• Title/Summary/Keyword: fraction as a ratio

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Effect of steel fiber volume fraction and aspect ratio type on the mechanical properties of SIFCON-based HPFRCC

  • Kim, Seugnwon;Jung, Haekook;Kim, Yongjae;Park, Cheolwoo
    • Structural Engineering and Mechanics
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    • v.65 no.2
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    • pp.163-171
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    • 2018
  • Plain concrete is a brittle material with a very low tensile strength compared to compressive strength and critical tensile strain. This study analyzed the dynamic characteristics of high-performance fiber-reinforced cementitious composites based on slurry-infiltrated fiber concrete (SIFCON-based HPFRCC), which maximizes the steel-fiber volume fraction and uses high-strength mortar to increase resistance to loads, such as explosion and impact, with a very short acting time. For major experimental variables, three levels of fiber aspect ratio and five levels of fiber volume fraction between 6.0% and 8.0% were considered, and the flexural strength and toughness characteristics were analyzed according to these variables. Furthermore, three levels of the aspect ratio of used steel fibers were considered. The highest flexural strength of 65.0 MPa was shown at the fiber aspect ratio of 80 and the fiber volume fraction of 7.0%, and the flexural strength and toughness increased proportionally to the fiber volume fraction. The test results according to fiber aspect ratio and fiber volume fraction revealed that after the initial crack, the load of the SIFCON-based HPFRCC continuously increased because of the high fiber volume fraction. In addition, sufficient residual strength was achieved after the maximum strength; this achievement will bring about positive effects on the brittle fracture of structures when an unexpected load, such as explosion or impact, is applied.

Elemental Analysis of Road Aerosols using by a PIXE Method (PIXE 분석법에 의한 도로변 분진의 원소분석)

  • 최금찬;임경택;조정구;김태형
    • Journal of Korean Society for Atmospheric Environment
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    • v.12 no.5
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    • pp.523-528
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    • 1996
  • Aerosol Particles were collected in a heaby traffic region in pusan. Samples were collected in two size fractions with a two-stage sampler during the day and the night. Elemental concentrations of these aerosol particles were determined by a PIXE(Proton Induced X-ray Emission) analysis method. The results suggest that the elements originating mainly from natural sources such as Si, Ca, Fe, Cl, and K are dominent in the coarse fraction, but the elements such as S, Pb, Br, and Zn are dominent in the fine fraction. Br/Pb ratio are evaluated in both coarse and fine size fraction, and which are mainly emitted automobile sources. The study further also discussed other Br/Pb ratio related works described elsewhere. Sulfur in the fine fraction was continuously increased during the sampling period without time variation.

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Development of Estimation of Model for Mechanical Properties of Steel Fiber Reinforced Concrete according to Aspect Ratio and Volume Fraction of Steel Fiber (강섬유의 형상비와 혼입률에 따른 강섬유 보강 콘크리트 보의 역학적 특성 추정 모형 개발)

  • Kwak, Kae-Hwan;Hwang, Hae-Sung;Sung, Bai-Kyung;Jang, Hwa-Sup
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.3
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    • pp.85-94
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    • 2006
  • Practially useful method of steel fiber for construction work is presented in this study. The most important purpose of this study is to develop a model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus, and splitting strength were performed with self-made cylindrical specimens of variable aspect ratios and volume fractions. The experiment showed that compressive strength was not in direct proportion to volume fraction which doesn't seem to have great influence over compressive strength. However, splitting strength showed almost direct proportion to aspect ratio and volume fraction. Improvement of optimal efficiency was confirmed when the aspect ratio was 70. Experiments on flexural strength, fracture energy, and characteristic length were carried out with self-manufactured beams with notch. As a result, increases of flexural strength, fracture energy, and characteristic length according to increase of volume fraction tend to be prominent when aspect ratio is 70. The steel fiber improves concrete to be more ductile and tough. Moreover, regression analysis was the performed and predictable model was developed after determining variables. With comparison and analysis of suggested estimated values and measured data, reliance of the model was verified.

An Comparative Analysis of Fraction Concept in Mathematics Textbooks of Korea and Singapore (싱가포르와 우리나라 교과서의 비교 분석을 통한 분수 개념 지도 방안 탐색)

  • Jeong, Eun-Sil
    • Journal of Educational Research in Mathematics
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    • v.19 no.1
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    • pp.25-43
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    • 2009
  • The fraction concept consists of various meanings and is one of the abstract and difficult in elementary school mathematics. This study intends to find out the implication for introducing the fraction concept by comparing mathematics textbooks of Korea and Singapore. Both countries' students peformed well in recent TIMMSs. Some implications are as follows; The term 'equal' is not defined and the results of various 'equal partitioning' activities can not easily examined in Korea's mathematics textbook. And contexts of introducing fractions as a quotient and a ratio are unnatural in Korea's mathematics textbook in comparison with Singapore's mathematics textbook. So these ideas should be reconsidered in order to seek the direction for improvement of it. And Korea's textbooks need the emphasis on the fraction as a measure and on constructing fraction concept by unit fraction.

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THE REPRESENTATION OF THE GOLDEN RATIO BY THE CONTINUED FRACTION

  • Kim, Seung Soo;Ko, Mi Yeon;Lee, Yong Hun
    • Honam Mathematical Journal
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    • v.36 no.1
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    • pp.103-112
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    • 2014
  • There are several theories to say that 'Mathematics is beautiful', but the typical one of them is a theory about the golden ratio. Often the golden ratio apt to be considered only as the geometric shapes or the simple number of ratio used in buildings and arts. However in this paper, we studied to consider the mathematical theories which are contained in their inside. In particular, we investigate the various expressions of the continued fraction which are represented by the golden ratio.

A Study on the Fraction as Quotient and Equal Sharing Strategies in Elementary Mathematics (몫으로서의 분수와 분배전략)

  • Lee, Hosoo;Choi, Keunbae
    • East Asian mathematical journal
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    • v.38 no.4
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    • pp.379-396
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    • 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.

Evaluation of Physical Characteristics of Discovery ST scanner Using NEMA NU2-2001 Standard (NEMA NU2-2001을 이용한 PET-CT 스캐너의 물리적 특성평가)

  • Lee, Byeong-Il
    • Journal of Integrative Natural Science
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    • v.1 no.2
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    • pp.79-83
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    • 2008
  • As a new standard for performance measurement, NEMA NU2-2001 was presented recently. In this study, I investigated the spatial resolution, sensitivity, scatter fraction, and noise equivalent count ratio (NECR) in order to know the information of physical characteristics and system performance of GE discovery ST using this new standard. Bismuth germinate crystals ($6{\times}6$ array, $6.3mm{\times}6.3mm{\times}30mm$) were used in discovery ST (energy window:375-650 keV, coincidence window:11.7 nsec). To measure the sensitivity, five aluminum sleeves (Data Spectrum Corp., Chapel Hill, NC., USA, thickness:1.25 mm)-NEMA sensitivity phantom- filled with F-18 solution were used. Successive measurements in 2D and 3D acquisition mode were made with a line source at the center of transaxial field of view and 10 cm off from the center until the count was over 500,000. Spatial resolution was estimated using a point source (F-18, 0.1 mCi) at different locations in the FOV. Scatter fraction and NECR was tested using a NEMA scatter phantom. Dynamic data were acquired for 7 half-lives using F-18 solution. And true to background ratio was averaged at last three frames when the random rate was as small as ignorable for the calculation of scatter fraction. We anticipate this overall evaluated results could be used for the quality assurance and optimized image acquisition for clinical research.

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A Critical Review on the Use of Cuisenaire Rods in Learning of Fraction (초등학교 분수 학습에서 퀴즈네어 막대 활용에 대한 비판적 고찰)

  • Lee, Jiyoung
    • The Mathematical Education
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    • v.56 no.2
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    • pp.193-212
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    • 2017
  • This study focuses on cuisenaire rods that can be used when teaching fractions to elementary school students. First of all, this study critically examines the use of cuisenaire rods in learning of fraction proposed by various researches. Then, based on this review, this study explores in detail the use of cuisenaire rods in teachers' manuals developed from the revised curriculum by 2009 and in lessons related to fraction. The results of this study show that there are subtle differences in how to use cuisenaire rods in learning fractions and these subtle differences have a significant impact on students' understanding of the fractions. Therefore, the teachers should be able to accurately grasp the differences and utilize appropriate methods for teaching purpose. The followings are some of the implications for teachers or textbook developers when using cuisenaire rods in fraction learning: First, we should use cuisenaire rods in ways that can fully exploit the interpretations of the fraction as a part-whole and the fraction as a ratio. Second, we should focus on quantitative reasoning with unit to determine what each cuisenaire rod refers to. Third, it is necessary to take a more careful and sensitive approach to the use of cuisenaire rods. Teachers and textbook developers should constantly explore ways to make good use of mathematical manipulatives to help students understand conceptually in fractional learning. Furthermore, when teaching various mathematical topics using different manipulatives, I expect that there will be sufficient discussions and specific studies on how to use each of these manipulatives.

The Fiber Damage and Mechanical Properties of Short-fiber Reinforced Composite Depending on Nozzle Size Variations in Injection/Mold Sides (단섬유강화 복합재료에서 사출측/금형측 노즐 크기 변화에 따른 섬유손상 및 기계적 성질)

  • Lee, In-Seop;Lee, Dong-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.4
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    • pp.564-573
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    • 2001
  • The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

소수의 역사적 기원과 의의

  • 강흥규;변희현
    • Journal for History of Mathematics
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    • v.16 no.3
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    • pp.69-76
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    • 2003
  • In this article, We explained the historical origin and significance of decimal fraction, and draw some educational implications based on that. In general, it is accepted that decimal fraction was first invented by a Belgian man, Simon Stevin(1548-1620). In short, the idea of infinite decimal fraction refers to the ratio of the whole quantity to a unit. Stevin's idea of decimal fraction is significant for the history of mathematics in that it broke through the limit of Greek mathematics which separated discrete quantity from continuous quantity, and number from magnitude, and it became the origin of modern number concept. H. Eves chose the invention of decimal fraction as one of the "Great moments of mathematics."The method of teaching decimal fraction in our school mathematics tends to emphasize the computational aspect of decimal fraction too much and ignore the conceptual aspect of it. In teaching decimal fraction, like all the other areas of mathematics, the conceptual aspect should be emphasized as much as the computational aspect.al aspect.

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