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Aerodynamic Drag Reduction on High-performance EMU Train by Streamlined Shape Modification (유선형 형상 개선을 통한 고성능 EMU 열차의 공기저항 저감 연구)

  • Kwon, Hyeok-Bin;Hong, Jai-Sung
    • Journal of the Korean Society for Railway
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    • v.16 no.3
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    • pp.169-174
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    • 2013
  • The effect of modifying the shape of a high-performance EMU train on the aerodynamic drag is studied here using Computational Fluid Dynamics(CFD) based on three dimensional Steady-state Navier-Stokes equation and two equation turbulence modeling. FLUENT 12 and Gambit 2.4.6 are employed for a numerical simulation of the aerodynamic drag of a streamlined-shape train as well as a proto type train. The characteristics of the aerodynamic drag of trains in tunnels are analyzed in a comparison with these characteristics in an open space. The contribution of the aerodynamic drag of each case is also investigated to establish principal pertaining to drag reduction for urban trains in tunnels. The aerodynamic drag of a streamlined train was reduced to 9.8% relative to a proto-type train with a blunt nose and a protruding roof facility and underbody shape: the running resistance is expected to be reduced by as much as 4% at a running speed of 80km/h.

Solution of TM Scattering Applying FGMM and PMM for Resistive Strip Grating Between a Grounded Double Dielectric Layer (접지된 2중 유전체층 사이의 저항띠 격자에 대해 FGMM과 PMM을 적용한 TM 산란 해)

  • Uei-Joong Yoon
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.23 no.3
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    • pp.77-82
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    • 2023
  • In this paper, TM(tranverse magnetic) electromagnetic scattering problems for resitive strip grating between grounded double dielectric layers are analyzed by using the FGMM(fourier galerkin moment method) and PMM(point matching method) known as a numerical method of electromagnetic field. The boundary conditions are applied to obtain the unknown field coefficients, the resistive boundary condition is applied to analysis of resistive strip. Overall, when the unoform resistivity decreased, the magnitude of the current density induced in the resistive strip increased, and the reflected power also increased. Also, as the thickness and relative permittivity of the double dielectric layers increased, the overall reflected power increased. The numerical results obtained by using the numerical methods of FGMM and PMM to the structure proposed in this paper agree very well.

A Study on the Conducting Behavior of La-Ca-Mn-O in the vicinity of Phase Transition Temperature (임계점 부근에서 LCMO의 전도 특성에 대하여)

  • 송하정;김우진;권순주
    • Journal of the Korean Magnetics Society
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    • v.8 no.4
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    • pp.179-184
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    • 1998
  • Colossal magnetoresistance is closely related to (but is not) the abrupt change of electrical resistivity in the vicinity of Curie temperature, which is caused by the temperature dependent paramagnetic-ferromagnetic phase transition and concurrent change of electrical conducting mechanism. A resistivity-temperature equation is presented to fully describe the overall behavior, especially the abrupt change. The main ingredients of the equation are a simple effective media theory and a function for the temperature dependent fraction of ferromagnetic phase. The model fits very well to the measured resistivity-temperature curve of $La_{0.7}Ca_{0.3}MnO_3$.

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Effects of Soil Resistivity on the Grounding Characteristics (대지 저항률이 접지 특성에 미치는 영향)

  • Jung, Yeon-Ha;Jang, Tae-Jun;Kwak, Hee-Ro;Roh, Young-Su;Choi, Chung-Seog
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.5
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    • pp.74-79
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    • 2005
  • In this paper the earth structures of four cities are analysed on the basis of the measured soil resistivity and the characteristics of a grounding system is examined. As a result it is revealed that the soil resistivity has an effect on touch voltage and step voltage, which are directly related to safety, as well as ground resistance.

Numerical Experiment for the Estimation of Equivalent Resistance Coefficient for the Simulation of Inundation over Densely Populated Structures (구조물 밀집지역 범람수치모의를 위한 상당저항계수 산정 수치실험)

  • Kim, Hyeong-Seok;Choi, Jun-Woo;Ko, Kwang-Oh;Yoon, Sung-Bum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.20 no.6
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    • pp.532-539
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    • 2008
  • Kwon et al.(2008) carried out a hydraulic experiment in order to evaluate Manning coefficient, which implicates flow resistance due to bottom friction as well as drag caused by the squared piers higher than water depth and arranged with equal intervals, under the flow condition with a constant drag coefficient, $Re>10^4$. And, based on the equation of equilibrium, they proposed a formula for the equivalent resistant coefficient including empirical drag interaction coefficient obtained by using the experimental results. In this study, the hydraulic experiment was simulated using FLOW-3D, a 3-dimensional computational fluid dynamic code. The computations were compared with the experiment results as well as the semi-theoretical formula, and the comparisons show a good agreement. From the agreement, it was confirmed that when flow resistance bodies were higher than water depth, Manning n value increases with 2/3 power of water depth as shown in the theoretical formula and that drag interaction coefficient was dominated by their intervals.

Effect of Stern Wedge on the Wave Making Resistance of Chine Hull Form (선미 웨지가 차인선형의 조파저항에 미치는 영향)

  • Lee Dae-Hoon;Lew Jae-Moon;Kang Dae-Sun
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.9 no.2
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    • pp.92-97
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    • 2006
  • Hull forms of a high speed small boat have been developed through numerical studies. A round bilge type hull form has been drived form a using chine hull form with HCAD, a hull form variation software. Wave resistance and the flow fields around the ships have been computed using well-known software, WAVIS. This software employs Rankine source method with non-linear tree surface condition as well as dry transom boundary conditions. The round bilge hull form showed better resistance performance than to the chine hull form for the whole speed range. However, considering the building and labor costs of the small shipyard, the chine hull form has been selected and its wave resistance characteristics has been improved by modifying the bow regions and applying the stem wedge. It is found that the effect of stem wedge is quite satisfactory to improve the resistance characteristics of high speed chine hull form.

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A Study on the Factors Affecting the Adoption of Traceability system : Focused on the Korea ginseng farm industry (생산이력시스템 도입 정책에 대한 수용과 저항 요인에 관한 연구 : 인삼 분야를 중심으로)

  • Park, Woo Seok;Rhee, Cheul;Moon, Jung Hoon;Yi, Eun Seob
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.9 no.5
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    • pp.95-101
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    • 2014
  • With the evocative interests in food safety, food traceability has been spotlighted by researchers as well as consumers. However, food traceability systems are not yet in reality even though there are continuous needs from market. Also, studies about food traceability focus on technical aspects without considering the spectrum of the adoption. In this study, we chose ginseng whose traceability systems are not easily adopted. Innovation-resistance model is employed to find out factors affecting either adoption, resistance or both. As results, we find out the followings. First, relative benefits and reasonableness of cost do not affect adoption and resistance of innovation. Second, there is difference between continuously resisting group and adoption-postponing group.

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Selection in $F_3$ and $F_4$ Generations of a Cross for Breeding Genic Male Sterile Pepper Lines Resistant to Phytophthora Blight and Bacterial Spot (역병과 세균성점무늬병에 복합저항성인 핵유전형 웅성불임성 고추 계통 육성을 위한 교배의 $F_3-F_4$세대 선발)

  • Park, Dong-Keun;Kim, Byung-Soo
    • Current Research on Agriculture and Life Sciences
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    • v.28
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    • pp.17-23
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    • 2010
  • Selection procedures for breeding genic male sterile lines for resistance to both Phytophthora blight caused by Phytophthora capsici and bacterial spot caused by Xanthomonas euvesicatoria were executed to $F_3$ and $F_4$ generations derived from a cross between a Phytophthora resistant genic male sterile (GMS) breeding line and a bacterial spot and Phytophthora resistant breeding line. Resistance to P. capsici was originally introduced from KC294(CM334) and KC263(AC2258), the well-known sources of resistance to P. capsici. Resistance to bacterial spot was introduced from KC47(PI244670). GMS lines with high resistance to P. capsici were obtained and the selected lines are expected to be quantitatively resistant also to bacterial spot.

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Laboratory study on the electrical resistivity characteristics using an artificial agar specimen with clay minerals (점토광물을 함유하는 한천인공시료를 이용한 전기비저항 특성에 관한 실험적 연구)

  • Park, Mi-Kyung;Park, Sam-Gyu;Kim, Hee-Joon
    • 한국지구물리탐사학회:학술대회논문집
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    • 2005.05a
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    • pp.65-70
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    • 2005
  • A low resistivity zone is found in many places such as a fractured fault zone, weathered zone and aquifer. The electrical resistivity is influenced mainly by pore fluid as well as the clay mineral types and contents, Hence, it is very important to understand the relationship between the electrical resistivity and clay contents associated with the low resistivity zone for geotechnical applications such as civil engineering. This study examines the characteristics of clay mineral types and contents to electrical resistivity through sample measurements, and proposes an expression relating the resistivity and clay content. The electrical resistivity is measured for an artificial agar specimen with clay minerals instead of a natural rock. The clay minerals used are Kaolinite and Montmorillonite. Montmorillonite shows remarkably lower resistivity than Kaolinite, although its clay content is fewer than that of Kaolinite. Also, the proposed expression shows a good correlation coefficient as high as 0.89 or more in all clay minerals.

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Studies on the disease resistance of tobacco varieties to Black shank, Black root rot Wild fire, Brown spot, CMV-Y and Blue mold -Disease resistance of Korean native varieties- (담배중요병해저항성에 관한 연구 특히 한국재래종에 대하여)

  • Il Hou
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.4 no.1
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    • pp.103-108
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    • 1968
  • Resistance to various diseases of Korean native varieties were investigated in field. The results obtained are summarized as follows: 1) The varieties Ubangtchio and Osib-eubthio were moderately resistant to black shank, but Suantchio, Usultchio and Gwangtchio were slightly resistant. Dixie Bright 101, $H_2$ and Bright Yellow 4 were more resistant to black shank than any of the Korean native varieties. 2) Mokgitchio, Ubangtchio and Osib-eubtchio were moderately resistant to black root rot, but Useultchio Suantchio and Hoetchio were susceptible than Others. 3) Muktchio, Hoetchio and Ubangtchio were slightly resistant to wild fire. 4) Osib-ebthio was highly resistant to brown spot, but Ubangtchio, Hyangtchio and Mokgitchio were moderately resistant and Useultchio was susceptible to brown spot, but it was resistant than Bright ellow 4 or Bernhart 1000-1. 5) Hyangtchio was slightly resistant to CMV-Y. According to these results, except Virus disease, Ubangtchio was resistant to all of the above mentioned diseases. Osib-eubtchio, Hoetchio, Hyangtchio and Suantchio showed proferable disease resistant and these might be well utilized as breeding materials.

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