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      • SCISCIESCOPUS

        Physicochemical Interactions between Rhamnolipids and <i>Pseudomonas aeruginosa</i> Biofilm Layers

        Kim, Lan Hee,Jung, Yongmoon,Yu, Hye-Weon,Chae, Kyu-Jung,Kim, In S. American Chemical Society 2015 Environmental science & technology Vol.49 No.6

        <P>This study investigated the physicochemical interactions between a rhamnolipid biosurfactant and a biofilm layer. A concentration of 300 μg mL<SUP>–1</SUP> of rhamnolipids, which is around the critical micelle concentration value (240 μg mL<SUP>–1</SUP>), showed great potential for reducing biofilm. The surface free energy between the rhamnolipids and biofilm layer decreased, as did the negative surface charge, due to the removal of negatively charged humic-like, protein-like, and fulvic acid-like substances. The carbohydrate and protein concentrations composed of extracellular polymeric substances decreased by 31.6% and 79.6%, respectively, at a rhamnolipid concentration of 300 μg mL<SUP>–1</SUP>. In particular, rhamnolipids can interact with proteins, leading to a reduction of the N source and amide groups on the membrane. For carbohydrates, the component ratio of glucosamine was decreased, but the levels of glucose and mannose that form the majority of the carbohydrates remained unchanged. To our knowledge, the present study is the first attempt at studying the interactions of the two phases of rhamnolipids and the biofilm layer, and as such is expected to clarify the mechanism by which rhamnolipids lead to a reduction in biofilm.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2015/esthag.2015.49.issue-6/es505803c/production/images/medium/es-2014-05803c_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es505803c'>ACS Electronic Supporting Info</A></P>

      • KCI등재

        Time-series comparison of COVID-19 case fatality rates across 21 countries with adjustment for multiple covariates

        Kim Yongmoon,Bryan Inho Kim,Tak Sangwoo 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.6

        Objectives: Although it is widely used as a measure for mortality, the case fatality rate (CFR) of coronavirus disease 2019 (COVID-19) can vary over time and fluctuate for many reasons other than viral characteristics. To compare the CFRs of different countries in equal measure, we estimated comparable CFRs after adjusting for multiple covariates and examined the main factors that contributed to variability in the CFRs among 21 countries.Methods: For statistical analysis, time-series cross-sectional data were collected from Our World in Data, CoVariants.org, and GISAID. Biweekly CFRs of COVID-19 were estimated by pooled generalized linear squares regression models for the panel data. Covariates included the predominant virus variant, reproduction rate, vaccination, national economic status, hospital beds, diabetes prevalence, and population share of individuals older than age 65. In total, 21 countries were eligible for analysis.Results: Adjustment for covariates reduced variation in the CFRs of COVID-19 across countries and over time. Regression results showed that the dominant spread of the Omicron variant, reproduction rate, and vaccination were associated with lower country-level CFRs, whereas age, the extreme poverty rate, and diabetes prevalence were associated with higher country-level CFRs.Conclusion: A direct comparison of crude CFRs among countries may be fallacious, especially in a cross-sectional analysis. Our study presents an adjusted comparison of CFRs over time for a more proper comparison. In addition, our findings suggest that comparing CFRs among different countries without considering their context, such as the epidemic phase, medical capacity, surveillance strategy, and socio-demographic traits, should be avoided.

      • Comparative compressional behavior of Zeolite-W with different extra-framework cations

        Hyeonsu Kim,Pyosang Kim,Donghoon Seoung,Yongmoon Lee 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

        Zeolite, one of microporous materials, has been widely studied for industrial application such as catalysts or adsorbent due to its size- and shape-selective property. Many experiments of zeolites have addressed the physio-chemical properties in ambient and non-ambient condition. High-pressure researches have been carried out in the last decades and shedded a new sights into phase stability and elastic behavior in response to adopting pressure and pressure-transmitting media (PTM). Zeolite-W is one of small pore zeolites and synthetic phase which has same framework with natural zeolite, Merlinoite (MER, (K,Na)5Ca,Ba)₂Al9Si23O64·23H₂O). We have prepared several extra-framework cation, EFC, analogues (K<SUP>+</SUP>: K-MER, Na<SUP>+</SUP>: Na-MER, Ag<SUP>+</SUP>: Ag-MER, NH₄<SUP>+</SUP>: NH₄-MER) of Zeolite-W by synthesis and cation-exchange method. Chemical composition of prepared samples was confirmed from Energy dispersive X-ray spectroscopy and Thermal Gravimetric Analysis. Compressional behavior of monovalent cation forms up to 5.22 GPa at room temperature is investigated by synchrotron X ray powder diffraction at 3D and 5A beamlines. We use a diamond-anvil cell as a pressurizing tool and water as PTM. In all cases, unit cell constants slightly increase in wet condition and then gradually decrease by pressure without phase transition. Calculated bulk modulus is 37(3) GPa, 38(4) GPa, 49(2) GPa, 47(3) GPa in order of Na-MER, Ag-MER, K-MER, NH4-MER, and it reveals that (in)compressibility is related to extra-framework cation size. Further understanding in atomic scale, Rietveld refinement is ongoing.

      • KCI등재

        다층지반에서 횡하중을 받는 군말뚝의 거동

        김용문(Kim Yongmoon),안광국(Ahn Kwangkuk) 한국지반환경공학회 2012 한국지반환경공학회논문집 Vol.13 No.3

        본 논문은 ABAQUS 유한 요소 프로그램을 사용하여 다층지반(화강풍화토-점토-화강풍화토)에서의 외말뚝과 군말뚝의 횡하중에 대한 영향을 설명한다. 본 연구에서의 변수는 캡이 없는 외말뚝과 캡이 있는 군말뚝으로, 파일의 직경은 0.5m, 길이는 10m인 말뚝을 사용하였다. 수치 해석은 말뚝의 간격을 (s=3D, 4D, 5D) 변화시켜 외말뚝과 군말뚝의 거동을 비교하기 위하여 수행되었다. 1×3군말뚝(leading pile, middle pile, trail pile)은 각각의 말뚝의 저항분포와 수평저항력을 조사하기 위하여 선정되었다. 점토의 해석모델은 Druker-Prager 구성관계를 이용하였고, 화강풍화토의 물성치는 기존의 논문을 사용하였으며, 말뚝은 탄성 원형 콘크리트로 모델링하였다. 해석 결과, 말뚝의 간격이 넓어짐에 따라 P-multiplier의 값이 leading pile의 영향을 덜 받는 것으로 나타났다. 또한, 단층지반이 다층지반에 비해 수평저항력이 약 4~20% 크게 작용하는 것으로 나타났다. This paper deals with the results for a numerical analysis of single piles and pile groups in multi-layers soil(granite soil-clay-granite soil) subjected to monotonous lateral loading using the ABAQUS finite element software. The investigated variables in this study include free head and embedded capped single pile, pile diameter (0.5m), pile length (10m), and pile groups. Numerical analyses were conducted by variation of spacing piles(s=3D, 4D, 5D) to compare the behaviour of single pile without cap and group pile. The 1×3 pile group(leading pile, middle pile, trail pile) was selected to investigate the individual pile and group lateral resistance, the distribution of the resistance among the piles. The analysis model of clay and the material of granite soil was modeled by using Druker-Prager constitutive relationship and existing treatise respectively. The pile was considered as a elastic circular concrete pile. As a result, the more pile space was extended, the value of P-multiplier is appeared to be less effective to leading pile. The lateral resistance of single-layer showed approximately 4-20% larger than the multi-layers.

      • KCI등재후보

        국내 스프링클러 설치기준과 소방관련 법에 관한 고찰

        김용문(YongMoon Kim),이영재(YoungJai Lee) 한국방재안전학회 2014 한국방재안전학회 논문집 Vol.7 No.2

        Recently, many accidents occur frequently because sprinklers aren’t installed or don’t work right when there are outbreak of fire in houses and aggregate buildings. Therefore, they can result in damage for humans and loss of property. Sprinklers are the most appropriate which can extinguish buildings' fire in the initial stages. Through lack of legal system, in domestic cases, sprinklers cannot operate their inherent performance. Domestic standard simply classifies installation objects according to types of business and forms of buildings, also divides into uses and floors of buildings. Especially it only regulates that sprinklers must be installed every floors in particular fire buildings that have more than eleven floors. While it doesn’t need to install sprinklers below ten floors, so we are threatened the safety. In this study, we derived causes and implications by analyzing concepts of sprinklers facilities, installation standards in domestic and foreign legal system, and recent cases that expanded damages in fire accidents because of weak point of installation and control standards. In domestic cases, as a result, government has to provide an institutional strategy and law that regulate duty to install sprinklers to all aggregate buildings regardless of floors in terms of new buildings. Also, if someone who has existing buildings wanted to install them, government would guarantee subsidy to encourage installation. In addition, government supervises fire-fighting activities when there are fire by compensating standards about regular inspection by a qualified technician, operation and maintenance of sprinklers as well as reinforcement of administrative criteria. 최근 들어 주택 및 집합건물에서 화재가 발생할 경우 스프링클러가 설치되어 있지 않거나, 설치되어 있어도 제대로 작동하지 않아서 많은 인명과 재산상의 손실을 초래하는 경우를 자주 목격하게 된다. 건축물 화재가 발생하면 초기에 진압 하는 소화설비로써 가장 적합한 것은 스프링클러라 여겨진다. 하지만 국내의 경우 법체계의 미비로 인해 스프링클러 설비가 가진 본연의 성능을 발휘하지 못하고 있다. 우리나라 기준은 스프링클러 설비의 설치 대상을 업종과 건축물 형태에 따라 단 순하게 분류하며, 건물의 용도나 건축물의 층수로 구분하고 있는 실정이다. 특히 층수가 11층 이상인 특정소방대상물에만 모든 층에 스프링클러를 설치하게 되어 있을 뿐, 법적으로 10층 이하의 건물에는 스프링클러를 설치하지 않아도 되는 안전의 사각지대에 놓여 있다. 본 연구에서는 스프링클러 설비에 관한 개념, 국내외 법체계상에서 규정하는 스프링클러의 설치 기준, 그리고 근래에 발생한 화재사고에서 스프링클러 설치 및 관리기준의 허점으로 인해 피해를 키운 사례를 분석하여 그 원인과 시사점을 도출하였다. 결과적으로 국내의 경우 신축 건물에 대해서 층수에 관계없이 모든 집합건물은 스프링클러를 의무적으로 설치하게 하는 법 및 제도적 장치를 마련해야 한다. 또한 기존의 건축물 중에 스프링클러가 설치되어 있지 않은 건 물의 경우에는 신규로 스프링클러를 설치하고자 하면, 정부 보조금을 지급하여 스프링클러 설치를 장려하는 정책적 시행도 요구된 다. 더욱이 스프링클러의 설치적 기준의 강화뿐만 아니라 전문기술자격자에 의한 수시, 정기점검을 강화하는 등 스프링클러의 운용 및 유지에 대한 관리적 기준도 보완하여 화재 발생 시 소방 활동이 제대로 이루어지도록 해야 한다.

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