• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.61-68
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• 2002

Combustion characteristics of dual transverse injection of hydrogen in supersonic air flows were studied using computational methods. Three-dimensional Navier-Stokes with a non-equilibrium chemical reaction model and the k-$\omega$ SST turbulence model were used. A parametric study was conducted with the variation of the distance between two injectors. Combustion characteristics of dual injection are very different from those of single injection. The combustion characteristics of two injection flows are very different from each other, and the ignition and combustion characteristics of the rear injection flow are strongly influenced by those of the front injection flow. The increase of the distance between two injectors up to a specific distance results in the increase of burning rate. However, the increase of the distance over the specific distance gives no increase of burning rate but makes more losses of stagnation pressure. From the results it can be stated that there exists a distance between two injectors for optimum combustion characteristics.

• Journal of Oral Medicine and Pain
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• v.44 no.1
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• pp.25-30
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• 2019

Purpose: The exact causes of burning mouth syndrome (BMS) is unclear so far. There are many studies to elucidate the relation between oral disease and genetic predisposition. In this study, we first tried to investigate salivary exosomal genetic components that could play an important role for diagnosing and elucidating the progression of BMS. Methods: We compared salivary exosomal micro RNAs (miRNAs) of BMS Patients to those of control using next generation sequencing (NGS). Unstimulated whole saliva from 15 patients with BMS and 10 control subjects were divided into two sets. Isolated exosomes and their total RNAs were subject to NGS for the screening of miRNAs. Results: There were up-regulated 10 exosomal miRNAs (hsa-miR-1273h-5p, hsa-miR-1273a, hsa-miR-1304-3p, hsa-miR-4449, hsa-miR-1285-3p, hsa-miR-6802-5p, hsa-miR-1268a, hsa-miR-1273d, hsa-miR-1273f, and hsa-miR-423-5p) and down-regulated 18 exosomal miRNAs (hsa-miR-27b-3p, hsa-miR-16-5p, hsa-miR-186-5p, hsa-miR-142-3p, hsa-miR-141-3p, hsa-miR-150-5p, hsa-miR-374a-5p, hsa-miR-93-5p, hsa-miR-29c-3p, hsa-miR-29a-3p, hsa-miR-148a-3p, hsa-miR-22-3p, hsa-miR-27a-3p, hsa-miR-424-5p, hsa-miR-19b-3p, hsa-miR-99a-5p, hsa-miR-548d-3p, and hsa-miR-19a-3p) in BMS patients comparing with those of control subjects. Conclusions: We show that there are 28 differential expression of miRNAs between the patients with BMS and those of control subjects. The specific function of indicated miRNAs should be further elucidated.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.45-53
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• 2004

An experimental study was carried out to obtain the fundamental data about the effects of radicals induced injection on premixture combustion. A constant volume combustor divided to the sub-chamber and the main chamber was used. The volume of the sub-chamber is set up to occupy less than 1.5％ of that of whole combustion chamber. Radial twelve narrow passage holes are arranged between the main chamber and the sub-chamber. The products including radicals generated by spark ignition in the sub-chamber will derive the simultaneous multi-point ignition in the main chamber. While the equivalence ratio of pre-mixture in the main chamber and the sub-chamber is uniform. We have examined the effects of the sub-chamber volume, the diameter of passage hole, and the equivalence ratio on the combustion characteristics by means of burning pressure measurement and flame visualization. In the case of radical ignition method(RI), the overall turning time including the ignition delay became very short and the maximum burning pressure was slightly increased in comparison with those of the conventional spark ignition method(SI), that is, single chamber combustion without the sub-chamber. The combustible lean limit by RI method is extended to more ER=0.25 than that by SI method. Therefore the decrease of every emission including NOx and the improvement of fuel consumption is anticipated due to lean burn.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.4
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• pp.319-326
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• 2014

Exhaust gas emitted as a result of the incomplete combustion of biomass in charcoal kilns includes odor compounds as well as other air pollutants such as particulate matters, sulfur and nitrogen oxides, and carbon monoxide. A number of offensive odor compounds affect quality of life. In this study, odor emissions were investigated from biomass burning in a pilot-scale charcoal kiln and a commercial-scale kiln. Complex odor from emission source reached up to 10,000 dilutions to threshold during the study period. Combustion fume was found to contain reduced sulfur compounds, aldehydes, and volatile organic compounds. Hydrogen sulfide and methyl mercaptan were the major odorants which highly contributed to the offensive odor.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.125-132
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• 2004

The radial slot configuration in the solid propellant grain is usually fabricated by the polyurethane foam slot former The foam cannot be easily removed from the solid propellant, some can remain in the slot. Analogue solid propellant rocket motors using polyurethane foam to shape the slot are static fired with the foam former still in place in the slot. The pressure increases at the slot part are measured and there are indications of the propellant cracks at the insulations above the slot. The pressure increase is produced at the beginning of the burning sequence as the foam will hinder the combustion gas of the burning propellant from flowing into the central bore. The pressure increase up to about 300psi is predicted for the motor tested and this pressure increase depends on the gap between the propellant and foam surfaces and remaining foam volume. This amount of pressure increase inside of the slot is estimated to cause the propellant crack. To prevent this pressure increase, minimizing the foam remainder in the slot and making sufficient chamfering at the comer of the slot entrance are suggested.

• Archives of Plastic Surgery
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• v.33 no.5
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• pp.648-651
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• 2006

Purpose: Tarsal tunnel syndrome is characterized by pain and paresthesia of the entire posterior tibial nerve and its branches of the lower extremity. The cause of the tarsal tunnel syndrome is usually unknown but, rare case of space occupying benign tumors such as a ganglion may be one of the causes. We report our experiences of surgical treatment of the tarsal tunnel syndrome caused by ganglion we have encountered recently. Methods: A 54-year-old male patient presented with paresthesia, burning pain, positive Tinnel's sign without preceeding trauma, infection or any other causes of event. With surgical intervention, we completely removed the space occupying ganglion and with performed surgical release of the posterior tibial nerve and its branches. Results: At a 14-month follow up examination, the symptoms of paresthesia, burning pain, sensory disturbance was much improved compared to the preoperative conditions. Takakura's rating scale was elevated from 4(Poor) to 8(Good). Conclusion: We report our surgical experience of a rare case of tarsal tunnel syndrome caused by a ganglion, with a review of literature.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.75-82
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• 2004

The allowable exhaust standard has been intensified as a part of the countermeasure to decrease air pollution in the world. As the cars with an alternative fuel starts to get into the spotlight, the cars with low emission has been introduced and exhaust gas regulation forced in this country. These days, LPG vehicles, which infrastructure of fuel was already built up, and CNG vehicles are recognized for alternative fuel cars in this country. In this study, the constant volume combustion chamber was manufactured and used for experiments to obtain the ignition characteristics of LPG fuel and the optimal ignition energy. The experiment measured the combustion characteristics, in regard to the change of combustion variable, and the change of ignition energy. During the combustion of fuel, the maximum temperature inside the combustion chamber is higher when the initial pressure is higher. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux did not change much with the theoretical correct mixture but the various initial temperature of the combustion chamber. The heat flux got faster and ignition energy bigger as the dwell time of the ignition system expanded. When the dwell time get longer, the ignition energy also increased then fixed. The ignition energy increased as the initial pressure inside the combustion chamber higher. The heat flux got faster as the dwell time expanded.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.7-10
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• 2009

The development and evaluation of solid propellant were performed for the turbopump pyro starter, which start up the liquid propellant rocket engine for the Space Launch Vehicle (SLV). Requirements for the turbopump pyro starter propellant include the production of low flame temperature, low burning rate and nontoxic gas to protect the mechanical corrosion or air pollution. This study describes the development of the solid propellant composition which is based on PCP binder. DHG (Dihydroxy glyoxime), which has advantages of oxygen balance and ignition, was used as coolant. The mechanical properties and burning rate of the propellants were measured. Finally, static fired test was performed to prove the possibility of development.

• Fire Science and Engineering
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• v.12 no.4
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• pp.51-57
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• 1998

The thermal behavior and the flammability characteristics of four different unsaturated polyester resins were studied by performing a series of thermal analysis experiments and laboratory scale fire tests. The results of TGA and DSC reveals that the vinylester type resins have superior thermal performances when compared to the isophthalic type resins. The vinylester type resins formed a network shaped char surface after the thermal decomposition up to 55$0^{\circ}C$. Consequently, the vinylester type resings have shown lower value of burning rate than that of iso type resins. Due to the high level of flammability and toxic smoke emission, the appropriate flame retardant system should be applied to the unsaturated polyester resings.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.112-120
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• 2005

The solid propellants have been most widely used for the military rockets or missiles all over the world and the efforts have been focused on the enhancement of propellant performance up to 1980s. lately in company with the distinguished development in the intelligence and communication technology, the more accurate guidance as well as maneuverability has been required in the military weapon system. To meet the requirements such as a high maneuverability, insensitiveness, or stealth of missile, the researches have been doing to develop the solid propellants which have a quality of ultra-fast burning rate, insensitiveness, low signature or the like.