• 대한수학교육학회지:수학교육학연구
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• 제19권1호
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• pp.25-43
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• 2009

이 연구는 분수 개념의 여러 가지 의미에 대해 우리나라 교과서와 싱가포르의 교과서를 비교 분석하여보고, 그 교육적 시사점에 대해 논의한 것이다. 논의의 결과, 등분할 활동을 한 결과를 확인할 수 있는 활동 위주로 구성하는 것이 교사나 학생들에 혼란을 주지 않을 것으로 기대되었다. 분할분수의 정의도 두 나라 모두 상대적인 크기를 갖는 수로서의 분수를 드러내도록 다듬어야할 필요가 있음을 알았다. 또한 몫분수나 비율분수를 도입하는 상황이 우리나라가 싱가포르보다 자연스럽지 못하다. 양분수를 좀 더 비중 있게 다루는 것이 실생활과의 관련성 뿐 아니라, 가분수를 도입할 때에 이해를 쉽게 해주며, 분수를 절대적인 크기를 갖는 수로 받아들이도록 하는데도 무리가 없음을 알았다. 그 뿐 아니라 두 나라 교육과정을 비교해본 결과 이산량의 등분할을 통한 분수 도입을 제외하고는 대체로 지도 순서가 우리나라보다 싱가포르가 더 빨리 도입되지만, 단계를 더 세분하여 지도할 뿐 아니라 다루는 분수에 대한 제한이 많음을 알 수 있었다. 우리나라에서도 불필요한 계산에 시간을 소비하지 않도록 이와 같은 제한을 두는 것이 바람직한 대안이라고 판단된다.

• 대한수학교육학회지:학교수학
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• 제8권2호
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• pp.123-138
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• 2006

이 연구는 분수 개념의 여러 가지 의미를 분석해보고, 분수 개념의 생성 과정을 역사 발생적으로, 심리적으로 분석하고 이를 바탕으로 현재 지도되고 있는 7차 교육 과정에 의한 교과서의 분수 개념 도입과 관련한 내용을 비판적으로 분석해 보면서 그 교육적 시사점에 대해 논의한 것이다. 그 논의의 결과를 요약하면 다음과 같다. 분할분수는 분류된 다른 분수와 그 의미가 중첩되어 있으므로, 다른 분수와 함께 묶어 분류하는 것보다 분할분수는 독립시키고 나머지 분수들을 분류하도록 한다. 그리고 분수 개념은 분배와 측정 과정에서 발생하였으므로 분수를 도입할 때 분배, 측정과 관련하여 등분할 활동과 양분수를 강조하는 것이 바람직하다. 또한 분수는 단위분수를 단위로 하여 구성되었으므로, 학교에서도 단위분수를 바탕으로 분수를 구성해 나가는 것이 바람직하다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.337-338
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• 2014

In this study, a method of using a capacitance sensor was investigated as a means to measure the mass fraction of a type of harmful substance. Using MEMS process, we developed a capacitance sensor and studied the real time mass fraction with harmful substance mixture liquid.

• 한국가시화정보학회지
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• 제15권1호
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• pp.41-46
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• 2017

Control of mixing and transport processes are the key areas that can be benefited by understanding the hydrodynamics in gas-liquid two-phase flows. In particular, the enhanced bubble-induced liquid-phase mixing is known to be a function of void fraction distribution, gas phase velocity and so on. To further our insight on the characteristics of the liquid-phase mixing induced by the bubbles, in the present study, we experimentally investigate the mixing performance of a rectangular bubble column while changing the void fraction from 0.006 to 0.075%. A shadowgraphy technique is used to measure the gas-phase properties such as void fraction and size/velocity of bubbles. On the other hand, we use dye visualization with low diffusive buoyant dye to directly measure the level of mixing. Finally, we confirm that the time taken for full mixing scales with the inverse of volume void fraction.

• 대한기계학회논문집B
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• 제28권7호
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• pp.863-870
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• 2004

The temperature and soot particle measurement technique in a laminar diffusion flame has been studied to investigate the characteristics of soot particle with temperature using a co-flow burner. The temperature distribution in the flame were measured by rapid insertion of a R-type thermocouple and the soot particles by LEM/LIS techniques. In these measurement, soot volume fraction, number density and soot diameters were analyzed experimentally. As a results, the spacial distributions of particle volume fraction, soot diameter, and number density are mapped throughout the flame using the Rayleigh theory for the scattering of light by particles. A laser extinction method was used to measure the soot volume fraction and laser induced scattering method was used to measure the soot particle diameter and number density. Also, we measured temperature without the effect of soot particles attached to the thermocouple junction, which is close to the nozzle. In this result, we found that upstream zone has a unstable flowing in co-flow diffusion flame and the y-axis temperature of flame has a uniform temperature distribution in the most soot volume fraction zone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1267-1273
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• 2004

The temperature and soot particle measurement technique in a laminar diffusion flame have been studied to investigate the characteristics of soot particle with temperature using a co-flow burner. The temperature distributions in the flame were measured by rapid insertion of a R-type thermocouple and the soot particles were detected were detected by LEM/LIS techniques. In these measurement, soot volume fraction, number density and soot diameters were analyzed experimentally. As a results, the spacial distributions of particle volume fraction, soot diameter, and number density are mapped throughout the flame using the Rayleigh theory for the scattering of light by absorbing particles. A laser extinction method was used to measure the soot volume fraction and Laser induced scattering method was used to measure the soot particle diameter and number density. Also, we measured temperature without the effect of soot particles attached to the thermocouple junction, which is close to the nozzle. In this result, we found that upstream zone has a unstable flowing in co-flow diffusion flame and the y-axis temperature of flame has a uniform temperature distribution in the most soot volume fraction zone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.721-727
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• 2000

Impedance method was carried out to design the electrode that can measure the void fraction of the bubbly flow in pool reservoir. To find out the optimum electrode shape, Styrofoam-tests were performed in a specially designed acrylic reservoir. Three kinds of electrodes were designed to compare the characteristics of water-air flow. The resistance was increased as the void fraction increased and the capacitance was decreased as the void fraction increased. The resistance is a main parameter to express the nature of the water-air flow in impedance method. Almost all the values of impedance were involved in resistance. The degree of deviation from the mean-resistance values showed reasonable results. Electrode type-I expressed excellent results among the three electrode shapes. The impedance values in void fraction 0-10% were similar to those of Maxwell's equation. But the impedance values in void fraction 10-20% were not similar to those of Maxwell' equation because of the edge effect near electrode.

• 한국가시화정보학회지
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• 제15권1호
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• pp.11-18
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• 2017

A two-phase flow observed in a heat exchanger or nuclear power generation often has a profound effect on undesirable noise or flow characteristics. Void fraction, which refers to the ratio of gas (or liquid) to the total fluid, affects heat transfer coefficient, vibration and so forth. In other words, void fraction is one of most important parameters in two-phase flow since it contributes to comprehend the characteristics of two-phase flow. We developed a two-phase flow visualization system to measure cross-sectional and volumetric void fractions by using quick closing valves and image processing software. With this system, we could observe the plug, slug, and stratified flow patterns of two-phase flow and measure a myriad of void fractions. As a consequence of the experiment, we found that the estimated void fractions were largely coincident with the predictive values by Chisholm model.

• 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.

• 대한기계학회논문집B
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• 제29권3호
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• pp.376-383
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• 2005

In the paper we investigate characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. In previous study, we showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. A gas-chromatograph is used to measure concentration field, a smoke-wire system is used to measure streak line, and a PIV system is used to measure velocity field in lifted flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. In PIV measurement, flow velocity for those three flames has minimum value at the tip of flame front. To differentiate triple flame and premixed flame, $\Phi$ value of partially premixed fraction is employed. The partially premixed fraction $\Phi$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.