• Corrosion Science and Technology
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• 제20권6호
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• pp.325-334
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• 2021

In the open system (vessel and pipe), the maximum corrosion rate of carbon steel at ca. 80 ℃ was obtained due to the decrease of dissolved oxygen by increasing the solution temperature. Effect of temperature on the cavitation damage can be explained through several mechanisms. Moreover, when cavitation occurs on the surface of metal and alloys, whether cavitation is erosion or corrosion is still controversial. This work focused on the effect of solution temperature on the corrosion of carbon steel under cavitation in an open system, Tests were performed using an electrochemical cavitation corrosion tester in 3.5% NaCl solution and the effect of solution temperature of carbon steel was discussed. Cavitation corrosion rate can be increased by cavitation, but when the temperature increases, a dissolved oxygen content reduces at a very high speed and thus the maximum cavitation corrosion temperature changed from 80 ℃ to 45 ℃. Below the maximum cavitation temperature, the electrochemical effect was more dominant than the mechanical effect by increasing temperature, but over the maximum cavitation temperature, the mechanical effect was more dominant than the electrochemical effect by increasing temperature.

• 한국습지학회지
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• 제23권4호
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• pp.287-295
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• 2021

댐 저수지(dam reservoir wetland)나 농업용 저수지 습지(irrigation reservoir wetland) 같은 시설물은 준공되고 시간이 지남에 따라 침식(erosion), 유사이송(sediment transport), 그리고 유사가 침전(sediment deposition)되어 퇴적이 발생하게 된다. 장기간 유사가 퇴적되면 홍수 및 가뭄 조절 기능에 영향을 주기 때문에 퇴적 문제는 저수지 습지의 유지 관리를 위해 매우 중요하다. 그러나 퇴사에 관한 연구는 가용 자료의 부족으로 인해 주로 경험공식에 의해 추정되어 왔다. 본 연구의 목적은 실측자료 및 경험공식과 더불어 다중회귀모형을 개발하여 비퇴사량(sediment deposition rate)을 산정하고 비교하고자 하였다. 또한, 저수지 습지의 퇴사(reservoir wetland sedimentation) 및 노후화로 인해 2020년 긴 장마에 따른 홍수피해가 발생한 64개소의 저수지 습지에 적용하여 잠재적인 붕괴 원인을 파악하고자 하였다. 대상 저수지는 실측 정보가 있는 한국의 경상남도 밀양시(Miryang city, Gyeongsangnam province)에 위치한 가곡(GaGog) 저수지 등 10개소를 선정하였다. 저수지 유효저수용량 실측자료를 이용하여 비퇴사량을 산정하였고 기존에 개발된 총 4가지 경험공식과 물리적/기후적 특성 등을 고려한 다중회귀모형을 개발하여 비퇴사량을 산정하였다. 비퇴사량 산정 결과, 본 연구에서 개발한 다중회귀모형의 오차가 0.21(m³km²/yr)부터 2.13(m³km²/yr)으로 가장 낮았다. 따라서 다중회귀모형에 의해 추정한 비퇴사량을 토대로 저수지 습지의 유효저수용량에 대한 변화를 분석하였는데 유효저수용량이 0.21(%)부터 16.56(%)까지 감소한 것으로 파악되었다. 또한, 월류 피해가 발생한 저수지 습지의 비퇴사량은 파이핑 피해 등이 발생한 저수지의 비퇴사량 보다 상대적으로 높았다. 즉, 저수지 바닥에 비퇴사량이 축적되면 허용할 수 있는 유효저수용량이 부족해지고, 저수지의 홍수 및 가뭄 조절 능력이 감소되어 호우로 인한 저수지 붕괴 피해가 발생할 수 있다는 것이다.

• 한국지리정보학회지
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• 제9권4호
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• pp.81-94
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• 2006

본 연구에서는 도암댐 유역에서의 산림파편화에 따른 수(水)환경 영향을 평가하였다. 이를 위해서 Soil and Water Assessment Tool (SWAT) 모형을 이용하였다. 도암댐 유역에서 산림파편화에 따른 수환경 영향만을 평가하기 위해서는 먼저 기상변화에 따른 영향을 배제시켜야 한다. 1985년과 2000년 강수량 분석결과 계절별 강수량에 상당히 많은 차이가 나타나, 본 연구에서는 1985년 기상자료를 이용하여 산림파편화에 따른 수환경 영향을 평가하였다. 산림 파편화에 따른 영향은 시간적 공간적으로 변화하기 때문에 본 연구에서는 수환경의 시 공간적 영향을 분석하였다. 도암댐 수계중 산림파편화가 가장 많이 발생한 소유역에서는 산림파편화로 인하여 유출량이 겨울철, 봄철, 여름철, 가을철 각각 $8,366m^3/month$, $72,763m^3/month$, $149,901m^3/month$, 그리고 $107,109m^3/month$ 증가하였다. 이렇게 증가된 유출량으로 인하여 상당한 양의 토양유실이 발생하여 하천의 부영양화 등을 초래한 것으로 판단된다. 이러한 토양유실로 인하여 가장 많은 산림파편화가 일어난 소유역에서 겨울철, 봄철, 여름철, 그리고 가을철, 유사농도가 각각 5.448mg/L, 13.354mg/L, 20.680mg/L, 그리고 24.680mg/L 증가하였다. 봄철 유사농도가 많이 증가한 이유는 산림지역과는 달리 농경지에서의 봄철 융설로 인한 토양유실이 많이 발생하였기 때문이다. 여름철과 가을철 유사농도가 증가한 이유 또한 과거 산림지역이었던 곳이 산림파편화로 인하여 상당부분 농경지로 전환되었으며, 이 지역에서의 영농에 따른 토양유실 증가로 유사농도가 증가한 것으로 판단된다. 본 연구의 결과를 종합해 보면 홍수조절, 토양유실 저감, 수질 개선과 같은 산림 고유의 기능은 유역내 산림파편화로 인하여 매우 빨리 손실될 수 있다. 따라서 도암댐 유역 내에서 산림 파편화에 따른 부정적 영향을 최소화시키기 위해서는 복합적인 토지이용계획을 수립하여 이행되어야 한다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.443-444
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• 2002

The uniformity of field oxide is critical to isolation property of device in STI, so the control of field oxide thickness in STI-CMP becomes enormously important. The loss of field oxide in shallow trench isolation comes mainly from dishing and erosion in STI-CMP. In this paper, the effect of slurries on the dishing was investigated with both blanket and patterned wafers were selected to measure the removal rate, selectivity and dishing amount. Dishing was a strong function of pattern spacing and types of slurries. Dishing was significantly decreased with decreasing pattern spacing for both slurries. Significantly lower dishing with ceria based slurry than with silica based slurry were achieved when narrow pattern spacing were used. Possible dishing mechanism with two different slurries were discussed based on the observed experimental results.

• 환경영향평가
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• 제3권2호
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• pp.47-56
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• 1994

AGNPS model is an event-based model to analyze nonpoint-source and to examine potential water quality problems from agricultural watershed. This model uses a square grid-cell system to represent the spatial variability of watershed conditions, and simulates runoff, sediment, and nutrient transport for each cell. AGNPS model was applied on Yeonwha watershed, and the test results were compared with the measured data for runoff volume, peak runoff rate, suspended solids, and phosphorus concentration. The watershed of 278.8 ha was divided into 278 cells, each of which was 1 ha in size. The coefficients of determination for runoff volume and peak flow were (0.893 and 0.801 respectively from regression of the estimated values on the measured values. The concentration of suspendid solid was increased but decreased that of phosphate with runoff volume.

• Ocean Systems Engineering
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• 제5권4호
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• pp.319-329
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• 2015

Submerged breakwaters are used to prevent shore line erosion and sediment transportation. One of their advantages is low visual impact. In this paper, the effects of discontinuous submerged breakwaters over water surface elevation was numerically studied considering the extended Boussinesq equations as governing equations using MIKE21 software. The result of discontinuous breakwater was compared with a beach without breakwater. The results showed that the gap dramatically effects on surface elevation from shore line to offshore. It is also evident from results that with approaching the center of the gap, fluctuation of surface elevation is generated. It is because of passing longshore currents towards offshore through the gap which leads to an increase in sediment transportation rate. Nevertheless, transferring water mass from breakwater gap results in powerful rip currents leading to high changes on longshore wave profile.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.65-71
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• 2010

The plugging rate of reheater tubes of Wolsung unit 1 nuclear power plant has been increased by corrosion and erosion since 1990. As the dimensions of the new first stage reheater bundle tubes which were supplied by Hanjung company to replace were different from old one, numerical calculations are carried out for flow and heat transfer in the reheater bundle tubes of the N.P.P. Numerical calculations consists of thermal performance, drain line pressure drop, flow change by pressure drop of line, stress analysis of finned tubes and analysis of flow induced vibration. Computational analysis using heat transfer research institute program is adopted to verify the results of the numerical calculations. It contains the evalution of performance in the system with view to location of the new reheater bundle and it shows the differences between the numerical calculation results and heat transfer research institute program output.

• 한국세라믹학회지
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• 제46권1호
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• pp.30-34
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• 2009

A Sand blasting technology has been used to address via and trench processing of glass wafer of optic semiconductor packaging. Manufactured sand blast that is controlled by blast nozzle and servomotor so that 8" wafer processing may be available. 10mm sq test device manufactured by Dry Film Resist (DFR) pattern process on 8" glass wafer of $500{\mu}m's$ thickness. Based on particle pressure and the wafer transfer speed, etch rate, mask erosion, and vertical trench slope have been analyzed. Perfect 500 um tooling has been performed at 0.3 MPa pressure and 100 rpm wafer speed. It is particle pressure that influence in processing depth and the transfer speed did not influence.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.98-101
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• 2005

The mechanical and thermal properties of PAN-based/Rayon-based carbon fabrics interply hybrid composite materials have been studied. Mechanical properties was improved with increasing amount of continuous PAN-based carbon fabrics. The erosion rate was calculated through torch test. The thermal conductivity of hybrid of spun PAN-based/continuous rayon-based carbon fabric is lower than others.

• 수산해양기술연구
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• 제40권2호
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• pp.155-160
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• 2004

Water jet trajectories and velocity deficits from a high pressurize nozzles were experimentally observed. In this article, several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA (Phase Doppler Particle Analyzer) system. The results indicated that trajectories along the centerline regardless of their momentum has its potential core region. However, the phenomena from the peripheral part need to be meticulosly considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.