• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.59-66
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• 2005

The main purpose of this paper is to describe a highly efficient common mid-point (CMP) data acquisition method for ground-penetrating radar (GPR) surveying, which is intended to widen the application of GPR. The most important innovation to increase the efficiency of CMP data acquisition is continuous monitoring of the GPR antenna positions, using a real-time kinematic Global Positioning System (RTK-GPS). Survey time efficiency is improved because the automatic antenna locating system that we propose frees us from the most time-consuming process-deployment of the antenna at specified positions. Numerical experiments predicted that the data density and the CMP fold would be increased by the increased efficiency of data acquisition, which results in improved signal-to-noise ratios in the resulting data. A field experiment confirmed this hypothesis. The proposed method makes GPR surveys using CMP method more practical and popular. Furthermore, the method has the potential to supply detailed groundwater information. This is because we can convert the spatially dense dielectric constant distribution, obtained by using the CMP method we describe, into a dense physical value distribution that is closely related to such groundwater properties as water saturation.

• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.45-53
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• 2009

This study concerned remediation of heavy metal contaminated farmland soils near abandoned mine, using stabilization method, with particular emphasis on the remediating the soils contaminated with multi-elements. In this study, stabilizing heavy metals based on 'In-situ chemical fixation' has been applied to the soil collected from an abandoned mine in Korea, using column test, with various stabilizing agents, including $FeSO_4$, $KMnO_4$, sludge (collected from coal mine drainage treatment pond), zero-valent iron (ZVI), zeolite and $CaCO_3$. Sixty five-days operation of the flow-through columns yield $FeSO_4\;+\;KMnO_4$ and zeolite are efficient on reducing As leaching from the soil. ZVI and sludge are reducing the leaching of Cu. Although $FeSO_4\;+\;KMnO_4$ seem to be efficient for most heavy metals, high pH in the initial stage of test enabled high leaching of the heavy metals, whereas fixation of the heavy metals maintain throughout the rest of the test period, with increasing pH up to around 6. Addition of some alkaline agent may inhibit the low pH during the application. The column test was also run as two set: one set incubated with deionized water for 72 hours prior to starting the test, and the other without incubation. The incubated set demonstrated better stabilizing efficiency, indicating the potential optimized operation method.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.327-333
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• 2008

In general, a lens with large NA makes image quality better. There are many kinds of cheap concave mirrors with large aperture and NA. This paper presents a method that uses a large aperture projection imaging system to enhance the image used for 3D shape measurement. This method makes it possible to enhance reflection uniformity on the object surface and increases SNR (Signal to Noise Ratio). Using a large aperture lens, it is possible to obtain a brighter image, reducing the shading nature in the image boundary, and enhancing the reflection uniformity even on woven surfaces. Because of the exorbitant cost of a large aperture projection lens larger than 150 mm in diameter, a refractive lens was exchanged with a concave mirror resulting in the same optical effect. In experiment, changing NA $0.15{\sim}0.8$, image contrast was enhanced from 46 to 1.33. Incidentally, the effect of the concave mirror was tested successfully through the experiment.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.4
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• pp.115-118
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• 1981

Effect of water potential of culture solution on photosynthesis, transpiration and water uptake was investigated using polyethylene glycol 6000. 1. Even at -0.5 bar of culture solution phothosynthesis was decreased by 20% within 1 hour. Plant in control showed 3.26% loss of initial water for 13 hours suggesting very sensitive in water uptake. 2. Relation between water potential of culture solution (${\psi}$) and water uptake amount (W) 2-year root was ${\psi}=-2.890/e^{2.796W}$ indicating that permanent wilting point will be greater than -2.89 bar. 3. Transpiration considerably decreased with the decrease of water potential and thus by 23.9% at -0.5 bar after 4 hours. 4. From the above results ginseng plant appears to have high root water potential at permanent wilting point and thus very week to water stress due to drought or high salt content in soils.

• The Korean Journal of Soil Zoology
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• v.4 no.2
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• pp.81-85
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• 1999

Efficiencies of hand sorting, vermifuge application and combined methods of them for sampling earthworms in the field were compared. 1) hand sorting : sampling unit of soil (50 cm${\times}$50 cm${\times}$30 cm, width${\times}$length${\times}$depth) was dug out and earthworms were sorted by hands. 2) Vermifuge application : Solution of mustard, pepper or formalin was treated onto the soil surface of smpling unit (50 cm${\times}$50 cm, width${\times}$length). 3) Combined method : In a sampling unit of soil (50 cm${\times}$50 cm${\times}$30 cm, width${\times}$length), hand sorting was carried out into the depth of 10 cm or 15 cm and then vermifuge was treated. Earthworms were collected more in numbers by hand sorting than vermifuge application although it was much more time-consuming and labor intensive. Efficiency of mustard to extract earthworms was as same as formalin but much better than that of pepper. Combined method of hand sorting with mustard treatment was more efficient than vermifuge applications and other combined methods. And it could collect earthworms as many as hand sorting, but was much less time-consuming and labor-intensive than hand sorting. Thus combined method of hand sorting (to the depth of 15 cm) with mustard treatment could be recommended for the sampling of earthworms in the field.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.846-855
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• 2021

Eco-friendly and renewable energy sources are actively being researched in recent times, and of shore wind power generation requires advanced design technologies in terms of increasing the capacities of wind turbines and enlarging wind turbine installation vessels (WTIVs). The WTIV ensures that the hull is situated at a height that is not affected by waves. The most important part of the WTIV is the leg structure, which must respond dynamically according to the wave, current, and wind loads. In particular, the wave load is composed of irregular waves, and it is important to know the exact dynamic response. The dynamic response analysis uses a single degree of freedom (SDOF) method, which is a simplified approach, but it is limited owing to the consideration of random waves. Therefore, in industrial practice, the time-domain analysis of random waves is based on the multi degree of freedom (MDOF) method. Although the MDOF method provides high-precision results, its data convergence is sensitive and difficult to apply owing to design complexity. Therefore, a dynamic amplification factor (DAF) estimation formula is developed in this study to express the dynamic response characteristics of random waves through time-domain analysis based on different variables. It is confirmed that the calculation time can be shortened and accuracy enhanced compared to existing MDOF methods. The developed formula will be used in the initial design of WTIVs and similar structures.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.5
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• pp.438-443
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• 2021

This paper uses a multiplex deposition sputter system and aims to improve transmittance and reduce production costs by depositing a CdS thin film on an ITO glass substrate. When manufacturing CdS thin films, we wanted to find excellent conditions when manufacturing solar cells by changing heat treatment time. It was observed that thickness and sheet resistance were not significantly different depending on heat treatment time changes. The specific resistance was measured from a minimum of 6.68 to a maximum of 6.98. When the heat treatment time was more than 20 minutes, the transmittance was measured to be more than 75%. When the heat treatment time was 10 minutes, the bandgap was 3.665 eV and more than 20 minutes was 3.713 eV, which was measured as the same result. The XRD analysis showed that the structure of CdS was hexagonal and only CdS thin films were deposited without any other impurities. The result of calculating the FWHM was a maximum of 0.142 when the heat treatment time was 20 minutes, and a minimum of 0.133 when the heat treatment time was 40 minutes, so there was no significant difference in the FWHM when the heat treatment time was changed. The particle size was measured at 11.65 Å when the heat treatment time was 40 minutes, and at 10.93 Å when the heat treatment time was 20 minutes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.675-682
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• 2021

Fire accidents on land and at sea can cause serious casualties; specifically, owing to the nature of marine plants and ships, the mortality rate at sea from suffocation in confined spaces is significantly higher than that on land. To prevent such cases of asphyxiation, it is essential to install ventilation fans that can outwardly direct these toxic gases from fires; however, considering the scale of marine fires, the installation of large ventilation fans is not easy owing to the nature of marine structures. Therefore, in this study, we developed a new concept for fire safety technology to control toxic gases generated by fires from applied direct current (DC) electric fields. In the event of a fire, most flames contain large numbers of positive and negative charges from chemi-ionization, which generates an "ionic wind" by Lorentz forces through the applied electric fields. Using these ionic winds, an experimental study was performed to artificially control the fire smoke caused by burning paper and styrofoam, which are commonly used as insulation materials in general buildings and ships. The experiments showed that a fire smoke could be artificially controlled by applying a DC voltage in excess of ±5 kV and that relatively effective control was possible by applying a negative voltage rather than a positive voltage.

• Journal of Conservation Science
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• v.37 no.5
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• pp.590-605
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• 2021

The history of printing technology in Korea is studied by investigating existing ancient documents and records and comparing accumulated data and knowledge. Cultural property research requires non-destructive testing and observation with the naked eye or aided by a microscope. Researchers' experience and knowledge are required even though they cannot guarantee the outcome. For ancient documents and records that are presumed to consist of woodblock printing, wood type printing, metal type printing, or their combinations, each researcher draws various opinions and conclusions. This often causes confusion and divides the opinions of ordinary citizens and field specialists. Among them, the criteria for judging ancient documents or books printed using woodblock and metal movable material are ambiguous. Academic research on the development history of printing technology in ancient Korea has been stagnant, and conflicts among researchers have also erupted. Involvement of national investigative agencies not specialized in cultural properties has exacerbated the situation. In this study, we investigated printing characteristics that are likely to serve as more objective judgment criteria by quantitatively analyzing the experiments of retrieving several sheets of Korean paper (Hanji) using a replicated Hunminjeongeum (訓民正音) woodblock and quantitatively analyzing the images of the printed papers. In addition, the validity and questions for the typical phenomena presented as a method for distinguishing between woodblock and metal print are reviewed. We investigated the possibility of developing new objective judgement criteria through quantitative analysis using image analysis and investigating the printing characteristics of Korean paper through a reproduction experiment of woodblock printing.

• Composites Research
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• v.34 no.5
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• pp.317-322
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• 2021

When a complex load such as torsion, low-speed impact, or fatigue load is applied, the properties in the thickness direction are weakened through microcracks inside the material due to the nature of the laminated composite material, and delamination occurs. To prevent the interlaminar delamination, various three-dimensional reinforcement methods such as Z-pinning and stitching, and structural health monitoring techniques that detect the microcrack of structures in real time have been continuously studied. In this paper, the single-lap joints with I-fiber stitching process were manufactured by a co-curing method and their strengths and failure detection capability were evaluated. AE and electric resistance method were used for detection of crack and failure signal and electric circuit for signal analysis was manufactured, and failure signal was analyzed during the tensile test of a single-lap joint. From the experiment, the strength of the single lap joint reinforced by I-fiber stitching process was improved by about 44.6% compared to the co-cured single lap joint without reinforcement. In addition, as the single-lap joint reinforced by I-fiber stitching process can detect failure in both the electrical resistance method and the AE method, it has been proven to be an effective structure for failure monitoring as well as strength improvement.