• Journal of Power System Engineering
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• v.4 no.4
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• pp.16-24
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• 2000

고체내의 열에너지의 전달을 분석하기 위하여 고전적인 Fourier 열전도 법칙과 에너지 보존식에서 유도되는 열전도 방정식을 사용해 왔다. 이러한 열전도 방정식은 열전도가 무한한 속도로 진행된다는 것을 의미하고 있다. 그러나 극저온상태에서나 매우 급속한 열전도과정 중 매우 짧은 시간의 상태에서 non-Fourier 모델에 기초를 둔 쌍곡선형 열전도 방정식이 도입되었다. 최근의 이에 관한 연구에서 열전도가 파장의 형태로 유한한 전파속도를 갖는다는 것이 실험적으로 증명되었고 이로부터 여러 가지 실험적인 해석과 이론 해석이 전개되었다. 본 논문에서는 열전파 속도의 유한한 성질을 나타내는 수정된 열전도 법칙을 이용하여 1차원 평판에 대하여 공간에 대한 finite Fourier 변환 방법과 Green 함수 방법으로 해석하여 열전도파의 파동 성질, 공진 현상 및 위상차를 고찰하고자 한다. 열전도파가 갖는 모달 주파수에 대해 임계값을 갖으며 이 임계값을 초과할 때 공진 현상과 위상차를 고찰할 수 있었다.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.341-346
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• 2020

Motion sickness or dizziness caused by visual and other sensory inconsistencies In virtual reality content seems to be a major problem. To solve the problem, research has been actively underway to satisfy the five senses. Among them, the most researches on the touch are many studies on hardness and texture, but the studies on temperature seem relatively small. Therefore, in this paper, we present a calculation model that can sense the temperature derived from the principle of heat energy moving from high temperature to low temperature, not the temperature of the material. Because heat energy is determined by the heat conductivity, temperature, and area of contact, which are the inherent characteristics of a material, the degree of heat felt by a person depends on the type of material, the temperature of the material and the area of contact with the object. The thermal energy shift per unit time of the material was calculated using the thermal conductivity law and the specific heat formula, and the thermal energy reproduction method that changes per unit time of the material was studied using the thermoelectric element.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.540-545
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• 1999

The classical Fourier heat conduction equation is invalid at temperatures near absolute zero or at very early times in highly transient heat transfer processes. In such situations, a hyperbolic equation model for heat conduction based on the modified Fourier law is introduced because the wave nature of heat propagation becomes dominant. The Fourier model and the hyperbolic model for heat conduction are analyzed by using the Green's function technique together with the integral transform. Analytical expressions for the heat flux and temperature distributions in a finite slab subjected to a periodic surface heating at one of its surfaces are presented and the results obtained from each model are compared with each other. The thermal wave implied b the hyperbolic model is shown to travel through a medium and to reflect back toward the origin at the other insulated surface. On the other hand, the heat by the Fourier model propagates at an infinite speed instantaneously after a thermal disturbance is felt throughout the medium.

• Journal of Ocean Engineering and Technology
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• v.32 no.2
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• pp.84-94
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• 2018

Subsea pipelines are designed to transport mixtures of oil, gas, and their associated impurities from a wellhead that can be in excess of approximately $100^{\circ}C$, while the external temperature may be approximately $5^{\circ}C$. Heat can be lost from a subsea pipeline containing a high-temperature fluid to the surrounding environment. It is important that the pipeline be designed to ensure that the heat loss is small enough to maintain sufficient flow from the unwanted deposition of hydrate and wax, which occurs at a critical temperature of about $40^{\circ}C$. Therefore, it is essential to estimate the heat loss of a subsea pipeline in various circumstances. In previous studies, overall heat transfer coefficient(OHTC) formulas were considered only for a single soil type. Thus, it is difficult to characterize the OHTC of the actual seabed with multiple soil layers. In this paper, an OHTC formula that considers multi-layered soils is proposed for more precise OHTC estimation.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.65-70
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• 2015

A study on thermal properties for a single-layer metal and two-layer composites was investigated for the heat-sink application. For the single-layer metal, an aluminum alloy (Al6061) was selected. A screen printed aluminum nitride (AlN) layer on the Al6061 substrate was chosen for the two-layer composites. The thermal conductivity of the sample was determined from the thermal diffusivity measured by the light flash analysis (LFA), specific heat and density. Measured thermal property values were compared to calculated values using the data from the references. The thermal conductivity of composites with screen printed AlN layer on the Al6061 substrate decreased linearly with increasing the thickness of AlN layer. Measured values of the thermal conductivity for composites with $53{\mu}m$ and $163{\mu}m$ thick AlN layers were $114.1W/m{\cdot}K$ and $72.3W/m{\cdot}K$, respectively. In particular, the thermal conductivity of the screen-printed AlN layer was demonstrated by appling the rule of mixture in view point of thermal resistivity. Measured values of the thermal conductivity for AlN layers with the thickness of $53{\mu}m$ and $163{\mu}m$ showed $9.35W/m{\cdot}K$ and $12.40W/m{\cdot}K$, respectively.

• Journal of Sensor Science and Technology
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• v.9 no.4
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• pp.288-296
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• 2000

Thin-film chromel-alumel multijunction thermal converters with a low output resistance of $64{\sim}85\;{\Omega}$ showed approximately the square law-dependent input-output relation. The voltage responsivities were very low with $0.34{\sim}0.67\;V/W$ in air and $1.15{\sim}1.48\;V/W$ in vacuum, respectively, and the ac-dc voltage transfer error was very large with about +340 ppm in the frequency range of $40\;Hz{\sim}10\;kHz$ in the case of 1 V-input sinewave rms voltage. It can be concluded that the large transfer error of the thermal converter was mainly caused by the low voltage responsivity and the large heat loss due to low output resistance, which implies that the optimization for small ac-dc transfer error is required.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.7-12
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• 2008

An experimental study has been conducted to investigate the effect of tunnel slope on critical velocity by using the model funnel of the 1/20 reduced-scale applying the Floods scaling law. the square liquid pool burners were used for methanol, acetone and n-heptane fires. tunnel. Tunnel slopes varied as five different degrees $0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$ and $8^{\circ}$. The mass loss rate and the temperatures are measured by a load celt and K-type thermocouples for tunnel slope. Present study results in bigger the critical velocity than the research of Atikinson and Wu using the propane burner. Therefore, when estimating the critical velocity in slope tunnel, the variations of the heat release rate is an important factor. The reason is the ventilation velocity directly affects variation of heat release rate when slope tunnel fire occurred.

• The Journal of Korean Philosophical History
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• no.38
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• pp.189-220
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• 2013

In this paper, the discussion on Yin and Yang and the Five Elements in Mohism is examined through the comparison with Hundred Schools of Thought. The ideas of School of Naturalists including Zou Yan or those of the Five Elements were fundamentally for the purpose of observing the regularity of changing dynasty. However, this perspective had not been emphasized as a subject of Contention of a Hundred Schools of Thought until the end of the Era of Warring States. Even though it is true that Hundred Schools of Thought applied the theory of Yin and Yang and the Five Elements in common based on the understanding of the idea, but it failed to be connected to each ideological system. The fundamental reason for this can be found in the difference between the awareness of a reality and the concept of history in Hundred Schools of Thought. Where were the characteristics and reasonable opinions of the theory of Yin and Yang and the Five Elements in Mohism from? The most important feature of Mohism is to form independent, collective, cooperative groups based on the people of lower classes at that time and to consider God an ideological presumption. Therefore, in reality, it concentrated only on sociopolitical stability and maintenance of their own labor activities, and it was difficult for them to focus on an objective regularity of a national system or change of dynasty. In addition, due to the characteristics of individual groups, it was hard to have a macroscopic viewpoint not only on a national system, but also on others as in Zou Yan's Dae-gu-ju-seol(大九州說). With respect to this, at least, Xunzi, before the unification, gives a valid criticism. In the end, the effort to design a new political system and to secure ideological legitimacy on the assumption of the unification of the nations of the Warring States period became more specific through the edition of $L{\ddot{u}}shi$ Chunqiu (呂氏春秋), so-called Mixed School(雜家) or Synthesized School(綜合家).