• Advances in materials Research
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• v.6 no.4
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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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• v.73 no.5
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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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• v.57 no.1
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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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• v.3 no.1
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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.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.197-206
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• 2006

Vibration of string is transmitted to the front plate through bridge to cause resonance of the instrument body in viol family string instruments. Therefore. the properties. geometrical shape. and positioning of the bridge are expected to have some effect on the sound color. In this study the strain and the stress in the bridge. and the force exerted on the top plate by the bridge as the string vibrates the bridge in cello are calculated through simulation based on the theory of elasticity. The modes of vibration and the characteristic frequencies are also found. Furthermore. the effect of geometric shape of bridge on sound color is studied in terms of frequency response. The results of this study show that the vibration characteristics of bridge is quite complex and the properties and the geometrical shape of bridge have significant effect on sound color, and therefore. the sound color of a cello can be controlled by changing the geometrical shape of bridge.

• Journal of Technology Innovation
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• v.19 no.3
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• pp.57-83
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• 2011

We suggested industry-specific priorities of R&D investment with R&D investment elasticity to GDP calculated from the ripple effect of 28 large-sized industry R&D investment, using a Computable General Equilibrium(CGE) Model. Priority orders apply to only 12 industries, because 16 industries with less than 1% of total investment have been excluded. First, R&D investment elasticity to GDP says that priorities are ordered as Basic metal products, Chemicals, drugs and medicines, Food, beverages and tobacco products, Electronic and electrical equipment, Transportation equipment, Precision instruments, Electrictity, gas, steam and water supply, General machinery and equipment, Communications and broadcasting, Construction, Other services, and Real estate and business services. These priorities show the status quo of Korean industry structures well. The GDP growth rate to 2030 year reference equilibrium, which is an auxiliary index, says a similar priority to results from R&D investment elasticity to GDP. In the end, two criteria of priority order can be functioned as a good index for National Science and Technology Commission deciding what industry to invest and what budget to allocate.

• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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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.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.843-850
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• 2010

The dynamic modulus of elasticity of concrete can be determined nondestructively using impact echo test as prescribed in KS F 2437. The fundamental longitudinal frequency of the concrete cylinders with free-free boundary condition was estimated by the wavelet transform theory. The advantage of the wavelet transform over either a pure spectral or temporal decomposition of the signal is that the features of the pertinent signals can be characterized in the time-frequency plane. For the concrete mix design utilized in this study, no significant difference between the dynamic and the static moduli of elasticity was observed. This was contrary to the perceived general notion of having the dynamic modulus considerably higher than the static modulus. It has been shown that the modulus from static and dynamic by impact echo test are comparable to each other fairly well, when the effect of strain level was properly taken into account. In this experimental test, it was shown that the dynamic modulus is approximately equal to the tangent modulus at $1{\times}10^{-4}$ strain level.

• Journal of Environmental Policy
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• v.8 no.3
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• pp.139-162
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• 2009

This paper confirms previous results indicating that the expenditure elasticity of demand for polluting goods plays an important role in achieving efficiency gains from tax reforms. Moreover, this paper finds that the results of the tax reforms depend not only on the size of the expenditure elasticity for the polluting goods but also on the relative size of the expenditure elasticities between polluting goods and clean goods. It also shows that in order to enhance the overall tax efficiency by the environmental tax reform, the expenditure elasticity of demand for clean goods should be larger than that of polluting goods. The result implies the following policy suggestion: When the tax authority considers green tax reforms, the expenditure elasticities should not be neglected to achieve gains in the overall efficiency of the tax system.

• Proceedings of the SCSK Conference
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• 2003.09b
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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.