• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.340-343
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• 2007

The temperature variation of concrete pavement at early-age significantly affects the initiation and movement of joint cracks. For this analysis, we have built on IIA(Incheon International Airport) concrete pavement construction zone, and we measured the temperature and movement of the concrete slabs by using thermocouples, moisture sensors, V/W strain gages, and Demac discs. The analysis results showed that pavement's temperature significantly affected the joint movement. The widths of the joint cracks increased at evening and early in the morning when the temperature dropped but, those decreased in the day time when the temperature rose because of the effect of thermal expansion of the concrete slabs. The movements of the joints where the cracks never developed showed opposite trend to the cracked joints.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.72-77
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• 2011

This study is to investigate the effect of the distillation temperature in ultra low sulfur diesel fuel on exhaust emissions in the low-temperature diesel combustion with 1.9L common rail direct injection diesel engine. Low temperature diesel combustion was achieved by adopting an external high EGR rate with a strategic injection control. The engine was operated at 1500 rpm 2.6 bar BMEP. The 90% distillation recovery temperature (T90) was $270^{\circ}C$ and $340^{\circ}C$ for the respective cetane number (CN) 30 and 55. It was found that there exists no distinctive discrepancy on exhaust emissions with regards to the different T90s. The high CN (CN55) fuels follow the similar trend of exhaust emissions as observed in CN30 fuels' except that high T90 fuel (CN55-T340) produced higher PM compared to low T90 fuel (CN55-T270). This may come from that high T90 plays an active role in aggravating the degree of fuel-air mixture preparedness before ignition.

• Advances in concrete construction
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• v.5 no.5
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• pp.513-537
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• 2017

In this study, the fracture toughness $K_{IC}$ of high performance concrete (HPC) was investigated by conducting three-point bending tests on a total of 240 notched beams of $500mm{\times}100mm{\times}100mm$ subjected to heating temperatures up to $450^{\circ}C$ with exposure times up to 16 hours and various heating and cooling rates. For a heating rate of $3^{\circ}C/min$, $K_{IC}$ for the hot concrete sustained a monotonic decrease trend with the increasing heating temperature and exposure time, from $1.389MN/m^{1.5}$ at room temperature to $0.942MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.906MN/m^{1.5}$ for 8-hour exposure time and $0.866MN/m^{1.5}$ for 16-hour exposure time. For the cold concrete, $K_{IC}$ sustained a two-stage decrease trend, dropping slowly with the heating temperature up to $150^{\circ}C$ and then rapidly down to $0.869MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.812MN/m^{1.5}$ for 8-hour exposure time and $0.771MN/m^{1.5}$ for 16-hour exposure time. In general, the $K_{IC}$ values for the hot concrete up to $200^{\circ}C$ were larger than those for the cold concrete, and an inverse trend was observed thereafter. The increase in heating rate slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.893MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.839MN/m^{1.5}$ for $10^{\circ}C/min$ for the hot concrete and from $0.792MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.743MN/m^{1.5}$ for $10^{\circ}C/min$ for the cold concrete after an exposure time of 16 hours. The increase in cooling rate also slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.771MN/m^{1.5}$ for slow cooling to $0.739MN/m^{1.5}$ for fast cooling after an exposure time of 16 hours. The fracture energy-based fracture toughness $K_{IC}$' was also assessed, and similar decrease trends with the heating temperature and exposure time existed for both hot and cold concretes. The relationships of two fracture toughness parameters with the weight loss and the modulus of rapture were also evaluated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.770-776
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• 2009

The composites were fabricated by adding 0, 15, 30, 45[vol.%] $ZrB_2$ powders as a second phase to SiC matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by spark plasma sintering(SPS) were investigated. Reactions between ${\beta}$-SiC and $ZrB_2$ were not observed in the XRD and the phase analysis of the electroconductive SiC ceramic composites. The relative density of mono ${\beta}$-SiC, ${\beta}$-SiC+15[vol.%]$ZrB_2$, ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]$ZrB_2$ composites are respectively 99.24[%], 87.53[%], 96.41[%] and 98.11[%] Phase analysis of the electroconductive SiC ceramic composites by XRD revealed mostly of ${\beta}$-SiC, $ZrB_2$ and weakly of $ZrO_2$ phase. The flexural strength showed the lowest of 114.44[MPa] for ${\beta}$-SiC+15[vol.%]$ZrB_2$ powders and showed the highest of 210.75[MPa] for composite no added with $ZrB_2$ powders at room temperature. The trend of the mechanical properties of the electroconductive SiC ceramic composites is accorded with the trend of the relative density. The electrical resistivity of the electroconductive SiC ceramic composites decreased with increased $ZrB_2$ contents. The electrical resistivity of mono ${\beta}$-SiC, ${\beta}$-SiC+15[vol.%]$ZrB_2$, ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]$ZrB_2$ composites are respectively $4.57{\times}10^{-1},\;2.13{\times}10^{-1},\;2.68{\times}10^{-2}\;and\;1.99{\times}10^{-2}[{\Omega}{\cdot}cm]$ at room temperature. The electrical resistivity of mono ${\beta}$-SiC and ${\beta}$-SiC+15[vol.%]$ZrB_2$ are negative temperature coefficient resistance(NTCR) in temperature ranges from $25[^{\circ}C]\;to\; 100[^{\circ}C]$. The electrical resistivity of ${\beta}$-SiC+30[vol.%]$ZrB_2$ and ${\beta}$-SiC+45[vol.%]ZrB_2$ are positive temperature coefficient resistance(PTCR) in temperature ranges from $25[^{\circ}C]\;to\;100[^{\circ}C]$. It is convinced that ${\beta}$-SiC+30[vol.%]$ZrB_2$ composites by SPS for heater or ignitors can be applied.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.2
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• pp.71-79
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• 2014

Climate change has been social and environmental issues, it typically indicates the trend changes of not only temperature but also rainfall. There is a need to consider climate changes in a long-term soil erosion estimation since soil loss in a watershed can be varied by the changes of rainfall intensity and frequency of torrential rainfall. The impacts of rainfall trend changes on soil loss, one of climate changes, were estimated using Sediment Assessment Tool for Effective Erosion Control (SATEEC) employing L module with current climate scenario and future climate scenario collected from the Korea Meteorological Administration. A 62 $km^2$ watershed was selected to explore the climate changes on soil loss. SATEEC provided an increasing trend of soil loss with the climate change scenarios, which were 182 ton/ha/year in 2010s, 169 ton/ha/year in 2020s, 192 ton/ha/year in 2030s,182 ton/ha/year in 2040s, and 218 ton/ha/year in 2050s. Moreover, it was found that approximately 90% of agricultural area in the watershed displayed the soil loss of 50 ton/ha/year which is exceeding the allow able soil loss regulation by the Ministry of Environment.

• Atmosphere
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• v.21 no.2
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• pp.143-149
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• 2011

A new multi-timescale analysis method, Ensemble Empirical Mode Decomposition (EEMD), is used to diagnose the variation of the MJO activity determined by 850hPa and 200hPa zonal winds from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data for the 56-yr period from 1950 to 2005. The results show that MJO activity can be decomposed into 9 quasi-periodic oscillations and a trend. With each level of contribution of the quasi-periodic oscillation discussed, the bi-seasonal oscillation, the interannual oscillation and the trend of the MJO activity are the most prominent features. The trend increases almost linearly, so that prior to around 1978 the activity of the MJO is lower than that during the latter part. This may be related to the tropical sea surface temperature(SST). It is speculated that the interdecadal change in the MJO activity appeared in around 1978 is related to the warmer SST in the equatorial warm pool, especially over the Indian Ocean.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.870-878
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• 2003

The scale is removed from the strip by high pressure hydraulic descaling at the FSB (Finishing Scale Breaker). Recently, the spray height of nozzle has a trend to be shorter for the purpose of increasing the impact pressure by the high pressure water jet. Here, the nozzle intervals should be decided after considering the impact pressure and the temperature distribution on the strip. In other words, the minimum of impact pressure at the overlap of spray influences the surface grade of the strip due to scale and the overlap distance of the spray affects the temperature variation in the direction of the width of strip. In the present study, the impact pressure of the high pressure water jet is measured by the hydraulic descaling system and calculated with regard to the lead angle of 15$^{\circ}$ and the offset angle of 15$^{\circ}$, and then the temperature distribution and the temperature variation are calculated at the overlap distances of 0 mm, 10 mm, 20 mm, and 30 mm, respectively. The method of setting nozzle intervals is shown by utilizing these results.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.3
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• pp.73-80
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• 2009

In accordance with the trend for high-speed multi-axes, and the increasing technical sophistication of machine tools, thermal deformation has become an important factor in the accuracy of machine tools. It was analyzed that thermal deformation error accounts for about 70% of all errors made with machine tools. For precise temperature control, both cooling and heating should be implemented. A hot gas bypass type cooling cycle method has a simplified structure and temperature control accuracy to with in ${\pm}0.1^{\circ}C$. In this study, the performances of oil cooler system, including temperature controllability according to hot gas floe and preset temperature sustainability according to temperature load, were tested. It is expected that this study will contribute to the development and performances of oil cooler system, which could minimize thermal errors and improve the quality of precision machine tools.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.4
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• pp.274-278
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• 2001

Polymer membranes composed of N, N-dimethylaminoethyl methaccrylate(DMAEMA) and acrylamide(AAm)(or ethyl acrylamide(EAAm) were prepared to demonstrated the thermo-control of solute permeation. Poly DMEMA has a lower critical solution temperature(LCST) at around 50$\^{C}$ in water, With the copolymerization of DMAEMA with AAm (or EAAm) a shift in the LCST to a lowere temperature was observed, probably due to the formation of hydrogen bonds between the amide and N-N-dimethylamino groups. However, the temperature-induced phase transition of poly(DMAEMA-co-EAAm) did not show a similar trend to that of poly(DMAEMA- co-AAm) in the gel state. The hydrogen bonds in poly(DMAEMA-co-EAAm) were significantly disrupted with the formation a gel network, which led to a difference in the swilling behavior of polymer gels in response to temperature. To apply these polymers to temperature-sensitive sol-ute permeation, polymer membranes were prepared. The permeation pattern of hydrocortisone, used as the model solute, was explained based on the temperature-sensitive swelling behavior of the polymer membranes.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.48-55
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• 2013

In this paper, W-DCAP-HTR(Web-based Design Compatibility Assessment Program for High Temperature Reactor) which will be used to check the design criteria for high temperature reactor is newly proposed. To do this, the assessment procedure of the ASME Sec.III Div.5 such as time-dependent primary stress limit, accumulated inelastic strain, and creep-fatigue damage evaluation were investigated. Furthermore, the trend of candidate materials for high temperature reactor was also reviewed. Then, all assessment procedures for high temperature reactor have been computerized to enhance the efficiency and to reduce the possibility of human error during calculating procedure by hand calculation. It can be directly conducted by adopting the actual thermal and structural analysis results. The validation of W-DCAP-HTR has been demonstrated by benchmark analysis.