• Journal of the Korean Wood Science and Technology
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• v.14 no.2
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• pp.13-20
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• 1986

The effect of heat treatment on the dynamic viscoelasticity of the woods of Picea sitchensis and Paulownia coreana which have been for musical instruments was investigated. The treatment was made in a temperature range of 60-180$^{\circ}C$ for periods of 3 hours to 24 hours. The results obtained are summarized as follows: Moisture absorption decreased with increasing temperature. Dynamic Young's modulus decreased with increasing temperature and hours. Dynamic viscoelasticity decreased with increasing moisture content, but internal friction increased with increasing amount of moisture content.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.641-646
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• 2004

Statement of Problem. Temporary soft relining materials are used in a diverse clinical situations such as tissue conditioner, relining material, functional impression by varying its viscoelasticity. However, reproduction of consistent viscoelasticity has been not possible. Materials and methods. Considering setting mechanism of this material, this study has measured the effect of varying amount of void in dynamic viscoelasticity of soft relining material, with three different mixing methods. In each methods 10 specimens were made and subjected to dynamic viscoelastic test which were measured at specific times over period of 72 hours. Results. The analysis of the result shown that there was no statistically significant differences between different mixing methods. Conclusion. Different mixing methods had no effect over control of viscoelasticity of soft lining material. Further research is recommended for under similar oral environmental condition.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.67-73
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• 1995

This study was undertaken to investigate the effect of heat treatment on the dynamic viscoelasticity of three species of Phyllostachys bambusoides, Phyllostachys nigra var. henonis and Phyllostachys pubescens, grown in southern Korea. The bamboo was treated for 3~24 hours at $60{\sim}180^{\circ}C$, and then was treated in a climatic chamber for 3~48 hours at $40^{\circ}C$ and 95% relative humidity. The results obtained are summarized as follows : 1. Dynamic Young's modulus decreased with increasing temperature and duration of the heat treatment. 2. Internal friction decreased with increasing treatment duration. 3. Moisture absorption decreased with increasing temperature and duration of the heat treatment. 4. Dynamic viscoelasticity decreased, whereas internal friction slowly increased, with increasing moisture content.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.525-526
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• 2006

The products designed by human sensibility and ergonomics are given good impression. Especially the touch feeling on the human skin is very useful sensibility for quality of products. Elasticity and viscosity of human skin is very important element in product design based on ergonomics. In this paper, we describe a sophisticated method for measurement of dynamic viscoelasticity characteristics of human skin. For this measurement, we developed a measurement system assembled with load cell, actuator, amplifier and data acquisition system. The $MATLAB^{TM}$ is used to analyze the data and fit a approximation curves.

• Korean Journal of Food Science and Technology
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• v.35 no.6
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• pp.1022-1027
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• 2003

The effect of ${\beta}$-glucan, prepared from waxy barley, on the dynamic viscoelasticity of nonwaxy and waxy barley starch during gelatinization and gelation was studied. Although no significant effect was observed on waxy starch, there were drastic changes in the dynamic viscoelasticity of nonwaxy starch. The gelatinization onset temperature of nonwaxy starch shifted to a higher temperature and showed a drastic increase in storage modulus and loss modulus at the range of $80{\sim}90^{\circ}C$. During the gelation of nonwaxy starch, ${\beta}$-glucan increased the rate of gel formation and weakened the network of starch and amylose by prohibiting their association. Therefore, we proved that there was no specific interaction between amylose and ${\beta}$-glucan. The addition of ${\beta}$-glucan to waxy starch seemed to have no effect of waxy starch.

• The Korean Journal of Food And Nutrition
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• v.28 no.6
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• pp.1011-1018
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• 2015

The effects of mixing speed (3, 6 and 10 speed) and time (2, 5 and 10 min) on the dynamic viscoelasticity of dough and the baking properties of gluten-free rice bread were investigated. The specific gravity of the dough was not affected by the mixing speed and time before and after fermentation. The elasticity (G') and viscosity (G") of the dough increased and the tan ${\delta}$ (G"/G') decreased with higher mixing speeds and longer mixing times. The specific volume of the gluten-free rice bread was affected by the mixing time in response surface methodology (RSM). The hardness of the gluten-free rice bread showed a decreasing trend as the specific volume for the gluten-free rice bread increased. The appearance of the gluten-free rice bread was symmetrical at high mixing speeds and long mixing times. Overall results indicated that the quality of gluten-free rice bread could be improved by controlling the mixing speeds and mixing times for the dough.

• Advances in nano research
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• v.14 no.1
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• pp.45-65
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• 2023

This paper aimed to investigate the nonclassical size dependent free vibration behavior of regularly squared cutout viscoelastic nanobeams. The nonlocal strain gradient elasticity theory is modified and adopted to incorporate the viscoelasticity effect. The Kelvin Voigt viscoelastic model is adopted to model the linear viscoelastic constitutive response. To explore the influence of shear deformation effect due to cutout, both Euler Bernoulli and Timoshenko beams theories are considered. The Hamilton principle is utilized to derive the dynamic equations of motion incorporating viscoelasticity and size dependent effects. Closed form solutions for the resonant frequencies for both perforated Euler Bernoulli nanobeams (PEBNB) and perforated Timoshenko nanobeams (PTNB) are derived considering different boundary conditions. The developed procedure is verified by comparing the obtained results with the available results in the literature. Parametric studies are conducted to show the influence of the material damping, the perforation, the material and the geometrical parameters as well as the boundary and loading conditions on the dynamic behavior of viscoelastic perforated nanobeams. The proposed procedure and the obtained results are supportive in the analysis and design of perforated viscoelastic NEMS structures.

• Advances in aircraft and spacecraft science
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• v.7 no.3
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• pp.215-228
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• 2020

As is shown in the paper, the Koltunov-Rzhanitsyn singular kernel of heredity (when constructing mathematical models of the dynamics problem of the hereditary theory of viscoelasticity) adequately describes real mechanical processes, best approximates experimental data for a long period of time. A mathematical model of the problem of the flutter of viscoelastic plates moving in a gas with a high supersonic velocity is given. Using the Bubnov-Galerkin method, discrete models of the problem of the flatter of viscoelastic plates flowed over by supersonic gas flow are obtained. A numerical method is developed to solve nonlinear integro-differential equations (IDE) for the problem of the hereditary theory of viscoelasticity with weakly singular kernels. A general computational algorithm and a system of application programs have been developed, which allow one to investigate the nonlinear dynamic problems of the hereditary theory of viscoelasticity with weakly singular kernels. On the basis of the proposed numerical method and algorithm, nonlinear problems of the flutter of viscoelastic plates flowed over in a gas flow at an arbitrary angle are investigated. In a wide range of changes in various parameters of the plate, the critical velocity of the flutter is determined. It is shown that the singularity parameter α affects not only the oscillations of viscoelastic systems, but the critical velocity of the flutter as well.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.3
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• pp.29-41
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• 1998

The ultraviolet(UV)-curable materials wildly have been used as a ink and coating materials. A according to measure UV polymerization phase separation of acryl groups 2,3,4-functional monomer, a few experiments were performed gel fraction, dynamic viscosity of alkyd resin blend system. Dependence of photoiniator concentration and various monomer, alkyd resin content investigated structural changes of films cured by UV irradiation. Curing rate measured UV irradiation under $25^{\circ}C$, cell gap 7cm and film thickness 100${\mu}{\textrm}{m}$. In results, it was through that the viscoelastic properties of films cured with increasing the ratios of monomer/alkydresin contents are network polymer in properties such as viscoelasticity.

• The Korean Journal of Rheology
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• v.9 no.3
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• pp.97-102
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• 1997

내피로성은 기계적 구조물로 사용되는 고분자재료에는 반드시 필요한 성질이며, 피 로거동은 재료특유의 비선형 동적 점탄특성과 아주 밀접한 관계가 있다. 본 연구에서는 피 로과정에서의 비선형 동적 점탄특성을 정량적, 연속적으로 측정할수 있는 시험 기기와 가해 준 변형에 대한 응답 응력파의 기본 응력파(선형적 응답)로부터의 차이를 직접 측정하여 이 를 규격화한 비선형 점탄성파라미터, NVP(Nonlinear Viscoelastic Parameter)라 명명한 새 로운 평가방법을 개발하였다. 그리고 고밀도 폴리에틸렌(HDPE) 배향물을 사용하여 그 평가 방법의 타당성을 조사한 결과 피로과정에서의 비선형동적 점탄특성을 나타내는 NVP가 증 가함에 따라 재료의 피로수명은 감소하였다. 따라서 NVP가 고분자재료의 내피로성을 평가 하는 척도로서 사용가능하다는 사실이 증명되었다. 또한 각 고조파 성분에대해 조사한 결과 인장형 피로시험양식에서는 고체입자 분산계의 전단변형에서 나타난 비선형 점탄성의 결과 와는 달리 2차 성분의 크기가 가장컸으며 NVP에의 기여도도 가장 크게 나타났다. 이는 변 형양식의 차이에 따른 결과를 볼수 있다.