• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.3
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• pp.230-240
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• 2009

The ESCORT model is applied at Mokpo coastal zone to analyze the effect of fresh water discharge released from the gates of the Youngsan River sea-dyke. Applicability and validity of both 2-D and 3-D hydrodynamic modules could be guaranteed by simulating hydrodynamic feature with ebb dominance characteristics. Then, effects of the released discharge on the hydrodynamics are investigated. And analysis of the effects on diffusion phenomena show that 3-D model is essential for such diffusion modelling. Moreover, vertical salinity distributions near the gates are examined, and the influence range of fresh water is also estimated, which shows that dilution of fresh water is going on slowly because of poor flushing.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.419-423
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• 2015

The flowing caused by artificial upwelling structure occurs ascending water flowing and vortex of rear side. In this moment, plentiful nutrient in the bottom water moves to the surface of the water and makes those plankton and fishing ecology promoted so that the fishing productivity can be enhanced. In this study, the changes of the upwelling flowing is included in consideration of the conditions of stratification by using CFD. In the conclusion, the closer upwelling effect is from the artificial upwelling structure, the better effectiveness comes out. Regardless of the conditions of stratification, only the upwelling feature from the bottom to the surface was shown up. But considering the conditions of stratification, the repeated flowing feature between upwelling and downwelling was verified.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.646-646
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• 2015

임진강은 북한지역이 유역면적의 60%에 달하고 2000년대 초부터 북한의 4월5일 댐과 황강댐과 남한의 군남과 한탄강 홍수조절지로 인해 물의 흐름과 강의 모습이 급격히 변화하고 있다. 기후변화 측면에서도 한반도 중부지역으로 기온 증가와 계절별 유출량, 특히 봄철의 유출량 감소가 전망되는 지역이다. 임진강 본류 유량 감소는 북한 측의 영향은 자료가 전무하고, 남측에서는 횡산, 군남 등 일부 수위표 자료만이 가용한 수준이다. 현재까지 자료로 보면, 2014년에 연강수량이 예년의 50% 수준이었던 점이 본류 유량 감소의 주 원인이었고, 다른 원인은 군남 홍수조절지의 저류 수준이 그 직하류 유량 변동에 영향을 미치고 있는 것으로 나타났다. 유량감소 영향은 2014년 장단반도 일대 파주지역에서 가장 극심하였고, 유량 감소와 연동된 염도 변동이 가중되면서 모내기철 농업용수 공급이 어려웠다. 유량 감소 피해는 농업보다 어업분야에서 그 체감 정도가 극심하였고 경제적 피해도 심각했다. 체감하는 주민들 대부분은 댐 건설 이후 하도와 수변의 침식과 퇴적 등 하천의 역동성이 변화함을 느끼고 있고, 그로 인해 어업과 수생태계가 지속가능성하지 않을 거라는 우려가 팽배해 지고 있다. 지금까지 파악된 임진강 유량 감소의 수준과 피해 정도가 앞으로 어떻게 변화될지, 그 수준, 심각성, 경제적 피해와 환경적 가치나 서비스 제약 등에 대해 면밀한 검토가 필요하다. 하천의 흐름이 단절, 변경되어 야기되는 직간접적 변화를 인정하고 이를 지속가능하게 보완할 방안이 논의되어야 할 시점이다. 무엇보다 수환경과 수생태계의 변화 정도를 파악하기 위한 장기모니터링이 절실하고 그 결과의 해석을 통해 새로운 대안을 모색해 나가야 할 것이다. 2014년 혹은 그보다 심각한 강우량 감소 재현을 대비하고, 기후변화와 남북한 문제까지를 고려한 임진강 관리가 필요하다. 단기적으로는 농업용수 공급을 위해 하천 본류는 물론 가용한 저수지, 지하수 등 대체 자원을 적극 활용하는 등 비상급수체계를 운영해야 한다. 그러나 기후변화 등 장래 여건이 수량 압박을 가중할 것을 고려, 유역의 용수수급과 변동성에 대한 재평가가 시급하다. 보다 면밀한 평가는 횡산, 군남 등을 포함한 남북유역의 상황을 장기모니터링하고 북한 지역의 기초 자료 확보를 위한 여건을 마련해야 한다. 보다 합리적 분석을 위해 임진강 수계와 유역을 국가하천에서 국제하천으로 격상하는 방안이나, DMZ와 연계한 남북공유 하천으로 관리하는 등의 새로운 대안이 절실하다. 국제수로협약 등을 통해 접경지역의 하천관리를 공동으로 하고 있는 외국 사례의 시사점도 접목해 볼 필요가 있다. 무엇보다 임진강 관리를 좀 더 제도적 틀안에서 확립해 가기 위해 지역정부로서의 경기도, 중앙정부 주체로 국토부와 통일부가 보다 협력적인 관계 정립과 역할 배분을 논의해야 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.787-792
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• 2022

In winter, the excessive use of deicing salt deteriorates concrete pavement durability. To reduce the amount of deicing salt used, phase-change materials (PCMs) potentially offer an alternative way to melt snow through their latent heat storage characteristics. In this research, thermal energy storage concrete was developed by using PCM-impregnated expanded clay as 50 % replacement to normal aggregate by volume. In addition, to improve the thermal efficiency of PCM lightweight aggregate (PCM-LWA)-incorporated concrete, multi-walled carbon nanotubes (MWCNTs) were incorporated in proportions of 0.10 %, 0.15 %, and 0.20 % by binder weight. Compressive strength testing and programmed thermal cycling were performed to evaluate the mechanical and thermal responses of the PCM-LWA concrete. Results showed a significant strength reduction of 54 % due to the PCM-LWA; however, the thermal performance of the PCM-LWA concrete was greatly improved with the addition of MWCNTs. Thermal test results showed that 0.10 % MWCNT-incorporated concrete had high thermal fatigue resistance as well as uniform heat flow, whereas specimens with 0.15 % and 0.20 % MWCNT content had a reduced thermal response due to supercooling when the ambient temperature was varied between -5℃ and 10℃.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.2
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• pp.178-184
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• 1992

The changes in contents of chlorophyll and free proline in the seedling leaves of ten rice cultivars as affected by salt stress were checked in order to obtain the basic information on the judgement of the degrees of salt injury. The difference in salt injury among the cultivars was clearly observed about 25 days after 6% salt treatment. Chlorophyll content was decreased in both Gayabyeo and Taebaegbyeo for 14 days after different salt treatment as salt concentration was increased and the decreased tendency was much higher in Taebaegbyeo than in Gayabyeo over 0.4% salt concentration. Chlorophyll content in Gayabyeo after 0.6% salt treatment was decreased slowly, while in Taebaegbyeo, deminished very rapidly as time progressed, therefore it decreased by about 16% in Gayabyeo and 67% in Taebaebyeo compared to the control at 20 days, respectively. The relationship between chlorophyll content and the degrees of salt injury in ten rice cultivars showed significant negative correlation at 10 day after 0.6% salt treatment. Free proline content in Gayabyeo was increased gradually for 14 days after different salt treatment as salt became higher, while in Taebaebyeo, it was increased rapidly under 0.6% but rather decreased under 0.8% salt concentration. Particularly, it was much higher Taebaegbyeo than in Gayabyeo under salt concentration from 0.4 to 0.6%. Free proline content in Gayabyeo after 0.6% salt treatment was increased from 15 days, on the other hand in Taebaegbyeo, it was increased from 5 days, but rather decreased from 20 days, and it was 6 times higher in Taebaegbyeo than in Gayabyeo at 10 days. There was significant positive correlation between free proline content and the degrees of salt injury in ten rice cultivars at 10 days after 0.6% salt treatment. From the above results, chlorophyll and free proline content may be used as an indicative character of intensity of salt stress as well as varietal difference in resistance to salt stress in the seedling stage.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.72.1-72.1
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• 2010

지금까지 연료전지 시스템의 효율을 극대화시키기 위한 기술들이 개발되어 왔는데, 대표적인 방법은 CHP(Combined Heat & power)와 FCT(Fuel cell & Turbine) Hybrid 시스템이다. 그러나 본 연구의 기술은 연료전지 배열을 이용한 Coanda 공기증폭기를 장착한 새로운 개념의 고효율 연료전지 시스템이다. 원래 공기 증폭기는 완만한 곡면 주위를 흐르는 유체가 곡면의 표면을 따라 흐름의 방향이 바뀌는 원리(Coanda Effect)를 이용한 장치로서, 소량의 고압유체를 구동 에너지원으로 사용하여 최고 20배에 해당하는 많은 양의 주변 유체를 빠른 속도로 이송시키는 역할을 한다. 문제는 고압의 유체원을 만드는 것인데, 본 연구에서는 발전용 연료전지 시스템의 배기가스를 활용하여 먼저 고압의 수증기를 발생시키고, 다음으로 고압의 수증기를 공기 증폭기의 구동원으로 사용함으로써 연료전지 시스템의 Air blower를 대체하는 것이다. 이러한 개념을 검증하기 위해서 고압의 스팀작동 Coanda 공기증폭기를 제작하여 선행실험을 진행하였다. 먼저 공기증폭기의 Gap 및 스팀압력에 따른 공기유량, 압력 등의 기본특성을 조사하였고, 출력 공기의 특성을 개선하기 공기증폭기의 형상 및 재료를 새롭게 설계하였다. 그리고 실제 시스템의 적용가능성을 알아보기 위해서, 예로 300kW급 용융탄산염 연료전지 발전시스템의 Air blower 대체가능성을 확인하였고, 배열이용 Coanda 공기증폭기를 활용한 고효율 연료전지 시스템의 개념설계를 수립하였다. 결론적으로 본 기술을 활용하면 연료전지 시스템의 최종 전기효율을 향상시킬 뿐 아니라는 시스템의 장기 신뢰성을 증대시키는 효과를 기대할 수 있다.

• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.604-610
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• 1995

The interaction between 3,3'-dipropyl oxacarbocyanine and poly(styrenesulfonate) has been studied by means of absorption and fluorescence spectroscopic methods. The results was interpreted by stacking model. The kinetic studies of the interaction between 3,3'-dipropyl oxacarbocyanine and poly(styrenesulfonate) were carried out by the absorption and fluorescence spectroscopic stopped-flow methods. The observed relaxation effect in DPC-PSS system was described quantitatively by assuming two relaxation processes. The dependence of rate of reaction on the salt concentration of the solution was also studied. The results are consistent with the two-step mechanism.

• 한국해양학회지
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• v.24 no.2
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• pp.96-108
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• 1989

Applying the numerical scheme developed by Semtner (1974), we investigate the circulation system in the Japan Sea in response to the air-sea interaction and the wind. In spite of blocking straits, resulting surface circulation pattern is similar to the schematic surface current chart introduced by Uda(1934) and Naganuma (1972); the northward flow along the Korean coast and the anticlockwise gyre in the northeastern part of the Japan Sea. Also the southward current flows along the Korean coast at depth of 100-200 m as similar to the North Korean Cold Current suggested by Kim and Kim (1983). And the sinking phenomenon of relatively saline water in the northeastern part of the Japan Sea is similar to the formation of the Japan Sea Proper Water.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.5
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• pp.565-573
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• 2015

The influencing factors to remove phosphate were evaluated by converter slag (CS). Experiments were performed by batch tests using different CS sizes and column test. Solutions were prepared at the different pH and concentrations. The maximum removal efficiency was obtained over 98% with the finest particle size, $CS_a$ within 2 hours in batch tests. The removal efficiency was increased in the order of decreasing size with same amount of CS for any pH of solutions. The adsorption data were well fitted to Freundlich isotherm. From the column experiment, the specific factors were revealed that the breakthrough removal capacity (BRC) $x_b/m_{cs}$, was decreased by increasing the influent concentration. The breakthrough time, tb was lasted shorter as increasing the influent concentration. The pH drop simultaneously led to lower BRC drop during the experimental hours. The relation between the breakthrough time and the BRC to influent concentration was shown in the logarithmic decrease. Results suggested that the large surface area of CS possessed a great potential for adsorptive phosphate removal. Consequently particle size and initial concentration played the major influencing factors in phosphate removal by converter slag.

• Membrane Journal
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• v.2 no.1
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• pp.59-66
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• 1992

The experimental studies were carried out on ultrafiltration of PEG #6000 and dextran 70T macromole¬cules. using an asymmetric cellulose acetate membrane in a cross flow plane type cell. Effects of pressure difference. feed concentration were studied on permeate flux and observed rejection for both the macromole¬cules. and the concentration polarization layer resistance $R_{b1}$ on permeate flux was analysed. The concentration polarization layer resistance $R_{b1}$ was correlated with the average macromolecule concen¬tration $C_{b1}$ in polarization layer. The resulting dimensionless correlation was expressed as : $\frac{R_{b1}}{{R_m}}=\alpha[\frac{\rho_{b1}}{C_{b1}}]^\beta$