• Resources Recycling
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• v.21 no.6
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• pp.12-22
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• 2012

This study investigated a utilization technology of light burned dolomite. light burned dolomite ($CaMg(CO_3)_2$) generated in furnace (steel manufacturer) is an alternative to quick lime. Using light burned dolomite has an effect on reducing the consumption of fluorite slag MgO concentration in supersaturated solution by prolonging the life of softening effect. Armophous MgO, not containing periclase is formed by firing dolomite under $800^{\circ}C$. It has larger surface area and higher reactivity than periclase, and also shows better expansion effect than quicklime. Due to those effects, therefore, armophous MgO produced from light burned dolomite is used as an alternative expansion agent in mortar. In the experiment, characteristics of light burned dolomite were compared to those of existing expansion agents such as anhydrite and quicklime. Then, each expansion and shrinkage rates were measured over a period of about 3 months in both of 1m Jis mold at labscale and apartment mortar flooring at field scale. In the result, it was observed that light burned dolomite in mortar flooring more compensates for the expansion and shrinkage rates than the existing expansion agents, showing low expansion rate of below 0.05% and also decreases the crack.

• Journal of Conservation Science
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• v.31 no.1
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• pp.29-35
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• 2015

Investigation on relics was performed by dividing the site of Samheung-ri, Gangjin-gun, Jeonranam-do into six districts, A to F, and as a result, total 16 kilns including Celadon kilns and pottery kilns were found. Among them, total 9 kilns found from A D E F districts including 3 Celadon kilns, 6 pottery kilns, went through archaeomagnetic analysis with baked earth samples collected from them. Since those baked earth samples showed good baking conditions as well as high soil quality, it was possible to gain archaeomagnetic data with high reliability. Through archaeomagnetic analysis, it was possible to obtain archaeomagnetic dating for each of the 9 kilns corresponding to the period between A.D. 990~1250, and the results also correspond to archaeological dating estimated to fall under the period of Goryeo. Also, it was examined if there was any difference in the operational periods of the kilns by districts, and there was difference of periods from archaeomagnetic dating in the order of district D(A.D.1100) ${\rightarrow}$ E F(A.D.1180) ${\rightarrow}$ A(A.D.1210). This result tells us that the kilns in district D stopped operating the earliest and were deserted, and next, those in districts E and F almost at the same time, and lastly, those in district A operated to the last and then were disposed.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.118-126
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• 2014

The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for concrete pumping performance for the rapid construction of super-tall buildings. In this study, a quantitative evaluation of concrete fluid characteristics and surface friction resistance was performed, applying different concrete mix proportions and pumping conditions. To achieve this, we developed a temporary horizontal pumping evaluation system to measure pipe pressure and surface friction characteristics, and performed an experiment to investigate the relations between concrete rheology characteristics and friction resistance in pipe. The experiment found that in terms of the rheology characteristics, plastic viscosity was reduced remarkably after pumping. As well, high regression between the surface friction and pressure gradient was confirmed. This means that it is possible to evaluate the friction resistance between concrete and pipe by means of a pumping system that includes a frictional resistance testing pipe. In addition, high regression between the plastic viscosity of concrete after pumping and friction resistance coefficient was confirmed. Finally, it is considered that pumping pressure can be predicted using the friction resistance coefficient derived in this study, and it has high regression.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.429-438
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• 2011

In this study, the explicit numerical algorithm was proposed to simulate the stress erection process and ultimate-load analysis of the strarch (stressed arch) system. The strarch system is a unique and innovative structural system and member prestress comprising prefabricated plane truss frames erected through a post-tensioning stress erection procedure. The flexible bottom chord, which has sleeve and gap details, is closed by the reaction force of the prestressing tendon. The prestress imposed on the tendon will enable the strarch system to be erected. This post-tensioning process is called "stress erection process." During this process, plastic rigid-body rotation occurs to the flexible top chord due to the excessive amount of plastic strain, and the structural characteristic is unstable. In this study, the dynamic relaxation method (DRM) was adopted to calculate the nonlinear equilibrium equation of the system, and a displacement-based finite-element-formulated filament beam element was used to simulate the nonlinear behavior of the top chord sections of the strarch system. The section of the filament beam element was composed by the amount of filaments, which can be modeled by various material models. The Ramberg-Osgood and bilinear kinematic elastic plastic material models were formulated for the nonlinear material behaviors of the filaments. The numerical results that were obtained in the present study were compared with the experiment results of the stress erection and with the results of the ultimate-load analysis of the strarch unit frame. The results of the present studies are in good agreement with the previous experiment results, and the explicit DRM enabled the analysis of the post-buckling behaviors of the strarch unit frame.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.170-170
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• 2013

형광체를 조명과 디스플레이 산업에 응용하기 위해서는 충분히 밝은 빛을 제공하는 형광체의 발광 세기가 중요한 변수이다. 이러한 발광 특성은 주로 모체 격자에 도핑 되는 활성제의 농도, 입자의 형상과 크기 분포의 균일성, 결정성에 따라 달라진다. 본 연구에서는 Ca2SiO4 모체 결정에 도핑한 활성제 Eu3+와 Dy3+ 이온의 농도를 변화시키면서 고상 반응법을 사용하여 높은 발광 효율을 갖는 Ca2-1.5xSiO4::Eux3+ 적색 형광체와 Ca2-1.5xSiO4:Dyx3+ 백색 형광체를 합성하였다. 특히, 활성제 Eu3+와 Dy3+ 이온 농도의 변화가 형광체의 결정 구조, 소성 온도, 입자의 표면 형상, 광학 스펙트럼의 발광 효율에 미치는 영향을 조사하여 최적의 합성 조건을 결정하였으며, 회절 신호의 반치폭과 발광 세기의 상호 관계를 조사하였다. Ca2-1.5xSiO4::Eux3+와 Ca2-1.5xSiO4:Dyx3+ 형광체 초기 분말 시료는 CaO (99.9% 순도), SiO2 (99.9%), Dy2O3 (99.9%)와 Eu2O3 (99.9%)인 화학 물질을 구입하여 초정밀 저울로 화학양론적으로 측정하였다. 이때 Eu와 Dy의 함량비는 x=0, 0.01, 0.05, 0.1, 0.15, 0.2 mol로 변화 시키면서 합성하였다. Ca2-1.5xSiO4: Dyx3+ 형광체 분말 시료의 경우에 소결 온도를 각각 $1000^{\circ}C$와 $1100^{\circ}C$로 달리하여 흡광과 발광 스펙트럼의 세기를 비교해 본 결과, 서로 다른 두 소결 온도에서 합성한 두 형광체 분말은 동일하게 Dy3+의 몰 비가 0.05 mol일 때 주 발광 스펙트럼의 세기는 최대값을 나타내었다. 파장 355 nm로 여기시킨 Dy3+ 함량비에 따른 Ca2-1.5xSiO4:Dyx3+ 형광체 분말의 발광 스펙트럼은 Dy3+ 함량비에 관계 없이 581 nm에서 가장 강한 황색 발광을 보였다. 함량비가 증가함에 따라 발광 스펙트럼의 변화가 관측되었는데, Dy3+의 몰 비가 0.01 mol~0.05 mol인 영역에서는 발광 세기가 증가하여 0.05 mol에서 최대를 나타내다가 Dy3+의 몰 비가 더욱 증가함에 따라 발광세기는 현저히 감소하는 경향을 나타내었는데, 이 현상은 농도 소광 현상으로 해석 할 수 있다. 이외에도, Eu3+와 Dy3+ 이온의 함량비와 소결 온도가 결정 입자의 크기와 흡광 스펙트럼에 미치는 결과를 조사하였다.

• Korean Journal of Food Science and Technology
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• v.32 no.5
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• pp.1093-1101
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• 2000

The effects of concentration and pH on the emulsifying and rheological properties of the pine nut's protein extract(PNPE) and carbohydrate extract(PNCE) were investigated. Emulsifying activity index(EAI) of sample containing PNPE was minimal at pH 4.0 and the alteration of pH from 4 to 3 or 8 increased EAI regardless of concentration. The most EAI(about 6.44 $m^2/g$ solid) significantly(p<0.05) observed in solution containing 1% PNPE at pH 8.0, but that of 3% PNPE(0.10 $m^2/g$ solid) was minimal at pH 4.0. The emulsion stability exhibited maximum value(about 20) in 3% PNPE emulsion at pH 8.0. However, EAI of samples containing PNCE increased gradually with the increase of pH, but it had lower value than that of samples containing PNPE. At pH 7.0 and 8.0, the rheological behavior of emulsion solutions showed Newtonian fluid(n=1, $r^2>0.99$) regardless of concentration in all samples containing PNPE, but the samples containing PNCE showed pseudoplastic behavior(n<1) in all conditions. The sample with the better emulsion stability index(ESI) significantly(p<0.05) exhibited the higher L, b, and ${\delta}E$, however, lower a value.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.5
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• pp.906-912
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• 2001

The effects of aerobic exercises and/or supplementation of kimchi on changes of the body composition and plasma lipids of obese middle school girls were studied. Thirty eight girls, 28 obese girls and 10 normal weighed girls, were paricipated. Among obese girls, 8 were assigned to exercise group (FG) 12 were grouped as kimchi group (KG) , and 8 were asked to practice excercise and to take kimchi simultaneously(excercise kimchi group, EKG). Ten girls whose weight is normal asked to remain o their own diet during 6 weeks of experiment (control group, CG)/ EG practiced jogging and rope-jumping for 60 minutes four times a week and KG took 3 g of freeze-dried kimchi packed in a 500 mg capsule daily which is equivalent to 30 g of fresh kimchi, EKC, EG and KG showed beneficial effects on changes of the body composition and plasma lipids compared to those of CG, EG showed greater effect than KG in reducing body fat resulted decrease in BMI, fat mas,. abdominal fat, and triglyceride concentration and increase in HDL-cholesterol. KG seemed to have greater effect on lowering plasma cholesterol and LDL-cholesterol than EG/ But the greatest effects in terms of reduction in weight, BMI fat mass, abdominal fat, total cholesterol, LDL-cholesterol, triglyceride, and increase in HDL-cholesterol were observed from EKG. These results indicate that kimchi supplemenation while practicing excercise might improve the obese state by reducing body fat content as well as reducing plasma lipids.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.520-520
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• 2016

석유 화학공장에서 발생하는 spent sulfidic caustic (SSC) 폐수는 액화석유가스(LPG)나 천연가스(NG)의 정제과정에서 발생되는 것으로 고농도의 sulfide와 cresylic, phenolic 그리고 mercaptan 등이 포함된 독성과 냄새를 유발하는 물질이다. 이러한 물질들은 LPG나 NG의 정제과정에서 높은 산도를 가진 휘발성 황화합 물질들을 제거하기 위해 사용된 NaOH가 $H_2S$와 반응하여 발생하는 것이다. 진한 갈색 또는 검은색을 띄는 SSC 폐수는 12 이상의 높은 pH를 가지고 있으며 5~12 wt%의 높은 염분도를 가지고 있다. 또한 강한 부식성과 독성을 가진 황화합물의 농도가 1~4 wt%이며, 방향족 탄화수소 물질 (i.e. methanethiol, benzene, tolune and phenol)들도 다량 함유되어 있다. 따라서 이러한 유해 물질들은 기존의 하수처리 공정으로 방류하기 전에 완벽하게 처리해야만 하수처리 공정의 오염 부하량을 줄일 수 있다. 습식산화공정은 SSC 폐수를 처리하기 위해 흔히 사용되고 있는 물리-화학적 처리 공정이지만 고비용, 고에너지가 필요하며, 고온 및 고압에서만 작동되어 안전상의 문제점을 갖고 있다. 또한 습식산화공정을 거친 폐수는 배출허용기준을 만족하기 위해 생물학적 2차 처리가 반드시 필요하다. 철-과산화수소를 이용하는 펜톤산화 공정, 그리고 sulfide를 sulfate로 전환시키는 생물학적 처리 공정은 황화합물의 완전한 무기물화가 힘들며, 현장 적용 시 기술적 경제적 부담이 크다. 이러한 단점을 극복하고, SSC 폐수를 효과적으로 처리하기 위해 본 연구는, 높은 흡착력과 광산화력을 가진 흡착광산화 반응 시스템(Adsorption Photocatalysis System, APS)을 개발하였다. APS는 SSC 폐수를 시스템 내부로 유입하여 수중의 오염물질을 흡착광산화제로 구성된 반응구조체가 흡착하고, 흡착된 오염물질을 UV에너지와 이산화티타늄 광촉매의 광화학반응에 의해 최종적으로 무해한 물질로 환원시키는 폐수처리시스템이다. APS의 반응구조체는 태양에너지 및 인공에너지원에 의해 활용 가능하며, 난분해성 유기화합물질을 물과 이산화탄소로 분해할 수 있는 친환경적이고 경제적인 소재로서 널리 쓰이고 있는 이산화티타늄 광촉매와 화력발전소의 높은 소성온도에 의해 연소된 후 발생되는 bottom ash를 이산화티타늄의 지지체로 사용하여 높은 흡착력과 광촉매 산화력을 가진 복합물이다. 개발된 APS에 의해 SSC 폐수를 처리한 결과, COD 86.1%, 탁도 98.4%, sulfide 99.9%의 높은 처리효율을 보여주고 있다. 따라서 본 연구를 통해 개발된 APS는 강한 부식성과 독성 그리고 높은 농도를 가지고 있는 SSC 폐수를 효과적으로 처리할 수 있다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.107-113
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• 2006

Water treatment plant sludge occurred in sedimentation and inverse wash process is generally disposed by ocean dumping or reclamation after dehydration processing using mechanical or natural dry method. Recently, ocean dumping of sludge is limited actually by London Convention. Physical, chemical, and geotechnical characteristics of water treatment plant sludge were analyzed by experiments. The possibilities for recycling of the dehydration sludges as materials for covering sanitary landfill were examined. Experiments performed with sludges mixed with general soil to improved the sludge properties are the hydrometer analysis, the liquid and plastic limit test, the specific gravity test, the compaction test, and the unconfined compression test. The value of ${\gamma}_{dmax}$ is increased and OMC(Optimum Moisture Content) is lessened with mixed sludge. The value of maximum compressive strength and friction angle are increased and the cohesion is decreased with mixed sludge. The ratio between sludge and soil in mixed sludge was 3:7 and the strength of mixed sludge showed $3.6kg/cm^2$. These results satisfy the regulation of U.S. E.P.A regarding materials for covering sanitary landfill.