• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.701-704
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• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having influenced by groundwater movement, understanding of thermo hydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.00 1 are shaped circular, and the center is moved less than 5m to the groundwater flow direction in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.48-52
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• 2007

A lot of researches have been done in order to investigate the dynamic characteristics of the aerostatic porous bearing, most of them used analytical approaches and only a few used experimental approaches. However the experimental condition used in the previous experimental approaches was not realistic, where the porous bearing has been fixed and only the mass supported by the bearing was allowed to move vertically. The dynamic stiffness obtained by those experimental setups may be different with the real case where the mass and the bearing move together in horizontal direction. In this paper, the dynamic characteristics of the horizontally moving aerostatic circular porous air bearings are investigated by the experimental approach. The experimental apparatus was designed to realize its real operating condition used in most industrial applications. The experimental results were compared with the previous experimental ones.

• The Korean Journal of Ecology
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• 제14권3호
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• pp.327-343
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• 1991

Clonal growth and rhizome architecture of calmagrostis epigeios, were studied in a 15-year old coastal reclamed land. As c. epigeios patch grew from center to margin radially over time, concentric annuli were added. the radial increases of the mature patch were 80~130cm/yr. the patch ages of c. epigeios estimated by relationships between the diameter and is radial increament, were 1~6year old. There were the marked variations of density, phytomass, shoot height and inflorecence frequency with increasing age of rhizome system within the patch. the maximum performance occurred at 2-year-old concentric annuli of the patch. The growth phasic continuum with aging was divided into 5 grwth phases ; pioneer, building, matyre, senile and degenerate. The rhizome aging had a more significant effect on the inflorescence frequency than on the other attributes. new rhizomes tended to diverge from the direction of the parent ramet by sympodial growth. in a 1-year-old patch, average length of rhizome segment was 7cm, average number of internode was 6, and the tillering frequency was 27%. The tillering in the early stage resultd in the increase of shoot density and the producation of multibranching rhizome. as the result of that, circular patchwas formed in a year. The branching structure based on such facts was represented graphically in branching degree of 60 and 100. therefore, c. epigeios with clonal growth may establish and grow vigorously earlier than other glycophytes in high salt conditions such as the coastal reclaimed land.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.799-809
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• 2002

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

• Steel and Composite Structures
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• 제28권5호
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• pp.541-557
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• 2018

This paper presents the influence of carbon nanotubes (CNTs) waviness and aspect ratio on the vibrational behavior of functionally graded nanocomposite sandwich annular sector plates resting on two-parameter elastic foundations. The carbon nanotube-reinforced (CNTR) sandwich plate has smooth variation of CNT fraction along the thickness direction. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of Pasternak's elastic foundation coefficients, sandwich plate thickness, face sheets thickness and plate aspect ratio are investigated on the free vibration of the sandwich plates with wavy CNT-reinforced face sheets. The study is carried out based on three-dimensional theory of elasticity and in contrary to two-dimensional theories, such as classical, the first- and the higher-order shear deformation plate theories, this approach does not neglect transverse normal deformations. The sandwich annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free.

• Human Ecology Research
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• 제58권2호
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• pp.163-176
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• 2020

Longitudinal studies have shown mixed findings on the association between body image dissatisfaction and self-esteem among adolescents. This study examined the longitudinal, reciprocal influences between body image dissatisfaction and self-esteem among Korean pre- and early adolescents by using nationally representative longitudinal panel data from the Korean Youth Panel Study (KYPS). Analyses based on 2,230 participants indicated that girls' body image dissatisfaction was significantly higher than boys'. The trajectory of body image dissatisfaction increased sharply during pre- and early adolescence, but stabilized afterwards for both boys and girls. Self-esteem deteriorated rapidly initially, but began to recover as adolescent girls and boys matured. Structural equation modeling showed that reciprocal influences between body image dissatisfaction and self-esteem were detected for boys. Body image dissatisfaction among girls predicted self-esteem during the entire period, while the opposite direction from self-esteem to body image dissatisfaction emerged two years later. The present study found that, during pre- and early adolescence, body image dissatisfaction and self-esteem develop in a circular fashion by forming a vicious cycle. Implications for the development of intervention and prevention programs are discussed in consideration of age and gender.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.131-136
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• 2008

Three-dimensional characteristics of fluid flow and heat transfer around a wavy circular cylinder having sinusoidal variation in cross sectional area along the spanwise direction are numerically investigated using the immersed boundary method. The three different wavelengths of ${\pi}/4$, ${\pi}/3$ and ${\pi}/2$ and at the fixed wavy amplitude of 0.1 have been considered to investigate the effects of waviness on especially the forced convection heat transfer around a wavy cylinder when the Reynolds and Prandtl numbers are 300 and 0.71, respectively. The present computational results for a wavy cylinder are compared with those for a smooth cylinder. The time- and total surface-averaged Nusselt number for a wavy cylinder with is larger than that for a smooth cylinder, whereas that with ${\lambda}={\pi}/4$ and ${\pi}/3$ is smaller than that for a smooth cylinder. However, because the surface area exposed to heat transfer for a wavy cylinder is larger than that for a smooth cylinder, the total heat transfer rate for a wavy cylinder with different wavelengths of ${\lambda}={\pi}/4$, ${\pi}/3$ and ${\pi}/2$ is larger than that for a smooth cylinder.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.87-90
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• 2003

In Resin transfer molding (RTM), composite parts are produced by impregnation of a dry reinforcement with liquid matrix resin. Permeability is a key issue in this process. For thin parts, the resin flow in the thickness direction can be neglected. Therefore thin parts are considered as two-dimensional composites. However the resin flow through the thickness is important to thicker parts and we have to consider out-of-plane permeability. This work discusses a method to measure out-of-plane permeability. The flow rate and pressure drop across the porous media were measured. Also one dimensional form of Darcy's law is applied to calculate the out-of-plane permeability of various preforms. The flow is injected uniformly into layers of the preform. And a circular fiber mat with 6cm diameter was cut and flattened from cylindrical mandrel.

• 한국응용곤충학회지
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• 제33권1호
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• pp.33-38
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• 1994

점박이응애 알에 대한 긴털이리응애의 전반적 채식행동을 연구하였다. 먹이가 충분히 존재할 때, 긴털이리응애는 섭식-섭식후이도.휴식-탐색 등 일련의 과정을 반복햇을며, 각각의 시간 소비(평균$\pm$표준편차)는 6.83$\pm$1.73, 3.00$\pm$1.33, 93.57$\pm$30.19 분이었고 탐색시간은 9분에 가가웠다. 섭식후이동은 이동 속도가 느리고 (초속0.09mm)한쪽 방향으로연속하여 회전하는 범위제한적 탐색행동을 보였으며 이탕행동은 속도가 빠르고(초속 0.31mm) 반응면적의 가장자리를 따라 이동하는 특징을 보였고, 탐색행동은 중간의 특징을 보였다. 또한 긴털이리응애의 섭식위치는 집중분포를 따랐다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.414-417
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• 2008

We have extracted a surface deformation map of a part of Canisteo Peninsula on Amundsen Sea in West Antarctica by applying 4-pass DInSAR technique to two ERS-1/2 tandem pairs obtained on October 21-22, 1995 (diff-pair) and March 9-10, 1996 (topo-pair), and analyzed changes of glaciers, sea ice, ice shelves, and their kinematic interactions. We observed fast motion of glaciers pushing the adjoining sea ice. Some interferometric phases indicate the up-rise of sea ice of which type is thought to be land-fast ice to exert repulsive force against the pushing glacier. There were other glaciers and sea ice that moved to the same direction, suggesting that the sea ice in these regions was land-fast ice weakly harnessed to sea bottom or pack ice not harnessed at all. Several small circular fringes in ice shelves suggested that islands or seamounts on the bottom of ice shelves deterred the movement of ice shelves, resulting in the rise of ice surface.