• 대한화학회지
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• 제54권1호
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• pp.105-109
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• 2010

Propylene glycol을 첨가제로 사용하여 HEMA (2-hydroxyethyl methacrylate)와 교차결합제인 EGDMA (ethylene glycol dimethacrylate) 그리고 개시제인 AIBN(azobisisobutyronitrile)을 사용하여 공중합 하였다. 생성된 고분자의 물리적 특성을 측정한 결과, 함수율 37.06~38.71%, 굴절률 1.492~1.432, 가시광선 투과율 89.4~91.5%, 인장강도 0.1416~0.2302 kgf 그리고 접촉각의 경우 $38.60{\sim}53.53^{\circ}$ 범위의 분포를 나타내었다. 따라서 propylene glycol을 첨가한 콘택트렌즈 재료의 경우, 기본적인 콘택트렌즈의 물성을 만족하였으며 함수율의 큰 변화를 나타내지 않으면서도 습윤성과 인장강도를 증가시키는 결과를 보여주었다.

• 한국도로학회논문집
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• 제14권6호
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• pp.1-11
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• 2012

PURPOSES : The purpose of the study was to examine dynamic features of concrete after mixing a little macro fiber with small aspect ratio and long length utilized for bridge, tunnel and shotcrete for tensile performance and crack control in domestic/overseas countries with cement concrete pavement mix. METHODS : Coarse aggregates with small aspect ratio and macro fibers with maximum length of approximately 32 mm are introduced in small quantities in the mix proportions of concrete pavement so as to prevent loss of the workability. Then, this study intends to evaluate the applicability of macro fibers in the mix proportions of concrete pavement by examining the basic construction performance, as well as the change of toughness, the equivalent bending strength and the flexural toughness index caused by compression, bending, tension and the flexural stress-displacement curve. RESULTS : As the results, in each kind of macro fiber, polyvinyl alcohol fiber and steel fiber displayed a good performance. CONCLUSIONS : In 0.2 and 0.3% of fiber contents, it is appeared that polyvinyl alcohol fiber has a large effect on improvement of tensile performance and steel fiber on improvement of deforming performance of bending stress.

• 한국재료학회지
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• 제33권1호
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• pp.1-7
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• 2023

The physical and antibacterial properties of ophthalmic lenses fabricated by copolymerization with hydrogel monomers using two types of graphene were measured, and their usability as contact lens materials was analyzed. For polymerization, silicone monomers, including SID-OH, 3-(methacryloxy)propyl tris(trimethylsiloxy)silane, and decamethylcyclopentasiloxane, were used, and N,N-dimethylacetamide, ethylene glycol dimethacrylate as a crosslinking agent, and azobisisobutyronitrile as an initiator were added. Also, graphene oxide nanoparticle (GON) and graphene nanoplate (GNP) were used as an additive, and the physical properties of the lenses fabricated after copolymerization were evaluated. The fabricated lenses satisfied the basic physical properties of general hydrogel contact lenses and showed the characteristics of lenses with high water content, and the disadvantage of very weak durability, due to low tensile strength. However, it was confirmed that the tensile strength and antibacterial properties were greatly improved by adding GON and GNP. With GON, the oxygen permeability and refractive index of the fabricated lenses were slightly improved. Therefore, it was determined that the graphene materials used in this study can be used in various ways as a contact lens material.

• Journal of Construction Engineering and Project Management
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• 제4권2호
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• pp.41-46
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• 2014

RCC consumes large quantities of natural resources like gravel stone and steel, and there is a need to investigate on an innovative material that utilizes limited quantities of natural resources but should have good mechanical strength. This study deals with the experimental investigation of strength evaluation of cementitious composites reinforced with polyolefin fibers from 0% to 2.5% (with interval of 0.5%), namely Polyolefin Fiber Reinforced Cementitious Composites (PL-FRCC) and developing statistical regression models for compressive strength, splitting-tensile strength, flexural strength and impact strength of PL-FRCC. Paired t-tests (for each PL fiber percentage 0 to 2.5%) bring out that there is significant difference in compressive and splitting-tensile strength when curing periods (3, 7, 28 days) are varied. Also, a strong relationship exists between the compressive and flexural strength of PL-FRCC. The proposed mathematical models developed in this study will be helpful to ascertain the mechanical strength of FRCC, especially, when the fiber reinforcing index is varied.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.175-176
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• 2011

Applying previous studies performed in the moisture transportation characteristics and shrinkage of lightweight concrete application of shrinkage reduction is to discuss. Applicability of shrinkage reduction effect of lightweight concrete applies for the analysis of PSC girder bridge beam placed on the construction site. Stress of the concrete bridge deck, rebar quantity is calculated by effective elastic modulus method and crack risk is assessed by moisture transport and differential shrinkage analysis. After approximately 10 days maximum tensile stress occurs 6MPa, similar to the case of normal concrete, a maximum tensile stress occurs 3MPa in lightweight concrete and comparing to normal concrete stress was reduced to approximately 50%. Normal and lightweight concrete crack index, respectively, is reduced 1.6 to 1.2, 1.2 to 0.9 in surface and boundary region. Therefore, reduction in shrinkage of concrete were able to confirm reduction of crack risk.

• Macromolecular Research
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• 제13권3호
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• pp.194-205
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• 2005

The network structure of Ni-coated carbon black (NCB) composites filled with phenolic resin was investigated by means of using scanning electron microscopy, viscosity, interfacial tension, shrinkability, Flory-Huggins interaction parameters, and swelling index. The electrical properties of the composites have been characterized by measurement of the specific conductivity as a function of temperature. Additionally, the variation of conductivity with temperature for the composites has been reported and analyzed in terms of the dilution volume fraction, relative volume expansion, and barrier heights energy. The thermal stability of phenolic-NCB composites has been also studied by means of the voltage cycle processes. The experimental data of EMI wave shielding were analyzed and compared with theoretical calculations. The mechanical properties such as tensile strength, tensile modulus, hardness and elongation at break (EB) of NCB-phenolic resin composites were also investigated.

• Carbon letters
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• 제16권2호
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• pp.121-126
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• 2015

Carbon fibers are prepared by stabilizing pitch fibers accompanying electron beam (E-beam) irradiation. The carbon fibers pretreated by E-beam irradiation achieve a higher stabilization index than the carbon fibers that are only heat-stabilized. In addition, the carbon fibers subjected to E-beam irradiation in the stabilization step exhibit a comparable tensile strength to that of general purpose carbon fibers. The carbon fibers pretreated with an absorbed dose of 3000 kGy have a tensile strength of 0.54 GPa for a similar fiber diameter. Elemental, Fourier-transform infrared spectroscopy, and thermogravimetric analyses indicate that E-beam irradiation is an efficient oxidation and dehydrogenation treatment for pitch fibers by showing that the intensity of the aliphatic C-H stretching and aromatic $CH_2$ bending (out-of-plane) bands significantly decrease and carbonyl and carboxylic groups form.

• 펄프종이기술
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• 제35권4호
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• pp.75-80
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• 2003

The purpose of this study was to design wedding dress by using Korean paper(Hanji). The Korean paper showed the good(excellent) properties of durability, softness, and tensile strength was 3.7Kg, tear index was 6 mN$.$$m_2$/g and folding numbers was 466. The appreance of Hanji was widely varied by blending(mixing) with other materials and various effects, pleating, crumpling, twisting and so on were achieved. The dress silhouette and form transformation of Hanji was very easy. Detailed points those are frill, pleats, gather, bow, paper casting, pin tuck for wedding dress were able to express easily. Hanji wedding dress has the natural texture because of natural properties of Hanji and that is echo friendly products.

• 한국지반공학회논문집
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• 제23권11호
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• pp.15-26
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• 2007

L. A. 마모율 시험은 건설용 골재의 강도를 확인하기 위한 방법으로 주로 석산의 모암을 대상으로 시행하여 왔다. 본 연구는 경상분지 퇴적암이 집중 분포되어 있는 25 지점에서 지질학적 특성을 대표할 수 있는 324 브록의 시료를 채취하여 L. A. 마모율시험으로 각종 공학지수(일축 압축강도, 압열 인장강도, 탄성계수, 점하중 강도지수, Schmidt 해머 반발지수)를 추정하기 위한 실험을 시행하여 회귀 분석법으로 서로간의 상관성을 확인한 결과, 상호간 좋은 상관관계가 있음을 확인하였다. 이 방법이 다른 공학지수를 추정함에 손색이 없으므로 이후에도 많은 활용이 있기를 기대한다.

• 대한화학회지
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• 제56권5호
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• pp.597-602
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• 2012

본 연구는 triacetoxyvinlysilane을 첨가제로 사용하여 교차결합제인 EGDMA (ethylene glycol dimethacrylate)와 HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), MA (methacrylic acid) 그리고 개시제인 AIBN (azobisisobutyronitrile)과 함께 공중합 하였다. 생성된 고분자의 물리적 특성을 측정한 결과, 함수율 35.63~32.44%, 굴절률 1.4382~1.4480, 가시광선 투과율 89.0~92.5%, 인장강도는 0.346~0.674 kgf를 나타내었다. 기본 모노머 조합에 triacetoxyvinlysilane을 첨가한 조합과 1%의 hexamethylene diisocyanate를 첨가하여 중합한 조합의 물성을 비교한 결과 hexamethylene diisocyanate 1%를 첨가하여 중합한 렌즈의 인장강도가 더 큰 값을 나타내었다. 본 실험결과로 볼 때 생성된 공중합체는 내구성 및 인장강도가 우수한 안의료용 렌즈 재료로 사용될 수 있을 것으로 판단된다.