• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.78-83
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• 2019

In this study, we analyze the structure of the transceiver coil in the inductive power transfer (IPT) system. In the IPT system, the transceiver coil design needs to have the highest magnetic coupling possible because of the relatively low magnetic coupling due to the large gap of distance without the core. The transmitting coil may be formed as a multi-layer type according to the distance between the transmitting and receiving coils if the receiving coil is configured as a multi-layer type on the inner structure of the receiving apparatus, thereby improving the magnetic coupling and system efficiency. We compare and analyze the coil magnetic coupling, and system efficiency according to the layer structure of the transmitting and receiving coils and verify the analysis by JMAG simulation. Experimental results show that the layer structure of the transceiver should be considered according to the inner space of the receiving device and the spacing distance.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.109.2-109.2
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• 2015

Graphene, as a single layer of $sp^2$-bonded carbon atoms packed into a 2D honeycomb crystal lattice, has attracted much attention due to its outstanding properties such as high carrier mobility, chemical stability, and optical transparency. In order to synthesize high quality graphene, transition metals, such as nickel and copper, have been widely employed as catalysts, which need transfer to desired substrates for various applications. However, the transfer steps inevitably induce defects, impurities, wrinkles, and cracks of graphene. Here, we report a facile transfer-free graphene synthesis method through nickel and carbon co-deposited layer, which does not require separately deposited catalytic nickel and carbon source layers. The 100 nm NiC layer was deposited on the top of $SiO_2/Si$ substrates by nickel and carbon co-deposition. When the sample was annealed at $1000^{\circ}C$, the carbon atoms diffused through the NiC layer and deposited on both sides of the layer to form graphene upon cooling. The remained NiC layer was removed by using nickel etchant, and graphene was then directly obtained on $SiO_2/Si$ without any transfer process. Raman spectroscopy was carried out to confirm the quality of resulted graphene layer. Raman spectra revealed that the resulted graphene was at high quality with low degree of $sp^3$-type structural defects. Furthermore, the Raman analysis results also demonstrated that gas flow ratio (Ar : $CH_4$) during the NiC deposition and annealing temperature significantly influence not only the number of graphene layers but also structural defects. This facile non-transfer process would consequently facilitate the future graphene research and industrial applications.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.135-141
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• 2015

The core melts stratifies into lower mixture layer and upper metal layer by density in a severe accident condition. The decay heat generated from the mixture layer threatens the integrity of the reactor vessel. This study simulated the natural convection heat transfer of the mixture layer with volumetric heat source using the mass transfer system. $H_2SO_4-CuSO_4$ electroplating system was used as the mass transfer system. With the modified Rayleigh number of $3{\times}10^{14}$, the Nusselt number showed minimum at the bottom and increased along curvature to the top of the experimental apparatus.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.589-595
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• 2001

The present study conducted heat transfer analysis in multi-layer of CD-R. It is necessary to analyze heat transfer during the recording process to find optimum power and write strategy in CD-R. This study investigated effects of several parameters such as recording speed, laser power, layer thickness and thermal property. The calculated results presented temperature distribution in the multi-layer and detailed information of recording characteristics. Optimum laser power was estimated, comparing an optimum mark length with the calculated mark lengths. The results showed that the optimum laser power was influenced significantly by the layer thickness and the thermal properties of the dye.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.568-574
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• 2012

Turbulent boundary layer noise is already a significant contributor to sonar self noise. For developing acoustic window of sonar system to reduce self noise, a parametric study of design factors of acoustic window is presented. Distance of sensor array from acoustic window, material and damping layer are studied as design factors to influence in the characteristics of the transfer function of self noise. As the result these design factors make change the characteristics of transfer function slightly. Among design factors the location of sensor array is most important parameter in the self noise reduction.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.298-299
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• 2018

본 논문에서는 자기유도방식 무선전력전송(Inductive Power Transfer, IPT) 시스템에 적용되는 송수신 코일의 Multi-layer 구조의 자기결합 특성에 대하여 분석한다. 기존에 제안된 Single-layer 구조의 코일과 Multi-layer 구조의 코일이 가지는 차이점을 자기결합도 측면에서 비교 분석하고 이를 Simulation 및 실험을 통해 검증한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1119-1127
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• 2000

Convective heat transfer in a channel filled with porous media has been analyzed in this paper. The two-equation model is applied for the heat transfer analysis with the velocity profile, considering both the inertia and viscous effects. Based on a theoretical solution, the effect of the velocity profile on the convective heat transfer is investigated in detail. The Nusselt number is obtained in terms of the relevant physical parameters, such as the Biot number for the internal heat exchange, the ratio of effective conductivities between the fluid and solid phases, and hydraulic boundary layer thickness. The results indicate that the influence of the velocity profile is characterized within two regimes according to the two parameters, the Biot number and the conductivity ratio between the phases. The decrease in the heat transfer due to the hydraulic boundary layer thickness is 15% at most within a practical range of the pertinent parameters.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.996-1007
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• 2019

We investigated the influence of the aspect ratio (H/R) of the oxide layer on the reactor vessel heating in three-layer configuration. Based on the analogy between heat and mass transfers, we performed mass transfer experiments to achieve high Rayleigh numbers ranging from $6.70{\times}10^{10}$ to $7.84{\times}10^{12}$. Two-dimensional (2-D) semi-circular apparatuses having the internal heat source were used whose surfaces of top, bottom and side simulate the interfaces of the oxide layer with the light metal layer, the heavy metal layer, and the reactor vessel, respectively. Multi-cell flow pattern was identified when the H/R was reduced to 0.47 or less, which promoted the downward heat transfer from the oxide layer and possibly mitigated the focusing effect at the upper metallic layer. The top boundary condition greatly affected the natural convection of the oxide layer due to the presence of secondary flows underneath the cold light metal layer.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.12 no.1
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• pp.45-53
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• 2006

Thermal insulation is used in a variety of applications to protect temperature sensitive products from thermal damage. Several factors affect the performance of insulation packages. Among these factors, the thermal resistance of the insulating wall is the most important factor to determine the performance of the insulating package. In many cases, insulating wall consists of multi-layered structure and the heat transfer through this structure is a very complex process. In this study, an one-dimensional mathematical model, which includes all of the heat transfer principles covering conduction, convection and radiation in multi-layered structure, were developed. Based on this model, several heat transfer phenomena occurred in the air space between the layer of the insulating wall were investigated. From the simulation results, it was observed that the heat transfer through the air space between the layer were dominated by conduction and radiation and the low emissivity of the surface of each solid layer of the wall can dramatically increase the thermal resistance of the wall. For practical use, an equation was derived for the calculation of the thermal resistance of a multi-layered wall.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.1
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• pp.32-40
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• 1994

The radiative heat transfer analysis in particle layer has an inherent difficulty in treating the governing integro-differential equations, which are derived from the remote effects. Most of the existing analyses are limited to the one dimensional system, taking into account only absorption or isotropic scatting of solid particles. Fortunately, a new Monte Carlo Simulation method is recently developed to analyse multidimensional radiative heat transfer in particles with anisotropically scatting. By this method, the present study analyses the radiative heat transfer in dispersed particles through the numerous droplets in the liquid droplet radiator to develop a technique of liquid droplet radiator. Consequently, knows that the radiative heat flux in particle layer is influenced by exitinction coefficient, optical thickness and surface area of particles in the system.