• 제목/요약/키워드: potential distribution

검색결과 2,892건 처리시간 0.035초

마이크로 채널 내부 전기삼투 유동의 Zeta-potential 계측 (Measurement of Zeta-potential of Electro-osmotic Flow Inside a Micro-channel)

  • 한수동;이상준
    • 대한기계학회논문집B
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    • 제30권10호
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    • pp.935-941
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    • 2006
  • Many important properties in colloidal systems are usually determined by surface charge $({\zeta}-potential)$ of the contacted solid surface. In this study, ${\zeta}-potential$ of glass ${\mu}-channel$ was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass f-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The ${\zeta}-potential$ in the glass ${\mu}-channel$ was measured fur two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and f-potential in the glass surface was also studied. In the range of $0{\sim}6mM$, the surfactant SDS was added to NaCl solution in few different mole concentrations. As a result, the addition of SDS increases ${\zeta}-potential$ in the surface of the glass ${\mu}-channel$. The measured $\zeta-potential$ was found to vary from -260 to -70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The ${\zeta}-potential$ has a positive sign for the negative particles.

SCBF 장치에서 이온전류에 대한 포텐셜 우물 구조의 영향 (Effect of Potential Well Structure on Ion Current in SCBF Device)

  • 주흥진;박정호;고광철
    • 한국전기전자재료학회논문지
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    • 제20권5호
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    • pp.471-477
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    • 2007
  • SCBF(Spherically Convergent Beam Fusion) device has been studied as a neutron source. Neutron production rate is a most important factor for the application of SCBF device and is proportional to the square of the ion current[1]. It is regarded generally that some correlations between the potential well structure and the ion current exist. In this paper, the ion current and potential distribution were calculated in a variety of grid cathode geometries using FEM-FCT method. Single potential well structure was certified inside the grid cathode. The deeper the potential well became, the higher the ion current due to the high electric field near the grid cathode became.

지표면전위 해석에 의한 접지저항 측정기법에 관한 연구 (A Study on the Measurement of Grounding Resistance based on the Earth Surface Potential Analysis)

  • 윤장완;안용호;정길조;한병성
    • 조명전기설비학회논문지
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    • 제16권4호
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    • pp.117-123
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    • 2002
  • 접지저항의 측정은 접지계통의 접지성능이 적정한가를 평가하기 위한 가장 기본적이고 중요한 작업이라고 할 수 있다. 그러나 실제 현장에서, 특히 접지극의 크기가 큰 경우일수록 접지저항을 정확히 측정하기란 쉽지 않은데, 이는 정확한 접지전위 측정을 위한 기준전위 점을 찾기가 힘들기 때문이다. 본 논문에서는 접지극 주변에서 측정한 지표면전위를 분석하여 기준전위 점의 위치를 정확히 식별하는 방법과 그 정당성을 제시하였다.

GARP 모형과 기후변화 시나리오에 따른 잣나무의 지리적 분포 변화 (Shifts of Geographic Distribution of Pinus koraiensis Based on Climate Change Scenarios and GARP Model)

  • 천정화;이창배;유소민
    • 한국농림기상학회지
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    • 제17권4호
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    • pp.348-357
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    • 2015
  • 본 연구는 그간 우리나라에서 경제적인 가치를 인정 받아온 수종인 잣나무를 대상으로 잣나무의 현존 분포를 파악하고, RCP (Representative Concentration Pathway) 8.5 기후변화 시나리오와 생태적 지위 모형에 기반하여 향후 잣나무의 분포 변화를 예측하기 위해 수행되었다. 이를 위해 5년간의 NFI 자료에서 조사지점별 잣나무의 풍부도 자료를 추출하여 사용하였으며, 수종에 영향을 미치는 환경요인변수를 선정하기 위해 생태적 지위 모형 가운데 하나인 GARP (Genetic Algorithm for Rule-set Production)를 이용하였다. 총 27개의 환경요인변수에 대해 각각 모형을 구동하고 컨퓨전 매트릭스(Confusion Matrix) 기반 산출 통계량인 AUC (Area Under Curve)가 0.6 이상인 변수들을 선발하여 최종 잠재분포모형을 작성하였다. 그 결과 작성된 모형은 비교적 높은 적합도를 나타냈는데 잣나무는 현재 표고의 범위가 300m에서 1,200m 사이인 지역 및 남부에서 북부에 이르기까지 넓게 자리 잡고 있는 것으로 나타났다. 작성된 모형에 RCP 8.5 기후변화 시나리오를 적용한 결과, 잣나무는 2020년대부터 잠재분포역이 큰 폭으로 축소되며, 2090년대에는 우리나라 대부분의 지역이 잣나무의 생육에 불리할 것으로 예측되었다. 본 연구를 통해 기후변화가 잣나무 분포에 미치는 영향을 파악하고, 잣나무와 기후변화와의 상관성에 대한 이해를 높임으로써 향후 지역별 조림수종 선정 및 경제수종 교체 등의 조림적 관점에서 도움이 될 수 있을 것으로 판단된다.

기후변화에 따른 우리나라 특산식물의 잠재적 분포적지 변화 예측 - 모데미풀을 중심으로 - (Projecting Climate Change Impact on the Potential Distribution of Endemic Plants (Megaleranthis saniculifolia) in Korea)

  • 이상혁;정휘철;최재용
    • 한국환경복원기술학회지
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    • 제15권3호
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    • pp.75-84
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    • 2012
  • The importance of the genetic value of native plants has been raised recently after the adoption of Nagoya Protocol. In this stream, this research focused on the future distribution of Megaleranthis saniculifolia which has been evolved and adapted to Korean natural environment and classified as an endemic endangered species by IUCN. The distribution of the species in future are projected based on 'present potential distribution area' by adopting SRES (Special Report on Emission Scenarios) A1B climate change scenario using 6 types of GCM (General Circulation Model). The major results of the research are as follows : habitats of Megaleranthis saniculifolia. (1) will be reduced by 44% nation wide; (2) in Chungcheongngnam Do and Jeollanam Do will be the most affected; and (3) in high altitude in Chungcheongbuk Do, Gyunggi Do and Gangwon Do will be relatively less affected.

잠재 산림분포 변화를 고려한 토지이용도가 장래 기후변화에 미치는 영향 모사 (A Simulation Study on Future Climate Change Considering Potential Forest Distribution Change in Landcover)

  • 김재철;이종범;최성호
    • 환경영향평가
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    • 제21권1호
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    • pp.105-117
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    • 2012
  • Future climate according to land-use change was simulated by regional climate model. The goal of study was to predict the distribution of meteorological elements using the Weather Research & Forecasting Model (WRF). The KME (Korea Ministry of Environment) medium-category land-use classification was used as dominant vegetation types. Meteorological modeling requires higher and more sophisticated land-use and initialization data. The WRF model simulations with HyTAG land-use indicated certain change in potential vegetation distribution in the future (2086-2088). Compared to the past (1986-1988) distribution, coniferous forest area was decreased in metropolitan and areas with complex terrain. The research shows a possibility to simulate regional climate with high resolution. As a result, the future climate was predicted to $4.5^{\circ}$ which was $0.5^{\circ}$ higher than prediction by Meteorological Administration. To improve future prediction of regional area, regional climate model with HyTAG as well as high resolution initial values such as urban growth and CO2 flux simulation would be desirable.

위성영상과 Maxent를 활용한 생태계교란생물 분포지역 예측 : DMZ의 단풍잎돼지풀을 대상으로 (Predicting the Potential Distributions of Invasive Species Using the Landsat Imagery and Maxent : Focused on "Ambrosia trifida L. var. trifida" in Korean Demilitarized Zone)

  • 박현철;임정철;이정환;이관규
    • 한국환경복원기술학회지
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    • 제20권1호
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    • pp.1-12
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    • 2017
  • This study has been carried out for the purpose of predicting the potential habitat sites of invasive alien plants in the DMZ and providing the basic data for decision-making in managing the future DMZ natural environment. From 2007 to 2015, this study collected the data for the advent of Ambrosia trifida var. trifida through fieldwork around the DMZ area, and simulated the potential distribution area of Ambrosia trifida var. trifida using Maxent model among the models of species distributions. As a result, it showed that the potential distribution area of the Ambrosia trifida var. trifida was concentrated in the western DMZ with relatively low altitude and scanty in the central east regions with relatively high elevation and forest cover rate. Because the invasive alien vegetation is a significant threatening factor in the agriculture and restoration of ecology and it costs a lot to restore the area already invaded by invasive alien vegetation, advance precautions are necessary to prevent biological invasions. It is expected that it is possible to predict the disturbed ecosystems through this study for the efficient land use within DMZ in the future and to apply this study in setting up the areas for the development and conservation within the DMZ.

Cu(In,Ga)$Se_2$ 박막의 Cu 결함 및 In, Ga 비율의 변화에 따른 구조적, 광학적, 전기적 특성 연구 (Structural, optical, and electrical properties on Cu(In,Ga)$Se_2$ thin-films with Cu-defects and In/(In+Ga) ratio)

  • 정아름;김지영;조윌렴;조현준;김대환;성시준;강진규;이동하;남다현;정현식
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2011년도 추계학술대회 초록집
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    • pp.47.1-47.1
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    • 2011
  • We report on a direct measurement of two-dimensional chemical and electrical distribution on the surface of photovoltaic Cu(In,Ga)$Se_2$ thin-films using a nano-scale spectroscopic and electrical characterization, respectively. The Raman measurement reveals non-uniformed surface phonon vibration which comes from different compositional distribution and defects in the nature of polycrystalline thin-films. On the other hand, potential analysis by scanning Kelvin probe force microscopy shows a higher surface potential or a small work function on grain boundaries of the thin-films than on the grain surfaces. This demonstrates the grain boundary is positively charged and local built-in potential exist on grain boundary, which improve electron-hole separation on grain boundary. Local electrical transport measurements with scanning probe microscopy on the thin-films indicates that as external bias is increases, local current is started to flow from grain boundary and saturated over 0.3 V external bias. This accounts for carrier behavior in the vicinity of grain boundary with regard to defect states. We suggest that electron-hole separation at the grain boundary as well as chemical and electrical distribution of polycrystalline Cu(In,Ga)$Se_2$ thin-films.

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속도포텐셜접속법과 특이점분포법에 의한 방파제에 근접한 부유식 해상공항에 대한 유탄성 응답 해석 (Hydroelastic Responses for a VLFS close to a Breakwater by the Velocity Potential Continuation and Singularity Distribution Method)

  • 이호영;곽영기;박종환
    • 대한조선학회논문집
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    • 제39권2호
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    • pp.11-18
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    • 2002
  • 본 논문은 착저식 방파제를 고려하여 방파제 후면에 위치한 부유식 해상공항의 파도 중에서 유탄성 응답을 계산하는 방법을 제시하였다. 방파제 효과를 고려한 일반화된 방사문제를 해석하기 위하여 소오스-다이폴 분포법을 사용하였고, 산란문제를 해석하기 위하여 속도포텐셜접속법과 소오스-다이폴 분포법을 이용하였다. 구조물의 응답은 자유-자유 보의 고유 모드함수에 의한 모드 해석법을 사용하여 계산하였다. 계산 모델로 길이가 1000m의 해상공항 구조물을 도입하였고, 방파제의 효과를 살펴보기 위해 방파제와 해상공항사이의 거리 및 입사화랑의 각도를 변화시키면서 수직 응답 및 굽힘 모우멘트 등을 계산하였다.

기후변화 시나리오에 의한 외래식물 실망초(Conyza bonariensis)의 서식지 분포 예측 (Predicting the Suitable Habitat of Invasive Alien Plant Conyza bonariensis based on Climate Change Scenarios)

  • 이용호;오영주;홍선희;나채선;나영은;김창석;손수인
    • 한국기후변화학회지
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    • 제6권3호
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    • pp.243-248
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    • 2015
  • This study was conducted to predict the changes of potential distribution for invasive alien plant, Conyza bonariensis in Korea. C. bonariensis was found in southern Korea (Jeju, south coast, southwest coast). The habitats of C. bonariensis were roadside, bare ground, farm area, and pasture, where the interference by human was severe. Due to the seed characteristics of Compositae, C. bonariensis take long scattering distance and it will easily spread by movement of wind, vehicles and people. C. canadensis in same Conyza genus has already spread on a national scale and it is difficult to manage. We used maximum entropy modeling (MaxEnt) for analyzing the environmental influences on C. bonariensis distribution and projecting on two different RCP scenarios, RCP 4.5 and RCP 8.5. The results of our study indicated annual mean temperature, elevation and temperature seasonality had higher contribution for C. bonariensis potential distribution. Area under curve (AUC) values of the model was 0.9. Under future climate scenario, the constructed model predicted that potential distribution of C. bonariensis will be increased by 338% on RCP 4.5 and 769% on RCP 8.5 in 2100s.