• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.542-547
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• 2017

This paper was to analyze the membrane characterization of hydrophilicity, surface morphology and membrane chemical anlysis of three commercial microfiltration/ultrafiltration membranes, and evaluate the filtration performance of a seawater to assess the availability for pretreatment of desalination process. From the results of contact angle, Mem-3, fabricated with polyacrylonitrile, was highly hydrophilic. It find out that Mem-3 has more anti-biofouling property. In Field emission scanning electron microscope (FESEM), Mem-1 (polyethylene) and Mem-2 (Polyvinylidenefluoride) showed the sponge-like shape and Mem-3 showed finger-like shape. Membrane chemical analysis by energy dispersive spectrometer (EDS) presented that Mem-2 was mostly fluoride and Mem-3 had s high ratio of N (32.47%) due to the nitrile group. The permeation flowrate per time on suction pressures using deionized water (D.I. water) tends that permeation rate of Mem-3 more increased when the pressure was increased compared to other membranes. From the results of turbidity and total suspended solids (TSS) removal, turbidity of permeate was 0.191 NTU to 0.406 NTU and TSS was 2.2 mg/L to 3.0 mg/L in all membranes, indicating that it was not suitable for the pretreatment of seawater desalination by short-term experiments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.239-245
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• 2009

Levees, the hydro-engineering structure, are similar to earth dams in aspects of shape and structure. However, they are different from earth dams in the external force conditions. As a levee is the structure that is complexly affected by the flow and the water stage in the river, it may be unreasonable to analyze the seepage safety as previous studies derived from the neglect of river flow. In this study, an experiment was conducted to investigate flow structures in a trapezoidal open-channel and the influence of the channel flow on the seepage through a levee. Flow structures in a trapezoidal open-channel were distinguished from a rectangular open-channel such as velocity and bottom shear stress distributions. In case with the flow velocity of 0.5 m/s, seepage water heads were higher 10 percent as compared with the stagnant case. This result is caused by dynamic heads, secondary currents, turbulent fluctuation forces, and various physical factors. It is suggested that external force boundary considered in terms of the flow as well as the water stage is proper to seepage analyses.

• Journal of the Korean GEO-environmental Society
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• v.17 no.11
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• pp.45-53
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• 2016

A precast panel wall system resists against the horizontal earth pressure by increasing the shear strength of ground by reinforcement connected to the panel. The application of precast panel wall system is growing to lately minimize the earth work and environmental damage caused by large cut slope and to use the limited land effectively. The ground adhered panel wall system is the construction method that has the panel engraved with natural rock shape to improve the landscape. This system is developed to complete Top-Down method, and it is possible to have vertical cut, and to adhere to in-situ ground, improve construction ability by minimizing the ground relaxation and exclusion the trench and backfill process. In this study the field tests were performed to verify the construction ability about the vertical cut and complete Top-Down process and the construction behavior of ground adhered panel wall system was analyzed by large scale loading test and measurement results during loading test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.203-209
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• 2006

SAR (Synthetic Aperture Radar) technology, which is not influenced by cloud cover because of using electromagnetic wave of long wavelength, has an advantage in mapping the earth. NASA, recognizing these strong points of SAR, launched SRTM (Shuttle Radar Topography Mission), and acquired the topographic information of the earth. SRTM and NED (National Elevation Data) of USGS were used for the research and vegetation height map was produced through differentiating the two data. Correlation between SRTM-NED and planting year was analyzed to see the relationship. Strong correlation was detected and it shows the feasibility of estimating timber age and eventually creating timber age map from SRTM-NED. Additional analyses were conducted to check if the linearity is influenced by regional characteristics and forest uniformity. As results, the correlation between SRTM-NED and timber age is influenced by roughness of the terrain. Overall, this paper shows that timber age estimation using SRTM and NED can be sufficiently practical.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.197-205
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• 2008

Total displacement under non-reinforcement is a quantitative index of rock mass behavior during tunnel excavation and depends widely upon geological characteristics. The primary purpose of this study is to suggest a rock mass evaluation method, well representing tunnel behavior during excavation, according to rock type. A 3-D numerical analysis was carried out, with consideration of the shape of tunnel section, excavation condition and so forth, in a sedimentary rock-based tunnel, and total displacements under non-reinforcement according to rock mass class were calculated. Finally, quantification analysis was carried out to assess correlation of the total displacement with RMR parameters. As the result, a modified RMR system fer quantification of rock mass behavior during tunnel excavation is suggested.

• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.77-84
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• 2012

Anatase, one of the $TiO_2$ polymorphs, is known to show different phase transition paths depending on its crystalline and shape. Particle size of 15~25 nm anatase has been subjected to high-pressure Raman spectroscopy and X-ray diffraction studies using a diamond anvil cell. We observe that the starting sample transforms to an amorphous phase above approx. 20 GPa, which is retained upon pressure release to ambient condition. This is in contrast to previously established transition to baddeleyite phase and we suspect difference in the particle distribution state trigger phase instability of nanoparticles and hence amorphization.

• Korean Journal of Remote Sensing
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• v.31 no.6
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• pp.531-548
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• 2015

Atmospheric Motion Vector (AMV) from satellite images have shown Slow Speed Bias (SSB) in comparison with rawinsonde. The causes of SSB are originated from tracking, selection, and height assignment error, which is known to be the leading error. However, recent works have shown that height assignment error cannot be fully explained the cause of SSB. This paper attempts a new approach to examine the possibility of SSB reduction of COMS AMV by using a new target tracking algorithm. Tracking error can be caused by averaging of various wind patterns within a target and changing of cloud shape in searching process over time. To overcome this problem, Gaussian Mixture Model (GMM) has been adopted to extract the coldest cluster as target since the shape of such target is less subject to transformation. Then, an image filtering scheme is applied to weigh more on the selected coldest pixels than the other, which makes it easy to track the target. When AMV derived from our algorithm with sum of squared distance method and current COMS are compared with rawindsonde, our products show noticeable improvement over COMS products in mean wind speed by an increase of $2.7ms^{-1}$ and SSB reduction by 29%. However, the statistics regarding the bias show negative impact for mid/low level with our algorithm, and the number of vectors are reduced by 40% relative to COMS. Therefore, further study is required to improve accuracy for mid/low level winds and increase the number of AMV vectors.

• Journal of Adhesion and Interface
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• v.24 no.4
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• pp.136-142
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• 2023

In this study, TEOS was used as a silica source, and a triblock copolymer (P123) was used as a template to produce mesoporous silica with a well-ordered hexagonal mesopore array through a self-assembly method and hydrothermal process under acidic condition. (Surfactant-extracted SBA-15). Surfactant-extracted SBA-15 showed the particle shape of a short rod with a size of approximately 980 nm. The surface area and pore diameter were 730 m²g^-1 and 70.8 Å, respectively. Meanwhile, aminosilane (3-aminopropyltriethoxysilane, APTES) was grafted into the mesopores using a post-synthesis method. Mesoporous silica (APTES-SBA-15) modified with aminosilane had a well-ordered pore structure (p6mm) and well-maintained the particle shape of short rods. The surface area and pore diameter of APTES-SBA-15 decreased to 350 m²g^-1 and 60.7 Å, respectively. APTES-modified mesoporous silica was treated with a solution of rare earth metal ions (Eu³⁺, Tb³⁺) to synthesize a mesoporous silica material in which rare earth metal complexes were introduced into the mesopores. (Eu/APTES-SBA-15, Tb/APTES-SBA-15) These materials exhibited characteristic photoluminescence spectra by λ_ex=250 nm. (⁵D₄→⁷F₅ (543.5 nm), ⁵D₄→⁷F₄ (583.5 nm), ⁵D₄→⁷F₃ (620.2 nm) transitions for Tb/APTES-SBA-15; ⁵D₀→⁷F₀ (577.7 nm), ⁵D₀→⁷F₁ (592.0 nm), ⁵D₀→⁷F₂ (614.9 nm), ⁵D₀→⁷F₃ (650.3 nm) and ⁵D₀→⁷F₄ (698.5 nm) transitions for Eu/APTES-SBA-15)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.345-357
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• 2011

Recently, as part of diversifying energy sources and earth environmental issues, technology development of new renewable energy using wave energy is actively promoted and commercialized around Europe and Japan etc. In particular, OWC(Oscillating Water Column) wave power generation system using air flow induced by vertical movement of the water surface by waves in an air-chamber within caisson is known as the most efficient wave energy absorption device and therefore, is one of the wave power generation apparatus the closest to commercialization. This study examines air flow velocity, which operates turbine(Wells turbine) directly in oscillating water column type wave power generation structure from two-and three-dimensional numerical experiments and discusses optimal shape of oscillating water column type wave power generation structure by estimating the maximum flow rate of air according to change in shape. The three-dimensional numerical wave flume was applied in interpretation for this study which is the model for the immiscible two-phase flow based on the Navier-Stokes Equation. From this, it turned out that size of optimal shape appears differently according to the incident wave period and air flow is maximized at the period where minimum reflection ratio occurs.

• Journal of Korean Elementary Science Education
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• v.17 no.2
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• pp.79-90
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• 1998

The purpose of this study is to investigate degree of the concept formation on cell in elementary school teachers and to clarify the patterns of their misconceptions. Data were collected by interview with 120 elementary school teachers, ranged from twenties to fifties in age, working in Taegu city. The instrument was developed by researchers and was categorized into four: cell as the basic units of life, morphology of cell, function of cell, growth of individual from the viewpoint of cell. The results are as follows: First, about 80% of teachers had two perspective outcome of cell: Cells are the basic units of life on earth. But the potato and meat, which we used to eat as food, are not constructed of cells but aggregated of nutrients. Second, most of elementary school teachers recognized that shapes of the cell in organisms were diverse, but some of them only could present several kinds of shape on cell. The 35% of teachers had misconception that shape of cell is all the same in a individual. It shows that this result is caused by lack of opportunity to observe the various kinds of cells. Third, most teachers understood tell can be seen only through a microscope. Yet in comparison with relative size, it was revealed that misconception of cell size was induced by the term of 'basic unit'. In addition, they thought that large organisms are built from large cells, and small organisms from small cells. Fourth, Elementary school teachers used to confuse the terms between chloroplast and chlorophyll, and believed that the genetic material was contained only in the reproductive cells and seeds. It was also revealed that they thought the nutrients such as starch and fat are located at intercellular space. Fifth, the 60% of teachers conceived correctly that growth of individual depends on mitosis and increase in cell number. The rest of them, however, misunderstood that it is due to the increase of tell volume.