• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.368-373
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• 2017

Control method for DACS with variable burning area is designed and the performance of the control method is analyzed by doing simulation at various conditions. DACS, which got solid propellant on board, is designed as end-burning type typically. End-burning type DACS has the merit of controlling pressure and thrust, but it discharges the combustion gas which does not using for getting thrust. Therefore, optimal design of propellant grain and burning area changes over time as a result. Variable burning area can be assumed as a disturbance and adaptive control method is useful for pressure control of DACS effected by disturbance.

• Korean Journal of Environment and Ecology
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• v.23 no.4
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• pp.317-325
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• 2009

This study was presented to effect of prescribed burning to the avian fauna and was conducted from March to October 2007 in Sihwa grassland, Gyeonggi-do, Korea. Prescribed burning was conducted at Sihwa grassland of Songjeong-ri Mado-myeon, Hwaseong city from 28th February to 1 st March 2007. Thirty birds species were observed and sum of the maximum count was 181 individuals at the prescribed burning area for all survey time. Observed species was 24 species and sum of the maximum count was 154 individuals on the unburned area. Number of species and sum of the maximum count at the prescribed burning area was greater than unburned area. There is no differences in the dominant species between prescribed and unburned area. Average number of species, number of individuals, species diversity and species richness of the prescribed burning area were greater than unburned area in early stage (from March to June) after prescribed burning. Community indices in burned area during early season were different with unburned area by prediscribed burning. However, the indices had became similar between burned and unburned area as time goes by. Disturbance by prescribed burning created new habitat and feeding site temporarily for the avian species in grassland. We would suggest that prescribed burning is most effective method to maintain grassland ecosystem from the invading bush or tree and periodical prescribed burning is a good method to preserve and manage the grassland ecosystem.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.225-233
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• 2007

The engineering properties of surface soils in natural terrain are changed due to wildfire. This change of engineering properties induced by wildfire is related to landslides occurrence. To investigate the change of soil properties caused by wildfire, the various soil tests are performed. The soil samples are obtained from the recently burned slopes of Yangyang area, Kangwon Province. The soil samples obtained from the burned slopes are classified into three types depending on the burning grade: the perfect burning grade, the intermediate burning grade, the non-burning grade. As the result of tests, the specific gravity and the dry unit weight of soils obtained from perfect and alternative burning grades are less than those of soils obtained from non-burning grade. It judges that an electronic force, ionic components and of soils are changed and organic matters in soils are burned by wildfire. The permeability of soil obtained from alternative burning grade is the lowest and that of soil obtained from perfect burning grade is the highest. The water-repellent layer is formed on soil surface by wildfire. The water-repellent layer is existed at the area of alternative turning grade, while the layer is not existed at the area of perfect burning grade. The water-repellent layer is collapsed in high temperature more than about $400^{\circ}C$.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1338-1348
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• 2004

A simplified method that models the deflagration process occurring in closed or vented vessels is described. When combustion occurs within the spherical or cylindrical vessels, the flame moves spherically or segmentally to the vessel periphery. The volume and area of each element along the propagating flame front are calculated by using simple geometrical rules. For instabilities and turbulence resulting in enhanced burning rates, a simple analysis results in reasonable agreement with the experimental pressure transients when two burning rates (a laminar burning rate prior to the onset of instability and an enhanced burning rate) were used. Pressure reduction caused by a vent opening at predetermined pressure was modeled. Parameters examined in the modeling include ignition location, mixture concentration, vented area, and vent opening pressure. It was found that venting was effective in reducing the peak pressure experienced in vessels. The model can be expected to estimate reasonable peak pressures and flame front distances by modeling the enhanced burning rates, that is, turbulent enhancement factor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1115-1121
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• 2017

In order to obtain high thrust at the beginning of the flight, the solid rocket motor with large initial burning surface area was designed and tested. From the static firing test, lower initial thrust was obtained compared with the expected thrust based on the internal ballistic prediction due to the negative erosive burning effect which reduced the burning rate estimated by APN Law. In addition, the radial mode combustion instability was observed with 8 fins grain configuration. This instability was removed after the odd number of fins were used.

• Journal of the Korean Wood Science and Technology
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• v.14 no.4
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• pp.21-28
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• 1986

Plywood used for construction as a decorative inner material is inflammable and can fire accident, causing destruction of human life and property. In this study, 3.5mm Kapur plywoods were soaked in the 23% monoammonium phosphate solutions by cold soaking method 3, 6, 9hrs and hot-cold bath method for 3/3hrs, and redrying was carried out by press-drying at the platen temperature of 110, 130, 160, 180$^{\circ}C$, and then fire test was carried out to investigate burning point, flame exhausted length, frame spread length, back side carbonized area and weight loss. The results are as follows; 1. In cold soaking method for 3, 6, 9hrs. retentions of monoammonium phosphate were 0.377, 0.448, 0.498kg/(30cm)$^3$ respectively, and in hot-cold bath method for 3/3hrs, the retention was 1.331kg(30cm)$^3$ that exceeded the minimum retention 1.124kg/(30cm)$^3$. 2. Correlation coefficients among the variable were shown in table 2. From the table, it could be recognized that there were close negative correlations between the treatment and burning point, flame spread length, back side carbonized area, flame exhausted time and weight loss, and there was negative correlation between treating time and back side carbonized area, but there was positive correlation between platen temperature and burning point. 3. From table 3, it can be observed that there were highly significant differences for burning point, flame spread length, flame exhausted time, back side carhonized area, weight loss between treatments. And in 2-way interactions, there were also highly significant for burning point, flame spread length, flame exhausted time, weight loss between time x treatment. 4. It was observed that burning point, flame exhausted time, flame spread length, back side carbonized area, and weight loss in fire-retardant treated plywood were the best effects in fire-retardant treated plywood, water treated plywood and nontreated plywood. In conclusion, I can estimate that absorbed chemical contents by hot-cold bath method for 3/3hrs, have a lot of effects on fire-retardant factors such as burning point, flame spread length, flame exhausted time, backside carbonized area and weight loss, but platen temperatures have a little effects on the fire factors.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.56-61
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• 2014

Two erosive burning models were applied to compare analysis results of ballistic for the internal ballistics of solid rocket motors. By comparing motor tests with results of analysis, the variance of a grain shape was analyzed and coefficients of erosive burning were drawn. Results of comparison presents that the coefficient of erosive burning was proportional to the change of burning area, while inversely proportional to the change of cross area.

• Journal of Oral Medicine and Pain
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• v.26 no.2
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• pp.161-171
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• 2001

In order to determine how oral mucosal change relates to inducing factors of burning mouth syndrome, the difference in pain perception scale and keratinization rate between burning mouth syndrome patients and normal subjects were investigated. Twenty patients (13 female, 7 male, mean age: 59 years), presenting in the Department of Oral Medicine, Chonnam National University Hospital were participated in this study. All subjects had been complaining of constant oral burning pain for more than a year, none took any strong analgesics, and none had oral mucosal lesions. Twenty volunteers (11 females, 9 males, mean age: 25 years) were also participated in this study as a control group. The control subjects had never had any symptoms of oral burning pain. A thermal stimulation using a Nd-YAG laser and cytological smear were carried out to anterodorsal part of tongue, tip of tongue, the left buccal mucosa, the lower lip mucosa and the chief complaint site. Stimulation of the dorsum of left hand was also carried out to contrast the mucosal area of burning mouth syndrome subjects and the control subjects. The laser output power could be adjusted from 0.75W to 4W. The pain perception scale of the burning mouth syndrome subjects were lower than in control subjects in the chief complaint area, the anterodorsal part of tongue and the buccal mucosa(p<0.01). The keratinization rate of burning mouth syndrome subjects, however, was higher keratinization rate than in normal subjects in the same area and lower lip mucosa(p<0.001). From above results, the anterodorsal part of tongue is the most appropriate site to use diagnostic laser stimulation. The higher level of keratinization and the lower level of thermal pain perception of the burning mouth syndrome subjects are explained as a protective mechanism against xerostomia and burning sensations. The application of Nd-YAG laser stimuli and cytological smear to oral mucosal surface could therefore be usefully employed as appropriate and standardized diagnostic tools for chronic orofacial pain subjects.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.4
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• pp.285-296
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• 1997

The suspended particulate matters had been collected on quartz fiber fiters by a cascade impactor having 9 size stages for 4 years (Sep. 1991 to Dec. 1995) in Kyung Hee University-Suwon Campus. Membrane filters were used to collected the particulate matters on each stage. The weight concentration on each stage was obtained by a microbalance and further chemical element levels were determined by an x-ray fluorescence system. Based on these chemical information, our study focused on applying the target transformation factor analysis (TTFA), a receptor model, to identify aerosol sources and to apportion quantitatively their mass contribution. There are total of 63 ambient data sets. Each data set consists of the 8 size-ranged subdata sets characterized by 16 elemental variables. By the results, four to five sources were extracted from each size range and some sources reappeared in other size ranges. Then total of 8 source profiles were statistically generated from all the ranges, such as oil burning source, soil source, field burning source, gasoline related source, coal burning source, marine source, glass related source, and unknown sources. Apportioning aerosol mass to each source was intensively examined by investigating emission inventories near the study area. The results showed that soil particle source was the most significant contributor. However, coal and oil burning sources were the major anthropogenic ones. The study finally proposed some air quality control strategies to achieve the clean air quality in Suwon area.

• 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.