• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.2
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• pp.103-110
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• 2016

Fine wires made from platinum have been used as sensors to evaluate the convection performance of nanofluids. However, the wire sensor is difficult to handle due to its fragility. Additionally, an unrealistic convective heat transfer coefficient (h) is obtained if a rigorous calibration process combined with precision equipment is not used for measurement. This paper proposes a new evaluation apparatus for h of nanofluids that uses a thermistor sensor instead of the platinum wire. The working principles are also explained in detail. Validation experiments for pure engine oil comparing h from the two sensors confirmed numerous practical benefits of the thermistor. The proposed system can be used as a useful tool to justify the adoption of developed nanofluids.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.17-24
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• 1986

β'-Sialon with different compositions was synthesized by the carbothermal reduction-nitridation of compacts containing kaolin graphite and silicon or aluminum at temperature of 1300-1450℃ under flowing gas of 90% N2-10% H2 or 20hrs. Quantitative analysis of minerals which were formed in the specimens was carried out by using the calibration curve which has been prepared from X-ray diffraction patterns. The obtained results were as follows : 1. In the formation of β'-Sialon by carbothermal reduction-nutridation of Si-Al-O-C system mixtures at 1400℃ for 20hrs. (2) β'-Sialon as a major mineral and α-Al2O3 as a minor mineral were identified in the specimen which was prepared of kaolin and graphite. (3)α-Al2O3 and 15R as a minor minerals were measured in the specimen which was prepared of kaolin aluminum and graphite. (4) AlN instead of α-Al2O3 and 15R was formed in the compacts that excess graphite(=35 wt%) was added to the mixture of kaolin and aluminium. 2. As the reaction time and temperature were increased the formation of β'-Sialon was increased whereas the phases of mllite SiC and Si2ON2 were decreased gradually.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1142-1146
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• 2004

The objective of this study is to the test applicability of SLURP on Soyanggang-dam watershed. The area of this watershed is $2,694km^2$ and mean elevation and slope is 650 m and $23^{\circ}$ respectively. Topographical parameters were derived from DEM using TOPAZ and SLURPAZ. NDVI was calculated from multi-temporal NOAA/AVHRR images. The daily meteorological data and hydrograph during $1999\~2001$ were selected for model calibration and performance tests. Weather elements (dew-point temperature, solar radiation, maximum and minimum temperature, relative humidity) were required from the S meteorological stations near the study area. The model parameters of each land cover class were optimized by sensitivity analysis and SCE-UA method. Runoff rate shows $49.33\%\~64.06\%$. Simulated results during 4 years were estimated by Nash-Sutcliffe efficiency and WMO volume error. Nash-Sutcliffe efficiency shows $0.61\~0.75$ and WMO volume error shows $6.1\%-18.8\%$.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.201-207
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• 2001

The dielectric relaxation study for aniline-dimethylsulphoxide (DMSO) and aniline-dim.ethylformamide(DMF) has been carried out using the Time domain reflectometry (TDR) technique, at different temperature and concentrations, in the frequency range of 10 MHz to 10 GHz. The dielectric parameters viz. static permittivity, relaxation time, the Kirkwood correlation factor, excess permittivity, excess inverse relaxation time and thermodynamic parameters have been obtained. The calibration method based on least squares fit method has been used. The dielectric parameters show systematic change with temperature and concentrations.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.232-234
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• 2000

Determination of uric acid by electrochemical method using ultrasonic stimulation has been investigated. Effects of sonication power, sonication time, pH of the solution and temperature were studied to obtain the optimal analytical conditions. The stability of the electrode was also examined. The optimal conditions for the sonovoltammetric determination of uric acid were as follows: temperature, $25.0^{\circ}C$ pH 7.0; sonication power, $20W/cm^2$. The calibration curve for the determination of uric acid by sono-LSV was linear over the range of$8.0{\times}10^{-6}\~5.0\times10^{-4}M$ and the limit of detection was $6.5\times10^{-6}M$.

• Analytical Science and Technology
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• v.14 no.6
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• pp.471-475
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• 2001

Solid phase microextraction(SPME) with $85{\mu}m$-polyacrylate (PA) and $100{\mu}m$-polydimethylsiloxane(PDMS) fibers, coupled to gas chromatography-mass spectrometry was used to determine 1,2-dibromo-3-chloropropane(DBCP) and n-butylbenzene in water. The conditions affecting the SPME process(i.e, extraction time, injection length, injection temperature, desorption time and temperature) were optimized. The linearity of the calibration curve (correlation coefficient, R) was over 0.99 and the limits of detection of the method were between 1.5 and $10.8{\mu}g/L$. Repeatability of the method was between 10.4 and 14.4 %.

• Journal of Korean Society on Water Environment
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• v.35 no.2
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• pp.131-144
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• 2019

Climate Change affects the hydrological cycle in agricultural watersheds through rising air temperature and changing rainfall patterns. Agricultural watersheds in Korea are characterized by extensive paddy fields and intensive water use, a resource that is under stress from the changing climate. This study analyzed the effects of climate change on river flows for Geum Cheon and Eun-San Choen watershed using STREAM, a semi-distributed watershed model. In order to evaluate the performance and improve the reliability of the model, calibration and validation of the model was done for one flow observation point and three reservoir water storage ratio points. Climate change scenarios were based on RCP data provided by the Korea Meteorological Administration (KMA) and bias corrections were done using the Quantile Mapping method to minimize the uncertainties in the results produced by the climate model to the local scale. Because of water mass-balance, evapotranspiration tended to increase steadily with an increase in air temperature, while the increase in RCP 8.5 scenario resulted in higher RCP 4.5 scenario. The increase in evapotranspiration led to a decrease in the river flow, particularly the decrease in the surface runoff. In the paddy agricultural watershed, irrigation water demand is expected to increase despite an increase in rainfall owing to the high evapotranspiration rates occasioned by climate change.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.6
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• pp.29-34
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• 2018

In this research, regarding the cement supplied to ready mixed concrete plant, the feasibility of rapid acquisition test for cement fineness using hydrometer which used for early strength evaluation of concrete was analyzed. Additionally, regarding the rapid test with hydrometer control factors were provided. As a result of analysis, quality control using hydrometer was possible with the regressive equation obtained in five minute between density of suspension and fineness of cement powder. As the control factors, dispersing admixture, replacing kerosene as a medium, and temperature of cement and water were evaluated. According to the control factor evaluation, the tap water was optimum as a medium and calibration of keeping the temperature of water to $20^{\circ}C$ or correction factor was needed for density results. Finally, it is considered that the suggested rapid quality evaluation method using hydrometer is cheaper and easier method than currently used Blaine test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.455-462
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• 2016

Output Characteristics of the spaceborn image sensor such as infrared(IR) sensor are varied according to time elapses and sensor repetition on/off operation. As a result, the quality of IR sensor image is decreased. Therefore, spaceborne image sensor require a periodic calibration using a black body system by correcting a non-uniformity of the sensor. In this paper, we proposed a MEMS-based black body system that can implement the high temperature uniformity at various standard temperatures ranging from low to high temperature and easily estimate the representative surface temperature. In addition, it has advantages lightweight, low-power and high accuracy. The feasibility of the proposed MEMS-based black body system was verified through the thermal analysis.

• Journal of Ocean Engineering and Technology
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• v.29 no.2
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• pp.169-174
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• 2015

This paper addresses experimental methodologies to measure the temperature-dependent thermal conductivity of the insulation materials popularly used for LNG cargo containment systems. The measurement techniques considered in this paper are the guarded hot plate (GHP) method and heat flow method (HFM). The former is based on the power supplied to the hot plate to keep the temperature constant, and the latter is based on a direct heat flux measurement. In order to improve the accuracy of the HFM, the thermal conductivity obtained by GHP was cross-compared with the HFM results, and a calibration factor was derived. It was found that the thermal conductivities measured by the two methods corresponded well under room temperature, but the deviation tended to slightly increase as the temperature decreased. Because of the easy installation and operability of HFM, it can be used to measure thermal conductivity in a large scale mock-up test or unit insulation panel test, where the GHP method is difficult to apply.