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      • Aerosol concentrations and composition in the North Pacific marine boundary layer

        Choi, Yongjoo,Rhee, Tae Siek,Collett Jr., Jeffrey L.,Park Jr., Taehyun,Park Jr., Seung-Myung,Seo Jr., Beom-Keun,Park Jr., Gyutae,Park Jr., Keyhong,Lee Jr., Taehyoung Elsevier 2017 Atmospheric environment Vol.171 No.-

        <P>Ship-borne measurements of inorganic and organic aerosols, including methanesulfonic acid (MSA), were conducted over the Northern Pacific using a High Resolution Time of Flight Aerosol Mass Spectrometer (AMS). This study, conducted aboard the Korean ice breaker R/V Araon, was part of the SHIP borne Pole-to-Pole Observations (SHIPPO) project. Based on air mass source region, the cruise track could be divided into five sections. Overall, the South Asia and Northern Japan ship transects showed higher aerosol concentrations due to continental pollution and biomass burning sources, respectively. In all five regions, the average mass concentrations of sulfate and organic aerosols (OA) were much higher than concentrations of nitrate and ammonium. Positive matrix factorization (PMF) analysis distinguished two organic aerosol factors as hydrocarbon-like and oxidized OA (HOA and OOA). HOA peaked in South Asia under the influence of anthropogenic pollution source areas, such as China and Korea, and generally decreased with increasing latitude across the full study region. OOA concentrations peaked in Northern Japan near the Tsugaru Strait and appear to reflect fine particle contributions from biomass burning. The mean HOA concentration in the clean marine area (Aleutian Island to Siberia) was 0.06 mu g/m(3) and comprised approximately 8% of the OA mass fraction. The highest MSA concentrations peaked in the Aleutian Islands at nearly 15 mu g/m(3), suggesting influence from higher dimethyl sulfide (DMS) emissions resulting from biological nutrient uptake during summer. The MSA/sulfate ratio, an indicator of the relative fine particle contributions of DMS and anthropogenic sources, revealed a sharp gradient as the ship approached the clean marine areas where the dominance of DMS increased. The patterns in OOA, HOA, and MSA concentrations found in this study provide a better understanding of the characteristics of inorganic and organic aerosols in the Northern Pacific Ocean. (C) 2017 Elsevier Ltd. All rights reserved.</P>

      • Controlling optical properties of metallic multi-shell nanoparticles through suppressed surface plasmon resonance

        Acapulco Jr., Jesus A.I.,Hong Jr., Soonchang,Kim Jr., Seong Kyu,Park Jr., Sungho Elsevier 2016 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.461 No.-

        <P><B>Abstract</B></P> <P>Herein, we report the surface plasmon resonance of plasmonic multi-shell nanoparticles compared to bimetallic Ag/Au hollow nanospheres of similar final size, shape, and percent composition. The surface plasmon resonance of solid and hollow nanoparticles exhibited a quadrupole mode that was particularly prominent around the 100nm size regime, while multi-shell nanoparticles did not show a quadrupole mode at a similar size. In the latter case, the quadrupole mode of the outermost nanoshell was suppressed by the dipole modes of the inner shells, and the suppression of the quadrupole mode was not affected by the shape of the inner nanostructures. Light interaction of the multi-shell nanoparticle was investigated through simulated electromagnetic field distribution obtained by finite-difference time domain (FDTD) calculations which were in a good agreement with the results of surface-enhanced Raman spectroscopy (SERS).</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

      • SCISCIESCOPUS

        Irradiation-induced disordering and amorphization of Al<sub>3</sub>Ti-based intermetallic compounds

        Park, Jeong-Yong,Kim, Il-Hyun,Motta, Arthur T.,Ulmer, Christopher J.,Kirk Jr., Marquis A.,Ryan Jr., Edward A.,Baldo Jr., Peter M. Elsevier 2015 JOURNAL OF NUCLEAR MATERIALS Vol.467 No.2

        <P><B>Abstract</B></P> <P>An in situ ion-irradiation study, simultaneously examined using transmission electron microscopy, was performed to investigate irradiation-induced disordering and amorphization of Al<SUB>3</SUB>Ti-based intermetallic compounds. Thin foil samples of two crystalline structures: D0<SUB>22</SUB>-structured Al<SUB>3</SUB>Ti and L1<SUB>2</SUB>-structured (Al,Cr)<SUB>3</SUB>Ti were irradiated using 1.0 MeV Kr ions at a temperature range from 40 K to 573 K to doses up to 4.06 × 10<SUP>15</SUP> ions/cm<SUP>2</SUP>. The results showed that both the compounds underwent an order-disorder transformation under irradiation, where both Al<SUB>3</SUB>Ti and (Al,Cr)<SUB>3</SUB>Ti ordered structures were fully transformed to the disordered face-centered cubic (FCC) structure except at the highest irradiation temperature of 573 K. A slightly higher irradiation dose was required for order-disorder transformation in case of Al<SUB>3</SUB>Ti as compared to (Al,Cr)<SUB>3</SUB>Ti at a given temperature. However, their amorphization resistances were different: while the disordered FCC (Al,Cr)<SUB>3</SUB>Ti amorphized at the irradiation dose of 6.25 × 10<SUP>14</SUP> ions/cm<SUP>2</SUP> (0.92 dpa) at 40 K and 100 K, the Al<SUB>3</SUB>Ti compound with the same disordered FCC structure maintained crystallinity up to 4.06 × 10<SUP>15</SUP> ions/cm<SUP>2</SUP> (5.62 dpa) at 40 K. The critical temperature for amorphization of (Al,Cr)<SUB>3</SUB>Ti under Kr ion irradiation is likely between 100 K and room temperature and the critical temperature for disordering between room temperature and 573 K.</P>

      • SCIESCOPUSKCI등재
      • SCISCIESCOPUS

        2D/3D electron temperature fluctuations near explosive MHD instabilities accompanied by minor and major disruptions

        Choi, M.J.,Park, H.K.,Yun, G.S.,Lee, W.,Luhmann Jr., N.C.,Lee, K.D.,Ko, W.-H.,Park, Y.-S.,Park, B.H.,In, Y. IOP 2016 Nuclear fusion Vol.56 No.6

        <P>Minor and major disruptions by explosive MHD instabilities were observed with the novel quasi 3D electron cyclotron emission imaging (ECEI) system in the KSTAR plasma. The fine electron temperature (<I>T</I> <SUB>e</SUB>) fluctuation images revealed two types of minor disruptions: a small minor disruption is a <img ALIGN='MIDDLE' ALT='$q\sim 2$ ' SRC='http://ej.iop.org/images/0029-5515/56/6/066013/nfaa223aieqn001.gif'/> localized fast transport event due to a single <I>m</I>/<I>n</I>  =  2/1 magnetic island growth, while a large minor disruption is partial collapse of the <img ALIGN='MIDDLE' ALT='$q\leqslant 2$ ' SRC='http://ej.iop.org/images/0029-5515/56/6/066013/nfaa223aieqn002.gif'/> region with two successive fast heat transport events by the correlated <I>m</I>/<I>n</I>  =  2/1 and <I>m</I>/<I>n</I>  =  1/1 instabilities. The <I>m</I>/<I>n</I>  =  2/1 magnetic island growth during the minor disruption is normally limited below the saturation width. However, as the additional interchange-like perturbation grows near the inner separatrix of the 2/1 island, the 2/1 island can expand beyond the limit through coupling with the cold bubble formed by the interchange-like perturbation.</P>

      • A role of low dose chemical mixtures in adipose tissue in carcinogenesis

        Lee, Duk-Hee,Jacobs Jr, David R.,Park Jr, Ho Yong,Carpenter Jr, David O. Elsevier 2017 Environment international Vol.108 No.-

        <P><B>Abstract</B></P> <P>The Halifax project recently hypothesized a composite carcinogenic potential of the mixture of low dose chemicals which are commonly encountered environmentally, yet which are not classified as human carcinogens. A long neglected but important fact is that adipose tissue is an important exposure source for chemical mixtures. In fact, findings from human studies based on several persistent organic pollutants in general populations with only background exposure should be interpreted from the viewpoint of chemical mixtures because serum concentrations of these chemicals can be seen as surrogates for chemical mixtures in adipose tissue. Furthermore, in conditions such as obesity with dysfunctional adipocytes or weight loss in which lipolysis is increased, the amount of the chemical mixture released from adipose tissue to circulation is increased. Thus, both obesity and weight loss can enhance the chance of chemical mixtures reaching critical organs, however paradoxical this idea may be when fat mass is the only factor considered. The complicated, interrelated dynamics of adipocytes and chemical mixtures can explain puzzling findings related to body weight among cancer patients, including the obesity paradox. The contamination of fat in human diet with chemical mixtures, occurring for reasons similar to contamination of human adipose tissue, may be a missing factor which affects the association between dietary fat intake and cancer. The presence of chemical mixtures in adipose tissue should be considered in future cancer research, including clinical trials on weight management among cancer survivors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Halifax project hypothesized a carcinogenic potential of chemical mixtures. </LI> <LI> Human adipose tissue is an important internal exposure source for chemical mixtures. </LI> <LI> Obesity with dysfunctional adipocytes can release chemical mixtures to circulation. </LI> <LI> Paradoxically, weight loss can also release chemical mixtures to circulation. </LI> <LI> Interrelated dynamics of adipocytes and chemicals can explain obesity paradox. </LI> </UL> </P>

      • Multiscale interaction between a large scale magnetic island and small scale turbulence

        Choi, M.J.,Kim, J.,Kwon, J.-M.,Park, H.K.,In, Y.,Lee, W.,Lee, K.D.,Yun, G.S.,Lee, J.,Kim, M.,Ko, W.-H.,Lee, J.H.,Park, Y.S.,Na, Y.-S.,Luhmann Jr, N.C.,Park, B.H. IOP 2017 Nuclear fusion. Fusion nucléaire. &n.Illiga Vol.57 No.12

        <P>Multiscale interaction between the magnetic island and turbulence has been demonstrated through simultaneous two-dimensional measurements of turbulence and temperature and flow profiles. The magnetic island and turbulence can mutually interact via coupling between the electron temperature (<I>T</I> <SUB> <I>e</I> </SUB>) gradient, the <I>T</I> <SUB> <I>e</I> </SUB> turbulence, and the poloidal flow. The <I>T</I> <SUB> <I>e</I> </SUB> gradient altered by the magnetic island steepens outside and flattens inside the island. The <I>T</I> <SUB> <I>e</I> </SUB> turbulence can appear in increased <I>T</I> <SUB> <I>e</I> </SUB> gradient regions. The combined effects of the <I>T</I> <SUB> <I>e</I> </SUB> gradient and the poloidal flow shear determines the two-dimensional distribution of the <I>T</I> <SUB> <I>e</I> </SUB> turbulence. When the poloidal vortex flow forms, it can maintain the steepest <I>T</I> <SUB> <I>e</I> </SUB> gradient and the magnetic island acts more like an electron heat transport barrier. Interestingly, when the <I>T</I> <SUB> <I>e</I> </SUB> gradient, the <I>T</I> <SUB> <I>e</I> </SUB> turbulence, and the vortex flow shear increase beyond critical levels, the magnetic island turns into a fast electron heat transport channel, which directly leads to the minor disruption.</P>

      • SCISCIESCOPUSKCI등재

        On the Mechanism of the Formation of Widmanstatten Graphite in Flake Graphite Cast Irons

        Jr Carl R.Loper,Park, Junyoung 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.4

        The mechanism whereby Widmanstatten graphite develops during the solidification of flake graphite cast irons has been found to involve the preferential segregation and a complex interaction of specific elements at the surface of the graphite flake during solidification and the development of the plate like appendages in the solid austenite adjacent to the graphite flake. The literature has suggested that lead, calcium and hydrogen may bc causal to the formation of Widmanstatten graphite. hut has the interaction of these elements has not been effectively documented. While the formation of this degraded graphite is often attributed to the presence of a sufficient amount of lead alone, it has been observed that Widmansatten graphite develops only in conjunction with a combination of factors operative at the graphite-austenite intertace. Commercial flake graphite cast irons may exhibit Widmanstatten graphite as a function of lead and calcium content in the iron, moisture content in the molding media, solidification cooling rate and the rate of cooling immediately after solidification, etc. Lead contamination of cast irons was also observed to increase the chilling tendency of the iron. The detrimental effects of lead can be counteracted by the presence of rare earths in the iron, where rare eanh elements react with lead to form stable. high melting point compounds.

      • KCI등재

        자연유산 환자 수태물의 세포유전학적 연구

        박제응,강정배,김홍배,김중석,김종렬,정태범,진현주,오숙경,이근영,강성원 대한산부인과학회 1999 Obstetrics & Gynecology Science Vol.42 No.7

        목적: 자연유산의 가장 흔한 원인은 수태물의 염색체 이상으로 알려져 왔다. 따라서 환자들의 상담 및 치료에 유용한 정보를 얻기위해 염색체 이상의 빈도 및 종류를 조사하였다. 연구 방법: 1994년 1월부터 1997년 12월 까지 한림대학교 강남성심병원 산부인과를 내원한 자연유산 환자에서 유산조직을 얻을 수 있었던 74례 중에서 염색체 이상을 보인 28례의 환자와 남편의 정맥혈을 이용하여 세포유전학적 검사를 시행하였다. 결과: 핵형 분석에 성공한 70례 중에서 염색체 이상의 빈도는 40.0%[28/70]였고, 염색체 이상이 있는 28례 중에서 상염색체 삼체성[autosomal trisomy]이 12례[42.7%]를 가장 많았으며, 단일염색체[monosomy] X가 6례[21.4%], 다배수성[polyploidy]이 3례[10.7%], 구조적 이상이 7례[25.0%]의 빈도를 보였으며, 유산아의 임신주수 기간에따른 이상군의 비율이 임신초기일수록 높았다. 상염색체 삼염색체중 21번이 33.0%로 가장 높은 빈도를 보였고, 18번이 25.0%, 16번이 17.0%였다. 모성나이에 따른 염색체 이상의 빈도는 큰 차이를 보이지 않았으나 상염색체 삼체성의 빈도는 모성의 나이가 많아짐에 따라 다소 증가하였다. 염색체의 구조적이상을 보인 7례 중에서 5례에서 역위를 보였고 2례에서 전좌를 보였다. 구조적이상은 양친에게 유전되는 경우보다 de novo 형태로 오는 경우가 71%[5/7례]이었으나, 전좌를 보이는 2례 모두는 Robertsonian 전좌로 양쪽 부모 중 하나가 염색체 이상을 갖는 보인자로 나타났다. 결론: 이상과 같은 결과로 자연유산 환자에서 유전상담 및 산전 염색체 검사가 필수적임을 재확인 할 수 있었다. Objective: Chromosomal abnormalities of abortuses have also been used to investigate the most common etiology of spontaneous abortion, but the frequency and the types of spontaneous abortions have also demonstrated considerable variation among in different countries and races. Methods: So as to studies of the frequency and type of chromosomal abnormalities of abortuses , a cytogenetic study of 74 abortuses and their aborters was performed from January, 1994 to December, 1997 in Hallym University Kangnam Sacred Heart Hospital. Results: The frequency of abnormal karyotypes in abortuses was 40.0%[28/70 cases], of autosomal trisomy 42.7% [12/28 cases], of monosomy X 21.4%[6/28 cases], of polyploidy 10.7%[3/28 cases] and of structural anomalies 25.0%[7/28 cases]. The earlier gestational age when the loss occurs, got the higher the likelihood to be chromosomally abnormal. Among trisomies, chromosomes 21[33%], 18[25%] and 16[17%] were prevalent. There was no statistical significance of the frequency of chromosomal abnormality according to maternal age, but trisomy was slightly increased at older age. Structural abnormalities were present in 7 cases; 2 cases were Robertsonian translocation and 5 cases were inversion. The origin of structural abnormalities were classified as De novo in 5 patients, and familial tendency in two. One of the parents of two translocation cases was carriers with abnormal karyotype. Two parents of translocation cases were carriers with abnormal karyotypes. Conclusion: Our findings support that cytogenetic study is worth-while in couples presenting with a history of spontaneous abortion or older age.

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