• KSTLE International Journal
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• v.8 no.1
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• pp.1-6
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• 2007

Chromatic device was developed using light emitting diodes, optic fibers and photodiodes. Chromatic ratio and total contamination parameters based on transmitted light intensity in Red, Green, and Blue wavelengths were used for oil chemical and particulate contamination assessment. Chromatic ratio criterion was found independent of the particulate contamination of oil; but depended on chemical degradation, being more sensitive for synthetic than mineral hydraulic oil. Total contamination index of the sensor depended on both the chemical degradation and particulate contamination of the oil; being most sensitive in blue wavelength, and least in the red. Test results for synthetic hydraulic oils monitored corroborated with results of other tests such as viscosity, total acid number, elemental optical emission spectroscopy, particulate counts and UV-VIS photospectrometry. Chromatic ratio showed a clearer indication of oil degradation, compared to key monitoring parameters such as total acid number, viscosity and particle counts. The results showed that these parameters are effective criteria for the condition monitoring of synthetic hydraulic oils.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.93-100
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• 2005

8 functionality photocurable polyester polyol modified hyperbranched methacrylates of two types were prepared from trimellitic anhydride, glycidyl methacrylate, and 4 functionality polyester polyol of two types. The physical properties of photocurable polyester polyol modified hyperbranched methacrylate were investigated. Thermal stability obtained by using TGA showed that HBMA-2 (hyperbranched methacrylate-2) was superior to the HBMA-1 (hyperbranched methacrylate-1). Hardness, abrasion resistance and tensile strength of HBMA-2 showed that were also superior to the HBMA-1. Value of yellow index of HBMA-2 showed the higher.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.56.1-56.1
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• 2018

Tidal disruption events (TDEs) provide evidence for quiescent supermassive black holes (SMBHs) in the centers of inactive galaxies. TDEs occur when a star on a parabolic orbit approaches close enough to a SMBH to be disrupted by the tidal force of the SMBH. The subsequent super-Eddington accretion of stellar debris falling back to the SMBH produces a characteristic flare lasting several months. The theoretically expected bolometric light curve decays with time as proportional to $t^{-5/3}$. However, the light curves observed in most of the optical-UV TDEs deviate from the $t^{-5/3}$ decay rate especially at early time, while the light curves of some soft-X-ray TDEs are overall in good agreement with the $t^{-5/3}$ law. Therefore, it is required to construct the theoretical model for explaining these light curve variations consistently. In this paper, we revisit the mass fallback rates analytically and semi-analytically by taking account of the structure of the star, which is simply modeled by the polytrope. We find the relation between a polytropic index and the power law index of the mass fallback rate. We also discuss whether and how the decay curves, which we derived, fit the observed ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.808-811
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• 2008

Optical and mechanical properties of diamond-like carbon (DLC) films synthesized by RF plasma enhanced chemical vapor deposition were investigated as a function the C/H ratio in gas mixture. The C/H ratio was varied from 6 to 10 %, adjusting the amount of $CH_4$ and $H_2$ as the source gas. The optical and mechanical properties of DLC films were characterized by UV spectrometer, Ellipsometer and Nano-indenter. The change of the C/H ratio during synthesis of DLC films had many effects on the growth rate, transmittance, refractive index and hardness. The growth rate of the films increased exponentially with the increase in C/H ratio. The hardness of the films showed the tendency to improve with increasing C/H ratio, whereas the transmittance decreased. The refractive index was varied from 2.03 to 2.17, and these refractive indexes close to 2.0 indicates that it can be applied to Si-based solar cell.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.991-994
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• 2007

In this paper, we have designed the anti-reflection(AR) coating for $1400{\sim}1600$ nm wavelength range on the ferrule facet of optical connector. The low-temperature ion-assisted deposition was applied to AR coating on the ferrule facet in order to avoid damage of optical connector. We have measured the refractive index of coating film($Ta_2O_5\;and\;SiO_2$) using the ellipsometer and optimized the film thickness using the SEM and thickness measurement equipment. UV-VIS-NIR spectrophotometer is used to measure transmissivity of the AR coated ferrule facet. The refractive index of $Ta_2O_5\;and\;SiO_2$ is $2.123{\sim}2.125$ and $1.44{\sim}1.442$, respectively, for $1400{\sim}1600$ nm wavelength range. The transmissivity of the AR coated ferule facet is more than 99.8 % for $1425{\sim}1575$ nm wavelength range and more than 99.5 % for $1400{\sim}1600$ nm wavelength range. The return loss of the AR coated ferrule facet is 30.1 dB.

• Journal of Integrative Natural Science
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• v.17 no.3
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• pp.67-73
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• 2024

Hydrophilic contact lens was prepared by dispersing MXene material in a hydrogel mixture, and the purpose of this study was to evaluate its properties as an ophthalmic material. The MXene used in the experiment was manufactured through an etching process using titanium aluminum carbide 312 [Ti3AlC2] and hydrofluoric acid [HF]. For the preparation of hydrophilic contact lenses, 2-hydroxyethyl methacrylate [HEMA], a photoinitiator 2-hydroxy-2-methylpropiophenone [2H2M], and a cross-linker Ethylene glycol dimethacrylate [EGDMA] were used, and UV-rays was irradiated for 50 seconds for photopolymerization. Optical transmittance, refractive index, water content, contact angle, electromagnetic wave shielding ability, and photo-thermal conversion effect were measured to evaluate the physical properties of the manufactured contact lens. Compared to MXene materials, MXene mixed with Dimethyl sulfoxide [DMSO] had superior dispersion ability in organic solvents, and the transparency of the prepared hydrophilic contact lenses was high. MXene did not significantly affect the refractive index and water content, and improved the wettability of the contact lens. In addition, the MXene material used as an additive showed electromagnetic wave shielding ability and photo-thermal conversion effect based on its excellent electrical conductivity. It is judged that the mixture using MXene as an additive can be used as a functional contact lens material for electromagnetic wave shielding and ocular photo-thermal therapy.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Journal of the Korean Society of Fashion and Beauty
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• v.3 no.2 s.2
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• pp.18-24
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• 2005

The result of the study for essential oil(Bergamot, Grapefruit essential oil)'s Anaiysis of Blood Serum Epidermis proteins by exposure of nature lays on treatments are as follows. 1. There is no significant difference between control group and the groups treated by essential oil in feed efficiency, but in water intake, there are significant differences between each group. Water intake of the groups treated by Bergamot and Grapefruit essential oil without treatment by sun cream is higher than that of any other group. It is presented that the effect of losing water of the surface of skin is related to the balance effect of water. 2. As a result of serum analysis without applied UV-rays, the total cholesterol in the groups treated by Bergamot essential oil is higher than that of the groups treated by Grapefruit essential oil. It is showed that the dissolution of cellulite of Grapefruit essential oil is stronger than that of Bergamot essential oil. After applied UV-rays, however, the change of total cholesterol of the groups treated by Bergamot essential oil is lower than that of the groups treated by Grapefruit essential oil, namely, the group treated by Bergamot essential oil drops is used to make sebum membrane on the surface of skin, so the quantity of influx into blood vessel was low. With the result that, atherosclerotic index(A.I) also was low in the group treated by Grapefruit essential oil. In the aspect of increasing cholesterol for obesity treatment, it was judged that the effect of treatment with Bergamot essential oil is somewhat slower than that with Grapefruit essential oil, but it is safer than the effect of treatment with Grapefruit essential oil in the aspect of health. 3. As a result of protein analysis, the groups applied UV-rays in the group of treated by Bergamot essential oil, the biggest change of protein's band was appeared under part of 20.0 1Kd in the change pattern of protein. As the trend of changing protein at the groups treated by SPF 15 and 30 was similar to that of the groups of the control, it was showed that the effect of sun cream can prevent the change of the composition of skin. In the groups treated by Grapefruit essential oil, after the groups treated by Grapefruit essential oil applied UV-rays, the biggest change of protein's bend was appeared the upper part of 43Kd in the change pattern of protein. It was also judged that it means the change of the composition of skin. However, the trend of changing protein at the groups treated by SPF 15 and 30 was also similar to that of the groups of the control. Eventually, it was also showed that it can prevent the change of the composition of skin by the effect of sun cream.

• Korean Journal of Optics and Photonics
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• v.34 no.4
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• pp.157-169
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• 2023

Augmented reality (AR) using a head mounted display (HMD) is used in various fields such as military, medicine, manufacturing, gaming, and education. In this paper, we discuss the design and fabrication of the AR optical system, which is most essential for HMD. The AR optical system for HMD requires a wide transparent area in which the augmented image of the display and the real world can be viewed at the same time. To this end, an AR optical system was designed and manufactured by dividing it into three parts according to each characteristic. Also, the refractive index of the ultra-violet (UV) adhesive layer required to make the three optical systems into one complete AR optical system was considered from the design stage to minimize the optical path shift phenomenon when the input light source passes through the UV adhesive layer. In addition, when designing the AR optical system, two aspheric surfaces were used to compensate for off-axis aberration and to be suitable for mass production. Finally, for HMD mass production, an aspheric AR optical system with a thickness of 11 mm, a diagonal field of view of 40°, and a weight of 11.3 g was designed and manufactured.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.299-311
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• 2015

We report first results from KVN and VERA Array (KaVA) VLBI observations obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN) project. We observed eight selected AGN at 22 and 43 GHz in single polarization (LCP) between March 2014 and April 2015. Each source was observed for 6 to 8 hours per observing run to maximize the uv coverage. We obtained a total of 15 deep high-resolution images permitting the identification of individual circular Gaussian jet components and three spectral index maps of BL Lac, 3C 111 and 3C 345 from simultaneous dual-frequency observations. The spectral index maps show trends in agreement with general expectations – flat core and steep jets – while the actual value of the spectral index for jets shows indications for a dependence on AGN type. We analyzed the kinematics of jet components of BL Lac and 3C 111, detecting superluminal proper motions with maximum apparent speeds of about 5c. This constrains the lower limits of the intrinsic component velocities to ~ 0.98c and the upper limits of the angle between jet and line of sight to ~20°. In agreement with global jet expansion, jet components show systematically larger diameters d at larger core distances r, following the global relation d ≈ 0.2r, albeit within substantial scatter.