• YAKHAK HOEJI
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• v.40 no.4
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• pp.411-417
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• 1996

Epidermal growth factor(EGF), a potential healing agent for wounds and burns, has been formulated to topical gels with the hydrophilic polymers, Carbopol 934P. Physicochemical c haracteristics of the aqueous gels were evaluated by rheological properties and pH changes on storage. The gels were relatively stable at $4^{\circ}C$ and room temperature showing no changes in pH for two weeks, and revealed the rheogram of shear thinning plastic flow with the yield values in the range of 40 to 70dyne/$cm^2$. In vivo healing effects of different gel formulations have been compared with water-soluble and oleaginous ointments in full-thickness wound mouse model. The gel systems resulted in better wound healing effects than the other ointments. Furthermore, liposomal Carbopol gel has been developed by the addition of EGF-containing liposomal suspension into the Carbopol gel. The enhanced wound healing effects have been observed in the liposomal gel system, compared to the other gels and conventional ointments.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.215-219
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• 2001

The resonators made of piezoelectric crystals such as a quartz crystal are widely used. Their frequency-temperature characteristics are of primary importance for their applications to the frequency control devices. The characteristics estimation is useful for determining their design parameters. In the present paper, several types of resonators are numerically analyzed. The numerical solutions are made using 3-D Finite Element Modeling, and the results are compared with the theoretical values whenever they are available. To demonstrate the validity of the present numerical approach, the application is made to the analysis of the plates with some well-established cutting angles. For the resonator stable with temperature change, the cutting angle is important in which the temperature coefficient of the first order is chosen to be zero. The rotated Y-cut plates in thickness-shear mode are considered. The equivalent circuit representation is often used fur describing the characteristics at the electrical terminals which enables the circuit analysis including the effect of temperature change by using the circuit simulators. The equivalent circuit parameters are obtained by fitting the admittance-frequency curve from the finite element analysis.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.3
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• pp.15-21
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• 1999

The flow characteristics around KRISO 300K VLCC double-body model have been experimentally investigated in a closed-type subsonic wind tunnel. The local mean velocity and turbulence statistics including turbulent intensity. Reynolds shear stress and turbulent kinetic energy were measured using a x-type hot-wire probe. The measurements were carried out at several transverse stations of the stern and near wake regions. The surface flow was visualized using on oil-film technique to see the flow pattern qualitatively. The flow in the stern and near wake region revealed complicated three-dimensional flow characteristics. The VLCC model shows a hook-shaped wake structure behind the propeller boss in the main longitudinal vortex region. The thin boundary layer at midship was increased gradually in thickness over the stern and evolved into a full three-dimensional turbulent wake.

• Steel and Composite Structures
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• v.2 no.5
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• pp.379-396
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• 2002

The paper describes the mechanical behavior of short concrete-filled steel tube (CFT) columns with circular section. The efficiency of the steel tube in confining the concrete core depending on concrete strength and the steel tube thickness was examined. Fifteen columns were tested to failure under concentric axial loading. Furthermore, a mechanical model based on the interaction between the concrete core and the steel tube was developed. The model employs a volumetric strain history for the concrete, characterized by the level of applied confining stress. The situation of passive confinement is accounted for by an incremental procedure, which continuously updates the confining stress. The post-yield behavior of the columns is greatly influenced by the confinement level and is related to the efficiency of the steel tube in confining the concrete core. It is possible to classify the post-yield behavior into three categories: strain softening, perfectly plastic and strain hardening behavior. The softening behavior, which is due to a shear plane failure in the concrete core, was found for some of the CFT columns with high-strength concrete. Nevertheless, with a CFT column, it is possible to use high-strength concrete to obtain higher load resistance and still achieve a good ductile behavior.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.245-256
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• 2012

The objective of this study is to investigate the effect of the openings on the structural behavior of SC walls. The test parameters were with or without the reinforcing of openings and sleeve thickness. The common failure showed that the crack in the concrete progressed with the plate's local buckling between the shear connectors. The failure of the openings showed that the vertical wall of the sleeve buckled toward the opening inside. The plate buckling load showed a similar value with or without the sleeve of the opening, respectively. However, the maximum compressive strength of the specimen without the opening was higher than that of specimen with the opening.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.232-239
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• 2005

Recently geosynthetics that can be constructed on soft ground have been used for reinforcement and separation in various ways. Through laboratory model tests and numerical analysis, in this study, estimated the suitability of cable elements and appropriate input factors considering loading effect in modeling of geosynthetics. First, in laboratory model tests, geosynthetics were constructed on the clay, and covered with the thickness, 7.5cm of sand mat. And then static and dynamic model tests were performed measuring loading, settlement, ground lateral displacement, and displacements of geosynthetics, but, for cyclic loading, bearing capacity increased linearly with stiff slop because cyclic loading with constant cyclic pressure compacted the ground. Numerical analysis were performed with FLAC 4.0 2D using Mohr-Coulomb and Modified Cam-Clay models, and they compared with the results of model tests. Cable elements of FLAC in modeling geosynthetics couldn't consider the characteristics of geosynthetics that increase shear strength between geosynthetics and clay according to the loading increase. Therefore, in this study, appropriate equation that can consider loading effects in Cable elements was proposed by Case Study.

• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.63-68
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• 2011

This paper presents an optimization procedure for performance improvement of a tunnel ventilation jet fan. Optimization techniques based on response surface approximation (RSA) are employed to improve the aerodynamic performance of a tunnel ventilation jet fan. For numerical analysis, three-dimensional Renolds- averaged Navier-Stokes (RANS) equations with shear stress transport turbulence model are discretized by using finite volume approximations and solved on hexahedral grids to evaluate the total efficiency at the operating condition as the objective function. Four geometric variables defining the meridional length and the thickness profile at the hub and shroud in the jet fan rotor are selected as design variables for the numerical optimization. The results of the numerical optimization show that the total efficiency of the optimized model is significantly improved in comparison with the base model.

• Fibers and Polymers
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• v.2 no.4
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• pp.196-202
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• 2001

In order to investigate the relationship between subjective sensation for fabric sound and touch and the objective measurements, eight different apparel fabrics were selected as specimens. Sound parameters of fabrics including level pressure of total sound (LPT), level range (ΔL), and frequency differences (Δf) and mechanical properties by Kawabata Evaluation System (KES) were obtained. For subjective evaluation, seven aspects of the sound (softness, loudness, pleasantness, sharpness, clearness, roughness, and highness) and eight of the tough (hardness, smoothness, fineness, coolness, pliability, crispness, heaviness, and thickness) were rated using semantic differential scale. Polyester ultrasuede was evaluated to sound softer and more pleasant while polyester taffeta to sound louder and rougher than any other fabrics. Wool fabric such as worsted and woolen showed similar sensation for sound but differed in some touch sensation in that woolen was coarseast, heaviest, and thickest in touch. In the prediction model for sound sensation, LPT affected positively subjective roughness and highness as well as loudness, while ΔL was found as a parameter related positively with softness and pleasantness. Touch sensation was explained by some of mechanical properties such as surface, compressional, shear, and bending properties implying that a touch sensation could be expressed by a variety of properties.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.951-961
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• 2001

The present article presents an extension to the computational model for spray/wall interaction and liquid film processes that has been dealt with in the earlier studies (Lee and Ryou, 2000a). The extensions incorporate film spread due to impingement forces and dynamic motion induced by film inertia to predict the dynamic characteristics of wall films effectively. The film model includes the impingement pressure of droplets, tangential momentum transfer due to the impinging droplets on the film surface and the gas shear force at the film surface. Validation of the spray/wall interaction model and the film model was carried out for non-evaporative diesel sprays against several sources of experimental data. The computational model for spray/wall interactions was in good agreement with experimental data for both spray radius and height. The film model in the present work was better than the previous static film model, indicating that the dynamic effects of film motion should be considered for wall films. On the overall the present film model was acceptable for predication of the film radius and thickness.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.157-165
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• 1997

The strength level of welded joint in room temperature and elevated temperature up to $600^{\circ}C$ was investigated in 250 and 300 grade 18% Ni maraging steel sheet welded with electron beam. The results obtained in this study are as follows; 1. Optimum welding heat input was 600J/cm in 1.0mm thickness and the room temperature tensile strength, joint efficiency of welded joint treated with optimum aging condition were found to be about 166kg/$mm^2$, 95% in 250 grade, 189kg/$mm^2$, 92% in 300 grade maraging steel sheet, respectively. 2. Tensile strength of welded joint in room temperature increased slightly by aging after repeated solution heat treatment, but the fracture mode showed a shear. 3. Joint efficiency at a temperature between $540^{\circ}C$and $600^{\circ}C$ found to be about 72% to 55%, but the joint efficiency exceeded about 90% below $300^{\circ}C$. 4. The fracture occurred in most weld metal, and the fracture surface showed a shallow dimple.