• Fire Science and Engineering
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• v.18 no.2
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• pp.20-26
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• 2004

The purpose of this study is to investigate the transition mechanism and prevention mechanism of gas explosion to fire. Transition phenomena of explosion to fire of LPG in the explosion vessel of its size of TEX>$100 cm {\times} 60 cm {\times} 45 cm$ was visualized using the high speed video camera and the mechanism was analysed from the videograph. Newspaper size of $30cm {\times} 20cm$ was used for combustible sample in this experiments and LPG-air mixture was ignited by 10 ㎸ electric spark. Experimental parameter was gas concentration, size of vent area and position of combustible solid. Size of vent area were varied as $10cm {\times} 9cm, 13cm {\times} 10cm, 27cm {\times} 20cm, 40cm {\times} 27cm$, and the position of combustible was varied in 4 point. Carbon dioxide was used to study the prevention mechanism of explosion to fire transition of LPG. Based on this experiment we can find that transition possibility of explosion to fire on solid combustible from explosion is depends on concentration of LPG-air mixture and the exposure time of solid combustibles in high temperature atmosphere of flame and burnt gas. And cooling or inerting of the atmosphere after explosion can be prevent the transition of explosion to fire on solid combustibles from gas explosion.

• Journal of Food Hygiene and Safety
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• v.33 no.6
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• pp.483-487
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• 2018

The objective of this study was to examine the natural origin of propionic acid in rice cakes by investigating the growth characteristics of the microflora and their production of propionic acid in the Joraengyi rice cake during storage period. The experiment was done in two stages within a period of three month: the rice cake fresh and contaminated with cocktail propionibacterium. The propionic acid production was analyzed according to the storage time and temperature by GC-FID (Gas chromatograph with flame ionization detector). During the storage of the fresh Joraengyi rice cake without alcohol at $30^{\circ}C$, about 95 mg/L of propionic acid was detected in 1st week, 330 mg/L in 4th week, 850 mg/L in 6th week, 970 mg/L in 8th week, and 1,040 mg/L in 12th week. During the storage of the Joraengyi rice cake which was contaminated with cocktail propionibacterium at $30^{\circ}C$, about 100 mg/L was detected from the rice cake with alcohol in the 1st week, 270 mg/L in 2nd week, about 470 mg/L in 4th week, and 660 mg/L in 8th week. This study demonstratesd the natural production of propionic acid during storage of the Joraengyi rice cake. To prevent the production, it is necessary to thoroughly manage hygiene and store it at refrigerated temperature or below $20^{\circ}C$.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.53-53
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• 2019

Cypripediums, popularly called lady's slippers or moccasin flowers, are the showiest and most sought after hardy terrestrial orchids, collected and grown by orchid and alpine plant enthusiasts alike. In Korea, 4 species of cypripedium are reported as Cypripedium japonicum, C. macranthos, C. guttatum, and C. calceolus. We had already reported the feasibilities of C. macranthos and C. guttatum with in vitro germination methods from immature seeds. The seeds of white lady's slipper orchid (Cypripedium macranthos Sw. alba) were collected 65 days after pollination in 2018. The green pods were sterilized with flame and sowed immediately on the POM(Phytomax orchid maintenance media(R), Sigma) supplemented with BAP 0, 0.5, 1.0 mg/L and NAA 0, 1, 2mg/L. The germination of seed was observed 90 days after sowing, and the plantlets were subcultured to the same media according to the size of the protocorm with 1~2, 2~3, 3~4, 5~6, 7~8mm. The time of the subculture to the new media seems to be critical factors of forming rhizoids which is the hairy root of the cypripediums. As a results, the protorms of the white lady's slipper orchid was successfully germinated in the POM media supplemented BAP 0.5 and NAA 1.0 mg/L. The roots and rhizoids were formed in 5~6mm protocorms subculture over 95% survival ratio. We also tried to subculture to liquid medium without activated charcoal, however the browning or malformation of the roots was observed in the root. The formation of shoots from the protocorm was effectively enhanced in the POM media with non-additives of plant growth regulators. These results indicate the possibility of high and stable production and practical industrialization of endangered white lady's slipper orchids.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.116-123
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• 2019

Thermal batteries are also called molten-salt batteries as the electrolyte is mainly composed of molten salt. The molten-salt electrolyte is a solid that does not conduct electricity at room temperature, but when it is melted by a pyrotechnic heat source, it becomes an excellent ionic conductor. Thermal batteries are a kind of pyrotechnic battery because they operate only when the solid electrolyte is melted by the heat energy provided by pyrotechnic materials. Pyrotechnic components used in a thermal battery include heat sources, fuse strips, and an igniter. The reliability of these pyrotechnic components critically affects the reliability and performance of the battery that must supply electricity stably to guided munitions even under extreme environmental conditions. Different igniter types offer different advantages: notch-type igniters offer improved ignition probability, whereas film-type igniters offer improved safety. The addition of metal oxides to the heat paper could improve the burn rate, and the ignition reliability could be greatly improved by using it with a flame igniter at the same time. Using a two-step reduction process, high-purity Fe particles in coral form can be safely obtained.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.314-320
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• 2022

The function of reinforcing fibers used in building materials is to maintain resistance to bending loads and to function for cracking caused by drying shrinkage. High-density fiber-cement composites are mainly used for linear plates and are used to increase bending resistance. Therefore, tensile properties, bonding strength with cement hydrate, alkali resistance, and the like are required. Recently, as the non-combustible performance has been strengthened, a function to minimize the occurrence of sparks during high-temperature heating has been added. Therefore, the use of organic fibers is limited. In this study, a study was conducted to replace polypropylene used as reinforcing fiber with hemp fiber with excellent heat resistance. Hemp fibers have excellent heat resistance, good affinity with cement, and excellent alkali resistance. Based on the total volume of polypropylene fibers used in the existing formulation, the non-combustible performance was compared and evaluated by using hemp fibers instead of the polypropylene fibers, and basic physical properties such as flexural strength were tested. As a result of conducting a non-combustibility and physical property test using hemp fibers with a fiber length of 7 mm using 2 % and 3 % by weight, it was found that there is no remaining time of the flame, and the flexural strength can be secured at 95 % level of the existing polypropylene fiber.

• Journal of the Korean Wood Science and Technology
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• v.10 no.1
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• pp.5-37
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• 1982

Plywood used for construction as a decorative inner material is inflammable to bring large fire accidents and burn out human life and their properties. To diminish the fire disaster, fire retardant plywood has been required indeed. In the methods of manufacturing the fire retardant plywood the soaking method is occasionally used. However after soaking plywood into fire retardant chemical solutions, redrying of soaked plywood is the most important. In this study, 3.5mm thin and 5.0mm thick plywoods were selected for fire retardant treatment. Treating solutions were prepared for 20% dilute solutions of ammonium sulfate, monoammonium phosphate, diammonium phosphate, borax-boric acid and minalith, and water solution. 1-, 3-, 6-, and 9 hour-soaking treatments were applied and after treatments hot plate drying was applied to those treated plywoods at $90^{\circ}C$, $120^{\circ}C$ and $150^{\circ}C$, of press temperature. Drying rates, drying curves, water absorption rates of fire retardant chemicals, weight per volume and fire retardant degree of plywood were investigated. The results may be summarized as follows: 1. The plywoods treated with ammonium sulfate, monoammonium phosphate and diammonium phosphate and diammonium phosphate showed increase of chemical absorption rate with proportion to increase of treating time, but not in case of the plywood treated with borax-boric acid and minalith. 2. In the treatment of definite time, the absorption rate per unit of volume of plywood showed higher in thin plywood (thickness of 3.5mm) than in thick plywood (thickness of 5.0mm). In both thin and thick plywoods, the highest absorption rate was observed in 9 hour-treatment of ammonium sulfate. The value was 1.353kg/$(30cm)^3$ in thin plywood and 1.356kg/$(30cm)^3$ in thick plywood. 3. The volume per weight of plywood after chemical treatment increased remarkably and. after hot plate drying, the values were to a little extent higher than before chemical treatment. 4. The swelling rates of thickness in chemical-treated plywoods increased similarly with that of water-treated plywood in 1- and 3 hour-treatment of both thin and thick plywoods. But in 6- and 9 hour-treatment, the greater increased value showed in water-treated ply wood than any other chemical, especially in thick plywood. 5. The shrinkage rates after hot plate drying showed the same tendency as the swelling rate, and the rate showed the increasing tendency with proportion to increase of treating time in thick plywood of both chemical and water treatments. 6. Among drying curves, the curves of water-treated plywood placed more highly than chemical-treated plywood without-relation to thickness in 6- and 9 hour-treatment except in 1- and 3 hour-treatment. 7. The drying rate related to thickness of treated plywood, was twice above in thin plywood compared with thick plywood. 8. The drying rate remarkably increased with proportion to increase of the plate temperature and, the values were respectively 1.226%/min., 6.540%/min., 25.752%/min. in hot plate temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in thin plywood and 0.550%/min., 2.490%/min, 8.187%/min, in hot plate temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in thick plywood. 9. In the treatment at $120^{\circ}C$ of hot plate temperature, the drying rates of chemical-treated plywood showed the highest value in monoammonium phosphate of thin plywood and in diammonium phosphate of thick plywood. But the drying rate of water-treated plywood was highest in 6- and 9 hour-treatment. 10. The fire retardant degree of chemical-treated plywood was higher than that of the untreated plywood as shown in loss of weight, burning time, flame-exhausted time and carbonized area. 11. The fire-retardant effect among fire retardant chemicals were the greatest in diammonium phosphate, the next were in monoammonium phosphate and ammonium sulfate, and the weakest were in borax-boric and minalith.

• Journal of Food Hygiene and Safety
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• v.32 no.4
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• pp.284-289
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• 2017

Oxidized polyethylene wax (OPEW) is, one of the food additives, used as a coating agent in citrus fruits and nuts. OPEW is authorized to quantum satis in EU, USA, and is acceptable less than 250 mg/kg in Australia and New Zealand. But OPEW is unauthorized as a food additive in Korea. This study was to establish the analytical method of OPEW and demonstrate the effective application of various food samples. We first conducted to compare the various analytical method including acid value (AV), high temperature gel permeation chromatography (HT-GPC), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS), gas chromatography flame ionization detector (GC-FID) and fourier transform infrared spectroscopy (FT-IR). This result indicated that FT-IR spectrum of OPEW treated food sample displayed absorption bands for carbonyl group (C=O, $1714cm^{-1}$), ester group (C-O, $1463cm^{-1}$), aliphatic group (C-H, $2916cm^{-1}$). Furthermore, IR spectrum of OPEW treated food sample showed similar tendency with IR spectrum of OPEW standard. Therefore, it is confirmed that analytical method using FT-IR can be detected on analysis of OPEW in food. As a result of monitoring of 111 samples using established analytical method, OPEW was not detected in the food samples.

• Journal of Science Education
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• v.35 no.1
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• pp.80-90
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• 2011

The purpose of this study is to investigate manual skills of experimental apparatuses of pre-service elementary school teachers by examining and analyzing the process of experiments conducted by pre-teachers. For this study, 24 pre-service elementary school teachers were selected as the subjects and 4 experimental apparatuses were chosen through analyzing science textbooks from 3rd grade to 6th grade in elementary school. The selected experimental apparatuses were alcohol burner, dropper, microscope, instruments for making a prepared specimen. In addition, a task was carefully chosen to conduct an investigation in real settings and a series of evaluation standards was developed. While 3 subjects conducted experiments in separated and independent space at the same time, 3 collaborators observed the experiment process and recorded whether the subject met the evaluation standards or not, using O, X. The study suggests that pre-service elementary school teachers' manual skills of experimental apparatuses were under far below our projections. Particularly, in case of alcohol burner, the subjects showed lower ability to properly light the burners - which is to brush through the lampwick with fire - and to adjust the height of tripods according to the flame. Also, when it comes to dropper, they were not held the way they were supposed to be. In addition, when designing prepared specimen, the subjects used their hands instead of tweezers and often skipped the process of dripping water drop and wiping water with an oilpaper. Moreover, they did not know how to use a microscope properly so there were many times that they could not focus a microscope, failing to observe the objects. Educational implications are discussed.

• The Korean Journal of Nuclear Medicine
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• v.38 no.3
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• pp.259-267
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• 2004

Purpose: NEMA NU2-2001 was proposed as a new standard for performance evaluation of whole body PET scanners. in this study, system performance of Siemens CTI ECAT EXACT 47 PET scanner including spatial resolution, sensitivity, scatter fraction, and count rate performance in 2D and 3D mode was evaluated using this new standard method. Methods: ECAT EXACT 47 is a BGO crystal based PET scanner and covers an axial field of view (FOV) of 16.2 cm. Retractable septa allow 2D and 3D data acquisition. All the PET data were acquired according to the NEMA NU2-2001 protocols (coincidence window: 12 ns, energy window: $250{\sim}650$ keV). For the spatial resolution measurement, F-18 point source was placed at the center of the axial FOV((a) x=0, and y=1, (b)x=0, and y=10, (c)x=70, and y=0cm) and a position one fourth of the axial FOV from the center ((a) x=0, and y=1, (b)x=0, and y=10, (c)x=10, and y=0cm). In this case, x and y are transaxial horizontal and vertical, and z is the scanner's axial direction. Images were reconstructed using FBP with ramp filter without any post processing. To measure the system sensitivity, NEMA sensitivity phantom filled with F-18 solution and surrounded by $1{\sim}5$ aluminum sleeves were scanned at the center of transaxial FOV and 10 cm offset from the center. Attenuation free values of sensitivity wire estimated by extrapolating data to the zero wall thickness. NEMA scatter phantom with length of 70 cm was filled with F-18 or C-11solution (2D: 2,900 MBq, 3D: 407 MBq), and coincidence count rates wire measured for 7 half-lives to obtain noise equivalent count rate (MECR) and scatter fraction. We confirmed that dead time loss of the last flame were below 1%. Scatter fraction was estimated by averaging the true to background (staffer+random) ratios of last 3 frames in which the fractions of random rate art negligibly small. Results: Axial and transverse resolutions at 1cm offset from the center were 0.62 and 0.66 cm (FBP in 2D and 3D), and 0.67 and 0.69 cm (FBP in 2D and 3D). Axial, transverse radial, and transverse tangential resolutions at 10cm offset from the center were 0.72 and 0.68 cm (FBP in 2D and 3D), 0.63 and 0.66 cm (FBP in 2D and 3D), and 0.72 and 0.66 cm (FBP in 2D and 3D). Sensitivity values were 708.6 (2D), 2931.3 (3D) counts/sec/MBq at the center and 728.7 (2D, 3398.2 (3D) counts/sec/MBq at 10 cm offset from the center. Scatter fractions were 0.19 (2D) and 0.49 (3D). Peak true count rate and NECR were 64.0 kcps at 40.1 kBq/mL and 49.6 kcps at 40.1 kBq/mL in 2D and 53.7 kcps at 4.76 kBq/mL and 26.4 kcps at 4.47 kBq/mL in 3D. Conclusion: Information about the performance of CTI ECAT EXACT 47 PET scanner reported in this study will be useful for the quantitative analysis of data and determination of optimal image acquisition protocols using this widely used scanner for clinical and research purposes.

• Journal of Korean Society of Forest Science
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• v.56 no.1
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• pp.1-25
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• 1982

Plywood used for construction as a decorative inner material is inflammable and can cause fire accidents. causing destruction of human life and property. To diminish the fire disaster, fire retardant plywood is indeed required. In the methods of manufacturing the fire retardant plywood, a soaking method is occasionally used. However after soaking plywood into fire retardant chemical solutions redrying of soaked plywood is of the utmost importance. In this study 3.5mm and 5.0mm thickness plywoods were selected for fire retardant treatment. Treating solutions were prepared for 20% dilute solutions of ammonium sulfate, monoammonium phosphate, diammonium phosphate, borax-boric acid minalith, and water solution, 1-, 3-, 6-, and 9 hour-soaking treatments in borax-boric acid and minalith, and 6- and 9 hours in the other chemicals were applied and after the treatment hot drying was applied to treated plywoods at $90^{\circ}C$, $120^{\circ}C$ and $150^{\circ}C$ of press temperature. Drying rates, drying curves, water absorption rates of fire retardant chemicals, weight per volume and fire retardant degree of plywood were investigated. The results may be summarized as follows: 1) In the 9 hours-soaking treatment of fire retardants by hot and cold bath method, the chemical retentions of 3.5mm thickness plywood could be attained within the range ($1.125-2.25kg/(30cm)^3$) of minimum retention specification as follows: $1.353kg/(30cm)^3$ in monoammonium phosphate, $1.331kg/(30cm)^3$ in diammonium phosphate, $1.263kg/(30cm)^3$ in ammonium sulfate, $1.226kg/(30cm)^3$ in borax-boric acid. But the chemical retention, $0.906kg/(30cm)^3$, in minalith could not be attained within the range of minimum retention specification. And also in case of 5.0mm thickness plywood, chemical retentions, as $1.356kg/(30cm)^3$ and $1.166kg/(30cm)^3$ respectively, of ammonium sulfate and diammonium phosphate could be attained within the range minimum retention specification, but the other fire retardant chemicals could not. 2) In the 6- and - hours-soaking treatments of 3.5mm and 5.0mm thickness plywood, the drying curve sloped of chemical treated plywood was smaller than that of water treated. The drying rate related to thickness of treated plywood, was about three times as fast in 3.5mm thickness plywood compared with 5.0mm thickness plywood. 3) In the treatment at $120^{\circ}C$ of hot platen temperature, the drying rates of chemical-treated plywood showed the highest quantity in diammonium phosphate of 3.5mm and 5.0mm thickness plywood. But the drying rate of water treated plywood was highest during the 6- and 9 hours-soaking treatments. 4) The drying rate remarkably increased with proportion to increase of the platen temperature, and the values were respectively 1.23%/min., 6.54%/min., 25.75%/min. in hot platen temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in 3.5mm thickness plywood and 0.55%.min., 2.49%/min., 8.19%/min. in hot platen temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in 5.0mm thickness plywood. 5) In the fire retardant degree of chemical treated plywood, the loss in weight was the smallest in diammonium phosphate, next was in monoammonium phosphate and ammonium sulfate, and the greatest was in borax-boric acid and minalith. And the fire-retardant effect in burning time, flame-exhausted time and carbonized area were greatest in diammouniun phosphate, next were in monoammonium phosphate and ammonium sulfate, and the weakest were in borax-boric acid and minalith.