• Proceedings of the Membrane Society of Korea Conference
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• 1996.09a
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• pp.94-104
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• 1996

막형 정수기에 있어서 정수능력은 입증되었으나 다각적인 성능평가 결과는 없었다. 그러나 MAC 21 Project는 여러가지 막을 사용한 매우 다양한 실험조건에 대한 결과이므로 이것이 음용수처리에 대한 UF/MF막의 유효성을 증명하는 것으로 판단되어 자세히 기술하고자 한다.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.268-276
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• 2005

• Education of Primary School Mathematics
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• v.1 no.1
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• pp.45-58
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• 1997

초등학교 아동은 교육과정을 이수하면서 수 영역에서 자연수, 정수, 그리고 양의 유리수까지 학습하게 되어 있다(교육부, 1992). 초등학교에서의 유리수는 분수ㆍ소수를 의미하는 소박한 의미의 유리수를 의미한다. 여기서 유리수는 자연수와 정수를 포괄하는 수 체계적 의미로서 포함관계가 강조되지는 않는다.(중략)

• Korean Journal of Microbiology
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• v.31 no.3
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• pp.245-254
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• 1993

Distribution and variation of bacterial densities of heterotrophic plate count (HPC) and Enterobacteriaceae in the water supply systems comprising raw, treated, and three tap water samples of a water treatment plant in Seoul were studied 23 times from 1991 to 1992. HPC bacteria of raw. treated, and tap waters on $R_{2}A$ agar media were at a density of $1.22{\times}10^{3} to 3.05{\times}10^{5}$, $1.50{\times}10^{1} to 4.29{\times}10^{3}$ and 2 to $5.41{\times}10^{3}$ cfu/ml, respectively. Densities of Enterobacteriaceae in raw, treated, and tap waters on mENDO-LES agar media ranged from 0.] to 8200 cfu/ml, 0 to 17.5 cfu/JOO mI. and 0 to 47.5 cfu/IOO ml, respectively. Injured Enterobacteriaceae of treated and tap waters on m-T7 agar media were at a density of o to 27 and 0 to 35 cfu/100 mI. These results showed that the density of bacteria in the treated water outflowing from the water plant significantly increased as the water flowed along the distribution sytems, which is so-called bacterial regrowth. The predominant bacteria] types in the water supply system were Pw'udomonas and Acinerobacter. In raw water, the ratio of Pseudomonas was higher than that of Acinetobaeter, but in treated and tap waters. both ratios were reversed. The most predominant species of Enterobacteriaceae was Enterobacter agglomerans. Some species such as Citrobacter freundii. Escherichia coli. Klebsiella pneumoniae. and Shigella dysenteriae which are opportunistic pathogens or pathogens were not found in the treated water but additionally detected in tap waters.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.5-14
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• 2010

Recent researches on the behavior of gravelly soils have been focused mainly on the relative density or on the gravel content. And some researchers presented the liquefaction behavior based on the relative density whereas others based on the gravel content of gravelly soil. However the relative densities vary with gravel content and relative density is not enough to fully express the behavior of gravelly soils. Therefore in this research state parameter which considers void ratio and effective confining pressure is introduced and Steady State Line(SSL) of gravelly soils for various gravel content are determined by undrained triaxial tests in order to express the behavior of gravelly soils. From the research the position of SSL moved downward with gravel content. And the same density of soil showed dense sand behavior or loose sand behavior depending upon the confining pressure. Especially relative density 80% of gravelly soil showed loose sand behavior under high confining pressure. However the gravelly soils with similar state parameters showed similar stress behaviors. It can bee seen that state parameter is useful tool to evaluate undrained behavior of gravelly soils. Also state parameter and undrained strength showed good correlations.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.699-705
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• 2007

In this study, the improvement of the operation condition and the water quality in water treatment plant by operating information system(OIS) was evaluated for Ansan water treatment plant. The average flow rate of raw water in the year 2005(after constructing the OIS) appeared 15.6 % lower than that in the year 2004(before constructing the OIS). The mean value(12.37 NTU) of raw water turbidity in the year 2005 remained constant, or nearly so with that(12.06 NTU) in the year 2004. The average dosing rates of coagulant appeared 12.06 mg/L in the year 2005 which was higher than 10.31 mg/L in the year 2004. Furthermore, the average turbidity concentration of fresh water in the year 2005 appcared slightly better than that in the year 2004. From $COD_{Mn}$ and BOD concentration of raw water, the water quality in the year 2005 were better than those in the year 2004. The average concentration of $KMnO_4$ in the year 2004 and the year 2005 was 2.95 mg/L and 1.25 mg/L, respectively, and the average concentration of THMs in the year 2004 and the year 2005 appeared 0.038 mg/L and 0.025 mg/L, respectively. Therefore, the fresh water quality in the year 2005 was better than that in the year 2004. In this study, it is considered that the operation of Ansan water treatment plant may be optimized by OIS, and thus the OIS may be very useful method to improve the water quality.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.913-920
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• 1995

RFe$_2$(R=rare earth) Laves Phase intermetallic compounds are one of the promising materials for magnetostrictive applications, due to large magnetostriction coefficients in the order of 10$^{-3}$ . However, because RFe$_2$intermetallic compounds have large magnetostriction constants as well as large magnetocrystalline anisotropy constants, a large external magnetic field is necessary to reach saturation magnetostriction. Hence researches on giant magnetostriction have been concentrated on producing materials exhibiting a high value of magnetostriction in a low magentic field. The main research trend of the giant magnetostriction to obtain the large value in the low magnetic filed, fortunately as the signs of magnetocrystalline anisotropy constans in RFe$_2$intermetallic compounds alternate with the rare earth metals, has been to substitute the rare earth metal for others and hence to reduce the magnetocrystalline anisotropy energy. In addition, amorphous RFe$_2$alloys have been researched. In this research, both of the methods which are substitution of the rare earth metal and amorphization in RFe$_2$ intermetallic compounds are simultaneously conducted to obtain the large magnetostriction coefficient in the low external magnetic field. Among them, SmFe$_2$and PrFe$_2$are selected, and amorphized in substrate-free bulk state. Magnetism in amorphous bulk (Sm$_{1-x}$ Pr$_{x}$) Fe$_2$alloys is investigated in the low magnetic field.ld.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1283-1293
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• 2022

The purpose of this study is to predict residual chlorine in order to maintain stable residual chlorine concentration in sedimentation basin by using artificial intelligence algorithms in water treatment process employing pre-chlorination. Available water quantity and quality data are collected and analyzed statistically to apply into mathematical multiple regression and artificial intelligence models including multi-layer perceptron neural network, random forest, long short term memory (LSTM) algorithms. Water temperature, turbidity, pH, conductivity, flow rate, alkalinity and pre-chlorination dosage data are used as the input parameters to develop prediction models. As results, it is presented that the random forest algorithm shows the most moderate prediction result among four cases, which are long short term memory, multi-layer perceptron, multiple regression including random forest. Especially, it is result that the multiple regression model can not represent the residual chlorine with the input parameters which varies independently with seasonal change, numerical scale and dimension difference between quantity and quality. For this reason, random forest model is more appropriate for predict water qualities than other algorithms, which is classified into decision tree type algorithm. Also, it is expected that real time prediction by artificial intelligence models can play role of the stable operation of residual chlorine in water treatment plant including pre-chlorination process.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.150-168
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• 2023

The anisotropic behavior of rocks is primarily attributed to the directional arrangement of rock-forming minerals and the distribution characteristics of microcracks. Notably, sedimentary and metamorphic rocks often exhibit distinct transverse isotropy in terms of their strength and deformation characteristics. Consequently, it is crucial to gain accurate insights into the deformation and failure characteristics of transversely isotropic rocks during rock mechanics design processes. The deformation of such rocks is described by five independent elastic constants, which are determined through laboratory testing. In this study, the characteristics of the directional variation of apparent elastic constants in transversely isotropic rocks were investigated using experimental data reported in the literature. To achieve this, the constitutive equation proposed by Mehrabadi & Cowin was introduced to calculate the apparent elastic constants more efficiently and systematically in a rotated Cartesian coordinate system. Four transversely isotropic rock types from the literature were selected, and the influence of changes in the orientation of the weak plane on the variations of the apparent elastic modulus, apparent shear modulus, and apparent Poisson's ratio was analyzed. Based on the investigation, a new constraint on the elastic constants has been proposed. If the proposed constraint is satisfied, the directional variation of the apparent elastic constants in transversely isotropic rocks aligns with intuitive predictions of their tendencies.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.1-7
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• 1999

We present VLSI architecture for a high performance 2-D DCT processor which is used compressing system of real time image processing or HDTV using fast computational algorithm of the Optimized Integer Cosine Transform(OICT). The coefficients of the OICT are integer, so the OICT performs only the integer operations for both forward and inverse transform. Therefore the proposed architecture could be greatly enhanced in improving the speed, reduced the hardware cost considerably by replacing the multiplication operations with shift and addition operations compared with DCT which performs floating-point operations.