• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.2
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• pp.36-44
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• 2001

The main purpose of this study was to classify forest vegetation effectively using Landsat Thematic Mapper data(June, 1994) in mountainous region. The research area was the Mt. Wolak Experimental Forest of Chungbuk National University, near Chungju and Jecheon city, Chungcheongbuk-do. To classify forest vegetation effectively, Normalized Difference Vegetation Index(NDVI) was used to reduce topographic effects. This NDVI was modified and transformed to the value of 0 to 255, and then the modified values were combined with other Landsat Thematic Mapper bands. To classify forest and land cover types, unsupervised classification method was used. The results of this study are summarized as follows. 1. Combinations of band "3, 5, NDVI" in Landsat Thematic Mapper data showed a good separation with high accuracy. The expected classification accuracy was 95.1% in Landsat Thematic Mapper data. 2. The Land Cover types were classified into six groups : coniferous forest, deciduous forest, mixed forest, paddy and grass, non-forest, and other undetectable areas. As these classified results were compared with the reconnaissance survey and aerial black and white infrared photographs, the overall classification accuracy was 76.5% in Landsat Thematic Mapper data. 3. The portion of non-forest in Mt. Wolak area was 1.9%. The percentages of coniferous, deciduous and mixed forests were 30.9%, 35.7% and 26.4%, respectively. 4. As these classified results were compared with other reference data, the percentages of coniferous, deciduous and mixed forests increased, but the portion of non-forest was exceedingly diminished. These differences are thought to be from the different research method and the different season of received Landsat Thematic Mapper data.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.9-25
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• 1994

In the present study, the Reynolds-averaged Navier-Stokes equations, together with the equations of the $k-{\varepsilon}$ model of turbulence, were solved numerically in a general body-fitted coordinate system for three-dimensional turbulent flows around the six basic shapes of the magnetically levitated train(MAGLEV). The numerical computations were conducted on the MAGLEV model configurations to provide information on shapes of this type very near the elevated track at a constant Reynolds number of $1.48{\times}10^{6}$ based on the body length. The coordinate system was generated by numerically solving a set of Poisson equations. The convective transport equations were discretized using the finite-analytic scheme which employed analytic solutions of the locally-linearized equations. A time marching algorithm was employed to enable future extensions to be made to handle unsteady and fully-elliptic problems. The pressure-velocity coupling was treated with the SIMPLER-algorithm. Of particular interests were wall effect by the elevated track on the aerodynamic forces and flow characteristics of the six models calculated. The results indicated that the half-circle configuration with extended sides and with smooth curvature of sides was desirable because of the low aerodynamic forces and pitching moment. And it was found that the separation bubble was occured at wake region in near the elevated track.

• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.158-163
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• 2011

The small-loop electromagnetic (EM) survey is an effective method to delineate contamination areas and pathways of contaminant plumes from landfill. A multi-frequency small-loop EM survey was applied to find them at landfill area, located in delta region, and checked the results with in-situ surveys including 24 trench excavations and 12 drilling boreholes. The correlation between these two results indicates this survey would be suitable to investigate the contamination area. However, it would be difficult to analyze low resistivity less than 10 ohm-m below 10 m depth in delta area without drilling survey because of a limitation to expand the penetration depth lower than 10 m depth due to the separation of 1.66 m between the two coils of GEM-2.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.157-168
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• 1995

The structural performance of Slip-Form system was examined to make use of many advantages of fast construction and high quality c0ncret.e. However, the separate cor~struction of wall and slabs may cause some weaknesses around the wall-slab connection region. Thus, the purpose of the study is to examine the structural performance of wall-type structure constructed by Slip-Form method and to develop an efficient connection system between wall and slabs. In order to investigate the system, 7 wall specimens and 8 wall-slab joint specimens were tested and the experimental results were compared with the design equations and theoretical analysis. A satisfactory performance was obtained from the wall specimen tests. However, wall-slab joint specimens with rebar connection materials I Ilalfen] were shown that. the strength of' wall should be checked during design porocess.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.87.2-87.2
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• 2017

RR~Telescopii is a symbiotic nova exhibiting accretion activities through gravitational capture of the slow stellar wind from a Mira variable. We present high resolution spectra of RR~Tel obtained with MIKE and the 6.5 m Magellan-Clay telescope, in which we find broad features with FWHM exceeding $10{\AA}$ at 6545, 6825, 7082, 7023 and $7053{\AA}$. They are formed through Raman-scattering with atomic hydrogen of far-UV He II 1025, O~VI 1032, $1038{\AA}$ and C II 1036 and $1037{\AA}$. We compute the Raman conversion efficiencies using the case B recombination theory for He II emissions, which are used in turn to infer the intrinsic line luminosities of O VI and C II. The Raman O~VI features are characterized by double-peaked profiles with a peak separation ~ 60km/s, pointing out the presence of an accretion disk with a physical size of ~ sub AU. In contrast, Raman C II features exhibit profiles with a simple peak and a narrower width ~40 km/s, indicating that C II is formed in a much more extended region. The weak C II multiplet at 1335, $1336{\AA}$ found in the IUE spectral archive and the absence of C II 1036, $1037{\AA}$ in the FUSE archive show that far-UV C II lines suffer heavy interstellar extinction consistent with the distance of ~ 2.5 kpc to RR Tel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.578-586
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• 2002

Flow structures around a rectangular prism have been investigated by using a PIV(Particle Image Velocimetry) technique. A thick turbulent boundary layer was generated by using spires arid roughness elements. The boundary layer thickness, displacement thickness and momentum thickness were 650mm, 117.4mm and 78mm, respectively. The ratio between the model height(40mm) and the boundary layer thickness H/$\delta$, was 0.06. The Reynolds number based on the free stream velocity and the height of the model was 7.9$\times$10$^3$. The PIV measurements were performed at three different wall normal planes. Three recirculation regions at forward facing step, top of the roof and backward facing step are clearly seen and show three dimensional features. Dramatic changes of flow patterns are observed in the wake regions in the different spanwise wall normal planes. Instead of reattachment and recirculation zone, rising streamlines are depicted at the normal planes near the side wall due to the interaction with a rising horse shoe vortex. The peak of turbulent kinetic energy occurs at the separation bubble on top of the roof and the magnitude is 2.5 times higher compared with that of the wake region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.948-955
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• 2005

A three-dimensional computation was conducted to understand effects of the inlet boundary layer thickness on the internal flow in a low-speed axial compressor operating at the design condition($\phi=85\%$) and near stall condition($\phi=65\%$). At the design condition, the flows in the axial compressor show, independent of the inlet boundary layer thickness, similar characteristics such as the pressure distribution, size of the hub comer-stall, tip leakage flow trajectory, limiting streamlines on the blade suction surface, etc. However, as the load is increased, the hub corner-stall grows to make a large separation region at the junction of the hub and suction surface for the inlet condition with thick boundary layers at the hub and casing. Moreover, the tip leakage flow is more vortical than that observed in case of the thin inlet boundary layer and has the critical point where the trajectory of the tip leakage flow is abruptly turned into the downstream. For the inlet condition with thin boundary layers, the hub corner-stall is diminished so it is indistinguishable from the wake. The tip leakage flow leans to the leading edge more than at the design condition but has no critical point. In addition to these, the severe reverse flow, induced by both boundary layer on the blade surface and the tip leakage flow, can be found to act as the blockage of flows near the casing, resulting in heavy loss.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.4 s.27
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• pp.267-272
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• 2006

Butterfly valves have been used for shut-off and throttling-control application in many industrial fields. Recently, they are frequently used for cooling water, oil system and ballast piping system of many larger vessels. They are especially suited for flow throttling control of heat exchangers in engine room. Measurement by the PIV(Particle Image Velocimetry) was conducted to investigate the flow characteristics of butterfly valve inserted within circular pipe. Flow behaviors such as instantaneous and time-mean velocity vectors are investigated. Furthermore, to reveal systematic performance of the butterfly valve, wall pressure was measured at 6 points along the pipe by digital manometer. As the valve position moves to the closed side, flow separation increases and persists its tendency downstream until smoothly uniform flow developed. The pressure loss is found to be about zero for the disk open angles less than 45 degrees, but is substantially increased for those larger than 60 degrees.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.5
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• pp.17-28
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• 2018

Cyclonic-dissolved air flotation(Cyclonic-DAF), an advanced form of pressure flotation, applies a structure that enables the forming of twirling flows. This in turn allows for suspended matter to adhere to microbubbles and float to the surface of a treatment tank during the process of intake water flowing through a float separation tank. This study conducted a lab-scale test and pursued geometrical modeling using computational fluid dynamics(CFD) to establish a pilot scale design. Based on the design parameters found through the above process, a pilot cyclonic-DAF system($10m^3/hr$) for removing algae was created. Upon developing the pilot-scale cyclonic-DAF system, a type of algae coagulant(R-119) was applied as the coagulant to the system for field testing through which the removal rates of chlorophyll-a and cyanobacteria were evaluated. The chlorophyll-a and harmful cyanobacteria of the raw water at region B, the field-test site, were found to be $177.9mg/m^3$ and 652,500cells/mL respectively. Treated waters applied with 60mg/L and 100mg/L of algae coagulant presented removal efficiencies of approximately 95% and 97%, respectively. The cyanobacteria cell number of the treated waters applied with 60mg/L and 100mg/L of algae coagulant both that were equal to or less than 1,000cells/mL and were below attention level criteria for the issuance of algae boundary.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.183-196
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• 2013

The purpose of this study is to process a seaweed resources that is easy to find in Korea and has outstanding phlogistone and high yield seaweed vinegar solution through mass-production and facility development for utilization. The compound uses wasted seaweeds, such as brown seaweed, kelp, seaweed fusiform, and laver, and carbonizes them in high temperature by drying in poly step trap to extract them. In also involves the development of a process that separates and refines the extracts to create a high value-added anti-bacterial bio solution that can replace chemicals in agriculture and industries and even chemical food additives. so, studied separation and refining of seaweed extracts to analyze the compounds. and processed and compared to seaweed vinegar extracts to prove superiority.