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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.
Lee, Hyun Ah,Song, Bo Ram,Kim, Hye Ryeong,Kim, Ji Eun,Yun, Woo Bin,Park, Jin Ju,Lee, Mi Lim,Choi, Jun Young,Lee, Hee Seob,Hwang, Dae Youn D.A. Spandidos 2017 Experimental and therapeutic medicine Vol.14 No.5
<P>Roots of <I>Asparagus cochinchinesis</I> have been widely used to treat fever, cough, kidney disease, breast cancer, inflammatory and brain disease, although the effects of their fermented products have not been assessed until now. To investigate the anti-inflammatory effects on macrophages of a butanol extract from <I>A. cochinchinensis</I> roots fermented with <I>Weissella cibaria</I> (BAW), alterations in the inducible nitric oxide synthase (iNOS)-mediated cyclooxygenase-2 (COX-2) induction pathway and inflammatory cytokine expression were measured in lipopolysaccharide (LPS)-activated RAW264.7 cells following pretreatment with BAW. Briefly, <I>W. cibaria</I> was selected from two bacterial strains for the fermentation of <I>A. cochinchinensis</I> roots based on its hyaluronidase inhibition and NO suppression rates. Following fermentation with <I>W. cibaria</I>, the level of various key components including total phenols and protodioscin were significantly enhanced in BAW. In addition, BAW exhibited high free radical scavenging activity (IC<SUB>50</SUB>=31.62 µg/ml) and induced a decrease of intracellular ROS production in RAW264.7 cells following DCFH-DA staining. Significant suppressions in the expression level of important members of the iNOS-mediated COX-2 induction pathway and the phosphorylation of mitogen-activated protein kinase members were detected. The expressions of pro-inflammatory and anti-inflammatory cytokines were recovered in BAW pretreated RAW264.7 cells. Overall, these results suggest that BAW may suppress inflammatory responses through differential regulation of the iNOS-mediated COX-2 induction pathway and inflammatory cytokine expressions in LPS-activated RAW264.7 cells.</P>
Ryeong Ha Kwon,Heon-Woong Kim,Suji Lee,So-Jeong Lee,Hyemin Na,Ju Hyung Kim,Chi-Do Wee,Seon Mi Yoo,Sang Hoon Lee 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
In this study, shoots and leaves of Acanthopanax senticosus (AST) were analyzed to identify triterpenoid saponins using UPLC-DAD-QToF/MS. The forty-three of saponins were isolated and identified by six standard compounds and published data (library) and the seventeen of saponins were tentatively confirmed for the first time as new compounds. According to aglycone types, triterpenoid saponins in shoots and leaves were classified to oleanane (mesembryanthemoidigenic acid, echinocystic acid, hederagenin, oleanolic acid), noroleanane (akebonic acid), lupane (chiisanogenin) classes. These saponins possessed structures in which arabinose (Ara, m/z 132), rhamnose (Rham, m/z 146), glucose and galactose (Glu and Gal, respectively, m/z 162) were bonded to C-3 of each aglycone and Rham-2Glu (m/z 470) or Rham-(acetyl)Glu-Glu (m/z 512) were bonded to C-28. The MS fragment pattern and intensity of the compounds were the crucial factors that tentatively identified to sugar type and position. It was the fundamental data that the result of composition of AST saponins support in future activity research and functional product development.
Fabrication of Core-Shell Structured Ni-Based Alloy Nanopowder by Electrical Wire Explosion Method
Lee, A-Young,Lee, Gwang-Yeob,Oh, Hye-Ryeong,Kim, Hyeon-Ah,Kim, Song-Yi,Lee, Min-Ha The Korean Powder Metallurgy Institute 2016 한국분말재료학회지 (KPMI) Vol.23 No.6
Electrical wire explosion in liquid media is a promising method for producing metallic nanopowders. It is possible to obtain high-purity metallic nanoparticles and uniform-sized nanopowder with excellent dispersion stability using this electrical wire explosion method. In this study, Ni-Fe alloy nanopowders with core-shell structures are fabricated via the electrical explosion of Ni-Fe alloy wires 0.1 mm in diameter and 20 mm in length in de-ionized water. The size and shape of the powders are investigated by field-emission scanning electron microscopy, transmission electron microscopy, and laser particle size analysis. Phase analysis and grain size determination are conducted by X-ray diffraction. The result indicate that a core-shell structured Ni-Fe nanopowder is synthesized with an average particle size of approximately 28 nm, and nanosized Ni core particles are encapsulated by an Fe nanolayer.