• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.473-479
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• 2004

A sedimentation basin (SB) at the inlet of an irrigation reservoir which was constructed using an auxiliary dam was monitored to evaluate its pollutant removal efficiency. Water sampling at three points, i.e., inflow stream, upstream and downstream of the reservoir, were taken 5 times before and after the construction of the SB in 1999 and 2003, respectively. No significant water quality variations in inflow stream were observed during these periods. The COD, T-N, T-P and SS removal efficiencies were 38, 24, 35 and 49%, respectively. The results indicated that those removal efficiencies significantly increased during the rainy season and COD removal efficiency, especially, was higher than others studies. The scale of SB in this study was rational as aspects of pollutant removal efficiency and hydraulic detention time. And it is recommended that SB, at inlet of an reservoir, should be constructed as completely separated structure from reservoir water body and having SAR Index from 0.7% to 1.0%.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.150-160
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• 2011

This study focuses on the Achard turbine, a vertical axis, cross-flow, marine current turbine module. Similar modules can be superposed to form towers. A marine or river hydropower farm consists of a cluster of barges, each gathering several parallel rows of towers, running in stabilized current. Two-dimensional numerical modelling is performed in a horizontal cross-section of all towers, using FLUENT and COMSOL Multiphysics. Numerical models validation with experimental results is performed through the velocity distribution, depicted by Acoustic Doppler Velocimetry, in the wake of the middle turbine within a farm model. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The overall farm efficiency, with respect to the spatial arrangement of the towers, was depicted by 2D modelling of the unsteady flow inside the farm, using COMSOL Multiphysics. Rows of overlapping parallel towers ensure the increase of global efficiency of the farm.

• Korean Journal of Environmental Agriculture
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• v.20 no.3
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• pp.143-149
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• 2001

A contact oxidation canal system with sedimentation basin was installed to study the efficiency of water quality purification. The primary sedimentation basin with 60 min of HRT (Hydraulic Retention Time) included in the system was aimed to sediment pollutants in the water and the deposit being released by the drainage culvert located at the bottom of the system. The oxidation canal aerated by nozzle was to contact the pollutants and oxygen in the surface of plastic filter to purify the water. Discharge, HRT, length of the oxidation canal were $200\;m^3/day$, 90 min, 20 m, respectively. The treatment efficiency of total nitrogen was lower compared with other water quality items such as SS, BOD, TP because the anoxic condition for denitrification was not ensured after the oxidation canal. However, $25%{\sim}89.6%$ of SS, $75.0%{\sim}91.5%$ of BOD, $44.3%{\sim}95.3%$ of TP were removed in this system. Overall, the results indicates that this system appears to have a potential capability for water quality improvement of the reservoirs or the canals in the agricultural watershed.

• Journal of Environmental Health Sciences
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• v.37 no.1
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• pp.64-72
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• 2011

This study was performed to assess the removal efficiency on nitrogen, phosphorus and organic carbon in wastewater by spatial separation and internal recycling in a modified oxidation ditch process (modified OD). The performances of the modified OD were evaluated via laboratory-scale experiments. The process was operated at hydraulic retention times of 6-48 hours and solid retention times of 17-38 days. We found that organic carbon removal efficiency increased after the modified OD operation period. T-N removal efficiency remained stable; average T-N concentration of effluent was 8.02 mg/l after modified OD operation. In contrast, T-P concentration of effluent was over 1 mg/l. Nitrogen and phosphorus removal efficiency of modified OD at HRT 12 hr were 83.1% and 74.1%, respectively. Also, maximum efficiency was found at SRTs from 20 to 30 days. T-N removal efficiency was 83.1% at a C/N ratio from 3.0 to 3.5. However, T-N removal efficiency decreased at C/N ratios over 3.5. Also, T-P removal efficiency increased with HRT at C/P ratios in the same condition. Maximum efficiency was 74.1% at a C/P ratio from 25 to 28. T-N removal efficiency was 79.2% and T-P removal efficiency was 65.3% after M4 mode operation (added to the internal recycle line connected to the anoxic reactor). The modified OD with spatial separation and internal recycling developed in this study is, therefore, believed to be an improvement for solving problems in the nutrient removal technologies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.701-702
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• 2011

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.1
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• pp.16-23
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• 2001

Hydraulic transport of fines up to the surface of flotation cell was supposed to be a mechanism of fines fractionation through the froth-flotation. Efficient fractionation of fines means efficient skimming out of flotation rejects as much as possible with least long fiber loss. The selectivity of fines fractionation was found to be mainly affected by long fibers flocculation degree in this study. Lack of sufficient flocculation of long fibers could lead to extensive loss of long fibers. It was also found that higher flotation flux caused higher flotation reject as well as the increase of long fiber loss, but did not affect the fine content ratio in the flotation reject. We controlled the flotation flux and the stock consistency, and chose a cationic polymer to maximize the flocculation of long fibers and to increase the amount of flotation reject. The highest efficiency of fines fractionation was obtained at 1.3% of stock consistency and at 100L/min of flotation flux in our experimental set up. The cationaic polymer we chose was found to be very effective in fiber flocculation and flotation froth stabilization. New definitions of fractionation efficiency were introduced in this study to compare the results more clearly.

• Journal of Biosystems Engineering
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• v.43 no.1
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• Environmental Engineering Research
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• v.23 no.1
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• pp.70-75
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• 2018

A pilot scale anaerobic fixed-bed with a reactor volume of $2.8m^3$ was built to treat slaughterhouse wastewater. Bamboo rings were chosen as support media mainly because of their cheaper price in underdeveloped countries. Even with their lower porosity and specific surface, the reactor performance showed a maximum 95% COD removal efficiency at an organic loading rate (OLR) of $1kg\;COD/m^3-d$ with its corresponding hydraulic retention time (HRT) of 7.5 d. At a higher OLR of $4.0kg\;COD/m^3-d$, the COD removal efficiency of 75% was achieved with an HRT of 2 d. No big difference in COD removal efficiencies was found between the reactors operated in both upflow and downflow modes. Their operational behavior and effluent characteristics were similar. The effluent COD/TKN ratio of 6.67 at an OLR of $4.0kg\;COD/m^3-d$ was only marginal acceptable range for a subsequent biological denitrification process. Otherwise carbon supplementation is required at a lower OLR.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.186-193
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• 2000

EPS(Electric Power Steering) systems have many advantages over traditional hydraulic power steering systems in space efficiency engine efficiency and environmental compatibility. In this paper an EPS system control logic using a torque map is proposed. The main function of the EPS system is to reduce the steering torque exerted by a driver by assist of an electric motor. Vehcile speed steering torque and steering wheel angle are measured and fed back to the EPS control system where appropriate assist torque is generated to assist the operator's steering effort. Another capability of the EPS system for easy adaptation to different steering feels via simple tuning is demonstrated by the experiments. It will be also verified that the EPS system can also improve damping and return performance of the steering wheel by control of the assist motor.

• The KSFM Journal of Fluid Machinery
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• v.14 no.1
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• pp.61-65
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• 2011

A series of water tests of a fuel pump for liquid rocket engines are performed at a room temperature. According to the test results, the head coefficient of the pump follows the conventional similarity rule - unlike this, the pump shows better efficiency with higher rotational speed. Also, it is found that the pressure at the rear bearing outlet is higher than expected because the inlet of bypass pipe line is narrow. Furthermore, the cavitation performance of the fuel pump is found to be sufficient for the engine operation and is better at the lower flow ratio and higher rotational speed.