• 대기
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• 제20권1호
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• pp.37-47
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• 2010

The methods measuring the precipitation drop size distribution(hereafter referred to as DSD) at Cloud Physics Observation System (CPOS) in Daegwallyeong are to use PARSIVEL (PARticle SIze and VELocity) disdrometer (hereafter referred to as PARSIVEL) and Micro Rain Radar (hereafter referred to as MRR). First of all, PARSIVEL and MRR give good correlation coefficients between their rain rates and those of rain gage: $R^2=0.93$ and 0.91, respectively. For the DSD, the rain rates are classified in 3 categories (Category 1: rr (Rain Rate) ${\leq}0.5\;mm\;h^{-1}$, Category 2: $0.5\;mm\;h^-1$ < rr < $4.0\;mm\;h^{-1}$, Category 3: rr ${\geq}4\;mm\;h^{-1}$). The shapes of PARSIVEL and MRR DSD are relatively most similar in category 2. In addition, we retrieve the vertical rain rate and liquid water content from MRR under melting layer, calculated by Cha et al's method, in Daegwallyeong ($37^{\circ}41{\prime}N$, $128^{\circ}45^{\prime}E$, 843 m ASL, mountain area) and Haenam ($34^{\circ}33^{\prime}N$, $126^{\circ}34^{\prime}E$, 4.6 m ASL, coast area). The vertical variations of rain rate and liquid water content in Daegwallyeong are smaller than those in Haenam. We think that this different vertical rain rate characteristic for both sites is due to the vertical different cloud type (convective and stratiform cloud seem dominant at Haenam and Daegwallyeong, respectively). This suggests that the statistical precipitation DSD model, for the application of weather radar and numerical simulation of precipitation processes, be considered differently for the region, which will be performed in near future.

• Applied Biological Chemistry
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• 제38권2호
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• pp.129-134
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• 1995

수산가공부산물인 어류껍질로부터 식용으로 이용 가능한 고품질의 젤라틴을 제조할 목적으로 알코올처리에 의한 찰가자미류껍질 젤라틴의 제조를 시도하였고, 아울러 제조한 젤라틴을 목적에 맞게 효율적으로 식품산업에 이용하기 위해 필요한 몇가지 기능 특성도 검토하였다. 알코올처리 조건은 추출 및 탈색 처리한 찰가자미류껍질 젤라틴용액에 최종농도가 30%가 되도록 에탄올을 가하고 $0^{\circ}C$에서 12시간동안 분별침전한 젤라틴의 품질이 가장 우수하였고, 이 때의 겔강도, 졸화온도, 겔화온도 및 수율은 각각 223.0 g, $17.7^{\circ}C$, $12.0^{\circ}C$ 및 5.1%로서 에탄올 무처리한 젤라틴에 비해 물리적 특성이 개선되었으나 가축껍질에서 추출한 시판 젤라틴에 비하여 물리적 특성이 낮아 겔화제 등으로 이용하기에는 미흡하였다. 그러나 기능성의 경우 에탄올 처리한 어류껍질 젤라틴이 에탄올 무처리한 어류껍질 젤라틴에 비하여 용해도는 약간 낮았지만 보수력, 지방흡수력, 유화성 및 유화안정성, 거품성 및 거품안정성 등은 훨씬 높았고, 뿐만 아니라 시판되는 가축껍질 젤라틴에 필적하는 수준이었다. 따라서 겔화성 이외에의 기능성을 고려한 식품가공소재로서 에탄올로 처리한 찰가자미껍질 젤라틴을 사용하면 제품의 기능 특성은 다소 향상되리라 판단되었다.

• 한국농림기상학회지
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• 제8권4호
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• pp.270-274
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• 2006

본 연구에서 고안 설계한 적설 관측용 수위 센서는 야외에서 일 변화량은 0.1 mm 내외의 적은 양의 오차를 기록하여 강설관측 센서로 적합한 것으로 판명되었으며, 실내 검정 결과 기상청에서 요구하고 100 mm의 강수 검정범위에 대해서 1%이하의 신뢰성 있는 검정결과를 나타내어 강설량 관측에 적합한 것으로 판명되었다. 또한 $-20^{\circ}C$의 테스트에서도 0.1 mm에 해당하는 아주 작은 변화 값을 타나내어 겨울철 야외환경에도 적합한 것으로 판명되었다. 깔때기가 없으며 수수구의 크기에 제한을 받지 않는 새로운 강수 관측구조는 적은 양의 강설관측이 가능하여 겨울철 예보에 필요한 레이다. 영상과 위성 영상에 의한 강설 연구와 해석에 많은 도움을 줄 수 있을 것이다. 또한 적설상당수량 관측이 가능하여 수자원 분야의 연구에도 많은 도움이 될 수 있다. 부동액을 사용하므로 고체 상태의 강설에 대해서 직접 관측이 가능하여 강설 관측에 있어 문제점으로 지적이 되고 있는 신적설 관측의 어려움을 해결할 수 있으며, 추후 야외 관측용 모델을 제작하여 야외 환경에서 여타 장비들과 비교 실험을 통해서 성능을 검정하고 개선할 계획이다.

• Corrosion Science and Technology
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• 제2권3호
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• pp.117-126
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• 2003

Due to excellent corrosion resistance and mechanical properties, austenitic stainless steel is widely used as the material for chemical plants. nuclear power plants, and food processing facilities. But, the zone affected by heat in the range of 400 to $800^{\circ}C$ during welding loses corrosion resistance and tensile strength since Cr-carbide precipitation like $Cr_{23}C_6$ forms at the grain boundary and thereby takes place the intergranular corrosion. In this study, AISI 304 stainless steel with the added Nb of 0.3 to 0.7 wt% was solutionized at $1050^{\circ}C$ and sensitized at $650^{\circ}C$. Specimen was welded by MIG. The phase and the microstructure of the specimens were examined by an optical microscope, a scanning electron microscope, and a x-ray diffractometer. The corrosion characteristics of specimens were tested by electrolytic etching and by double loop electrochemical potentiokinetic reactivation method(EPR) in the mixed solution of 0.5M $H_2SO_4$ + 0.01M KSCN. The melting zone had dendritic structure constituted of austenitic phase and $\delta$-ferrite phase. Cr carbide at the matrix did not appear, as Nb content increased. At the grain boundaries of the heat affected zone, the precipitates decreased and the twins appeared. The hardness increased, as Nb content increased. The hardness was highest in the order of the heat affected zone>melted zone>matrix. According to EPR curve, as the Nb content decreased, the reactivation current density(Ir) and the activation current density(la) were highest in the order of the melted zone

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.137-137
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• 2021

In this study we aimed to enhance streamflow prediction skill of a land-surface hydrological model, WRF-Hydro, over one of the snow dominated catchments lies in Himalayan mountainous range, Astore. To assess the response of the Himalayan river flows to climate change is complex due to multiple contributors: precipitation, snow, and glacier melt. WRF-Hydro model with default glacier module lacks generating streamflow in summer period but recently developed WRF-Hydro-CROCUS model overcomes this issue by melting snow/ice from the glaciers. We showed that by implementing WRF-Hydro-CROCUS model over Astore the results were significantly improved in comparison to WRF-Hydro with default glacier module. To constraint the model with the observed streamflow we chose 17 sensitive parameters of WRF-Hydro, which include groundwater parameters, surface runoff parameters, channel parameters, soil parameters, vegetation parameters and snowmelt parameters. We used Dynamically Dimensioned Search (DDS) method to calibrate the daily streamflow with the Nash-Sutcliffe efficiency (NSE) being greater than 0.7 both in calibration (2009-2010) and validation (2011-2013) period. Based on the number of iterations per parameter, we found that the parameters related to channel and runoff process are most sensitive to streamflow. The attempts to address the responses of the streamflows to climate change are still very weak and vague especially northwest Himalayan Part of Pakistan and this study is one of a few successful applications of process-based land-surface hydrologic model over this mountainous region of UIB that can be utilized to have an in-depth understanding of hydrological responses of climate change.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.46-46
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• 2011

Severe sediment erosion during floods occur disaster and economic losses, but general sediment erosion is basic mechanism to move sediment from upstream to downstream river. In addition, it is important process to change river form. Check dam, which is constructed in mountain stream, play a vital role such as control of sudden debris flow, but it has negative aspects to river ecosystem. Now a day, check dam of open type is an alternative plan to recover river biological diversity and ecosystem through sediment transport while maintaining the function of disaster control. The purpose of this paper is to verify sediment erosion progress of river bottom and bank as first step for river restoration after dam slit by cross-sectional shear stress and critical shear stress. Study area is upstream reach of slit check dam in mountain stream, named Wasada, in Japan. The check dam was slit with two passages in August, 2010. The transects were surveyed for four upstream cross-sections, 7.4 m, 34 m, 86 m, and 150 m distance from dam in October 2010. Sediment size was surveyed at river bottom and bank. Sediment of cobble size was found at the wetted bottom, and small size particles of sand to medium gravel composed river bank. Discharge was $2.5\;m^3/s$ and bottom slope was 0.027 m/m. Excess shear stress (${\tau}_{ex}$) was calculated for hydraulic erosion by subtracting the values of critical shear stress (${\tau}_{c}$) from the value of shear stress (${\tau}$) at river bottom and bank (${\tau}_{ex}=\tau-{\tau}_c$). Shear stress of river bottom (${\tau}_{bottom}$) was calculated using the cross-sectional shear stress, and bank shear stress (${\tau}_{bank}$) was calculated from the method of Flintham and Carling (1988). $${\tau}_{bank}={\tau}^*SF_{bank}((B+P_{bed})/(2^*P_{bank}))$$ where $SF_{bank}=1.77(P_{bed}/p_{bank}+1.5)^{-1.4}$, B is the water surface width, $P_{bed}$ and $P_{bank}$ are wetted parameter of the bed and bank. Estimated values for ${\tau}_{bottom}$ for a flow of $2.5\;m^3/s$ were lower as 25.0 (7.5 m cross-section), 25.7 (34 m), 21.3 (86 m) and 19.8 (150 m), in N/$m^2$, than critical shear stress (${\tau}_c=62.1\;N/m^2$) with cobble of 64 mm. The values were insufficient to erode cobble sediment. In contrast, even if the values of ${\tau}_{bank}$ were lower than the values for ${\tau}_{bottom}$ as 18.7 (7.5 m), 19.3 (34 m), 16.1 (86 m) and 14.7 (150 m), in N/$m^2$, excess shear stresses were calculated at the three cross-sections of 7.5 m, 34 m, and 86 m distances compare with ${\tau}_c$ is 15.5 N/$m^2$ of 16mm gravel. Bank shear stresses were sufficient for erosion of the medium gravel to sand. Therefore there is potential to erode lateral bank than downward erosion in a flow of $2.5\;m^3/s$. Undercutting of the wetted bank can causes bank scour or collapse, therefore this channel has potential to become wider at the same time. This research is about a potential of sediment erosion, and the result could not verify with real data. Therefore it need next step for verification. In addition an erosion mechanism for river restoration is not simple because discharge distribution is variable by snow-melting or rainy season, and a function for disaster control will recover by big precipitation event. Therefore it needs to consider the relationship between continuous discharge change and sediment erosion.