• 한국기계가공학회지
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• 제17권5호
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• pp.8-15
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• 2018

Films with special properties (e.g., water-repellent films, optical films, anti-reflection films, and flexible films) are referred to as functional films. Recently, there has been interest in fine patterning methods for film fabrication. In particular there have been many studies that use a UV nanoimprint process involving a UV curing method. In this paper, a polymer film was fabricated by the UV nanoimprint process with a micro-pattern, and its durability was evaluated by a wear test and a nano-indentation test. The film mechanical properties (such as coefficient of friction, hardness, and modulus of elasticity) were measured. Moreover, the choice of PUA type resin used in the UV nanoimprint process was confirmed to impact the durability of the thin film. Despite making the polymer film samples using the same method and PUA type resin, different coefficient of friction, hardness, and modulus of elasticity values were obtained. PUA 4 resin had the most favorable coefficient of friction, hardness, and modulus of elasticity. This material is predicted to produce a high durability functional film.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.173-178
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• 2000

New prediction model is investigated estimating splitting tensile strength and modulus of elasticity with curing temperature and aging. New prediction model is based on the model which was proposed to predict compressive strength, and splitting tensile strength and modulus of elasticity calculated by this model are compared with experimental values. New prediction model well estimated splittinge tensile strength and elastic modulus as well as compressive strength.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.101-111
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• 2005

본 연구에서는 철근콘크리트의 압축부재에 배근되는 횡방향 철근의 구속효과와 축방향 철근비에 따른 탄성계수의 변화를 검토하였으며, 이를 바탕으로 철근비를 고려한 구조해석의 필요성을 제시하고자 하였다. 기존의 실험자료를 이용하여 철근콘크리트 압축부재에 대한 수정탄성계수 계산식을 제안하였다. 제안된 탄성계수를 적용한 구조물에 대한 해석을 실시하여 구조물의 거동에 어느 정도 영향을 미치는 파악하였는데, 철근비를 고려한 단면과 철근비를 고려하지 않은 단면에서 기둥과 보의 휨모멘트 크기에 상당한 차이가 발생함을 확인하였다. 풍하중 같은 횡방향 하중이 지배적인 경우에도 기둥의 철근비를 고려한 경우와 그렇지 않은 경우는 수평변위와 모멘트와 축력 등의 부재력에 큰 차이를 보였다. 따라서 철근콘크리트 구조물의 구조해석 시 현재 실무에서 일부 사용되는 방법에는 부재력의 과소평가 또는 과대평가의 가능성이 있으며, 이러한 문제점을 최소화하는 대안으로 본 연구에서 제시한 철근비를 고려한 수정탄성계수의 적용이 합리적인 것으로 판단된다.

• 한국건설순환자원학회논문집
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• 제3권3호
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• pp.206-211
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• 2015

최근에 활발히 연구되어지고 있는 UHPC의 경우, 강섬유 혼입량에 의해서 인장강도가 절대적으로 영향을 받는 이유로 본 논문에서는 압축강도, 강섬유량 등을 변수로 하여 압축강도, 탄성계수 및 인장강도 등을 실험적으로 구한 후, 그 결과를 분석하였다. 실험결과에 의하면, 압축강도와 탄성계수 및 인장강도는 비례관계로 상당한 상관성을 가지는 것으로 나타났으며, 섬유혼입률에 따른 압축강도와 인장강도의 관계 역시는 비례관계의 상관성을 가지는 것으로 나타났다. 탄성계수의 경우, 실험결과와 현행 국내 설계기준 식의 차이는 그다지 크지 않은 것으로 나타나, 기존의 설계기준 식을 준용하여도 UHPC 탄성계수 평가에는 큰 문제가 없을 것으로 예상된다. 한편 인장강도의 경우, 현행 설계기준에서 제시되지 않은 이유로 비선형 회귀분석을 실시하여 섬유혼입률을 고려한 인장강도 식을 제안하였으며, 제안된 식은 좋은 상관성을 보이는 것으로 나타났다.

• 한국화재소방학회논문지
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• 제29권1호
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• pp.1-6
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• 2015

본 연구에서는 충격반향기법을 이용하여 화해를 입은 고강도 콘크리트의 화재손상정도를 평가하였다. 100 MPa급의 고강도 콘크리트 시편을 제조하여 $100{\sim}800^{\circ}C$의 고온에 2시간 동안 노출한 후 충격반향기법의 응답스펙트럼을 이용하여 시편의 탄성파 속도를 측정하였으며, 이를 이용하여 동탄성계수를 산출하였다. 이후 직접 압축강도 실험을 통해 시편의 잔존압축강도와 정탄성계수를 측정하였다. 실험결과, 노출되는 온도가 높을수록 탄성파의 속도, 동탄성계수, 잔존압축강도, 정탄성계수가 저하되는 경향을 나타냈으며, 탄성파 속도와 압축강도, 동탄성계수와 정탄성계수는 선형적인 상관관계를 나타냈다. 따라서 충격반향기법을 이용하여 화해를 입은 고강도 콘크리트의 화재손상정도를 평가하는 것이 가능하다고 판단된다.

• Geomechanics and Engineering
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• 제17권3호
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• pp.247-252
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• 2019

Modulus of deformation of soil is an essential parameter used for design analysis of foundations, despite its importance; little attention is paid to developing empirical models for predicting the sensitivity of deformation moduli to other parameters that obtained from the pressuremeter tests. Various methods of analysis used to predict the horizontal at rest pressure from pressuremeter testing ($P_o$), these values showed distinctive variations, five methods used to evaluate the values of horizontal at rest pressure, these values been used to evaluate the modulus of elasticity using three methods of analysis. The values of modulus showed distinctive increase when the values of horizontal at rest pressure increase for the same pressuremeter test, these increases may reach to 65%. This sensitivity of the moduli to values of horizontal lead the author to propose some reliable methods of analysis for both the horizontal at rest pressure and the modulus of deformation from pressuremeter testing.

• Journal of the Korean Wood Science and Technology
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• 제22권1호
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• pp.20-27
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• 1994

Water repellent preservative (WRP) treated and untreated, small-sized specimens prepared from semiwater resistant, water resistant, and tegofilm-overlaid plywood were exposed to outdoor weathering for one year. Exterior durability of specimens was evaluated on the basis of changes in dynamic modulus of elasticity, degree of delamination, modulus of elasticity, modulus of rupture, and glueline shear strength. Among untreated specimens, tegofilm-overlaid plywood showed the best outdoor durability, and durability between semiwater resistant and water resistant plywood was similar. Although WRP treatment increased the durability of all types of plywoods, the effect of treatment on the increase in durability for semi water resistant plywood was not distinct. Accordingly, it can be concluded that semi water resistant plywood, which is used for temporary construction such as concrete formwork in our country, can not be inadequate for exterior use, regardless of WRP treatment. The bending strength and glueline shear strength of untreated water resistant plywood measured after weathering for one year did not exceed the minimum value specified by Korean Standard (KS), thereby the outdoor use of water resistant plywood was not desirable without WRP treatment. Exterior durability between treated water resistant plywood and untreated tegofilm-overlaid plywood was very similar. This result suggests that if an exposed plywood surface is treated with WRP regularly water resistant plywood can be used for temporary construction. This suggestion, however, needs to be investigated. In summary, semiwater resistant plywood cannot be used for temporay construction regardless of WRP treatment. Water resistant plywood can be used only with WRP treatment. Comparing the cost of tegofilm-overlaid plywood to costs of water resistant plywood and WRP treatment, however, it can be concluded that use of tegofilm-overlaid plywood for temporay constrution is strongly suggested from the point of view of both outdoor durability and costs.

• Structural Engineering and Mechanics
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• 제34권3호
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• pp.285-300
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• 2010

The two-dimensional deformation of a homogeneous, isotropic thermoelastic half-space with voids with variable modulus of elasticity and thermal conductivity subjected to thermomechanical boundary conditions has been investigated. The formulation is applied to the coupled theory(CT) as well as generalized theories: Lord and Shulman theory with one relaxation time(LS), Green and Lindsay theory with two relaxation times(GL) Chandrasekharaiah and Tzou theory with dual phase lag(C-T) of thermoelasticity. The Laplace and Fourier transforms techniques are used to solve the problem. As an application, concentrated/uniformly distributed mechanical or thermal sources have been considered to illustrate the utility of the approach. The integral transforms have been inverted by using a numerical inversion technique to obtain the components of displacement, stress, changes in volume fraction field and temperature distribution in the physical domain. The effect of dependence of modulus of elasticity on the components of stress, changes in volume fraction field and temperature distribution are illustrated graphically for a specific model. Different special cases are also deduced.

• 한국농공학회논문집
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• 제48권2호
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• pp.59-66
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• 2006

This study is performed to evaluate freezing and thawing properties of polypropylene fiber reinforced eco-concrete using soil, natural coarse aggregate, soil compound and polypropylene fiber. The mass loss ratio is decreased with increasing the content of natural coarse aggregate and soil compound, but it is increased with increasing the content of polypropylene fiber. The ultrasonic pulse velocity, dynamic modulus of elasticity and durability factor are increased with increasing the content of natural coarse aggregate and soil compound, but it is decreased with increasing the content of polypropylene fiber. The mass loss ratio, ultrasonic pulse velocity, dynamic modulus of elasticity and durability factor are $1.49{\sim}3.32%,\;1,870{\sim}2,465\;m/s,\;77X10^2{\sim}225X10^2\;MPa\;and\;84.6{\sim}92.8$ after freezing and thawing 300 cycles, respectively. These eco-concrete can be used for environment-friendly side walk and farm road.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.731-734
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• 2005

Crushed sand is blended in order to investigate the quality changes and characteristics of concrete with variation of blend ratio of crushed sand (50, 60, 70, 80, 90, $100\%$). Slump and air content were measured to investigate properties of fresh concrete, and unit weight, compressive strength and modulus of elasticity in age of 7, 28, 60, 90, 180 days were measured to investigate properties of hardened concrete. Compressive strength, unit weight and modulus of elasticity were increased as time goes by and they are expected to keep on increasing in long-term age as well. As a result of measuring compressive strength and modulus of elasticity in age of 7, 28, 60, 90, 180days, compressive strength was highest when it is $70\%$ of blended ratio.