• Architectural research
• /
• 제12권2호
• /
• pp.93-98
• /
• 2010

This paper describes a numerical method for estimating the elastic moduli of cement paste. The cement paste is modeled as a unit cell which consists of three components: the unhydrated cement grain, the gel, and the capillary pore. In the unit cell, the volume fractions of the constituents are quantified using a single kinetic function calculating the degree of hydration. The elastic moduli of cement paste are calculated from the total displacements of constituents when a uniform pressure is applied to the gel contact area. The cement paste is assumed to be a homogenous isotropic matrix. Numerical simulations were conducted through the finite element analysis of the three-dimensional periodic unit cell. The model predictions are compared with experimental results. The predicted trends are in good agreement with experimental observations. This approach and some of the results might also be relevant for other technical applications.

• Journal of Mechanical Science and Technology
• /
• 제14권8호
• /
• pp.861-866
• /
• 2000

Flow induced shape change is important for spatial interpretation of vascular response and for understanding of mechanotransduction in a single cell. We investigated the possible shapes of endothelial cell (EC) in a mathematical model and compared these with experimental results. The linearized analytic solution from the sinusoidal wavy wall and Stokes flow was applied with the constraint of EC volume. The three dimensional structure of the human umbilical vein endothelial cell was visualized in static culture or after various durations of shear stress (20 $dyne/cm^2$ for 5, 10, 20, 40, 60, 120min). The shape ratio (width: length: height) of model agreed with that of the experimental result, which represented the drag force minimizing shape of stream-lining. EC would be streamlined in order to accommodate to the shear flow environmented by active reconstruction of cytoskeletons and membranes through a drag force the sensing mechanism.

• 한국수소및신에너지학회논문집
• /
• 제19권1호
• /
• pp.26-34
• /
• 2008

This study presents an aerodynamic design and an experimental performance test of a turbo air compressor consisted of mixed-flow impeller and curved diffuser for the PEM fuel cell vehicle application. Many studies compare the efficiency, cost or noise level of high-pressure and low-pressure operation of PEM fuel cell systems. Pressure ratio 2.2:1 is considered as design target The goal of compressor design is to enlarge the flow margin of compressor from surge to choke mass flow rate to cover the operational envelope of FCV. Large-scale rig test is performed to evaluate the compressor performance and to compare the effects of compressor exit pipe volume to stall or surge characteristics. The results show that the mixed-flow compressor designed has large flow margin, and the flow margin of compressor configuration with small exit volume is larger than that with large exit volume.

• 한국수소및신에너지학회논문집
• /
• 제15권2호
• /
• pp.159-165
• /
• 2004

Fuel cell makes electricity through chemical reaction. Bipolar-plate distribute hydrogen, oxidation using channel geometry condensation of water vapor inside channels of bipolar-plates lowers efficiency of fuel cell. Usually high pressured gas supply is used to solve the water condensation problem with serpentine type channel geometry. In this study, a new channel geometry shows feasible to minimize lowering efficiency due to water condensation through numerical and experimental analysis.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권5호
• /
• pp.2819-2822
• /
• 2013

In this study, antiproliferative effects of the selective estrogen receptor modulator Tamoxifen and the aromatase inhibitor letrozole (Femara) were evaluated and compared using the FM3A cell line, originating from a C3H mouse mammary carcinoma and positive in terms of estrogen receptor (ER) expression. Cell kinetic parameters including labelling index, mitotic index and labelling index were assessed after exposure of the. FM3A cell line to $0.001{\mu}g/ml$ of Tamoxifen and $0.25{\mu}g/ml$ of Femara for 4, 8, 16 and 32 h for all parameters. The results showed that cell growth was inhibited by both agents. There was a significant decrease in labelling index and mitotic index and significant increase in apoptotic index for all experimental groups. The differences between control and all experimental groups were statistically significant (p<0.001) for all applications.

• 한국동물학회:학술대회논문집
• /
• 한국동물학회 1996년도 한국생물과학협회 국제학술대회
• /
• pp.151.2-151
• /
• 1996

No Abstract, See Full Text

• International Journal of Contents
• /
• 제11권3호
• /
• pp.34-38
• /
• 2015

A band stop filter is proposed with cascading unit cells that are based on a dual composite right/left-handed (D-CRLH) conductorbacked coplanar waveguide. The parameters of the unit cell have been analyzed to confirm the behavior of each component for the equivalent circuit of the cell. We simulated the dispersion characteristics and energy distribution and have determined that the unit cell has a D-CRLH property. The band stop filter was implemented by symmetrically cascading two of the proposed unit cells. The experimental results for the band stop filter revealed a band rejection performance of 32 dB and a return loss of 0.35 dB in the stopband frequency range from 869MHz to 954MHz. Finally, we show that there is a good agreement in the experimental results and those obtained through the simulations.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 춘계학술대회
• /
• pp.81-84
• /
• 2006

To investigate the characteristics of water droplet on the gas diffusion layer from both upper-view and side-view of flow channel, a rig test apparatus was designed and fabricated with L-shape acryl plate in a $1mm{\times}1mm$ micro-channel. This experimental device is used to simulate the single droplet growth and its transport process under fuel cell operating condition. As a first step, we investigated the growth and transport of single water droplet with working temperature and air flow velocity. The contact angle and its hysteresis of water droplet at departing moment are measured and analyzed. It is expected that this study can provide the basic understanding of liquid water droplet behavior in gas flow channel and GDL interface during the PEM fuel cell operation.

• Coupled systems mechanics
• /
• 제12권5호
• /
• pp.419-428
• /
• 2023

We have developed a model for estimating the parameters of viscous materials from indirect tensile tests for asphalt. This is a simple Burger nonlinear rheological two-cell model or standard model. At the same time, we begin to develop a more versatile and complex multi-cell model. The simple model is validated using experimental load-displacement results from laboratory tests: The recorded displacements are used as input values and the measured force data are simulated with the model. The optimal model parameters are estimated using the Levenberg-Marquardt method and a very good agreement between the experimental results and the model calculations is shown. However, not all parts of the model are active in the loading phase of the experiment, so we extended the validation of the model to the simulation of the relaxation behaviour. In this stage, the other model parameters are activated and the simulation results are consistent with the literature. At this stage, we have estimated the parameters only for the two-cell uniaxial model, but further work will include results for the multi-cell model.

• 대한화학회지
• /
• 제47권1호
• /
• pp.79-86
• /
• 2003

볼타 전지에 대한 학생들의 오개념과 고등학교 화학 2 교과서에서 기술된 내용을 연구, 분석하였다. 볼타 전지에 대해 많은 학생들이 오개념을 가지고 있으며 몇몇 화학교과서의 경우 내용이 잘못 기술되어 있다는 것을 본 연구에서 밝혔다. 대부분의 교과서에는 볼타 전지의 초기 측정 전압이 왜 1.1V와 유사하며 시간이 지남에 따라 감소하는지에 대한 명확한 설명이 없다. 표준상태에서 볼타 전지의 기전력은 0.76V 이지만 어떤 교과서에는 다니엘 전지처럼 1.1V로 기술되어 있다. 대부분의 학생들은 볼타 전지를 배우거나 실험을 한 후에도 여전히 오개념을 가지고 있으며 이것은 적어도 다음 두 가지 요인에서 기인된다고 여겨진다. 첫째, 볼타 전지의 초기 측정 전위값이 다니엘 전지의 전위와 매우 유사하기 때문에 학생들이 혼동하여 오개념을 가진다. 둘째, 대부분 교과서의 볼타 전지 실험은 표준 상태가 아닌 조건에서 수행되도록 기술되어 있으므로 학생들이 실험을 하더라도 표준 상태 기전력값을 얻을 수 없기 때문에 여전히 오개념을 가지게 된다. 따라서 우리는 학생들의 오개념을 줄일 수 있는 개선된 볼타 전지의 실험 모형을 제안하였다.