• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.24-30
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• 2007

The effects of C, Si and RE additions on the tendency of chill formation of ductile cast iron obtained from metal mold casting were investigated. In case of metal mold cast, the ductile cast iron with 2.5%Si had pearlitic matrix, and specimens with 2.9%Si had bull's eye type regardless of C contents. As-cast specimen with a large amount of fine graphites could be obtained by adding 0.2% RE. Normalizing process was necessary to remove carbide and form a large amount of spheroidal graphites for the as-cast specimens. Good mechanical properties could be obtained by heat-treatment of as-cast specimens with pearlitic matrix. Normalizing the specimens with RE caused the reduction in mechanical properties.

• ETRI Journal
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• v.45 no.6
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• pp.1046-1055
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• 2023

We introduce a display for virtual-reality (VR) fire training. Firefighters prefer to wear and operate a real breathing apparatus while experiencing full visual immersion in a VR fire space. Thus, we used a thin head-mounted display (HMD) with a light field and folded optical system, aiming to both minimize the volume for integration in front of the face into a breathing apparatus and maintain adequate visibility, including a wide viewing angle and resolution similar to that of commercial displays. We developed the optical system testing modules and prototypes of the integrated breathing apparatus. Through iterative testing, the thickness of the output optical module in front of the eyes was reduced from 50 mm to 60 mm to less than 20 mm while maintaining a viewing angle of 103°. In addition, the resolution and image quality degradation of the light field in the display was mitigated. Hence, we obtained a display with a structure consistent with the needs of firefighters in the field. In future work, we will conduct user evaluation regarding fire scene reproducibility by combining immersive VR fire training and real firefighting equipment.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.65-73
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• 2008

Purpose: The purpose of this study is to investigate the effect of age in the response to long-term overnight orthokeratology (OK) lens wearing. Methods: Among volunteers, ninety-five healthy subjects who had no eye diseases and could wear OK contact lens at least for 8 hours every day were divided into three groups children, youngsters and young adults. Unaided logMAR visual acuity, refractive error, apical corneal radius, corneal asphericity and central corneal thickness were measured with different period; before and after one day, one week, two weeks, one month, three months and six months of OK lens wear. Paired student t-test, ANOVA analysis and Pearson correlation were used with a critical p value of 0.05 for statistical analysis. Results: All groups showed statistically significant (p<0.001) improvement in unaided visual acuity, a trend for flattening in the apical corneal radius, decrease in central corneal thickness and less prolate after OK lens wear. The child group showed significantly rapid change (p<0.001) in visual acuity, and apical corneal radius showed that they reached the targeted refractive change earlier compared with youngster and adult groups. The visual effect of OK lens was significantly related with the change in central corneal thickness after long-term OK lens wear, especially in child and youngster group, and central corneal thickness were highly correlated with the targeted refractive change. Conclusions: Visual acuity change is statistically correlated with the central corneal thickness change, which is highly correlated with targeted refractive change in the long-term orthokeratology and younger lens wearers showed a rapid response to OK lens wear, suggesting a reduced epithelial response with increasing age. The results found this study extends our understanding and development in the long-term orthokeratology.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2839-2843
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• 2013

In this study, the relation between the corneal refractive power and the tear break-up time(TBUT) was analyzed. The results can be effectively used in eye clinics and served as the reference on wearing the contact lenses. We had measured the radius of the corneal of university students who are in the range of 21 to 27 year-old and who don't have eye disease. The corneal refractive power was calculated by using the radius of the corneal. And TBUT is the time when the mire image is distorted first time. The relation between the corneal refractive power and TBUT in right eye was a linear as 'y=37.921-0.610x', in which the larger the refractive power of the cornea is, the shorter TBUT is(negative relationship; r=-0.462, p=0.010). The relation in left eye was also a negatively linear as 'y=41.894-0.695x'(r=-0.509, p=0.004). Consequently, in both eyes the corneal refractive power and TBUT have a negative correlation when myopia is a high. It is possible to predict TBUT, which is necessary in deciding on wear of contact lenses, by measuring the corneal radius of subjects.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.15-26
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• 2009

Purpose: To compare and analyze the ocular changes after wearing conventional and 2-weeks cosmetic tinted contact lens, which were made of different material and fabrication method. Methods: Thirty five university students, age of twenties, participated in this study. With daily wearing schedule, they had worn temporary cosmetic tinted lens for 2 weeks and conventional tinted lens for two month in their right and left eye, respectively. Subjective symptoms and objective signs were graded by using CCLRU scales and corneal thickness were measured after 1 day and 2 months wearing, and under or over 5 hours wearing in a day, respectively. Results: Major subjective symptoms found in the student wearing cosmetic tinted contact lens for a 1 day and 2 months were dryness, redness, foreign body sensation and itchiness. It was also found that those symptoms were more severe in left eye (conventional cosmetic tinted contact lens) than right eye (2-weeks cosmetic tinted contact lens). However, symptoms of redness in both eyes showed statistically significant difference in the case of 1 day and 2 months wearing and under or over 5 hours wearing in a day (p=0.000). After 2 months wearing, left eye with conventional cosmetic tinted contact lens showed limbal redness (p=0.000) and bulbar conjunctival redness (p=0.012) with statistically significance, whereas there was no significant difference in both eyes before lens wear. Left eye showed statistically significant changes in all objective signs, but right eye showed palpebral conjunctival redness, corneal staining and conjunctival staining. Therefore, it was concluded that conventional cosmetic tinted contact lens may be more effective on ocular changes after wearing of lens. A statistically significant changes in both eyes after wearing lens were found that corneal thickness increased about $5{\mu}m$ (p=0.001) in right eye whereas $7{\mu}m$ (p=0.004) in left eye. Conclusions: A statistically significant number of participants in this study preferred to wearing of high Dk/t temporary cosmetic tinted contact lens made by sandwich method which resulted in less ocular changes and may give more healthy and safe ocular conditions.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.107-113
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• 2000

This study has analyzed soft contact lens care-after-sale and periodic examinations at optical shops and eye clinics. And I wish to make that use of educational data for the soft contact lens lesson of the department of ocular optics. This questionnaire studied the status of care for soft contact lens and periodic examination, of students who wears soft contact lens. The results are as follows: First, 7.5% of students questioned wore soft contact lens. More women than men wore soft contact lens. The soft contact lens wearers purchased lens mainly at optical shops. 78.5% of them wore daily wear lens. Because of cosmetic advantages of soft contact lens. 47.9% of them wore soft contact lens. 72.5% of them wore soft contact lens less than 12 hours per a day. 32.0% of them has worn soft contact lens more than 6 months less than 1 year. 51.1% of them experienced irritation. 39.7% of them have exchanged soft contact lens between 6 and 9 months. Secondly, when purchasing lenses. 60% of soft contact lens wearers were given instructions of general care, such as duration of wearing lens, how to remove protein, how to store, and how to sterilize at both of eye clinics and optical shops. But the proportion of instructions, such as side effects and periodic examination which were given to soft contact lens wearers, is lower both at eye clinics and optical shops. Especially at optical shops, the proportion of instruction for periodic examination, is lower than at eye clinics(p<0.05). Thirdly, The proportion of operations of periodic examinations after use of soft contact lens both at eye clinics and optical shops, is low. The soft contact lens wearers have had more periodic examinations at eye clinics than at optical shops. But the rate of non-periodic examination at optical shop is 87.9%. And for periodic examinations, general care was done at optical shops. On the other hand, eye examinations, general care, and treatments were done more at eye clinics. Fourthly, 60.3% of the soft contact lens wearers understood the necessity of the periodic examinations, but actually, only 6.4% of them were given the schedule for the periodic examinations, and 2.5% of them were given at an optical shop(p<0.01).

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.3
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• pp.191-201
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• 2016

Purpose: In the present study, the effect of artificial tears with different ingredients on tear film stability and subjective symptoms of dry eyes in the early stage of soft contact lenses wear was investigated. Methods: The three kinds of artificial tears and saline solution were respectively applied onto 50 dry eyes which wore soft contact lenses made of etafilcon A. Then, non-invasive tear film break-up time (NIBUT) was measured at every five minutes for 30 minutes right after the instillation of artificial tears, and the changes in blink rate and subjective symptoms were estimated after 30 minutes from the instillations. Results: All three kinds of artificial tears increased NIBUT larger than saline. The effect of increasing NIBUT immediately after the instillation of artificial tears was the largest when the artificial tear containing viscosity enhancer was used. The duration time of the effect was the longest when the artificial tear having both surfactant and viscosity enhancer was applied. The blink rate was not significantly changed when both artificial tears and saline solution were instilled. Subjective symptoms were significantly improved by the instillation of both artificial tears and saline solution and dryness, irritation, tiredness, stiffness, dazzling were improved by the use of most solutions. However, the subjective symptoms were rebounded to the level before the instillation of artificial tears after 30 minute-instillation. Conclusions: It was revealed that both artificial tears and saline solution could improve the subjective symptoms of dry eye in the early stage of soft contac lenses however, the effect of these solutions on the tear film stability was different according to the components. From the results, it is suggested that the proper selection of artificial tears is necessary for the improvement of dry eye symptoms at the early stage of soft contact lenses wear in dry eye.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.375-381
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• 2011

Purpose: The purpose of this research was to see how wearing either a SCL or a C-SCL effected the dryness of a person's eye depending on how long they wear either type of lens. Methods: This study was carried out on 52 subjects (104 eyes) who were all in their twenties and had previously experienced wearing contact lenses. All of these subjects were required to wear either a SCL or a C-SCL, which were made out of the same material, for three months. Contents such as the McMonnies Questionnaire survey, the blinking rate per min. and the Noninvasive tear break-up time test (NIBUT) were later conducted on the subjects for this study. Results: According to the results of the McMonnies Questionnaire, it was concluded that the longer the subject wore the SCL and C-SCL, the value of the measurements gradually increased. On the other hand, the results from the NIBUT concluded that the longer the subject wore the SCL, the value of the measurements eventually decreased. However, according to the measurements of the blink rate test, it was concluded that neither results had a significant change. Conclusions: It was concluded that long-term wearing of SCL and C-SCL could be the cause of the induction and progression of dry eyes.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.7-15
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• 2009

Purpose: To investigate the corneal recovery after discontinuing orthokeratology (OK) lenses wear in children for long-term period. Methods: Among the OK lens wearers who wear over 8 months and showed successful refractive correction, 25 subjects were selected who want to discontinue the OK lenses. Uncorrected visual acuity, refractive correction, corneal curvature (Sim K), central corneal thickness and corneal eccentricity were measured during the OK lens wearing period and after discontinuation for 1 month. Results: Uncorrected visual acuity and corneal shape had remodeled significantly during the OK lens wear and recovered significantly during the first week of discontinuation. Uncorrected visual acuity and refractive correction had achieved full recovery 2 weeks after discontinuation of lens wear and were highly correlated with the changes in corneal thickness. But corneal shape recovered slowly, eccentricity had recovered fully after 1 month and corneal curvature and central thickness had not been achieved full recovery until 1 month after discontinuation. Conclusions: Recovery of after longterm use of OK lens is rapid for refractive change, but slow for corneal curvature and central thickness that to refit the contact lenses, practitioners need patience.

• Journal of the Korea Fashion and Costume Design Association
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• v.17 no.4
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• pp.77-90
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• 2015

This study is to designed to provide foundation for knit design which can apply the thickness and flexibility of jacquard knit by analyzing and comparing mechanical properties of 7 types of jacquard (normal jacquard, bird's eye jacquard, floating jacquard, tubular jacquard, ladder's back jacquard, blister jacquard, transfer jacquard) widely used in knit design to achieve the results. The sample was projected by using 7 gauge and SES-122S type computer knitting machine house tooth pattern with two colors were applied to 7 types of jacquard using Acrylic/Wool(30%/70%) $2/50.5^{\prime}s{\times}4ply\;yarn$ by Shimaseiki MFG., Ltd computer knitting machine. The mechanical properties of 7 types of jacquard samples were measured using KES-FB (Kawabata Evaluation System for Fabric, Kata Tech Co. Ltd). HV(Hand Value) and THV (Total Hand Value) were calculated by using the formula of KN-402-KT and KN-301-WINTER respectively. The measurements were evaluated by 0-to-5 rating scale. As result, the floating jacquard was found to have excellent drape, making it suitable for express feminine silhouette with its most flexible and smooth touch. On the other hand, bird's eye jacquard is adequate for a suit jacket and coat regarding its excellent volume and flexibility. Blister jacquard and tubular jacquard are thick, heavy and stiff knit and both are suitable for simple box-style design. Ladder's back jacquard, however, is more appropriate for expressing the design of feminine charm and voluminous design. Based on the result of this study, it is supposed to provide basic information for development of knit industry regarding jacquard knit by designing the creative knit wear with high production efficiency.