• 콘크리트학회논문집
• /
• 제21권3호
• /
• pp.377-386
• /
• 2009

ACI life-365 기준확산계수 모델은 NT build 443 방법에 의한 시험 결과들로부터 만들어졌다. 이 방법은 침지기간 동안의 시간평균 확산계수를 구하는 방법이므로 ACI에서는 침지기간 동안의 시간평균 확산계수를 기준확산계수로 정의한 것이다. ACI 모델에서는 재령에 따른 감소효과를 지수함수 형태로 표현하고 있으므로 이를 고려한 ACI 기준확산계수 모델의 수정이 필요하다. 이를 위해 본 연구에서는 염소이온 노출개시기를 고려한 확산방정식의 해석해를 유도하고, 이를 사용하여 NT build 443 방법의 시간평균 확산계수를 기준재령의 확산계수로 변환하였다. 연구결과 life-365 기준확산계수 모델은 기존 값 보다 10% 정도 증가되고 수정되어야 함을 밝혔으며, 이에 따라 NT build 443 방법과 NT build 492 방법의 기존관계를 수정하여 내구수명 평가에 이용할 수 있도록 하였다. JCI 확산계수모델과 ACI 확산계수모델의 직접적인 비교를 위하여 JCI 확산계수모델에 대응하는 기준확산계수를 유도하였으며, 이를 통해 JCI 모델보다 ACI 모델이 더 보수적인 결과를 나타내는 것을 확인하였다.

• 대한의용생체공학회:의공학회지
• /
• 제23권1호
• /
• pp.1-8
• /
• 2002

심방세동은 가장 많이 나타나는 부정맥으로. 뇌졸중 등 심각한 합병증을 초래하는 질환이다 심방세동이 발작성으로 발생하는 경우 단시간내 불규칙적으로 발생하기 때문에 그 진단이 어렵다 본 연구에서는 발작성 심방세동 환자의 조기진단을 위하여 심실세동 등의 진단에 이용되는 신호평균 심전도를 이용한 분석방법을 사용하였다 심방세동의 징후가 있는 환자는 초기에 심방에서 심근의 전기전도가 지연된다는 이론을 근거로 심전도 P파의 길이를 진단의 기준으로 하였다. p파 길이를 정확히 측정하기 위하여 다양한 종류의 필터와 차단주파수에 대하여 분석하였으며. p파의 시작과 끝점을 판단하는 여러 방법을 시도하였다. 분석 방법의 신뢰성을 높이기 위하여 자동으로 P파 길이를 측정하는 알고리즘을 구현하였다. 구현된 알고리즘의 검증을 위해서 발작성 심방세동 이외의 병력이 없는 환자 38명과 정상인 32명을 대상으로 임상 데이터를 수집하였다. 분석 결과 30 Hz 차주파수를 가지는 LMS 필터를 사용하고. 절대치 8.75 $\mu N$를 기준으로 P파의 시작과 끝점을 측정하여 P파 길이를 계산할 때가 가장 높은 발작성 심방세동의 예측도를 가졌다. 또한 발작성 심방세동의 진단을 위한 가장 적합한 판별 값을 구하기 위하여 수신 동작 특성 곡선을 이용한 결과. 의사결정의 판별 값을 112 ms로 하는 경우 진단의 민감도 88 %. 특이도 64.4 %의 결과를 얻을 수 있었다

• The Korean Journal of Physiology
• /
• 제2권2호
• /
• pp.93-99
• /
• 1968

The Present study attempted to analyze the fate of CO diffused into the circulating blood through the alveoli. Dogs were induced to CO poisoning by rebreathing CO gas mixture contained in Krog's spirometer, by closed circuit method, for 60 minutes. The spirometer was filled initially with 282 ml of CO and 20 liters of air and oxygen, so the composition of gases were arranged as 1.4% in CO and 50% in $O_2$ at the begining of the rebreathing. Oxygen was added corresponding to the utilization of $O_2$ by the animal in proceeding of the experiment. At 60th minutes of CO rebreathing, the concentration of CO in arterial blood and in mixed venous blood were analysed and compared with each other after the CO contents were corrected with the hematocrit measured in the arterial and mixed venous blood. The distribution of CO gas to other tissues was estimated by the analysis of CO diffused into the cystic bile and into the peritoneal gas pocket which was formed by injection of 300 ml air into the peritoneal cavity prior to the CO gas rebreathing. The blood volume was measured by dilution method using $^{51}Chromium$ tagged red cells. CO amount vanished in the animal body was calculated by subtraction of total CO content in blood stream and the CO remained in closed circuit breathing system from the CO amount given to the breathing system at the begining of the experiment. Results obtained are summarized as follows: 1. The content of CO corrected by the hematocrit value was slightly less in mixed venous blood than in arterial blood. The amount of CO diffused into the cystic bile and into the peritoneal cavity was averaged to 0.1% and 0.4% of the CO amount in 100 ml of blood, respectively. 2. For 60 minutes of CO rebreathing, CO-hemoglobin saturation reached about 77% at the 60th minutes, CO amount vanished in the experimental animal averaged 36.1 ml/dog/hr., or 21% of the total CO volume in the blood stream. The average vanishing rate of CO during 60 minutes of CO rebreathing per kg of body weight was 2.71 ml/hr. Production of CO measured in ten dogs under hypoxic condition averaged 0.023 ml/kg/hr. The major part of the CO vanished in the dogs seemed to be oxidized to $CO_2$ by various tissues of the animal. The conclusion might be delivered as such oxidation of CO to $CO_2$ by animal tissues can play a role in part of the process of recovery and protection of animal from CO-poisoning.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1991년도 춘계학술대회
• /
• pp.47-50
• /
• 1991

An automatized latency calculation method of evoked otoacoustic emission is proposed. Averaged e-OAE signal is measured from normal adult and it is processed by IBM-AT computer for latency calculation. After partition of stimulated and emitted signal on the time axis by converted linear prediction coding spectrum, latency is calculated by cross correlation method. The output is also compared with those of conventional autocorrelation and pure cross correlation methods. The result show that proposed method has better performance than those of conventional ones.

• 한국전산유체공학회지
• /
• 제16권2호
• /
• pp.49-55
• /
• 2011

Turbulent flows with wavy wall are simulated using Residual-based Variational Multiscale Method (RB-VMS) which is proposed by Bazilves et al(2007) as new Large Eddy Simulation methodology. Incompressible Navier-Stokes equations are integrated using Isogeometric analysis which adopt the basis function as NURBS. The Reynolds number is 6760 based on the bulk velocity and averaged channel height. And the amplitude (${\alpha}/{\lambda}$) of wavy wall is 0.05. The computational domain is $2{\lambda}{\times}1.05{\lambda}{\times}{\lambda}$ in the streamwise, wall normal and spanwise direction. Mean quantities and turbulent statistics near wavy wall are compared with DNS results of Cherukat et al.(1998). The predicted results show good agreement with reference data.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.793-797
• /
• 2003

In this paper, we present a self-localization method for mobile robots using vertical line features of indoor environment. When a 2D map including feature points and color information is given, a mobile robot moves to the destination, and acquires images by one camera from the surroundings having vertical line edges. From the image, vertical line edges are detected, and pattern vectors meaning averaged color values of the left and right region of each line segment are computed. The pattern vectors are matched with the feature points of the map using the color information and the geometrical relationship of the points. From the perspective transformation of the corresponded points, nonlinear equations are derived. Localization is carried out from solving the equations by using Newton's method. Experimental results show that the proposed method using mono view is simple and applicable to indoor environment.

• 한국해양공학회지
• /
• 제31권3호
• /
• pp.183-188
• /
• 2017

This paper provides numerical results for the estimation of the efficiency of KRISO energy saving devices in the design stage. A finite volume method is used to solve Reynolds averaged Navier-Stokes (RANS) equations, where the SST k-$\omega$ model is selected for turbulence closure. The propeller rotating motion is determined using a rigid body motion (RBM) scheme, which is called a sliding mesh technique. The numerical analysis focuses on predicting the power reduction by the designed KRISO devices (K-DUCT) under a self-propulsion condition. The present numerical results show good agreement with the available experimental data. Finally, it is concluded that CFD can be a useful method, along with model tests, for assessing the performance of energy saving devices for propulsion efficiency improvement.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.305-310
• /
• 2001

This paper presents the computational method for analyzing the compressible flow fields in a high voltage gas circuit breaker. There are many difficult problems in analyzing the gas flow in GCB due to complex geometry, moving boundary, shock wave and so on. In particular, the distortion problem of the grid due to the movement of moving parts can be worked out by the fixed grid technique. Numerical simulations are based on a fully implicit finite volume method of the compressible Reynolds-averaged Navier-Stokes equations to obtain the pressure, density, and velocity through the entire interruption process. The presented method is applied to the real circuit breaker model and the pressure in front of the piston is good agreement with the experimental one.

• 대한기계학회논문집B
• /
• 제30권7호
• /
• pp.700-706
• /
• 2006

This study presents a numerical procedure to optimize the shape of dimple surface to enhance turbulent heat transfer in a rectangular channel. The response surface based optimization method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter ratio, channel height-to-dimple print diameter ratio, and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. full factorial method is used to determine the training points as a mean of design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

• 한국환경과학회지
• /
• 제18권8호
• /
• pp.833-839
• /
• 2009

The calculation of the wind field for resource assessment is done by using CFD Reynolds-Averaged Navier-Stokes simulations performed with the commercial software WindSim. A new interface has been created to use mesoscale simulation data from a meteorological model as driving data for the simulations. This method makes it necessary to take into account thermal effects on the wind field to exploit the full potential of this method. The procedure for considering thermal effects in CFD wind field simulations as well as the impact of thermal effects on the wind field simulations is presented. Simulations for non-neutral atmospheric conditions with the developed method are consistent with expected behavior and show an improvement of simulation results compared with observations.