• Geophysics and Geophysical Exploration
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• 제14권3호
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• pp.249-253
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• 2011

Based on intrinsic and scattering quality factor ($Q_i^{-1}$ and$Q_s^{-1}$) obtained from the seismic data of the southeastern Korean Peninsula, the expected coda quality factor (${Q_{Cexp}}^{-1}$) was theoretically calculated using multiple scattering model, and was compared with other quality factors such as $Q_i^{-1}$, $Q_s^{-1}$, and observed $Q_C^{-1}$ obtained by single scattering model. While the ${Q_{Cexp}}^{-1}$ values are typically comparable to the $Q_i^{-1}$ values, the $Q_C^{-1}$ values are different from the ${Q_{Cexp}}^{-1}$ values except for the higher frequency. Future works require to consider depth-dependent attenuation.

• Journal of Energy Engineering
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• 제27권4호
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• pp.64-69
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• 2018

The purpose of this study is to expand the use of coal ash and coal slag in thermal power plants. In addition, controlled low strength materials was developed to prevent mine settlement. Bottom ash and KR slag are mixed at ratio of 7:3 to expand the use of industrial by-products through carbonate reaction and inhibit the exudation of heavy metals. In order to efficiently fill the abandon mine, workability and physical properties were evaluated according to flow. As a result of elution of harmful substance experiment, it was confirmed that the carbonation reaction inhibited the elution of heavy metals. It was confirmed that the difference in water ratio was the difference in specific surface area of the controlled low strength materials. It was confirmed that the working efficiency is excellent when the flowability is 300mm compared to 260mm. compressive strength measurement result was relatively high at 260mm compared to 300mm because the number of pores due to decrease of water ratio was small.

• Applied Chemistry for Engineering
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• 제30권4호
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• pp.504-508
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• 2019

The feasibility of replacing the tope cell of pn GaInP homojunction with our GaInP/AlGaInP heterojunction structure in III-V semiconductor multijunction photovoltaic (MJPV) cells having the highest current conversion efficiency was investigated. The performance of photovoltaic (PV) cells grown on $2^{\circ}$ and $10^{\circ}$ off-oriented GaAs substrates were compared to each other. The PV cells on the $10^{\circ}$ off-cut substrate showed higher short-circuit current density ($J_{sc}$) and conversion efficiency values than that of using the $2^{\circ}$ one. For $2{\times}2mm^2$ area PV cell on $10^{\circ}$ off substrate, the $J_{sc}$ of $9.21mA/cm^2$ and the open-circuit voltage of 1.38 V were measured under 1 sun illumination. For $5{\times}5mm^2$ cell on $10^{\circ}$ off substrate, the conversion efficiency was decreased from 6.03% (1 sun) to 5.28% (20 sun) due to a decrease in fiill factor (FF).

• Applied Chemistry
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• 제15권1호
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• pp.37-40
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• 2011

A chemiluminescent method with silver nanoparticles for determination of L-alanine has been presented. The chemilumiscence intensity was further enhanced by silver nanoparticles in the luminol system by its catalytic role. The silver nanoparticles enhanced chemiluminescent method is applicable for the determination of an amino acid such as alanine. When alanine was introduced to the luminol system with silver nanoparticles, chemiluminescence intensity was reduced with the concentration of the added alanine. The effects of pH, concentrations of luminol, hydrogen peroxide and silver nanoparticles on the chemiluminescence intensity were investigated. The calibration curve for L-alanine was linear over the range from 6.60×10^-8 M to 4.00×10^-7 M, coefficient of correlation was 0.996 and detection limit was 3.5×10^-9 M under the optimal conditions of 4.0×10^-3 M, 4.0×10^-2 M, 4.0×10^-4 M, 12.8 for the concentration of luminol, H₂O₂, silver nanoparticles and pH, respectively.

• Journal of the Korean earth science society
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• 제32권1호
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• pp.152-157
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• 2011

Lg amplitude decrease $Q^{-1}$ becomes very important when harzadous earthquakes occurred in neighbor nations such as Japan and China because the Lg phase is the largest seismic phase in Korea. The values of Lg $Q^{-1}$ are correlated with seismic activities from the RTSM for IRIS data with long pair distance of stations and events. The Japanese paths crossing the East Sea (Sea of Japan) show high $Q^{-1}$ values related with seismicity and oceanic crust. The paths of Shanghai having the moderate seismicity show the second highest values followed by the Japanese region, while the paths between Manchuria and the Korean Peninsula exhibit low values associated with the low seismicity of the regions.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.853-860
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• 2019

In order to meet more severe environmental regulations, oxy-fuel circulating fluidized bed(CFB) boilers or ultra supercritical CFB boilers, which are a kind of process in that solid particles moves similar to fluid, have been developed in the world. In CFB power generation processes, the method to reduce or remove sulfur dioxide is in-situ desulfurization reaction via limestone directly injected into CFB boilers. However, the desulfurization efficiencies have continuously changed because limestones injected into CFB boilers are affected by various operation conditions (Bed temperature, pressure, solid circulating rate, solid holdup, residence time, and so on). In this study, a prediction method with physical and chemical properties of limestone and operation conditions of CFB boiler for in-situ desulfurization reaction in CFB boilers has developed by integrating desulfurization kinetic equations and hydrodynamics equations for CFB previously published. In particular, the prediction equation for in-situ desulfurization was modified by using experimental results from desulfurization reactions of various domestic limestones.

• Korean Journal of Remote Sensing
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• 제34권6_2호
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• pp.1155-1163
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• 2018

Recently, much attention has been focused on the change and role of the Arctic region due to climate change. Studies using various platforms are being conducted in the polar regions. Among them, monitoring of Arctic cryosphere information using remote sensing is the most important observational role of various scientific activities. This special issue introduces several studies on polar exploration monitoring in polar research. We hope that this special issue contributes to the sharing of information on the role of polar exploration in remote areas, as well as the identification of the current status of domestic polar exploration and remote environmental exploration. We are also looking forward to the efforts of Korean remote sensing experts to find out the persistent polar exploration field and to increase national support.

• Geophysics and Geophysical Exploration
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• 제11권3호
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• pp.250-262
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• 2008

In order to assess the feasibility of the dipole-dipole electric method to the investigation of metallic ore deposit, both field data simulation and inversion are carried out for several simplified ore deposit models. Our interest is in a vein-type model, because most of the ore deposits (more than 70%) exist in a vein type in Korea. Based on the fact that the width of the vein-type ore deposits ranges from tens of centimeters to 2m, we change the width and the material property of the vein, and we use 40m-electrode spacing for our test. For the vein-type model with too small width, the low resistivity zone is not detected, even though the resistivity of the vein amounts to 1/300 of that of the surrounding rock. Considering a wide electrode interval and cell size used in the inversion, it is natural that the size of the low resistivity zone is overestimated. We also perform field data simulation and inversion for a vein-type model with surrounding hydrothermal alteration zones, which is a typical structure in an epithermal ore deposits. In the model, the material properties are assumed on the basis of resistivity values directly observed in a mine originated from an epithermal ore deposits. From this simulation, we can also note that the high resistivity value of the vein does not affect the results when the width of the vein is narrow. This indicates that our main target should be surrounding hydrothermal alteration zones rather than veins in field survey. From these results, we can summarize that when the vein is placed at the deep part and the difference of resistivity values between the vein and the surrounding rock is not large enough, we cannot detect low resistivity zone and interpret the subsurface structures incorrectly using the electric method performed at the surface. Although this work is a little simple, it can be used as references for field survey design and field data Interpretation. If we perform field data simulation and inversion for a number of models and provide some references, they will be helpful in real field survey and interpretation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제11권5호
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• pp.190-196
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• 2001

Alunite was dehydrated at 500~$580^{\circ}C$ and desulfurued at 580~$780^{\circ}C$ in air atmosphere. Therefore, this study was carried out to investigate the formation conditions of anhydrite ($CaCO_4$) when the mixtures of alunite TEX>$[K_2SO_4$.$Al_2(SO_4)_3$.$4Al(OH)_3$] and limestone ($CaCO_3$)were roasted. Alunite scarcely dected the partial pressures of $CO_2$(g), but limestone was bansformed into CaO at $650^{\circ}C$ in air and $900^{\circ}C$ in saturated $CO_2$(g), atmosphere, respectively. When the the mixtures of 1 mol of alunite and 6 rnol of limestone were roasted for 2 hours at lO00C in air and saturated $CO_2$(g), anhydrite was formed at $550^{\circ}C$ calciumlangbeinite, at $700^{\circ}C$and haiiyne, at 800~$950^{\circ}C$. The formation rate of anhydrite in air and saturated $CO_2$(g), was 99.0 % and 95.0 %, respectively. then the formation rate of anhydrite was not changed in air atmosphere but increased according to the decreasing of the particle size of limestone in saturated $CO_2$(g). Therefore, when the mixture of 1 mol of alunite and 6 rnol of limestone were roasted, the clinker composed of lmol of haiiync and 1 mol of calciumlangbeiilte can be manufactured

• Korean Journal of Remote Sensing
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• 제35권3호
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• pp.457-470
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• 2019

Automatic Target Recognition (ATR) using Synthetic Aperture Radar (SAR) has been attracted attention in the fields of surveillance, reconnaissance, and national security due to its advantage of all-weather and day-and-night imaging capabilities. However, there have been some difficulties in automatically identifying targets in real situation due to various observational and environmental conditions. In this paper, ATR problems in Extended Operating Conditions (EOC) were investigated. In particular, we considered partial occlusions of the target (10% to 50%) and differences in the depression angle between training ($17^{\circ}$) and test data ($30^{\circ}$ and $45^{\circ}$). To simulate various occlusion conditions, SARBake algorithm was applied to Moving and Stationary Target Acquisition and Recognition (MSTAR) images. The ATR accuracies were evaluated by using the template matching and Adaboost algorithms. Experimental results on the depression angle showed that the target identification rate of the two algorithms decreased by more than 30% from the depression angle of $45^{\circ}$ to $30^{\circ}$. The accuracy of template matching was about 75.88% while Adaboost showed better results with an accuracy of about 86.80%. In the case of partial occlusion, the accuracy of template matching decreased significantly even in the slight occlusion (from 95.77% under no occlusion to 52.69% under 10% occlusion). The Adaboost algorithm showed better performance with an accuracy of 85.16% in no occlusion condition and 68.48% in 10% occlusion condition. Even in the 50% occlusion condition, the Adaboost provided an accuracy of 52.48%, which was much higher than the template matching (less than 30% under 50% occlusion).