• Composites Research
• /
• 제23권1호
• /
• pp.44-50
• /
• 2010

본 연구에서는 염수 침수 실험과 염수 분무 실험이라는 두 가지의 실험을 위그선의 구조재료로 사용될 3가지 다른 복합재료 시스템에 대해서 해수와의 접촉에 의한 물성저하를재현하기 위해 수행하였다. 140일간 염수환경하에서 노화시킨 후 탄소섬유 복합재료와유리섬유 복합재료의 인장, 압축, 전단 강성과 강도 및 층간 전단 강도를 측정하였다. 기본 물성파의 비교를 통해서 염수환경이 복합재료의 기계적 물성에 미치는 영향이 평가되었다. 실험을 통해 염수 분무환경과 침수 환경의 차이는 거의 영향을 미치지 않음을 확인하였다. 탄소섬유 복합재료의 경우 인장 물성에 적은 손실이 발생한 반면 유리섬유 복합재료에서는 인장물성의 저하률이 탄소섬유 복합재료에 비해서 큼을 확인하였다. 그리고 모재 지배적 물성들의 큰 물성저하가 관찰되었다. 이를 통해, 염수는 복합재료의 섬유와 모재 사이의 계면을 퇴화시키고, 또한 모재 자체 물성과 유리섬유의 물성을 저하시킬 수 있음을 확인하였다.

• Composites Research
• /
• 제18권4호
• /
• pp.27-34
• /
• 2005

염수시험기를 통해 6개월 동안 염수분무시험과 염수침수시험을 수행함으로써 염수환경에 노출된 유리섬유직물페놀 복합재의 내구성을 실험적으로 조사하였다. 이때 염수환경에 노출된 시간에 따른 인장특성, 굽힘특성, 전단특성 등의 기계적 특성을 평가하고 동역학 측정장치를 적용하여 저장전단탄성계수. 손실전단탄성계수, tan $\delta$ 등의 열분석 특성을 측정하였다. 또한 적외선 분광분석기를 적용하여 염수환경에의 노출시간에 따른 화학구조의 변화를 분석하였다. 연구결과에 따르면 기계적 특성과 열분성 특성은 노출시간에 민감하게 변하며 노출시간이 길어짐에 따라 점차 감소되는 양상을 나타낸다. 그러나 강성의 경우에는 염수환경에 노출되면 복합재의 가소화로 인해 노출의 초기에는 감소하기 시작하고 노출시간이 길어짐에 따라 복합재의 팽창, 수지의 소성화, 가교 결합의 증가 등으로 인해 다소 증가하는 양상을 나타내지만 노출시간이 더욱 더 길어지면 점차 감소할 것으로 추측된다. 또한 FT-IR 선도에서의 피크 형상과 위치는 노출시간에 큰 영향을 받지 않으며 피크 세기는 노출시간에 따라 달라진다. 마지막으로 염수침수환경은 염수분무환경에 비해 유리섬유직물/복합재의 내구성에 더욱 심각한 영향을 미침을 알 수 있었다.

• 터널과지하공간
• /
• 제21권2호
• /
• pp.138-144
• /
• 2011

광산이 폐광을 하는 경우 배수시스템을 정지함으로 인해 갱도는 물로 포화된다. 갱도가 포화되었을 때 갱도 주변의 암석은 완전히 포화되고 갱도 주변 암반에는 수압이 작용한다. 암석의 일축압축강도는 함수율에 따라 달라지며 함수율이 증가함에 따라 감소한다. 수압은 암석 내 균열이나 암반 내 불연속면의 확장을 유발하게 된다. 갱도 내 포화된 수압이 지보압을 발휘할 수도 있지만 지하수에 의해 발생한 암반 물성의 저하는 갱도의 안정성을 감소시킬 것이다. 본 연구에서는 수압에 의해 발생한 갱도 주변 암반의 물성 저하가 갱도의 안정성에 미치는 영향을 평가하기 위하여 2차원 불연속해석과 3차원 연속해석을 실시하였다. 수치해석 결과 수압에 의해 유발된 갱도 주변 암반의 물성 저하는 갱도 주변 암반의 변위 증가에 영향을 미치고, 2차원 해석 결과는 3차원 해석 결과 보다 큰 변위를 나타냈다.

• 펄프종이기술
• /
• 제47권5호
• /
• pp.112-119
• /
• 2015

The pulp mold attract the increasing concern as recyclable, biodegradable, and eco-friendly packaging materials. In order to broaden the applicability of the pulp mold as substitutes of the expanded styrofoam, the properties of various raw materials for the pulp mold were evaluated and the way for improving water resistance properties of the pulp mold were also tested by applying some additives. The higher value in the fines contents and in the water retention value were shown for the TMP (thermomechanical pulp), which resulted in the bulkier pulp mold with the higher moisture absorption property. In case of water resistance properties, the pulp mold made of white ledger stock showed the higher value in water contact angle and very slow water absorption rate. The addition of oil palm EFB fiber showed the improvement in the water resistance of the pulp mold made of UBKP. The effects of various additives on the improvement in the water resistance properties of the pulp mold were tested by using AKD, PVAm, epoxy resin. The application of AKD leaded to the higher increase in the water resistance. The results in this study showed the effects of AKD for the pulp mold could be improved and optimized by the application with fixing agent and by the ageing treatment after production.

• 자원환경지질
• /
• 제31권2호
• /
• pp.101-110
• /
• 1998

The purpose of this study is to elucidate the source of U anormaly formed in stream water of the drainage system around the Shinbo talc mine area based on the hydrochemical properties of water masses including surface water and groundwater. The hydrochemical properties of water masses in the Shinbo talc mine area are divide into three types; Type I : $Ca(Mg)SO_4$ type with high U content as shown in the stream water flowout from the mine, Type II : $Ca(HCO_3)_2$ type with high U content as in deep groundwater, Type III : $Ca(HCO_3)_2$, type with low U content as in the other stream water and shallow groundwater. It is necessary to emphasize that in deducing the uranium source, a distinct discrimination between type I and type II is showed in their hydrothermal properties in spite of commonly having a high uranium content, which in turn means the occurrence of a different water-rock interaction processes between both type. All evidences suggest that type II groundwater have acted as a primary media in the transport of uranium and that, as the groundwater flows through the talc mineralization zone, water composition of type II was transformed into that of type I water as the results of a secondary water rock interaction process, caused by imposition of new mineralogically controlled thermodynamic constraints. Consequently, in the viewpoint of hydrochemical exploration, the investigation of the hydrologic circulation system and the hydrogeologic properties for the aquifer of type II groundwater shall be done first of all and will provide a crucial clue on tracing the uranium mineralization zone occurred in the Shinbo talc mine area.

• Advances in concrete construction
• /
• 제5권2호
• /
• pp.87-99
• /
• 2017

After passing through a magnetic field, the physical quality of water improves, and magnetic water (MW) is produced. There are many investigations on the effects of magnetic field on water that shows MW properties like saturation and memory effect. This study investigates the fresh and hardened properties of concrete mixed with MW, which contains silica fume (SF) and superplasticizer (SP). The test variables included the magnetic field intensity for producing MW (three kinds of water), SF content replaced cement (0 and 10 percent), water-to-cementitious materials ratio (W/CM=0.25, 0.35 and 0.45) and curing time (7, 28 and 90 days). The results of this study show that MW had a positive impact on the workability and compressive strength of concrete. By rising the intensity of the magnetic field which was used for producing MW, its positive influence on both workability and compressive strength improved. MW had greater positive impacts on samples containing SP that did not have SF. Moreover, the best compressive strength improvements of concrete achieved as W/CM ratio decreased.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.147-152
• /
• 2001

The purpose of this study is to ascertain the strength properties of water-permeable polymer concretes with SBR latex and redispersible polymer powder. The water-permeable polymer concretes using SBR latex and redispersible polymer powder with water-binder ratio of 29%, polymer-cement ratios of 0, 5, 10, 15 and 20% are prepared, and tested for compressive strength, tensile strength, flexural strength, water permeability. From the test results, improvements in the strength properties of the water-permeable polymer concretes due to the addition of the SBR latex and redispersible polymer powder are discussed.

• Tribology and Lubricants
• /
• 제33권6호
• /
• pp.245-250
• /
• 2017

In this work, we examine pure water and water with nanoparticles to investigate water lubrication characteristics and the effect of nanoparticles as lubricant additives for different substrates. We test carbon-based coatings and metals such as high-speed steel and stainless steel in pure deionized (DI) water and DI water with nanoparticles. We investigate water lubrication characteristics and the effect of nanoparticles based on the friction coefficient and wear rate for different substrates. The investigation reveals that nanoparticles enhance the friction and wear properties of high-speed steel and stainless steel. The friction coefficient and wear rate of both high-speed steel and stainless steel decreases in DI water with nanoparticles compared with the results in pure DI water. The presence of nanoparticles in water show good lubricating effect at the contact area for both high-speed steel and stainless steel. However, for carbon-based coatings, nanoparticles do not improve friction and wear properties. Rather, the friction coefficient and wear rate increases with an increase in the concentration of nanoparticles in case of water lubrication. Because carbon-based coatings already have good tribological properties in a water environment, nanoparticles in water do not contribute toward improving the friction and wear properties of carbon-based coatings.

• 유변학
• /
• 제11권1호
• /
• pp.28-33
• /
• 1999

붕산은 폴리비닐알코올(PVA)의 히드록시기간의 가교를 형성할 수 있기 때문에 PVA용액내에 가입되면 용액의 유변학적 특성에 큰 영향을 미친다. 본 연구에서는 양이온이 존재하지 않는 경우 PVA/디메틸술폭시드(DMSO)/물/붕산계에 있어서 물의 함량이 유변학적 특성에 미치는 영향을 조사하였다. PVA/DMSO/물계에 붕산을 1 wt.% 첨가할 경우 물 함량이 증가할 수록 점도가 급속히 감소하였다. PVA/DMSO계에 1 wt.%의 붕산이 가입된 경우 양이온이 없어도 강한 가교구조를 형성하여 탄성겔의 점탄성특성을 나타낸 반면 PVA/물계에 1 wt.%의 붕산이 가입된 경우 전형적인 점성물질의 특성을 나타냈다. 순수한 DMSO나 혼합용매중 DMSO의 함량이 높으면 양이온의 존재없이도 붕산첨가에 의해 가교구조를 형성하여 급격한 점도변화를 나타냈으나 물 함량이 풍부한 계에서는 붕산의 첨가에 따른 점도의 변화가 미약하였으며 순수한 물을 용매로 사용한 경우 붕산첨가의 영향이 거의 없었다. 저장탄성률도 PVA/DMSO계의 경우가 가장 높은 값을 보였고 혼합용매계에는 물함량이 증가할 수록 감소하였다.

• Environmental Engineering Research
• /
• 제24권1호
• /
• pp.45-53
• /
• 2019

Water and soil properties in paddy fields subjected to organic and conventional farming were characterized over the rice cycle in South Korea. To achieve the goals of this study, we sampled and analyzed soil and water from 24 organic paddy plots and 11 conventional paddy plots in March, May, August, and October 2016. The results were analyzed using statistical analyses, including analysis of variance (ANOVA), cluster analysis, and principal component analysis. The ANOVA results showed that water content (WC), electrical conductivity (EC), organic matter (OM), and available phosphorus ($P_2O_5$) in soil varied significantly (p < 0.01) depending on the farming method. Higher OM, EC, and $P_2O_5$ of soil were observed in the conventional paddies than in the organic paddies. All soil properties, except pH and ammonium, depended on seasonal variation. Cluster analysis revealed that soil properties in May were distinctly separated from those in other seasons mainly due to basal fertilization. The principal component analysis distinguished the soil properties in different seasons, but such a distinction was not observed between the soil properties in organic and conventional paddies. Low contents of WC, OM, and total N were observed in March. High concentrations of nitrate and total P were observed in May, but these were low in August and October. The soils from October were also characterized by high concentrations of EC and $P_2O_5$. These results indicate that the sampling time for soil and water can significantly influence the evaluation of soil properties with different farming methods.