• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.365-369
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• 2004

The Advantages of hot machining are the reduction of cutting forces, tool wear, and the increase of material removal rates. In this study, a hot-machining using gas flame heating characteristics of milling by CBN tip was analyzed, and the influence of the surface temperature and the depth of cut on the tool life were investigated. The results show that hot machining of tungsten carbide-alloyed is more effective than conventional machining. In addition, some advantages obtained from hot machining, such as decrease of tool wear and cutting force, high surface quality.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.102-103
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• 2002

금속 입자들이 채워진 유리는 광 호변성 물질로써 광 저장 디스크, 광 도파로 그리고 도파로 레이저, 광 스위치 등의 다양한 응용분야에 이용될 수 있음이 여러 연구진들에 의해서 밝혀져 왔다. [1] 광 호변성이란 외부에서 입사되는 광에 의해서 유리의 색이 변색되는 현상인데 이는 유리에 함유된 물질들이 광이나 열에 의해서 변화하기 때문이다. Wood 등은 열처리와 불꽃에 의한 가열 등을 이용하여 은 입자를 작은 입자로 쪼개고. 이를 엑시머 레이저로 열처리시키면 은 입자가 분해된다는 것을 보였다. (중략)

• Proceedings of the KIEE Conference
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• summer
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• pp.521-523
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• 2004

산불과 같은 대형화재는 철탑의 전선이나 애자와 같은 부착물의 기능에 많은 장애를 유발할 수 있어 송전선로 운영에 큰 영향을 미치게 될 수 있다. 만약 이와 같은 재해로 인해 송전선로의 운영에 차질이 생긴다면 산업전반에 걸쳐 엄청난 파급효과를 초래시킬 것이 다. 본 논문에서는 산불과 같은 화재가 송전용 폴리머애자에 미치는 영향을 파악하기 위하여 산불의 불꽃을 모의한 실험장치를 제작하였으며, 시료로는 현재 송전선로에 사용되고 있는 송전용 폴리머애자를 축소 제작한 폴리머애자와 자기애자를 사용하였다. 산불모의 인공화염 실험은 가열시간의 경과에 따라 폴리머애자의 하우징과 자기애자의 디스크 변화를 관찰하였고, 가열실험이 끝난 애자들을 이용하여 전기적인 시험과 기계적인 시험을 행하였다. 이 실험 데이터를 바탕으로 폴리머애자와 자기애자의 특성변화를 비교 분석하여 산불영향이 송전용 폴리머애자에 미치는 영향을 연구하였다.

• Korean Journal of Microbiology
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• v.11 no.2
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• pp.101-106
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• 1973

The microwave of 2450 MHz, generated by a household cooking oven, was evaluated for its applicability to melt various rehydrated media and to remove dissolved oxygen from tubed media for anaerobic culture. The effect on the sterilization of E. coli in selective media was also evaluated. The following results were obtained. 10 The microwave oven was useful in saving time for melting media and in eliminating heat and combustion gas from the laboratory, which were inevitable by-products in the conventional flame method. 2) Dissolved oxygen could be removed without boiling over by exposing the tubes of anaerobic culture medium after putting them in a wire basket in a beaker with water. 30 The count of E. coli during the melting of MacConkey and EMB agar were similar to those treated with open flame. The microwave treatment was not considered a possible mean to replace autoclaving even in these selective media.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.74-80
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• 2002

In this study, a numerical method for fuel droplet evaporation in cylinder of S.I. engine is presented. This study was newly defined non-dimensional critical droplet lifetime and modeled heating and evaporation processes of fuel droplet during intake and compression stroke of gasoline engine. The simulation results show that simultaneous increase of gas temperature and pressure in compression stroke seems to have compensative effect on droplet gasification rate. The environment variations in cylinder have little effect on the fuel droplet gasification process. The droplet size for full evaporation at the end of compression stroke can be estimated using this program.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.52-60
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• 2002

Line heating is a forming process which makes the curved surface with the residual strain created by applying heat source of high temperature to steel plate. in order to control the residual strain, it is necessary to understand not only conductive heat transfer between heat source and steel plate, but also temperature distribution of steel plate. In this paper we attempted to analyze is temperature distribution of steel plate by simplifying a line heating process to collision-effusive flux of high temperature and high velocity, and conductive heat transfer phenomenon. To analyze this, combustion in the torch is simplified to collision effusive phenomenon before analyzing turbulent heat flux. The distribution of temperature field between the torch and steel plate is computed through turbulent heat flux analysis, and the convective heat transfer coefficient between effusive flux and steel plate is calculated using approximate empirical Nusselt formula. The velocity of heat flux into steel plate is computed using the temperature distribution and convective heat transfer coefficient, and temperature field in the steel plate is obtained through conductive heat transfer analysis in which the traction is induced by velocity of heat flux. In this study, Finite Element Method is used to accomplish turbulent heat flux analysis and conductive heat transfer analysis. FEA results are compared with empirical data to verify results.

• 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.

• Fire Science and Engineering
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• v.25 no.3
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• pp.91-98
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• 2011

This study is about fire resistance performance of wood framed lightweight wall including a middle lintel as a traditional wall form in Korea. The target wall is non-loadbearing system which constructed with $38{\times}89$ mm ($2"{\times}4"$) wood frame and fireproof gypsum board covering, including a middle lintel made of $150{\times}150$ mm section glue-laminated timber. As a test results, all specimens have showed fire resistant performance over 90 minutes and tests were maintained until flame occuring on Specimen-l, 2, 3 at 91 min, 97 min and 98 min respectively. Fire resistance of the heat side gypsum board was 45 minutes and charring rate of middle lintel was equivalant with that of usual timber. The wood stud inside wall system showed relatively quick combution characteristic when exposed to high temperature with no temperature rising delaying time caused by moisture evaporation because of the dehydration preceded during the early period of fire side gypsum board resist to heat.

• Analytical Science and Technology
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• v.28 no.3
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• pp.236-245
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• 2015

Recently, candles have been widely used to create a romantic atmosphere and to heat tea. In this study, a small combustion chamber for candle was designed using an 0.008 m³ bell jar. The emission factors of combustion products were then measured. The combustion chamber includes a glass dish, which prevents candle flame from affecting the composition of the gas emitted through the exhaust outlet. The outlet in the combustion chamber was designed as a cone shape, and it was lengthened to prevent flow from the outside, which could affect the homogeneous composition of the exhaust gas. The temperature at the outlet of the chamber was 34 ℃~41℃. The major combustion products of the candle, such as such aldehydes and acids, contained oxygen. The mass specific emission rates of benzene, toluene, ethylbenzene, and TVOC were 0.04 μg/g, 0.01 μg/g, 0.02 μg/g, and 3.81, respectively. The mass specific emission rates of formaldehyde, acetaldehyde and benzaldehyde were 4.48 μg/g, 1.09 μg/g, and 0.67 μg/g, respectively. Considering the different compositions of the candle samples, their mass specific emission rates were similar to those obtained by using a large chamber 0.17 m³~50 m³ in size.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.355-361
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• 2002

본 연구에서는 원적외선.열풍 복합건조특성을 구명하기 위하여 건조용량 150-500kg이고, 승강기, 상.하부스크류, 건조실, 템퍼링실, 송풍기 및 가열장치로 구성된 시뮬레이터를 제작하여 건조특성시험을 실시하였다. 그 결과를 요약하면 다음과 같다. 가. 열풍온도에 따른 곡온변화를 시험한 결과 열풍온도 45$^{\circ}C$일 때 곡온 32-33$^{\circ}C$를 유지하였으며, 48, 51$^{\circ}C$일 때는 곡온이 35$^{\circ}C$가 넘어서는 현상을 나타났다. 건조중 곡온이 35$^{\circ}C$를 넘어서게 되면 동할미 발생량이 많아지고 품질저하가 급격히 일어난다. 나. 템퍼링실의 온도편차가 2,5$^{\circ}C$ 정도로 고른 온도분포를 나타내었고, 버너 입구쪽과 템퍼링실 중앙지점에서 온도가 약간 높게 나타났으며, 원적외선방사체 표면온도분포는 열풍온도가 45$^{\circ}C$일 때 평균 17$0^{\circ}C$를 유지하였고, 48$^{\circ}C$, 51$^{\circ}C$일 때 각각 22$0^{\circ}C$, 23$0^{\circ}C$에서 유지하는 것으로 나타났다. 다. 원적외선방사체 길이방향으로 온도편차는 버너를 기준으로 해서 버너쪽에서 멀수록 온도가 높았고, 중간, 근거리 순으로 나타났다. 버너의 원거리쪽에서 온도가 높게 나타난 것은 원적외선방사체를 통과하는 열풍이 빠져나가도록 되어있는 열풍 유동관이 버너 원거리에 위치하고 있어 버너에 불꽃이 점화되면서 열풍이 방사체 끝쪽으로 일시 머물렀다가 배출되기 때문으로 판단된다. 라. 건조기의 송풍량을 요인으로 하여 건조속도와 건조에너지를 비교한 결과 송풍량이 30cmm일 때가 25cmm에서보다 약 33%의 건조속도가 증가되어 송풍량이 많을수록 건조속도가 빨라졌으나, 건조에너지는 1,391kcal/kg.water로 나타나 약 4.2%정도가 더 소요 되었다. 곡물순환속도를 요인으로 하여 비교 시험한 결과 곡물순환속도가 33kg/min일때가 26kg/min보다 약 25%의 건조속도가 증가되어 곡물의 순환속도가 빠를수록 건조속도가 빨라졌으며, 건조에너지도 1,334kcal/kg.water로 비슷하게 소요되었다. 마. 시험구와 대비구의 건감률은 시험구에서 1.08~1.36w.b./h로 나타나 대비구보다 약 9.9~18.3%가 높게 나타났고, 건조에너지는 10.2~14.6%가 절감되었다. 발아율은 열풍온도가 낮을수록 높게 나타났고 시험구가 대비구보다 발아율이 낮게 나타났으며, 동할률 증가량도 원적외선.열풍 복합건조방법이 높게 나타나 이것은 곡물 표면에 원적외선 방사에의한 복사열이 전달되어 열장해를 받았기 때문으로 판단되며, 금후 더 연구하여 적정 열풍온도 및 방사체 크기를 구명해야 할 것이다.