• Title/Summary/Keyword: Field Width

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A Study on the Coupling of a Flanged Parallel-Plate Waveguide to a Nearby Conducting Strip from the Viewpoint of Near-Field Scanning Microscopy (근접주사현미경의 관점에서 플랜지된 평행평판 도파관과 근접도체스트립과의 결합에 관한 연구)

  • Lee, Jong-Ig;Ko, Ji-Hwan;Cho, Young-Ki
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.11
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    • pp.2260-2266
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    • 2009
  • In this paper, the problem of electromagnetic coupling between a slit fed by a flanged parallel-plate waveguide (FPPW) and a nearby conducting strip parallel to the slit is studied as a simplified problem for a near-field scanning microscopy (NSM). The characteristics of the FPPW are investigated from the results for the variations of the equivalent slit admittance, the reactive powers near the slit inside and outside the FPPW, the magnitude and phase of the voltage reflection coefficient of the TEM wave. The performance of the proposed apparatus as an NSM is tested by examining the effects of various geometrical parameters such as guide height, slit width, strip width, distance between slit and strip, and the ratio of slit width to guide height on the magnitude and phase of the voltage reflection coefficient of the TEM wave. From the results for the voltage reflection coefficient against the strip offset from the slit, it is found that a slit in the FPPW with smaller guide height gives higher scanning resolution and the phase variation is more sensitive than the magnitude variation.

Dynamics of Transverse Magnetic Domain Walls in Rectangular-shape Thin-film Nanowires Studied by Micromagnetic Simulations

  • Lee, Jun-Young;Choi, Sang-Kook;Kim, Sang-Koog
    • Journal of Magnetics
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    • v.11 no.2
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    • pp.74-76
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    • 2006
  • Dynamic behaviors of transverse domain walls (TDWs) in rectangular shaped thin-film magnetic nanowires with different widths under applied magnetic fields less than the Walker field were studied by micromagnetic simulations. It was found that the velocity of stable TDWs in the viscous region increases from 147 to 419 m/s and their mass decreases from $6.24{\times}10^{-23}\;to\;2.70{\times}10^{-23}kg$ with increasing strength of the applied magnetic field ranging from 5 to 20 Oe for the nanowire with a dimension of 10 nm in thickness and $5{\mu}m$ in length, and 50 nm in width. With increasing the width of nanowires from 50 to 125 nm at a specific field strength of 5 Oe, the TDW's velocity also increases from 147 to 246 m/s and its mass decreases from $6.24{\times}10^{-23}\;to\;5.91{\times}10^{-23}kg$.

Filamentation and α-factor of broad area laser diodes (대면적 레이저 다이오드의 필라멘테이션과 α-factor)

  • Han, Il-Ki;Her, Du-Chang;Lee, Jung-Il;Lee, Joo-In
    • Korean Journal of Optics and Photonics
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    • v.13 no.4
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    • pp.319-323
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    • 2002
  • 1.55 ${\mu}m$multi-quantum well (MQW) broad area laser diodes with different linewidth enhancement factors ($\alpha{-factor}$) of 2 and 4 were fabricated. The far-fields of the laser diodes were measured. It was observed that the full width at half maximum (FWHM) of the far-fields and the filamentations were reduced in the laser diodes for which the value of the $\alpha{-factor}$ was small. As injection current increased, the FWHM of the far-field also increased regardless of the a-factor. This phenomenon was explained by reduction of filament spacing as injection current increased.

A Study on Sample Size Dependence of Ferromagnetic Resonance in Polycrystalline Magnesium Ferrites (마그네슘 페라이트에서 강자성 공명의 시료 크기 의존성 연구)

  • 한기태;백종규
    • Journal of the Korean Ceramic Society
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    • v.32 no.2
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    • pp.163-170
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    • 1995
  • Sample size effect on ferromagnetic resonance (FMR) in polycrystalline MgFe2O4 has been investigated. The signal intensity (SI), resonance field (Hres) and line width (ΔH) were found to increase proportionally to r3 with the increase of sample radius. The r3-depencence of SI means the complete penetration of rf-field into the sample, and the broadening of ΔH due to the sample size appears to be closely related to the amount of scattering sources like pores. Meanwhile, the values of Hres (0) and ΔH (0) obtained by extrapolating the data of Hres (r) and ΔH (r) measured at several sizes to r=0, were in good agreement with those calculated using the Schlomann's equations for internal field and ΔH, respectively. This result indicates that the discrepancy between the measured FMR parameters and those calculated by Schlomann's equation could be ascribed to the effect of sample size. Thus it is suggested that the size effect on FMR should be removed for the analysis of the FMR parameters. Meanwhile, our result for the size dependance of ΔH was found to be contradictory to those reported by Dionne, where ΔH 1/r at a given surface roughness. This discrepancy appears to arise from the difference in the definition of reading the line width.

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Characteristics of Nanolithography Process on Polymer Thin-film using Near-field Scanning Optical Microscope (근접장현미경을 이용한 폴리머박막 나노리쏘그라피 공정의 특성분석)

  • 권상진;김필규;장원석;정성호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.590-595
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    • 2004
  • The shape and size variations of the nanopatterns produced on a positive photoresist using a near-field scanning optical microscope(NSOM) are investigated with respect to the process variables. A cantilever type nanoprobe having a 100nm aperture at the apex of the pyramidal tip is used with the NSOM and a He-Cd laser at a wavelength of 442nm as the illumination source. Patterning characteristics are examined for different laser beam power at the entrance side of the aperture( $P_{in}$ ), scan speed of the piezo stage(V), repeated scanning over the same pattern, and operation modes of the NSOM(DC and AC modes). The pattern size remained almost the same for equal linear energy density. Pattern size decreased for lower laser beam power and greater scan speed, leading to a minimum pattern width of around 50nm at $P_{in}$ =1.2$\mu$W and V=12$\mu$m/. Direct writing of an arbitrary pattern with a line width of about 150nm was demonstrated to verify the feasibility of this technique for nanomask fabrication. Application on high-density data storage using azopolymer is discussed at the end.

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Optimum Coagulation of Water Treatment Plant using On-line Floc Monitoring System (정수장 응집제주입 최적화를 위한 플럭 모니터링)

  • Hwang, Hwando;Lim, Sangho;Sung, Kyujong;Han, Youngjin;Kim, Youngbeom;Kwak, Jongwoon
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.4
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    • pp.397-406
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    • 2009
  • This study was conducted to monitor the floc sizes forming in the mixing zone in the water treatment plant. The dosing amount of poly aluminium chloride(PAC) was determined by particle dispersion analyzer(iPDA) in the lab and field scale test. During a field test period, PAC coagulant was used and the raw water was taken from Nakdong river. PAC wad diluted to activate the coagulant, leading to bring the more homogeneous dispersion in the shorter time. To monitor the floc sizes, the unit of floc size index(FSI) was used. With increasing of raw water turbidity, FSI value was increased. Also, the increased dosing amount of PAC brought the increased FSI and with overdosing of coagulant was in turn decreased. When the PAC was fed into the raw water after dilution in a field scale test, the width of FSI was narrower compared with the feeding of the mother liquor of PAC, implying that the formed flocs are denser and more uniform sizes. The width of FSI in average was varied on depending on the basicity of coagulant. Also, dF value, fractal dimension was evalued with the different coagulants, showing from 2.01 to 2.03. On-line floc monitor was effective for the optimal dosing in the drinking water plant.

Experimental Study for Installation Damage Assessment of Geogrid (지오그리드의 시공중 손상 평가를 위한 실험적 연구)

  • Cho, Sam-Deok;Lee, Kwang-Wu;Oh, Se-Yong
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.8 no.1
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    • pp.27-36
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    • 2005
  • Geosynthetic reinforcements may be damaged during its installation in the filed. The installation damage mainly depends on two factors such as materials used and construction activities. This paper describes the results of a series of field tests, which are conducted to assess the installation damage of geogrid according to different maximum grain sizes of fills (40, 60, and 80 mm). These tests are done in three sites for twelve different kinds of geogrids. After field tests, the changes in tensile strength of the geogrids is determined from wide width tensile tests using both damaged and undamaged specimens. In the results of tests, tensile strength of the relatively flexible geogrids after field installation tests was decreased about from 20% to 40% according to the increment of the maximum grain size. On the other hand, for the relatively stiff geogrids, the loss of the tensile strength after site installation was examined below 5.2% independent of the maximum grain size of the soils. The results of this study show that the installation damage significantly depends on the stiffness of geogrid and is more obvious to a flexible geogrid and a fill material having higher maximum grain size.

Numerical Study of Land/Channel Flow-field Optimization in Polymer Electrolyte Fuel Cells (PEFCs) (I) -The Effects of Land/Channel Flow-field on Current Density and HFR Distributions- (고분자전해질형연료전지의 가스 채널 최적화를 위한수치적연구(I) -가스 채널 치수가 전류밀도와 HFR 분포에 미치는영향성-)

  • Ju, Hyun-Chul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.9
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    • pp.683-694
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    • 2008
  • The performance and durability of Polymer Electrolyte Fuel Cells (PEFCs) are strongly influenced by the uniformity of current density, temperature, species distributions inside a cell In order to obtain uniform distributions in them, the optimal design of flowfield must be a key factor. In this paper, the numerical study of land/channel flowfield optimizations is performed, using a multi-dimensional, multi-phase, non-isothermal PEFC model. Numerical simulations reveal more uniform current density and HFR(High Frequency Resistance) distributions and thus better PEFC performance with narrower land/channel width where the less severe oxygen depletion effect near the land region and more uniform contact resistance variation along the in-plane direction are achieved. The present study elucidates detailed effects of land/channel width and assist in identifying optimal flow-field design strategies for the operation of PEFCs.

Field Wave Data Analysis for Investigation of Freak wave Characteristics (Freak wave 특성 파악을 위한 파랑관측 자료의 분석)

  • Shin, Seung-Ho;Hong, Key-Yong;Moon, Jae-Seung
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.175-180
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    • 2006
  • This study is carried out the investigation of nonlinear characteristics of the ocean based on the field wave observation data acquired the western sea area in Jeju island during one year. It is aimed to offer the fundamental data for Freak wave forecasting in real sea. For this, the nonlinearity parameters of ocean waves, which are Skewness, Atiltness, Kurtosis and Spectrum band width parameter, are introduced, and the parameters are compared and discussed with some characteristic wave components, ie, significant wave height, maximum wave height, and so on.

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A Study on the Revegetation Structural Analysis for Environment Factor of Road Slope (도로비탈면의 환경인자를 고려한 식생구조분석에 관한 연구)

  • Jeon, Gi-Seong
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.2
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    • pp.12-20
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    • 2004
  • This study was carried out from January 1998 to December 1999 to report the revegetation of cutting-rock slopes and a design standard in the highway cut-slopes. The field data was collected from the 67 sites cutting-rock slopes of highways, local roads, and field test. As the result of analyze, cutting-rock slopes revegetation measures were 16 types. There were Vine planting(3 types), Hydroseeding measures with seed-fertilizer-soil materials(5 types), Vegetaion-base spraying measures(5 types), and Stability measures(3 types). The factors affecting the plant coverage rates of cutting-rock slopes were the slope gradient, the slope width and direction. The plant coverage rate decreases in the condition of steep slope and long slope width and length(height). In addition, the plant coverage rates of the westward and southward were lower than that of the northward and eastward. Most dominant species were Zoysia japonica, Lespedeza cyrtobotrya, Lespedeza cuneata, Rubus crataegifolius, Miscanthus sinensis, Arrundinella hirta, Themeda triandra, and Oenothera odorata. Exotic species were Eragrostis curvula(Weeping lovegrass), Dactylis glomerata Orchardgrass), Lolium perenne(Perennial ryegrass), and Festuca arundinacea(Tall fescue). It is recommended to adjust the proposed factor as environment, topsoil, classification of rock, field condition and characteristic related with revegetation measures on slopes for the presentation of revegetation standard.