• 한국식품과학회지
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• 제29권5호
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• pp.932-938
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• 1997

Changes in viscosity and dynamic theological properties of Job's-tears were measured by Bohlin dynamic tester as a function of moisture, and measurement was performed within a linear viscoelastic range. The result of the shear stress vs shear rate of Job's-tears at different moisture contents $(50{\sim}75%)$ was applied to mathematical models and Herschel-Bulkley model showed the highest correlation coefficient. Lower moisture content (55%) produced higher yield stress and consistency index, but lower flow behavior index, whereas higher moisture content showed reverse effects. Job's-tears with $50{\sim}70%$ moisture contents showed a higher storage modulus (G') than loss modulus (G') at all frequencies, showing a higher concentrated polymer characteristics. However, higher moisture content (>75%) showed crossover point between G' and G', and frequency dependency. As the moisture content was increased, the amount of viscoelastic properties such as G', G', complex viscosity decreased during heating, and initial temperature and miximum value of viscoelastic properties shifted to higher temperatures, representing the moisture-dependence of Job's-tears upon theological properties.

• Advanced Composite Materials
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• 제17권3호
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• pp.191-214
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• 2008

Polypropylene/layered silicate nanocomposites containing maleic anhydride grafted polypropylene were prepared by melt compounding and their rheological behavior was investigated in shear flow. Transient and steady shear flows were simulated numerically by using the K-BKZ integral constitutive equation along with experimentally determined damping functions under dynamic oscillatory and step strain shear flows. Nonlinear shear responses were predicted with the K-BKZ constitutive equation using two different damping functions such as the Wagner and PSM models. It was observed that PP-g-MAH compatibilized PP/layered silicate nanocomposites have stronger and earlier shear thinning and higher steady shear viscosity than pure PP resin or uncompatibilized nanocomposites at low shear rate regions. Strong damping behavior of the PP/layered silicate nanocomposite was predicted under large step shear strain and considered as a result of the strain-induced orientation of the organoclay in the shear flow. Steady shear viscosity of the pure PP and uncompatibilized nanocomposite predicted by the K-BKZ model was in good agreement with the experimental results at all shear rate regions. However, the model was inadequate to predict the steady shear viscosity of PP-g-MAH compatibilized nanocomposites quantitatively because the K-BKZ model overestimates strain-softening damping behavior for PP/layered silicate nanocomposites.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권1호
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• pp.64-69
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• 2006

Due to the inherent nonlinear nature of Electro-rheological (ER) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the nonlinear damping force model is made to identify the properties of the ER damper using higher order spectrum. The higher order spectral analysis is used to investigate the nonlinear frequency coupling phenomena with the damping force signal according to the sinusoidal excitation of the damper. Also, this paper presents an inverse model of the ER damper, i.e., the model can predict the required voltage so that the ER damper can produce the desired force for the requirement of vibration control of vehicle suspension systems. The inverse model is constructed by using a multi-layer perceptron neural network. A quarter-car suspension model is considered in this paper for analysis and simulation. Simulation results show that the proposed inverse model of ER damper can obtain control voltage of ER damper for required damping force.

• 대한기계학회논문집
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• 제11권2호
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• pp.205-213
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• 1987

본 논문에서는 비압축 선형 점탄성재료를 원통체로 모델화하여 열하중에 대한 거동을 점유적 시간증분과정을 적용하여 수치해를 제시하고 원통체를 제작실험하여 변 형과 비파괴검사를 통해 측정하여 비교검토하였다. 또한 이론적 수치해와 시편과의 안전율을 각 파괴기준(failure criteria)에 적용하여 비파괴검사결과와 비교하였다.

• 한국식품저장유통학회지
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• 제19권6호
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• pp.841-848
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• 2012

모시죽의 가용성 고형물 함량은 7.40-11.60 brix, pH는 6.0-6.6 사이에서 변화하는 것을 알 수 있었다. 모시죽의 amylose함량은 가수량에 의해 유의적인 영향을 받았으며 가수량이 증가할수록 현저하게 감소하는 것으로 나타났다. 점성은 가수량이 증가할수록 급격하게 떨어지는 것을 보여 주었으나, 모시분말은 죽의 점성 특성에 영향을 미치지 못하였다. 퍼짐성은 가수량이 증가할수록 현저하게 증가하는 경향을 보여주었으며, 이는 점성이 증가할수록 퍼짐성은 떨어진다는 사실과 일치된 결과를 보여주었다. 모시 첨가량이 증가할수록 밝기는 현격히 감소하는 것으로 조사되었으며 가수량의 변화는 밝기에 거의 영향이 없는 것으로 나타났다. 모시분말 첨가량은 적색도를 감소시키는 것으로 조사되었으나 황색도는 모시분말 첨가비를 증가시킬수록 크게 증가하는 것으로 나타났다. 모시죽의 제조조건에서 가수량은 물성특성에 모두 유의적으로 영향을 미치는 것으로 분석되었으나 모시분말 첨가비율은 유의성이 인정되지 않아 설정된 범위 내에서는 물성에 대한 영향이 크지 않는 것으로 평가되었다.

• 산업식품공학
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• 제21권2호
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• pp.167-173
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• 2017

본 연구에서는 고유의 자색 안토시아닌을 함유하고 있는 PFPP를 이용하여 매쉬드 포테이토를 제조하고 이의 물리화학적 특성을 확인하였다. PFPP와 전지분유, 덱스트린을 혼합하여 ready-to-eat (RTE) 매쉬드 포테이토 제품을 제조하기 위하여 세 구성 성분의 최적 혼합비를 도출하고자 혼합물 실험방법을 이용하였다. 다양한 배합비에서 매쉬드 포테이토의 색도, 안토시아닌 함량, 유변학적 특성의 차이를 관찰하였으며 PFPP와 전지분유의 배합비에 따라 매쉬드 포테이토의 구조가 변화하여 다른 유변학적 gel 특성을 나타내었다. PFPP의 함량은 주로 적색도와 안토시아닌 함량에 큰 영향을 미쳤으며, 전지분유의 함량은 전지분유의 친수성 및 수용성 특성에 의하여 유변학적 특성의 변화에 영향을 미쳤다. 매쉬드 포테이토의 유변학적 특성 및 다양한 배합비에 따른 특성은 모델링을 통하여 구조적 및 성분에 따른 경향을 정량적으로 나타낼 수 있었다. 본 연구를 통하여 적색도와 안토시아닌의 함량을 최대로 함유하면서 유변학적 특성은 시판되는 매쉬드 포테이토와 유사한 고품질의 기능성 매쉬드 포테이토의 최적 배합비는 PFPP 90.49%, 전지분유 4.86%, 덱스트린 4.65%임을 도출하였다.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• Preventive Nutrition and Food Science
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• 제18권1호
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• pp.45-49
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• 2013

This study was carried out to determine a possibility of adding Corni fructus extract (CFE) into yogurt for improving the neutraceutical properties of yogurt and the effects of adding CFE (2~6%, v/v) on the physicochemical and sensory properties of the products during a 15-day storage period at $4^{\circ}C$. Incorporation of CFE into the yogurt samples resulted in a significant pH reduction and a significant increase in titratable acidity. When evaluating the color of the yogurt, the $L^*$-values were not significantly influenced by CFE supplementation; however, the $a^*$- and $b^*$-values significantly increased with the addition of CFE during storage. The power law and Casson models were applied to assess the flow behavior of CFE-added yogurt samples. The magnitudes of apparent viscosity (${\eta}_{a,100}$), consistency index (K), and yield stress (${\sigma}_{oc}$) for 4~6% CFE yogurt samples were significantly greater than those for the control, indicating that CFE can be used as a thickening agent for yogurt. The sensory test revealed that addition of CFE (2~4%) to yogurt did not significantly affect the overall scores, but the overall preference score for 6% CFE yogurt was significantly decreased. Based on the data obtained from the present study, we concluded that the concentrations (2~4%) of CFE could be used to produce a CFE-added yogurt without the significantly adverse effects on the physicochemical and sensory properties.

• Computers and Concrete
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• 제15권4호
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• pp.687-707
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• 2015

A finite element computer code for short-term analysis of steel-concrete composite structures is extended to study long-term effects under service loads, in the present work. Long-term effects are important in engineering design because they influence stress and strain distribution of the structural system and therefore contribute to the increment of deflections in these structures. For creep analysis, a rheological model based on a Kelvin chain, with elements placed in series, was employed. The parameters of the Kelvin chain were obtained using Dirichlet series. Creep and shrinkage models, proposed by the CEB FIP 90, were used. The shear-lag phenomenon that takes place at the concrete slab is usually neglected or not properly taken into account in the formulation of beam-column finite elements. Therefore, in this work, a three-dimensional numerical model based on the assemblage of shell finite elements for representing the steel beam and the concrete slab is used. Stud shear connectors are represented for special beam-column elements to simulate the partial interaction at the slab-beam interface. The two-dimensional representation of the concrete slab permits to capture the non-uniform shear stress distribution in the horizontal plane of the slab due to shear-lag phenomenon. The model is validated with experimental results of two full-scale continuous composite beams previously studied by other authors. Results are given in terms of displacements, bending moments and cracking patterns in order to shown the influence of long-term effects in the structural response and also the potentiality of the present numerical code.

• Design & Manufacturing
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• 제16권3호
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• pp.9-15
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• 2022

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.