• 제목/요약/키워드: dispersed generation

검색결과 136건 처리시간 0.027초

Clay-based Management for Removal of Harmful Red Tides in Korea: A Multi-perspective Approach

  • Choi, Moon-Hee;Lee, Soon Chang;Oh, You-Kwan;Lee, Hyun Uk;Lee, Young-Chul
    • 한국해양바이오학회지
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    • 제6권1호
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    • pp.17-25
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    • 2014
  • Periodically, harmful algal blooms (HABs) have occurred, with impacts on various areas including public health, tourism, and aquatic ecosystems, especially aquacultured and caged fisheries. To prevent or manage invasions of HABs into fish farms on an emergency basis, many methods have been proposed. Frequently over the past 30 years in coastal countries, treatments of clay and clay mixed with polyaluminum chloride (PAC) and chitosan have been tested for HAB-removal effectiveness in both the laboratory and the field. In Korea, yellow loess clay (hwangto) has been dispersed using electrolytic clay dispensers, both to decrease the amount of yellow loess clay's usage in containers and enhance HAB-removal efficiency. However, this emergency method has limitations, among which is the requirement for more effective controlling agents for field applications. Thus, in this paper, we review technologies for clay-based red tides prevention and control and their limitations, and, further, introduce next-generation algicidal technologies for the emergency protection of fish farms.

Genetic diversity assessment of Aconitum coreanum (H. Lév.) Rapaics (Ranunculaceae), an endangered plant species in Korea, using microsatellite markers

  • Won, Hyosig;Yun, Young-Eun;Kwak, Myounghai;Han, Jeong Eun
    • Journal of Species Research
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    • 제1권2호
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    • pp.224-231
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    • 2012
  • To assess the genetic diversity of Aconitum coreanum (Ranunculaceae) populations in Korea, we have amplified and sequenced eight organellar marker regions, and developed and analyzed microsatellite markers. No sequence variation was detected from the eight organellar markers. Ten microsatellites were developed using Next Generation Sequencing and two microsatellite markers, AK_CA03 and AK_CT07, were identified polymorphic and applied for 143 individuals of twelve A. coreanum populations. Four and five alleles were detected for the two microsatellite loci, respectively, and number of migrants ($N_m$) was estimated as 1.12586. Two microsatellite marker loci showed $F_{ST}$ of 0.205 and 0.275, respectively. The heterozygosity deficit, low level of among-population differentiation, small size of gene flow, and lack of sequence variation of the organellar markers suggest that A. coreanum is reproductively isolated from other Aconitum species and there has been continuous gene flow among the populations of A. coreanum or it has dispersed relatively recently after speciation. Though population pairwise $F_{ST}$'s presented significant geographic structure, further sampling and study will be necessary to confirm this.

Valve actuation effects on discrete monopropellant slug delivery in a micro-scale fuel injection system

  • McDevitt, M. Ryan;Hitt, Darren L.
    • Advances in aircraft and spacecraft science
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    • 제1권4호
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    • pp.409-425
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    • 2014
  • Converging flows of a gas and a liquid at a microchannel cross junction, under proper conditions, can result in the formation of periodic, dispersed microslugs. This microslug formation phenomenon has been proposed as the basis for a fuel injection system in a novel, 'discrete' monopropellant microthruster designed for use in next-generation miniaturized satellites. Previous experimental studies demonstrated the ability to generate fuel slugs with characteristics commensurate with the intended application during steady-state operation. In this work, numerical and experimental techniques are used to study the effect of valve actuation on slug characteristics, and the results are used to compare with equivalent steady-state slugs. Computational simulations of a valve with a 1 ms valve-actuation cycle show that as the ratio of the response time of the valve to the fully open time is increased, transient effects can increase slug length by up to 17%. The simulations also demonstrate that the effect of the valve is largely independent of surface tension coefficient, which is the thermophysical parameter most responsible for slug formation characteristics. Flow visualization experiments performed using a miniature valve with a 20 ms response time showed less than a 1% change in the length of slugs formed during the actuation cycle. The results of this study indicate that impulse bit and thrust calculations can discount transient effects for slower valves, but as valve technology improves transient effects may become more significant.

Effect of viscosity ratio and AN content on the compatibilization of PC-SAN blends during ultrasound-assisted melt mixing

  • Kim, Hyung-Su;Yang, Hyun-Suk;Lee, Jae-Wook
    • Korea-Australia Rheology Journal
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    • 제17권4호
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    • pp.165-170
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    • 2005
  • In this study, high intensity ultrasound was employed to induce mechano-chemical degradation during melt mixing of polycarbonate (PC) and a series of styrene-acrylonitrile (SAN) copolymers. It was confirmed that generation of macroradicals of constituent polymers can lead to in-situ copolymer formation by their mutual combination, which should be an efficient path to compatibilize immiscible polymer blends and stabilize their phase morphology in the absence of other chemical agents. Based on the effectiveness of the compatibilization by ultrasound assisted mixing process, we investigated the effects of viscosity ratio of PC and SAN and AN content in SAN on the compatibilization of PC/SAN blends. It was found that effectiveness of compatibilization is optimal when the AN content is in the range of favorable interaction with PC and the viscosity of the matrix is higher than that of the dispersed phase. In addition, changes in the interfacial tension between PC and SAN were assessed by examining relaxation spectra which were obtained from measuring rheological properties of ultrasonically treated blends.

Development and Characterization of 14 Microsatellite Markers for the Antarctic Midge Parochlus steinenii (Diptera, Chironomidae) in Maritime Antarctic

  • Kim, Hanna;Kang, Seunghyun;Kim, Hanul;Kim, Sanghee;Jung, Jongwoo
    • Animal Systematics, Evolution and Diversity
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    • 제33권2호
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    • pp.140-143
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    • 2017
  • A winged midge species, Parochlus steinenii is one of the most abundant species in Antarctica, which is distributed over a wide area from the South American continent to the South Shetland Islands in Antarctica. It was dispersed into islands in the South Shetland Islands from the South American continent, and it adapted to a variety of environments and settled. This species, therefore, is a good model organism to explain the evolutionary process of Antarctic terrestrial fauna. Nevertheless, there are few genetic studies on this species, which are necessary for understanding the genetic diversity, population structure, etc. Here, we developed and characterized 14 polymorphic microsatellite markers. The number of alleles per locus ranged from 2 to 5. The observed and expected heterozygosities were in the range of 0.024 to 0.561 and 0.024 to 0.535, respectively. Identifying genetic differences between populations, they are suitable markers for researches investigating genetic diversity and population structure of P. steinenii, which provide us with clues to dispersion, evolution and ecology of this species.

The effect of cooling rates on carbide precipitate and microstructure of 9CR-1MO oxide dispersion strengthened(ODS) steel

  • Jang, Ki-Nam;Kim, Tae-Kyu;Kim, Kyu-Tae
    • Nuclear Engineering and Technology
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    • 제51권1호
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    • pp.249-256
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    • 2019
  • The 9Cr-1Mo ferritic-martensitic ODS steel is a promising structural material for the next generation nuclear power plants including fast reactors for application in reactor vessels and nuclear fuel. The ODS steel was cooled down by furnace cooling, air cooling, oil quenching and water quenching, respectively, after normalizing it at $1150^{\circ}C$ for 1 h and then tempering at $780^{\circ}C$ for 1 h. It is found that grain size, a relative portion of ferrite and martensite, martensitic lath configuration, behaviors of carbide precipitates, and hardness of the ODS steel are strongly dependent on a cooling rate. The grain size and martensitic lath width become smaller with the increase in a cooling rate. The carbides were precipitated at the grain boundaries formed between the ferrite and martensite phases and at the martensitic lath interfaces. In addition, the carbide precipitates become smaller and more widely dispersed with the increase in a cooling rate, resulting in that the faster cooling rate generated the higher hardness of the ODS steel.

태양광전원이 연계된 고압배전선로의 보호협조 평가 방안에 관한 연구 (Evaluation Method for Protection Coordination of PV Systems Interconnected with Primary Feeders)

  • 김병기;김소희;유경상;노대석
    • 한국융합학회논문지
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    • 제2권4호
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    • pp.29-37
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    • 2011
  • 종래의 배전계통에 있어서의 전력조류는 변전소에서 선로말단을 향한 단 방향이었지만, 신에너지전원(분산전원)이 연계된 배전계통의 경우에는 그 출력용량의 여부에 따라 양방향의 전력조류가 발생할 가능성이 있어, 계통운용상 여러 가지의 문제점이 야기될 수 있다. 분산전원은 대규모전원의 보완적 역할과 배전선로 상의 국부적 부하 감당 역할을 부과하여 그의 적극적 활용을 꾀하기 위해서는, 분산전원으로부터 배전계통에 전력을 공급하는 역 조류의 기능을 허용할 수 있는 양방향 보호협조방식의 체제를 확립할 필요가 있다. 따라서 본 연구에서는 분산전원 연계에 따른 보호협조 기본 방안과 부하절체 운전에 따른 보호협조 방안, 변압기결선에 따른 보호협조 방안 등에 대한 알고리즘을 제시하였다. 또한, 이론적인 계산법(대칭좌표법)과 MATLAB/SIMULINK에 의하여 실 계통에서의 양방향 보호협조에 관련된 문제점을 분석하고, 해결방안을 제시하였다.

Non-gaseous Plasma Immersion Ion Implantation and Its Applications

  • Han, Seung-Hee;Kim, En-Kyeom;Park, Won-Woong;Moon, Sun-Woo;Kim, Kyung-Hun;Kim, Sung-Min
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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    • pp.151-151
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    • 2012
  • A new plasma process, i.e., the combination of PIII&D and HIPIMS, was developed to implant non-gaseous ions into materials surface. HIPIMS is a special mode of operation of pulsed-DC magnetron sputtering, in which high pulsed DC power exceeding ~1 kW/$cm^2$ of its peak power density is applied to the magnetron sputtering target while the average power density remains manageable to the cooling capacity of the equipment by using a very small duty ratio of operation. Due to the high peak power density applied to the sputtering target, a large fraction of sputtered atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed plasma of sputtered target material by HIPIMS operation, the implantation of non-gaseous ions can be successfully accomplished. The new process has great advantage that thin film deposition and non-gaseous ion implantation along with in-situ film modification can be achieved in a single plasma chamber. Even broader application areas of PIII&D technology are believed to be envisaged by this newly developed process. In one application of non-gaseous plasma immersion ion implantation, Ge ions were implanted into SiO2 thin film at 60 keV to form Ge quantum dots embedded in SiO2 dielectric material. The crystalline Ge quantum dots were shown to be 5~10 nm in size and well dispersed in SiO2 matrix. In another application, Ag ions were implanted into SS-304 substrate to endow the anti-microbial property of the surface. Yet another bio-application was Mg ion implantation into Ti to improve its osteointegration property for bone implants. Catalyst is another promising application field of nongaseous plasma immersion ion implantation because ion implantation results in atomically dispersed catalytic agents with high surface to volume ratio. Pt ions were implanted into the surface of Al2O3 catalytic supporter and its H2 generation property was measured for DME reforming catalyst. In this talk, a newly developed, non-gaseous plasma immersion ion implantation technique and its applications would be shown and discussed.

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해쇄 및 침강분리에 의한 저품위 견운모의 품위향상 특성 (Beneficiation of Low Grade Sericite Using Attrition Scrubbing and Sedimentation)

  • 채성기;김현수;김상배;김완태
    • 한국광물학회지
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    • 제30권4호
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    • pp.137-147
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    • 2017
  • 본 연구에서는 저품위 견운모를 대상으로 파쇄, 해쇄 및 침강분리 공정을 적용하여 각각의 단위공정의 특성과 품위향상에 미치는 영향에 대해 고찰하였다. 원광석의 주 구성광물은 견운모, 석영, 방해석이었으며, 체가름 결과, 입자의 크기가 작아질수록 견운모의 함량은 높아지는 반면, 불순광물의 함량은 상대적으로 감소하는 경향을 보였다. 조암광물의 형상 및 원소분석 결과, 메디아를 이용하는 분쇄 방식보다는 입자의 표면에 선택적으로 충격력과 전단력을 가해줄 수 있는 해쇄 방식이 적절한 것으로 판단되었다. 해쇄 시간 및 슬러리 농도가 증가함에 따라 미립자 발생량이 증가하였으며, 장시간 해쇄한 경우 미립자 내 불순광물인 석영과 방해석의 혼입량이 증가하는 결과를 보였다. 해쇄 없이 단순하게 분산한 슬러리를 20분 동안 정치 후 회수한 정광의 생산율은 15.4 wt%, $K_2O$ 함량은 9.84 wt% 였다. 10분 해쇄한 후 40분 침강 분리하여 회수한 정광의 생산율은 23.4 wt%로 증가한 반면 $K_2O$ 함량은 9.71 wt%로 감소하였다. 회수된 최종산물은 대부분 판상의 입자로 관찰되었으며 입자표면의 원소분석 결과, 주 구성 원소는 Si, Al, K로 견운모의 화학조성을 보였다.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • 황창묵;박종완
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2010년도 제39회 하계학술대회 초록집
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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