• 대한수학교육학회지:학교수학
• /
• 제12권3호
• /
• pp.439-454
• /
• 2010

본 연구는 두 명의 중학교 2학년 학생들이 어떻게 단위 분할 도식의 수정, 변경을 통하여 분수나눗셈 상황에서 그들 자신만의 자가-생성 알고리듬을 만들어 나가는지 보여주고 있다. 교육실험이 연구방법으로 사용되었고, 일년간 행해진 교육실험 중 일부분의 자료가 본 연구를 위해 분석되었다. 두 명의 참여 학생들은 기준단위와 제수사이의 상호 관계 구성과 활용으로 분수나눗셈을 위해 전통적으로 학습되어 왔던 '뒤집어서 곱하기'와 같은 역할을 하는 그들 자신의 자기-생성 알고리듬을 구성할 수 있었다. 본 연구결과는 또한 학생들이 만들어 낸 알고리듬을 이해할 수 있는 것이 훌륭한 수학 교사로서의 질을 결정하는 하나의 요소로 고려 되어야 함을 보여주고 있다.

• 한국초등수학교육학회지
• /
• 제18권1호
• /
• pp.105-122
• /
• 2014

본 논문에서는 분수 나눗셈 알고리즘 지도 방법 개선을 위한 기초 작업의 일환으로, 우리나라 초등학교 수학 교과서에서의 분수 나눗셈 알고리즘 정당화 과정을 분석한다. 교과서에서는 간접적인 방법으로 분수 나눗셈식을 분수 곱셈식으로 변환시켜 알고리즘을 정당화하고 있다. 그 방법으로 추이성을 이용하는 것, 수 막대나 직사각형 모델을 이용하는 것의 두 가지가 있다. 2007 개정 교육과정에 따른 수학 교과서 ${\ll}5-2{\gg}$, ${\ll}6-1{\gg}$에서 분수 나눗셈 알고리즘은 외형상 6개이다. 그 중 4개는 형태상 제수의 역수를 곱하는 표준 알고리즘이다. 본 논문에서는 이러한 분석 결과를 바탕으로 다음의 세 가지 제언을 결론으로 제시한다. 첫째, 초등학교 5학년에서 역수라는 용어의 사용을 전향적으로 고려할 필요가 있다. 둘째, 비표준 알고리즘을 표준 알고리즘 형태로 도입하는 것을 고려할 필요가 있다. 셋째, 차후의 교육과정에서 분모가 1인 분수의 취급에 관해 논의할 필요가 있다.

• Carbon letters
• /
• 제3권3호
• /
• pp.127-132
• /
• 2002

Unidirectional polymer composites were prepared using high-strength carbon fibers as reinforcement and phenolic resin as matrix precursor with keeping fiber volume fraction at 30, 40, 50 and 60% respectively. These composites were carbonized at $1000^{\circ}C$ and graphitised at $2600^{\circ}C$ in the inert atmosphere. The carbonized and graphitised composites were characterized for mechanical properties as well as microstructure. Microscopic studies were carried out of the polished surface of carbonized and graphitised composites after etching by chromic acid, to understand the effect of fiber volume fraction on oxidation at fiber-matrix interface. It is found that the flexural strength in polymer composites increases with fiber volume fraction and so does for the carbonised composites. However, the trend was found to be reversed in graphitised composites. In all the carbonized composites anisotropic region has been observed at fiber-matrix interface which transforms into columnar type microstructure upon graphitisation. The extension of strong and weak columnar type microstructure is function of fiber volume fraction. SEM microscopy of the etched surface of the sample reveal that composites containing 40% fiber volume has minimum oxidation at the interface, revealing a strong interfacial bonding.

• 대기
• /
• 제29권4호
• /
• pp.381-390
• /
• 2019

This study investigates the impacts of urban land-use fraction and temperature advection on the urban heat island intensity over the Seoul metropolitan area using the UM (Unified Model) with the MORUSES (Met Office Reading Urban Surface Exchange Scheme) during the heat wave over the region from 2 to 8, August 2016. Two simulations are performed with two different land-use type, the urban (urban simulation) and the urban surfaces replaced with grass (rural simulation), in order to calculate the urban heat island intensity defined as the 1.5-m temperature difference between the urban and the rural simulations. The land-use type for the urban simulation is obtained from Korea Ministry of Environment (2007) land-use data after it is converted into the types used in the UM. It is found that the urban heat island intensity over high urban-fraction regions in the metropolitan area is as large as 1℃ in daytime and 3.2℃ in nighttime, i.e., the effects of urban heat island is much larger for night than day. It is also found that the magnitude of urban heat island intensity increases linearly with urban land-use fraction. Spatially, the estimated the urban heat island intensities are systematically larger in the downwind regions of the metropolitan area than in the upwind area due to the effects of temperature advection. Results of this study indicate that urban surface fraction in the city area and temperature advection play a key role in determining the spatial distribution and magnitude of urban heat island intensity.

• 한국초등수학교육학회지
• /
• 제22권4호
• /
• pp.385-403
• /
• 2018

분수 나눗셈의 여러 맥락 중 등분제와 카테시안 곱의 역 맥락에서는 제수의 역수 곱하기 알고리즘이 자연스럽게 유도된다. 그러므로 제수의 역수 곱하기 알고리즘을 분수 나눗셈의 통합 알고리즘으로 지도하고자 할 때 특히 이슈가 되는 것은 포함제 맥락이다. 이 논문에서는 포함제 맥락에서 $1{\div}$(제수)를 매개로 하는 방법이 지닌 잠재력 및 그 기반을 분석하고, 이 방법을 제수의 역수 곱하기 알고리즘을 분수 나눗셈의 통합 알고리즘으로 지도하려 할 때 고려할 수 있는 한 대안으로 제안한다. 포함제 맥락에서 $1{\div}$(제수)를 매개로 하여 제수의 역수 곱하기 알고리즘을 유도하는 방법은 다음과 같은 특징을 지니고 있다. 첫째, 포함제 맥락에서 맥락과의 연결성을 유지한 채로 제수의 역수 곱하기 알고리즘을 유도할 수 있다. 둘째, 다른 맥락들에서와 마찬가지로, 제수와 1의 곱셈적 관계에 주목한다. 셋째, 다른 맥락들에서와 마찬가지로, 제수와 1의 곱셈적 관계를 1/제수의 분모을 징검다리로 삼는 추론과 제수의 분자를 징검다리로 삼는 두 가지 추론으로 파악한다. 이러한 특징은 이 방법이 제수의 역수 곱하기 알고리즘을 분수 나눗셈의 공통 구조를 담고 있는 통합 알고리즘으로 다루는 데 기여할 수 있음을 시사한다. 한편, 이 방법은 양분수의 이중적 의미와 배의 합성을 그 기반으로 한다. 분수 나눗셈의 통합적 이해를 지향하는 교재 개발 및 수업 연구에서는 이 기반의 형성에 유의할 필요가 있다.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제41권1호
• /
• pp.1-5
• /
• 2020

Tumor necrosis factor-α (TNFα) is a representative marker for inflammation. Silk sericin is known as mild TNFα inducer. The purpose of this study was to compare the level of TNFα among different fractions of silk sericin. Silk sericin was extracted from cocoon and separated it by molecular weight. Each fraction was applied to RAW264.7 cells. The level of TNFα was evaluated by western blot and ELISA assay. In results, the level of TNFα was increased as time-dependent manner. Higher molecular weight fraction of sericin induced higher amount of TNFα than lower molecular weight fraction. In conclusion, different molecular weight fraction of sericin induced TNFα differently.

• 한국약용작물학회지
• /
• 제25권5호
• /
• pp.282-289
• /
• 2017

Background: To investigate the possibility of using Asarum sieboldii as an environment-friendly fumigant for protecting organic cultural heritages, the inhibitory effect of A. sieboldii extract against wood rot fungi on Hanji was examined. Methods and Results: The physical, optical, and morphological properties of Hanji inoculated with Trametes versicolor and Tyromyces palustris, and exposed to the n-hexane fraction of A. sieboldii extract, were measured. The physical properties were expressed as weight loss, zero-span tensile strength and viscosity and the optical properties were depicted by luminance and chromaticity ($L^*$, $a^*$, and $b^*$). The results showed that, the n-hexane fraction of A. sieboldii extract inhibited the growth of fungi on Hanji, and preserved its condition. At a concentration of 25 mg, the n-hexane fraction of A. sieboldii extract maintained zero-span tensile strength, increased viscosity, and restricted discoloration of Hanji. It also was confirmed that the weight of fungi infested Hanji exposed to the extract did not decrease. Scanning electron microscopic images revealed that the spores and hyphae of T. versicolor and T. palustris were not present on Hanji during treatment with > 25 mg of the n-hexane fraction of A. sieboldii extract. Conclusions: These results indicate that the n-hexane fraction of A. sieboldii extract by virtue of its antifungal effectiveness may help in preserving Korean paper cultural heritages, including Hanji.

• East Asian mathematical journal
• /
• 제38권4호
• /
• pp.379-396
• /
• 2022

In this paper, we investigate distribution strategies in the Egyptian fraction, and through this, we examine the distribution strategies of (fraction)÷(fraction) and then provide some educational implications. The (natural number)÷(natural number) of the sharing situation has the meaning of 'share' per unit, which can be seen as a situation where the unit ratio is determined. These concepts can also naturally be extended to the case of (fraction)÷(fraction) by some problem posing situations. That is to say, the case of (fraction)÷(fraction) can be deduced the case (natural number)÷(natural number) by the re-statement of the problem.

• Preventive Nutrition and Food Science
• /
• 제11권1호
• /
• pp.6-9
• /
• 2006

This study was conducted to evaluate the antioxidant activity of each fraction from Sedum sarmentosum. Antioxidant activity of each fraction was measured using the DPPH radical assay, the ferric thiocyanate (FTC) method, and thiobarbituric acid (TBA) method. The antioxidant activities were then compared with that of BHT(synthetic antioxidant). The ethyl acetate and butanol fractions were found to have significant DPPH radical scavenging activity, with scavenging potencies showing 90.61 % and 87.02%, respectively. Total phenolic compound contents, determined according to the Folin-Denis method, were found to be in the order of ethyl acetate>butanol>ethanol>chloroform>aqueous fraction. From the results, we have been able to establish a positive correlation between the antioxidant activity and the total phenolic compound content of the sample. The antioxidant activity in a linoleic acid system was measured using the ferric thiocyanate (FTC) method and thiobarbituric acid (TBA) method. The ethyl acetate fraction had the highest antioxidant activity among the tested fractions. On the basis of these results, the ethyl acetate fraction provided equivalent or higher antioxidant activity as compared to BHT. These results suggest that Sedum sarmentosum is a potentially useful antioxidant for foods, cosmetics, and medicine.

• 한국주조공학회지
• /
• 제14권5호
• /
• pp.438-446
• /
• 1994

The effect of various thermomechanical treatments on the structure and rheological behaviour of Al-6.2wt%Si alloy in its solidification range were investigated using a Searle type high temperature viscometer. During continuous cooling, the viscosity increases gradually with increasing fraction of solidified alloy, until a critical fraction of solidified alloy is reached above which the viscosity sharply increases. The viscosity of the slurry, at a given volume fraction wolid, decreased with increasing shear rate. The size and morphology of primary solid particles during stirring is influenced strongly by shear rates, cooling rates, volume fraction and stirring time of solid. Morphological changes during stirring as a function of solid volume fractions, shear rate and processing time were also reported. In this study, the size of primary solid particles in these alloys consistently increases and the it`s aspect ratio decrease with the increase in fraction solid and decrease in shear rate. Crystal morphology changes from rosette type to spheroid type with the increase in shear rate and solid fraction.