• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.132-139
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• 2010

The river technology of Japan was highly developed and achieved much result in flood protection, water use and the environment. Nowadays, the function which is requested to the river is changes because the society changes from growth to maturity. In this study, we suggest the functions of the river in the maturity society about future welfare, medical care and education based on field research of case study. In this research, we pay attention to the functions related with culture, one) function of healing, mental stress improvement and life, two) function of landscape, education and recreation. And this paper proposed the usage of the river where adopt to the times, a function and the value of "the river as the space". We made a questionnaire to 187 river managers, and 90% of answers wear positive for use the river as the medical aspect, health and the welfare. Furthermore, based on research result of hospitals and welfare facilities which used a river for their activities, we suggest to develop and use the river walk, to design a city and rivers as one, and to use many facilities which are located on river front more active, those are improve the new river functions.

• Computers and Concrete
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• v.24 no.4
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• pp.283-293
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• 2019

The limited availability of raw materials and increasing service demands for pavements pose a unique challenge in terms of pavement design and concrete material selection. The self-compacting rubberized concrete (SCRC) can be used in pavement design. The SCRC pavement slab has advantages of excellent toughness, anti-fatigue and convenient construction. On the premise of satisfying the strength, the SCRC can increase the ductility of pavement slab. The aim of this investigation is proposing a new method to predict the crack growth and flexural capacity of large-scale SCRC slabs. The mechanical properties of SCRC are obtained from experiments on small-scale SCRC specimens. With the increasing of the specimen depth, the bearing capacity of SCRC beams decreases at the same initial crack-depth ratio. By constructing extended finite element method (XFEM) models, crack growth and flexural capacity of large-scale SCRC slabs with different fracture types and force conditions can be predicted. Considering the diversity of fracture types and force conditions of the concrete pavement slab, the corresponding test was used to verify the reliability of the prediction model. The crack growth and flexural capacity of SCRC slabs can be obtained from XFEM models. It is convenient to conduct the experiment and can save cost.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.1-7
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• 2011

PEM 연료전지에 있어서 수분의 균형이 연료전지의 시스템 성능에 현저한 영향을 미친다. 그래서 수분 균형은 가장 중요한 요소 중의 일부가 되었으며, 이에 관한 연구가 광범위하게 이루어지고 있다. 적절한 수분 균형을 유지하기 위해서는 적당한 멤브레인 수화작용(membrane hydration)이 필요하며, 반대로 촉매층(catalyst layer)에서의 익수(water flooding)현상이 없어져야 한다. 따라서 이와 같은 동적 상태에서 PEM 연료전지 내의 수분 균형을 유지하기 위해서는, 고도의 동적 수분 조정 기술이 확보되어야 한다. 현재의 연구는 이러한 특성을 고려하여 PEM 연료전지에서 동적부하 상태에서의 수분 이동에 관한 일차원 해석 모델에 관한 것이다. 금번 모델링의 결과, 양극촉매층(CCL, cathode catalystlayer)에서의 수분 상태는 거의 포화 단계에 이르고 있음을 보여주고 있으며, 이 모델링은 연료전지가 작동되는 동안의 CCL에 나타나는 수분의 양상을 예측하는데 활용될 수 있다. 본 논문에서는 수분 이동 모델이 국제규격에 따라 다양한 수송기관이 가동될 때, 동적부하 상태에서 서로 다른 차이점을 발견하기 위한 시뮬레이션 결과에 초점이 맞추어져 있다. 이 모델링을 적용한 결과, 수분 포화도가 상태에 따라 상이하게 나타남을 알 수 있었고, 또한 정적 수분 조절 요소에 따라 최적 상태가 모든 동적 분포에 따라 달라짐을 알 수 있었다.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.555-560
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• 2023

Conventional aqueous amine-based CO₂ capture has a problem in that a large amount of renewable energy is required for CO₂ stripping and solvent regeneration in its industrial applications. This work proposes a water-lean absorbent that can reduce regeneration energy by lowering the water content in the absorbent with high absorption capacity for CO₂. To this purpose, this water-lean solvent introduced NMP (N-methyl-2-pyrrolidone), which has a higher physical solubility in CO₂ and a low specific heat capacity comparing to water, along with 3-methylaminopropylamine (MAPA), a diamine, into the absorbent. The circulating absorption capacity and absorption rate for CO₂ of this water-lean solvent were measured using a packed tower. When NMP was added to the absorbent, the absorption rate was improved. In the case of the absorbent containing 2.5M MAPA was used, the maximum circulating absorption capacity was obtained when 10 wt% of NMP was included in absorbent. The overall mass transfer coefficient increased as the concentration of NMP increased. However, at loading values higher than 0.5, the increment in mass transfer coefficient decreased as the concentration of NMP increased. When the lean loading value is low, the mass transfer resistance due to viscosity of the absorbent is low, so the overall mass transfer coefficient increases with the addition of NMP. However, as the lean loading value increases, the viscosity of the absorbent increases, and the diffusivity of CO₂ and MAPA decreases, resulting in sharply decreasing of the overall mass transfer coefficient.

• Journal of Korea Port Economic Association
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• v.27 no.1
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• pp.1-11
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• 2011

The main purpose of this paper is to estimate the impact of exchange rate and economic business activity on the passengers' demand for international transportation. The demand pattern depends upon the transport vehicles that the global passengers take. The global passengers' demand for transportation is modelled as exchange rate, industrial production and seasonal dummy variables. The seasonality is found in both water and air, but the former is far greater than the latter. All series span the period January 1990 to December 2008. The empirical results of this paper reveal that the income elasticity of sea transport is greater than that of air one, all of which are positive. The study also shows that the exchange rate has an significant impact on the demand for air transport, whereas it is insignificant in water transport. The impulse response function indicates that passengers increase steadily before peaking seven to eight months after the shocks to economic business activity and decline very slowly to its pre-shock level. The air passengers also respond negatively to the shocks in exchange rate and the impacts of exchange rate shock seem to decrease relatively slowly, while the water passengers respond positively after six months. The industrial production shocks remain above equilibrium for more than twenty four months, while the exchange rate shocks remain below equilibrium for more than twenty four months. Boosted by improved economic conditions worldwide, international tourism has recovered faster than expected from the impacts of the global financial crisis and economic recession of late 2008 and 2009. These facts suggest that the demand of global water transport has the high possibility of growing steadily and continuously.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.175-181
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• 2017

The purpose of this study is evaluating the characteristics of tensile strength of UHPC and examining tensile performance of notched specimens by direct tensile test. For test variables, 120, 150, and 180MPa of target design standard strength were aimed at. With general water curing and $90^{\circ}C$ high temperature steam as curing conditions, the properties were reviewed. Overall, it was represented that the specimens of notch-type direct tensile strength concrete was effective in inducing central cracks compared with existing direct tension specimens. Through this, it was judged that data construction with high reliability was possible. Above all, in a graph of direct tensile strength and strain, in the case of steam curing at high temperature, there was great difference of initial tensile strength compared with water curing. As passing of ages, an aspect that the difference gradually decreased was shown. Maximum tensile strength was found to increase steadily with increasing age for all target design strengths in water curing, in the case of steam curing, the tendency to increase significantly due to the initial strength development effect at 7 days of age. The initial crack strength increases with age in case of underwater curing, in the case of steam curing, it was higher than that of water curing in 7 days, while the strength of 28 days was lowered. In this part, it is considered necessary to examine the arrangement condition of the steel fiber.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.217-231
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• 2017

The subsidence of ground in urban area can be caused by the occurrence of the cavity and the change in ground volumetric water content. The objective of this study is the detection of abnormal area of ground in urban area where the cavity or the change in ground volumetric water content is occurred by the ground penetrating radar signal. GPR survey is carried out on the test bed with a circular buried object. From the GPR survey, the signals filtered by the bandpass filtering are measured, and the methods consisting of gain function, time zero, background removal, deconvolution and display gain are applied to the filtered signals. As a result of application of the signal processing methods, the polarity of signal corresponds with the relation of electrical impedance of the cavity and the ground in test bed. In addition, the relative permittivity calculated by GPR signal is compared with that of predicted by volumetric water content of the test bed. The relative permittivities obtained from two different methods show similar values. Therefore, the abnormal area where the change in ground volumetric water content is occurred can be detected from the results of the GPR survey in case the depth of underground utilities is known. Signal processing methods and estimation of relative permittivity performed in this study may be effectively used to detect the abnormal area of ground in urban area.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.523-532
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• 2015

Hydrocyclone is widely used in industry, for its simple design, high capacity, low maintenance and low operational cost. The objective of this study is to develop hydrocyclone coagulation and filtration system. The system is made of hydrocyclone ballasted coagulation with polyaluminium chloride silicate (PACS) and upflow filter to treat micro particles in urban storm runoff. Roadside sediment particles (< $200{\mu}m$) was mixed with tap water to make various turbid suspensions to simulate urban storm runoff. The filter cartridge was filled with polyethylene media system and ran 1hr per everyday and total operation time were 8.19hrs and backwashing everyday after end of operation. The operation condition of flowrate was $8.2{\sim}11.9m^3/day$ (mean $10.1m^3/day$) and surface overflow rate (SOR) based on filter surface area was $45.5{\sim}65.9m^3/m^2/day$ (mean $55.7m^3/m^2/day$). The range of PACS dosage concentration was 14.0~31.5 mg/L. As the results of operation, the range of removal efficiency of turbidity, SS were 81.0~95.8% (mean 89.5%) 81.8~99.0% (mean 91.4%), respectively. An increase of filtration basin retention time brought on increased of removal efficiency of turbidity and SS, and increase of SOR brought on decreased of removal efficiency. During the first flush in urban area, storm runoff have an high concentration of SS (200~600 mg/L) and the filtration bed becomes clogged and decreased of removal efficiency. Backwashing begins when the drainage pipe valve at the filtration tank bottom is completely open (backwashing stage 1). Backwashing stage 2 was using air bubbles and water jet washing the media for 5 mins and open the drainage valve. After backwashing stage 1, 2, 61.83~64.04%, 18.53~27.51% of SS loading was discharged from filtration tank, respectively. Discharged SS loading from effluent was 7.12~14.79% and the range of residual SS loading in fliter was 2.26~5.00%. The backwashing effects for turbidity, SS were 89.5%, 91.4%, respectively. The hydrocyclone coagulation and filtration with backwashing system, which came out to solve the problems of the costly exchange filter media, and low efficiency of removing micro particles of filter type nonpoint treatment devices, is considered as an alternative system.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.4
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• pp.373-379
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• 2017

We carried out the enzymatic synthesis of 1, 2-hexanediol galactoside (HD-gal) by transgalactosylation reaction using recombinant Escherichia coli ${\beta}-galactosidase$ (${\beta}-gal$). The amounts of ${\beta}-gal$ and 1, 2-hexanediol (HD), pH, and temperature, respectively, were first optimized (${\beta}-Gal$, 4.8 U/mL; HD, 75 mM; pH, 7.0; temperature, $37^{\circ}C$). Under these optimal conditions, about 96% HD was converted to HD-gal. When we investigated the water holding capacities (WHCs) of HD and HD-gal using pig epidermis in the concentrations of 84.4, 126.6, 168.8, 211.0 mM, WHC of HD-gal was superior to HD. In particular, at 168.8 mM HD and HD-gal, WHC of HD-gal showed about 20% greater than that of HD. However, it was observed that MIC values against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus of HD-gal were about three to ten times greater than those of HD, although MIC value of HD-gal against Enterococcus faecalis was almost the same as that of HD. Finally, it was concluded that the covalent bonding of a galactose molecule to HD (transgalactosylation) resulted in an increase in WHC of HD-gal and a decrease in anti-bacterial activity.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.359-364
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• 2017

This study examined business acts related to leisure boats, so as to investigate the differences of regulations and things to be supplemented, as well as to suggest improvement measures. In order to achieve this purpose, the authors analyzed the respective legislations. The Acts on businesses using leisure boats(or power-driven water leisure crafts) are the Marine Transportation Act, Excursion Ship and Ferry Business Act, Water-Related Leisure Activities Safety Act, and Act on the Development, Management, etc. of Marinas. These Acts have differences in regulations, in terms of gross tonnage, the age of vessels, crewman, and the liquor traffic. These differences can cause problems such as adjusting the gross tonnage of the vessel by modifying the structures of the facilities, assigning old vessels, sailing without crewmen required for safety, and going against fairness in the liquor traffic in similar businesses. Such differences appeared to be caused by the lack of understanding of leisure boats and the series of new legislation which have been added one by one. It is required to raise the understanding on the characteristics of leisure boats and reflect them in the legislation.