• 한국초전도ㆍ저온공학회논문지
• /
• 제21권2호
• /
• pp.10-14
• /
• 2019

In order to improve resource value, separation of nonferrous metals obtained from crushed materials of home appliances is required. In this study, we aimed to develop a continuous separation system by magneto-Archimedes method using magnetic fluid as a medium and the permanent magnet as a magnetic field source. Firstly, the separation conditions were examined in which only copper is settled and the difference in levitation positions between aluminum and other metals are over 1 cm. Based on the results, levitation experiment of each metal and separation experiment from the mixture of nonferrous metals were confirmed. The separation experiment showed that the continuous separation of copper and aluminum from a mixture of nonferrous metals is possible.

• 대한수학회보
• /
• 제50권6호
• /
• pp.2103-2114
• /
• 2013

Archimedes knew that the area between a parabola and any chord AB on the parabola is four thirds of the area of triangle ${\Delta}ABP$ where P is the point on the parabola at which the tangent is parallel to AB. We consider whether this property (and similar ones) characterizes parabolas. We present five conditions which are necessary and sufficient for a strictly convex curve in the plane to be a parabola.

• 한국초전도ㆍ저온공학회논문지
• /
• 제14권4호
• /
• pp.1-4
• /
• 2012

The applicability of the two types of magnetic separation system, high gradient magnetic separation (HGMS) and Magneto Archimedes method were studied considering the magnetic susceptibility of targeted substances. It was noted that the combination of the two methods can control the almost all the substances, paramagnetic and diamagnetic in addition to ferromagnetic substances. The principle of the methods was given and the conceput of the magnet force control technology is discussed. The practical applications of the technique were introduced together with the new application of HGMS.

• 한국수학교육학회지시리즈A:수학교육
• /
• 제59권2호
• /
• pp.131-146
• /
• 2020

원의 넓이를 구하는 공식을 보면, 일반적으로 원주율이 반지름의 길이의 제곱의 앞에 쓰여 지지만 독일과 프랑스에서 원주율이 뒤에 쓰여 진 경우가 있었다. 본 연구에서는 두 가지를 연구 한다: 첫째, 원주율을 뒤에 쓰는 학생이 얼마나 있는가? 둘째, 학생들이 원의 넓이를 구하는 공식에서 문자 표기 순서에 대해 어떻게 인식하는가? 국내의 만 14세에서 만 21세까지의 사람들 중 임의 추출한 201명에 대한 온라인 설문 조사 결과 둘 다 가능하다 또는 뒤에만 가능하다는 인식이 86% 이상 있었다. 본 연구에는 원의 넓이에 대한 일반적인 문자 표기 순서와 학교 교육을 통해 자연스럽게 형성된 학생들의 인식에 차이가 있음이 보여 진다. 덧붙여 만 14세에서 만 16세까지의 학생들은 원주율을 뒤에만 써야한다는 인식이 더 강했으나 그 연령대 이후로 둘 다 가능하다는 인식의 변화가 있었다. 이러한 관점에서 의미의 혼동이 없다면, 두 표기 모두 가능하다는 것이 가장 공통적인 인식이 될 수 있다. 그러므로 교과서에는 원주율을 뒤에 쓴 표현이 추가된 방식으로 표현되어야 학생들의 이해가 더 자연스러울 것이다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.408-409
• /
• 2008

This paper presents a new development for topology optimization of heat-dissipating structure with forced convection. To cool down electric devices or machines, two types of convection models have been widely used: Natural convection model with a large Archimedes number and Forced convection with a small Archimedes number. Nowadays, many engineering application areas such as electrochemical conversion device or fuel cell devices adopt the forced convection to transfer generated heat. Therefore, to our knowledge, it becomes an important issue to design flow channels inside which generated heat transfer. Thus, this paper studies optimal topological designs considering fluid-heat interaction. To consider the effect of the advection in the heat transfer problem, the incompressible Navier-stokes equation is solved. This paper numerically studies the coupling phenomena and presents optimal channel design considering forced convection.

• Kyungpook Mathematical Journal
• /
• 제55권2호
• /
• pp.473-484
• /
• 2015

Archimedes determined the center of gravity of a parabolic section as follows. For a parabolic section between a parabola and any chord AB on the parabola, let us denote by P the point on the parabola where the tangent is parallel to AB and by V the point where the line through P parallel to the axis of the parabola meets the chord AB. Then the center G of gravity of the section lies on PV called the axis of the parabolic section with $PG=\frac{3}{5}PV$. In this paper, we study strictly locally convex plane curves satisfying the above center of gravity properties. As a result, we prove that among strictly locally convex plane curves, those properties characterize parabolas.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
• /
• pp.583-589
• /
• 2004

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fan has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control of the size and position, is the important cause of performance decrease. In this study, experiments are carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to research the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spital, which is the important factor haying an effect on it.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.391-396
• /
• 2003

A cross-flow fan relatively produces higher dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. The performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, and 15% by the heat exchanger. At the low flow rate, there exist a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. The purpose of this study is to investigate the reciprocal relation among each parameter Experiments are conducted to study the effects of a rearguider and a diameter ratio of impeller on the performance analysis of a cross-flow fan. Comparing with the rearguider of radial type, the Archimedes type shows excellent results for various diameter ratios.

• 대한수학교육학회지:학교수학
• /
• 제18권1호
• /
• pp.215-229
• /
• 2016

본 연구는 무한 등비급수의 합을 구하는 Archimedes의 상승적 아이디어를 소개하고 분배 상황을 이용하여 이를 은유적으로 확장하였다. Archimedes의 아이디어에 대한 은유적 확장 모델은 현행 고등학교 수준에서 강조되는 극한 개념의 동적 측면에 상보적으로 작동할 수 있는 정적인 특징을 갖고 있으며 중학교 수준에서 $0.999{\cdots}=1$임을 설명할 때 현행 교과서에서 대수적 무한 유추에 기반하여 유도하고 있는 식 $0.999{\cdots}=9/(10-1)$에 새로운 의미를 불어넣을 수 있는 장점이 있다. 실제로 중학교 2학년 영재학생들을 대상으로 한 본 연구자의 수업에서 은유적으로 확장된 모델은 구체적인 분배 상황을 통해 위의 식을 문맥화 함으로써 학생들의 흥미를 유발하였고 창의성과 오류를 이끌어 낼 수 있는 학습 환경을 제공하였다.

• 한국수학사학회지
• /
• 제13권1호
• /
• pp.27-32
• /
• 2000

Reasonable Mathematics New Issues are more elaborate in dealing with the mathematical problems and the methods of the mathematical thinking than the ways of mathematical meditative concentration of one's attentive calculation. They were written about one generation later as comparing the latter of the above. They also introduced the Archimedes' principle.