• 한국수학교육학회지시리즈A:수학교육
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• 제45권3호
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• pp.319-343
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• 2006

The purpose of this study is to investigate how fifth and sixth graders recognize average and to find out suggestions for teaching/learning methods of average by examining which difference there is depending on the way of the word problem presentation. For the this purpose, was conducted experiment study with the way of the world problem presentation set up as experimental treatment. The conclusions drawn from the results obtained in the this study were as follows : First, since students who did not learn the regular course of average had various informal concepts already, it is needed to consider handling more various concepts of average in order to enable students to expand flexible thoughts. Second, compared with fifth and sixth graders showed a wide difference in informal concepts of average depending on the way of the word problem presentation. In expect data with given average, concepts of mean as algorithm, balance point, and mode indicated similar percentage, while in estimate average with given data, the percentage of students who showed the concept of mean was very high at 67.6%. That may be because problems related to mean in the current textbooks are items of 'estimate average with given data', so in types of 'estimate average with given data', students solve questions with mean as algorithm without considering situations of problems. This result suggests that it is necessary to diversify the way of the word problem presentation even in textbooks. Third, as a result of analyzing informal concepts of average, there was significant difference in grades. In addition, the results suggested that there would be difference in the concepts of average depending on gender or attributes of discrete quantity and continuous quantity.

• 가정과삶의질연구
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• 제30권3호
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• pp.193-208
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• 2012

The purpose of this study is to suggest basic data on the education of traditional living culture and seasonal customs. In order to achieve the purpose of this study, a research questionnaires consisting of 46 questions was developed. The data was collected by 287 child caregivers in Incheon Metropolitan City. and the data analysis was conducted with the SPSS/Win 17.0 program. The results of this study, they are summarized as follows. First, child caregivers overall perception of the traditional life and culture was scored as 3.28. Their perception of the need for education on traditional life and culture was scored as 3.7, and their knowledge and interest both as 2.77. The analysis of difference according to background variables revealed, significant difference in educational experience (p. <05) and age (p. <01). Second, the child caregivers were unaware any other seasonal customs besides Chuseok(Korean Thanksgiving), Tano(a festival occurring on the fifth day of the fifth month of the lunar calendar), Lunar New Year's Day, and Daeboreum (the day of the first full moon of the year) Third, child caregivers perceived 'culture' experiences as being very important for education about seasonal customs. Forth, two of Korea's seasonal customs, Chuseok(Korean Thanksgiving) and the Lunar New Year's Day have always been celebrated with family gatherings. Fifth, child caregivers awareness of seasonal customs is correlated with educational training. And their awareness of the traditional living culture is also correlated with educational training.

• 대한영양사협회학술지
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• 제6권1호
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• pp.44-52
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• 2000

Two hundred sixty six children were retrospectively surveyed from first to fifth grade to find out the status of obesity during four years. The obesity index was gained by height and weight data from student's health file and the data about eating behaviors and weight control behaviors, etc. were collected by questionnaires. Children assigned to one of the following groups : underweight, normal, overweight and obese. The results were as follows ; 1. Obese children were 18.6%(n=27) of boys and 10.8%(n=13) of girls at fifth grade. 2. Twenty eight children among forty obese children at fifth grade were also overweight or obese at first grade, and the other twelve was normal. 3. Breakfast skipping rate was significantly high among underweight and obese group of boys(p<0.01).The most children(87.6%) had prejudice for special foods. 4. The rate of agreement between obesity index and self recognition of body image was 60.7% in boys and 63.6% in girls. 5. Forty two point five percent of children have ever tried weight control as exercise(35.7%), reducing sugars and snacks(27%), fasting(23.8%), avoiding fatty foods(12.7%), taking diet food or drug(0.8%). In conclusion, the prevalence of children obesity is gradually increasing and children tried weight control without right guidances. In order to prevent progress into adulthood obesity, nutrition education should be followed with school foodservice including the right perception for obesity, proper weight control and eating behavior modification.

• 대한수학회보
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• 제55권3호
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• pp.881-898
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• 2018

This article deals with implementation of a high-order finite difference scheme for numerical solution of the incompressible Navier-Stokes equations on curvilinear grids. The numerical scheme is based on pseudo-compressibility approach. A fifth-order upwind compact scheme is used to approximate the inviscid fluxes while the discretization of metric and viscous terms is accomplished using sixth-order central compact scheme. An implicit Euler method is used for discretization of the pseudo-time derivative to obtain the steady-state solution. The resulting block tridiagonal matrix system is solved by approximate factorization based alternating direction implicit scheme (AF-ADI) which consists of an alternate sweep in each direction for every pseudo-time step. The convergence and efficiency of the method are evaluated by solving some 2D benchmark problems. Finally, computed results are compared with numerical results in the literature and a good agreement is observed.

• ETRI Journal
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• 제29권4호
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• pp.452-456
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• 2007

Very compact 4-channel 200-GHz-spacing external cavity lasers (ECLs) were fabricated by hybrid integration of reflection gratings and superluminescent laser diodes on a planar lightwave circuit chip. The fifth-order gratings as reflection gratings were formed using a conventional contact-mask photo-lithography process to achieve low-cost fabrication. The lasing wavelength of the fabricated ECLs matched the ITU grid with an accuracy of ${\pm}0.1$ nm, and optical powers were more than 0.4 mW at the injection current of 80 mA for all channels. The ECLs showed single mode operations with more than 30 dB side lobe suppression.

• 대한전자공학회논문지
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• 제12권2호
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• pp.31-42
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• 1975

접지-비접지 FDNR자을 구성하는 새로운 방법을 고안하였으며 이것과 admittance변환함수가 s3에 비례하는 CGIC를 교대로 사용하면 분모 분자의 저차항부터 3개항씩 동시에 실현할 수 있는 새로운 개방전압전달함수합성방법을 제시하였다. 종전의 두 개항씩을 구분하여 나가는 방식과는 달리 3개항을 구분하여 나가므로 임의의 고차의 전달함수실현이 용이하여진다. 실지로 여파특성을 가지는 5차의 전달함수를 이 방법으로 실현하고 그 특성을 검토함으로써 본방법의 타당성을 확인하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.327-332
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• 1999

In this paper, six harmonic injection PWM method for reducing total harmonic distortion in single switch three phase discontinuous conduction mode boost converter is presented. In the proposed method, periodic six harmonic voltage is injected in the control circuit to vary the duty ratio of the converter switch within a line cycle so that the fifth order harmonic of the input current is reduced. Experimental results are verified by converter operating at 400V/6kW with three phase 140V~220V input.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1195-1209
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• 2009

In this paper, we point out some errors in a recent paper by Cordero and Torregrosa [7]. We prove the convergence of the variants of Newton's method for solving the system of nonlinear equations using two different approaches. Several examples are given, which illustrate the cubic convergence of these methods and verify the theoretical results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1624-1626
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• 2004

On the 105th year of the Korean Railroad, Korea railroad is at the advent of the high speed operation with an commercial operation of KTX(Korea Train eXpress), the fifth high speed line in the world, between Pusan and Seoul at the speed of 300km/hr. In order to enhance nation competitiveness in $21^{st}$ century, Korea Railroad is faced with a task of improving the railroad network in the areas of new line constructions, betterment of existing rail lines, increasing the operation speed and transportation capacity and modernization of rolling stock fleet.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1863-1866
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• 2002

This paper describes synthesis of a complex R$^{i}$ CR filter with a finite transmission zero except zero frequency. First, a new kernel function is proposed. Secondly, how to determine the element values included in the R$^{i}$ CR filter is described. A fifth-order R$^{i}$ CR filter is designed. Finally, the sensitivity property of the proposed filter is evaluated through computer simulation.