths dependent on the physical conditions of the central star. The emission nebula is treated as a simple spherical shell with uniform density. It is found that detectable Raman-scattered He II are obtained for T∗ ~ 105 K in the presence of a thick neutral component. We present mock spectra exhibiting Raman He II features based on the photoionization calculations and compare them with observed data. We discuss effective strategies for searching young PNe with Raman-scattered He II emissivities.

• KSBB Journal
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• v.10 no.1
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• pp.63-70
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• 1995

The effect of operating conditions on separation of soybean proteins in a home-made free-flow electrophoresis apparatus was investigated. Measurement of the pH, conductivity, and UV-absorbance(280 nm) were carried out at each run and the purity of the sample was tested with SDS-PAGE analysis. The soybean extract pretreated with Tris and boric acid was mixed with the amino acids composed of glutamic acid, histidine, arginine, glycine(1 mM each) with glycyl-glycine(2mM) and KCl(1mM). When the cellulose acetate was used as a compartment between the electrode and the buffer solution in the cell, pH distribution in the separation cell varied from 3.0 at the anodic side to 8.0 at the cathodic side and had two inflection point. The applied voltage was from 300V to 1000V and the separation was better at a higher voltage but the voltage was limited by the capability of the cooling system due to Joule heat. The proteins focused near the middle of the channel. From the change of pH and conductivity it was found that the ions in the channel moved out to the electrodes through the membrane. In the case when the concentration of the buffer solution was increased 5 times, proteins were focused at 300V. We could not increase up to the ten times of the concentration since the temperature difference between inlet and outlet was more than $25^{\circ}C$ and denaturation of proteins was expected. When ion-exchange membranes were used U-type pH distribution was set up due to the ionic polarization near the membrane. The commercial ampholytes, instead of the mixed amino acids showed not much improvements in purity of the separated sample.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.172-178
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• 1997

Polyaniline(PANI)-stearic acid(SA) composite monolayer was formed at the air-water interface. The stearic acid as a surfactant was used to promote PANI monolayer formation. Uniform PANI-SA monolayer assemblies with Y type and transfer ratio of ca. 1 were fabricated using the Langmuir-Blodgett(LB) technique. The PANI-SA composite LB films with high electrical conductivity of $10^{-1}{\sim}10^{-2}S/cm$ were obtained by doping of HCl or $I_2$, and their conductivity revealed essentially close value as that of conventional PAHI-HCl complex. Especially, iodine is found to be the most promising dopant, since it gives a remarkable stability for the application as a polymer electrode in the MIM molecular device consisted of acceptor, sensitizer, and donor. The structure and physical properties of PANI-SA LB films were investigated through the near-ir UV, FT-IR, and Cyclic voltammetry.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.101-112
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• 2015

II~VI compound semiconductors, $Zn_xCd_{1-x}S$ thin films have been synthesized onto indium-tin-oxide(ITO) coated glass substrates using thermal evaporation technique. The composition ratio x($0{\leq}x{\leq}1$) was varied to fabricate different kinds of $Zn_xCd_{1-x}S$ thin films including CdS(x=0) and ZnS(x=1) thin films. Then, the deposited thin films were thermally annealed at $400^{\circ}C$ to enhance their crystallinity. The chemical composition and electronic structure of films were investigated by using X-ray photoelectron spectroscopy(XPS). The optical energy gaps of the samples were determined by ultra violet-visible-near infrared(UV-Vis-NIR) spectroscopy and were found to vary in the range of 2.44 to 3.98 eV when x changes from 0 to 1. Finally, we measured the THz characteristics of the $Zn_xCd_{1-x}S$ thin films using THz-TDS(time domain spectroscopy) system to identify the capability for electronic and optical devices in THz region.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.181-186
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• 2016

The hydrophilic ophthalmic lens with addition of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA) and Ag nanoparticles were manufactured. And also, the cross-linker ethylene glycol dimethacrylate (EGDMA) and the initiator azobisisobutyronitrile (AIBN) were used for polymerization. The polymerization of the hydrogel lens material was conducted through thermal polymerization in 100 ℃ for 1h. The optical and physical characteristics of hydrogel lens were evaluated by measuring water content, refractive index and optical transmittance. The water content of sample containing HEA, HEMA and HPMA was in the average of 82.12%, 37.06% and 21.57%, respectively. And also, refractive index of the sample containing HEA, HEMA and HPMA was in the average of 1.3540, 1.4330 and 1.4649, respectively. In case of the optical properties of the sample, the results showed that the near-UV transmittance was 82.67%, 80.32% and 79.83%, and the visible transmittance was 89.72%, 88.24% and 86.89%, respectively. And also, optical transmittance of the sample containing Ag nanoparticles showed that the near-UV transmittance of 10.59% and visible transmittance of 43.74% were obtained. From the results, the molecular length influenced on the water content and refractive index of the polymerized material.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1497-1503
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• 2023

To address challenges in classifying clouds and snow cover when calculating ground reflectance in Near-UltraViolet (UV) wavelengths, this study introduces a methodology that combines cloud data from the Geostationary Environmental Monitoring Spectrometer (GEMS) and the Advanced Meteorological Imager (AMI)satellites for snow cover analysis. The proposed approach aims to enhance the quality of surface reflectance calculations, and combined cloud data were generated by integrating GEMS cloud data with AMI cloud detection data. When applied to compute GEMS surface reflectance, this fusion approach significantly mitigated underestimation issues compared to using only GEMS cloud data in snow-covered regions, resulting in an approximately 17% improvement across the entire observational area. The findings of this study highlight the potential to address persistent underestimation challenges in snow areas by employing fused cloud data, consequently enhancing the accuracy of other Level-2 products based on improved surface reflectivity.

• Advances in materials Research
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• v.3 no.4
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• pp.227-232
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• 2014

$Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor was synthesized via solid state reaction method using $CaF_2$, $CaCO_3$ and $SiO_2$ as raw materials for the host and $Eu_2O_3$, $CeO_2$, and $Tb_4O_7$ as activators. The luminescent properties of the phosphor was analysed by spectrofluorophotometer at room temperature. The effect of excitation wavelengths on the luminescent properties of the phosphor i.e. under near-ultraviolet (nUV) and visible excitations was investigated. The emission peaks of $Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor lays at 480(blue band), 550(green band) and 611nm (red band) under 380nm excitation wavelength, attributed to the $Ce^{4+}$ ion, $Tb^{3+}$ ion and $Eu^{3+}$ ions respectively. The results reveal that the phosphor emits white light upon nUV (380nm) / visible (465nm) illumination, and a red light upon 395nm / 535nm illumination. RE ions doped $Ca_3Si_3O_8F_2$ is a promising white light phosphor for LEDs. The emission colours can be seen using Commission international de l'eclairage (CIE) co-ordinates. A single host phosphor emitting different colours under different excitations indicates that it is a potential phosphor having applications in many fields.

• Journal of the Korean Chemical Society
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• v.50 no.6
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• pp.440-446
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• 2006

ZnO nanoparticles were prepared by laser ablation of the ZnO powder dispersed in deionized water and surfactant solutions, and characterized using UV-VIS absorption spectroscopy, X-ray diffractometer and Transmission electron microscopy(TEM). ZnO nanoparticles produced show the pure ZnO crystal state without mixed state with Zn(OH)2 or Zn, and have the band gap energy of 3.35 eV, which is comparable to that of bulk ZnO. While ZnO nanoparticles prepared in SDS solution have the average diameter of 28nm with near spherical shape, those prepared in CTAB solution have the average size of 40 nm with mainly rod-like shape. ZnO colloidal solution of CTAB is more stable than that of SDS. These difference according to surfactants can be explained by difference of electrostatic interaction between surface charge of ZnO and surfactant molecules and by solvation effect in solution.