• Journal of Integrative Natural Science
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• v.6 no.2
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• pp.76-81
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• 2013

ZnO nanoparticles and vinyl pyridine were added to the mixture of MMA (methyl methacrylate), HEMA (2-hydroxy ethyl methacrylate) and NVP (N-vinylpyrrolidone) in a mould at various concentrations. Cross-linker EGDMA (ethyleneglycoldimethacrylate) and AIBN (azobisisobutyronitrile) initiator were finally added to the mixture and then heated at $80^{\circ}C$ for 60 min to prepare high-performance hydrogel ophthalmic lens. The physical properties of the hydrogel ophthalmic material were investigated by measuring the average value of refractive index, water content and optical transmittance. The refractive index of 1.429~1.450, water content of 34~41%, and visible transmittance of 78~90% were obtained. The material is possibly used to manufacture UV-block hydrogel contact lens.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.457-463
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• 2013

To determine the impact of artificial tears which include carboxymethyl cellulose on a hydrogel contact lenses. Methods: A contact lenses made of the cross-linking agent, EGDMA (ethylene glycol dimethacrylate) and HEMA (2-hydroxyethyl methacrylate) and with added NVP (n-vinyl-2-pyrrolidone) and MMA (methyl methacrylate) was evaluated for water content, refractive index, spectral transmittance and contact angle of produced contact lens. Results: The physical properties of the sampled copolymerized polymers showed that water content, refractive index, visible ray transmittance and contact angle were in the range of 26.61%~48.58%, 1.422~1.455, 80.8%~91.4% and $33.93^{\circ}{\sim}65.70^{\circ}$, respectively. In addition, after soaking with artificial tears, the water content, refractive index and contact angle were in the range of 24.46%~48.25%, 1.422~1.457, 77.0%~91.0% and $37.25^{\circ}{\sim}77.33^{\circ}$, respectively. The changes of the physical property depending on hydration time and showed an increase of refractive index and contact angle, decrease of water content and visible ray transmittance. Conclusions: Artificial tears which include carboxymethyl cellulose sodium which is used as a wetting agent influenced water content, refractive index, contact angle and spectral transmittance of a hydrogel contact lenses.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.69-77
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• 2014

Purpose: The functional ophthalmic lenses containing fluorine-substituted aniline group (2,4-difluoroaniline, 2,6-difluoroaniline, 3,4-difluoroaniline) were manufactured and the physical and optical characteristics of copolymerized ophthalmic lens were investigated. Methods: HEMA (2-hydroxyethylmethacrylate), NVP (N-vinyl pyrrolidone), MA (methacrylic acid), the cross-linker EGDMA (ethylene glycol dimethacrylate) and the initiator AIBN (azobisisobutyronitrile) were used as a basic combination and fluorine-substituted aniline group (2,4-difluoroaniline, 2,6-difluoroaniline, 3,4-difluoroaniline) were used as additives for preparing the hydrogel soft contact lenses. The hydrogel ophthalmic lens was manufactured by cast mould method and the ophthalmic lenses were stored in a 0.9% NaCl normal saline for 24 hrs. Results: The optical transmittance of the sample with addition 2,4-difluoroaniline showed that the UV-B(9.8~51.4%), UV-A(58.8~79.2%) and visible transmittance(87.0~90.4%). In the case of 2,6-difluoroaniline were measured the UV-B(80.2~83.2%), UV-A(85.8~86.4%), and visible transmittance(90.8~91.4%). Also, the optical transmittance of ophthalmic lens containing 3,4-difluoroaniline were measured the UV-B transmittance of 3.8~30.4%, UV-A transmittance of 47.8%~74.4% and the visible transmittance of 86.2~91.0% respectively. Conclusions: Based on the results of this study, 2,4-difluoroaniline and 3,4-difluoroaniline can be used effectively as additive for UV-blocking ophthalmic contact lenses.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.125-131
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• 2015

Purpose: The effect of pigmentation in circle contact lens on lens wearers' tear film stability was investigated in this study. Methods: Non-invasive tear film break-up times of 54 normal eyes before and after lens wearing in twenties and the portion of first tear breakup were measured. The frontal and back surface roughness of circle contact lens was further observed with a scanning electron microscope. The clear lens which was made of hilafilcon B and circle contact lenses which were made of hilafilcon B, polymacon and copolymer of HEMA NVP were tested. Results: Non-invasive tear film breakup time was significantly reduced compared with it before lens wearing. In some case, statistically significant difference in tear film breakup time was also observed between circle contact lenses. The tear file break-up was usually early started in lower than upper portion, and in temporal than nasal portion although there was variation in the lens material. The tear film break-up of circle contact lenses made of hilafilcon B was more commonly observed in peripheral portion(pigmented area) compared with clear contact lens made of same material. Conclusions: The present study revealed that the stability of tear film was affected by wearing circle contact lens and the result seems to be used as the basis for the problem solving that can occur due to the pigmentation when wearing circle contact lens.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1252-1256
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• 2010

A polyvinylpyrrolidone (PVP)/Ag nanocomposites was prepared by the simultaneous thermal reduction and radical polymerization route. The in situ synthesis of the Ag/PVP nanocomposites is based on the finding that the silver n-propylcarbamate (Ag-PCB) complex can be directly dissolved in the NVP monomer, and decomposed by only heat treatment in the range of 110 to $130^{\circ}C$ to form silver metal. Silver nanoparticles with a narrow size distribution (5 - 40 nm) were obtained, which were well dispersed in the PVP matrix. A successful synthesis of Ag/PVP nanocomposites then proceeded upon heat treatment as low as $110^{\circ}C$. Moreover, important advantages of the in situ synthesis of Ag/PVP composites include that no additives (e.g. solvent, surface-active agent, or reductant of metallic ions) are used, and that the stable silver nanocolloid solution can be directly prepared in high concentration simply by dissolving the Ag/PVP nanocomposites in water or organic solvent.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.9-15
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• 2004

The copolymerization of HEMA with different hydrophilic and hydrophobic co-monomers allows for the manipulation of their intrinsic properties. 2-Hydroxyethylmethacrylate (HEMA)-based hydrogels thus are of great interest due to their outstanding physico-mechanical properties and chemical stability. The idea to use HEMA in order to create thermo-sensitive polymers was based on our assumption that thermal-sensitivity comes from a suitable hydrophilic-hydrophobic balance of macromolecules. In this work we have chosen N-vinyl pyrrolidone as a hydrophilic co-monomer with the relatively hydrophobic HEMA due to its good polymerizing properties as well as its non-toxicity in a polymer state and deserved recognition as a biocompatible material. As a result, copolymerization of NVP and HEMA was successful in obtaining new types of thermo-sensitive polymers composed of hydrophilic and hydrophobic monomers.

• 한국벤처창업학회:학술대회논문집
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• 2020.06a
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• pp.141-147
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• 2020

최근 중소기업연구원 연구자료에 의하면 우리나라 중소벤처기업의 혁신 수준은 OECD 최하위 수준이며, 네트워크 기반의 협력체계가 필요하다고 발표하였다. 또한, 최근의 혁신 행동 관련 연구를 살펴보면 내적 혁신 행동에 대한 연구는 많으나, 외부 네트워크 혁신 행동과 연동한 연구는 미진하였다. 따라서 본 연구의 목적은 CEO 변혁적 리더십이 조직 공정성을 기반으로 내적 외적 혁신 행동을 실행함에 있어서 유연적 조직 문화의 조절 효과가 사업성과에 미치는 영향에 대해서 알아보고자 한다. 이론적 고찰을 통해 중소벤처기업 성과모형, CEO 변혁적 리더십, 내적 혁신 행동, 외적 혁신 행동, 조직 공정성, 유연적 조직문화, 사업성과에 대해서 알아보았다. Chrisman 등(1998)의 중소벤처기업 성과모형은 ①기업가(entrepreneur), ②산업구조(industry structure), ③사업전략(business strategy), ④자원(resources), ⑤조직구조(organization structure, processes and systems) 등 5가지를 제시하였다. 본 연구에서는 Chrisman 등(1998)의 벤처기업 성과모형 NVP = f(E, IS, BS, R, OS)을 적용하여 연구 모형을 설계하고 실증 검증하였다. 향후 중소벤처기업 성과모형으로서 직원들의 미래전망과 자부심 향상에 본 연구가 시사점을 제공할 뿐만 아니라 중소벤처기업 경쟁력 강화를 위한 기업 혁신 행동 컨설팅 연구에도 기여할 수 있을 것으로 판단된다.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.4
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• pp.1389-1393
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• 2012

Objective: To discuss the significance of DOG1, CD117 and PDGFRA in the diagnosis of gastrointestinal stromal tumors (GISTs), and analyze their correlations with clinicopathological features and risk ranking. Method: DOG1, CD117 and PDGFRA were detected with IHC Envision ldpe-g-nvp in 63 GISTs and 43 cases of non-GISTs, and analyzed for relations with clinicopathological factors (gender, age, location, tumor size, mitotic phase, histology) and risk degree. Results: The positive expression rate of DOG1, CD117 and PDGFRA in GISTs was 84.1% (53/63), 90.5% (57/63), 53.2% (33/63), respectively. Among the 6 CD117 negative cases, all were DOG1 positive and 5 were PDGFRA positive. Rates in patients with non-GISTs was 11.6%, 16.3%, 6.98%, respectively. Expression of DOG1 and PDGFRA demonstrated no significant variation with gender, age, position, tumor size, mitotic phase, histology, and risk rank. However, CD117 was related with position and histology (P=0.008 and P=0.045), those in the mesentery having a higher positive rate than those derived from stomach, small intestine, colon and rectum (50.0% vs 94.7%, P=0.008). Furthermore CD117 was also highly expressed in spindle and epithele types. Conclusions: DOG1 had a good sensitivity and specificity as a kind of newly discovered marker, especially for KIT negative GISTs. However, DOG1, CD117 and PDGFRA cannot be used for assessing the rish of patients.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.32-45
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• 2016

For effective utilization of downtown area, many studies about underground have been performed around the world, and double-deck tunnel have being operated in USA, Europe and China, etc. (A86 East Duplex in France, M30 tunnel project in Spain, SR-99 in seattle, USA, Yangtze river tunnel in China) In Korea, the research about network type double-deck tunnel in deep underground space is in progress to solve the traffic jam and secure the ground space. In this study, a number of factors required for double-deck tunnel in deep underground are analyzed through the existing ventilation design outline and unique ventilation design factors for network type double-deck tunnel are established by reviewing design cases of overseas double-deck tunnel.

• Journal of Integrative Natural Science
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• v.6 no.1
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• pp.1-7
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• 2013

Polyurethane resin containing isocyanate is marked by excellent tensile and mechanical strengths and this test aims to gauge its applicability as a medical high polymer. Tris [2-(acryloyloxy)ethyl]isocyanurate and hexamethylenediisocyanate were added to a basic mixing ratio of HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), NVP (n-vinyl-2-pyrrolidone) and crosslink agent, EGDMA (ethylene glycol dimethacrylate) with increasing proportions and copolymerized respectively. Also, the basic physical properties of the polymerized high polymers including refraction rate, tensile strength, light transmission and water content were measured to confirm that they are appropriate as hydrogelcontact lenses. After measuring the physical properties of high performance polymers produced by adding tris [2-(acryloyloxy) ethyl]isocyanurate, it was found that the average tensile strengths of sample TRIS1 to TRIS10 were between 0.285 and 0.612 kgf, while the average values of refractive index were ranged from 1.441 to 1.449 with water content from 30.00 to 37.35%.The measurement of physical properties of the copolymers generated by adding hexamethylenediisocyanate showed that the average tensile strength of sample HEXA1 to HEXA10 ranged from 0.267 to 1.742 kgf, the refractive index ranged from 1.443 to 1.475 and water contents were in the range of 21.22 to 35.58%. In all combinations the transmission rates satisfied the transmittance of general hydrogel contact lenses. From theresults, it is possible to conclude that the produced copolymers can be used as contact lens materials with excellent tensile strength.