• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.9
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• pp.1991-1998
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• 2015

This paper presents the antenna factor characteristics of a calculable dipole antenna with a hybrid balun, installed above ground plane vertically and horizontally, using Method of Moments (MoM). An expression for the antenna factor is formulated using the concept of power mismatch loss. The input impedance and effective length of the antenna, which are in the formula of the antenna factor, are calculated using the MoM. The results show that the antenna factors above a ground plane are agreed with the free space antenna factors within ± 0.14 dB. The horizontal antenna factors are varied more by 0.2 dB than the vertical antenna factors.

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.16-23
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• 2001

Comparing with general optical fiber sensors performing localized measurement, distributed optical fiber sensors can measure along an optical fiber, and they have large measuring range. The surface-mounting method with epoxy adhesive is general in attaching optical fiber sensors to structures, This is also appliable to the structural integrity monitoring with Brillouin-scattering distributed optical fiber sensors. In this paper, Brillouin-scattering distributed optical fiber sensors, which are attached to the surface of a structure with epoxy adhesive, was verified with the finite element method. From the analysis results of strain transfer through the structure, optical fiber coating, cladding and core, the strain transfer rates were calculated. And the influence of the epoxy free-end was also studied.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.1
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• pp.29-38
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• 2018

In order to evaluate the performance of the floating wave power, which is an axisymmetric oscillating water column type, linearized free surface boundary condition considering the influence of PTO (power takeoff) was derived and a finite element numerical model was established. Numerical experiments were carried out by varying cylinder length, skirt length, and depth of water, which are design parameters that can change the resonance of water column in cylinder and heave resonance of the float, which is considered to affect the power generation efficiency. Finally, the basic data necessary for the optimum design of the power generation system were obtained. As a result, the efficiency of the power generation system is dominated by the heave motion resonance of the float rather than the water column resonance in the cylinder, and the resonance condition for the heave motion can be changed efficiently by attaching the skirt to the outside of the buoy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.89-95
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• 2013

This study investigates a parallel manipulator that can move over two parallel sliders and in which the end-effector of the manipulator can be adjusted arbitrarily. Through the direct and inverse kinematics of the manipulator, position equations are derived. These equations represent the relationship between the positions of the sliders and the position of the end-effector. The Jacobian matrices of the direct and inverse kinematics are obtained by these equations. By using the condition number defined from these matrices, the local performance index of the manipulator is proposed. By using the simulation results of the performance index, we find that the manipulator can smoothen movements in only one quadrant and that the distribution of the maximal performance index is affected by the ratio of the length of links and the orientation of the end-effector.

• Journal of Wetlands Research
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• v.21 no.3
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• pp.207-214
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• 2019

This study investigated the flow characteristics in an annular flume with a free water surface using the Acoustic Doppler Velocimeter(ADV) in the laboratory. The flow was driven by the rotation of the inner cylinder in a way designed not to interfere with flocculation of cohesive sediments. The effect of the inner cylinder for the longitudinal velocities showed highest near the moving boundary and decreased towards the outer wall. At the lower longitudinal velocity, there was a peak in turbulent kinetic energy near the bed, whereas it moved upward to with increasing of the velocity. The longitudinal velocities estimated using the power law were in good agreement with the measured values than the values predicted by the log-law with roughness lengths. The average friction velocities evaluated by Reynolds shear stress were smaller than the values calculated using the log-law and power law when increasing the longitudinal velocity.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.2
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• pp.142-149
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• 2019

The coils to transmit the electric energy are necessary to charge an electric vehicle wirelessly. There are several types of coils, from basic circular coils to DD-type coils for enhancing the coupling effect between two coils. However, DD-type coils with a good coupling effect between coils have a disadvantage in use because of the structure complexity of the power conversion device of transmitting and receiving side. In this paper, we propose a method to calculate the inductance value and to design the size of the spiral inductor which is convenient to fabricate when the power is transmitted wirelessly by using two coils in free space. Since the bifurcation phenomenon occurs when the XLm value is similar to the load resistance value in the resonator the XLm value was selected to be equal to the minimum load resistance value to minimize this phenomenon, and the inductance value required for the resonator was calculated. In order to realize the calculated inductance value by the spiral inductor, the relationship between the inductance value and the size, the number of turns, the total coil length of a spiral inductor was investigated. In addition, the change of coupling coefficient k according to the horizontal separation of two coils was examined and an appropriate inductor was selected.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.323-331
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• 2019

In this study, a computational model approach for the modeling of hydrodynamic pressures acting on radial gates during strong earthquakes is proposed. The use of the dynamic layering method with the Arbitrary Lagrangian Eulerian (ALE) algorithm and the SIMPLE method for simulating free reservoir surface flow in addition to moving boundary interfaces between the fluid domain and a structure due to earthquake excitation are suggested. The verification and validation of the proposed approach are realized by comparisons performed using the renowned formulation derived by the experimental results for vertical and inclined dam surfaces subjected to earthquake excitation. A parameter study for the truncated lengths of the two-dimensional fluid domain demonstrates that twice the water level leads to efficient and converged computational results. Finally, numerical simulations for large radial gates with different curvatures subjected to two strong earthquakes are successfully performed using the suggested computational model.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.1011-1019
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• 2021

This study presents numerical simulations of submerged jump and washed-out jump resulted from the flow over the embankment type weir. Unsteady Reynolds Averaged Navier-Stokes (URANS) equations are solved with the k-𝜔 SST turbulence model. Validations are carried out using the experimental results in the literature, revealing that computed roller shape, free surface, and mean velocity are in good agreement with measured data. The volume fractions of water of the submerged jump and washed-out jump are compared, and the characteristics of the two flows from the double-averaged volume fractions of water are presented. The condition under which the transition occurs from the submerged jump to washed-out jump is presented by the relation between the relative embankment length and submergence factor via numerical simulations by changing the weir length, discharge, and tailwater depth.

• Journal of the Daesoon Academy of Sciences
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• v.16
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• pp.217-226
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• 2003

당시(唐詩)에는 당나라 사람들의 생활상이 많이 반영되고 있으며, 이러한 기록들은 많은 부분에 있어서 역사서적의 내용과 일치하기도 한다. 그러므로 우리는 당시를 통하여 당나라의 제도 뿐만 아니라 당나라 사람들의 생활도 광범위하게 이해할 수 있다. 본 고에서 우리는 당시에서 언급되고 있는 당나라 사람들의 복식에 있어서 몇 가지 문제들을 간략히 서술하기로 한다. 당대 초기에는 수나라 복제를 따랐으나, 태종(太宗)과 고종(高宗)을 거치면서 품급에 따라 복색을 구체적으로 구분하였으며, 여자들도 남편의 복색을 따랐다. 황색을 황제의 복색으로 한 것은 고종 총장 원년(668)에 시작되었다. 고종 상원(上元) 원년(674)에는 또 관원의 품급에 따라 색깔의 짙고 옅음을 엄격히 구분하였을 뿐만 아니라 요대의 장식물 재료에도 상세한 규정을 함으로써 신분의 차이를 더욱 구체적으로 구분하였다. 관복의 색깔로 등급의 차이를 구별한 외에도 5품 이상의 관원에게는 어부(魚符)를 담는 어대(魚袋)를 차고 다니게 함으로써 귀천을 분별하였고, 조정의 부름에 응하는 부신(符信)으로 삼았다. 어부는 물고기 모양으로 관등에 따라 금(金)·은(銀)·동(銅)으로 만들어 몸에 지니고 다녔다. 관원들은 갓의 모양으로도 귀천을 구분하였다. 귀족을 갓을 썼으나 평민은 쓰지 못하였고, 문관과 무관도 갓을 각기 달리하였다. 당시에는 또 여자들의 복식과 관련한 묘사도 상당히 보인다. 당나라 때의 여자들은 한(漢)나라 진(晋)나라 때와 마찬가지로 일반적으로 윗옷과 치마를 입었다. 치마는 가슴에서 동여매었고, 그 길이도 매우 길어 땅에 3촌(寸)까지 끌렸다. 여자들은 대개 상의(上衣) 밖에 이른바 반비(半臂)라는 반소매의 옷을 입었다. 본래는 궁녀들이 일하기 편리한 복장으로 입었는데, 후에 점차 여자들의 평상복이 되었다. 여자들의 눈썹과 머리형에 관해서도 당시에는 많이 묘사되고 있다. 여자들의 머리장식과 화장 그리고 몸의 각종 장식구에 대해서도 당시에는 상당히 언급되고 있다. 당나라 여자들의 복식에 있어서 가장 큰 특징은 국내 소수민족 및 외국의 복식에 영향을 받아 "호복(胡服)"을 즐겨 입었다는 점이다. 이른바 "호복"은 서역만을 가리키는 것이 아니라 주변국들의 복장도 가리킨다. 여자들이 쓰는 모자와 신발에도 많은 변화가 생겼다. 당나라 중원지역에는 "만화(蠻靴)"를 신는 여자들이 생겨났으며, 이것은 호복의 하나로 호화(胡靴)라고 칭하기도 하였다. 여자들의 미와 상대적인 자유에 대한 추구는 당시에 강렬히 나타나고 있으며, 이것은 당나라 여자들의 사상이 점차로 개방화되고 있음을 시사해 준다. 이러한 개방의 과정은 당나라 사회의 개방과 사상문화의 교류·진보와 밀접히 관련하는 것이다. 그래서 당나라 사람들의 복식에 대한 당시의 묘사는 우리가 당나라 사회와 사람들의 생활을 이해하는데 중요한 단서가 되고 있다고 말할 수 있다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.6
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• pp.1253-1259
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• 2001

The purpose of this study was to investigate the effects of green tea catechin on change of bone tissue in long-term cadmium treated rats. Sprague-Dawley male rats weighing 100$\pm$10 g were randomly assigned to one normal group and three cadmium treated groups. Cadmium groups were classified to catechin free diet group (Cd-0C group), 0.25% catechin diet group (Cd-0.25C group) and 0.5% catechin diet group (Cd-0.5C group) according to the levels of catechin supplement. Animals were raised for 20 weeks. Cadmium were supplied as drinking water of 50 ppm Cd$^{2+}$. Effects of catechin were analyzed on changes of bony tissue in long-term cadmium treated rats by determining the accumulated cadmium in bone and bone mineral density and micro- photographs of bony tissue. The cadmium accumulation of tibia and femur were higher in Cd-treated groups than in normal group, but they was lowered by catechin supplementation. The bone mineral density (BMD) of tibia and femur in Cd-0C group was significantly lower than in normal group, but it of catechin supplemetation group was similar to normal group. Microphological changers were appeared under a light microscope and an electro microscope reveal no structural changes in bony spicules, marrow cell distribution and cellular morphology in all groups. The bone weight and length tend to decrease in Cd-0C groups. Catechin supplementation in long-term cadmium treated rats depressed the cadmium accumulation in bony tissue that led to improve the bone mineral density in tibia and femur.r.