• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.85-92
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• 1993

Oxynitride glasses in Na-Ca-Si-O-N system were prepared by melting at 135$0^{\circ}C$ for 2 hours in N2 gas. The effects of Si/Na mole ratio and the various Si3N4 contents were investigated. Stable oxynitride glasses can be obtained up to 9wt.% Si3N4 content in case the Si/Na mole ratio was 2.12 and 1.62, but $\beta$-Si3N4 was precipitated at 9wt.% Si3N4 content in case the Si/Na mole rtio was 1.12. Density (p), chemical durability, hardness (Hv), and fracture toughness (KIC) increased with increasing Si3N4 content. In cae the Si/Na mole ratio was 1.12, the increment of properties was remarkable but hardness and fracture toughness did not increase no longer owing to precipitation of $\beta$-Si3N4.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.763-768
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• 1990

The gradient and depth of tin at the side of glasses by float process were measured. The effects of tin to ion exchanged of glasses in the molten salt of KNO3 and AgNO3 were presented by means of Ag+ ion penetration depth, diffusion coefficient variation, spectral transmittance and color coordinates. The diffusion coefficient of Ag+ ion of tin side was higher than air side, and the activation energy of tin side was 0.2-0.6Kcal/mole lower than air side. Therefore Ag+ ion penetration depth of tin side is 2-10$\mu\textrm{m}$ deeper, hence it can be seen that tin promote Ag+ ion diffusion. The same treatment of ion exchange, reddish-brown oflong wavelength in case of tin present, yellowish-amber of short wavelength in case of tin absence were revealed.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.9-16
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• 1986

The effect of $TiO_2$ addition to the 90wt% Cordierite-10wt% Enstatite base glass was investi-gated to understand the crystallization behavior of the glass. Glasses with addition of $TiO_2$ less than 7, 5wt% had a tendency of surface crystallization and were cracked when heat treated and in this case the crystalline phase formed was indialite. glasses with addition of $TiO_2$ more than 10wt% to 15wt% were crystallized in bulk when heat treated and were suitable for glass-ceramics. The highest microhardness 1640kg/$mm^2$ was obtained when the glass of 12.5wt% $TiO_2$ addition was heat treated at 762$^{\circ}C$ for 60 minutes for nucleation and at 1135$^{\circ}C$ for 20 minutes for crystal growth and in general higher microhardness was obtained when crystalline phase of magnesium aluminum titanate and $\mu$-cordierite were developed. Avrami equation for crystal growth kinetics was applicable in glasses of less than 7.5 wt% $TiO_2$ addition and in case of glasses of more than 10wt% $TiO_2$ addition it was not applicable because of too fast crystal growth.

• Journal of Korean Clinical Health Science
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• v.9 no.2
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• pp.1535-1542
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• 2021

Purpose. This study categorizes vision correction subjects by age and gender, and aims to find out which glasses or contact lenses the subjects of each age group show preference based on the answers of the questionnaires answered by the subjects. Methods. A study was conducted in the form of a questionnaire through SNS on the types of correction tools used for the purpose of correcting ametropia for the general public from their teens to their 50s. Results. As for the most preferred method for correcting asymmetry, in the case of teenagers, glasses were the most common at 50%, glasses and contact lenses the most at 43.8% each, and glasses in their 30s at 50%. Those in their 40s had the most glasses at 75%, and those in their 50s wore glasses and sunglasses at 50%. Conclusions. Since the demand for vision correction and eye protection methods varies according to age and gender, it is necessary to identify and design the flow of these demands in the existing market. Therefore, it is necessary to make a judgment that can contribute to the development of eye health targeting the main customer base and the provision of appropriate services to consumers.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.237-242
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• 1988

Ion exchange behavior of glasses was investigated in this study. The used glasses were Soda-limesilica glasses that was produced by float process. In order to analyse effects of ion exchange, some properties were measured; $K^+$ ion penetration depth, compressive stress, compression layer thickness, amount of $K^+$ ion exchange and density, in case of 43$0^{\circ}C$-8h and 45$0^{\circ}C$-6h, and activation energy is 17.0kcal/mole. Further it can be seen that excessive heat treatment brings about stress relaxation.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.23-29
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• 2001

In the SP series of glasses, the formation of droplet is well done with increasing PbO. But in the case SP-1, droplet could not be observed in low concentration PbO. These results are considered that PbO does the role of a network modifier, so the crosslinking break down by $SiO_2$. But, in the glasses contained PbO above 50 mol%, glasses are formeddue to $Pb^{4+}$ ion does the role of a network former. As a result of electrical conductivity analysis for SP series of glasses, the electrical conduction is due to bipolaron at high temperature, and it is due to single polaron hopping at low temperature. In the SP series of glasses, electrical conduction mechanism coincide with the correlated-barrier hopping(CBH) model.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.137-143
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• 2008

The spherical glasses lenses are typically classified into two groups such as (+) diopter lens and (-) diopter lens by the refractive power index. The thermal deformation of a lens is occurred by external heat source and is changed respected to the diopter of a lens. In this paper, the thermal deformation of spherical glasses lenses were quantitatively measured by using ESPI (electronic speckle pattern interferometry) which has an advantage that the non-contact, non-destructive and precise deformation measurement is available due to the coherency characteristic. The temperature changes were measured by IR camera. It makes experiments over 14 types of the plastic glasses lenses. From the results, it was confirmed that the larger diopter lens showed the less thermal deformation in case of the (+) diopter lens. On the other hand, the thermal deformation of the (-) diopter lens was measured with uniform pattern when the same temperature changes were applied. Also, it was found that the thermnal deformation of the (+) diopter lens is less than that of the (-) diopter lens. Therefore, it is expected that when the thermal deformation is occurred to the various types of the lens, the variation of the focal length caused by the thermal distortion of a lens would be measured quantitatively.

• Journal of the Korean Ceramic Society
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• v.43 no.7 s.290
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• pp.433-438
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• 2006

In order to examine the working condition of melts in tin bath of float process it was investigated Sn diffusion behavior and solidification rate of melts for alkali-alkaline earth-silica PDP substrate glasses such as commercial CaO rich CS-77 glass, commercial $Al_2O_3$ rich PD-200 glass and self developed $SiO_2$ rich T-series (T-2, T-4, T-6) glasses. In the case of Sn depth and concentration created in glass surface by ion exchange between Sn and alkali, T-series showed lower value than CS-77, especially T-2 is more excellent than PD-200. The solidification rate of melts expressed by cooling time between $log{\eta}=4\;and\;7.6dPa{\cdot}s$ was low for T-series comparing with CS-77 and PD-200. Therefore, it was concluded that T-series is desirable considering forming condition in the tin bath of the float process.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.579-588
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• 2018

Purpose : To analyze the eyeglasses supply system for ametropic soldiers in ROK military. Methods : We investigated and analyzed the supply system of eyeglasses for the ametropic soldiers provided by the Korean military. The refractive powers and corrected visual acuity were measured for 37 ametropic soldiers who wear insert glasses for ballistic protective and gas-masks supplied by the military based on their habitual prescriptions. Full correction of refractive error was prescribed for subjects having less than 1.0 of distance visual acuity, and comparison was held for inspecting the changes in corrected visual acuity. Suggestions were provided for solving the issues regarding current supplying system, and this study investigated the applicabilities for utilizing professional optometric manpower. Results : The new glasses supplied by army for ametropic soldiers were duplicated from the glasses they worn when entering the army. The spherical equivalent refractive powers of the conventional, ballistic protective and gas-mask insert glasses supplied for 37 ametropic soldiers were $-3.47{\pm}1.69D$, $-3.52{\pm}1.66D$ and $-3.55{\pm}1.63D$, respectively, and the spherical equivalent refractive power of full corrected glasses was $-3.79{\pm}1.66D$, which showed a significant difference(p<0.05). The distant corrected visual acuity measured at high and low contrast(logMAR) of conventional, ballistic protective and gas-mask insert glasses were $0.06{\pm}0.80$, $0.21{\pm}0.82$, $0.15{\pm}0.74$, $0.34{\pm}0.89$, $0.10{\pm}0.70$ and $0.22{\pm}0.27$, respectively, while the corrected visual acuity by full corrected glasses were increased to $0.02{\pm}1.05$, $0.10{\pm}0.07$, $0.09{\pm}0.92$, $0.26{\pm}0.10$, $0.04{\pm}1.00$ and $0.19{\pm}1.00$, respectively. There was a significant difference(p<0.05) except for the case of the low contrast corrected visual acuity of the conventional and gas-mask insert glasses. The procedure for ordering, dispensing, and supplying military glasses consists of 5 steps, and it was found that approximately two weeks or more are required to supply from the initial examination. Conclusion : The procedure of supplying the military glasses showed three issues: 1) a lack of refraction for prescription system, 2) relatively long length of time required for supplying the glasses, 3) an inaccurate power of supplied glasses. In order to solve those issues, in the short term, education is necessarily required for soldiers on the measurement of the refractive powers, and in the near future, further standard procedures for prescription of glasses as well as the securement of optometric manpower are expected.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.109-114
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• 2009

Purpose: This study was designed to investigate the condition of refractive correction on wearing glasses currently of elementary school children and their accommodative ability in Jinju city. Methods: Objective refraction, subjective refraction, amplitude of accommodation, negative and positive accommodation, accommodative facility, and dynamic retinoscopy were examined on 60 elemenary school children who aged 8~12 wearing myopiacorrected glasses. Results: The condition of refractive corrections was distributed that a case of full correction was 11.7%, a case of low correction with more than 0.8 visual acuity (VA) was 10%, and a case of low correction with less than 0.8 VA was 78.3% in wearing glasses currently. In results from examination of accommodative ability, the number of children having accommodative anomaly is 8 persons (13.3%), they were divided into accommodation insufficiency (4 persons), accommodative facility insufficiency (2 persons), accommodation excess (1 person), and accommodation insufficiency related to ocular function (1 person). Conclusions: It is demanded a periodic inspection of refractive correction to growing children, and the refractive correction after due consideration to accommodative ability is really needed.