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Kunsan, South Korea

Kunsan National University is a national university located in Gunsan, Jeollabuk-do, in western South Korea. The university first opened its doors in 1947 as Kunsan Teachers' College. It gained university status in 1991. Wikipedia.


Park M.-I.,Kunsan National University
Classical and Quantum Gravity | Year: 2011

Recently Hořava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. But there have been confusions regarding an extra scalar graviton mode and the consistency of the Hořava model. I reconsider these problems and show that, in the Minkowski vacuum background, the scalar graviton mode can be the consistency decoupled from the usual tensor graviton modes, by imposing the (local) Hamiltonian as well as the momentum constraints. © 2011 IOP Publishing Ltd Printed in the UK & the USA. Source


Lee C.O.,Kunsan National University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We investigate the extended thermodynamic properties of higher-dimensional Taub-NUT/Bolt-AdS spaces where a cosmological constant is treated as a pressure. We find a general form for thermodynamic volumes of Taub-NUT/Bolt-AdS black holes for arbitrary dimensions. Interestingly, it is found that the Taub-NUT-AdS metric has a thermodynamically stable range when the total number of dimensions is a multiple of 4 (4, 8, 12,...). We also explore their phase structure and find the first order phase transition holds for higher-dimensional cases. © 2014 The Author. Source


Combustion and emissions characteristics of a compression ignition engine with a dual fuel (biodiesel-CNG) combustion system were investigated in this study. This experiment utilized a biodiesel pilot injection to ignite a main charge of compressed natural gas (CNG). The pilot injection pressure was maintained at approximately 120MPa while the pilot injection timing was varied across the range 11-23 crank angle degrees (CAD) before top-dead-center (BTDC) to investigate the characteristics of engine performance and exhaust emissions in a single cylinder diesel engine. Results show that performance can be optimized for biodiesel-CNG dual fuel combustion (DFC) by advancing the pilot injection timing for low loads and delaying the injection timing for high loads. However, overall performance of diesel single fuel combustion (SFC) still exceeds that of biodiesel-CNG DFC. Slight cycle-to-cycle variations are observed when dual fuel is used, but remains less than 1.3% at all conditions. The combustion of biodiesel-CNG begins at a later CAD compared to that of diesel SFC due to the increase of ignition delay of the pilot fuel. The ignition delay in DFC is 1.6-4.4 CAD longer than that of the diesel SFC. Ignition delays are reduced with the increased engine load. BSEC of biodiesel-CNG DFC improves with advanced pilot injection timing at low load and with delayed pilot injection timing at full load. Smoke is decreased and NOx is increased with advanced pilot injection timing in the biodiesel-CNG DFC. Compared to the diesel SFC, however, smoke emissions are significantly reduced over the range of operating conditions and NOx emissions are also reduced except for the full load condition. DFC yields lower CO2 emissions compared to diesel SFC over all engine conditions. Biodiesel-CNG DFC results in relative high CO and HC emissions at low load conditions due to the low combustion temperature of CNG but no notable trend of HC emissions with variations of pilot injection timing were discovered. © 2013 Elsevier Ltd. Source


Biodiesel-compressed natural gas (CNG) dual fuel combustion (DFC) system is studied for the simultaneous reduction of particulate matters (PM) and nitrogen oxides (NOx) from diesel engine. In this study, biodiesel is used as a pilot injection fuel to ignite the main fuel, CNG of DFC system. In particular, the pilot injection pressure is controlled to investigate the characteristics of engine performance and exhaust emissions in a single cylinder diesel engine. The results show that the indicated mean effective pressure (IMEP) of biodiesel-CNG DFC mode is lower than that of diesel single fuel combustion (SFC) mode at higher injection pressure. However, the combustion stability of biodiesel-CNG DFC mode is increased with the increase of pilot injection pressure. At the same injection pressure, the start of combustion of biodiesel-CNG DFC is delayed compared to diesel SFC due to the increase of ignition delay of pilot fuel. On the contrary, it is observed that as the pilot injection pressure increase, the combustion process begins and ends a little earlier for biodiesel-CNG DFC. The ignition delay in the DFC is about 1.2-2.6 CA longer compared to diesel SFC, but decreases with increases of pilot injection pressure. Smoke and NOx emissions are decreased and increased, respectively, as the pilot injection pressure increases in the biodiesel-CNG DFC. In comparison to diesel SFC, smoke emissions are significantly reduced over all the operating conditions and NOx emissions also exhibited similar reduction trend except for the full load condition in biodiesel-CNG DFC. DFC yields higher CO emissions compared to diesel SFC over all engine conditions except for 100% load. The more unburned hydrocarbon emissions are exhausted in the DFC mode than in the diesel SFC; however, this decreases with increases in pilot injection pressure. © 2013 Elsevier Ltd. All rights reserved. Source


Lee C.O.,Kunsan National University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

We consider higher dimensional topological Taub-NUT/Bolt-AdS solutions where a cosmological constant is treated as a pressure. The thermodynamic quantities of these solutions are explicitly calculated. Furthermore, we find these thermodynamic quantities satisfying the Clapeyron equation. In particular, a new thermodynamically stable region for the NUT solution is found by studying the Gibbs free energy. Intriguingly, we also find that like the AdS black hole case, the G- T diagram of the Bolt solution has two branches which are joined at a minimum temperature. The Bolt solution with the large radius, at the lower branch, becomes stable beyond a certain temperature while the Bolt solution with the small radius, at the upper branch, is always unstable. © 2015 The Author. Source

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