• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.395-402
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• 2001

The gasoline engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc, in the engine, Thine film instantaneous temperature measurement probe was made. And the manufactural method of probe was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured by this probe and the heat flux was obtained by Fourier analysis. The authors measured the wall temperature of combustion chamber and computed the heat flux through the cylinder wall in order to understand the combustion characteristics depending on height of probe. For achieving this goal, the thin film instantaneous temperature probe was developed for analyzing the instantaneous surface wall temperature and unsteady heat flux on the constant volume combustion chamber.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1218-1222
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• 2007

Under various tunnel fires, smoke average temperature and volume flow rate in a tunnel fire are calculated. To obtain realistic results, enthalpy of smoke which composites combustion gases and entrainment air is calculated from curvefit polynomials by temperature.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.4
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• pp.216-223
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• 2003

In the production of internal combustion engines, there have been trends to develop the high performance engines with improved fuel efficiency, lighter weights and smaller sizes. This trends help to answer problems related to thermal load and abnormal combustion, etc. in these engines. In order to investigate these problems, a thin film-type probe and its manufacturing method for instantaneously measuring surface-temperatures have been proposed in this study, Instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and heat flux was obtained by Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe have been measured. To achieve the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.644-648
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• 2009

Temperature dependency of resistivity of the carbon black-polyethylene composites below and above percolation threshold is studied based on the electrical conduction mechanism. Temperature coefficient of resistance of the composites below percolation threshold changed from minus to plus, increasing volume fraction of carbon black; this trend decreased with increasing volume fraction of carbon black. The temperature dependence of resistivity of the composites below percolation threshold can be explained with a tunneling conduction model by incorporating the effect of thermal expansion of the composites into a tunneling gap. Temperature coefficient of resistance of the composites above percolation threshold was positive and its absolute value increased with increasing volume fraction of carbon black. By assuming that the electrical conduction through percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of carbon black, the temperature dependency of the resistivity above percolation threshold has been well explained without violating the universal law of conductivity. The apparent activation energy is estimated to be 0.14 eV.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.81-88
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• 1996

In order to investigate the electrical properties of transformer oils for large power, the characteristics of AC and Impulse breakdown in gap length of 1.0~2.5mm and that of volume resistivity were researched in temperature range of 20~$100^{\circ}C$. An geometrical capacitance of electrode with coaxial cylindrical shape for measuring the volume resistivity was 16pF, and highmegohm meter with model no. VMG-1000 was used, and also the applied voltage were DC 100, 250 and 500V. In the dependance of breakdown characteristics due to electrode gap length, it was confirmed that breakdown voltage was nearly uniform by volume effect according to the increase of gap. In the characteristics for AC breakdown, the dielectric strength was increased to $90^{\circ}C$ but decreased over $90^{\circ}C$, and also in case of impulse breakdown, it was increased to 7$0^{\circ}C$ and at dated $70^{\circ}C$ over in temperature range. The calculated mobility of oils in the characteristics for impulse breakdown were about $10^{-5}$~$10^{-4}cm^2/V{\cdot}S$, and the value of volume resistivity was almost invariable in low temperature range, regardless of voltage by the stable thermal properties, and it indicated a peak at $50^{\circ}C$ and had a sudden change to decrease over that temperature, and also the value of volume resistivity in 250V/mm at $80^{\circ}C$ is suitable for the International electrical standards, it was confirmed.

• Journal of Korea Foundry Society
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• v.11 no.4
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• pp.323-330
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• 1991

The relationships between the microstructure changes, retained austenite volume and elevated temperature tensile properties of Mo-Ni-Cu ADI corresponding to various austempering temperatures and time were investigated, After the $250^{\circ}C$ tensile test for the test piece austempered at $270^{\circ}C$ the accicular bainite structure was observed blunted under room temperature microscope. In the case of $370^{\circ}C$ austempering, the feathery bainite lath spacing was observed broadened. But after the $450^{\circ}C$ tensile test, bainitic features could not be observed. As the testing temperature increased, retained austenite volume tested at room temperature decreased. Especially, after the $450^{\circ}C$ tensile test retained austenite volume approached nearly to zero. A little higher tensile properties appeared at $250^{\circ}C$ testing than those at room temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.624-632
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• 2003

In the gasoline engine industry. there has been a trend towards the development of high performance engines with improved fuel efficiency, reduced weight and smaller sizes. These trends help to solved engine problems related to thermal load and abnormal combustion. In order to investigate these Problems, a thin film-type probe for instantaneously measuring temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and the heat flux was obtained through Fourier analysis. A peak instantaneous temperature was obtained after 55∼60 ms from ignition and the temperature increased according to an equivalence ratio and varied differently according to the position of the probe. Total heat loss during combustion period was affected by the equivalence ratio and differed widely in accordance to the position of the probe.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.336-341
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• 2019

The gas adsorption isotherm requires accurate measurement for the analysis of porous materials and is used as an index of surface area, pore distribution, and adsorption amount of gas. Basically, adsorption isotherms of porous materials are measured conventionally at 77K and 87K using liquid nitrogen and liquid argon. The cold volume calibration in this conventional method is done simply by splitting a sample cell into two zones (cold and warm volumes) by controlling the level sensor in a Dewar filled with liquid nitrogen or argon. As a result, BET measurement for textural properties is mainly limited to liquefied gases (i.e. $N_2$ or Ar) at atmospheric pressure. In order to independently investigate other gases (e.g. hydrogen isotopes) at cryogenic temperature, a novel temperature control system in the sample cell is required, and consequently cold volume calibration at various temperatures becomes more important. In this study, a cryocooler system is installed in a commercially available BET device to control the sample cell temperature, and the automated cold volume calibration method of temperature variation is introduced. This developed calibration method presents a reliable and reproducible method of cryogenic measurement for hydrogen isotope separation in porous materials, and also provides large flexibility for evaluating various other gases at various temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.67-68
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• 2015

Recently, usage of ultra-high strengh concrete(UHSC) have been increased. Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Therefore, this study evaluated effect of the coarse Aggregate volume by high temperature mechanical properties of UHSC. Residual mechanical properties are evaluated under fine aggregate ratio 40,60% and 500℃ temperature on UHSC of W/B 15, 20%. As result, residual mechanical properties of UHSC are high by lower coarse aggregate volume.

• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.1-8
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• 2012

To understand growth characteristics of eight dominant red tide species ($Prorocentrum$ $minimum$, $Heterocapsa$ $triquetra$, $Scrippsiella$ $trochoidea$, $Akashiwo$ $sanguinea$, $Chattonella$ $marina$, $Heterosigma$ $akashiwo$, $Amphidinium$ $carterae$ and $Rhodomonas$ $salina$) in the Korean coastal water, the growth rates were examined in relation with the impacts of water temperature and bio-volume. Of these, $P.$ $minimum$, $C.$ $marina$, $H.$ $akashiwo$, $A.$ $carterae$ and $R.$ $salina$ were eurythermal species with relatively high growth rates in a borad ranges (15 to $25^{\circ}C$) of water temperature. On the other hand, the growth rate of $H.$ $triquetra$, $S.$ $trochoidea$ and $A.$ $sanguinea$ were high in relatively mid temperature (optimum: $25^{\circ}C$) condition. In particular, $H.$ $triquetra$ was well adapted in low temperature of 5 to $15^{\circ}C$, implying that the species can survive and grows even at very low temperature. Based on results of our experiment, the growth characterestics of five eurythermal species and three mid temperature species may have dominated in Korean coastal water during summer season and fall season, respectively. Contrastively, the growth characteristics of $H.$ $triquetra$ make a consistently dominant during the cold winter season. In addition, the growth rates of large bio-volume species were lower than those of small bio-volume species, indicates that growth of single cells of several flagellates might be depended on the cells sizes.