• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.119-130
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• 2019

This paper establishes an iterative calculation model for the hydrodynamic performance of propeller in oblique flow based on low order potential based surface panel method. The hydrodynamic performance of propeller is calculated through panel method which is also used to calculate the induced velocity. The slipstream of propeller is adjusted according to the inflow velocity and the induced velocity. The oblique flow is defined by the axial inflow velocity and the incident angle. The calculation results of an instance show that the thrust and torque of propeller decrease with the increase of axial inflow velocity but increase with the incident angle. The unsteadiness of loads on the propeller blade surface gets more intensified with the increases of axial inflow velocity and incident angle. However, comparing with the effect of axial inflow velocity on the unsteadiness of the hydrodynamic performance of propeller, the effect of the incident angle is more remarkable.

• Atmosphere
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• v.27 no.1
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• pp.67-77
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• 2017

In this study, we analyzed the characteristics of flow around the Daeyeon automatic weather station (AWS 942) and established formulas estimating inflow wind speeds at a computational fluid dynamics (CFD) model domain for the area around Pukyong national university using a computational fluid dynamics (CFD) model. Simulated wind directions at the AWS 942 were quite similar to those of inflows, but, simulated wind speeds at the AWS 942 decreased compared to inflow wind speeds except for the northerly case. The decrease in simulated wind speed at the AWS 942 resulted from the buildings around the AWS 942. In most cases, the AWS 942 was included within the wake region behind the buildings. Wind speeds at the inflow boundaries of the CFD model domain were estimated by comparing simulated wind speeds at the AWS 942 and inflow boundaries and systematically increasing inflow wind speeds from $1m\;s^{-1}$ to $17m\;s^{-1}$ with an increment of $2m\;s^{-1}$ at the reference height for 16 inflow directions. For each inflow direction, calculated wind speeds at the AWS 942 were fitted as the third order functions of the inflow wind speed by using the Marquardt-Levenberg least square method. Estimated inflow wind speeds by the established formulas were compared to wind speeds observed at 12 coastal AWSs near the AWS 942. The results showed that the estimated wind speeds fell within the inter quartile range of wind speeds observed at 12 coastal AWSs during the nighttime and were in close proximity to the upper whiskers during the daytime (12~15 h).

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.426-432
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• 2012

This study involves using nickel chloride solution as a raw material to produce nano-sized nickel oxide powder with average particle size below 50 nm by the spray pyrolysis reaction. The influence of the inflow speed of raw material solution on the properties of the produced powder is examined. When the inflow speed of the raw material solution is at 2 ml/min., the average particle size of the powder is 15~25 nm and the particle size distribution is relatively uniform. When the inflow speed of the solution increases to 10 ml/min., the average particle size of the powder increases to about 25 nm and the particle size distribution becomes much more uneven. When the inflow speed of the solution increases to 20 ml/min., the average particle size of the powder increases in comparison to the case in which the inflow speed of the solution was 10 ml/min. However, the particle size distribution is very uneven, showing various particle size distributions ranging from 10 nm to 70 nm. When the inflow speed of solution increases to 50 ml/min., the average particle size of the powder decreases in comparison to the case in which the inflow speed was 20 ml/min., and the particle size distribution shows more evenness. As the inflow speed of the solution increases from 2 ml/min. to 20 ml/min., the XRD peak intensities gradually increase, while the specific surface area decreases. When the inflow speed of solution increases to 50 ml/min., the XRD peak intensities rather decrease, while the specific surface area increases.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.396-402
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• 2011

In this study, by using tin chloride solution as a raw material, a nano-sized tin oxide powder with an average particle size below 50 nm is generated by a spray pyrolysis process. The properties of the generated tin oxide powder depending on the inflow speed of the raw material solution are examined. When the inflow speed of the raw material solution is 2 ml/min, the majority of generated particles appear in the shape of independent polygons with average size above 80-100 nm, while droplet-shaped particles show an average size of approximately 30 nm. When the inflow speed is increased to 5 ml/min, the ratio of independent particles decreases, and the average particle size is approximately 80-100 nm. When the inflow speed is increased to 20 ml/min, the ratio of droplet-shaped particles increases, whereas the ratio of independent particles with average size of 80-100 nm decreases. When the inflow speed is increased to 100 ml/min, the average size of the generated particles is around 30-40 nm, and most of them maintain a droplet shape. With a rise of inflow speed from 2 ml/min to 5 ml/min, a slight increase of the XRD peak intensity and a minor decrease of specific surface area are observed. When the inflow speed is increased to 20 ml/min, the XRD peak intensity falls dramatically, although a significant rise of specific surface area is observed. When the inflow speed is increased to 100 ml/min, the XRD peak intensity further decreases, while the specific surface area increases.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.33-45
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• 2014

In this study, current sewer infiltration/Inflow(I/I) computation and application method was examined about improvement and adequacy relating to the main issues raised by the field for practitioners. The results of review about infiltration calculation method were considered to be in need of improvement at 'standards of minimum sewage calculation'. Furthermore, the results of review about I/I application method were considered to be in need of improvement at 'standards of seasonal infiltration application' and 'the relative decrease in the Annual evaluation standards'. In addition, annual I/I analysis at JC County for the four years(2009~2012) in respect of operation flow and rainfall data was conducted. The result of annual infiltration analysis, compared average daily sewage generated average infiltration rate was found in 21.95 %, infiltration by unit was found in $0.31m^3/day/cm/km$ and $0.12m^3/day/day$, respectively. The result of annual inflow analysis, average rainfall - Inflow equations was found $y=5.499{\times}$($R^2$ 0.793), and the average Inflow quantity by sewer extension was predicted to $0.66m^3/mm-km$.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.1-10
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• 2022

Most wells developed in Jeju island before the enactment of the Groundwater Management Ordinance in 2002 are vulnerable to aquifer contamination due to inflow of upper groundwater having the high concentration of nitrate nitrogen, likely due to incomplete grouting in upper section of the wells. Although these wells require entire reinstallation, it is often necessary to rehabilitate the existing wells due to various constraints. Therefore, to identified the inflow section of contaminants, the thermal level sensor (TLS) technique was firstly applied for three wells, which enables to monitor temperature variations in every 50 cm depth. Then, the grouting material was injected to the upper section to prevent the inflow of upper contaminated groundwater into the entire aquifer. By applying TLS technique, it was found that the temperature deviations in the upper groundwater inflow section decreased sharply. Moreover, both the change in the concentration of nitrate nitrogen in the rainy/dry seasons and the average concentrations were found to decrease rapidly after grouting material injection. Consequently, the application of TLS proposed in the study turned out to be appropriate to prevent aquifer contamination.

• Journal of environmental and Sanitary engineering
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• v.10 no.1
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• pp.12-24
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• 1995

I tried to evaluate the reason of the monthly variation of water quality according to the hydrologic character of Pal- dang reservoir inflow variation. The result of this study is as below; 1 ) COD, BOD, Total- nitrogen and Total- phosphate concentration increase generally according to the flux and Total- phosphate concentration is the most affected item by flux. 2) COD, BOD, Total- nitrogen and Total- phosphate concentration increase according the flux, but they begin to decrease at the below point ; COD · 1,154 CMS, BOD : 1,007 (CMS cubicmeter per second ) and Inflow- Concentration interrelation formula is as below; table omitted.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.778-784
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• 2009

The purpose of this study is to figure out the differences of the inflow rates of Sewage Treatment Plants (STP), invested by public fund or public-private partnership (PPP). This paper finds that the average ratio of sewage inflow according to facility capacities (medium and small scale STP) was either nearly below 30% or above 100% in the first year. As the size of STP increased, there was decrease in the accuracy of demand assumption. This was because the operation time when the ratio of sewage inflow was uniform was different according to the size of STP, whereby the time was short when the STP were small. The design average ratio of sewage inflow was 10% larger than the real average ratio; this was considered overdesigned. In the case of a plant built by the PPP scheme, the average ratio of inflow of the STP before an abolition of MRG was larger than after the abolition of MRG. This may be explained by moral hazard from too much reliance on MRG. After the abolition of MRG, the demand risk of PPP was shifted from a PPP project to a conventional project.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.237-238
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• 2014

A correlation between an air inflow velocity and $NO_x$ emission is investigated numerically. The area of a swirl premixed burner is controlled geometrically to increase or decrease an air inflow velocity. When an air velocity increases, mixedness at the burner exit is improved and NO emission at the liner exit is reduced. Although the area of an air slit is the same, NO emission shows discrepancy due to difference of air slit shapes.

• Journal of Korea Water Resources Association
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• v.37 no.8
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• pp.653-662
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• 2004

In this study, the method of Increasing the flood control as well as conservation effects is studied by joint operation of Hwacheon and Peace Dam. After completing the second phase of the construction of the Peace Dam, the dam crest height will be increased from 225m and the storage capacity will also be increased. If storage capacity is increased and gates are installed, it will assist not only flood control but also conservation of the entire Han river basin. Considering the change of conservation levels, the change of the restricted water level of the Hwacheon Dam in flood season, and the inflow change into the Peace Dam through the simulated reservoir operation, the annual average power of Hwacheon Dam with 95% reliability, annual firm power, the volume of water supply is calculated. As a result, when the conservation level of the Peace Dam and the restricted water level of the Hwacheon Dam are increased, the generation capacity will be improved. However, even though the inflow decrease, the generation capacity will not be affected. If the inflow decrease under the same conditions, the water supply capability will be reduced to the range from 35% to 40%. It is necessary to increase conservation level to keep the same water supply capability.