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.
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.
Lee S.C.,Kunsan National University
Separation and Purification Technology | Year: 2013
An attempt to separate acetic acid from xylose and sulfuric acid in a simulated hemicellulosic hydrolysate by emulsion liquid membranes (ELMs) was made in a batch reactor for the first time. This is the first step to realize the ultimate goal of xylose purification by removal of acetic acid from the hydrolysate and by subsequent removal of sulfuric acid. In order to develop the ELM system for selective removal of acetic acid, the effects of various experimental variables on extraction of acetic acid, xylose and sulfuric acid were investigated. Under a specific operating condition, the apparent degree of extraction of acetic acid was higher than 99% in the ELM system while those of xylose and sulfuric acid were below zero. Also, the enrichment ratio of acetic acid was 5.45 while those of xylose and sulfuric acid were below 0.15. These results demonstrated the superiority of the current ELM work. © 2013 Published by Elsevier B.V.
Sahoo P.K.,Kunsan National University
Reviews of environmental contamination and toxicology | Year: 2013
AMD is one of the critical environmental problems that causes acidification and metal contamination of surface and ground water bodies when mine materials and/or over burden-containing metal sulfides are exposed to oxidizing conditions. The best option to limit AMD is early avoidance of sulfide oxidation. Several techniques are available to achieve this. In this paper, we review all of the major methods now used to limit sulfide oxidation. These fall into five categories: (1) physical barriers,(2) bacterial inhibition, (3) chemical passivation, ( 4) electrochemical, and (5) desulfurization.We describe the processes underlying each method by category and then address aspects relating to effectiveness, cost, and environmental impact. This paper may help organisms.Encapsulation or passivation of sulfide surfaces (applying organic and/or inorganic coatings) is simple and effective in preventing AMD. Among inorganic coatings,silica is the most promising, stable, minerals into a low-volume stream, leaving mainly waste with low sulfur content that will be non-acid-generating. The attractiveness of desulfurization is that it is simple and economic.Our review has clearly disclosed that more information is needed for most of the AMD-mitigation techniques available. Silica passivation has shown promise, butmore extensive field-testing is needed to reduce it to commercial viability. Silica is the dominant element in fly ash, and therefore, its use as a low-cost, easily accessible coating should be evaluated. Permanganate passivation also requires further study to understand the role of pH. The secondary formation of Fe-oxyhydroxide minerals from Fe-oxyhydroxides, from the standpoint of their phase transformation,stability and effectiveness, should be assessed over longer experimental periods. All inorganic coatings are designed to inhibit abiotic oxidation of pyrite; however, their effect on biotic pyrite oxidation is not well known and should be further studied.Currently, there is no information available on longer-term field application of organic reagents. Such information is needed to evaluate their lifetime environmental and performance effects. Future studies require spectroscopic analyses of all coating types to achieve a better understanding of their surface chemistry. In addition,a thorough mineralogical and geochemical characterization of waste materialsis applications, or at specific sites. Combining techniques can help ac~Ie:eAMD containment in some cases. For example, applying dry cover (e.g., sml) mcombination with liming material or a bactericide, or applying inorganic coatings(e.g., silica) along with organic reagents (e.g., lipids or humic acid) may be moreeffective than utilizing any single technique alone.
Ryu K.,Kunsan National University
Applied Energy | Year: 2013
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.