• Economic and Environmental Geology
• /
• v.37 no.5
• /
• pp.499-508
• /
• 2004

Changwon City first constructed riverbank filtration plants in Book-Myeon and Daesan-Myeon in Korea in the year 2001. This study evaluated hydrogeological characteristics and groundwater flow simulation between the Nakdong River and the fluvial aquifers adjacent to the river in Book-Myeon, Changwon City. The groundwater simulation calculated the influx rate from the Nakdong River and the fluvial aquifers to pumping wells through the riverbank filtration system. The groundwater flow model utilized drilling, grain size analysis, pumping test, groundwater level measurements, river water discharge and rainfall data. Hydraulic heads calculated by the steady-state model closely matched measured heads in pumping and observation wells. According to the transient flow model, using a total pumping amount of 14,000 $m^3$/day, the flux into the pumping wells from the Nakdong River accounts for 8,390 $m^3$/day (60%), 590 $m^3$/day (4%) is from the aquifer in the rectilinea. direction to the Nakdong River, and 5,020 $m^3$/day (36%) is from the aquifer in the parallel direction to the Nakdong River. The particle tracking analysis shows that a particle from the Nakdong River moves toward the pumping wells at a rate of about 1.85 m/day and a particle from the aquifer moves toward the pumping wells at a rate of about 0.75 m/day. This study contributes to surface water/groundwater management modeling, and helps in understanding, how seasonal change affects pumping rates, water quality, and natural recharge.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.7
• /
• pp.459-466
• /
• 2012

In order to improved treatment performance of dielectric barrier discharge (DBD) plasma, plasm + UV process and gas-liquid mixing method has been investigated. This study investigated the degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the generation of OH radical). The basic DBD plasma reactor of this study consisted of a plasma reactor (consist of quartz dielectric tube, titanium discharge (inner) and ground (outer) electrode), air and power supply system. Improvement of plasma reactor was done by the combined basic plasma reactor with the UV process, adapt of gas-liquid mixer. The effect of UV power of plasma + UV process (0~10 W), gas-liquid mixing existence and type of mixer, air flow rate (1~6 L/min), range of diffuser pore size (16~$160{\mu}m$), water circulation rate (2.8~9.4 L/min) and UV power of improved plasma + UV process (0~10 W) were evaluated. The experimental results showed that RNO degradation of optimum plasma + UV process was 7.36% higher than that of the basic plasma reactor. It was observed that the RNO decomposition of gas-liquid mixing method was higher than that of the plasma + UV process. Performance for RNO degradation with gas-liquid mixing method lie in: gas-liquid mixing type > pump type > basic reactor. RNO degradation of improved reactor which is adapted gas-liquid mixer of diffuser type showed increase of 17.42% removal efficiency. The optimum air flow rate, range of diffuser pore size and water circulation rate for the RNO degradation at improved reactor system were 4 L/min, 40~$100{\mu}m$ and 6.9 L/min, respectively. Synergistic effect of gas-liquid mixing plasma + UV process was found to be insignificant.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.1
• /
• pp.42-47
• /
• 2016

This paper presents the development of a floating outboard type of compact water jet propulsion system. The planning case of the water jet system is developed by performing precision processing after manufacturing FRP (Fiber Reinforced Plastics) from plug mold casting. This system is composed of an intake, impeller, diffuser, reverse bucket, and main shaft. In addition, a rebuilt engine was applied through marine engineering. The water jet propulsion system performance was verified to discharge a maximum $0.29m^3/s$ of flow rate and 37 m/s of flow velocity in a test pool on land. A field test was performed by installing the water jet propulsion device on board a ship that was tested off the coast of Korea. The weight of the hull, engine, and other equipment was approximately 1.2 tons, and the sailing speed was a maximum 22 knots at 3,600 rpm.

• Nuclear Engineering and Technology
• /
• v.31 no.4
• /
• pp.375-384
• /
• 1999

The credibility of CHECWORKS FAC model analysis was evaluated for plant application in a model plant chosen for demonstration. The operation condition at each pipe component was defined before the wear rate analysis by plant data base, water chemistry analysis, and network flow analysis. The predicted wear was compared with the measured wear for 57 sample components selected from 43 susceptible line groups analysed. The inspected 57 locations represent components of highest predicted wear in each line group. Both absolute value and relative ranking comparisons indicated reasonable correlations between the predicted and the measured values. Four components showed much higher measured wear rates than the predicted ones in the feed water train from main feed water pump discharge to steam generator, probably due to high hydrazine concentration operation the effect of which had not been incorporated into the CHECWORKS model. The measured wear was higher than the predicted one consistently for components with least susceptibility to FAC. It is believed that the conservatism maintained during UT data analysis dominated the measurement accuracy. A great deal of enhancement is anticipated over the current plant pipe management program when a comprehensive plant pipe management program is implemented based on the model analysis.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1268-1270
• /
• 1994

Fine lithographic technology in a submicron design regime is necessary for the fabrication of VLSI circuits. In such lithography, fine pattern delineation is performed by electron beam, ion beam and X-ray lithography instead of photolithography. Therefore, the new resist materials and development method have been required. So, we are investigating another positive E-beam resists which have high sensitivity and dry etching resistance, Plasma co-polymerized resist was prepared using an interelectrode gas-flow-type reacter. Methymethacrylate, tetramethyltin and styrene were chosen as the monomer to be used. The delineated pattern in the resist was developed with gas-flow-type reactor using an argon and 02 as etching gas. We studied about the effects of discharge power and mixing rate of the co-polymerized thin :film. The molecular structure of thin film was investigated by ESCA and IR, and then was discussed in relation to its quality as a resist.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.5
• /
• pp.558-566
• /
• 2007

The performance characteristics of water-chilling heat pump using $CO_2$ with respect to variation of refrigerant charge amount was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter-flow-type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2400 mm length. The experimental results summarize as the followings : As the refrigerant charge ratio of $CO_2$ heat pump system increases, the discharge pressure and compressor ratio increases, but mass flow rate of refrigerant decreases. Also the compressor work increases with the increase of refrigerant charge ratio. However, the heating and cooling capacity of $CO_2$ heat pump decreases as the refrigerant charge ratio increases. The maximum heating COP of $CO_2$ heat pump system presented at 0.25 refrigerant charge ratio. It is possible to confirm the optimum charge ratio of $CO_2$ heat pump system by the viewpoint of heating COP.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.12
• /
• pp.823-829
• /
• 2012

In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The experimental setup of a MAC consists of an belt driven compressor, a condenser, an evaporator and a block type thermal expansion valve. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The compressor discharge temperature of R1234yf is $8^{\circ}C$ lower than that of R134a. The cooling capacity with R1234yf system decreased by 4~7% compared with R134a system. In addition, The COP of R1234yf system is lower 3~4% than that of R134a system.

• Geomechanics and Engineering
• /
• v.35 no.6
• /
• pp.571-580
• /
• 2023

During EPB shield tunnelling, construction speed and safety are severely affected by spewing. In this study, a theoretical seepage model is established to capture of the effects of screw conveyor geometry and turbulent flow on spewing. Experimental test results are used to verify the proposed theoretical seepage model. It is found that the seepage is greatly affected by the length of screw conveyor and soil permeability. The proposed model can increase the screw conveyor length and reduce soil discharge sections simultaneously, the permeability of treated muck thus decreases by one order of magnitude. By using the proposed theoretical seepage model, the criterion of critical soil permeability used to identify spewing is proposed. When the water head applied at tunnel face reaches 40 m and 50 m, the critical permeability coefficients of treated muck should be less than 10^-5 m/s and 10^-6 m/s to avoid spewing. For a given permeability coefficient of soil, the water flow rate is overestimated if structural characteristics of screw conveyor is not considered. Consequently, the occurrence of spewing is greatly overestimated, which increases construction cost substantially.

• Journal of Korean Society for Atmospheric Environment
• /
• v.30 no.4
• /
• pp.339-349
• /
• 2014

$CO_2$ emission has been gradually increased due to rising fossil fuel use. A gliding arc plasma scrubber (GAPS) was proposed to destruct $CO_2$. For optimum design of GAPS, a CFD analysis has been conducted in different configuration for the system. The parameters considered included gas injection velocity at the nozzle and gas flow rate to gap between electrodes. The reactor configuration affected velocity fields which caused changes in the mixture fraction and the retention time. The mixing effect of $CO_2$ and supplied gas ($CH_4$ and steam) was enhanced by installing a orifice baffle. This revealed that the orifice baffle is effective in $CO_2$ conversion by positioning the reactants in the gas into the center of plasma discharge.

• Tribology and Lubricants
• /
• v.20 no.4
• /
• pp.209-217
• /
• 2004

Lubrication characteristics between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump play an important role in volumetric efficiency and durability of pump. In this paper, a finite element method is presented for the computation of the pressure distribution between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump. Also, a Runge-Kutta method is applied to simulate the cylinder block dynamics of three-degrees of freedom motion. From the results of computation, we can draw two major conclusions. One is related to the fluid film characteristics between a cylinder block and a valve plate and the other is related to the average leakage that is determined by the pressure gradient and the clearance near the discharge port. The numerical results of cylinder block dynamics were compared with the experimental results using eddy-current type gap sensors those are fixed at a pump housing.