• Journal of the Korean Society for Railway
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• v.16 no.2
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• pp.99-103
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• 2013

In this paper, research on the thermal analysis method is reported for the characterization of heat generation while operating an Interior Permanent Magnet Synchronous Motor (IPMSM) for railway vehicles. Efficient cooling of the heat generated in the IPMSM is important because the excessive heat generated from the winding, core and permanent magnets increases the difficulty of continuously operating an IPMSM over long time periods. Therefore, in this study, in order to analyze the heat generation characteristics of the IPMSM for advanced research in the application of IPMSMs to cooling devices, the heat transfer coefficients for each component of the IPMSM were derived and the thermal equivalent circuit was configured to perform thermal analyses. Finally, the validation of the suggested thermal analysis method was performed through comparison with the heat experimental data of an IPMSM prototype.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.759-769
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• 2021

For aerospace propulsion systems, Titanium Hydride Potassium Perchlorate (THPP) is a material commonly used as a pyrotechnic initiator that generates gas when energy is supplied or as a supplement charge for NASA standard initiator (NSI). However, when the energetic materials are stored for a long time, it faces the problem of 'aging'. In this study, changes in thermodynamic properties of THPP aged under various humidity environments were identified through thermal analysis and surface analysis. First, a considerable amount of cracks on the surface of the oxidant was found in the aged THPPs. Particularly, when the humidity level increased, the number and length of the cracks rapidly increased. Also, the deterioration of Viton was found only in the thermally aged sample whereas the oxidation of the fuel was more pronounced in the hygrothermally aged samples. The extracted kinetic parameters of THPP on the reaction progress vary greatly by the humidity level, indicating that moisture significantly changes the performance and combustion reaction of THPP, which may eventually result in a reduced lifespan.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.75-82
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• 2010

To study the combustion characteristics of forest fuel by fire intensity, the experiment of combustion characteristics on Pinus Densiflora living leaves, which is the weakest species to the forest fire, was delivered, using variables of heat flux(25 kW/$m^2$, 50 kW/$m^2$, 75 kW/$m^2$). With the equipment of Cone calorimeter, the characteristics of ignition, heat, smoke release, CO and $CO_2$ release, and mass loss were analyzed. Pinus Densiflora living leaves containing moisture of 60.66% were not ignited at the heat flux of variables 25 kW/$m^2$, 50 kW/$m^2$, 75 kW/$m^2$. In proportion to the heat flux value, heat release amount and heat release rate reached maximum value rapidly: higher variables came to the maximum by the half rapidity and the maximum value were twice higher than the former lower variables respectively. As for the smoke release, the less heat flux the variable had, the more smoke release it had, due to incomplete combustion. The release amount of CO and $CO_2$ had more maximum value as the heat flux increased and more radiant heat meaned more carbon oxide. When the forest fire breaks out, therefore, a great amount of CO and $CO_2$ will be released by Pinus Densiflora.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.12.2-12.2
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• 2008

• Proceedings of the Korean Information Science Society Conference
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• 2001.04b
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• pp.514-516
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• 2001

본 논문은 시차를 두고 촬영된 두 장의 치과용 디지털 X-Ray 영상으로부터 임플란트 시술환자에서 자주 발생하는 임플란트 주위염을 검출하는 자동화된 시계열 분석 방안을 제안한다. 분석자에 따라서 결과의 차이를 보이는 수동적인 시계열분석방법의 문제점을 극복하고 보다 객관적이고 정략적인 결과를 얻는 방안을 제시한다. 보다 신속하고 정확한 검출을 위해서 본 연구에서는 치아의 구조 분석을 통해서 환부 탐색 영역을 줄이고 작은 변화도 민감하게 검출할 수 있는 환부영역을 분리할 수 있는 방안을 제안한다. 또한 분리된 환부의 특성을 수치적으로 표현할 수 있는 방안도 함께 제시된다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1834-1835
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• 2011

본 논문에서는 22.9kV급 지중 전력 케이블의 열화에 의한 특성 변화를 분석한다. 케이블이 실제 선로로 포설될 경우 케이블에는 고전압이 흐르게 되고, 이로 인해 열이 발생하게 된다. 이와 같이 발생한 열에 의한 절연체 이상은 케이블 사고로 이어지므로 케이블의 열화 특성 분석은 사고를 미연에 방지하기 위해서 필요하다. 따라서 본 논문에서는 실제 선로에 사용된 후 교체된 케이블의 감쇠 상수를 구하여 열화가 진행된 정도에 따른 감쇠상수의 변화를 분석한다. 이 때, 네트워크분석기의 S-파라미터를 이용하여 감쇠 상수를 구하고, 정상 상태 케이블과 폐 케이블의 감쇠상수를 비교하여 열화에 의한 케이블의 특성을 분석한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.803-806
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• 2012

On this paper, various analysis methods has been applied to analyze and forecast the maximum electrical power needs, which is regarded as a nonlinear dynamic system. To understand the characteristic of complicated system, we used TISEAN package and evaluate the chaotic characteristic of time series obtained from electrical power demand using it. TISEAN package offers various algorithms and codes to analyze time series of nonlinear system effectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.65-65
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• 2003

청색 발광 LEDs의 개발과 상용화 이후에 백색조명등의 응용 가능성으로 인하여 이에 대한 많은 연구가 최근에 계속되고 있다 하지만 GaN의 많은 광학적인 장점에도 불구하고 이러한 소자의 기판으로 사용되고 있는 sapphire의 열악한 열적 특성은 소자의 열화를 야기할 수 있으며 특히 고출력작동 시에 소자성능 저하의 원인이 될 수 있다. 따라서 이러한 GaN를 기본으로 하는 LED의 경우 이에 대한 정확한 열 측정과 고출력 작동 시의 열적 모델링은 칩과 패키징 단위에서 모두 중요한 연구분야가 되고 있다. 고출력 GaN LED에 대하여 신뢰성에 관한 몇 가지 보고가 있지만, 이러한 보고의 대부분은 패키징 된 램프에 대한 분석이며 정작 칩에 대한 근본적인 열 분석과 신뢰성에 대한 연구결과는 미미한 실정이다 따라서 본 연구에서는 GaN LED 칩에 대하여 직접적인 열 분석을 시도하였다

• Fire Science and Engineering
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• v.21 no.3
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• pp.41-46
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• 2007

The combustion characteristics of surface forest fire fuels was analysed using variable external irradiation level. The characteristics such as ignition time, ignition temperature, critical heat flux and mass loss rate were measured. Fuel samples were exposed to incident heat fluxes from 8 to $50\;kW/m^2$. For the measurement of various combustion characteristics, the size of specimen holder was $100\;mm{\times}100\;mm{\times}12\;mm$ and the fuel samples grinded by electric mill were the fallen leaves of Quercus variabilis and Pinus densiflora. As results, the occurrence of ignition is possible to the heat flux more than $9\;kW/m^2$. The fuel of Pinus densiflora keeps its high temperature longer than that of Quercus variabilis during the combustion process. The results of measurement shows that the maximun and average mass loss rate of Quercus variabilis larger than that of Pinus densiflora.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.104-110
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• 2019

The thermal decomposition characteristics of boron-potassium nitrate ($BKNO_3$) were investigated by non-isothermal thermal gravimetric analysis (TGA). Two steps of mass loss were observed in the temperature range between room temperature and $600^{\circ}C$. Kinetic parameters of the thermal decompositions were evaluated from the measured TGA curves using the AKTS Thermokinetics Software. For the first step of mass loss ($220-360^{\circ}C$) corresponding to the thermal decomposition process of the binder (Laminac/Lupersol), the activation energy is in the range of approximately 120-270 kJ/mol when evaluated by Friedman's iso-conversional method, while the value of activation energy varies in the range of approximately 150-400 kJ/mol during the second step process ($360-550^{\circ}C$).