• 정보저장시스템학회논문집
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• 제2권1호
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• pp.85-90
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• 2006

In this study, measurement of thermal conductivity of multilayer thin dielectric film has been conducted via differential $3\omega$ method. Also, verification of differential $3\omega$ method has been accomplished with various proposed criteria. The target film for the measurement is 300 nm thick silicon dioxide which is covered with upper protective layer of various thicknesses. The upper protective layer is inserted between the target film and the heater line for purpose of electrical insulator or anti-oxidation barrier since the target film may be a good electrical conductor or a well-oxidizing material. Since the verification of differential $3\omega$ method has not been conducted yet, we have shown that the measurement of thermal conductivity of thin films with upper protective layer via differential $3\omega$ method is verified to be reliable as long as the proposed preconditions of the samples are satisfied. Experimental results show that the experimental errors tend to increase with aspect ratio between thickness of the upper protective layer and width of the heater line due to heat spreading effect.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.254-259
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• 2005

In this study, measurement of thermal conductivity of multilayer thin dielectric film has been conducted via differential 3$\omega$ method. Also, verification of differential 3$\omega$ method has been accomplished with various proposed criteria. The target film for measurement is 300 nm silicon dioxide and this thin film is covered with various thicknesses of upper protective layer. The upper protective layer is inserted between the target film and the heater line for purpose of electrical insulator or anti-oxidation barrier since the target film may be a good electrical conductor or a well-oxidizing material. However, the verification of differential 3$\omega$ method has not been conducted. Thus we have shown that the measurement of thermal conductivity of thin films with upper protective layer via differential 3$\omega$ method is verified to be reliable as long as the proposed preconditions are satisfied. Experimental results show that the experimental errors tend to increase with aspect ratio between upper protective layer thickness and width of the heater line due to heat spreading effect.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.26.2-26.2
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• 2005

• 한국전자파학회논문지
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• 제19권5호
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• pp.580-586
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• 2008

위성 항법 보정 시스템(DGPS)을 설치하거나 운영하기 위해서는 시스템 커버리지에 대한 예측이 필요하다. 그러나 기존에 제안된 ITU-R 유효 대지 도전율을 이용하여 커버리지를 분석할 경우, 실제 측정된 결과와 오차가 많이 발생하기 때문에, 본 연구에서는 수정된 유효 대지 도전율 값을 이용하여 DGPS의 기준국 커버리지를 분석하였다. 수정된 유효 대지 도전율은 ITU-R 유효 대지 도전율을 기본으로 하였으며, 예측된 전계 강도와 측정된 전계 강도간의 오차를 최소화하기 위해 통계저인 방법을 이용하여 수정되었다. 다음으로 중파 대역 감쇠 모델과 수정된 유효 대지 도전율을 이용하여 현재 운용중인 DGPS의 서비스 영역을 예측하였으며, 다양한 분석을 통해 시스템의 안정성을 확인하였다.

• Advances in nano research
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• 제10권4호
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• pp.339-347
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Advances in nano research
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• 제10권5호
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• pp.471-479
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Structural Engineering and Mechanics
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• 제91권6호
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• pp.627-642
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• 2024

In the present work, the deformation and stresses induced in a functionally graded disk have been reported for different loading conditions. The governing differential equation is solved using the classical method namely Navier's method by considering thermal and mechanical boundary conditions at the surface of the disk. To simplify solving the second-order differential equation, a plane stress condition was assumed. Following validation using a one-dimensional steady-state heat condition problem, temperature variations were computed for constant heat generation and varying conductivity. The research aims to investigate both the individual and combined effects of rotation, gravity, and temperature with constant heat generation on a hollow disk operating under complex loading conditions. The results demonstrated a high degree of accuracy when compared with those in existing literature. Material properties, such as Young's modulus, density, conductivity, and thermal expansion coefficient, were modeled using a power law variation along the disk's radius by considering aluminum as a base material. The proposed analytical method is straightforward, providing valuable insights into the behavior of disks under various loading conditions. This method is particularly useful for researchers and industries in selecting appropriate loading conditions and grading parameters for engineering applications, including aerospace components, energy systems, and rotary machinery parts.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.514-519
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• 2006

To improve the mean-life and the reliability of power cable, we have investigated specific heat (Cp) and thermal conductivity of XLPE insulator and semiconducting materials in 154[kV] underground power transmission cable. Specimens were made of sheet form with the seven of specimens for measurement. Specific heat (Cp) and thermal conductivity were measured by DSC (Differential Scanning Calorimetry) and Nano Flash Diffusivity. Specific-heat measurement temperature ranges of XLPE insulator were from $20[^{\circ}C]\;to\;90[^{\circ}C]$, and the heating rate was $1[^{\circ}C/min]$. And the measurement temperatures of thermal conductivity were $25[^{\circ}C],\;55[^{\circ}C]\;and\;90[^{\circ}C]$. In case of semiconducting materials, the measurement temperature ranges of specific heat were from $20[^{\circ}C]\;to\;60[^{\circ}C]$, and the heating rate was $1[^{\circ}C/min]$. And the measurement temperatures of thermal conductivity were $25[^{\circ}C]\;and\;55[^{\circ}]C$. From these experimental results both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature. We could know that a small amount of CNT has a excellent thermal properties.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권11호
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• pp.477-482
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• 2005

We have investigated volume resistivity and thermal properties showed by changing the content of carbon black which is the component parts of semiconducting shield in underground power transmission cable. Specimens were made of sheet form with the nine of specimens for measurement. Volume resistivity of specimens was measured by volume resistivity meter after 10 minutes in the preheated oven of both 25$\pm$1[$^{\circ}C$] and 90$\pm$1[$^{\circ}C$]. And specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The measurement temperature ranges of specific heat using the BSC was from 20[$^{\circ}C$] to 60[$^{\circ}C$], and the heating rate was 1[$^{\circ}C$/min]. And the measurement temperatures of thermal conductivity using Nano Flash Diffusivity were both 25[$^{\circ}C$] and 55[$^{\circ}C$]. Volume resistivity was high according to an increment of the content of carbon black from these experimental results. And specific heat was decreased, while thermal conductivity was increased by an increment of the content of carbon black. And both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature.

• 공업화학
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• 제25권5호
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• pp.463-467
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• 2014

본 연구에서는 팽창흑연의 함량 변화를 달리하여 제조한 팽창흑연/에리스리톨 복합체의 열적거동에 관하여 고찰하였다. 팽창흑연이 도입된 팽창흑연/에리스리톨 복합체의 표면 및 구조특성은 scanning electron microscope (SEM), transmission electron microscope (TEM), 그리고 X-ray diffraction (XRD)를 이용하여 관찰하였으며, 열적특성은 differential scanning calorimetry (DSC)와 thermal conductivity (TC)를 이용하여 분석하였다. 실험 결과 팽창흑연의 함량이 증가함에 따라 팽창흑연/에리스리톨 복합체의 열전도도가 증가하였으며, 반면에 잠열은 팽창흑연의 존재 하에 약간 감소하였다. 결론적으로 팽창흑연은 상변이 물질의 높은 열 전달성능 및 열 저장능력을 향상시키는데 적합한 소재라 판단된다.