• The Korean Journal of Physiology
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• 제25권2호
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• pp.133-146
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• 1991

In order to elucidate systematically the effects of serotonin on gastric motility of guinea-pig, the contractile and electrical responses to serotonin were recorded using four kinds of muscle strips prepared from antral circular, antral longitudinal, fundic circular, and fundic longitudinal muscles. Experiments were performed using various methods including isometric contraction recording, transmural electrical field stimulation, junction potential recording, intracellular microelectrode technique, and partition stimulation method. The results were as follows: 1) The effect of serotonin on spontaneous contractions was inhibitory in the circular muscle strips of the antrum and fundus, while it was excitatory in the longitudinal muscle strips of the antrum and fundus. Serotonin changed mainly phasic contractions of both the circular and longitudinal muscle strips in the antrum, while it changed mainly tonic contractions of both the circular and longitudinal muscle strips in the fundus. 2) On the contractions induced by transmural nerve stimulation, serotonin decreased the amplitude in the circular muscle strips of the antrum, but it increased them in the other three groups of muscle strips(antral longitudinal, fundic circular, and fundic longitudinal). 3) On the contractions induced by direct muscle stimulation, serotonin decreased the amplitude in the circular muscle strips of the antrum and fundus. 4) In the fundic circular muscle strips serotonin potentiated excitatory junction potentials (EJPs), and in the antral circular muscle strips it evoked EJPs after inhibitory junction potentials(IJPS). 5) In the antral circular muscle strips serotonin did not affect the slow wave even at the disappearance of spontaneous contractions. On the contrary it increased the amplitude of the slow wave, when the spike component was potentiated and the second component was inhibited. 6) In the antral circular muscle strips the membrane potential was slightly hyperpolarized, but the membrane resistance was not changed. From the above results following conclusions could be made. 1) Serotonin inhibits spontaneous contractions of the circular muscle layer and it increases those of the longitudinal one, irrespective of the gastric region. 2) In the guinea-pig stomach there exists a serotoninergic facilitatory neuromodulation system which exerts its effect on cholinergically mediated contraction. 3) The excitation-contraction decoupling was observed in the effect of serotonin.

• 한국전산유체공학회지
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• 제21권4호
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• pp.96-101
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• 2016

A two-dimensional Stokes flow past a circular disk in a circular tube is analyzed. The circular disk is located coaxially with the circular tube and the Hagen-Poiseuille flow exists at upstream and downstream far from the circular disk. The Stokes approximation is used and the flow is investigated analytically by using the method of eigenfunction expansion and the method of least square. From the analysis, the stream function and the pressure of the flow field are obtained, and the streamlines and pressure distribution are shown. Also, the pressure and shear stress distributions on the circular disk and circular tube wall are calculated, and shown for some typical radii of the circular disk. The additional pressure drop induced by the disk and the drag force exerted on the disk are compared as functions of the radius of the circular disk, and it is shown that the shear force on the wall of the tube increases due to the disk.

• 대한기계학회논문집
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• 제11권2호
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• pp.296-303
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• 1987

본 논문에서는 동력전달용 기어에 주로 쓰이는 물림률 1.3 이상일 때, 치면접 촉응력과 공칭굽힘응력이 작게되는 풀림각 1˚로 고정하여 잇수 30∼100개 압력각 14˚∼30˚의 범위에서 최소 원호반경식과 치형 조건을 만족하는 최대 원호반경식에 대하여 고찰하였다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.364-368
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• 2000

In this paper, we present the design and fabrication of a new circularly polarized circular patch antenna. The antenna is realized using a plastic foam sheet, a Teflon substrate and a metal-coated film. The radiating element is a circular patch proximity-fed by a wide microstrip line. Two thins slots are introduced on the circular patch to obtain a circular polarized radiation. The antenna is optimized using a commercial software. The antenna has 18% impedance bandwidth, 4% axial-ratio band width and 9.12dBi gain.

• 소음진동
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• 제4권3호
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• pp.283-295
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• 1994

This work presents the experimental and finite element analysis results for the free vibration of 4 edges clamped, isotropic square plates with 2 collinear circular holes. Natural frequencies of finite element analysis are obtained for the complete square plate, the square plates with a central circular hole and the square plates with 2 collinear circulare holes. And natural frequencies are experimentally measured for the complete square plate, the square plate with a central circular hole(d = 150 mm) and the square plates with 2 collinear circular holes. Agreement between experimental and FEM results is excellent. Mode shapes in special case are presented. The conclusions of the study are as follows. There is little variation of nondimensional frequency parameters for the first six mode when the aspect ratio of circular hole is less than 1/6 in the isotropic square plates with 2 collinear circular holes. And the first nondimensional frequency parameter doesn't vary as the aspect ratio of circular hole increase.

• 한국해양공학회지
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• 제23권6호
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• pp.23-31
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• 2009

The interaction of incident monochromatic waves with a bottom-mounted vertical porous circular cylinder is investigated using the framework of the three-dimensional linear potential theory. The porosity of the circular cylinder is uniform vertically but varies in the circumferential direction. By adjusting the porosities of the circular cylinder, both the wave blocking performance of a porous semi-circular breakwater and the wave responses inside a circular harbor with an entrance are applied as calculation examples. It is found that the reflected waves, wave run-up, and wave forces are significantly reduced due to wall porosity, which are positive factors for a breakwater, and the amplification factor of a circular harbor at resonant frequencies is greatly reduced by a porous sidewall.

• 한국경영과학회지
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• 제39권4호
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• pp.97-113
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• 2014

Circular shareholding refers to a situation where at least three member firms in a business group have stock in other member firms and establish a series of ownership in a circular way. Although many studies have focused on the ultimate effect of circular shareholding on firm's value and profitability, there have been few studies which address how to resolve circular shareholding from the perspective of optimization theory. This paper proposes a heuristic method for identifying shareholdings which need to be cleared in order to settle the problem of circular shareholding in a business group. The proposed heuristic tries to maximize the sum of voting rights the controlling family has in its business group firms. The applications results confirm that the heuristic provides near-optimal solutions for most of 16 Korean large business groups involving circular shareholding.

• Journal of the Korean Data and Information Science Society
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• 제23권4호
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• pp.797-805
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• 2012

Many circular distributions are known to be not only asymmetric but also bimodal. Hidden truncation method of generating asymmetric distribution is applied to a bivariate circular distribution to generate an asymmetric circular distribution. While many other existing asymmetric circular distributions can only model an asymmetric data, this new circular model has great flexibility in terms of asymmetry and bi-modality. Some properties of the new model, such as the trigonometric moment generating function, and asymptotic inference about the truncation parameter are presented. Simulation and real data examples are provided at the end to demonstrate the utility of the novel distribution.

• Steel and Composite Structures
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• 제44권1호
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• pp.141-154
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• 2022

This paper describes the experimental and numerical investigation on circular and octagonal CFDST short columns under concentric loading to study their responses to various internal circular steel tube sizes by the constant cross-sectional dimensions of the external circular and octagonal steel tube. The non-linear finite element analysis of circular and octagonal CFDST columns was executed using the ABAQUS to forecast and compare the axial behavior influenced by the various sizes of internal circular steel tubes. The study shows that the axial compressive strength and ductility of circular and octagonal CFDST columns were significantly influenced by inner steel tubes with the strengths of constituent materials.

• 콘크리트학회논문집
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• 제11권3호
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• pp.81-88
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• 1999

원형 철근콘크리트 기둥의 전단보강철근에 의한 저항강도의 평가를 위하여 전단에 의한 사인장 균열 면을 관통하는 원형 전단보강철근의 횡하중 작용방향의 평균 인장력을 산정하였다 이를 위하여 원형 전단보강철근이 이루는 원의 중심선간 직경, 수직 배근간격 및 기둥축 방향에 대한 사인장 균열면을 고려하였으며, 이들 변수들을 이용하여 원형 전단보강철근의 유효단면적을 계산하는 공식을 제안하였다. 연구결과, 원형 전단보강철근의 유효단면적 계산을 위하여 근 10년 간 사용되어 온 상수 계수가 모든 경우에 일률적으로 사용될 수 없음을 보여주고 있다 즉, 기존에 사용되는 원형전단철근 유효단면적은 기둥의 전단저항강도의 계산에 있어서, 전단철근의 배근간격이 비교적 넓은 비내지진 지역에서는 안전 측의 예측을 하게 되어 구조물의 안전상 큰 문제가 없지만, 배근간격이 촘촘하거나 원통형강관을 사용하게 되는 내진 지역에서는 기둥의 전단저항강도를 실제보다 20% 정도 과하게 예측하여 구조물의 안전에 좋지 않은 결과를 낳을 수도 있다.