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Grain Boundary Diffusion of La Based Low-melting Alloy to Nd-Fe-B Sintered Magnets
Ye Ryeong Jang,Hyungju Lee,Jaeryung Lee,Hyun-Sook Lee,Wooyoung Lee 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
The high-performance Nd-Fe-B magnets have been widely used in many different applications, such as motors, generators, actuators, hard disk drives, and communication devices, since their discovery in 1894. In order to improve the performance of Nd-Fe-B magnets, grain boundary diffusion process is carried out by using heavy rare-earth element (HRE) such as Dy or Tb. Many efforts have been made to prepare high-performance Dy/Tb diffused Nd-Fe-B sintered magnets. However, these heavy rare-earth elements (Dy, Tb) have a problem that prices and supply are unstable. In this study, we have investigated the magnetic properties of Light rare-earth element (LRE) diffused Nd–Fe–B magnets. The alloys containing less expensive rare-earth element and low-melting metals work effectively as diffusion sources. Metals or compounds with low melting points can modify boundary structure by improving the wettability between intergranular phases and matrix phases. La based alloys effectively diffused along grain boundary phases and formed non-ferromagnetic phases, improving exchange decoupling and enhancing the coercivity. In order to analyze the microstructures, we use scanning electron microscopy. It is expected to provide solutions for cost reduction of GBDP and NdFeB magnets production by saving rare-earth resource. (See text for figure)
담배연기와 담뱃잎 내 함유된 방사능 농도분석 및 위해도 평가
이세령(Se-Ryeong Lee),이상복(Sang-Bok Lee),김정윤(Jeong-Yoon Kim),김지민(Ji-Min Kim),방예진(Yei-jin Bang),이두석(Doo-Seok Lee),조형준(Hyung-Joon Jo),김성철(Sungchul Kim) 대한방사선과학회(구 대한방사선기술학회) 2021 방사선기술과학 Vol.44 No.5
In this study, radioactivity quantitative analysis was performed on radon contained in cigarette, and the effective dose was calculated using the result value to determine the amount of exposure caused by smoking. A total of 5 types of cigarettes were sampled. Cigarette smoke was collected by using activated carbon, and tobacco were measured by homogenizing for quantitative analysis. For each sample, Bi-214 and Pb-214 were subjected to gamma nuclide analysis to observe the uranium-based radioactive material contained in cigarette, and a measurement time of 30,000 seconds was set for the sample based on the results of previous studies. As a result of measuring the radioactivity of tobacco, a maximum of 0.715 Bq/kg was derived, and in the case of cigarette smoke measured using activated carbon, a maximum of 3.652 Bq/kg was derived. Using this measurement, the average effective dose to the lungs is 0.938 mSv/y, and it was found that there is a possibility of receiving exposure up to 1.099 mSv/y depending on the type of tobacco. It was found that the exposure dose due to cigarette occupies a large proportion of the annual effective dose limit for the general public. Therefore, more diverse studies on radioactive substances in cigarette are needed, and measures to monitor and reduce the incidental exposure to radon should be established.
Weak Hyponomal Composition Operators Induced by a Tree
Lee, Mi-Ryeong,Ahn, Hyo-Gun Department of Mathematics 2010 Kyungpook mathematical journal Vol.50 No.1
Let g = (V, E, ${\mu}$) be a weighted directed tree, where V is a vertex set, E is an edge set, and ${\mu}$ is ${\sigma}$-finite measure on V. The tree g induces a composition operator C on the Hilbert space $l^2$(V). Hand-type directed trees are defined and characterized the weak hyponormalities of such C in this note. Also some additional related properties are discussed. In addition, some examples related to directed hand-type trees are provided to separate classes of weak-hyponormal operators.
Construction of Logarithmic Spiral-like Curve Using G2 Quadratic Spline with Self Similarity
Ryeong Lee, Young Joon Ahn 조선대학교 기초과학연구원 2014 조선자연과학논문집 Vol.7 No.2
In this paper, we construct an logarithmic spiral-like curve using curvature-continuous quadratic spline and quadratic rational spline. The quadratic (rational) spline has self-similarity. We present some properties of the quadratic spline. Also using this G2 quadratic spline, an approximation of logarithmic spiral is proposed and error analysis is obtained.
Crystallinity-dependence of ionic conductivity in the ion pairs of a multi-interactive anion
Lee, Gil Ryeong,Ohtsu, Hiroyoshi,Koo, Jinyoung,Yakiyama, Yumi,Park, Moon Jeong,Inoue, Daishi,Hashizume, Daisuke,Kawano, Masaki The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.20
<P>Ammonium and sodium salts (ion pairs) of a multi-interactive tri-(4-pyridyl) hexaazaphenalenyl anion (TPHAP(-)) showed completely different ion-conductive properties depending on the crystal structure. TPHAP columnar crystals showed a high conductivity of 10(-3) S cm(-1) while retaining their structures even under humid conditions, whereas TPHAP dimer crystals exhibited a conductivity of similar to 10(-5) S cm(-1) with crystallinity deterioration. The main unit structures induced by multi-interactivity realized different water accessibility, which explains the differences in their ion conductivity and stability against humidity.</P>
The Correlation Dimensions of Loosely Self-Similar Sets
Lee, Mi-Ryeong ... et al KYUNGPOOK UNIVERSITY 2000 Kyungpook mathematical journal Vol.40 No.2
For a given loosely self-similar set K which is generated by a sequence of similarity maps, we define the push-down measure ν on K and calculate the correlation dimension of K with respect to the measure ν. It is just the same as the Hausdorff dimension of K.
웹을 이용한 장애 아동의 사회화 촉진 총괄체계 구축 : 일상생활 기능증진 웹지원 시스템
이상복,이원령,변찬석,서경희,전헌선,이민호,김춘희,문혜숙 대구대학교 특수교육재활과학연구소 2005 특수교육재활과학연구 Vol.44 No.4
The purpose of this study was to evaluate children development in the residental facilities and to analyze data according to their subordinate types and sex. Subjects were 56 children with disabilities, that consisted of 51% boys and 49% girls. The results were as follows: First, we developed a scale on adaily life, basic leaning cognitive abilities, emotion-behavior, communication, and body development. It was the Web-supported system on the internet. Second, we tried to analyze the developmental characteristics of children in the residental facilities according to the subordinate types. There were 41% in a daily life, 18% in basic leaning cognitive abilities, 9% in emotion-behavior, 0% in communication, 43% in body development who exceeded the standard. Third, we tried to see the developmental characteristics according to sex. The boy distribution was found higher and more widespread in the various types than the girl one. However, there is some limitation on the results, because we treated only one residental facilities. 본 연구는 생활시설에 거주하고 있는 장애아동 56명을 대상으로 인터넷을 통한 발달평가를 실시하여 그 결과를 발달평가 하위영역과 성별로 나누어 분석하였다. 이에 대한 결과는 다음과 같다. 첫째, 발달특성을 평가하기 위하여 일상생활, 기초학습 인지능력, 정서행동, 의사소통, 신체발달 등 5가지 하위영역으로 구성된 척도를 개발하여, 인터넷을 통해 웹지원 시스템을 구축하였다. 둘째, 생활시설에 거주하는 아동이 어떤 발달특성을 보이는지 알아보았다. 일상생활에서는 기준을 초과한 아동의 비율이 41%, 기초학습 인지능력에서는 기준을 초과한 아동이 18%, 정서행동에서는 기준을 초과한 아동이 9%, 의사소통에서 기준을 초과한 아동은 0%, 신체발달에서는 기준을 초과한 아동이 43%로 나타났다. 셋째, 아동의 발달특성이 성별에 따라 어떤 특성을 보이는지 알아보았다. 전체적으로 남자아동의 영역별 분포는 여자아동의 분포보다 상대적으로 크고 넓게 분포되어 있음을 알 수 있었다. 그러나 본 연구는 생활시설 한 곳만을 연구대상으로 하였기 때문에 결과를 일반화하기에는 제한점을 가지고 있다.