• Membrane Journal
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• v.10 no.1
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• pp.19-29
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• 2000

To estimatc mutual diffusion coefficient for the analysis of mass transfer phenomena in polymer/solvent system, two models are proposed and the equations are derived. The estimates of mutual diffusion coefficients are obtained by two models suggested in this work and compared with and experimental data and Vrentas-Duda's. Vrentas-Duda's self diffusion coefficient was used for the mutual diffusion coefficient. Derivative of chemical potential on solvent was derived and used using original UNIFAC-FV and modified UNIFAC-FV. However, Vrentas-Duda's equation for mutual diffusion coefficient contains Flory-Huggins parameter x. For the derivative of chemical potential term, Vrentas-Duda assumed that parameter x was constant and independent of temperatures and concentrations The assumption is one of shortcoming in vrentas-Duda's mutual diffusion coefficient. New methods proposed in this work do not have such assumptions and simplifications. For the solvent of cyclohexane, n-pentane, and n-hexane in PIB(polyisolbutylene) and PMS-BR (poly(p-methylstyrene-co-isobutylene), new methods well correlate the experimental data at various temperatures and concentrations, and predicted the experimental data much better than Vrentas-Duda's for the PIB/toluene system. It is shown that new methods are excellent tools for correlating mutual diffusion coefficient data in polymer/solvent system over wide ranges of temperature and concentration without any assumptions or simplifications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.355-364
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• 2010

Filiform hairs that respond to movements of the surrounding medium are the mechanoreceptors commonly found in arthropods and vertebrates. In these creatures, the filiform hairs function as a sensory system for raider detection. Parametric analyses of the motion response of filiform hairs are conducted by using a mathematical model of an artificial flow sensor to understand the possible operating ranges of a microfabricated device. It is found that the length and diameter of the sensory hair are the major parameters that determine the mechanical sensitivities and responses in a mean flow with an oscillating component. By changing the hair length, the angular displacement, velocity, and acceleration could be detected in a wide range of frequencies. Although the torques due to drag and virtual mass are very small, they are also very influential factors on the hair motion. The resonance frequency of the hair decreases as the length and diameter of the hair increase.

• Journal of Korean Home Economics Education Association
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• v.24 no.4
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• pp.105-116
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• 2012

The purpose of this study was to investigate the effects of body appearance satisfaction(BAS) and the self-esteem on the obesity stress(OS). A survey sample drawn from the total of 664 middle school students(324 of females and 340 of males) were analyzed with the suggested conceptual model by employing the latent variables such as BAS and OS. By using the AMOS statistical program, we found that the conceptual model fitted well with the data set and paths in the model significantly predicted the OS. The middle schoolers' BAS had significant direct effects on the OS and self-esteem as well as a indirect effect via self-esteem on the OS. Self-esteem had a significant direct effect on the OS which was larger than the total effects from BAS on OS. Therefore, self-esteem could be buffered the negative influences from the BAS on the OS.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.361-368
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• 2014

In order to investigate the effect of CGT on atopic dermatitis, various anti-inflammatory factors were studied. In-vitro, inflammatory mediators, such as MTT and nitric oxide and ROS were detected after the addition of LPS with or without CGT in RAW 264.7 cells. In-vivo, in order to verify the effectiveness of CGT in atopic dermatitis animal model, its role in inflammation factors and histological changes were observed in NC/Nga mice. CGT showed cell viability of 100% or higher in all concentration in RAW 264.7 cells. CGT inhibited LPS-induced productions of inflammatory mediators nitric oxide and antioxidant activity reactive oxygen species production in RAW 264.7 cells. CGT treated group showed significant decrease in serum of the expression of IL-$1{\beta}$, IL-6 and TNF-${\alpha}$ by 53%, 43% and 57% respectively. And CGT treated group showed decrease in serum of the expression of IgE by 56% respectively. Also, infiltration of adipocytes into skin was suppressed and the thickness of epidermis and dermis were relatively decreased in the CGT treated group. As a result, CGT has an anti-inflammatory effects in NC/Nga mouse. Thus, these results suggested a beneficial effect of CGT in treatment with Atopic dermatitis and inflammatory.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.317-324
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• 2015

The design of anchorage zone in a post-tensioned member has been started from the evaluation of the ultimate resisting capacity as well as the maximum bursting stress developed, and a lot of design codes including AASHTO and PTI describe their design equations to determine the bearing strength of concrete at the anchorage zone. However, these equations usually give conservative results because their derivation is based on the simple anchorage with a wide bearing plate in the surface without any additional consideration for the load transfer mechanism through transverse ribs on the anchorage. To assess the influence of geometric parameters related to the transverse ribs on the resisting capacity of anchorage block, experiments and analysis are conducted. After verifying the validity of numerical model conducted through correlation studies between experimental and analytical results, parametric studies with changes in the transverse ribs are followed and design recommendations for the anchorage block are suggested from the numerical results obtained.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.537-549
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• 2001

The effect of partially restrained(PR) connections and the uncertainties in them on the reliability of steel frames subjected to seismic loading is addressed. A stochastic finite element method(SFEM) is proposed combining the concepts of the response surface method(RSM), the finite element method(FEM), the first-order reliability method (FORM), and the iterative linear interpolation scheme. The behavior of PR connections is captured using moment-relative rotation curves, and is represented by the four-parameter Richard model. For seismic excitation, the loading, unloading, and reloading behavior at PR connections is modeled using moment-relative rotation curves and the Masing rule. The seismic loading is applied in the time domain for realistic representation. The reliability of steel frames in the presence of PR connections is calculated considering all major sources of nonlinearity. The algorithm is clarified with the help of an example.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.183-195
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• 2003

In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived. The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free nitration control for the beam structures with bonded plate-tyPe Piezoelectric sensors and actuators is proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.743-750
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• 2019

Most of the water supply facilities that use rivers as sources do not have monitoring facilities such as precipitation and stream flow measurement, and there is no judgment standard for drought response such as water intake control in river flow during dry season. In addition, it was confirmed that local government officials, who deal with actual drought work, have limitations in applying the drought index (SPI, PDSI, etc.) and diffusion models that have been proposed so far in advance. Therefore, in this study, the drought prediction system was constructed to determine the number of water-intake available days using SWAT (Soil and Water Assessment Tool) and the water supply network from the intake source to the beneficiary area, suggesting the drought spreading time and space.

• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.481-491
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• 2020

The development of agricultural land at Saemangeum has required a significant increase in agricultural water use. It has been well acknowledged that salinity plays a critical role in the farming system. Therefore, a systematic study in salinity is necessary to better manage agricultural water. This study aims to develop a stochastic salinity simulation model that simultaneously simulates salinities obtained from different layers. More specifically, this study proposed a two-stage Autoregressive Exgeneous (ARX) model within a hierarchical Bayesian modeling framework. We derived posterior distributions of model parameters and further used them to obtain the predictive posterior distribution for salinities at three different layers. Here, the BIC values are used and compared to determine the optimal model from a set of candidate models. A detailed discussion of the model is provided.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.71-80
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• 2016

This study is based on the previous research which proved that "seeking convenience", "seeking low-cost" and "pleasures of shopping" are the major shopping motivation of online shopping. Research is conducted by using the trust as mediator, purchase intention as dependent variable. Also, differences between Chinese and Vietnamese consumers are applied in analysis of the model. The results were as follows: First, "seeking low-cost" and "pleasures of shopping" have positive effects on trust. Second, all shopping motivation have positive effect on purchase intention. Third, the trust has positive effect on purchase intention. Fourth, consumers' shopping motivation have significant difference in trust and purchase intention according to Chinese and Vietnamese consumers. The results of this study presented the strategic implications for operators at online shopping area.