• Title/Summary/Keyword: Dispersed flow

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The Analysis of Growth Environment on Corylopsis coreana Community in Hallyeohaesang National Park (한려해상국립공원 히어리군락의 생육환경 분석)

  • Shin, Seoung-Ho;Kim, Jong-Sub;Kim, Jong-Myung;Seo, Dong-Jin;Kang, Hee-Gon;Kim, Min-Kyu;Jo, Gye-Jung;Goo, Chur-Hyun;Park, Eun-Hee
    • Journal of agriculture & life science
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    • v.45 no.5
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    • pp.49-56
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    • 2011
  • This study was conducted to provide data for the maintenance of the Corylopsis coreana community within the Hallyeohaesang National Park. Survey site of Corylopsis coreana community was located at a valley, which composed of over 60% exposed rock. As this result, much of the species was damaged or washed away due to the water flow from rainfall. The tree layers dominant species were Quercus serrata and Pinus densiflora. while the subtree layers dominant species were Corylopsis coreana, Acer pseudosieboldianum, Sapium japonicum, Chamaecyparis obtusa and Cornus kousa etc. The shrub layers dominant species were Callicarpa japonica and Smilax china etc., and herbaceous layers dominant species were Disporum smilacinum etc. Increased precipitation and rainfall days were observed from May to September in this valley during 2008~2010, which likely increased soil erosion and damage. Because water flow pattern was dispersed the Corylopsis coreana seed and the soil floor was shallow, and population of Corylopsis coreana seedlings were diminished.

Measurement of Terminal Velocity for Scatter Prevention of Powder in the Voloxidizer for Oxidation of UO$_{2}$ Pellet (UO$_{2}$ 펠릿 산화로의 분말 비산 방지를 위한 최종속도 측정)

  • Kim Young-Hwan;Yoon Ji-Sup;Jung Jae-Hoo;Jin Jae-Hyun;Hong Dong-Hee
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.3 no.2
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    • pp.77-84
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    • 2005
  • A voloxidizer for a hot cell demonstration, that handles spent fuels of a high radiation level in a limited space should be small and spent fuel powders should not be dispersed out of the equipment involved. In this study a density rate equation as well as the Stokes'equation has been proposed in order to obtain the theoretical terminal velocity of powders. The terminal velocity of U$_{3}$O$_{8}$ has been predicted by using the terminal velocity of SiO$_{2}$, and then determination has been the optimum air flow rate which is able to prevent powders from scattering. An equation which has shown a relationship between theoretical terminal velocities of U$_{3}$O$_{8}$ and SiO$_{2}$ has been derived with the help of the Stokes'equation, and then an experimental verification made for the theoretical Stokes' equation of SiO$_{2}$ by means of an experimental device made of acryl. The theoretical terminal velocity based on the proposed density rate equation has been verified by detecting U$_{3}$O$_{8}$ powders in a filter installed in the mock-up voloxidizer. As the results, the optimum air flow rates seem to be 20 LPM by the Stokes'equation while they are 14.5 L/min by the density rate equation. At the experiments with the mock-up voloxidizer, a trace amount of U$_{3}$O$_{8}$ seems to be detectable at the air flow rate of 14.5 L/min by the density rate equation, but U$_{3}$O$_{8}$ powders of 7$\mu$m diameter seem detectable at the air flow rate of 20 L/min by the Stokes'equation. It is revealed that 14.5 L/min is the optimum air flowe rate which is capable of preventing U$_{3}$O$_{8}$ powders from scattering in the UO$_{2}$ voloxidizer and the proposed density rate equation is proper to calculate the terminal velocity of U$_{3}$O$_{8}$ powders.

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A Study on Chemical Compositions of Sediment and Surface Water in Nakdong River for Tracing Contaminants from Mining Activities (광해오염원 추적을 위한 낙동강 지역 퇴적물 및 하천수의 화학조성 연구)

  • Kim, Jiyun;Choi, Uikyu;Baek, Seung-Han;Choi, Hye-Bin;Lee, Jeonghoon
    • Journal of the Korean earth science society
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    • v.37 no.4
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    • pp.211-217
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    • 2016
  • There have been found mine tailings, wastes, and mining drainage scattered in the area of Nakdong River due to the improper maintenance of the abandoned mines. These contaminants can flow into rivers during the heavy rain periods in summer. Along the study area beginning Seokpo-myeon, Bonghwa-gun of Gyeongsangbuk-do untill Dosan-myeon, Andong-si, there are one hundred five mines including sixty metalliferous mines and forty-five nonmetal mines, which can adversely affect the adjacent rivers. To verify the contamination, we collected sediments, seepage water and surface water for a year both in rainy season and dry season. This study found that sediments, containing high concentrations of heavy metals caused by mining activities, are dispersed throughout the entire river basin (68 sample points with pollution index, based on the concentration of trace element, (PI) >10 among the total of 101 samples). The results of river water analysis indicated the increased concentrations of arsenic and cadmium at branches from Seungbu, Sambo, Okbang and Janggun mine, which concerns that the river water may be contaminated by mining drainage and tailing sediments. However, it is difficult to sort out the exact sources of contamination in sediments and waters only by using the chemical compositions. Thus the control of mining pollution is challenging. To prevent water from being contaminated by mining activities, we should be able to divide inflow rates from each origin of the mines. Therefore, there should be a continued study about how to trace the source of contaminants from mining activities by analyzing stable isotopes.

Liquid-Liquid Dispersion of an Immiscible Liquid Phase (n-Hexane/Water) System in a Stirred Tank (교반조에서 비혼화성 액상(n-헥산/물)계의 액-액분산)

  • Kim, Tae-Ok;Kim, Dong-Uk;Chun, Jong-Han
    • Applied Chemistry for Engineering
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    • v.4 no.3
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    • pp.537-543
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    • 1993
  • The effect of agitation on liquid-liquid dispersion was investigated in an immisible liquid phase(n-hexane/water) system. Four different types of six-bladed turbine impellers were used: a flat blade, two screen blades and a solid edged 60 mesh screen blade. We found that the extent of dispersion of organic phase and power consumption of agitator were decreased in the order of flat, solid edged, 60 mesh, and 40 mesh blades at same agitation speed. And the minimum agitation speed for complete dispersion of organic phase was increased with increasing volume fraction of organic phase. Also, mean diameter of liquid droplets of dispersed phase was decreased with increasing agitation speed and it was increased in the order of solid edged, flat, 60 mesh, and 40 mesh screen blades at same agitation speed. At complete dispersion, the minimum power consumption was not vary significantly with impeller blade types, but the solid edged screen blade impeller gave the smallest and uniform sizes of liquid droplets, and it had a good performance for liquid-liquid dispersion. In this condition, Power number was not affected by Reynolds number and it was constant in turbulent flow region, and Sauter mean diameter($d_{32}$) of liquid droplets was expressed as a function of volume fraction of organic phase(${\phi}$) and Weber number($N_{We}$) as follows: $d_{32}/D=a(1+b{\phi})N_{We}{^{-0.6}}$.

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A Study on the Soil Contamination(Maps) Using the Handheld XRF and GIS in Abandoned Mining Areas (휴대용 XRF와 GIS를 이용한 폐광산 지역의 토양오염에 관한 연구)

  • Lee, Hyeon-Gyu;Choi, Yo-Soon
    • Journal of the Korean Association of Geographic Information Studies
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    • v.17 no.3
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    • pp.195-206
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    • 2014
  • In this study, soil contamination maps related to Cu and Pb were created at the Busan abandoned mine in Korea using a handheld X-Ray Fluorescence(XRF) and Geographic Information Systems(GIS). Hydrological analysis was performed using the Digital Elevation Model(DEM) of the study area to identify the flow directions of surface runoff where pollutants can be dispersed from the soil contamination sources. 24 locations for measuring the soil contamination related to Cu and Pb were selected by considering the result of hydrological analysis. The results measured at the 24 locations using the handheld XRF showed that the highest value of Cu contamination is 8,255ppm and that of Pb is 2,146ppm. The field investigation data were entered into ArcGIS software, and then soil contamination maps regarding Cu and Pb with a 5m grid-spacing were created after performing spatial interpolations using the ordinary kriging method. As a result, we could know that high concentrations of Cu and Pb are presented at the waste and tailings dumps around the abandoned mine openings. This study also showed that the handheld XRF and GIS can be utilized to create soil contamination maps related to Cu and Pb in the field.

Population Genetic Structure of Japanese Anchovy (Engraulis japonicus) in Korean waters Based on Mitochondrial 12S Ribosomal RNA Gene Sequences (미토콘드리아 12S 리보종 RNA 유전자배열에 의한 한국해역 멸치 개체군의 유전자 구조)

  • Kim Jin Yeong;Cho Eun Seob;Kim Woo Jin
    • Journal of Life Science
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    • v.14 no.6 s.67
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    • pp.938-950
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    • 2004
  • We used portions of mitochondrial 125 ribosomal RNA gene sequences (339 bp) to investigate the phylogenetic and population genetic characteristics of the Japanese anchovy, Engraulis japonicus, in Korean waters. A total of 35 mtDNA haplotypes were obtained from the samples collected in 3 locations (the southern area of the Yellow Sea, the western coast of Jejudo, and the eastern area of the South Sea) in Korean waters. One haplotype, AN8T103, obtained from the southern area of the Yellow Sea, was formed according to an independent phylogenetic individual in the PAUP analysis, which was separated from the others by a $0.2-4.1\%$ sequence divergence. This distinct haplotype appeared to be one that was carried by immigrants from another study area, but further study is necessary. Genetic divergence, except for AN8T103, was moderate to substantial $(0.2-3.8\%)$ and nucleotide diversity within populations was 0.015 for Yellow Sea, 0.013 for Jejudo, and 0.D15 for South Sea, respectively. The female gene flow was substantial or high (Nm=25.5-36.4), and the genetic distances between regions were not statistically significant $(P>0.01)$. These results indicated that the Japanese anchovy populations occurring in Korean waters were consisted of individuals randomly dispersed over geographic areas.

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

  • Kim, Byungki;Kim, Sohee;Ryu, Kyungsang;Rho, Daeseok
    • Journal of the Korea Convergence Society
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    • v.2 no.4
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    • pp.29-37
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    • 2011
  • Dispersed generation (DG) such as wind power (WP) and Photovoltaic systems (PV) that has been promoted at the national level recently is mainly being introduced into distribution systems adjacent to consumers because it is generation on a small scale when compared to current generation. Due to its characteristics, DG can be operated by interconnection with distribution systems to present security of more stable power and efficient use of power facilities and resources. Problems on protection coordination of distribution systems by reverse flow of DG can roughly be divided into three possibilities: excess in rated breaking capacity (12.5KA) of protective devices by a fault in DG current supply, failure to operate protective devices by an apparent effect that can occur by reduction in impedance parallel circuit fault current due to interconnection of DG, and malfunction of protective devices by interconnection transformer connection type. The purpose of this study is to analyze problems in protection coordination that can occur when DG is operated by interconnection with distribution systems by conducting modeling and simulations by using theoretical symmetrical components and MATLAB/SIMULINK to present methods to improve such problems.

Development of Slurry Flow Control and Slot Die Optimization Process for Manufacturing Improved Electrodes in Production of Lithium-ion Battery for Electric Vehicles (전기자동차 리튬이온 배터리 제조공정에서 Loading Level 산포최소화 코팅을 통한 전극 품질개선에 관한 연구)

  • Jang, Chan-Hee;Lee, Jae-Chon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.3
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    • pp.14-20
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    • 2018
  • Electric vehicles are environmentally friendly because they emit no exhaust gas, unlike gasoline automobiles. However, since they are driven by the electric power from batteries, the distance they can travel based on a single charge depends on their energy density. Therefore, the lithium-ion battery having a high energy density is a good candidate for the batteries of electric vehicles. Since the electrode is an essential component that governs their efficiency, the electrode manufacturing process plays a vital role in the entire production process of lithium-ion batteries. In particular, the coating process is a critical step in the manufacturing of the electrode, which has a significant influence on its performance. In this paper, we propose an innovative process for improving the efficiency and productivity of the coating process in electrode manufacturing and describe the equipment design method and development results. Specifically, we propose a design procedure and development method in order to improve the core plate coating quality by 25%, using a technology capable of reducing the assembly margin due to its high output/high capacity and improving the product capacity quality and assembly process yield. Using this method, the battery life of the lithium-ion battery cell was improved. Compared with the existing coating process, the target loading level is maintained and dispersed to maintain the anode capacity (${\pm}0.4{\rightarrow}{\pm}0.3mg/cm^2r$ reduction).

Oxidation of Phenol Using Ozone-containing Microbubbles Formed by Electrostatic Spray (전기장에 의해 생성된 미세기포를 이용한 페놀의 오존산화)

  • Shin, Won-Tae;Jung, Yoo-Jin;Sung, Nak-Chang
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.12
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    • pp.1292-1297
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    • 2005
  • The use of ozone in water and wastewater treatment systems has been known to be a process that is limited by mass transfer. The most effective way to overcome this limitation is to increase the interfacial area available for mass transfer by decreasing the size of the ozone gas bubbles that are dispersed in solution. Electrostatic spraying(ES) of ozone into water was investigated in this work as a method of increasing the rate of mass transfer of ozone into a solution and thereby increasing the rate of phenol oxidation. Results were obtained for ES at input power levels ranging from 0 to 4 kV and compared with two different pore-size bubble diffusers($10{\sim}15{\mu}m$ and $40{\sim}60{\mu}m$). It was determined that the rate of mass transfer could be increased by as much as 40% when the applied voltage was increased from 0 to 4 kV as a result of the smaller bubbles generated by ES. In addition, ES was shown to be more effective than the medium-pore-size($10{\sim}15{\mu}m$) bubble diffuser and the best results were achieved at low gas flow rates.

Ecological Risk Assessment(ERA) of Abandoned Mine Drainage(AMD) in Korea Based on Vibrio fisheri, Selenastrum capricornutum, and Daphnia magna (국내 폐광산 지역의 Vibrio fisheri, Selenastrum capricornutum, 그리고 Daphnia magna를 이용한 생태 위해성 평가)

  • Kim, Ki-Tae;Lee, Byoung-Cheun;Kim, Dong-Wook;Kim, Sang-Don
    • Journal of Korean Society of Environmental Engineers
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    • v.29 no.2
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    • pp.163-168
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    • 2007
  • Ecological risk assessment(ERA) to 5 abandoned mine drainage was investigated by using chemical measurement and bioassay experiment. From the results of chemical analysis, the high concentration of heavy metals are detected in most area. The Arsenite were mostly detected in Songcheon, Nakdong, and Dukum abandoned mine area, and various heavy metals were highly dispersed in Nakdong area. The study area have also high biological toxicity, resulted from the bioassay based on WET(Whole Effluent Toxicity) test by using Vibrio fisheri, Selenastrum copricornutum, and Daphnia magna. The maximum toxicity was shown in the point where the mine waters start to flow. The sensitivity of toxicity by S. capricornutum was relatively high considering the values of toxicity in all samples, from 1.3 to 32.0 TU. The different sensitivities of toxicity recommends the use of battery system, resulted from at least two test species for bioassay or ecological risk assessment of mine drainage. Besides, the results showed high hazard quotient(i.e., greater than 1 HQ value indicating potentially significant toxic risks) with regard to abandoned mine drainage area in this study. On the other hand, the biological toxicity results were sharply decreased by attenuation along further distance from discharging of mine waters. Therefore, environmental parameters including the dilution factor, dissolved organic matter, and hardness should be considered when the remediation and ERA of abandoned mine drainage is planned.