• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.256-267
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• 2009

A method of estimating pollutant delivery ratios considering watershed physical and meteorological characteristics and flow conditions using SWAT-K watershed model was described, and pollutant delivery characteristics during dry and rainy seasons, for monthly and seasonally, and with flow regimes were investigated for the Chungju dam watershed. Delivery ratios for sediment, T-N, and T-P showed higher values over 100% during dry and winter seasons with low pollutant loads and flows, and showed relatively uniform ones under 100% during rainy and summer seasons with concentrated loads and flows. It was found that mainly wet flows during summer seasons played very important roles in investigating the delivery characteristics of total or nonpoint pollutant loads, because more than 90% of total loads were influenced by nonpoint source, and discharged with the flows. From the results, we could find out the delivery characteristics with various watershed and flow conditions which are difficult to consider by actual measurement, and could get a foothold of estimating more reasonable and scientific allocated loads for water quality standard using the reliable method of estimating delivery ratios with a watershed model.

• Advances in concrete construction
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• v.5 no.5
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• pp.481-492
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• 2017

The aim of this paper is to investigate the effect of quartz powder (Qp), quartz sand (Qs), and different water curing temperature on mechanical properties including 7, 14, 28-day compressive strength and 28-day splitting tensile strength of Ultra High Performance Concrete and also finding the correlation between these variables on mechanical properties of UHPC. The response surface methodology was monitored to show the influences of variables and their interactions on mechanical properties of UHPC, then, mathematical models in terms of coded variables were established by ANOVA. The offered models are valid for the variables between: quartz powder 0 to 20% of cement substitution by cement weight, quartz sand 0 to 50% of aggregate substitution by crushed limestone weight, and water curing temperature 25 to $95^{\circ}C$.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.195-195
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• 2017

The patterns of occurrence of typhoons in North Pacific region are constantly changing with the increase of temperature in sea surface and the occurrence of El Nino and La Nina and changes of their development caused by global warming. In addition, alterations of flow regimes caused by large-scale hydraulic construction projects in the past few years and changes in precipitation patterns caused by climate change have imposed increased stress on hydroecology while the indiscreet utilization of water resources has a negative environmental impact on the water flows in the natural rivers and streams and hydroecological structures. The purpose of this study is to explore the impact of altered hydrologic regime on stream and riparian ecosystems that are most vulnerable to climate variability and extremes such as typhoons.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.611-616
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• 2015

The Antarctic high plateau offers exceptional conditions for infrared and terahertz astronomy, as well as for programs requiring long, uninterrupted periods for measurements made with high cadence and photometric precision (i.e. time domain astronomy). In this review we summarise the special conditions of the Antarctic plateau which facilitate these observing regimes. We also outline some high profile science programs in each that could be conducted most effectively from the Antarctic high plateau, involving the first light in the Universe, the life cycle of our Galaxy, and the equation of state for the Universe. Three high plateau sites are under particular consideration for furthering such scientific programs{Dome A, Dome F and Ridge A. We summarise the activity underway at each site, which includes the building of new stations and the construction of facilities for optical, infrared and terahertz astronomy, as well as the plans for their future development.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.6
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• pp.61-74
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• 2004

Hydraulic engineers and scientists working on river restoration recognize the need for a deeper understanding of natural streams as a complex and dynamic system, which involves not only abiotic elements(flow, sediments) but also biotic components. From this point of view, the role played by riverine vegetation dynamics and flow conditions becomes essential. Hydro-mechanic interaction between flow and flexible plants covering a river bed is studied in this paper and some previous works are discussed. Measurements of turbulence and flow resistance in vegetated open channel were performed using rigid and flexible tube. Measuring detailed turbulent velocity profiles within and above submerged and flexible stems allowed to distinguish different turbulent regimes. Some interesting relationships were obtained between the velocity field and the deflected height of the plants, such as a reduced drag coefficient in the flexible stems. Turbulent intensities and Reynolds stresses were measured showing two different regions : above and inside the vegetation domain. In flexible vegetated open channel, the maximum values of turbulent intensities and Reynolds stresses appear above the top of canopy. Method to predict a flow resistance in flexible vegetated open channel is developed by modifying an analytical model proposed by Klopstra et al. (1997). Calculated velocity profiles and roughness values correspond well with flume experiments. These confirm the applicability of the presented model for open channel with flexible vegetation. The new method will be verified in the real vegetated conditions in the near future. After these verifications, the new method should be applied for nature rehabilitation projects such as river restorations.

• The Southeast Asian review
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• v.24 no.1
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• pp.191-221
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• 2014

South Sumatra's capital, Palembang, has long maintained a river-oriented transportation system. With road transportation's increased importance for exploiting natural resources, however, hundreds of roads have been constructed since the Dutch colonial period. This article examines how the construction of roads and bridges affected people's lives and social networks in Palembang, and what social and political significance it has in the context of a region in the postcolonial Indonesia, with a focus on the huge river called the Musi River, which horizontally crosses the city. After independence, there has been strong aspiration to link these two parts by road, and in 1965 the Musi Bridge (then the Sukarno Bridge) over the river was eventually opened. The construction of the bridge apparently initiated socioeconomic transformations and development in the region, including Ulu (the southern river bank)'s rapid urbanization. However, the features of regional development actually were prerequisites for "national" development. The regional development was impossible without financial support from the central government, and the local or regional aspiration for development was often supported only when it fitted with national envision. The Musi Bridge was a model case that fitted with such national envision. While it was the symbol of regional development, it was also celebrated as an exemplary sign of "national" development, by both Sukarno's government and Suharto's New Order regime. By analyzing the discussions and discourses regarding the Musi project since early 1950s, in addition to its social and economic impact after the construction, this article explores the continuities and changes in the roles and significance of the (construction of the) Musi Bridge with the changing political backstops in both regimes. Together with it, this article also aims to reexamine the interplay between "the national" and "the regional" in the prevalent aspiration for the national and regional "development" throughout the 1950s and 1960s.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.35-41
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• 2007

In general, coastal damage is mostly occurred by the action of complex factors, like severe water waves. If the maximum storm surge height combines with high tide, severe water waves will overflow coastal structures. Consequently, it can be the cause of lost lives and severe property damage. In this study, using the numerical model, the storm surge was simulated to examine its fluctuation characteristics at the coast in front of Noksan industrial complex, Korea. Moreover, the shallow water wave is estimated by applying wind field, design water level considering storm surge height for typhoon Maemi to SWAN model. Under the condition of shallow water wave, obtained by the SWAN model, the wave overtopping rate for the dike in front of Noksan industrial complex is calculated a hydraulic model test. Finally, based on the calculated wave-overtopping rate, the inundation regime for Noksan industrial complex was predicted. And, numerically predicted inundation regimes and depths are compared with results in a field survey, and the results agree fairly well. Therefore, the inundation modelthis study is a useful tool for predicting inundation regime, due to the coastal flood of severe water wave.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.1003-1011
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• 2006

Droplets are ejected onto a substrate through a nozzle by pushing liquids in flow channels of drop-on-demand devices. The behavior of ejection and formation of droplets is investigated to enhance the physical understanding of the hydrodynamics involved in inkjet printing. The free surface phenomenon of a droplet is described using $CFD-ACE^{TM}$ which employs the volume-of-fluid (VOF) method with the piecewise linear interface construction (PLIC). Droplet formation characteristics are analyzed in various flow regimes with different Ohnesorge numbers. The computational results show that the droplet formations are strongly dependent on the physical properties of working fluids and the inlet flow conditions. In addition, the wetting characteristics of working fluids on a nozzle influence the volume and velocity of a droplet produced in the device. This study may provide an insight into how a liquid droplet is formed and ejected in a piezoelectric inkjet printing device.

• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.295-303
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• 2004

In this paper, an improved four-node Reissner-Mindlin plate-bending element with enhanced assumed strain field is presented for the analysis of isotropic and laminated composite plates. To avoid the shear locking and spurious zero energy modes, the transverse shear behavior is improved by the addition of a new enhanced shear strain based on the incompatible displacement mode approach and bubble function. The "standard" enhanced strain fields (Andelfinger and Ramm, 1993) are also employed to improve the in-plane behaviors of the plate elements. The four-node quadrilateral element derived using the first-order shear deformation theory is designated as "14EASP". Several applications are investigated to assess the features and the performances of the proposed element. The results are compared with other finite element solutions and analytical solutions. Numerical examples show that the element is stable, invariant, passes the patch test, and yields good results especially in highly distorted regimes.

• Journal of Soil and Groundwater Environment
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• v.9 no.4
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• pp.8-14
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• 2004

To investigate the optimal operation factors in appling Soil Flushing Process, which use EDTA and boric acid composite as a flushing reagent, to the Cd(cadmium) and Cr(chromium) contaminated sites, Cd and Cr emediation rate was investigated at various experimental conditions; as EDTA concentration was increased from 0.001M to 0.1M, Cd remediation rate was increased from $73.2\%\;to\;98.5\%$; as boric acid concentration was increased from 0.001M to 0.1M, Cr remediation rate was increased from $59.2\%\;to\;99.0\%$. In the experiments using 0.005M of EDTA and 0.005M of boric acid composite as a flushing reagent at different pH regimes, Cd remediation rate was decreased from $92.4\%\;to;80.9\%$ as the pH was increased from 3 to 7. But Cr remediation rate was more effective ($70.4\%$) at pH 5 compared to the other pHs. Furthermore, at pH 5, Cd and Cr remediation rate was investigated at different molecular ratio of [EDTA]/[Boric aicd]; the optimized [EDTA]/[Boric acid] ratio was 0.01M/0.1M for Cd contaminated site and, as the concentration of boric acid was increased over 0.1M, Cr remediation rate was also increased. So the similar results were shown in the experiments using real contaminated soils which were sampled from a mining and a industrial area.