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조남규,김현국,권기환,한창수,안유민,이성환,박균명 한국공작기계학회 2000 한국공작기계학회 추계학술대회논문집 Vol.2000 No.-
This paper describes the statistical analysis techniques for the surface roughness assessment of polished surfaces. In experiments, the polishing process of the sample surfaces which are manufactured by ball end mill is consist of two steps; the cusp removal process and the surface finishing process. For the cusp removal process, the criterion of cusp removal was established from the power spectrum analysis to assess the change of the cusp removal rate. For the finishing process, the surface was polished by the rotational CBN tool and vibration wood tool. And the surface quality of polished surface was assessed using the functional parameters based on the statistical values of surface profiles. Consequently, the surface finish performance of the polished surface using the vibration wood tool was improved.
( Chang Hyun Nahm ),( Seonki Lee ),( Sang Hyun Lee ),( Kibaek Lee ),( Jaewoo Lee ),( Hyeokpil Kwon ),( Kwang-ho Choo ),( Jung-kee Lee ),( Jae Young Jang ),( Chung-hak Lee ),( Pyung-kyu Park ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.3
Biofilm formation on the membrane surface results in the loss of permeability in membrane bioreactors (MBRs) for wastewater treatment. Studies have revealed that cellulose is not only produced by a number of bacterial species but also plays a key role during formation of their biofilm. Hence, in this study, cellulase was introduced to a MBR as a cellulose-induced biofilm control strategy. For practical application of cellulase to MBR, a cellulolytic (i.e., cellulaseproducing) bacterium, Undibacterium sp. DM-1, was isolated from a lab-scale MBR for wastewater treatment. Prior to its application to MBR, it was confirmed that the cell-free supernatant of DM-1 was capable of inhibiting biofilm formation and of detaching the mature biofilm of activated sludge and cellulose-producing bacteria. This suggested that cellulase could be an effective anti-biofouling agent for MBRs used in wastewater treatment. Undibacterium sp. DM-1-entrapping beads (i.e., cellulolytic-beads) were applied to a continuous MBR to mitigate membrane biofouling 2.2-fold, compared with an MBR with vacant-beads as a control. Subsequent analysis of the cellulose content in the biofilm formed on the membrane surface revealed that this mitigation was associated with an approximately 30% reduction in cellulose by cellulolytic-beads in MBR.
Nahm, Chang Hyun,Choi, Dong-Chan,Kwon, Hyeokpil,Lee, Seonki,Lee, Sang Hyun,Lee, Kibaek,Choo, Kwang-Ho,Lee, Jung-Kee,Lee, Chung-Hak,Park, Pyung-Kyu Elsevier 2017 Journal of membrane science Vol.526 No.-
<P><B>Abstract</B></P> <P>Quorum quenching (QQ) has been recognized as an innovative approach for biofouling control in membrane bioreactors (MBRs). Recently, QQ bacteria entrapping beads (QQ-beads) have been developed and verified to have excellent anti-biofouling potential in a pilot-scale MBR with flat-sheet membrane modules. In this study, considering the dense structure of hollow fiber (HF) bundles into which QQ-beads can hardly penetrate, QQ bacteria entrapping sheets (QQ-sheets) were developed as a new shape of QQ-media suitable for MBRs with HF modules. In a lab-scale MBR, QQ-sheets with a thickness of 0.5mm exhibited a greater physical washing effect than did QQ-beads with a diameter of 3.5mm because the former collided with membrane surfaces at the inner as well as the outer part of HF bundles, whereas the latter only made contact with the outer part. Moreover, QQ-sheets showed 2.5-fold greater biological QQ activity than did QQ-beads due to their greater total surface area at a fixed volume of QQ-media. These results suggest high potential for QQ-sheets to be used in MBRs with HF modules.</P> <P><B>Highlights</B></P> <P> <UL> <LI> QQ-sheets were developed to effectively mitigate biofouling in MBR with HF module. </LI> <LI> QQ-sheets effectively detached biofilm on both inner and outer part in HF module. </LI> <LI> QQ-sheets showed greater QQ activity than QQ-beads due to their higher surface area. </LI> <LI> The merits of QQ-sheets were confirmed in lab-scale continuous MBR with a HF module. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Sintering and Microstructure of BaTiO<sub>3</sub> Nano Particles Synthesized by Molten Salt Method
Lee, Chang-Hyun,Shin, Hyo-Soon,Yeo, Dong-Hun,Ha, Gook-Hyun,Nahm, Sahn American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.5
<P>In order to establish thinner dielectric layers in thick film electronic components such as MLCC (Multilayer ceramic capacitor), BaTiO3 nanoparticles have been utilized. However, studies on the synthesis of nanoparticles smaller than 20 nm, the characteristics of the BaTiO3 powder, and the powder's sintering are lacking. Therefore, this paper aims to synthesize BaTiO3 particles smaller than 20 nm by using the molten salt method and evaluate the microstructure and dielectric properties by varying the sintering temperature from 750 degrees C to 1200 degrees C. Through the molten salt method and by using KOH-KCI mixed salt, 20 nm BaTiO3 powder was synthesized at a low temperature of 150 degrees C. Sintering the pellets formed from the synthesized 20 nm BaTiO3 nano powder led to the observation of an unusual phenomenon where the particles grew to approximate sizes below 850 degrees C where densification progressed. At sintering temperatures above 950 degrees C, particles that expanded into rod shapes were observed and these particles were identified to be unreacted TiO2 based on the results of the EDX (Energy Dispersive X-ray Spectroscopy) analysis and phase analysis results.</P>
Post LGM Fluvial Environment and Palynological Changes of South Korea
Kim, Ju-Yong,Yang, Dong-Yoon,Bong, Pil-Yoon,Nahm, Wook-Hyun,Lee, Heon-Jong,Lee, Yung-Jo,Hong, Sei-Sun,Lee, Jin-Young,Kim, Jin-Wkan,Oh, Keun-Chang Korea Association For Quaternary Research 2003 제사기학회지 Vol.17 No.2
In Korea terrestrial fluvial sequences can be used as pedological and sedimentological markers indicating a millenium-scale environmental and climatic changes imprinted in fluvial sub-environments, which in turn are represented by the cyclicity of fluvial sands, backswamp organic muds, and flooding muds intercalations of frostcracked or dessicated brown paleosols. Post LGM and Holocene fluvial and alluvial sedimentary sequences of Korea are formed in such landscapes of coastal, floodplain, backswamp and hillslope areas. Among them, the most outstanding depositional sequences are fluvial gravels, sands and organic mud deposits in coastal, fluvial, or alluvial wetlands. The aim of this study is to explain the sedimentary sequences and palynofloral zones since the last 15,000years, on the basis of organic muds layers intercalated in fluvial sand deposits. Jangheung-ri site of Nam river, Soro-ri site of Miho river, Youngsan rivermouth site in Muan, Oksan-ri site of Hampyeong and Sanggap-ri site of Gochang are illustrated to interpret their sedimentary facies, radiocarbon datings, and palynofloral zonation. Up to the Middle to Late Last Glacial(up to 30-35Ka), old river-bed, flooding, and backswamp sequences contain such arboreal pollens as Pinus, Abies, and Picea, and rich in non-arboreal pollens like Cyperaceae, Gramineae, Ranunculaceae, and Compositae. During the LGM and post-LGM periods until Younger Dryas, vegetation has changes from the sub-alpine conifer forest(up to about 17-11Ka), through the conifer and broad-leaved deciduous forest, or mixed forest (formed during 16,680-13,010yrB.P), to the deciduous and broad-leaved forest (older than 9,500yrB.P). In the Earliest Holocene flooding deposits, fragments of plant roots are abundant and subjected to intensive pedogenic processes. During Holocene, three arboreal pollen zones are identified in the ascending order of strata; Pinus-Colyus zone(mixed conifer and deciduous broad-leaved forest, about up to 10Ka), Alnus-Quercus forest (the cool temperate deciduous broad-leaved forest, about 10Ka-2Ka), and Pinus forest (the conifer forest, about after 2Ka), as examplified in Soro-ri site of Cheonwon county. The palynological zonations of Soro-ri, Oksan-ri, Sanggap-ri, Youngsan estuary, and Gimhae fluvial plain have been recognized as a provisional correlation tool, and zonations based on fluvial backswamp and flooding deposits shows a similar result with those of previous researchers.
삼투질 농도와 Vasopression이 젖산생산에 미치는 영향
김창준,강석원,김영준,김원석,이근묵,남숙현 現代醫學社 1969 現代醫學 Vol.10 No.3
The present experiments were designed to examine in rabbit kidney cortex and inner medulla slices, the responses to the lactic acid production to osmotic gradiants as affected by vasopressin and by adenosine-triphosphate. The os molarity of medium was :altered by changing the concentration of NaCl in the Krebs-Ringer bicarbonate solution, and the NaCl was replaced with urea. The data demonstrate that 1) the lactic acid production in the medulla was two times in the cortex Media. In the cortex the lactic acid production was greatest in the media of 298mOsm/kg·H₂O, whereas it showed a periodic changes in the medulla as the osmolarity increased. 2) After addition of vasopressin, the lactic acid production was decreased in the media of 298mOsm/kg·H₂O but was increased in the media of 548mOsm/kg·H₂O. 3) The lactic acid production was not influenced by addition of ATP and interrelationship between vasopressin and ATP on the lactic acid production was obscure from this experiment.