Surface morphologies and wetting properties of layer-by-layer assembled films of polyelectrolytes with bimodal molecular weight distribution

성충현,최수빈,김진경 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.7

Layer-by-layer (LbL) assembly has been rigorously applied to the construction of superhydrophobic surfaces. Typically, this involves generating a hierarchical porous structure which is then coated with a low surface energy compound. In this study, a porous LbL film was constructed from poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) using a PAA solution with a bimodal molecular weight distribution. This solution was prepared by mixing two PAA solutions with different average molecular weights (100,000 and 15,000 g/mol). The mixing ratio was adjusted for fine control of the porous structure, which was induced by acid treatment at pH 2.0-2.4. Generally, surface pore structure was weakened as the 15,000 g/mol PAA ratio increased. However, the surface roughness decreased or increased as the 15,000 g/mol PAA ratio increased depending on the acid treatment pH and time. The porous LbL films were coated with fluorinated silane to make them hydrophobic. When the acid condition was pH 2.4 for 5min, the water contact angle decreased significantly from 132o to minimum of 105o as the amount of 15,000 g/mol PAA increased. However, at pH 2.0 for 5min, the water contact angle decreased smaller from 148o to 139o as the amount of 15,000 g/mol PAA increased.

제주도 밭작물의 농업용수 재이용 타당성 평가

성충현,강문성,장태일,박승우,이광야,김해도,Seong, Choung-Hyun,Kang, Moon-Seong,Jang, Tae-Il,Park, Seung-Woo,Lee, Kwang-Ya,Kim, Hae-Do 한국농공학회 2009 한국농공학회논문집 Vol.51 No.1

The objective of this study is to assess the feasibility of wastewater reuse for the vegetable farming. The study region, about 250 ha in size, is located on the west coast of Jejudo, Korea. Major agricultural products of the study area are the cabbage, broccoli, garlic and onion. To confirm the feasibility of wastewater reuse, the drought duration and the water requirement analysis were conducted respectively. The average annual precipitation of the study region (1,121 mm) was smaller than that of Jeju island (1,975 mm). The drought duration for a ten-year return period in October through November was more than 20 days. The water requirement for irrigation was calculated by the FAQ Penman-Monteith method which took into account the cultivated crops, planting system, and meteorological conditions of the study region. The water requirement for a ten-year return period was estimated 4.7 mm/day and the water demand for irrigation was $4,584\;m^3/day$. As a result, the irrigation water for the crops was insufficient during their breeding season, especially in October through November. Thus, the result indicated that the study region required the alternative water supply such as wastewater reuse during the non-rainy season. As drought continues to place considerable stress on the availability of fresh water supplies in the study region, irrigation with reclaimed wastewater will play an important role in helping to meet future water demands.

하수처리수의 농업용수 재이용에 따른 포장단위 수질영향 분석

성충현,김성재,김성민,김상민,Seong, Choung-Hyun,Kim, Sung-Jae,Kim, Sung-Min,Kim, Sang-Min 한국농공학회 2011 한국농공학회논문집 Vol.53 No.4

The purpose of this study was to analyze the water quality change when wastewater applied to study paddy fields. CREAMS-PADDY (Chemical, Runoff and Erosion from Agricultural Management System) model was used to estimate the field-scale water quality. Simulated results were compared with observed data monitored from Byeongjeom study paddy fields which is located near the Suwon sewage treatment plant in Gyeonggi-do. Significance analysis was performed for the three different irrigation water quality level and five fertilizer reduction scenarios using LSD (Least Significant Difference) and DMRT (Duncan's Multiple Range Test). Total nitrogen was found to be significant for both irrigation water quality level and fertilizer reduction while total phosphorus was not. Annual drainage load for total nitrogen was reduced by 66~92 % compared to irrigation load when treated wastewater irrigated to study paddy fields from 2002 to 2007. Total phosphorus was reduced by 70~86 %.

HSPF의 대규모 유역 적용: 체사픽만(Chesapeake Bay) 유역모형

성충현 한국농공학회 2016 韓國農工學會誌 : 전원과 자원 Vol.58 No.2

염분수지 및 EFDC 모형을 이용한 간척 담수화호 염도변화모의

성충현,Seong, Choung Hyun 한국농공학회 2014 한국농공학회논문집 Vol.56 No.6

Forecasting salinity in an estuary reservoir is essential to promise irrigation water for the reclaimed land. The objective of the research was to assess salinity balance and its temporal and spatial variations in the Iwon estuary reservoir which has been issued by its high contents of salinity in spite of desalination process for four years. Seepage flows through the see dikes which could be one of possible reason of high salinity level of the reservoir was calculated based on the salinity balance in the reservoir, and used as input data for salinity modeling. A three-dimensional hydrodynamic model, Environmental Fluid Dynamics Code (EFDC), was used to simulate salinity level in the reservoir. The model was calibrated and validated based on weekly or biweekly observed salinity data from 2006 to 2010 in four different locations in the reservoir. The values of $R^2$, RMSE and RMAE between simulated and observed salinity were calculated as 0.70, 2.16 dS/m, and 1.72 dS/m for calibration period, and 0.89, 1.15 dS/m, and 0.89 dS/m for validation period, respectively, showing that simulation results was generally consistent with the observation data.

오염원 산정단위 수준의 소유역 세분화를 고려한 새만금유역 수문·수질모델링 적용성 검토

성충현,황세운,오찬성,조재필,Seong, Chounghyun,Hwang, Syewoon,Oh, Chansung,Cho, Jaepil 한국농공학회 2017 한국농공학회논문집 Vol.59 No.3

This study presented a surface water quality modeling framework considering the spatial resolution of pollutant load estimation to better represent stream water quality characteristics in the Saemangeum watershed which has been focused on keeping its water resources sustainable after the Saemangeum embankment construction. The watershed delineated into 804 sub-watersheds in total based on the administrative districts, which were units for pollutant load estimation and counted as 739 in the watershed, Digital Elevation Model (DEM), and agricultural structures such as drainage canal. The established model consists of 7 Mangyung (MG) sub-models, 7 Dongjin (DJ) sub-models, and 3 Reclaimed sub-models, and the sub-models were simulated in a sequence of upstream to downstream based on its connectivity. The hydrologic calibration and validation of the model were conducted from 14 flow stations for the period of 2009 and 2013 using an automatic calibration scheme. The model performance to the hydrologic stations for calibration and validation showed that the Nash-Sutcliffe coefficient (NSE) ranged from 0.66 to 0.97, PBIAS were -31.0~16.5 %, and $R^2$ were from 0.75 to 0.98, respectively in a monthly time step and therefore, the model showed its hydrological applicability to the watershed. The water quality calibration and validation were conducted based on the 29 stations with the water quality constituents of DO, BOD, TN, and TP during the same period with the flow. The water quality model were manually calibrated, and generally showed an applicability by resulting reasonable variability and seasonality, although some exceptional simulation results were identified in some upstream stations under low-flow conditions. The spatial subdivision in the model framework were compared with previous studies to assess the consideration of administrative boundaries for watershed delineation, and this study outperformed in flow, but showed a similar level of model performance in water quality. The framework presented here can be applicable in a regional scale watershed as well as in a need of fine-resolution simulation.

Assessment of Water Quality Calibration Criteria for Field-Scale Water Quality Model

성충현,김상민,박태양,정기웅,박승우,김성재 경상대학교 농업생명과학연구원 2010 농업생명과학연구 Vol.44 No.5

The objective of this study was to assess the statistics and associated criteria for field-scale model used to simulate nutrient concentrations in paddy field. CREAMS-PADDY, a modified version of the field-scale CREAMS model, simulates the hydrologic, sediment, and nutrient cycles in paddy fields was applied in this study. The model was calibrated and validated using data from study rice paddy fields in Republic of Korea. The calibration statistics include mean and the minimum-maximum range associated with a “temporal window” that spans a period of several days. Because nutrient concentrations in paddy filed are typically sampled infrequently (on a weekly basis, at best) and represent only an instant in time, it is not reasonable to expect any model to simulate a daily average concentration equal to an observed value on a particular day. The 5-day window and related calibration statistics were applied in this study and the applicability of this concept was tested for field-scale water quality model. As a result of calibration and validation, the ponded water nutrient concentration values showed only small changes except the fertilization period. Because of the small changes in ponded water concentration, the size of 5-day window was too small to capture the observed values. Further study is required to establish the 5-day window calibration method for field-scale water quality modeling.

이동차량에서 모바일 폰 카메라를 이용한 얼굴 인증 시스템

성충현,김성동,최기호 한국ITS학회 2004 한국ITS학회 학술대회 Vol.2004 No.1

Effect of assembly condition on the morphologies and temperature-triggered transformation of layer-by-layer microtubes

성충현,Jodie L. Lutkenhaus 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1

The morphology and temperature-triggered transformation of the LbL microtubes consisting of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were investigated as a function of assembly pH, polyelectrolyte molecular weight (MW), and multivalent ions. The as-made microtubes assembled at pH 5.5 (PAH)/5.5 (PAA) showed perforations on the surface, while those assembled at pH 7.5 (PAH)/3.5 (PAA) showed smooth surface without perforations. At the same MW, the microtubes assembled at pH 7.5/3.5 transformed more effectively compared to those assembled at pH 5.5/5.5. The aspect ratio of microtubes assembled at pH 7.5/3.5 decreased from 5 to 2 as the temperature increased from room temperature to 121 oC. Furthermore, transformation of microtubes was facilitated as the MW of polyelectrolytes decreased. The dimensional stability of microtubes was influenced by the MW and added multivalent ions. These results were discussed in the context of the structure of the LbL assemblies.

HSPF 모형과 호소 물수지를 이용한 미계측 간척 담수화호 수문모델링

성충현,Seong, Choung Hyun 한국농공학회 2014 한국농공학회논문집 Vol.56 No.6

This research presents an streamflow modeling approach in a data-scarce estuary reservoir watershed which has been suffered from high salinity irrigation water problem after completion of land reclamation project in South Korea. Since limited hydrology data was available on the Iwon estuary reservoir watershed, water balance relation of the reservoir was used to estimate runoff from upstream of the reservoir. Water balance components in the reservoir consists precipitation, inflow from upstream, discharge through sluice, and evaporation. Estimated daily inflow data, which is stream discharge from upstream, shows a good consistency with the observed water level data in the reservoir in terms of EI (0.93) and $R^2$ (0.94), and were used as observed flow data for the streamflow modeling. HSPF (Hydrological Simulation Program - Fortran) was used to simulate hydrologic response of upstream of the reservoir. The model was calibrated and validated for the periods of 2006 to 2007 and 2008 to 2009, respectively, showing that values of EI and $R^2$ were 0.89 and 0.91 for calibration period, 0.71 and 0.84 for validation period.