• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.19-25
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• 2004

The linear analysis for the balance of linear momentum of a structure is relatively easy to perform, but the error becomes large when the structure experiences large deformation. Therefore, the material and geometric nonlinearity need to be considered for the precise calculations in that case. The plastic flow of a ductile steel-like metal mainly transforms its dissipated mechanical energy into heat, which transfers under the first and second law of thermodynamics. This heat increases the temperature of the material and the strength of the material decreases accordingly, which affects mechanical behavior of the given structure. This paper presents a finite-strain thermo-elasto-plastic steel model. This model can handle large deformation and thermal load simultaneously, which is common during earthquake periods. Two 3-dimensional finite element analyses verify this formulation.

• Coupled systems mechanics
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• v.7 no.6
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• pp.649-668
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• 2018

In this paper, we present a numerical model for fluid-structure interaction between structure built of porous media and acoustic fluid, which provides both pore pressure inside porous media and hydrodynamic pressures and hydrodynamic forces exerted on the upstream face of the structure in an unified manner and simplifies fluid-structure interaction problems. The first original feature of the proposed model concerns the structure built of saturated porous medium whose response is obtained with coupled discrete beam lattice model, which is based on Voronoi cell representation with cohesive links as linear elastic Timoshenko beam finite elements. The motion of the pore fluid is governed by Darcy's law, and the coupling between the solid phase and the pore fluid is introduced in the model through Biot's porous media theory. The pore pressure field is discretized with CST (Constant Strain Triangle) finite elements, which coincide with Delaunay triangles. By exploiting Hammer quadrature rule for numerical integration on CST elements, and duality property between Voronoi diagram and Delaunay triangulation, the numerical implementation of the coupling results with an additional pore pressure degree of freedom placed at each node of a Timoshenko beam finite element. The second original point of the model concerns the motion of the outside fluid which is modeled with mixed displacement/pressure based formulation. The chosen finite element representations of the structure response and the outside fluid motion ensures for the structure and fluid finite elements to be connected directly at the common nodes at the fluid-structure interface, because they share both the displacement and the pressure degrees of freedom. Numerical simulations presented in this paper show an excellent agreement between the numerically obtained results and the analytical solutions.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.179-184
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• 2021

Stratum corneum known as a skin barrier, which maintains water in skin, is the outer layer of the skin. Natural moisturizing factors (NMF) are one of the constituents in stratum corneum and amino acids are the highest components among NMF. In this study, we designed stearic acid-based solid lipid nanoparticles (SLNs) for improved skin penetration of serine (Ser). Ser-capsulated SLN was manufactured by double-melting emulsification method. The mean particle size and zeta potential of SLNs were 256.30 ~ 416.93 nm and -17.60 ~ -35.27 mV, respectively. The higher the degree of hydrophobicity or hydrophilicity of emulsifiers, the smaller the particle size and the higher the stability and capsulation rate. In addition, skin penetration was conducted using SkinEthic^TM RHE which is one of the reconstructed human epidermis models. The results of Ser penetration demonstrated that all SLNs enhanced than serine solution. The amount of enhanced Ser penetration from SLNs were approximately 4.1 ~ 6.2 times higher than that from Ser solution. Therefore, Ser-loaded SLN might be a promising drug delivery system for moisturizing formulation in cosmeceutical.

• Journal of the Korean Chemical Society
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• v.41 no.12
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• pp.653-660
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• 1997

Silicone rubber-matrix membranes doped with tetradecyltrimethylammonium chloride (TDTMACl) are used to enhance electrode performance for chloride measurements in physiological samples. The optimized membrane formulation incorporates 95.4 wt% silicone rubber and 4.6 wt% TDTMACl, and its pH response is negligible in the range of pH 6-10. The TDTMACl-doped silicone rubber membrane exhibits sub-Nernstian response to chloride from 10 to 300 mM (-37.5 mV/decade), but its selectivities for chloride over other anions are remarkably enhanced: KpotCl,NO3=1.3, KpotCl,I=2.0, KpotCl,Sal=0.8, KpotCl,SCN=2.0 and KpotCl,ClO4=0.8. Furthermore, since the silicone rubber-matrix membrane exhibits better adhesion to the solid surface than do PVC membranes, the lifetime of the coated-wire type membrane electrode is greatly improved. The response properties toward chloride and salicylate for solid-state sensor are not significantly changed after at least 35 days of use.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.206-222
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• 2015

This work uses different finite element approaches to the free vibration analysis of reinforced shell structures, and a simplified model of a typical launcher with two boosters is used as an example. The results obtained using a refined one-dimensional (1D) beam model are compared to those obtained with commercial finite element software. The 1D models that are used in the present work are based on the Carrera Unified Formulation (CUF), which assumes a variable kinematic displacement field over the cross-sections of the beam. Two different sets of polynomials that correspond to Taylor (TE) or Lagrange (LE) expansions were used. The analyses focused on three reinforced structures: a stiffened panel, a reinforced cylinder and the complete structure of the launcher. The frequencies and natural modes obtained using one-dimensional models are compared to those obtained from classical finite element analysis. The classical FE models were built using a beam-shell or solid elements, and the results indicate that the refined beam models can in fact be used to investigate the behavior of very complex reinforced structures. These models can predict the shell-like modes that are typical of thin-walled structures that cannot be detected using classical beam models. The refined 1D models used in the present work provide results that are as accurate as those from solid FE models, but the 1D models have a much lower computational cost.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.4112-4112
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• 2001

The feasibility of NIR spectroscopy as a quick and nondestructive method for quality control of uniformity of coating thickness of pharmaceutical tablets was investigated. Near infrared spectra of a set of pharmaceutical tablets with varying coating thickness were measured with a diffuse reflectance fiber optic probe connected to a Broker IFS 28/N FT-NIR spectrometer. The challenging issues encountered in this study included: 1. The similarity of the formulation of the core and coating materials, 2. The lack of sufficient calibration samples and 3. The non-linear relationship between the NIR spectral intensity and coating: thickness. A peak at 7184 $cm^{-1}$ was identified that differed for the coating material and the core material when M spectra were collected at 2 $cm^{-1}$ resolution (0.4 nm at 7184 $cm^{-1}$). The study showed that the coating thickness can be analyzed by polynomial fitting of the peak area of the selected peak, while least squares calibration of the same data failed due to the lack of availability of sufficient calibration samples. Samples of coal powder and solid pieces of coal were analyzed by FT-NIR diffuse reflectance spectroscopy with the goal of predicting their ash content, percentage of volatile components, and energy content. The measurements were performed on a Broker Vector 22N spectrometer with a fiber optic probe. A partial least squares model was constructed for each of the parameters of interest for solid and powdered sample forms separately. Calibration models varied in size from 4 to 10 PLS ranks. Correlation coefficients for these models ranged from 86.6 to 95.0%, with root-mean-square errors of cross validation comparable to the corresponding reference measurement methods. The use of FT-NIR diffuse reflectance measurement techniques was found to be a significant improvement over existing measurement methodologies in terms of speed and ease of use, while maintaining the desired accuracy for all parameters and sample forms.(Figure Omitted).

• Computers and Concrete
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• v.20 no.3
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• pp.319-327
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• 2017

Studying the structural behavior of prestressed segmented girders is quite important due to the large use this type of solution in viaducts and bridges. Thus, this work presents a nonlinear three-dimensional structural analysis of an externally prestressed segmented concrete girder through the Finite Element Method (FEM), using a customized ANSYS platform, version 14.5. Aiming the minimization of the computational effort by using the lowest number of finite elements, a new viscoelastoplastic material model has been implemented for the structural concrete with the UPF customization tool of ANSYS, adding new subroutines, written in FORTRAN programming language, to the main program. This model takes into consideration the cracking of concrete in its formulation, being based on fib Model Code 2010, which uses Ottosen rupture surface as the rupture criterion. By implementing this new material model, it was possible to use the three-dimensional 20-node quadratic element SOLID186 to model the concrete. Upon validation of the model, an externally prestressed segmented box concrete girder that was originally lab tested by Aparicio et al. (2002) has been computationally simulated. In the discretization of the structure, in addition to element SOLID186 for the concrete, unidimensional element LINK180 has been used to model the prestressing tendons, as well as contact elements CONTA174 and TARGE170 to simulate the dry joints along the segmented girder. Stresses in the concrete and in the prestressing tendons are assessed, as well as joint openings and load versus deflection diagrams. A comparison between numerical and experimental data is also presented, showing a good agreement.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.2
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• pp.19-26
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• 2008

This study has been carried out to investigate the dynamic characteristics of RC slabs. For this purpose, the 20-node solid element has been used to discretize the RC slabs into two parts of concrete and rebar. The material non-linearity considering elasto-visco plastic model and the smeared crack model have been adopted in the finite element formulation. The applied load can handle step load, load intensity of harmonic load, area of distributed load and frequency. The frequency of harmonic load has an significant effect on dynamic behaviour in terms of displacement. As the frequency is increased, the effect of load amplitude is more serious. Especially, if the frequency of harmonic load exceeds 30 Hz, it is noted that the displacement by harmonic load is greater than that by step load. In case of harmonic load, the damping effect shows no certain tendency with respect to frequency of load. In details, the damping is effective when the frequency of harmonic load is 2 Hz, but there is no consistent tendency according to damping ratio. The dynamic response when the frequency of harmonic load is 3 Hz shows same result for undamped case as well as for damped case with 5% damping ratio. It is also noted that we can get the largest deflection for damped case with 1% damping ratio. However, there is not any damping effect when the frequency of harmonic load is greater than 4 Hz.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.11a
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• pp.89-92
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• 2000

Non-aqueous tape casting of LTCC with PVB binder has been studied in a continuous tape casting machine. The aim of the study was to evaluate this type of system in the different Binder/Plasticizer and solid content compositions. Each four slurry compositions were used in the experiments with varied binder/plasticizer and solid content. All the slurries gave good quality tapes with smooth surfaces without blisters or pinholes. The highest mechanical properties was obtained for the B/P=3.0, powder content 70vol% composition from 52 ${\mu}{\textrm}{m}$ green tapes, a tensile strength of 4.6 MPa and a linear extension of 29.5%

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.1
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• pp.15-22
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• 2018

Alpha-pinene is an organic compound that possesses antibiotic and anti-parasitic activities. In this study, we developed a layered nanocomposite to combat against Miamiensis avidus which causes scuticociliatosis in the olive flounder Paralichthys olivaceus. We used a solid-solid reaction to develop the layered nanocomposite, incorporating-pinene ($C_{10}H_{16}$) into organically modified montmorillonite. We used cetyltrimethylammonium cations as the interlayered modifier for the adsorption of hydrophobic pinene molecules. The X-ray diffraction patterns of the nanocomposite structure showed that the basal spacing increased from $9.6{\AA}$ to $30.4{\AA}$. Interestingly, the fraction of ${\alpha}$-pinene released remained constant for a long period of time (228 h) due to the layered nature of the nanocomposite. Additionally, optical microscopic images of the treated scuticociliatids revealed that their cells were lysed, and this effect increased with the increasing concertration of ${\alpha}$-pinene. Histopathological assessment of ${\alpha}$-pinene nanocomposite-treated olive flounder gills revealed no significant morphological changes, even at the highest concentration of the ${\alpha}$-pinene. The nanocomposite has several advantages, including easy handling, high solubility, low toxicity, and the easy formulation of granules or powder, which improve the pesticidal activity of ${\alpha}$-pinene. Collectively, our results suggest that ${\alpha}$-pinene nanocomposite may be a useful treatment against scuticociliatosis.