• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.22-29
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• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.35-41
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• 2013

In this study, flame retardancy of polyurethane foam and phenolic foam were investigated by addition of phosphorous flame retardants. The thermal degradation behavior of polyurethane foam and phenolic foam in the presence of flame retardants has been studied by thermogravimetric analysis(TGA). Heat release rate(HRR), mean HRR, mass loss rate(MLR), total smoke released(TSR) and limited oxygen index(LOI) were tested by cone calorimeter. From the test results, Phenolic foam showed low HRR, MLR and TSR than polyurethane foam.

• Fire Science and Engineering
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• v.33 no.1
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• pp.50-59
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• 2019

Experimental and numerical studies on the fire characteristics according to the distance between the fire source and sidewall under the over-ventilated fire conditions. A 1/3 reduced ISO 9705 room was constructed and spruce wood cribs were used as fuel. Fire Dynamics Simulator (FDS) was used for fire simulations to understand the phenomenon inside the compartment. As a result, the mass loss rate and heat release rate were increased due to the thermal feedback effect of the wall in the compartment fire compared to the open fire. As the distance between the fire source and sidewall was reduced, the major fire characteristics, such as maximum mass loss rate, heat release rate, fire growth rate, temperature, and heat flux, were increased despite the limitations of air entrainment into the flame. In particular, a significant change in these physical quantities was observed for the case of a fire source against the sidewall. In addition, the vertical distribution of temperature was changed considerably due to a change in the flow structure inside the compartment according to the distance between the fire source and sidewall.

• The Journal of Korean Medicine
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• v.23 no.1
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• pp.61-66
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• 2002

목적： 본 연구는 감미의 작용에 관한 "감보" 등의 이론적 바탕과 약물의 이화학적인 특성을 통해 약효를 어느 정도 예측하고자 하였다. 방법： 한약재의 오미별 이화학적 특성을 구명하기 위하여 수소이온농도(pH), $200^{\circ}C$와 $550^{\circ}C$에서의 질량감소량, 전기전도도, 가시부 및 자외부 흡수 spectrum의 전자전이에 따른 비율, TLC에 의한 주요 성분의 이동율($R_{f}{\;}value$)과 낮은 성분의 이동율($R_{f}{\;}value$)을 측정하였다. 결과： 전탕에 따른 수소이온농도(pH)의 평균은 $5.24{\pm}0.56$이었으며. 약재의 휘발 성분 및 수분 함유량은 $288{\pm}125mg$이었고, 유기물함량의 평균은 $867{\pm}116g$이었으며, 전기전도도의 평균은 $5.46{\pm}0.93S/cm$이었으며, 가시부 및 자외부 흡수 spectrum의 전자전이에 따른 흡광도 비율($\pi{\\rightarrow}\pi^{*}/n{\rightarrow}\pi^{*}$)의 평균은 $3.043{\pm}0.679$이었으며, TLC에 의한 주요 성분의 이동율($R_{f}{\;}value$)의 평균은 $0.553{\pm}0.317$이었고, TLC에 의한 낮은 성분의 이동율($R_{f}{\;}value$)의 평균은 $0.136{\pm}0.122$ 이었다. 결론：약재의 pH는 모두 7보다 낮은 약산성 이었으며, 약재의 휘발 성분 및 수분 함유량은 대략 10~50%정도를 나타내었다. 유기물함량은 대략 80~95%정도를 나타내었다. 전기전도도를 통하여 산약이나 감초는 이온성 물질을 많이 포함하고 있으리라 추정된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.112-112
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• 2020

하천에서 유해화학물질 유입 사고 발생 시 수환경 피해를 최소화하기 위해 신속한 초기 대응이 필요하다. 따라서, 본 연구에서는 수환경 화학사고 대응 시스템 구축을 위해 하천 실시간 모니터링 지점에서 관측된 유해화학물질의 농도 자료를 이용하여 발생원의 유입 지점과 유입량을 역추적하는 프레임워크를 개발하였다. 본 연구에서 제시하는 프레임워크는 첫 번째로 하천 저장대 모형(Transient Storage Zone Model; TSM)과 HEC-RAS 모형을 이용하여 다양한 유량의 수리 조건에서 화학사고 시나리오를 생성하는 단계, 두번째로 생성된 시나리오의 유입 지점과 유입량에 대한 시간-농도 곡선 (BreakThrough Curve; BTC)을 21개의 곡선특징 (BTC feature)으로 추출하는 단계, 최종적으로 재귀적 특징 선택법(Recursive Feature Elimination; RFE)을 이용하여 의사결정나무 모형, 랜덤포레스트 모형, Xgboost 모형, 선형 서포트 벡터 머신, 커널 서포트 벡터 머신 그리고 Ridge 모형에 대한 모형별 주요 특징을 학습하고 성능을 비교하여 각각 유입 위치와 유입 질량 예측에 대한 최적 모형 및 특징 조합을 제시하는 단계로 구축하였다. 또한, 현장 적용성 제고를 위해 시간-농도 곡선을 2가지 경우 (Whole BTC와 Fractured BTC)로 가정하여 기계학습 모형을 학습시켜 모의결과를 비교하였다. 제시된 프레임워크의 검증을 위해서 낙동강 지류인 감천에 적용하여 모형을 구축하고 시나리오 자료 기반 검증과 Rhodamine WT를 이용한 추적자 실험자료를 이용한 검증을 수행하였다. 기계학습 모형들의 비교 검증 결과, 각 모형은 가중항 기반과 불순도 감소량 기반 특징 중요도 산출 방식에 따라 주요 특징이 상이하게 산출되었으며, 전체 시간-농도 곡선 (WBTC)과 부분 시간-농도 곡선 (FBTC)별 최적 모형도 다르게 산출되었다. 유입 위치 정확도 및 유입 질량 예측에 대한 R²는 대부분의 모형이 90% 이상의 우수한 결과를 나타냈다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.53-62
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• 2024

In this paper, an experimental study on the strengths and material properties of concrete manufactured by using coal gangue, as a fine aggregate was conducted. Experimental parameters included coal gangue aggregate contents as a replacement of fine aggregate by 50 % and 100 % (by volume) and fly ash contents. The water-binder ratio was fixed at 0.38. In addition, 30 % of the OPC binder was replaced with fly ash in some mixtures. Test of the unit weight, compressive, split tensile, and flexural tensile strength of concrete were performed and test results were analyzed. Unit weight, compressive strength, split tensile strength, and flexural tensile strength decreased as the coal recycled aggregates increased. In addition, TGA and SEM experiments, which are microstructure experiments, were conducted to analyze thermogravimetric analysis and ITZ by section.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.283-290
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• 2009

Differently from fly ash, the bottom ash produced from thermoelectric power plant has been treated as an industrial waste matter, and almost reclaimed a tract from the sea. If this waste material is applicable to foam concrete as an aggregate owing to its light-weight, however, it may be worthy of environmental preservation by recycling of waste material as well as reducing self-weight of high-rising structure and horizontal forces and deformations of retaining wall subject to soil pressure. This study has an objective of evaluating the effects of application of bottom ash on the mechanical properties of foam concrete. Thus, the ratio of bottom ash to cement was selected as a variable for experiment and the effect was measured in terms of unit weight of concrete, air content, water-cement ratio and compressive strength. It can be observed from experiments that the application ratios have different effects on the material parameters considered in this experiment, thus major relationships between application ratio and each material parameter were finally introduced. The result of this study can be applied to decide a mix design proportion of foam concrete while bottom ash is used as an aggregate of the concrete.

• Explosives and Blasting
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• v.34 no.4
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• pp.28-34
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• 2016

Empirical model, phenomenological model, and CFD model have been used to evaluate the blast effects produced by explosion of explosives, flammable gas and liquid or dust. TNT equivalence method which is one of empirical models has been widely used as it is simple. In this study, new peak overpressure-scaled distance and scaled impulse-scaled distance equations are induced through fitting data from the curves given by TNT equivalence method. If the TNT equivalent mass is calculated, it is possible to estimate the peak overpressure and impulse using the regression equations. Differences of peak overpressure with yield factor which is a component of TNT equivalence method are found to be great in near-by distances from explosion source where the increase in overpressure is very steep, but the differences are getting smaller as the distances increase.

• Elastomers and Composites
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• v.40 no.3
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• pp.166-173
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• 2005

Effect of thermal aging on the weight loss and water absorption of epoxy adhesives was investigated in the presence of three types of different hardeners, such as D-230, G-5022, and HN-2200. Thermal and mechanical properties of the cured epoxy resins were also studied througth the glass transition temperature and shear adhesion strength measurements. Weight losses of DGEBA/D-230 and DGEBA/HN- 2200 systems were not varied. However, the weight of DGEBA/G-5022 system was significantly decreased with increasing the thermal aging time. The water absorption of the specimens was increased as the thermal aging time increased except that using G-5022. DEGBA/HN-2200 system showed higher $T_g$ value than those of other systems, due to the formation of the fine three-dimensional network structure containing aliphatic ring. Shear adhesion strength of all systems was increased with increasing the thermal aging tine, which is attributed to increased degree of cure and fine three-dimensional network structure formation. And $T_g$ values and shear adhesion strength of all specimens exposed to water was decreased as the immersion time increased.

• Tuberculosis and Respiratory Diseases
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• v.54 no.4
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• pp.395-402
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• 2003

Background : Patients with chronic obstructive pulmonary disease (COPD) are at increased risk for osteoporosis, which has implications for mobility and even mortality. The goal of this pilot study was to evaluate bone mineral density (BMD) and risk factors for osteoporosis in a limited number of men with COPD. Methods : We checked BMD, $FEV_1$(% of predicted) and investigated risk factors for osteoporosis in 44 male patients with COPD who visited our hospital from January to August 2002. Results : Mean(${\pm}$) age was $69{\pm}9$ yrs, body mass index(BMI) $21{\pm}3kg/m^2$, $FEV_1$ $50{\pm}18%$ of predicted, lumbar spine T-score $-3.0{\pm}1.2$, lumbar spine Z-score $-2.0{\pm}1.2$, and lumbar spine BMD $0.76{\pm}0.13g/cm^2$. Osteoporosis(T-score below -2.5) was present in 27 patients(61.4%) and osteopenia(T-score between -1 and -2.5) in 17(38.6%). None of the patients had normal BMD. There was no relationship between BMD and $FEV_1$(% of predicted). There were significant differences in smoking, alcohol consumption, exercise, cumulative steroid dose, BMI and BMD among the three groups according to $FEV_1$(% of predicted) (group1 : ${\geq}65%$, group2 : 50-64%, group3 : ${\leq}49%$), except age. However, there were no significant differences in these variables between the osteopenia and osteoporosis groups, except BMI. Linear Regression(Stepwise) analysis showed that lumbar BMD was correlated with BMI & exercise. Conclusion : BMD is significantly reduced in men with COPD. There was no relationship between BMD and pulmonary function.