• 한국지하수토양환경학회지:지하수토양환경
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• 제20권6호
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• pp.95-102
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• 2015

The purpose of this study is to compare the degradation characteristics by subcritical water of RDX contaminated soil using batch mode and dynamic mode devices. First, upon application of RDX contaminated soil, RDX treatment efficiency was increased with increasing the temperature in both modes. At 150℃, the treatment efficiency was 99.9%. RDX degradation efficiency got higher with lower ratio of solid to liquid. However, the treatment efficiency in the dynamic mode tended to be decreased at a certain ratio of solid to liquid or lower. The treatment efficiency was increased when it took longer time for the reactions in both modes. As the results of analysis on concentration of treated water after subcritical water degradation, the RDX recovery rate of dynamic and batch modes at 150℃ was 10.5% and 1.5%, respectively. However, both modes showed very similar recovery rates at 175℃ or higher. RDX degradation products were analyzed in treated water after it was treated with subcritical water. According to the results, RDX degradation mechanism was mostly oxidation reaction and reduction reaction was partially involved. Therefore, it suggested that most of RDX in soil was degraded by oxidation of subcritical water upon extraction. According to this result, it was found that both batch and dynamic modes were very effectively applied in the treatment of explosive contaminated soil.

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.41-51
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• 2012

Heliostat field is the most important subsystem in the tower type solar thermal power plant since its optical performance affects the total system efficiency most significantly while the construction cost of it is the major part of total construction cost in such a power plant. Thus a well designed heliostat field to maximize the optical efficiency as well as to minimize the land usage is very important. This work presents methodology, procedures and result of heliostat filed design for 200kW solar thermal power plant built recently in Daegu, Korea. A $2{\times}2(m)$ rectangular shaped receiver located at 43(m) high and tilted $28^{\circ}$ toward heliostat field, 450 of heliostats of which the reflective surface is formed by 4 of $1{\times}1(m)$ flat plate mirror facet, and the land area having about $140{\times}120(m)$ size are used to form the heliostat field. A procedure to deploy 450 heliostats in radial staggered nonblocking formation is developed. Also the procedures to compute the cosine effect, intercept ratio, blocking and shading ratio in the field are developed. Finally the heliostat filed is designed by finding the optimal radial distance and azimuthal spacing in radial staggered nonblocking formation such that the designed heliostat field optical efficiency could be maximized. The designed heliostat field has 77% of annual average optical efficiency, which is obtained by annually averaging the optical efficiencies computed between the time of where sun elevation angle becomes $10^{\circ}$ after sunrise and the time of where sun elevation angle becomes $10^{\circ}$ before sunset in each day.

• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.323-330
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• 2017

Ash remaining after coal combustion was used as a catalyst support for tar steam reforming with various proportions of $Al_2O_3$ added for higher reforming efficiency. At a constant Ni content of 12 wt%, a coal ash and $Al_2O_3$ were mixed at a ratio of 5:5, 7:3, 9:1. As a result, the catalytic activity for toluene steam reforming was improved by adding $Al_2O_3$ at $500-600^{\circ}C$. The catalysts with ratio 7:3 and 5:5 reached toluene conversion of 100% above $700^{\circ}C$. When comparing the catalysts in which the coal ash and $Al_2O_3$ mixed at a ratio of 5:5 and 7:3 with the Ni/Al catalyst, it was concluded that this coal ash catalyst has efficient catalytic performance.

• 한국농공학회논문집
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• 제48권3호
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• pp.85-94
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• 2006

Practially useful method of steel fiber for construction work is presented in this study. The most important purpose of this study is to develop a model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus, and splitting strength were performed with self-made cylindrical specimens of variable aspect ratios and volume fractions. The experiment showed that compressive strength was not in direct proportion to volume fraction which doesn't seem to have great influence over compressive strength. However, splitting strength showed almost direct proportion to aspect ratio and volume fraction. Improvement of optimal efficiency was confirmed when the aspect ratio was 70. Experiments on flexural strength, fracture energy, and characteristic length were carried out with self-manufactured beams with notch. As a result, increases of flexural strength, fracture energy, and characteristic length according to increase of volume fraction tend to be prominent when aspect ratio is 70. The steel fiber improves concrete to be more ductile and tough. Moreover, regression analysis was the performed and predictable model was developed after determining variables. With comparison and analysis of suggested estimated values and measured data, reliance of the model was verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1666-1668
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• 1997

This paper reports the optimal gas mixing ratio for color plasma display panel to improve luminous efficiency using gas dischage simulation which contains energy equation. We verified a simulation by measuring vacuum ultraviolet. The luminous efficiency has improved considerably(about 30%) by adding Ar (0.5%), compared with Ne-Xe(4%) mixing gas.

• Current Applied Physics
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• 제18권12호
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• pp.1571-1576
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• 2018

Recent study shows that the main reason for limiting CZTS device performance lies in the low open circuit voltage, and crucial factor that could affect the $V_{oc}$ is secondary phases like ZnS existing in absorber layer and its interfaces. In this work, the $Cu_2ZnSnS_4$ thin film solar cells were prepared by sputtering CuSn and CuZn alloy targets. Through tuning the Zn/Sn ratios of the CZTS thin films, the crystal structure, morphology, chemical composition and phase purity of CZTS thin films were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Raman spectroscopy. The statistics data show that the CZTS solar cell with a ratio of Zn/Sn = 1.2 have the best power convention efficiency of 5.07%. After HCl etching process, the CZTS thin film solar cell with the highest efficiency 5.41% was obtained, which demonstrated that CZTS film solar cells with high efficiency could be developed by sputtering CuSn and CuZn alloy targets.

• 대한임베디드공학회논문지
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• 제9권1호
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• pp.17-24
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• 2014

In this paper, we implement and evaluate the performance of a vector-based rasterization algorithm for 3D graphics by using a SIMD (single instruction multiple data) many-core processor architecture. In addition, we evaluate the impact of a data-per-processing elements (DPE) ratio that is defined as the amount of data directly mapped to each processing element (PE) within many-core in terms of performance, energy efficiency, and area efficiency. For the experiment, we utilize seven different PE configurations by varying the DPE ratio (or the number PEs), which are implemented in the same 130 nm CMOS technology with a 500 MHz clock frequency. Experimental results indicate that the optimal PE configuration is achieved as the DPE ratio is in the range from 16,384 to 256 (or the number of PEs is in the range from 16 and 1,024), which meets the requirements of mobile devices in terms of the optimal performance and efficiency.

• Asian-Australasian Journal of Animal Sciences
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• 제16권9호
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• pp.1355-1359
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• 2003

This study examined the replacement of the fish meal (FM) with commercial poultry by-product meal (PBM) in practical diets for rainbow trout (Onchorynchus mykiss, Walbaum). Five isocaloric and isonitrogenous diets containing levels 0 (control), 10, 20, 30 and 40% of PBM as a replacement for FM were fed to three replicate groups of rainbow trout with a initial weight $34.50{\pm}0.43g$ (mean${\pm}$SE). Protein efficiency ratio (PER) of diets containing PBM up to 20% were similar to the control while significantly lower values were obtained from the groups receiving higher levels of PBM (p<0.05). Apparent protein digestibility coefficients (ADCs) were significantly lower than that of the control group when PBM was included at level of 20% or more. Similarly, significantly lower values were observed with diets containing 30 and 40% PBM in terms of dry matter, organic matter, ether extract, ash and energy digestibility (p<0.05). Dietary treatments did not significantly affect the body composition of the fish in terms of dry matter, crude protein, ether extract and ash. In conclusion, PBM in a proportion of 20% may replace about 40 % of FM in rainbow trout diet without significant impairment grow.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.749-758
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• 2011

The present work explores the performance and operation limit of electrodialysis cell for HI concentration in sulfur iodine thermochemical hydrogen production process, For this purpose, the electrodialysis cell was assembled with Nafion 117 as a PEM membrane and two activated carbon papers as the electrodes. HIx solution was prepared with composition of HI: $I_2$: $H_2O$ = 1: 0.5~2.5: 5.2 in molar ratio. The cell and its peripheral apparatus were placed in the specially designed convective oven in order to uniformly maintain the operation temperature. As operation temperature increased, the amount of water transport from anode to cathode increased, thus reducing HI molarity in catholyte. Meanwhile, the current efficiency was constant as about 90 %, irrespective of temperature change. The cell voltage increased with initial $I_2$ mole ratio as well as anolyte to catholyte mole ratio. Moreover the cell voltage overshot took place within 10 h cell operation, which is due to the $I_2$ precipitation inside the cell. From the analysis of $I_2$ mole ratio in the anolyte, it is noted that operation limit (in $I_2$ mole ratio) of the electrodialysis cell, arising from was measured to be 3.2, which is much lower than bulk solubility limit of 4.7.

• Korean Chemical Engineering Research
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• 제47권5호
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• pp.580-586
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• 2009

본 연구에서는 2 MWe 규모 순환유동층 발전소에서 중국산 유연탄과 북한산 무연탄의 혼합연소특성을 실험적으로 고찰하였다. 중국유연탄과 호주유연탄을 과잉공기량과 층온도 등을 변수로 실험한 결과, 연소효율은 석탄입자의 입도와 석탄중의 휘발분의 영향을 받으며, 이 때 미연탄소분은 Fly ash 5~7%, 바닥회 0.3% 수준으로 중국 유연탄의 연소효율은 99.5% 이상을 보였다. 북한산 무연탄과 유연탄의 혼소시 혼합비 20%에서 무연탄의 평균입도가 작아 연소실에서 비산되는 입자로 인해 연소효율은 5% 이상 저하되었다, 그러나 $SO_2$와 NOx의 배출농도는 크게 변화하지 않았다. 배출되는 대기오염물질의 농도는 $NO_x$ 200~250 ppm($O_2$ 6%), $SO_2$ 100~320 ppm($O_2$ 6%)이었다. SCR 공정에서 2~13 l/min 범위의 $NH_3$ 공급으로 30~65%의 $NO_x$가 저감되었다. Limestone을 이용한 노내탈황에서 약 Ca/S 몰비 6.5를 공급했을 때 $SO_2$가 75% 제거되었고, $Mg(OH)_2$를 흡수제로 하는 FGD를 운전했을 때 pH 5.0 이상에서 100% 탈황효과를 보였다.