• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.409-410
• /
• 2002

In order to measure the oil-film pressure in sliding surface of machinery, we have developed a piezo-resistive type thin-film pressure sensor. To reduce the measurement error due to temperature and strain, the constituent of the pressure sensitive alloy was optimized and a new sensor shape was devised. In this study, we present the measurement results of the oil-film pressure distribution in engine connecting rod big-end bearing and piston pin- bosses with 3 different pin-boss shapes using the newly developed thin-film pressure sensor.

• 한국수소및신에너지학회논문집
• /
• 제31권5호
• /
• pp.489-497
• /
• 2020

The Li-ion battery is considered to be one of the potential power sources for electric vehicles. In fact, the efficiency, reliability, and cycle life of Li-ion batteries are highly influenced by their thermal conditions. Therefore, a novel thermal management system is highly required to simultaneously achieve high performance and long life of the battery pack. Basically, thermal modeling is a key issue for the novel thermal management of Li-ion battery systems. In this paper, as a basic study for battery thermal modeling, temperature distributions inside the simple Li-ion battery pack (comprises of nine 18650 Li-ion batteries) under a 1C discharging condition were investigated using measurement and computational fluid dynamics (CFD) simulation approaches. The heat flux boundary conditions of battery cells for the CFD thermal analysis of battery pack were provided by the measurement of single battery cell temperature. The temperature distribution inside the battery pack were compared at six monitoring locations. Results show that the accurate estimation of heat flux at the surface of single cylindrical battery is paramount to the prediction of temperature distributions inside the Li-ion battery under various discharging conditions (C-rates). It is considered that the research approach for the estimation of temperature distribution used in this study can be used as a basic tool to understand the thermal behavior of Li-ion battery pack for the construction of effective battery thermal management systems.

• 대한원격탐사학회지
• /
• 제31권6호
• /
• pp.583-598
• /
• 2015

본 연구에서는 천리안위성 기반의 지표면 열적 특성 감시 및 기상현상 탐지에 이용할 수 있는 배경 온도장을 산출하고 지상관측자료 및 지리정보와 비교하여 정확도를 검증하였다. 배경온도장은 밝기온도를 선택하였으며 2012년 자료를 이용하여 월별로 매 시간대에 대해 산출되었다. 밝기온도 자료에서 청천화소와 구름화소를 구별하기 위해 천리안 구름탐지를 사용하였고, 천리안 구름탐지의 입력자료로 사용된 수치모델자료와 공간 균질성 검사 부분에서 구름 오탐지현상을 발견하였다. 과다하게 구름으로 오탐지된 화소는 통계적인 방법에 기반한 구름화소 복원을 통해 해결하였다. 산출된 밝기온도 배경장은 지상관측 기온과 0.95의 상관관계를 보였으며 0.66 K의 편향과 4.88 K의 평균 제곱근 오차를 보였다. 밝기온도 배경장과 고도는 시간대와 계절에 따라 변동성을 보이는 음의 상관관계를 보였다. 녹지와의 상관관계는 기온이 높은 계절 및 주간에 높게 나타났으며, 상관관계의 시간에 따른 변화가 관측되었다. 이러한 이유로 지표면온도 산출 시 시간에 따른 방출률을 별도로 구성해야 할 필요성이 제기되었다.

• 한국전기전자재료학회논문지
• /
• 제20권2호
• /
• pp.188-193
• /
• 2007

Tracking and erosion of Poly Methyl Methacrylate (PMMA) and the suppression mechanism of alumina trihydrate were investigated in the present study The conventional testing as IEC-60587 is widely used in surface aging measurement of outdoor insulator those testing can carry out very short time for Lab testing. Also IEC-60587 testing is able to offer the standard judgement of relative degradation level of outdoor HV system. Therefore it is very useful method compare to previous conventional tracking testing method, But surface discharges(SD) have very complex characteristics of discharge pattern so it is required estimation research to development of precise analysis method. In recent, the study of IRR-Camera is carrying out discover of temperature of power equipment through condition diagnosis and system development of degradation diagnosis. In this paper, SD occurred from IEC-60587 is measured with the surface temperature of weibull distribution in real time, the degradation grade of SD is analyzed through produced patterns in IEC-60587 using Infrared Radiation(IRR) camera.

• Nuclear Engineering and Technology
• /
• 제52권10호
• /
• pp.2299-2305
• /
• 2020

Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr₂O₃ formed on the outer surface of the Cr-Al alloy, and a thin Al₂O₃ layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr₂Zr.

• 한국재료학회지
• /
• 제29권5호
• /
• pp.336-341
• /
• 2019

The gas adsorption isotherm requires accurate measurement for the analysis of porous materials and is used as an index of surface area, pore distribution, and adsorption amount of gas. Basically, adsorption isotherms of porous materials are measured conventionally at 77K and 87K using liquid nitrogen and liquid argon. The cold volume calibration in this conventional method is done simply by splitting a sample cell into two zones (cold and warm volumes) by controlling the level sensor in a Dewar filled with liquid nitrogen or argon. As a result, BET measurement for textural properties is mainly limited to liquefied gases (i.e. $N_2$ or Ar) at atmospheric pressure. In order to independently investigate other gases (e.g. hydrogen isotopes) at cryogenic temperature, a novel temperature control system in the sample cell is required, and consequently cold volume calibration at various temperatures becomes more important. In this study, a cryocooler system is installed in a commercially available BET device to control the sample cell temperature, and the automated cold volume calibration method of temperature variation is introduced. This developed calibration method presents a reliable and reproducible method of cryogenic measurement for hydrogen isotope separation in porous materials, and also provides large flexibility for evaluating various other gases at various temperature.

• 펄프종이기술
• /
• 제30권3호
• /
• pp.74-83
• /
• 1998

The phenomenon of decrease in sizing efficiency when the stock temperature is increased is well recognized as summer sizing, and this is believed to be caused by uneven distribution of sizing agents on paper surface most often incurred by coagulation of sizing agents. When unevenly sized paper is used as coating base stock, nonuniform consolidation of the coating layer may result, which, in turn, causes uneven distribution of binder on coating surface. This causes nonuniform ink absorption to produce print mottle. In this study the effects of simple or polymeric electrolytes, storage temperature and time on the coagulation of cationic dispersed rosin size were investigated using a turbidity measurement method which was verified to correlate well with the particle size of rosin emulsion or its coagulates. Handsheets sized with rosin dispersions coagulated under various conditions were prepared and their sizing degree and coated paper properties including gloss and ink density were examined. The relationship between the sizing nonuniformity of coated papers and its ink absorption property was evaluated. Turbidity of rosin emulsion increased as the storage temperature and time were increased. Addition of simple or polymeric electrolytes caused reduction in $zeta$ -potential of the rosin dispersion and accelerated the coagulation tendency substantially. Reversion of the $zeta$ -potential of rosin dispersion, however, did not occur when coagulation was induced with simple electrolytes. On the other hand, addition of an anionic polyelectrolyte reversed the $zeta$ -potential of the flocculated rosin dispersion. This indicated that electrical double layer compaction and bridging flocculation were coagulation mechanisms for simple and polymeric electrolytes, respectively. Sizing degree decreased as coagulation of rosin was increased. Paper gloss, ink gloss and ink density were increased when sizing degree of base stock was increased most probably due to prevention of base paper swelling and increased binder migration to coating surface. This suggested that uneven printing ink density occurred when uneven sizing development was induced by coagulation of rosin particles.

• 한국정밀공학회지
• /
• 제14권4호
• /
• pp.72-77
• /
• 1997

In the temperature analysis of hot metal forming process, the heat transfer conditions between the work-piece and the tool have improtant influences upon the temperature distribution. The accuracy of thermal analysis depends on the proper description of boundary conditions including heat transfer. At the contact surface of two materials with different temperatures, this requires the knowledge of the overall heat transfer coefficient. In order to determine the overall heat transfer coefficient, a technique is developed. The technique involves temperature measurement by using thermocouples during hot upsetting operations and finite element computation. The overall heat transfer coefficient is determined using a non-linear optimization technique.

• 한국측량학회지
• /
• 제31권2호
• /
• pp.143-150
• /
• 2013

최근 기후 온난화, 오존층 파괴, 열대림의 감소, 사막화 등의 환경문제가 이미 한 국가 문제를 넘어 범세계적인 지구환경문제로 대두되면서 이를 해결하기 위한 국제적인 관심과 노력이 다양하게 진행되어 왔다. 본 연구에서는 원격탐사 기법을 이용하여 도시의 녹지증가를 정량적으로 산출하고, 온도 추출을 통해 도시의 온도변화를 파악하고자 하였다. 2002년 5월과 2009년 5월 Landsat TM영상을 이용하여 연구대상지의 녹지 면적변화와 열변화를 분석하였으며, 도심의 지표면 온도를 추출하기 위해 Landsat TM 열적외선 영역센서인 Band 6의 분광밝기정도를 이용하여 표면온도분포를 산출하였다. 연구결과, 도심지 녹지의 면적이 $2.97km^2$ 증가하였으며, 도시의 지표온도가 약$0.6^{\circ}C{\sim}0.8^{\circ}C$ 낮아졌음을 제시하였다. 향후 원격탐사 및 실측자료를 바탕으로 도심 온도변화에 대한 추가적인 연구가 이루어진다면 도시환경문제 해결에 크게 기여할 것이다.

• 한국가시화정보학회지
• /
• 제7권2호
• /
• pp.17-21
• /
• 2010

This paper presents the fabrication and performance measurement of a temperature sensor array on a flexible substrate attachable to a curved surface using MEMS technology. Specifically, the fabrication uses the well-developed printed circuit board fabrication technology for complex electrode definition. The temperature sensor array are lifted off with a $10{\times}10$ matrix in a $50\;mm{\times}50\;mm$ to visualize temperature distribution. Copper is used as temperature sensing material to measure the change in resistances with temperature increase. In a thermal oven with temperature control, the temperature sensor array is Characterized. The constant slope of resistance change is obtained and temperature distribution is measured from the relationship between resistance and temperature.