• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.79-85
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• 2009

Low temperature combustion regime for the simultaneous reduction of nitrogen oxides ($NO_x$) and paticulate matter (PM) is demonstrated in single cylinder engine at various operating parameters, such as EGR rate, injection timing, EGR temperature, amount of fuel and swirl rate. Low temperature combustion is accomplished by high exhaust gas recirculation (EGR) rate in this study. Generally, the emission of $NO_x$ almost completely disappears and PM significantly increases in the first decreasing regime of oxygen concentration but after peaking about 10~12% oxygen concentration, PM then decreases regardless of fuel injection quantity. Low temperature combustion regime was extended by low EGR temperature, high injection pressure and low amount of fuel.

• The Korean Journal of Ecology
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• v.17 no.4
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• pp.485-499
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• 1994

This study was focused on the effect of the altitude on the geographical variations of germination characteristics in the populations of Plantago asiatica L. distribute in Mt. Chiri. There was a significant difference among the 14 groups in the phenological pattern in relation to altitudes. When the altitude becomes higher, the thermal time which was required for 10 to 80% germination rate showed higher and wider distribution. On the other hand, the germination response of increasing temperature (IT) and secreasing temperature (DT) regime was classified into 3 group. The first group was the spering germination type. This group showed that the IT regime hadhigher germination rate than that of the DT regime, and was distributed in Macheon(300m) and Packmudong (500m). The second was the spring-fall germination type which was distributed in Hadong (900m) and Saemt대 (1100m). This group also showed higher germination rate in the IT regime, but the difference of the germination rate between IT and DT regime was less than that in the first group (the spring type). The third group was the early fall germination type which was found in the Nogodan (1507m), Changetomok (1750m) and Cheonwangbong (1915m). The germination rate of this group showed almost 100% similarity between IT and DT regime. These data suggested that the geographical varations of germination characteristics within species was an important ecological strategy for the survival from severe environmental conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3297-3304
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• 1994

Experimental investigation have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution heated from below in a cylindrical cavity. The objective is to examine the process of mixed-layer formation, the flow phenomena, the heat transfer characteristics, and temperature and concentration distribution according to the changes in the effective Rayleigh number based on the reference height which represents the relation of temperature and concentration gradient. The types of initially formed flow pattern are categorized in three regimes depending on the effective Rayleigh number ; stagnant flow regime, single mixed-layer flow regime and successively formed multiple mixed-layer flow regime. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered flow regime, but both linear in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly. The layers expand by diffusion of concentration through the interface along with its random fluctuation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1731-1740
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• 1995

Experimental investigations have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution due to heating from below in a rotating cylindrical cavity. The objective is to examine the flow phenomena and the heat transfer characteristics according to the changes in temperature gradient, concentration gradient and rotating velocity of cavity. Thermal and solutal boundary conditions at side wall are adiabatic and impermeable, respectively. The top and bottom plate are maintained each at constant temperature and concentration. The cavity is put into a state of solid body rotation. Like the stationary case, the types of initially-formed flow pattern are classified into three regimes depending on the effective Rayleigh number and Taylor number; stagnant flow regime, single mixed-layer flow regime and successively formed multi-mixed layer flow regime. At the same effective Rayleigh number, the number of initially-formed mixed layer and its growth rate decrease as the effect of rotation increases. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered-flow regime, but look both liner in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.23-32
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• 1998

Al2O3/Al composites were produced by immersing the sintered silica preform in molten aluminum which contained magnesium as impurity. Three distinct regions existed in the penetration behavior of molten me-tal with changing the reaction temperature. These regions are denoted as low temperature regime(75$0^{\circ}C$-85$0^{\circ}C$) intermediate regime(90$0^{\circ}C$-95$0^{\circ}C$) and high temperature regime(100$0^{\circ}C$$\leq$) In the low temperature regime the penetration speed of molten aluminum increased with increasing reaction temperature whereas it decreased in the intermediate regime due to the phase transition of alumina formed by displacement reac-tion. In the high temperature regime the penetration speed of molten aluminum was the highest at 100$0^{\circ}C$ which was 3.6 mm/hr But above 105$0^{\circ}C$ molten aluminum did not penetrate into the silica preform because of the formation of a dense spinel layer at the preform surface by magnesium in molten Al.

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1425-1433
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• 2012

Water temperature in the eastern part of the Yellow Sea (EYS) during winter (JFM) and summer (JJA) from 1964 to 2009 and Siberian High Pressure Index (SHI) and Arctic Oscillation index (AOI) during winter (JFM) from 1950 to 2011 were used to analyze long-term variation in oceanic and atmospheric conditions and relationship between winter and summer bottom water temperature. Winter water temperature at 0, 30 and 50 m had fluctuated highly till the late of 1980s, but after this it was relatively stable. The long-term trends in winter water temperature at both depths were separated with cold regime and warm regime on the basis of the late 1980s. Winter water temperature at 0m and 50m during warm regime increased about $0.9^{\circ}C$ and $1.1^{\circ}C$ respectively compared to that during cold regime. Fluctuation pattern in winter water temperature matched well with SHI and AOI The SHI had negative correlation with water temperature at 0 m (r=-0.51) and 50 m (r=-0.58). On the other hand, the AO had positive correlation with Winter water temperature at 0 m (r=0.34) and 50 m (r=0.45). Cyclic fluctuation pattern of winter water temperature had a relation with SHI and AO, in particular two to six-year periodicity were dominant from the early of the 1970s to the early of the 1980s. Before the late of 1980s, change pattern in winter water temperature at 0 and 50 m was similar with that in the bottom water temperature during summer, but after this, relationship between two variables was low.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.18-25
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• 2020

The droplet impact behavior is dominated by some parameters such as surface temperature, We number, surface and fluid property. Especially, Leidenfrost effect which prevents the contact between surface and droplet is very powerful phenomenon for determining droplet impact behavior. Due to this effect, the impact regime is divided into contact boiling regime and film boiling regime whether the droplet contact with the surface. Many studies have found that surface micro-structures which processed by surface processing are effective to overcome the Leidenfrost effect. In this study, droplet impact behaviors were compared using ethanol both on flat and laser-ablated Al surface. On the flat surface, impact regime was mainly divided by surface temperature. And there is key dominant parameter for each regime. On the laser-ablated surface, we could see changed impact regime and different impact behavior such as jetting and ejection of tiny droplets despite of same impact conditions.

• The Korean Journal of Ecology
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• v.19 no.3
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• pp.231-240
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• 1996

The germination responses of Cassia mimosoides var. nomame seeds to temperature were examined under various conditions. The temperature range allowing germination was $20~40^{\circ}C$, and the linear relationship between the germination rate and temperature appeared to exist between $28~38^{\circ}C$ The total thermal time required for germination (10~80%) of C. mimosoides seeds ranged from 259 Kh (degree Kelvin$\times$hours) to 421 Kh and base temperature range was relatively constant, i.e., $23.39~26.68^{\circ}C$. In the increasing temperature (IT) regime, C. mimosoides seeds started to germinate at $16^{\circ}C$ and showed greater germination rate with increasing temperatures. The final germination rate was 64% at $36^{\circ}C$. On the other hand, in the decreasing temperature (DT) regime, the seeds began to germinate at $36^{\circ}C$, and the final germination rate was 52% at $20^{\circ}C$. An induced dormancy occurred at $16^{\circ}C$ in the DT regime.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.764-771
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• 2007

The objective of the present work is to evaluate the evaporation heat flux of deposited droplet on the hot surface by using of inverse heat transfer technique. On the basis of measured temperature, a integral form solution is determined for the transient temperatures beyond the two positions by using Green's function technique. This method first approximates the temperature data with a half polynomial series of time. we compared this result with constant radius model in single phase regime, nucleate boiling regime, film boiling regime respectively. this paper performed the experiments as following conditions: (a)the surface temperature is within the range between $80^{\circ}C\;and\;160^{\circ}C$ in the conduction, (b) droplet diameter are 2.4 and 3.0mm. (c) surface roughness is $0.18{\mu}m$.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.821-825
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• 2014

Steam gasification of sawdust char was performed in a thermobalance reactor at high temperature. Gasification temperature was changed from $850^{\circ}C$ to $1400^{\circ}C$ and steam partial pressure was 0.3, 0.5 and 0.7 atm. Three models of gas-solid reaction were applied to the reaction kinetics analysis and modified volumetric model was an appropriate model. Reaction control regime and diffusion control regime were distinct depending on the temperature. Apparent activation energy and pre-exponential factors for both of the regimes were evaluated and the effects of steam partial pressure were examined. $H_2$ concentration in the produced gas was two times higher than that of CO due to the gasification accompanying by the water gas shift reaction.