• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2524-2527
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• 2007

Solid propellant gas generators (SPGG) play a role as a turbopump starter in liquid propellant propulsion systems by supplying pressurized gas to power turbines for engine start. For such a purpose, the propellants should burn with a relative low flame temperature and the combustion gas should not contain corrosive constituents such as chlorine compounds. In accordance with these requirements, stabilized AN-based propellants have been usually used as the most appropriate oxidizer for propellant compositions. However, the burning area of the propellant intends to increase to satisfy the required mass flux because of its low burning rate. Consequently the burning area incensement brings on the SPGG size augmentation. A flow restriction such as filters is applied to decrease the SPGG size by rising up the combustion pressure resulting in increasing the burning rate. The feasibility of the size reduction of SPGG by the employment of filters have been studied. The preliminary results of this study show that the considerable reduction of SPGG size would be achievable just by installing a filter with relatively high pressure loss coefficient.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.1-6
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• 2008

The burning characteristics of HTPB/AP solid propellants were measured by closed bomb of internal volume of 200 cc and 700 cc up to 30,000 psia. The burning rates of closed bomb method showed good agreement with those of strand burner method between 1,000 psia and 5,000 psia, and the sharp increment of pressure exponent(n) around 6,000 psia as a result of testing in accordance with loading densities. The burning rate measured in 200 cc and 700 cc of internal volume of closed bomb agreed well without the relation of internal volume size.

• Journal of Korean Elementary Science Education
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• v.18 no.2
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• pp.145-151
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• 1999

There is an experiment in the elementary science textbook which a burning candle hold upright in a water tank and a beaker is converted over the burning candle, the candle flame goes out and the water rises into the beaker. Some reference books including teachers' guide for the elementary school teachers explain the reason why water rises that oxygen is "used up", so water rises the same volume of consumed oxygen into the beaker. But this explanation is only partially correct. In this study, discrepancies of the explanation that oxygen is "used up" are analyzed. Water rises by two major reasons. One is that water can rise to the level about l/3 of the volume of consumed oxygen. The other is that the beaker is converted over the burning candle which produces hot CO2 and water vapor, and the candle's flame heats the air around it to expand, after the candle flame goes out, the air in the beaker cools and water vapor changes to liquid water, so, air pressure in the beaker is reduced, and the water is pushed into the beaker by great air pressure outside. 1 demonstrate a inquiry teaching method of the candle experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.124-127
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• 2003

Sewage sludge and clay used as raw materials in the study. Green aggregates contain different contents by dried weight of the sewage sludge, up to 80 percent is manufactured and burning conditions of soak temperature, soak time and rate of temperature increase. influence of burning condition and mixing ratio on specific gravity of burned aggregate are discussed. The appropriate burning condition to all aggregates is evaluated. Aggregates result form the thermal treatment get specific gravity under 0.8, water absorption fewer than 7.5 percent, and aggregate crushing value from 28 to 53. As the result, aggregates can be available as the lightweight aggregate for non-structural concrete.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.3
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• pp.12-17
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• 2020

The mechanical properties of the propellant with yellow iron oxide were slightly increased compared to the propellant with red iron oxide. The propellant with yellow iron oxide used two types of AP. As the ratio of small particles of AP increased, the burning rate increased. The propellant may be applied to the propellant under operating conditions of 17.5 mm/sec or less having a pressure index of 0.5. The burning rate downs in the mixer scale-up. The stress at maximum load of propellant decreased and the strain at maximum load increased in the mixer scale-up. The yellow iron oxide did not affect the adhesive force between the insulation/liner/propellant.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.25-32
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• 2000

Fire-resistant boom is one of the most important facilities in in situ homing of spilled oil. Thermal response of a fire-resistant boom to turning is experimentally investigated in this paper by using an electric furnace and a burning test facility. This test facility is composed of a test tank, a fire boom, a hood for inhaling smoke, an incinerator for burning up gases and thermocouples, etc. Thereby a systematic method of approach in small laboratory scale is developed to study the performance of a fire-resistant boom. Burning test is carried out for the fire boom model which has been developed through the present study. It is shown that the present fire boom model has capability to withstand the high temperature around 800℃ and high rate of heat flux on it due to homing. For more realistic experimental environments, larger dimensions in devices and longer time in experiments are recommended in near future.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.76-79
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• 2008

In this work wood crib burning behaviors have been simulated by using the FDS(Fire Dynamic Simulator) program. Wood cribs are regularly stacked arrays of wood sticks, and available for the performance rating of fire-extinguishers. On the basis of an angle iron supporter 26 layers of wood sticks have been stacked up. Each layer consists of 5 or 6 wood sticks which are placed in parallel, with a constant distance, and in alternating rows. They are laid between the horizontally adjacent sticks at the before last layer. The wood crib is ignited instantaneously by an amount of burning gasoline below. A comprehensive simulation of such a practical sophisticated combustion is still too difficult to realize with any currently available computer, although the performance of modern processors is getting better everyday. We could carry it out here through parallel computing on the HPC(High Performance Computing) cluster as the feasible alternative. At last the validation has been executed by means of temperature distribution data measured by the thermal video camera.

• Journal of Oral Medicine and Pain
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• v.41 no.4
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• pp.188-194
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• 2016

Purpose: Burning mouth syndrome (BMS) is ambiguous and enigmatic oral condition. Sleep disturbance is one of the most prevalent complaints of patients with chronic pain. The aim of this study was to estimate general sleep characteristics and propensity in patients with BMS. Methods: A total of thirty BMS patients and thirty healthy control subjects were investigated. Self-reported measures of sleep quality were conducted using two widely used methods; the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). Data were analyzed with one-way ANOVA, chi-square, Fisher's exact test, Kruskal-Wallis test, Holm method with 95% confidence interval and p<0.05 significant level. Results: BMS patients showed more poor sleepers than those in control subjects in both ESS and PSQI test. BMS patients also showed statistically significant poorer sleep quality compared with control subjects in both test. When BMS group were divided into three groups on the basis of numeric rating scale, the higher score subjects had, the more mean rank they had in the PSQI. Conclusions: BMS patients showed up poor sleep characteristics and propensity than control group, and they also showed the more severe the pain was, the worse the sleep quality was.

• Journal of the military operations research society of Korea
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• v.3 no.1
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• pp.83-96
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• 1977

The combustion chamber and nozzle of an end burning, small spherical rocket is designed. A spherical external shape has a number of advantages such as fixed center-of-gravity and minimum aerodynamic precession torques during flight and a better mass distribution for gyro-stabilization as contrasted to a conventional ogive rocket shape. It is shown that the cross-sectional variation of the end burning solid propellant with length is an exponential geometry to provide a constant thrust-weight ratio of the rocket device during the propellant burning period, and that the factors which affect the attainment of the constant relationship of thrust to weight in the design are the initial propellant area, initial weight of the rocket and propellant density. The measurement of the transient thrust in the ground static test using black powder propellant supports the predicted results. A wind tunnel having a $30{\times}30{\times}75cm$ test section and Mach number 0.11 is constructed, and a simple balance-type device is designed for the measurement of the drag of a spinning sphere. The experimental results indicate that the. spinning has no effect on the magnitude of the drag up to the Reynolds number $3{\times}10^5$. Numerical computation of the flight trajectories for various launching angles is presented, and the gyro-stabilization of spinning sphere is discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1172-1177
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• 2004

The emission control of automobile 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 combustion characteristics of propane mixture. The combustion characteristics was analyzed, with the change of supply conditions of propane fuel. Inside the combustion chamber, the maximum temperature increase with the initial pressure is going up. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux do not change much according to the theoretical correct mixture but it changes with the various initial temperature of the combustion chamber.