• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1155-1163
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• 2004

Extracellular signal-regulated kinase (ERK) signaling pathway is one of the mitogen-activated protein kinase (MAPK) signal transduction pathways. This pathway is known as pivotal in many signaling networks that govern proliferation, differentiation and cell survival. The ERK signaling pathway comprises positive and negative feedback loops, depending on whether the terminal kinase stimulates or inhibits the activation of the initial level. In this paper, we attempt to model the ERK pathway by considering both of the positive and negative feedback mechanisms based on Michaelis-Menten kinetics. In addition, we propose a fraction ratio model based on the mass action law. We first develop a mathematical model of the ERK pathway with fraction ratios. Secondly, we analyze the dynamical properties of the fraction ratio model based on simulation studies. Furthermore, we propose a concept of an inhibitor, catalyst, and substrate (ICS) controller which regulates the inhibitor, catalyst, and substrate concentrations of the ERK signal transduction pathway. The ICS controller can be designed through dynamical analysis of the ERK signaling transduction pathway within limited concentration ranges.

• 수산해양기술연구
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• 제41권1호
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• pp.78-84
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• 2005

The main goal of this work is to study the effects of temperature and volume fraction of fiber on the Charpy impact test with GF/PP composites. The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperature range of 60^{\circ}C$ to -50^{\circ}C$ by impact test. The critical fracture energy increased as the fiber volume fraction ratio increased. The critical fracture energy shows a maximum at ambient temperature and it tends to decreases as temperature goes up or goes down. Major failure mechanisms can be classified such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

• 한국분무공학회지
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• 제25권1호
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• pp.21-26
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• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• 한국수학교육학회지시리즈A:수학교육
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• 제48권3호
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• pp.235-263
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• 2009

The purpose of the study was to investigate the influence of children's understanding of fractions in mathematics problem solving. Kieren has claimed that the concept of fractions is not a single construct, but consists of several interrelated subconstructs(i.e., part-whole, ratio, operator, quotient and measure). Later on, in the early 1980s, Behr et al. built on Kieren's conceptualization and suggested a theoretical model linking the five subconstructs of fractions to the operations of fractions, fraction equivalence and problem solving. In the present study we utilized this theoretical model as a reference to investigate children's understanding of fractions. The case study has been conducted with 6 children consisted of 4th to 5th graders to detect how they understand factions, and how their understanding influence problem solving of subconstructs, operations of fractions and equivalence. Children's understanding of fractions was categorized into "part-whole", "ratio", "operator", "quotient", "measure" and "result of operations". Most children solved the problems based on their conceptual structure of fractions. However, we could not find the particular relationships between children's understanding of fractions and fraction operations or fraction equivalence, while children's understanding of fractions significantly influences their solutions to the problems of five subconstructs of fractions. We suggested that the focus of teaching should be on the concept of fractions and the meaning of each operations of fractions rather than computational algorithm of fractions.

• 한국초등수학교육학회지
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• 제18권2호
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• pp.319-339
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• 2014

최근의 우리나라 교육과정 문서 안에는 분수의 포함제와 등분제에 관한 논의가 증가하고 있다. 포함제와 등분제 두 가지 모두 성립이 불가능하다는 주장에서부터 두가지 모두 성립이 가능하다는 주장까지 다양한 의견이 제시되고 있다. 이 논문에서는 분수 나눗셈에서 포함제와 등분제 정의의 성립 가능성에 대해서 탐색하였다. 그 결과, 분수 나눗셈에서의 포함제와 등분제는 자연수의 그것을 적절히 확장시킴으로써 타당하게 정의될 수 있음이 드러났다. 나아가 이렇게 정의된 분수의 포함제와 등분제는, 문장제로부터 나눗셈식을 만들어내는 활동, 분수 나눗셈의 알고리즘을 증명하는 활동에서 효과적으로 활용될 수 있다.

• 한국추진공학회지
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• 제15권6호
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• pp.15-25
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• 2011

금속 연료 중 널리 사용되는 알루미늄의 연소 특성에 관하여 1차원 연소모델링을 제안하였다. 연소 모델링은 예열영역, 반응영역, 반응 후 영역, 세 영역으로 나누어 수행하였다. 또한 희박연소로 가정하여 단일 입자의 경우 입자크기와 당량비에 따른 화염속도, 나노와 마이크로 입자의 혼합물의 경우 혼합 비율에 따른 화염속도를 압력이 1기압 조건에서 계산하여 실험결과와 비교하였다. 단일입자의 경우, 입자의 크기가 작아질수록 화염속도가 빨라지고, 당량비가 낮아질수록 화염속도가 느려지는 현상이 관찰되었다. 나노와 마이크로 입자의 혼합물의 경우, 나노 입자의 함유량에 따라 화염속도는 빨라지며, 화염구조는 분리화염과 중첩화염이 나타남이 관찰되었다.

• Archives of Pharmacal Research
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• 제13권4호
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• pp.330-337
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• 1990

The crude polysaccharide from Panax ginseng prepared by hot water extration and precipiation with ethanol was further fractionated into neutral and acidic fractions by DEAE- cellulose ion exchange chromatography. The chemical compositions were 85.0% carbohydrorate and 15.0% protein for the neutral fraction, and 28.4% carbohydrate, 10.0% protein and 29.0% uronic acid for the acidic fraction. The acidic fraction was more effective in increasing of the ratio of spleen to body weight, the number of antibody secreting cells to SRBC and phagocytic activity of reticuloendothelial system, as well as antitumor activity against the solid form of sarcoma 180 in ICR mice than the neutral fraction. All polysaccharide fractions were mitogenic to cultured spleen cells of C57BL/6 mice. However, FA was different from FN in the co-mitogenicities with lectin mitogens. Both crude and acidic fractions potentiated remarkably the mitogenic activity of PHA-P or LPS in dose-dependent manner but neutral fraction enhanced only that of LPS. Three polysaccharide fractions had no effect on that of Con A. These results suggest that the acidic fraction may stimulate B and Td cells as well as macrophages while the neutral fraction may simulate only B cells and macropages.

• Computers and Concrete
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• 제7권5호
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• pp.421-435
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• 2010

This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test, have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

• 한국건설순환자원학회논문집
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• 제5권1호
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• pp.14-20
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• 2017

UHPC는 초고층 건물 및 초장대교의 경우 필연적으로 사용되어진다. 일반적으로 콘크리트는 압축강도보다 낮은 휨강도 및 인장강도를 가지므로 취성균열이 발생하여 에너지 흡수능력이 저하된다. 이러한 문제를 해결하기 위해 본 연구에서는 강섬유의 혼입율과 형상비가 UHPC의 기계적 물성에 미치는 영향을 조사하고자한다. 시리즈 I에서, 20mm 직선형 강섬유가 0, 1.0, 1.3, 1.5 및 2.0%의 혼입율로 첨가되었다. 시리즈 II에서는 16mm 강섬유를 0, 1, 1.5%로 혼입한 후 형상비에 따라 역학적 성질을 조사하였다. 실험결과, 압축강도의 차이는 미비했다. 하지만 휨강도 및 인장강도와 관련하여 혼입율 및 형상비가 증가함에 따라 휨성능 및 인장성능이 개선되었다.

• 한국주조공학회지
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• 제35권5호
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• pp.109-113
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• 2015

In this study, the measurement of FN (ferrite volume fraction) and the solution annealing ratio at a temperature of $1130^{\circ}C$ were determined with 15A elbow fittings of shell cast SSC13, and the corrosion resistance with and without austenitizing solution annealing were investigated in comparison with AISI304. The delta ferrite phase was observed in the material due to the slow cooling effect of the shell mold casting. However, the delta ferrite phase decreased gradually with the solution annealing at a temperature of $1130^{\circ}C$. The hardness generally decreased with a heat treatment; however, its corrosion resistance was improved with the heat treatment. In addition, when a passivation treatment was applied, its corrosion ratio showed the lowest value. The pattern of general corrosion decreased due to the decrease in the delta ferrite phase with the solution annealing treatment. Consequently, it is suggested that the corrosion resistance of SSC13 elbow fittings can be improved by increasing the ratio of any solution annealing treatment used and by decreasing the ferrite phase. The relationship between the ratio of solution annealing and delta ferrite is expressed as follows: SA (solution annealing ratio,%) = 98 - FN (ferrite volume fraction, %).