• 한국전기전자재료학회논문지
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• 제30권1호
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• pp.17-22
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• 2017

Effects of pH value and deposition time on the electrical properties of (NMC) Ni-Mn-Cu-O and (NMCC) Ni-Mn-Cu-Co-O thin films were investigated. The NMC and NMCC films were prepared by spin spray method. The crystal structure and thickness of the annealed films were changed by the pH value and deposition time, respectively. A single phase of cubic spinel structure was confirmed for the annealed films deposited from solutions with pH 7.6. The resistivity of the annealed films was affected by the crystal structure and microstructure. The TCR (temperature coefficient of resistance) was dependent on the $Mn^{3+}/Mn^{4+}$. Typically, the resistivity of $70.5{\Omega}{\cdot}cm$ and TCR of -3.56%/K at room temperature were obtained for NMCC films deposited from solutions with pH 7.6 for 5 min, and annealed at $450^{\circ}C$ for 3 h.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.410-411
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• 2009

The multi-component ceramic proton conductor, $BaZr(Y)O_3-SiO_2-TiO_2-ZrO_2$ (BZY-STZ) and $LaPO_4-SiO_2-TiO_2-ZrO_2$ (LP-STZ), were synthesized by micro-emersion and sol-gel technique. The characterization of proton conductors were carried out using X-ray diffraction(XRD), thermogravimetric analysis(TGA), differential thermal analysis(DTA), impedance analysis. The proton conductors indicate the possibility of application for the intermediate temperature up to $700^{\circ}C$.

• 한국방재학회 논문집
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• 제10권3호
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• pp.119-131
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• 2010

가뭄은 인간이 극복하기 힘든 자연재해로서 가뭄지역의 경제를 어렵게 할 뿐 아니라 생태계까지 파괴하기 때문에 전 세계적으로 가장 두려워하는 관심 재해 중 하나이다. 따라서 본 연구에서는 대표적인 가뭄지수인 팔머가뭄지수와 범지구적 해수면 온도의 상관관계를 분석하였다. 먼저 팔머가뭄지수를 산정하여 과거 가뭄발생연도와 비교분석을 실시하였다. 비교분석을 결과 대부분의 과거 가뭄사상과 지수가 일치하는 것으로 분석되었다. 상관성 분석을 위해 팔머가뭄지수 산정을 위한 지수인 강수자료와 온도자료를 월평균강수량과 월평균온도 자료로 산정하여 군집분석을 실시하였다. 우리나라 기상청관할에 있는 61개 지점을 선정하여 월평균강우량과 월평균온도 자료로 군집분석결과 총 6개의 군집을 형성하는 것으로 분석되었다. 또한, 군집분석결과와 팔머가뭄지수의 주성분 분석을 실시하였다. 주성분 분석을 통해 전체 자료의 분산을 80% 이상 설명할 수 있는 14개의 시계열 자료를 추출하였다. 추출된 팔머가뭄지수의 주요 성분과 범지구적 해수면 온도와의 상관성 분석결과 팔머가뭄지수는 양의 상관관계가 음의 상관관계보다 큰 것으로 분석되었으며, 태평양에서 관측되는 해수면 온도와 통계적으로 유의한 상관관계를 갖는 해수면 온도 구역을 확인할 수 있었다. 이를 통해 해수면 온도를 이용하여 우리나라에 발생할 수 있는 가뭄의 예측 가능성을 제시하였다.

• 한국재료학회지
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• 제32권12호
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• pp.538-544
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• 2022

In existing ceramic mold manufacturing processes, inorganic binder systems (Si-Na, two-component system) are applied to ensure the effective firing strength of the ceramic mold and core. These inorganic binder systems makes it possible to manufacture a ceramic mold and core with high dimensional stability and effective strength. However, as in general sand casting processes, when molten metal is injected at room temperature, there is a limit to the production of thin or complex castings due to reduced fluidity caused by the rapid cooling of the molten metal. In addition, because sodium silicate generated through the vitrification reaction of the inorganic binder is converted into a liquid phase at a temperature of 1,000 ℃. or higher, it is somewhat difficult to manufacture parts through high-temperature casting. Therefore, in this study, a high-strength ceramic mold and core test piece with effective strength at high temperature was produced by applying a Si-Na-Ti three-component inorganic binder. The starting particles were coated with binary and ternary inorganic binders and mixed with an organic binder to prepare a molded body, and then heat-treated at 1,000/1,350/1,500 ℃ to prepare a fired body. In the sample where the two-component inorganic binder was applied, the glass was liquefied at a temperature of 1,000 ℃ or higher, and the strength decreased. However, the firing strength of the ceramic mold sample containing the three-component inorganic binder was improved, and it was confirmed that it was possible to manufacture a ceramic mold and core via high temperature casting.

• 한국정보통신학회논문지
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• 제14권12호
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• pp.2609-2614
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• 2010

본 논문에서는 온도센서를 이용한 온도보상회로를 구현하였으며, 이를 이용하여 전력증폭기의 동작 온도범위인 $-30^{\circ}C{\sim}60^{\circ}C$에서 전력증폭기의 혼변조 규격을 만족할 수 있도록 하였다. 온도보상회로의 출력이 온도에 따라 170mV정도 변화하도록 하여 출력이 3W인 증폭기의 TR 게이트에 인가한 결과, $-30^{\circ}C{\sim}60^{\circ}C$에서 우측 3차 혼변조 성분이 -18.5~-26dBm, 좌측 3차 혼변조 성분이 -18.5~-35dBm으로 변화하였으며, 5차 혼변조 성분은 좌 우측 모두 -24~-26dBm으로 규격인 -17dBm이하라는 전력증폭기의 혼변조 성분 규격을 만족하는 것을 확인할 수 있었다.

• 자원ㆍ환경경제연구
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• 제29권4호
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• pp.419-442
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• 2020

우리나라 도시가스 수요는 난방수요에 기인한 뚜렷한 동고하저의 계절성을 보이며, 기온에 따른 민감도는 시간에 따라 변화하는 것으로 나타났다. 본 연구에서는 시간에 따라 변화하는 계절성을 효과적으로 모형하기 위해서 시간변동 기온반응함수 개념을 도입하여 이를 해당 일의 기온분포로 적분하여 기온에 따른 수요변동을 추정한다. 또한 기상청에서 발표하는 향후 10일의 도시별 기온 예측치를 체계적으로 반영하여 도시가스 수요를 예측하는 방법론을 개발하였다. 평년기온분포를 사용한 것에 비해서 함수적 방법론을 이용하여 기상청의 기온 예측치를 기온분포예측치로 변환하여 예측했을 때 기온분포의 예측 오차율은 2배, 도시가스 수요의 예측 오차는 5배 가까이 감소하는 것을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.630-633
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• 2004

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).

• 한국화재소방학회논문지
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• 제10권2호
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• pp.28-39
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• 1996

A recently developed electro-thermal simulation methodology is used to analyze the behavior of a PWM(Pulse-Width-Modulated) voltage source inverter which uses IGBT(Insulated Gate Bipolar Transistor) as the switching devices. In the electro-thermal network simulation methdology, the simulator solves for the temperature distribution within the power semiconductor devices(IGBT electro-thermal model), control logic circuitry, the IGBT gate drivers, the thermal network component models for the power silicon chips, package, and heat sinks as well as the current and voltage within the electrical network. The thermal network describes the flow of heat form the chip surface through the package and heat sink and thus determines the evolution of the chip surface temperature used by the power semiconductor device models. The thermal component model for the device silicon chip, packages, and heat sink are developed by discretizing the nonlinear heat diffusion equation and are represented in component from so that the thermal component models for various package and heat sink can be readily connected to on another to form the thermal network.

• Steel and Composite Structures
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• 제38권2호
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• pp.141-150
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• 2021

In the present paper we have investigated the Stoneley wave propagation at the interface of two dissimilar homogeneous nonlocal magneto-thermoelastic media under the effect of hall current applied to multi-dual-phase lag heat transfer. The secular equations of Stoneley waves have been derived by using appropriate boundary conditions. The wave characteristics such as attenuation coefficients, temperature distribution and phase velocity are computed and have been depicted graphically. Effect of nonlocal parameter and hall effect are studied on the attenuation coefficient, phase velocity, temperature distribution change, stress component and displacement component. Also, some particular cases have been discussed from the present study.

• Elastomers and Composites
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• 제57권3호
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• pp.100-106
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• 2022

Waterborne polyurethane-acrylate(WPUA) dispersions were prepared by surfactant-free emulsion polymerization in a two-step process. In the first step, polytetrahydrofuran, isophorone diisocyanate, dimethylol proponic acid, and 2-hydroxyethyl methacrylate were used to synthesize a vinyl-terminated polyurethane prepolymer. In the second step, styrene, methyl methacrylate, butyl acrylate, and different multi-functional crosslinkers were copolymerized. 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate were used as the crosslinkers, and their effect on the mechanical and thermal properties of WPUA was investigated. Overall, as the number of functional groups of the cross-linker increased, the gel fraction improved to 79.26%, the particle size increased from 75.9 nm to 148.7 nm, and the tensile strength was improved from 5.86 MPa to 12.40 MPa. In thermal properties, the glass transition temperature and decomposition temperature increased by 9.9℃ and 18℃, respectively. The chemical structures of the WPUA dispersions were characterized by Fourier-transform infrared spectroscopy. The synthesized WPUA has high potential for applications such as coatings, leather coatings, adhesives, and wood finishing.