• 해양환경안전학회지
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• 제15권1호
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• pp.63-69
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• 2009

가스상의 체적분율과 압력강하는 기액이상류에 대한 이해와 예측에 있어서 매우 중요한 인자이다. 또한 그것들은 산업용 대용량의 열교환시스템 및 선박에 설치되는 보일러 및 냉동시스템의 설계에 있어서 필수적인 항목이다. 따라서 본 논문에서는 파이프의 모든 경사각도에서 기액이상류 가스상의 체적분율과 압력손실을 예측할 수 있는 이론적 해석 방법을 제시한다. 여기서의 이론적 해석은 2유체 층상류 모델을 기초로 하고 있다. 또한 이론적 해석결과와 기존의 실험결과와 비교한 결과에 대해서도 제시한다.

• 설비공학논문집
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• 제18권4호
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• pp.344-350
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• 2006

The present study investigates the characteristics of fire-driven heat flows and gas concentration in a compartment fire by using the modified VHS model (MVHS). The main idea of this model is to add some source terms for combustion products and oxygen consumption to the original VHS model for providing more accurate and useful information on gas concentration distributions as well as thermal fields. It is found that the present MVHS model shows fairly good agreement with the experimental data and the eddy breakup combustion model. The tilting angle of fire plume calculated by MVHS is larger than that of EBU model because the fire source of VHS is affected by ventilating flow less than EBU. However, this discrepancy is apparently reduced in the downstream region of fire source.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.93-99
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• 2000

It is well known that an automotive muffle strongly influences engine efficiency and noise reduction. The performance of a muffler system is determined by the geometrical parameters such as the relative location of an inlet and outlet pipe size and cross sectional geometry of a chamber. In this study numerical analysis was performed to examine the flow characteristics in the simple automotive muffler for the variation of volumetric rate and offset. The computational grid generation was carried out. The RNG k-$\varepsilon$ turbulence model was applied. To provide the boundary condition for numerical analysis the experimental measurement wes carried out. As a result of this study we could understand that there was a recirculation flow inside muffler and pressure loss depends on the variation of volumetric rate and offset.

• 한국해양공학회지
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• 제12권2호통권28호
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• pp.147-152
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• 1998

In this study turbine flowmeters were used to predict volumetric flow rate of each phase in two-phase, gas-liquid, flowing in a vertical tube. To determine volumetric flow rates of two-phase, air-water, flowing vertically upward through the polycarbonate tube(57mm ID-inside diameter), two turbine flow meters were used. For void fraction measurements, two gamma densitometers were used at each location of the turbine flow meter, one at the upstream and the other at the downstream. It was determined that the turbine flowmeter's outputs were a function of actual volumetric flow rate of each of the two phases. A two-phase flow model was developed.

• 오토저널
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• 제10권4호
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• pp.57-65
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• 1988

The study of unsteady gas exchange processes in the intake and exhaust systems of four-cylinder, four-stroke cycle internal combustion engine is described in this paper. The calculation model for the intake and exhaust systems is established and solved by the characteristic method for the equations defining these systems. A constant pressure theory is used for modeling branches of intake and exhaust manifolds. The relationship between the volumetric efficiency and the intake, exhaust pressure variation is clarified by simulation of these systems. It is found that the volumetric efficiency mainly depends on the intake pressure during the short period before the intake valves is closed, that the volumetric efficiency is influenced a little by intake chamber volume in the intake and exhaust system.

• 오토저널
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• 제9권3호
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• pp.85-93
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• 1987

The intake system of 4-cycle, 4-cylinder reciprocating engine is investigated the simple model composed of vessel, duct and throttling part. The numerical calculation based on the simulation is performed for the flow phenomena including heat transfer, friction and bend of duct at each part. In the multi-cylinder engine, the volumetric efficiency is increased a little as the junction location is closed to cylinder at the engine speed having maximum volumetric efficiency. The configuration and dimension of intake system have an influence on the inertia effect by resistance and pressure variation, and the magnitude of that is varied by the engine speed. Thus the volumetric efficiency is correlative to them. The volumetric efficiency is high as the intake valve close is advanced at the low engine speed, and is delayed at high speed.

• 한국정보과학회논문지:시스템및이론
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• 제31권12호
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• pp.682-691
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• 2004

본 논문에서는 햅틱 인터페이스를 통해 실제 찰흙을 만지는 것처럼 자연스럽게 가상 모델의 일부를 덧붙이거나 제거하여 원하는 모양을 만드는 햅틱 가상 조각 시스템을 소개하고자 한다. 햅틱 렌더링과 햅틱 툴에 의한 가상 모델의 변형은 볼륨 간접 표면 법을 기반으로 이루어진다. 본 시스템에서는 기존의 불륨 데이타 기반의 햅틱 조각 시스템이 갖는 문제점들을 개선하고 빠르고 안정된 알고리즘을 제안하였다. 먼저 가상의 물체를 조각하는 동안 빠른 햅틱 응답 속도(1 KHz)에 비해 훨씬 느린 비쥬얼 프로세싱(~30 Hz)의 속도 차이로 인해 발생되는 문제를 극복하기 위해 조각과정의 연속적인 두 모델의 중간 표면들을 생성하여 부드러운 햅틱 렌더링을 구현하였다. 조각 툴에 의해 변형되는 불륨 간접 표면은 비쥬얼 디스플레이를 위해 메쉬 모델로 컨버전 되는데 이때 메쉬 모델은 표면의 복잡도를 반영하여 적은 폴리곤으로 복잡한 모양을 보여줄 수 있는 비 군일 메쉬 생성 기법을 사용하였다. 실시간 조각과정에서 가상 물체의 다양한 비쥬얼 효과를 위해 메쉬 기반의 솔리드 덱스쳐링, 페인팅, 그리고 모델의 양각/음각기법도 구현하였다.

• Agricultural and Biosystems Engineering
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• 제2권2호
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• pp.63-68
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• 2001

The objective of this study was to develop a real-time soil moisture meter using RF impedance. The impedance suchas capacitance and resistance (or conductance) was analyzed using parallel cylinder type capacitance probe(C-probe) and Q-meter (HP4342). The capacitance and conductance of soil increased as volumetric water content increased. The 5 MHz of modified Colpitts type crystal oscillator was designed to detect the capacitance change of the C-probe with moist soil. A third order polynomial regression model was proposed to describe the relationship between RF impedance and volumetric water content. The prototype real time moisture meter consisted of the C-probe, sample container, oscillator, frequency counter and related signal processing units. The calibration equation for measurement of volumetric moisture content of soil was developed and validated. The correlation coefficient and root mean square error between measured volumetric water content by oven method and predicted values by prototype moisture meter for unknown soil samples were 0.984 and 0.032$cm^3$$cm\^3$, respectively.

• Geomechanics and Engineering
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• 제13권5호
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• pp.743-756
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• 2017

Laboratory investigation reveals that rockfills exhibit significant stress-path-dependent behavior during shearing, therefore realistic prediction of deformation of rockfill structures requires suitable constitutive models to properly reproduce such behavior. This paper evaluates the capability of a strain hardening model proposed by the authors, by comparing simulation results with large-scale triaxial stress-path test results. Despite of its simplicity, the model can simulate essential aspects of the shear behavior of rockfills, including the non-linear stress-strain relationship, the stress-dependence of the stiffness, the non-linear strength behavior, and the shearing contraction and dilatancy. More importantly, the model is shown to predict the markedly different stress-strain and volumetric behavior along various loading paths with fair accuracy. All parameters required for the model can be derived entirely from the results of conventional large triaxial tests with constant confining pressures.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.239-251
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• 2022

The use of lateral reinforcement in confined concrete columns can improve bearing capacity and deformability. The lateral responses of lateral reinforcement significantly influence the effective confining pressure on core concrete. However, lateral strain-axial strain model of concrete columns confined by lateral reinforcement has not received enough attention. In this paper, based on experimental results of 85 concrete columns confined by lateral reinforcement under axial compression, the effect of unconfined concrete compressive strength, volumetric ratio, lateral reinforcement yield strength, and confinement type on lateral strain-axial strain curves was investigated. Through parameter analysis, it indicated that with the same level of axial strain, the lateral strain slightly increased with the increase in the unconfined concrete compressive strength, but decreased with the increase in volumetric ratio significantly. The lateral reinforcement yield strength had slight influence on lateral strain-axial strain curves. At the same level of lateral strain, the axial strain of specimen with spiral was larger than that of specimen with stirrup. Furthermore, a lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression was proposed by introducing the effects of unconfined concrete compressive strength, volumetric ratio, confinement type and effective confining pressure, which showed good agreement with the experimental results.