• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.407-412
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• 2015

A preconcentration procedure for determination of palladium by laser thermal lens spectrometry (TLS) is proposed. It is based on cloud point extraction of palladium(II) ions as 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminoaniline (3,5-diCl-PADMA) complexes using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The effects of various experimental conditions such as pH, concentration of ligand and surfactant, equilibration temperature and time on cloud point extraction were studied. Under the optimized conditions, the calibration graph was linear in the range of 0.15~6 ng mL⁻¹, and the detection limit was 0.04 ng mL⁻¹ with an enrichment factor of 22. The sensitivity was enhanced by 846 times when compared with the conventional spectrophotometric method. The recovery of palladium was in the range of 96.6%~104.0%. The proposed method was applied to the determination of palladium in water samples.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.2
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• pp.13-18
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• 1996

In this study, contact lens care solutions were compared to each other for cytotoxic effect on cultured mouse fibroblasts by the use of neutral red(NR) assay. This study tested the cytotoxicity of 12 cleaning solutions, 2 lubricants and 5 multipurpose solutions(MPS) at 1%, 2%, 3% and 5% concentrations. These solutions are manufactured in Korea and foreign countries. The relative cytotoxic comparison of these solutions showed that some of them are toxic, three of the cleaning solutions were especially highly toxic 10 cells, so most fibroblasts were dead at 1% concentration. The toxic cleaning solutions have more components than other solutions. But both lubricants and MPSs are non-cytotoxic 10 cells. Some of these solutions did not have any descriptions or indications. They are very dangerous to eyes. From this study, contact lens care solutions should be tested for cytotoxic effects.

• Journal of Korean Biological Nursing Science
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• v.21 no.1
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• pp.12-21
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• 2019

Purpose: The purpose of this study was to review previous literature with an aim to explore the sleep disturbance level after a patient undergoes cataract surgery using an integrative review. Methods: We used the key words, 'cataract surgery', 'sleep', and 'intraocular lens' to find peer-reviewed publications in seven databases. Among 450 searched articles, eight articles were selected after exclusion of articles that did not meet the criteria. Results: Five of the articles submitted that subjective sleep quality of the patients with blue-filtering intraocular lens (BF-IOL) implant improved as compared to that before surgery. The change of saliva melatonin concentration after BF-IOL implant did not coincide in two of the articles. Two of the articles reported an increased level of intrinsically photosensitive retinal ganglion cells response after BF-IOL implantation. Conclusion: The published studies stated that BF-IOL implant did not have any negative impact on quality of sleep among cataract patients suffering with poor sleep. Rregardless of intraocular lens type, cataract surgery may increase photoreception of intrinsically photosensitive retinal ganglion cells one year after surgery although the mechanism was not clear. It is necessary to identify various factors influencing the quality of sleep such as gender and activities among cataract patients with BF-IOL implant in the future.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.96-101
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• 2012

An experimental study was conducted to investigate the performance of a concentrating photovoltaic cell (CPV) against temperature. It is know that a high efficiency of a CPV can be achieved only with proper cell temperature as well as high concentration ratio (CR). This study is concerned with appropriate cooling condition for a liquid-convection cooler for the best performance of a specific CPV. A series of experiments was conducted in a range of cell temperatures as a result of varying cooling conditions, while the concentration ratio was 390 and the solar irradiation flux was higher than 900 $W/m^2$ in outdoor environment. The CPV had a planar dimension of 10 by 10 mm. A Fresnel lens was used as a concentrator, of which the dimension was 221 mm(W) ${\times}$ 221 mm(L) ${\times}$ 3 mm(t) and the transmissivity was known to be 0.8. The cooler was attached to the bottom side of the CPV and had a contact area of 21 mm(W) ${\times}$ 26 mm(L), which was identical to the size of the base plate of the CPV. The coolant temperature was controlled by an isothermal bath and the flow rate was controlled and measured by a flowmeter. The experimental results showed that the average of power efficiency of the CPV decreased from 28.6 % to 24.7 % as the cell temperature increased from $36^{\circ}C$ to $97^{\circ}C$. An appropriate cooling method of a CPV might increase the power conversion efficiency by about 4% for the same concentration ratio. Discussion is included from the viewpoint of the combined efficiency in addition to the power efficiency.

• Journal of the Korea Convergence Society
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• v.12 no.7
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• pp.125-131
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• 2021

Blue light with strong energy is required for light-curing resin treatment, which is being used more frequently in dentistry. To reduce the risk of exposure to scattered light, we tried to use colored lenses. The tips for light curing machine and a commercially available yellow-type blue-light blocking lens and a yellow lens colored with yellow dye, which are expected to be effective in blocking blue light, were placed in a UV-Vis spectrometer device, and transmission and blocking of blue light were tested respectively. As a result, the average blue light blocking rate of the light curing machine tips was 99.49%, and the C lens with the highest color density among commercially available lenses showed a high blue light blocking rate of 99.54%. In the case of lenses tinted with yellow, the yellow tinted C lens with the highest tint concentration showed 87.57% of blue light blocking rate. It is judged that the side effects related to the eyes caused by blue light can be reduced if a yellow-type commercially available or colored lens is worn along with a light curing machine tip during resin treatment.

• Journal of the Korea Convergence Society
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• v.12 no.7
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• pp.61-67
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• 2021

The purpose of this study was to investigate the colors of spectacle lenses that would be effective in blocking blue light among various colors so that the damage caused by blue light could be conveniently reduced even in daily life and when filling with dental light-curing resin. Each color dye of orange, brown, gray, yellow, red, and rosa was dissolved in an individual container of a spectacle lens tinting machine, and 6 uncolored spectacle lenses were immersed in a temperature of 90℃ for 1 hour to color. As a result of comparing the blue light transmittance of the colored spectacle lens and the tip for the photopolymerizer, the blue light transmittance of the orange colored lens was 0.82%, and the blue light blocking effssect was the best. Brown and gray tinted lenses had excellent blue light blocking rate, but it was difficult to recognize objects through the lens due to the high tinted concentration, and yellow tinted lenses were found to be effective when the tint was similar to the tip. The blue tinted lens had a blue light transmittance of 15.10%, which was lower than other tinted lenses. The results of the experimental study are expected to be helpful in recognizing the blue light transmittance by spectacle tinted lenses of various colors and making efforts to select the appropriate blue light blocking lens color and block harmful blue light stimuli.

• Journal of Biomedical Engineering Research
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• v.9 no.1
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• pp.67-72
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• 1988

Poly (HPMA/NVP) hydrogel was synthesized according to the composition and the con- centration of the crosslinking agent. The swelling degree of the P(HPMA/NVP) hydrogel decreased with increasing of P(HPMA) composition and crosslinking agent. The glass transi- tion and softening temperatures of the P(HPMA/NVP) increased with increasing of P(HPMA) composition. The composition of P(HPMA/NVP) : 70/30 and the concentration of the crosslin- king agent of 0.5 wt % gave the optimum condition in the application to the contact lens. There were also adequate in the mechanical, refractive properties and in vivo test in the P(HPMA/ NVP): 70/30 system.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.63-67
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• 2015

White light-emitting diode (WLED) is growing interest in using both illumination and communications. This paper reports visible light communication (VLC) composed of a super bright white light-emitting diode, low cost commercial photo-diode and a Fresnel lens. LED driver is consisted of the power MOSFET and MOSFET driver that switches the LED on and off. The modulation bandwidth of the LED used was determined to be 8 MHz. However, it was possible to communicate up to 1 Mbps under illumination of 500 lx because of the weak signal power and a low spectral sensitivity of the SHF213 as a PIN photodiode. In order to enhance the system bandwidth, the LED light was focused on the PIN photodiode by use of the Fresnel lens. As a result of that, visible light link was operated up to modulation bandwidth of the LED. The signal to noise ratio can be improved by 40 dB using an optical concentration at the receiver.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.213-216
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• 2013

This paper presents a combination of linear Fresnel lenses optimized for ${\times}25$ solar concentration. The combined lens consists of $5{\times}5$ linear Fresnel lenses. Each Fresnel lens is of $10{\times}10$ mm and optimized to tilt the incoming light onto a solar cell of the same size. All of the optimized Fresnel segments have the same pattern height of 35 ${\mu}m$, draft angle of $4^{\circ}$, and edge groove round of 1 ${\mu}m$ but with different facet angles varying from $14.1^{\circ}$ to $31.2^{\circ}$. The solar concentrating efficiency of the combination is shown to be over 80% and more robust than a conventional single ${\times}25$ circular Fresnel lens in terms of pointing misalignment and manufacturing errors. A sensitivity analysis finds that the edge groove round should be kept as small as machining allows since the concentrating efficiency drops ~5% per 1 ${\mu}m$ increase of the edge groove.

• Journal of Information Technology Applications and Management
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• v.16 no.4
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• pp.59-77
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• 2009

Microblog services are such new communication channels with some considerable potential to improve information sharing. The idea of sharing short messages using multiple access points seems to be appealing to people worldwide. Through the lens of flow and social identity, we explored factors that influence information sharing behaviors in microblog services. With an empirical study, we examined enjoyment and concentration(flow) and self-presentation(social identity) in microblog services like twitter can contribute to the user behaviors. Our aim was to gain insight into ways of creating an environment that facilitating voluntary sharing of information. Our findings suggested that enjoyment, concentration, and selfpresentation were crucial determinants of information sharing behaviors in microblog services. This study has important implications for academic researchers and practitioners who seek to understand why microblog service users share their information with other members in microblog services.