• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.533-542
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• 2001

In order to establish drought policy, the estimation of drought period for each drought situation should be preceded. Non-linear Water Balance Model(NWBM) and palmer Drought Severity Index (PDSI) can be used for analysis of drought period. As a water balance method considering moisture transfer between land surface and atmosphere, NWBM can be used to estimate transition time between dry and wet period induced by stochastic fluctuations. PDSI is also water balance method to show drought severity comparing actual precipitation with climatically appropriate precipitation based on precipitation and potential evapotranspiration. In this study, the drought periods are estimated using NWBM and PDSI for the Han River Basin. The drought periods according to the soil moisture estimated by NWBS and the drought periods according to drought severity index estimated by PDSI show similar trend. The estimated drought period from extreme drought to wet condition for the Han River Basin is about 3years.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.57-65
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• 2014

For economic and technical reasons, it is difficult to obtain high quality undisturbed cohesionless samples, hence most researchers rely on preparing remolded and reconstituted representative samples of sandy soils. In this study, moist tamping, air pluviation, and dry deposition methods were applied to make remolded samples at similar relative densities. A series of isotropically consolidated drained tests were conducted with accompanied by measured elastic wave velocities in order to evaluate a difference between sample preparation methods and relative densities. For the elastic wave velocity measurements, piezoelectric elements were installed on the top and bottom cap of the triaxial device. The results showed that soil behavior relies on sample preparation methods, and that the trend of shear wave velocity was the same with volumetric strain behavior.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1777-1781
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• 2006

수자원장기종합계획 보고서 및 저수지운영상에서는 실측을 통해 자연유량을 산정하지 않고 간접적인 방법인 강우-유출모형을 이용하여 자연유량을 산정하고 있다. 그러나 일반적인 강우-유출모형의 검증은 인위적인 영향이 적을 것이라 판단되는 일부 특정지역을 대상으로 실시하며 이에 대한 결과를 전 유역에 동일하게 반영하였기 때문에 금강유역과 같은 대유역에서는 각 소유역별 유출특성이 반영되지 못하고 있는 실정이다. 따라서 본 연구에서는 모형의 안정성 고취를 위해 모형외적으로 강우, 생 공 농업용수 이용량 및 관측유량자료 등의 기본 수문자료에 대한 검 보정을 실시하였으며 모형내적으로는 적정매개변수의 선정을 위해서 토양습윤상태별 유출율, 침투량별 지하수 유입률, 지표수와 복류수 분리 등을 반복적인 수행과정을 걸쳐 적정한 매개변수를 산정하였으며 RRFS모형에 의한 일별 유출량산정 결과를 비교분석을 실시하여 모의유량의 신뢰도를 고취시킨 후 인위적인 요소를 모두 배제시켜 자연상태의 유출량인 자연유량을 산정하고자 한다.

• Korean Journal of Plant Resources
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• v.21 no.2
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• pp.144-147
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• 2008

This study was conducted to clarify the characteristics of seed germination and to promote the germination rate in Pollia japonica Thunb. that was pointed to protect by the Office of Forestry in 1997. It was better the germination rate and the growth of in the light than those of in the darkness. The seed germination of Pollia japonica showed the highest germination rate at $20^{\circ}C$ any other treated temperature. To increase the germination rate of Pollia japonica, it was conducted priming treatments and storage treatments at $4^{\circ}C$. Priming treatments using 1% NaOH, 1% KOH for 30min were effective compared to control, but soaking of 100mg/L GA3 for 24 hours, 1% NaOCl for 30min were not useful. It was higher in wet storage than in dry storage. Wet storage of seeds showed a germination rate with 95.3% in 90-day treatment, which improved 55.3% than dry storage in 90-day.

• Conservation Science in Museum
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• v.2
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• pp.19-25
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• 2000

In order to studies proper conservation treatment condition of waterlogged archaeological wood excavated from wetland in Shinchang-dong, Kwangju, 2 kinds of wooden objects were treated with PEG(Poly-Ethylene Glycol), sucrose and lactitol and their size stability and relative humidity were analyzed and compared each other. The result showed that Quercus spp. had the highest size stability in 2 Step-PEG treatment using PEG#200(MW:200) and PEG#4000 (MW:3,350) and Acer spp. was the highest in treatment using only PEG#4000. In relative humidity test after treatment 2 Step-PEG treatment showed the lowest size stability. In the meantime, sucrose and lactitol-treated sample was fast for penetration, sucrose-treated sample showed a sharp increase for penetration in as high as 84% humidity condition and medicine flew out a lot and lactitol-treated sample got enlarged with fine cracking(splitting) in relative humidity test. In relative humidity test, the samples showed cracking(splitting) in all treatment materials except for 2 Step-PEG treatment. This study showed that waterlogged archaeological wood excavated from Shinchang-dong had the highest size stability and highest adaptation to humidity change in case of treatment with 2 Step-PEG.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.87-94
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• 2017

In the nuclear power plant, the steel or polymer liner plates are adopted to prohibit the inner concrete surface from contacting with gas or liquid materials. If there is an accident, the plate may be damaged, and, in this case, concrete shall have the final responsibility to safety requirements. In this paper, an experimental research was carried out to investigate the effects of construction joint and wet and loading conditions on the permeability of concrete. The test results showed that, under a construction joint in the wet condition, leakage of gas pressure has been started from $1kg/cm^2$. However, when there are no construction joints, it is initiated from $2kg/cm^2$. In addition, under the air dried and unloading condition, regardless of with or without the presence of the construction joint, since the gas passage that exist in concrete is constant, leakage has a constant tendency to increase. Finally, under the loading condition, as described in Reference 1, since leakage is inversely proportional to the thickness of the wall, and, considering the wall thickness of the actual plant, it is found that there will not be no problem in the sealing of the gas.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.639-646
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• 2007

This study performed several tests for the durability of the concrete coated with nano synthesis ceramics which do not contain volatile organic compounds harmful to environment. The tests were adhesion test on dry and humid concrete, SEM test, MIP analysis, carbonation, chloride diffusion by electronic facilitation, freezing-thawing resistance, alkaline resistance, and brine resistance test. In the adhesion test on dry and humid concrete, nano synthesis ceramics coating produced the highest results among all the coatings tested. Nano synthesis ceramics adhered solidly on the concrete surface. The adhesive strength seemed to result from the hydrogen bond between nano synthesis ceramics which are inorganic and generated by hydrolysis and re-condensation reaction and the concrete's hydrates such as calcium silicate aluminate or calcium silicate hydrate. SEM test and MIP analysis results show surface structure with finest crevices pore in the nano synthesis ceramics coating applied concretes. In the carbonation, chloride diffusion, and freezing-thawing resistance tests, the concretes with nano synthesis ceramics coating indicated the best results. Based on these test results, further progress in application of nano synthesis ceramics coatings to various concrete structures including costal structures and sewerage arrangements can be expected.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.79-89
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• 2019

The field measurement and laboratory experiment were conducted to investigate the effect of reducing the surface temperature of the functional aspect of the heat island phenomenon of the permeable block which is made the recycled synthetic resin rather than the existing concrete permeable block. Field measurement was taken for 3 days in consideration of dry condition and wet condition and laboratory experiment was divided into dry condition, rainfall simulating condition, and wetting condition. The variations of temperature and the evaporation rate of water moisture content after experiment were confirmed. As a result of field measurement, it is confirmed that the surface temperature decreases due to the difference in albedo of the pore block surface rather than the cooling effect due to the latent heat of vaporization. The evaporation of moisture in a dry state where drought persisted or a certain level of moisture was not maintained in the surface layer. As a result of laboratory experiment, resin permeable block gives higher surface temperature when it is dry condition than concrete permeable block, but the evaporation of water in the pore is kept constant by capillary force in rainfall simulation condition, and higher temperature reduction rate. As a result of measuring the evaporation rate after laboratory experiment, it is confirmed that the effect of reducing temperature is increased as the evaporation rate of water is higher. Based on these results, correlation formula for evaporation rate and temperature reduction rate is derived.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.506-513
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• 2021

The durability and safety of reinforced concrete structures significantly depend on the reinforcement conditions, concrete cover thickness, cracks, and concrete strength. There are two ways to accurately determine the information on reinforcing bars embedded in concrete - the local destructive method and the non-destructive rebar detection test. In general, the non-destructive rebar detection tests, such as the electromagnetic wave radar method, electromagnetic induction method, and radiation method, are adopted to avoid damage to the structural elements. The moisture content and temperature of concrete affect the dielectric constant, which is the electrical property of concrete, and cause interference in the non-destructive rebar detection test results. Therefore, in this study, the effects of the electromagnetic wave radar method and electromagnetic induction method have been analyzed according to the temperature and surface moisture content of concrete. Due to the technological advancement and development of equipment, the average error rate was less than 5% in the specimens at 24℃, irrespective of their operating principles. Among the tested methods, the electromagnetic induction method showed very high accuracy. The electromagnetic wave radar method indicated a relatively small error rate in the dry state than in the wet state, and exhibited a relatively high error rate at high temperatures. It was confirmed that the error could be reduced by applying the electromagnetic wave radar method when the temperature of the probe was low and in a dry state, and by using the electromagnetic induction method when the probe was in a wet state or at a high temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.303-311
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• 2009

In this study, weakly cemented sand was cured at air dry condition with different periods (3, 7, 14, 21, 28 days) and its unconfined compressive strength was evaluated. As a result, the strength of specimens with low cement ratios such as 4 and 8% increases until 7 days curing but, after 7 days, their strength continuously decreases. The strength of specimens with relatively high cement ratios such as 12 and 16% increases up to 7 days curing and then stays almost constant until 21 days. After 21 days curing, their strength suddenly dropped down, which is much lower than the strength of 3 days curing specimen. A cemented sand and gravel called CSG, which is highly permeable, could be exposed to repetitive drying and wetting conditions due to rainfall or groundwater table change during curing. In this study, the weakly cemented sand is exposed to repetitive drying and wetting and then its unconfined compressive strength was evaluated. As a result, the strength of a specimen with 27 days drying condition following 1 day wetting was at maximum 35% lower than the one cured under 28 days drying. The strength degradation due to wetting decreases as a cement ratio increases. However, the strength of a specimen with repetitive drying and wetting increases as the number of wetting increases until 3 cycles. After 3 cycles of drying and wetting, the rate of strength increase decreases due to an insufficient water for hydration or stays constant. If the sufficient water supply is provided to cemented sand during curing, the target or design strength increase can be achieved. Otherwise, the strength degradation due to wetting should be considered at the design stage.