• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.749-754
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• 2009

HEMA (2-hydroxyethyl methacrylate) is a hydrophilic material which is broadly used for ophthalmologic purposes and especially in the manufacture of soft contact lenses. Also, the oxygen transmissibility (Dk/t) is a very important physical characteristic in the evaluation of a material’s adequacy to be used to produce contact lenses. This study used HEMA (2-hydroxyethyl methacrylate), MMA (methylmethacrylate), NVP (Nvinyl-pyrrolidone), the cross-linker EGDMA (ethylene glycol dimethacrylate) for copolymerization, and measured the oxygen transmissibility of the central and peripheral areas of the manufactured general and color contact lenses using the polarographic method. The measurement showed that the decreased amount of oxygen transmissibility of the central and peripheral areas of the contact lenses measured using the polarographic method range between 40.77% and 49.13%, and the oxygen transmissibility of the color contact lens showed a larger decrease due to the effects of the coloring materials.

• Korean Journal of Breeding Science
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• v.40 no.1
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• pp.15-21
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• 2008

It was previously pointed out that mutation is the ultimate source of variation. Adequate variation is needed for plant breeding if there is a limitation in natural genetic resources. When the ionizing radiation has been known to cause chromosomal and genomic alternations, it is widely used for inducing mutagenesis. The electron beam as an ionizing radiation is the principal physical mutagens that induces mutation and effectively used in plant breeding. Since dose-response relationships of electron beam in plant species are rarely known, we investigated the seed germination rate and early seedling growth of irradiated seeds of creeping bentgrass (Agrostis palustris Huds., cv Penn-A1) with various electron beam irradiating conditions (1, 1.3, 2 MeV at both 0.03 mA and 0.06 mA with dose of 100 Gy (Gray) and 0.03, 1, 1.3, 2 MeV at 0.03 mA with dose of 200 Gy, respectively) using electron accelerator at Korea Atomic Energy Research Institute. The growth parameters in terms of shoot length, primary root length, and secondary root length showed similar response between 0.06 / 1 (mA / MeV) at 100 Gy and 0.03 / 0.3 (mA / MeV) at 200 Gy. Bentgrass seed germination was mainly affected by the intensity of irradiated dose (Gray). Germination rate was lowered as the irradiated dose increased. On the other hand, early seedling growth was mainly governed not by the dose of radiation but by voltage.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.715-726
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• 2018

Various methods, such as geophysical exploration, temperature measurement, and fiber optics, have been developed for detecting the seepage at a dam. In this study, in order to investigate the possibility of leakage detection using dielectric constant of FDR sensor, a physical model consisting of weak and no-weak zones is fabricated and the sensors for dielectric constant, temperature and pore water pressure measurements are installed. As a leakage happens, the dielectric constant changes more rapidly through a weak zone than no-weak zone. In addition, comparing three factors (dielectric constant, temperature, and pore water pressure), the response of dielectric constant to seepage is fast and it is easily recognized even at the end measurement point. Considering these features, it is concluded that it could be possible to cope with the leakage detection quickly and efficiently if the dielectric constant is measured at the downstream slope of a dam.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.1
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• pp.27-34
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• 2005

Photochromic lens is the color changing lens from colorlessness to colorness when exposed to UV light. It can protect eyes from UV-B light which cause the cataract and can be used as sunglass in the summer since it can cut off 70~80% of sun light. Surface coating technique was used to develop lens which has 70% light transmittance and of which fading time of color change is within 5 min. Various color lenses were developed so that these had various color such as blue, green, brown, violet, yellow and red etc. Lens has an excellent physical properties, 100% adhesion and 4~5H hardness. The chemical and the scratch resistance of this lens were the greatest and the thermal stability was also higher. The clinical trial of developed lens were applied to 65 patients who had photophobia by various reasons at ophthalmology of Soonchunhyang University Hospital. Results showed that glaring was significantly reduced and the visual health were remarkably improved. Especially, anti-glaring effect in the night was great for the patient who had the LASIK operation. Protection of UV-B and blue light also can prevent the patient from cataract and the yellowish crystalline lens at old ages. Through the result of clinical. trial, we know that photochromic lens could be a new technique for both cure and precaution of photophobia.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.98-103
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• 2011

This study was done for the preparation of macromolecular material with UV-blocking features by adding the benzophenone group that is commonly used as a UV-absorbent and $TiO_2$ which is known to be a very stable material in chemical and physical aspects. Also, we compared the level of UV absorbency of the polymer produced from polymerization with previous materials and measured basic properties such as water content, refractive index and optical transmittance of produced contact lenses. The results of the measurement showed that the refractive index and water content of the contact lens with added UV-absorbent was 1.430~1.440 and 35.0~45.0% respectively, which was similar to that of previous contact lenses. Also, for optical transmittances of each wave length, contact lenses without the UV-absorbent was 89%, 88% and 89% respectively for UV-A, UV-B and visible light, indicating that the UV transmittance is very high though contrary with cases of contact lenses with added 2-hydroxy-4-methoxy-benzophenone and 2,4-dihydroxy-benzophenone which showed transmittances of 0% and 6% respectively for UV-A and UV-B showing a UV-blocking effect. Meanwhile, contact lenses with added $TiO_2$ showed transmittance of 6% and 51% respectively for UV-A and UV-B also showing a UV-blocking effect. The visible transmittance was 77~89% showing that it satisfies the visible transmittance required for ophthalmological materials.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.45-50
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• 2008

Purpose: A soft contact lens was manufactured by adding naringin known as natural anti-bacterial material to resin solution. With solution eluted from manufactured contact lens, we examined its optical properties, physical and chemical states of naringin in the polymer, and elution properties. Methods: The soft contact lens with naringin was synthesized by bulk polymerization method. IR spectrum and HPLC were used to define the bonding type of naringin itself in the soft contact lens contained naringin, elution process of naringin to the saline solution, and the amount of naringin solution eluted from the lens with elapsed time. Results: Naringin was continuously eluted with constant concentration from the soft contact lens for about a month and the structure ofnaringin which is eluted was as same as before it was added to resin solution. Any change in optical properties such as transmittance couldn't be found. Bonding state and the structure of naringin in contact lens were explained with IR spectrum and HPLC results. Conclusions: In the contact lens with naringin, naringin remained in the contact lens bonding with weak hydrogen bonding and/or van der Waals force between naringin and polymer. Naringin was continuously eluted from the contact lens contained naringin during about 1 month. Even after 1 month, it showed that the concentration of the naringin eluted was approximately 10 ppm in a day. From the results, adding naringin to the soft contact lens resin is very effective method for manufacturing the soft contact lens which has anti-bacterial function for a period of time.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.145-151
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• 2014

Purpose: The material properties of contact lenses were measured by varying the amounts of an initiator and a cross-linking agent that are the basis for the manufacture of contact lenses, and the drug delivery effects depending on the material properties of contact lenses were compared. Methods: Contact lens samples were manufactured using HEMA by varying the concentration of the cross-linking agent and the initiator. To investigate the changes in physical characteristics depending on the material properties, the results of the experiments on the amount of drug elution, water content, refractive index, and the amount of protein adsorption were compared. Results: For the contact lenses manufactured by varying the amount of the initiator, the water content hardly changed, and the refractive index also hardly changed. The amount of drug elution was not much affected by the changes in the initiator, but the amount of elution increased as the water content increased. The amount of protein adsorption was hardly affected by the changes in the initiator, but the amount of adsorption increased as the water content decreased. Conclusions: The changes in the properties were hardly affected by the changes in the amount of the initiator, but were significantly affected by the changes in the amount of the cross-linking agent. As the amount of the cross-linking agent increased, the water content decreased, while the refractive index increased. Also, when the water content increased, the amount of drug elution increased, while the amount of protein adsorption decreased.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.285-291
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• 2015

Purpose: The hydrogel lenses have been functionalized with HA(Hyaluronic Acid) using two different methods: construction of an IPN(Interpenetrating Polymer Networks) and formation of CCB(Chemical Covalent Bonding). The lysozyme adsorption and physical properties such as optical transmittance and water content of the hydrogel lenses have been investigated in order to determine whether method is suitable for the application potentials in contact lens industry. Methods: HA have been added to the hydrogel lenses prepared in the Lab using the two different method, e.g. IPN and CCB. The optical transmittance was measured in the wavelength range of 300~800 nm. The water content was measured by the gravimetric method using 0.9% NaCl saline solution. The amounts of adsorbed lysozyme on the contact lenses was analyzed by HPLC after incubation for 12h in artificial tears. Results: The water content of the HA added hydrogel contact lenses was increased, and the lens made by IPN method showed higher water content than the lens made by CCB method. The optical transmittance was over 90% both before and after addition of HA. Comparing the lysozyme adsorption reduction ratio, contact lens manufactured by IPN method was 60.0%, and the lens made by CCB method was 40.4%. Conclusions: CCB method is appropriate to distribute the functional material evenly throughout the lens, whereas IPN method is effective for the case of giving the functionality on the lens surface without phase separation.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.158-165
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• 2017

The physical shape of an ultrasound transducer has not been considered in previous studies of the photoacoustic saturation effect, where a photoacoustic signal's magnitude linearly increases as an absorption coefficient increases and it is finally saturated. In this paper, the effect of a spherically focused ultrasound transducer on photoacoustic nonlinearity is investigated. The focused ultrasound transducer's spatial filtering effect on photoacoustic signals is analytically derived considering the combined concept of a virtual point detector and Green function approach. The ultrasound transducer's temporal response (i.e., transfer function) effect on photoacoustic signals is considered by integrating photoacoustic signal values within the absorption area covered by a spatial resolution of the ultrasound transducer. Results from the analytically derived expression show that the magnitude of photoacoustic signals measured by a spherical focused ultrasound transducer shows a maximum at a specific absorption coefficient, and decreases after that maximum point as an absorption coefficient is increased. The origin of this photoacoustic nonlinearity is physically understood by comparing the ultrasound transducer's transfer functions and photoacoustic resonance spectra. In addition, this physical interpretation implies that the photoacoustic nonlinearity is strongly dependent on the irradiance distribution inside an absorption medium.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.307-313
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• 2022

As the development of renewable energy expands internationally to cope with global warming and climate change, the share of wind power generation has been gradually increasing. Although wind farms can produce electric power for 24 h a day compared to solar power plants, Their interfere with the operation of nearby radars or communication equipment must be analyzed because large-scale wind power turbines are installed. This study analyzed whether a land radio station can receive sufficient signals when a ship sailing outside the offshore wind farm transmits distress signals on the VHF band. Based on the geographic information system digital map around the target area, wind turbine CAD model, and wind farm layout, the area of interest and wind farm were modeled to enable numerical analysis. Among the high frequency analysis techniques suitable for radio wave analysis in a wide area, a dedicated program applying physical optics (PO) and shooting and bouncing ray (SBR) techniques were used. Consequently, the land radio station could receive the electromagnetic field above the threshold of the VHF receiver when a ship outside the offshore wind farm transmitted a distress communication signal. When the line of sight between the ships and the land station are completely blocked, the strength of the received field decreases, but it is still above the threshold. Hence, although a wind farm is a huge complex, a land station can receive the electromagnetic field from the ship's VHF transmitter because the wave length of the VHF band is sufficiently long to have effects such as diffraction or reflection.