• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.258-258
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• 2014

Spark discharge in water generates shockwaves which have been utilized to generate mechanical actuation for potential use in pumping application. Discharge pulses of several microseconds generate shockwaves and vapor bubbles which subsequently displace the water for a period of milliseconds. Through the use of a sealed discharge chamber and metal bellow spring, the fluid motion can be used create an oscillating linear actuator. Continuous actuation of the bellow has been demonstrated through the use of high frequency spark discharge. Discharge in water forms a region of high electric field around the electrode tip which leads to the creation of a thermal plasma channel. This process produces fast thermal expansion, vapor and bubble generation, and a subsequent shockwave in the water which creates physical displacement of the water [1]. Previous work was been conducted to utilize the shockwave effect of spark discharge in water for the inactivation of bacteria, removal of mineral fouling, and the formation of sheet metal [2-4]. Pulses ranging from 25 to 40 kV and 600 to 900 A are generated inside of the chamber and the bellow motion is captured using a slow motion video camera. The maximum displacements measured are from 0.7 to 1.2 mm and show that there is a correlation between discharge energy input to the water and the displacement that is generated. Subsequent oscillations of the bellow are created by the spring force of the bellow and vapor in the chamber. Using microsecond shutter speed ICCD imaging, the development of the discharge bubble and spark can be observed and measured.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.8-14
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• 2007

Water quality in Lake Rotorua, New Zealand, deteriorated since the 1960s because of excessive phytoplankton growths due principally to increasing nitrogen and phosphorus in the lake waters. Nutrient concentrations in eight of the nine major streams feeding Lake Rotorua have increased since 1965. The groundwater system has a key role in the hydrology of the Lake Rotorua catchment and the groundwater system is probably the control on the time delay between intensification of agricultural land use and response of surface water quality. All major, and many minor streams, in the catchment are fed by springs. Two lithological units are most important to groundwater flow in the Lake Rotorua catchment: Mamaku Ignimbrite, erupted in about 200,000 years ago and Huka Formation sediments which filled the caldera left by the Mamaku Ignimbrite eruption. Rainfall recharge to groundwater in the groundwater catchment of Lake Rotorua is estimated as approximately 17300 L/s. A calibrated steady-state groundwater flow model estimates that approximately 11100 L/s of this flow discharges into streams and then into the lake and the balance travels directly to Lake Rotorua as groundwater discharge through the lake bed. Land use has impacted on groundwater quality. Median Total Nitrogen (TN) values for shallow groundwater sites are highest for the dairy land use (5.965 mg/L). Median TN values are also relatively high for shallow sites with urban-road and cropping land uses (4.710 and 3.620 mg/L, respectively). Median TN values for all other uses are in the 1.4 to 1.5 mg/L range. Policy development for Lake Rotorua includes defining regional policies on water and land management and setting an action plan for Lake Rotorua restoration. Aims in the action plan include: definition of the current nutrient budget for Lake Rotorua, identification of nutrient reduction targets and identification of actions to achieve targets. Current actions to restore Lake Rotorua water quality include: treatment of Tikitere geothermal nitrogen inputs to Lake Rotorua, upgrade of Rotorua City sewage plant, new sewage reticulation and alum dosing in selected streams to remove phosphorus.

• Journal of Korea Water Resources Association
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• v.32 no.4
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• pp.501-510
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• 1999

Stream and groundwater qualities of small agricultural watershed in Kangwon Probince, Korea were monitored 1 to 2 years, and the relationships between stream and groundwater qualities and seasonal water quality changes analyzed. Flooded paddy fields influenced groundwater level and quality during rice culture. The differences between groundwater levels during rice culture and non-culture spans were between 0.8 and 2.91 m. Seasonal changes of total nitrogen and nitrate nitrogen concentrations of stream and groundwater were very similar and groundwater quality was thought to have a profound impact on stream quality of the research watersheds. Suspended solids and BOD maintained the first degree stream water quality throughout the monitoring period except for a few and short flooding spans. The concentrations of total phosphorus and total bacteria of both waters showed wide variations and any seasonal trends were not observed. Long-term monitoring studies on small rural watersheds were recommended to understand the pattern of both stream and groundwater quality changes with respect to land use, season and cultural practice, and to apply the results to develop effective water quality management policies for large river and domestic water supply systems.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.333-341
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• 2021

Irrigation scheduling is a water management strategy of applying the proper amount of water in a plant's root zone at the right time to maximize profit. We conducted an experimental evaluation of the response of soybean, sorghum, and sesame to an irrigation scheduling scheme. The soil water contents were adjusted in the root zone between 20% and 28% to reflect changes in crop water consumption. The other ones fixed at 25% during the whole growing season were compared to evaluate the effectiveness of irrigation scheduling. Surface drip irrigation (SDI) were employed as an irrigation method. For all three crops, the evapotranspiration (ET) was the greatest at flowering stage (6.93 mm), followed by vegetative growth stage (5.00 mm) and maturity stage (2.53 mm). The irrigation amount was significantly reduced by 21.8% (soybean), 22.2% (sorghum), and 16.1% (sesame), respectively, compared with the ones at constant soil water content treatment. Their water use efficiency (WUE) were also much higher than the controls: 2.65-fold increase at soybean, 1.82-fold increase at sorghum, and 1.47-fold increase at sesame. These results showed that an effective irrigation scheduling on upland crops (soybean, sorghum, sesame) could increase crop yield while minimizing water use.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.668-670
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• 2004

Taipei Water Management Office (TWMO) is one of the eleven district offices in Water Resource Agency. Water management is the top priority to be pursued both on daily management and long-term management at TWMO. There are five departments to perform a wide range of tasks in addition to water management. All management prescriptions are simply to provide sustainable clean water for about four millions population in Taipei. TWMO has gone through 16 years experience of development and implementation of GIS in water management. The objectives of this paper are to provide the major ingredients of successful and operational GIS for water management. The five departments at TWMO have performed tasks such as city planning, construction management, forest management, land use enforcement, soil and water conservation, water quality monitoring and protection, garbage collection, and sewage disposal management. Data base creation was one of the major jobs to be done. Update of data base has to be done on a daily basis. Computers, its peripheral, and software are essential for GIS developed at TWMO. Know-how and technical skill on computers and GIS for every technician are contributing significantly such that GIS can be implemented on most of jobs performed at TWMO. Implementations of GIS have been pursued by application modules on a task-oriented basis. Application modules are simple, easy to use, and menu driven with only Chinese. Web-based and mobile GIS are the new components that make water management at TWMO stay on the right course. To solve problems encountered in water management by GIS at TWMO can be easily and user-friendly may be the most important experience.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.563-574
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• 2006

Economic theory tell us, consumers always make a choice to maximize their utility. In the market system, consumers' choices are revealed and policy maker taking into account the aggregated consumers choice such as price, supply and demand. However, water resources as a public goods, therefore typically there is no market and does no aggregated information for residential water use. This study explore the consumers' willingness to pay for higher quality for residential water. Over 1,000 households responded for this survey and willingness to pay has been estimated. Furthermore, consumers' behaviors of residential water are examined. Consumers are willing to reduce the amount of water use with more than 50% of increasing water price, but stay almost constant with less than 25% of increasing which mean that current price level is not high enough to derive water saving. If consumers can have better quality of water, they willing to pay additional 16%, $153\;won/m^3/month$, more than their current price. Based on the derived information, we suggested policy direction for residential water policy.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.477-487
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• 2021

Due to the global climate change, Korean peninsula is has been experiencing flooding and drought severely. It is hard difficult to manage water resources sustainably, because due to intensive precipitation in short periods and severe drought has increased in Korea. Reused water from the wastewater treatment plant (WWTP) could be a sustainable and an alternative water source near the urban areas. In order to understand the patterns of water reuse in Korea, annual water reuses data according to the times and regional governments were investigated from 2008 to 2019. The reused water from WWTP in Korea has been mainly used for river maintenance flow and industrial use, while agricultural use of water reuse has decreased with time. Metropolitan cities in Korea such as Seoul, Busan, Daegu, Ulsan, and Incheon have been mainly used reused reusing water for river maintenance flow. Industrial water reuse has been limitedly applied recently for the planned industrial districts in Pohang, Gumi, Paju, and Asan. By using the collected annual water reuse data from the domestic sewerage statistics of sewerage, the optimistic and pessimistic future estimations of for future annual water reuse were suggested from 2020 to 2040 on a five year interval for every five years.

• Journal of the Korean housing association
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• v.19 no.1
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• pp.79-88
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• 2008

Hot water is used by having a wash, dishes, taking tub and drinking water in residential buildings, and the use objective is to raise comfort of human body sense, washing and sterilization effect and so on. Cold & hot water supply system is understanded simpler than HVAC systems relatively, so it is true that pace of performance improvement is slower than other systems for plan and technical development. In this study, the performance evaluations are conducted under the condition of composition ratio by 1:1 for cold & hot water supply manifold system using functionally complex valves such as constant flow regulating valve and 3-way mixing valve in the area of $105.6m^2$ apartment which consist of the largest part of the whole apartment. Also, flow rate related to simultaneous use of faucets and change of hot water temperature are compared with the existing method.

• Journal of Korean Society on Water Environment
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• v.31 no.4
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• pp.418-427
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• 2015

This study was carried out to evaluate the performance of a lab-scale novel septic tank system for improving the conventional septic tank in the developing countries of water shortages. The lab-scale novel septic tank system consists of sepetic tank, aeration tank with HBC-ring, and sand filter. Optimum HRT was reguired about 1.5days to get a total COD removal efficiency of 90%, COD, BOD and SS removal efficiency was about 70%, 60%, and 85% in sepetic tank only. The structure of sepetic tank with two stages results in the high removal efficiency of organic matter. When sepetic tank, aeration tank, and sand filter were more than HRT 1.5days, 18hrs, and 12hrs, respectively, final effluent was less than 20 mg/L of BOD, 14 mg/L of SS, so that there is a high potential of its use for reusing water in flush toilet. There is no significant effect of HRT change on nutrient removal. Total nitrogen removal efficiency was about 40%, final effluent was 30~40 mg/L of TN, total phosphorus removal efficiency was about 11~25%, final effluent was 9~12 mg/L of TP. Because there is very small amounts of organic nitrogen and phosphorus in effluent, it was possible to reuse water for agricultural use.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.147-147
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• 2018

In this article, we use an open source software library: TensorFlow, developed for the purposes of conducting very complex machine learning and deep neural network applications. However, the system is general enough to be applicable in a wide variety of other domains as well. The proposed model based on a deep neural network model, LSTM (Long Short-Term Memory) to predict the river water level at Okcheon Station of the Guem River without utilization of rainfall - forecast information. For LSTM modeling, the input data is hourly water level data for 15 years from 2002 to 2016 at 4 stations includes 3 upstream stations (Sutong, Hotan, and Songcheon) and the forecasting-target station (Okcheon). The data are subdivided into three purposes: a training data set, a testing data set and a validation data set. The model was formulated to predict Okcheon Station water level for many cases from 3 hours to 12 hours of lead time. Although the model does not require many input data such as climate, geography, land-use for rainfall-runoff simulation, the prediction is very stable and reliable up to 9 hours of lead time with the Nash - Sutcliffe efficiency (NSE) is higher than 0.90 and the root mean square error (RMSE) is lower than 12cm. The result indicated that the method is able to produce the river water level time series and be applicable to the practical flood forecasting instead of hydrologic modeling approaches.