• 상하수도학회지
• /
• 제34권6호
• /
• pp.473-480
• /
• 2020

High-pressure membrane system like nanofiltration(NF) and reverse osmosis(RO) was investigated as a part of water treatment processes to produce high quality potable water with low organic matter concentration through membrane module tests and design simulation. River water and sand filtration permeate in Busan D water treatment plant were selected as feed water, and NE4040-90 and RE4040-Fen(Toray Chemical Korea) were used as NF and RO membranes, respectively. Total organic carbon(TOC) concentrations of NF and RO permeates were mostly below 0.5 mg/l and the average TOC removal rates of NF and RO membranes were 93.99% and 94.28%, respectively, which means NF used in this study is competitive with RO in terms of organic matter removal ability. Different from ions rejection tendency, the TOC removal rate increases at higher recovery rates, which is because the portion of higher molecular weight materials in the concentrated raw water with increasing recovery rate increases. Discharge of NF/RO concentrates to rivers may not be acceptable because the increased TDS concentration of the concentrates can harm the river eco-system. Thus, the idea of using NF/RO concentrate as the raw water for industrial water production was introduced. The design simulation results with feed water and membranes used in this work reveal that the raw water guideline can be satisfied if the recovery rate of NF/RO system is designed below 80%.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.265-273
• /
• 2016

A water wall system is one of the most important components of a boiler in a thermal power plant, and it is a nonlinear Multi-Input and Multi-Output (MIMO) system, with 6 inputs and 3 outputs. Three models are developed and comp for the controller design, including a linear model, a multilayer feed-forward neural network (MFNN) model and an Echo State Network (ESN) model. First, the linear model is developed by linearizing a given nonlinear model and is analyzed as a function of the operating point. Second, the MFNN and the ESN are developed by using training data from the nonlinear model. The three models are validated using Matlab with nonlinear input-output data that was not used during training.

• 한국기계가공학회지
• /
• 제10권3호
• /
• pp.87-93
• /
• 2011

CNC lathe machining has been widely used for parts machining of vehicles, aircraft, ships, electronics, etc. because cost savings for shortening processing time and increasing productivity are great. In this study, the purpose is to investigate the effect of cooling methods such as oil mist, water-soluble cutting oils on the workpiece surface roughness with the cutting speed, cutting depth, tool nose radius and feed rate of CNC lathe machine as a parameter in the cutting process of the aluminum alloy 2024 which is used a lot recently on aircraft parts. It is found that oil mist is coolant and water-soluble cooled by cutting the experimental conditions, cutting speed and cutting depth without effecting the surface roughness value was constant.

• 한국인쇄학회지
• /
• 제23권1호
• /
• pp.13-25
• /
• 2005

In order to technical analysis of the Newspaper printing press, the printability such as, dot gain, contrast and printing density change according to the amount of ink and damping water feeding were experimented. t도 Printability assurance in printing aims at a correct and constant color reproduction throughout the whole print-run. And the checked values were checked from densitometer and colorimeter instead of conventional subjective method. In this research, we could propose the range of driving in printing of domestic Newspaper printing press as well as the limits of ink feed speed and damping water feed speed.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
• /
• pp.45-46
• /
• 2006

Usual LEO satellite for earth observation use a blowdown hydrazine monopropellant propulsion system for attitude hold and orbit maintenance. For precision control, thruster valve has very short closing time, but this can cause water hammering and pressure surge. Since water hammering and pressure surge can cause damage of propulsion system and ununiform thrust, Thruster valve closing is one of the special concern during satellite propulsion system design. In this paper, an analysis for propellant feed system is conducted using the method of characteristics. The results represent water hammer effect is negligible even at the worst case and pressure surge can be decreased effectively with a trim orifice.

• 상하수도학회지
• /
• 제16권6호
• /
• pp.717-725
• /
• 2002

A bench-scale submerged-type membrane filtration system (SMFS) was constructed to study a feasibility of membrane filtration for solid-liquid separation in water and wastewater treatment processes. In the case of applying the SMFS to a biological wastewater treatment process, so-called membrane bioreactor, aeration underneath membrane modules is usually employed in order to provide oxygen demand for microbial growth as well as to control membrane fouling. A study was investigated the effects of operation parameters by aeration intensity, feed concentration, foulant type and airlift pore size on critical flux. Critical flux tends to increase with aeration rate. Optimal aeration flow rate was found to be 10 L/min/module. Feed concentration and foulant type has a significant effect on membrane fouling and filtration performance. But downward position and pore size of airlift has no a significant effects on membrane fouling and filtration performance.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2017년도 학술발표회
• /
• pp.506-510
• /
• 2017

최근 변화된 하천환경에서 대량 발생하는 조류는 다양한 수질 문제를 일으켜 이에 대한 관심이 점차 높아지고 있다. 특히 낙동강의 조류발생과 피해가 심화되면서 다양한 관련 연구가 폭넓게 수행되고 있으나, 본류와 지류가 만나는 합류부에서의 수리 수질 특성과 조류발생 간의 관계를 구명하기 위한 연구는 전무한 실정이다. 따라서 본 연구에서는 낙동강-남강 합류부에서 녹조대발생기 현장측정을 통해 합류부에서의 조류와 수리 수질 특성 간의 관계를 파악하고자 하였다. 측정결과 수심별 조류의 분포양상이 수채 내 수온 및 수질인자 분포에 따른 성층정도와 관계가 있음을 확인할 수 있었다. 또한 다양한 수질인자와 조류발생 간의 관계에 대한 분석을 통해 용존산소와 pH가 조류발생과 높은 상관관계를 보임을 확인할 수 있었다.

• Journal of Electrochemical Science and Technology
• /
• 제13권3호
• /
• pp.369-376
• /
• 2022

In this study, the stability of an anion exchange membrane water electrolyzer (AEMWE) cell was evaluated in an on-off cycling operation with respect to an applied electric bias, i.e., a current density of 500 mA cm^-2, and an open circuit. The ohmic and polarization resistances of the system were monitored during operation (~800 h) using electrochemical impedance spectra. Specific consideration was given to the ohmic resistance of the cell, especially that of the membrane under on-off cycling conditions, by consistently feeding the cell with KOH solution. Owing to an excess feed solution, a momentary increase in the polarization resistance was observed immediately after the open-circuit. The excess feed solution was mostly recovered by subjecting the cell to the applied electric bias. Stability tests on the AEMWE cell under on-off cycling with continuous feeding even under an open circuit can guarantee long-term stability by avoiding an irreversible increase in ohmic and polarization resistances.

• 전기학회논문지
• /
• 제66권7호
• /
• pp.1066-1071
• /
• 2017

Recently high voltage impulse (HVI) technique has been extensively studied for desalting processes to control the $CaCO_3$ scale formation in industrial water practices such as power plant, boiler, and heat exchange operations. Investigation of the operational parameters for the HVI is important, however, those had not been reported yet. In this study, the effect of initial feed volume and contact time on reduction of calcium ion concentration by the HVI technique was investigated. Initial feed volumes of artificial hard water which contained 100 mg/L of $Ca^{2+}$, were set to 1, 2, and 3 L respectively. After 24hr of HVI contact with 12kV, $Ca^{2+}$ ion was reduced to 50, 29 and 19 % of their initial concentration, indicating that calcium removal increased as initial feed volume decreased. This implies the applied HVI pulse energy per unit mass of calcium is important parameter determining overall desalting efficiency. A series of extended operations of HVI up to 30 days verified the long term stability of the HVI system. The calcium ion declined to 40 mg/L after 2~3 days, and further reduction of calcium was not achieved, indicating that optimum operation time could be 2~3 days under these experimental conditions. Consequently, it was confirmed that the important operational parameter of HVI technique is initial feed volume and contact time as well as the applied voltage that was already proven in the previous study.

• 대한수의학회지
• /
• 제44권4호
• /
• pp.593-605
• /
• 2004

An egg has been considered as one of the most important food sources because of it's nutritional superiority and reasonable price. With the complexity of egg flow system from production to consumption in Korea, preventive measures for egg safety have been required. Therefore, our study was carried out to analyze hazards for the egg under farm level and develope preventive measures with a purpose of obtaining egg safety. To analyze biological hazards, microbial contamination of egg(normal, dirty and cracked), water, feed, manure and equipments associated with laying were investigated. One isolate of Salmonella enteritidis and S. bardo were detected from the manure and dirty egg shell respectively. The sanitary conditions in the farm were surveyed by questionaries. Confirmation of vaccination for purchasing chicks and establishment of sanitary guidances for water and type of water suppliers ought to be preceded. Feed supplier systems including feed tanks, feed pipes and hoppers were known that their contamination might give it a chance to infect individuals and egg content and shell. The safe and rapid disposal of dead chickens and rodent were reported as more crucial factors to prevent infectious disease and manage good sanitation. Egg selector and collecting belt should be kept properly not to be contaminated from egg fluids and feces. It should be also considered that regular gathering of eggs, removal of dirty or cracked ones, storage under refrigeration and the use of disposable egg tray were continuously fulfilled. Conclusively, Our results suggested that HACCP-based system for providing fresh and safe eggs to consumers should be applied to the farm.