• Advances in materials Research
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• 제6권4호
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• pp.329-341
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• 2017

The challenge of replacing conventional plastics with biodegradable composite materials has attracted much attention in product design, particularly in the tensile-related areas of application. In this study, fibres extracted from oil palm empty fruit bunch (EFB) were treated and utilized in reinforcing polyester matrix by hand lay-up technique. The effect of fibre loading and combined influence of alkali and silane treatments on porosity and water absorption parameters, and its correlation with the tensile behaviour of composites was analyzed. The results showed that tensile strength decreased whilst modulus of elasticity, water absorption and porosity parameters increased with increasing fibre loading. The composites of treated oil palm EFB fibre exhibited improved values of 2.47 MPa to 3.78 MPa for tensile strength; 1.75 MPa to 2.04 MPa for modulus of elasticity; 3.43% to 1.68% for porosity and 3.51% to 3.12% for water absorption at respective 10 wt.% fibre loadings. A correlation between porosity and water absorption with tensile behavior of composites of oil palm EFB fibre and positive effect of fibre treatment was established, which clearly demonstrate a connection between processing and physical properties with tensile behavior of fibre composites. Accordingly, a further exploitation of economic significance of oil palm EFB fibres composites in areas of low-to-medium tensile strength application is inferred.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.565-584
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• 2020

The nonlinear thermo-electro-elastic buckling behavior of viscoelastic nanoplates under magnetic field is investigated based on nonlocal elasticity theory. Employing nonlinear strain-displacement relations, the geometrical nonlinearity is modeled while governing equations are derived through Hamilton's principle and they are solved applying semi-analytical generalized differential quadrature (GDQ) method. Eringen's nonlocal elasticity theory considers the effect of small size, which enables the present model to become effective in the analysis and design of nano-sensors and nano actuators. Based on Kelvin-Voigt model, the influence of the viscoelastic coefficient is also discussed. It is demonstrated that the GDQ method has high precision and computational efficiency in the buckling analysis of viscoelastic nanoplates. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as electric voltage, small scale effects, elastomeric medium, magnetic field, temperature effects, the viscidity and aspect ratio of the nanoplate on its nonlinear buckling characteristics. It is explicitly shown that the thermo-electro-elastic nonlinear buckling behavior of viscoelastic nanoplates is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of viscoelastic nanoplates as fundamental elements in nanoelectromechanical systems.

• Structural Engineering and Mechanics
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• 제57권1호
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• pp.179-200
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• 2016

In this paper the differential transformation method (DTM) is utilized for vibration and buckling analysis of nanotubes in thermal environment while considering the coupled surface and nonlocal effects. The Eringen's nonlocal elasticity theory takes into account the effect of small size while the Gurtin-Murdoch model is used to incorporate the surface effects (SE). The derived governing differential equations are solved by DTM which demonstrated to have high precision and computational efficiency in the vibration analysis of nanobeams. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of thermal loading, small scale and surface effects, mode number, thickness ratio and boundary conditions on the normalized natural frequencies and critical buckling loads of the nanobeams in detail. The results show that the surface effects lead to an increase in natural frequency and critical buckling load of nanotubes. It is explicitly shown that the vibration and buckling of a nanotube is significantly influenced by these effects and the influence of thermal loadings and nonlocal effects are minimal.

• International Journal of Korean Welding Society
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• 제3권1호
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• pp.39-44
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• 2003

The welded specimens were made by butt welding of the 2 wires of 50mm length using the pulsed YAG laser. The laser welded wires were tested for investigating the shape memory effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was Investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

• 한국음향학회지
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• 제25권5호
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• pp.197-206
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• 2006

비올족 현악기에서 현의 진동은 브릿지에 의해 전판에 전달되어서 악기 몸통을 공명시킨다. 따라서 브릿지의 재질, 기하학적 형상, 설치 위치 등이 음색에 영향을 미치게 된다. 본 연구에서는 첼로에서 현에 의해 변위가 가해질 때 브릿지 내부의 변형, 응력, 그리고 브릿지 다리에 의해 전판에 미치는 힘을 탄성학적으로 해석하고, 브릿지의 고유진동모드와 고유진동주파수 등을 구하였다. 또, 브릿지의 형상이 음색에 미치는 영향을 주파수 응답의 관점에서 측정하였다. 본 연구의 결과는 첼로에서 브릿지의 진동특성은 대단히 복잡하고, 그 재질, 형상 등이 음색에 큰 영향을 미치며, 따라서 브릿지의 형상을 변화시킴으로써 첼로의 음색을 조정하는 것이 가능함을 실험적으로 보였다.

• 기술혁신연구
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• 제19권3호
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• pp.57-83
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• 2011

본 연구에서는 CGE(Computable General Equilibrium)모형을 이용하여 28개 산업별 R&D투자액의 GDP 파급효과를 추정한 뒤, 그 결과로써 GDP의 R&D투자탄력성을 계산하여 산업별 R&D 투자 우선순위를 제시하였다. 우선순위는 28개 대분류 산업 중 전체 연구 개발투자에서 차지하는 비중이 1% 미만인 16개 산업을 제외한 12개 산업에 대해서만 적용해 보았다. 먼저 GDP의 R&D투자 탄력성에 근거한 우선순위는 제1차 금속제품, 화학제품, 음식료품, 전기 및 전자기기, 수송장비, 금속제품, 정밀기기, 전력 가스 및 수도, 일반기계, 통신 및 방송, 건설, 사회 및 기타 서비스, 부동산 및 사업 서비스 순이었다. GDP의 R&D투자탄력성에 근거한 순위설정은 비교적 우리나라 산업들의 현황을 잘 보여주고 있는 것으로 판단된다. 보조 지표인 2030년 기준 균형 대비 GDP 증가율에 근거한 우선순위 역시 판정기준으로 유사한 결과를 보여주었다. 결국 두 개의 우선순위 기준은 국가과학기술위원회의 R&D예산투자방향 및 기준 설정과 주요 사업별 예산배분 방향에 좋은 판정기준으로 활용될 수 있음을 보여주었다.

• 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.

• 콘크리트학회논문집
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• 제22권6호
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• pp.843-850
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• 2010

콘크리트의 동탄성계수는 KS F 2437에 규정된 바와 같이 탄성파 비파괴시험인 충격반향기법에 따라 측정할 수 있다. 자유단 경계조건에서의 콘크리트 공시체에 대한 종방향 고유진동수를 웨이블릿 변환이론을 적용하여 평가하였다. 웨이블릿 변환은 순수한 스펙트럼 해석뿐만 아니라 시간영역에서의 분해신호를 추출하는데 있어 시간-주파수 공간에서의 실제 신호형상을 제공하는 장점을 갖고 있다. 이 실험에 적용된 배합비를 갖는 콘크리트의 경우에 동탄성계수와 정탄성계수의 평가 결과가 큰 차이를 나타내지 않아 일반적으로 알려져 있는 정도는 아닌 것으로 판단된다. 충격반향기법에서 결정된 동탄성계수와 정적시험에서 결정된 정탄성계수는 변형률 정도를 고려하여 비교하면 비교적 서로 잘 일치하며 이 실험에서의 동탄성계수는 평균변형률 $1.04{\times}10^{-4}$에서의 접선탄성계수와 같은 것으로 평가되었다.

• 환경정책연구
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• 제8권3호
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• pp.139-162
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• 2009

본 논문은 환경세의 이중배당가설과 환경세 부과대상 재화의 지출탄력성에 대한 연구이다. 본 연구의 결론은 환경세 정책의 효율성 개선효과가 환경세 부과대상 재화의 지출탄력성에만 의존하는 것이 아니라, 경제 내에 존재하는 다른 재화, 즉 환경세가 부과되지 않는 재화와의 상대적인 지출탄력성에도 영향을 받을 수 있음을 지적하고 있다. 본 연구결과는 향후 우리나라 환경세 정책추진에 있어 다음과 같은 시사점을 제시한다. 환경세 정책은 환경의 질적 개선을 최우선 목표로 추진됨이 바람직하지만, 만약 조세체계 전반에 걸친 효율성 개선까지 염두에 둔다면 부과대상 재화의 지출탄력성까지 함께 고려하는 것이 바람직하다는 점이다. 구체적으로 환경세 부과대상 재화를 선정함에 있어서 가급적 지출탄력성이 낮은 재화위주로 구성하는 것이 효율성 개선효과를 극대화할 수 있는 방안이다.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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• pp.253-267
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• 2003

Inositol and phytic acic extracted from rice bran were investigated for applying cosmetics. Skin lotions containing 0∼3.0wt% inositol and 0∼1.5wt% phytic acid were applied respectively, to the arm skins of 45 Asian women 20'-40's for 7 weeks. Improvement on moisture was evaluated. In addition, improvements on sebum, elasticity, and wrinkle were examined after applying placebo, Inositol and phytic acid-containing skin lotions for face, respectively. For 1.0 wt% inositol resulted in 19% increase of moisture. The wrinkle reduction and elasticity improved 12.4% and 17.0% on average, respectively. Applying 0.5wt% phytic acid resulted in 71.6% increase the moisture. Improvements on wrinkle and elasticity were 15.9% and 21.9% respectively. Applying inositol or phytic acid regardless of dry or oily, resulted in sebum value recovery to that of the normal skin after 2- 4 weeks. Inositol is inferior to phytic acid in improvenients of the skin, and phytic acid is not suitable to sensitive skin. So 0-0.5wt% of phytic acid were added to 1.0wt% inositol and similar experiments were carried out. In case of added 0.1wt% phytic acid, moisture increased 63.8% approximately. Improvements on elasticity and reduction on wrinkle were 17.2% and 17.4%, respectively. Both skin types were turned to normal skin type after 2 weeks. It could improve the skin condition when used inositol added phytic acid. The optimized concentration of phytic acid was 0.10wt% with 1.0wt% of inositol for synergic effect.