• Title/Summary/Keyword: Unit Fraction

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The Effects of Leaner-Centered Mathematical Instructions on Students' Reasoning Ability and Achievement (학습자 중심 수학 수업이 학생의 추론 능력과 학업성취도에 미치는 영향: 초등학교 4학년 분수 및 다각형 단원을 중심으로)

  • Cha, So-Jeong;Kim, Jinho
    • Education of Primary School Mathematics
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    • v.24 no.1
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    • pp.43-69
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    • 2021
  • The purpose of this study is to confirm the influences of learner-centered instruction on learners' achievement and reason ability. In order to accomplish them, the fraction unit and the polygonal unit in the fourth grade were implemented with teaching methods and materials suitable for learner-centered mathematics instruction. Some conclusions could be drawn from the results as follows: First, learner-centered mathematics instruction has a more positive effect on learning of learned knowledge and generating unlearned knowledge in the experimental period than teacher-centered instructions. Second, learner-centered instruction makes an influence of low learning ability on getting achievement positively. Third, as the experimental treatment is repeated, learner-centered instruction has a positive effect on students' reasoning ability. The reasoning ability of students showed a difference in the comparison between the experimental group and the comparative group, and within the experimental group, there was a positive effect of the extension of the positive reasoning ability. Fourth, it can be estimated that the development of students' reasoning ability interchangeably affected their generation test results.

A case study on the quadratic function problem solving process of middle school students with different unit coordination stages (단위 조정 단계가 다른 중학생의 이차함수 문제 해결 과정에서 나타나는 특징)

  • Lee, Jin Ah;Lee, Soo Jin
    • The Mathematical Education
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    • v.61 no.3
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    • pp.441-456
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    • 2022
  • The purpose of the current study is to report a part of our larger project whose focus is to understand a relationship between students' units coordination and K-12 school mathematics. In particular, in this paper we report how students who exhibit distinct levels of units coordinations used their knowledge of proportion to solve quadratic function problems of the form y = ax2. To this end, three 7th grade students all of whom assimiliated whole number problem situations with three levels of units but showed different levels for fraction problems were chosen. We carried out clinical interviews not only to understand their ability to coordinate units but to understand their problem solving process of proportion and the quadratic function problems. The analysis suggest that their abilities to coordinate units influenced their ways to solving proportion problems, and in turn influenced their ways to solve the specific form of quadratic functions. We have finalized our study by discussing how students' ability to construct and coordinate units, their proportion knowledge, and their knowledge associated with expressing the specific type of quadractic functions could be related.

Measurement of Pancreatic Fat Fraction by CT Histogram Analysis to Predict Pancreatic Fistula after Pancreaticoduodenectomy

  • Wonju Hong;Hong Il Ha;Jung Woo Lee;Sang Min Lee;Min-Jeong Kim
    • Korean Journal of Radiology
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    • v.20 no.4
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    • pp.599-608
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    • 2019
  • Objective: To evaluate the effectiveness of computed tomography (CT) Hounsfield unit histogram analysis (HUHA) in postoperative pancreatic fistula (PF) prediction. Materials and Methods: Fifty-four patients (33 males and 21 females; mean age, 65.6 years; age range, 37-89 years) who had undergone preoperative CT and pancreaticoduodenectomy were included in this retrospective study. Two radiologists measured mean CT Hounsfield unit (CTHU) values by drawing regions of interest (ROIs) at the level of the pancreaticojejunostomy site on preoperative pre-contrast images. The HUHA values were arbitrarily divided into three categories, comprising HUHA-A ≤ 0 HU, 0 HU < HUHA-B < 30 HU, and HUHA-C ≥ 30 HU. Each HUHA value within the ROI was calculated as a percentage of the entire area using commercial 3-dimensional analysis software. Pancreas texture was evaluated as soft or hard by manual palpation. Results: Fifteen patients (27.8%) had clinically relevant PFs. The PF group had significantly higher HUHA-A (p < 0.01) and significantly lower mean CTHU (p < 0.01) values than those of the non-PF group. The HUHA-A value had a moderately strong correlation with PF occurrence (r = 0.60, p < 0.01), whereas the mean CTHU had a weak negative correlation with PF occurrence (r = -0.27, p < 0.01). The HUHA-A and mean CTHU areas under the curve (AUCs) for predicting PF occurrence were 0.86 and 0.65, respectively, with significant difference (p < 0.01). The HUHA-A and mean CTHU AUCs for predicting pancreatic softness were 0.86 and 0.64, respectively, with significant difference (p < 0.01). Conclusion: The HUHA-A values on preoperative pre-contrast CT images demonstrate a strong correlation with PF occurrence.

A Study on the Cytotoxic Activity of Garlic(Allium Sativum) Extract Against Cancer Cells (마늘중 지용성 성분의 암세포증식 억제효과 연구)

  • 손흥수
    • Journal of Nutrition and Health
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    • v.23 no.2
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    • pp.135-147
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    • 1990
  • This study was devised to observe the cytotoxic activities of garlic extracts against various cancer cells, that is, murine leukemic lymphocyte(L1210 and P388) and human rectal(HRT-18) and colon cancer cells(HCT-48 and HT-29) in vitro, and murine ascitic tumor cell(S-180) in vivo. Each cell-line except S-180 was cultured in medium containing serial concentration of the garlic extract in vitro. Inhibitory effect n the growth rate of the cancer cells was stronger in extracts of petroleum ether than that of ethanol. A lipid soluble compound in the extracts of garlic was cytocidal to murine leukemic cells, human rectal and colon cancer cells in vitro. The growth rates of the cancer cells in medium containing garlic extracts were inhibited gradually to a significant degree in proportion to the increase of the extract concentration. The cytotoxic activity of garlic active fraction from TLC was about 2.3 times more potent than that of crude garlic extract, one unit of cytotoxic activity against L1210 cells being equivalent to 4.2$\mu\textrm{g}$ and 1.8$\mu\textrm{g}$ from the crude garlic and active fraction, respectively. The Rf value of the active fraction on silica-gel TLC was 0.18 in condition that petroleum ether/ethyl ether/acetic acid mixture(90:10:1, v/v/v) was used as a developing solvent. The survival times of mice inoculated with S-180 cells were extended about 1.5 to 2 times in the groups treated with garlic extract(through i.p. and oral administration) compared with their control group(no garlic extract treatment). Observations were carried out on S-180. Ethanol extracts of garlic injured markedly tumor cells within 3 hours after injection.

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Characteristics for Heavy Metal Pollution in Road Dust from Daebul Industrial Complex: Classification by Particle Size and Magnetic Separation (대불산업단지 도로먼지 내 중금속류 오염 특성: 입도와 자성에 따른 구분)

  • Jeong, Hyeryeong;Choi, Jin Young;Ra, Kongtae
    • Journal of Environmental Impact Assessment
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    • v.29 no.4
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    • pp.252-271
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    • 2020
  • In this study, we investigated physical and chemical properties such as grain size, heavy metal pollution, magnetic properties, and their environmental impacts of road dusts (RD) collected from 14 sampling points in Daebul industrial Complex. Heavy metal concentrations in RD were in the order of Fe>Zn>Cu>Pb>Cr>Ni>As>Cd>Hg, and this pollution pattern was related to major industries and traffic activities in this area. The results of the correlation analysis between heavy metal elements and particle size in RD showed that Fe and all of analyzed heavy metals had a significant correlation with each other and metal concentrations had a significantly negative correlation (p<0.05). However, due to the input of large metal particles some heavy metal concentrations in the particle fraction of >1000 ㎛ were highest. Pollution load per unit area of this fraction was the highest among the grain size fractions. Cr, Ni, Cu, Zn, Cd, Pb levels in RD decreased and the levels of Cr, Ni, Cu, Zn, Cd, and Pb were reduced to 85 (As) -22 (Ni)% of the whole after removal of MFs fraction from RD. The mean heavy metal levels in the study area did not exceed the soil contamination guide value of Korea, indicating that heavy metal levels in RD were not a concern. However, at some sampling points, Zn concentrations were exceeded the soil contamination guide value for the 3rd areas of Korea and this result indicated that further studies of the impact of RD on the surrounding environment through re-suspension or non-point pollution, and of effective management methods are required.

Pressure Distribution over Tube Surfaces of Tube Bundle Subjected to Two-Phase Cross-Flow (이상 유동에 놓인 관군의 표면에 작용하는 압력 분포)

  • Sim, Woo Gun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.1
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    • pp.9-18
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    • 2013
  • Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

An Analytical Study on Drawbacks Related to Contents Handled in Elementary Mathematics Textbooks in Korea (우리나라 초등학교 수학 교과서에서 취급하는 내용과 관련한 문제점 분석)

  • Park, Kyo Sik
    • School Mathematics
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    • v.18 no.1
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    • pp.1-14
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    • 2016
  • In this paper, in order to lay the foundation for clearly determining the scope of contents handled in elementary math textbooks in Korea, what may be issues are discussed with respect to the contents handled in the current math textbooks. First of all, handling of percent point, concave polygons, and possibilities of event that will happen are discussed, the handling of them can be a issue in the sense of inconsistencies to the curriculum. Next, handling of fractions attaching units of discrete quantities and fractions attaching 'times' are discussed, the handling of them can be a issue in the sense of gap between everyday life and definition in math textbooks. Finally, handling of representing natural numbers into fractions and the positional relationship of geometrical figures are discussed, the handling of them can be a issue in the sense of a logical jump. The following three implications obtained from these discussions are presented as conclusions. First, it is necessary to establish clearly the relationship of textbooks and curriculum. Second, it is necessary to give attention to using the way to define or deal with concepts in math textbooks mixed with the way to use them in everyday life. Third, it is necessary to identify and eliminate the logical jumps in math textbooks.

A Comparative Study of the Way of Introducing Fractions in Mathematics Textbooks of South and North Korea (남북한 초등학교 교과서의 분수 도입 방식 비교)

  • Park Kyo Sik;Lee Kyung Hwa;Yim Jae Hoon
    • Journal of Educational Research in Mathematics
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    • v.14 no.4
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    • pp.367-385
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    • 2004
  • This study intends to compare the way of introducing fractions in elementary mathematics textbooks of south and those of north Korea. After thorough investigations of the seven differences were identified. First, the mathematics textbooks of south Korea use concrete materials like apples when they introduce equal partition context, while those of north Korea do not use that kind of concrete materials. Second, in the textbooks of south Korea, equal partition of discrete quantities are considered after continuous ones are introduced. This is different from the approach of the north Korean text-books in which both quantities are regarded at the same time. Third, the quantitative fraction which refers to the rational number with unit of measure at the end of it, is hardly used in the textbooks of south. However, the textbooks of north Korea use it as the main representations of fractions. Fourth, in the textbooks of south Korea, vanous activities related to fractions are more emphasized, while in the textbooks of north Korea, various meanings of fractions textbooks from south and north Korea focused on the ways of introducing partition approach and equivalence relation as operational schemes of fractions, the following play an important role before defining fraction. Fifth, the textbooks of south Korea introduce equivalent fractions with number one using number bar, and do not consider the reason why that sort of fractions are regarded. On the contrary, the textbooks of north Korea introduce structural equivalence relation by using various contexts including length measure and volume measure situations. Sixth, whereas real-life contexts are provided for introducing equivalent fractions in the textbooks of south Korea, visual explanations and mathematical representations play an important role in the textbooks of north Korea. Seventh, the means of finding equivalent fractions are provided directly in the textbooks of south Korea, whereas the nature of equivalent fractions and the methods of making equivalent fractions are considered in the textbooks of north Korea.

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Evaluation of the antioxidant potential and enzyme activities in species of Rhus (옻나무류의 항산화력 및 항산화 효소 활성)

  • 정형진;김은희;이건주;정규영;임종국;유정민;심영은;박재호
    • Korean Journal of Plant Resources
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    • v.14 no.3
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    • pp.220-228
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    • 2001
  • Comparison of the antioxidant potential and enzyme activities of the extracts of Rhus showed considerable differences. The antioxidative activities of Rhus javanica were the highest of three species tried (7 $\mu\textrm{g}$/$m\ell$). The highest activities showed in fraction No.3 of 12 fractions by Sephadex LH-20 column chromatography and the antioxidative activity showed, in purified extract of each stem,1.5 $\mu\textrm{g}$/$m\ell$ (in Rhus verniciflua), 1.9 $\mu\textrm{g}$/$m\ell$ (in Rhus javanica) and 2.3 $\mu\textrm{g}$/$m\ell$ (in Rhus tricocarpa) respectively. These were identificated as phenolic compounds which are well known antioxidant compounds such as 2-propenoic acid (Caffeic acid), Benzoic acid (Gallic acid), 7-hydroxy- 6methoxy-2H-1-Benzopyran-2-one (Scopoletin). POD activities of stem were higher than leaf. Especially, POD activity in stem of Rhus javanica was 193 times higher than leaf. Rhus tricocarpa, however, showed very low POD activity. SOD activities of stem were higher than that of leaf in Rhus javanica and Rhus verniciflua but in Rhus tricocarpa, the activity of leaf was 25 times higher than that of stem.

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AMINO ACID DIGESTIBILITY AS AFFECTED BY VARIOUS FIBER SOURCES AND LEVELS 1. DIFFERENCE BETWEEN ILEAL AND FECAL DIGESTIBILITY OF AMINO ACIDS

  • Nongyao, A.;Han, In K.;Choi, Yun J.;Lee, N.H.
    • Asian-Australasian Journal of Animal Sciences
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    • v.3 no.4
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    • pp.347-351
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    • 1990
  • A simple cross-over design was used in digestion experiment carried out on finishing pig (70 kg body wt.) fitted with ileal T-cannula, to determine the difference between ileal and fecal digestible values as affected by various fiber sources and levels. The series of semi-purified diets were formulated in an attempt to meet 1, 3, 7 and 9% crude fiber level, with alfalfa meal (AFM), rubber seed meal (RSM), leucaena meal (LM) and cellulose. Both the levels and sources influenced the amino acid digestibilities, as increasing crude fiber level the digestibilities increased. The digestibilities of amino acids at ileal level were higher than at fecal level. The magnitude of response were ranged from 1.76 to 8.41 percentage unit or 4.86 by average. The dry matter digestibilities of the diets reflect the digestibilities of amino acids as accumulation of fiber would increase endogenous losses. It indicates that the digestibilities of amino acids varied irregularly among diets, probably depended on a dietary nutrient and individual fiber fraction contents.