• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.101-111
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• 2016

It is possible that aggregates add on to geopolymer based fly ash to mix mortar and concrete like cement. This is necessary to evaluate mineral composition, particle shape, surface, size distribution, density and absorption ratio for fine aggregates due to few detailed research to examine influence of fine aggregates properties on unhardened geopolymer concrete. In this research, used two different fine aggregates, Jumunjin sand(having quartz, mica, feldspar, pyroxene in mineral composition, more than 96% of total size between -0.60 and +0.30mm, angular shape and rough surface) and ISO sand(having almost all quartz in mineral composition, more than 51% size between -1.40 and +0.60mm, simultaneously varied size distribution, spherical shape and smooth surface). After an experimental result of the varied ratio of Si/Al=1.0-4.1 geopolymer paste, mix proportion respectively applied Si/Al=1.5 having the highest compressive strength to mortar and Si/Al=3.5 having the highest consistency to concrete. Geopolymer mortar by mixing with Jumunjin and ISO sand in varied range of 20-50wt.% showed flow size increase between 69.5 and 112.0mm, between 70.5 and 126.0mm respectively. Geopolymer concrete at an addition of 77wt.% of total aggregates ratio showed that average compressive strength was 32MPa and the consistency was favorable to molding. Since ISO sand observing varied size distribution, spherical shape, smooth surface, low absorption ratio resulted in advantageous properties on consistency of geopolymer, geopolymer concrete can be suitable for using the fine aggregates similar to ISO sand.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.227-232
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• 1995

The model equations including scaling factors to estimate the soil water characteristics curve(SWCC) without direct measurement of soil water tension were developed. Scaling were applied to a data set of soil water content, soil water tension, particle size distribution, and OM contents of the 134 soil samples with the 10 soil textural classes. The capability of the model equations was tested on another 205 soil samples. The parameter, ${\theta}^*$, of soil water contents was used by scale transformation as follows : ${\theta}^*=[{\theta}i-{\theta}(1.5MPa)]$/$[{\theta}(10KPa)-{\theta}(1.5MPa)]$ Using ${\theta}^*$ a model equation to estimate SWCC, which was applicable to all textural classes, was developed as follows: $H(0.1MPa)=0.13{\cdot}({\theta}^*)^{-2.04}$. Other model equations to estimate the water content at the soil water tension of 10KPa [${\theta}(10KPa)$] and 1.5MPa [${\theta}(1.5MPa)$], which are required to ${\theta}^*$ were developed by using scale factors of sand(S) and silt(Si) content and organic matter content(OM) as foilows : ${\theta}(10KPa)=26.80-3.99ln[S]+2.36{\sqrt{[Si]}}+2.88[OM]$ ($R=0.81^{**}$) ${\theta}(1.5KPa)=15.75-2.86ln[S]+0.55{\sqrt{[Si]}}+0.70[OM]$ ($R=0.76^{**}$) The measured and estimated values of ${\theta}(1/30MPa)$ on the 205 soil samples were highly correlated on 1 : 1 corresponding line with $R=0.85^{**}$.

• Korean Journal of Plant Taxonomy
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• v.42 no.3
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• pp.207-210
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• 2012

Hylodesmum laxum (Candolle) H. Ohashi & R. R. Mill subsp. laxum was recorded from Korea. The species is widely distributed in S. E. Asia, but in Korea the plant was the first found in the evergreen forest of Seogwipo-si in Jeju-do. Hylodesmum H. Ohashi & R. R. Mill was raised as a separate genus recently based on Desmodium sect. Podocarpium Benth. Except for two species, all Korean species included in the former Desmodium are classified into the genus Hylodesmum. A key to and enumeration of the Korean species of Hylodesmum are provided.

• Journal of Wetlands Research
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• v.14 no.1
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• pp.131-137
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• 2012

This study was investigated to characterize the stormwater runoff pollutant materials from the urban area mixed with industrial area. Almost the similar rainfall pattern is shown during the 5 years, and the yearly precipitation was 5.2~6.6 mm. The first flushing effect during the early-stage rainfall-run off was observed in some events. EMC ranges are 19.3~39.9 mg/L for BOD, 45.2~190 mg/L for CODcr, 67.2~351 mg/L for TSS, 3.6~10.3 mg/L for TN, 1.2~2.5 mg/L for TP. Heavy metal are not detected except Zn which is observed at only one event. The particle size was distributed to 10 ${\mu}m$ at the 3% weight volume and the 50% cumulative weight percent was shown at 12 ${\mu}m$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.135-135
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• 2016

차세대 가스터빈 엔진 및 초음속 항공기 내 고온부의 온도가 증가함에 따라, 기존의 초내열합금 기반 소재를 사용하기 어려워지고 있다. 초고온 세라믹스는 높은 기계적 물성, 화학적 안정성 등 우수한 고온 특성을 가지고 있어 기존의 초고온 소재를 대체 할 수 있는 물질로 부상되고 있다. 하지만 기존의 금속 기반 소재 대비 높은 밀도로 인하여 초고온 세라믹 단일체를 비행체 부품에 적용하기에는 어려움이 있다. 이에 초고온 세라믹스와 탄소섬유를 포함하는 세라믹 복합체(Ceramic Matrix Composite, CMC)를 제작하여 동등한 기계적 물성을 보이면서 무게를 감소시키는 연구들이 진행 중에 있다. 초고온 세라믹스가 함침 된 세라믹 복합체의 경우 우수한 내삭마, 내산화 특성을 보이지만, 장시간 고온에 노출되어 탄소 섬유가 드러나게 되면 급격한 산화로 인해 소재 특성의 열화가 진행되는 단점을 가지고 있다. 따라서, 탄소 섬유가 드러나지 않도록 복합체 표면에 코팅층을 형성하여 세라믹 복합체 모재를 보호하는 방법이 활발히 연구되고 있다. 본 연구에서는 진공 플라즈마 용사 공정을 이용하여 다양한 공정조건 하에서 초고온 세라믹 코팅층을 형성하였다. 수십 마이크론 크기 분포를 갖는 HfC 분말을 Ar 유송 가스를 이용하여 플라즈마 화염 내부로 투입하였다. 플라즈마 화염 가스는 Ar 과 H2를 혼합하여 구성되었으며, 분위기 가스로는 N2를 사용하였다. 코팅에 사용된 모재로는 ZrB2 단일체와 SiC가 미량 포함된 HfC 단일체를 사용하였다. 다양한 공정 조건하에서 형성된 HfC 코팅층의 두께, 미세 조직구조를 SEM을 이용하여 관찰하였으며, XRD를 이용하여 형성된 HfC 코팅층의 결정구조를 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.270-279
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• 2000

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutants emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle configuration. Basically, nozzle which has mixed flow of gas and particle is required to have the balanced coal concentration at exit, but it is very difficult to obtain that by itself without help of other device. In this study, coal distribution and pressure drop in gas-solid flow are calculated by numerical method in nozzle with various shapes of venturi diffuser as a means to get even coal particle distribution. The tentative correlations of pressure drop and exit coal distribution are deduced as function of the height, length and reducing angle of venturi from the calculated results. When coal hurner nozzle is designed, these equations are very useful to optimize the shape of venturi which minimize uneven particle distribution and pressure drop within coal nozzle.

• Journal of Oriental Medical Thermology
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• v.2 no.1
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• pp.35-42
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• 2003

Objective : This study is to examine the interrelationship between Infertility with hypothalamic-pituitary gland disorders and Face temperature by D.I.T.I. Methods : Sample group is the 50 women who were diagnosed as P.C.O.S. or FSH,LH trouble or hyper-prolactinemia or anovulation or oligo-ovulation. Control group is the 50 women who have not P.C.O.S. & FSH.LH trouble & hyper-prolactinemia & anovulation or oligo-ovulation, who have normal menstural cycle and success in pregnancy after treatment. Both group came at Conmaul Oriental Hospital Infertility Center, Seoul, Korea, from May, 2001 to Jan., 2003. They selected at random. We checked temperature of ${\ulcorner}S17{\lrcorner}\;{\ulcorner}SI18{\lrcorner}\;{\ulcorner}TE17{\lrcorner}\;{\ulcorner}HN-3{\lrcorner}$ and gained differences of Rt. check point and Lt. check point, and then compared mean ${\Delta}T$ of sample group with that of control group. Conclusion : We gained results that mean ${\Delta}T$ of sample group is larger than that of control group at all check points. (p=0.000)

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1924-1928
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• 2009

다중패커시스템은 격리된 어느 특정 구간의 지하수를 채수할 수 있으며 그 구간의 온도, 압력 등의 자료를 연속적으로 관측할 수 있어 이를 통해 각 구간별 수리전도도를 구할 수 있다. 심도별 수직적 지하수두는 지상에서 연결 롯드를 통해 압력 측정 센서를 해당 심도까지 내려 롯드에서 설치된 압력 측정용 장비에서 관측할 수 있으며, 다중패커시스템을 이용한 수리시험으로는 양수시험, 순간충격시험, 간섭시험 등이 있는데, 본 논문에서는 순간충격시험을 이용한 결과를 제시하였다. 도출된 구간별 수리전도도를 다중패커시스템을 설치하기 전 나공에서 이중 패커를 이용한 정압주입시험의 결과와 비교하여 보았다. 다중패커시스템을 통해 획득된 심도별 지하수두는 정수두 (hydro-static)상태의 일정한 경향성이 없이, 각 심도에 존재하는 투수성 구조에 영향을 보이고 있음을 알 수 있었으며, 이는 다수의 관측공을 통해 수평 방향의 수리경사를 산출함에 있어 관측공의 심도에 대한 충분한 고려가 있어야 한다고 판단된다. 또한, 다중패커시스템을 이용한 수리시험 결과를 나공 상태에서 이중 패커를 이용한 정압주입시험 결과에 대해 심도별 도출되는 수리전도도가 국지적으로 분포하는 투수성 구조에 영향으로 인해 투수량계수 (transmissivity)로 환산한 유효 투수계수로 비교하여 결정질 암반의 수리 특성으로 제안하는 것이 타당한 것으로 분석되었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.66-75
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• 2006

As construction for road tunnel is increasing, various geotechnical conditions can be faced during the construction stage. Especially, if the tunnel is located in limestone area, many kinds of site investigations such as in-situ boring, electrical resistance survey, TSP(Tunnel Seismic Prediction) and etc., are conducted before and during the construction. By conducting these preliminary tests, location, size, and filling materials in limestone cavities can be approximately estimated. Once some cavities which can be harmful for tunnel safety are predicted, methods for ground reinforcement and tunnel excavation, corresponding those ground conditions, have to be established and verified by measurement data and numerical analysis. If necessary, invert lining should be also considered. In this paper, by studying some cases of tunnels constructed in limestone area, predicted problems during construction and rational countermeasures for those are presented.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.210-216
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• 2008

The propose of this study is evaluating which correlation of foot pressure distribution and scoliosis that happen by walking to 20'th Mens that have not experienced a scoliosis. The propose of this study is evaluating which correlation of foot pressure distribution and scoliosis that happen by walking to 20'th Mens that have not experienced a scoliosis. Measurement and analysis of Foot Pressure was executed by using by F-scan System. Degree of scoliosis was expressed as a angle used x-ray image of 5-lumbar from 4-thoracic vertebra The correlation between result of foot pressure and degree of scoliosis was evaluated under 0.05 interrelationship, and variables used for analysis were showed high correlation.