• Geomechanics and Engineering
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• v.32 no.3
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• pp.255-270
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• 2023

One of the main parameters that affect the design of suction caisson-supported offshore structures is uplift behavior. Pull-out of suction caissons is profoundly utilized as the offshore wind turbine foundations accompany by a tensile resistance that is a function of a complex interaction between the caisson dimensions, geometry, wall roughness, soil type, load history, pull-out rate, and many other parameters. In this paper, a parametric study using a 3-D finite element model (FEM) of a single offshore suction caisson (SOSC) surrounded by saturated soil is performed to examine the effect of some key factors on the tensile resistance of the suction bucket foundation. Among the aforementioned parameters, caisson geometry and uplift loading as well as the difference between the tensile resistance and suction pressure on the behavior of the soil-foundation system including tensile capacity are investigated. For this purpose, a full model including 3-D suction caisson, soil, and soil-structure interaction (SSI) is developed in Abaqus based on the u-p formulation accounting for soil displacement (u) and pore pressure, P.The dynamic responses of foundations are compared and validated with the known results from the literature. The paper has focused on the effect of geometry change of 3-D SOSC to present the soil-structure interaction and the tensile capacity. Different 3-D caisson models such as triangular, pentagonal, hexagonal, and octagonal are employed. It is observed that regardless of the caisson geometry, by increasing the uplift loading rate, the tensile resistance increases. More specifically, it is found that the resistance to pull-out of the cylinder is higher than the other geometries and this geometry is the optimum one for designing caissons.

• Wind and Structures
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• v.38 no.4
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• pp.261-275
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• 2024

Before performing an experimental study on the downburst-generated wave, it is necessary to examine the scale effects and corresponding corrections or compensations. Analysis of similarity is conducted to conclude the non-dimensional force ratios that account for the dynamic similarity in the interaction of downburst with wave between the prototype and the scale model, along with the corresponding scale factors. The fractional volume of fluid (VOF) method in association with the impinging jet model is employed to explore the characteristics of the downburst-generated wave numerically, and the validity of the proposed scaling method is verified. The study shows that the location of the maximum radial wind velocity in a downburst-wave field is a little higher than that identified in a downburst over the land, which might be attributed to the presence of the wave which changes the roughness of the underlying surface of the downburst. The impinging airflow would generate a concavity in the free surface of the water around the stagnation point of the downburst, with a diameter of about two times the jet diameter (D_jet). The maximum wave height appears at the location of 1.5D_jet from the stagnation point. Reynolds number has an insignificant influence on the scale effects, in accordance with the numerical investigation of the 30 scale models with the Reynolds number varying from 3.85 × 10⁴ to 7.30 × 10⁹. The ratio of the inertial force of air to the gravitational force of water, which is denoted by G, is found to be the most significant factor that would affect the interaction of downburst with wave. For the correction or compensation of the scale effects, fitting curves for the measures of the downburst-wave field (e.g., wind profile, significant wave height), along with the corresponding equations, are presented as a function of the parameter G.

• 전자공학회논문지 IE
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• v.44 no.2
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• pp.8-13
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• 2007

This paper aims to analyze the characteristics of ITO which are caused by variation of plasma condition to fabricate the OLED of high efficiency. We treated $N_2$ gas and $O_2$ gas plasma on the surface of the ITO by changing their RF plasma power into 100 W, 200 W, 400 W and by changing their 9as pressure into 12 mTorr, 120 mTorr. The work function of ITO that plasma treatment was done by using $N_2$ gas had value of $4.88{\sim}5.07\;eV$, and that by using $O_2$ gas, $4.85{\sim}4.97 eV$. The characteristics of the ITO were most efficient in the $N_2$ gas plasma with the RF power of 200W and gas pressure of 120 mTorr. The rms roughness of ITO surface is the value from AFM image. In this case, ITO obtained $25.2\;{\AA}$ and $30.5\;{\AA}$ in the $N_2$ and $O_2$ gas plasma respectively when it had the RF power of 200 W. But ITO that didn't have plasma treatment was $44.5{\AA}$. The variation of ITO transmittance was almost not discovered by the change of $N_2$ gas and $O_2$ gas pressure.

• Journal of Korea Water Resources Association
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• v.37 no.7
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• pp.527-540
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• 2004

In order to investigate characteristics of the primary flow and the secondary currents in the meandering channel, laboratory experiments were conducted in the meandering channel made up of alterative bends haying 120。 arc angle. Experiments were performed in two types of cross-sections, a rectangular cross-section and a curved cross-section which was made to adopt a beta probability function. Three-dimensional velocity fields were measured using a micro-ADV. As the result of experiments, in case of the rectangular cross-section, the primary flow occurred taking the shortest course, which is similar to the result of previous researches. In case of the curved cross-section, the primary flow was expected to occur along the thalweg. but it occurred almost along the shortest way. This is considered due to effects of bottom roughness and sinuosity Not only a main cell but also a secondary cell of secondary currents were clearly shown by mean of the stream function. The secondary current intensity has the maximum value near the apex of the second bend for cases of both rectangular and curved cross-sections. However, the value of the secondary current intensity for the curved section is slightly larger than that for the rectangular cross-section. Also, in case of the rectangular cross-section, the higher the ratio of width to depth is, the larger the secondary current intensity is.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.482-487
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• 2016

Ultra-violet rays are very harmful to eye health care. The blocking of ultra-violet rays and a reduction of optical reflection in the visible light range, which is to increase the share of transmitted light, and avoid the formation of ghost images in imaging, are important for the applications of polymer eyeglasses lenses. In this study, the high-refractive index polymer lenses, n=1.67, were fabricated by injection-molded method with the xylene diisocyanate monomer, 2,3-bis-1-propanethiol monomer, and benzotriazol UV absorber (SEESORB 709) mixture. To reduce the reflection of the polymer lens surfaces, multi-layer anti-reflection (AR) coatings were coated for both sides of the polymer lens using an E-beam evaporation system. The optical properties of the UV blocking polymer lens were characterized using a UV-visible spectrometer. The material properties of the thin films, which were composed AR coating layers, refractive index, and surface roughness, were analyzed by ellipsometry and atomic force microscopy. As a result, the fabricated polymer lens perfectly blocked ultra-violet rays below 395 nm with a blocking rate greater than 99%.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.35 no.4
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• pp.63-74
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• 2022

Objectives : Skin aging is generally characterized by wrinkles, sagging, loss of elasticity roughness, pigmentation and dryness. This changes is caused by reducing the elements constituting the extracellular matrix contributing to the physiological properties of the skin, such as collagen fiber, elastic fiber, and hyaluronic acid. Adequate skin hydration is important to maintain normal skin function and reduce skin aging. The present study is objective to observe skin moisturizing effects of Unripe apple(UA, Immature fruit of Malus pumila Mill) in vivo and its underlying molecular mechanisms. Methods : ICR mice were orally administerd UA(100, 200 and 400mg/kg/day) for 8 weeks, and skin water contents and the expression of transforming growth factor (TGF)-𝛽1, ceramide, hyaluronan and collagen type I(COL1) were measured in dorsal back skin of the mice. Gene expression of hyaluronan synthase(HAS1, HAS2, HAS3), collagen synthase(COL1A1, COL1A2) and TGF-𝛽1 were also determined by realtime RT-PCR. Results : Skin water contents and the expression of TGF-𝛽1, ceramide, COL1 and hyaluronan were significantly increased in UA group(100, 200 and 400mg/kg/day) compared to vehicle control. The mRNA expression of HAS isoform(HAS1, HAS2, HAS3), COL1A1, COL1A2, and TGF-𝛽1 were also significantly increased by UA. Conclusions : UA has skin moisturizing effects and enhancement activities in skin function related components(COL1, hyaluronan, ceramide and TGF-𝛽1). These results suggested that UA can be a developing candidate for developing alternative skin protective agent or functional food ingredient.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.5-19
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• 2010

The purpose of this study is to figure out the effect of pressurized grouting on the pullout resistance and the group effect of the compression ground anchor by performing pilot-scale chamber tests and field tests. The laboratory tests are carried out for 3-types of soils which are abundant in the Korean peninsular. Experimental results showed that the enlargement of anchor diameters estimated from the cavity expansion theory matches reasonable well with that obtained from experiments. Moreover, the required injection time as a function of the coefficient of permeability of each soil type was proposed. A series of in-situ anchor pullout tests were also performed to experimentally figure out the effect of pressurized grouting on the pullout resistance. Experimental results also showed that the effect of the pressurized grouting is more prominent in a softer ground with smaller SPT-N value in all of the following three aspects: increase in anchor diameter; pullout resistance; and surface roughness. The pressurized grouting effect in comparison with gravitational grouting was found to be almost nil if the SPT-N value is more than 50. Based on experimental results, a new equation to estimate the pullout resistance as a function of the SPT-N value was proposed. And based on in-situ group anchor pullout tests results, a new group effect equation was proposed which might be applicable to decomposed residual soils which are abundant in the Korean peninsular.

• Korean Journal of Environment and Ecology
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• v.33 no.4
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• pp.472-480
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• 2019

Selection of the plant material for planting to reduce fine dust should comprehensively consider the visual characteristics, such as the shape and texture of the plant leaves and form of bark, which affect the adsorption function of the plant. However, previous studies on reduction of fine dust through plants have focused on the absorption function rather than the adsorption function of plants and on foliage plants, which are indoor plants, rather than the outdoor plants. In particular, the criterion for selection of fine dust reduction species is not specific, so research on the selection criteria for plant materials for fine dust reduction in urban areas is needed. The purpose of this study is to identify the priorities of eight indicators that affect the fine dust reduction by using the fuzzy multi-criteria decision-making model (MCDM) and establish the tree selection criteria for the urban planting to reduce fine dust. For the purpose, we conducted a questionnaire survey of those who majored in fine dust-related academic fields and those with experience of researching fine dust. A result of the survey showed that the area of leaf and the tree species received the highest score as the factors that affect the fine dust reduction. They were followed by the surface roughness of leaves, tree height, growth rate, complexity of leaves, edge shape of leaves, and bark feature in that order. When selecting the species that have leaves with the coarse surface, it is better to select the trees with wooly, glossy, and waxy layers on the leaves. When considering the shape of the leaves, it is better to select the two-type or three-type leaves and palm-shaped leaves than the single-type leaves and to select the serrated leaves than the smooth edged leaves to increase the surface area for adsorbing fine dust in the air on the surface of the leaves. When considering the characteristics of the bark, it is better to select trees that have cork layers or show or are likely to show the bark loosening or cracks than to select those with lenticel or patterned barks. This study is significant in that it presents the priorities of the selection criteria of plant material based on the visual characteristics that affect the adsorption of fine dust for the planning of planting to reduce fine dust in the urban area. The results of this study can be used as basic data for the selection of trees for plantation planning in the urban area.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.40 no.2
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• pp.195-201
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• 2014

Body fluid has been studied for diverse fields like Ringer's solutions, artificial joint fluids, cell growth culture media because it plays a crucial role in controlling body temperature and acts as a solvent for diverse metabolite processes in the body and delivery media of mineral, energy source, hormone, signal and drug from and to cell via blood or lymphatic vessel by osmotic pressure or active uptake. Stratum corneum containing extracellular lipids and NMF (natural moisturizing factor) absorbs atmospheric water residing outside of cells and utilize it to hydrate inside of their own. This process is related to skin barrier function. In this study, we conducted the cell viability test with Cell Bio Fluid $Sync^{TM}$, which mimicks body fluids including amino acids, peptides, and monosaccharides to strengthen skin barrier, and the clinical skin improvement test with cosmetics containing Cell Bio Fluid $Sync^{TM}$. In the cell viability test, HaCaT cell was treated with PBS for 3 hours, followed by the treatment of a cell culture medium (DMEM) and isotonic solution (PBS) and Cell Bio Fluid $Sync^{TM}$ for 3 hours each. Then, MTT assay and image analysis were conducted. In the clinical skin improvement test, twenty-one healthy women participated. Participants applied cosmetics containing Cell Bio Fluid $Sync^{TM}$ on their face for a week and evaluated the skin hydration, skin roughness, brightness and evenness. All measurements were conducted after they washed off their face and took a rest under the constant temperature ($22{\pm}2^{\circ}C$) and constant humidity conditions ($50{\pm}5%$) for 20 minutes. All the data were analyzed by SPSS (version 21) software program. Results showed that Cell Bio Fluid $Sync^{TM}$ improved both the cell viability and in vivo skin conditions such as skin hydration, roughness, brightness and evenness.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.83-94
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• 2009

The aim of this study was to investigate the shear bond strength between zirconia ceramic and resin cement according to various surface treatments. The surface of each zirconia ceramic was subjected to one of the following treatments and then bonded Rely X Unicem or Rely X ARC resin cement; (1) Rocatec system and $50{\mu}m$ surface polishing, (2) No treatment and $50{\mu}m$ surface polishing, (3) Rocatec system and $1{\mu}m$ surface polishing, (4) No treatment and $1{\mu}m$ surface polishing. Each of eight bonding group was tested in shear bond strengths by universal testing machine(Z020, Zwick, Ulm, Germany) with crosshead speed of 1mm/min. The results were as follows; 1. Rocatec treatment groups showed greater bonding strengths than No Rocatec groups. There was significant difference of among groups(P<0.001) 2. For Rocatec groups, $50{\mu}m$ surface roughness groups showed greater bonding strengths than $1{\mu}m$ surface roughness groups.(P<0.001) But for No Rocatec groups, There was no significant difference of among groups(P>0.05) 3. Rely X Unicem groups showed greater bonding strengths than Rely X ARC groups. There was significant difference of among groups(P<0.01) Within the conditions of this study, Rocatec treatment was an effective way of increasing zirconia bonds to a resin cement, even in the case of self-adhesive resin cement.