• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2620-2629
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• 2020

As an early stage in the development of a water calorimeter, this study established a computer simulation methodology for analyzing the thermal behavior of a water calorimeter based on radiation transport and energy deposition. As a result, this study developed a method wherein the energy deposition distribution, which is obtained by applying Monte Carlo methods in water calorimeters, is directly used as a heat source for the thermal analysis model. Based on the proposed method, heat transfer in a water vessel and the effect of thermistor self-heating were analyzed. Through an analysis of the water velocities with and without a water vessel, it was found that a water vessel can serve as a convection barrier. Furthermore, it was confirmed that when considering thermistor self-heating, the water temperature change at the thermistor location is 0.219 mK higher compared to that when the thermistor was not considered. Therefore, thermistor self-heating must be considered to analyze the thermal behavior of a water calorimeter more accurately.

• 센서학회지
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• 제20권5호
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• pp.329-335
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• 2011

We demonstrated that high-stability thermistors can be calibrated with an uncertainty less than 1 mK, if the error due to the heat conduction is minimized. We first investigated the effect of the self-heating of typical thermistor probes to see how accurate we need to determine the effect of self-heating. We, then, calibrated thermistors and fitted the results using various modeling equations. We found out that the heat conduction is an important factor in achieving the calibration uncertainty under 1 mK for thermistors when the diameter of the probe is as thick as 10 mm. Therefore, we controlled the room temperature within $0.5^{\circ}C$ to minimize the heat conduction error during the calibration. The calibration with an uncertainty below 1 mK was possible when the stabilization time for each calibration was long enough to obtain a good thermal equilibrium.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.97-100
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• 1989

Thermistor is the semiconducting material whose electrical resistance is varied with its self heating. In this paper, the improvement of resistance-temperature characteristics of NTC thermistor devices based on NiO was experimented. The specimens were prepared by mixing NiO and Mn$_2$O$_3$(1:1 mole %) and by addition of CuO(1 wt %, 2 wt %, 4 wt %). The specimens were compacted at the pressure of 1000 kg/$\textrm{cm}^2$ and sintered for 1 hour in air ambient at 120$0^{\circ}C$. Reducing CuO additions not only resistance-temperature characteristics, but also increased room temperature resistance.

• Macromolecular Research
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• 제10권6호
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• pp.345-358
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• 2002

The electrical conductivity during vulcanization process was measured as a function of time for the system of TiC loaded styrene-butadiene rubber (SBR) composites. The phenomenon of negative and positive temperature coefficients of conductivity and its conduction mechanism were also studied for the SBR polymeric composites. The current-voltage characteristics of the polymeric composites were non-linear in high voltage and showed a switching effect. The effects of temperature on the thermal conductivity and effective dielectric constant were measured. The measured parameters were found to be dependent on TiC concentration. The electromagnetic wave shielding (EMS) of the SBR-TiC polymeric composite was also examined. The SBR filled with TiC could be expected to be promising novel smart polymeric composites for self-electrical heating, temperature sensor, time delay switching, and electro-magnetic wave shielding effectiveness.

• Journal of Preventive Medicine and Public Health
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• 제6권1호
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• pp.65-70
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• 1973

The study in the fild of medical instrument has been out of the interest by any of the life scientist in Korea. Especially, the recent developments in the medical electromics are remarkable one. Authors planned this study to ascertain the possibility of setting up the thermister thermometer with available accessories of demestic prouducts including some specific foreign assembly parts. By proper use of the thermister as one of the wheatstone bridge, we could detect tile resistance variations due to the environmental temperature variace. The intensive care for the bridge circuit and compensation scheme was required. The calibration procedure adopted here makes it possible to read the current as the temperature. The temperature range was determined by the examination and construction of the graph of the resistance-temperature variation. The determination of electric current, available ambient-temperature, the reduction of excessive current and self-heating of the thermister were made. Renovation in response-velocity was under taken too. This electronic thermometer was designed and assembled by the circuitry developed in accordance with the maximum availability of domestic products with some foreign-made parts. The result of our experiment showed very stable function and proved to be the most promissing item in the actual application as long as the thermistor thermister is concerned.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1478-1480
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• 2003

본 논문에서는 PTC 서미스터를 이용해서 히터와 기판을 일체화한 가스센서용 자기발열기판을 개발하였다. $BaTiO_3$, $PbTiO_3$를 기초원료로 하여 $Nb_2O_5$를 첨가해 (Ba, Pb)$TiO_3$ PTC 소자를 제조한 결과 $Nb_2O_5$ 첨가량이 증가할수록 낮은 상온 비저항 값을 나타내었으며, 첨가량이 0.11mol.%${\sim}$0.13mol.% 범위일 때 가장 균일하고 치밀한 구조가 얻어짐을 알 수 있었다. 상온에서 비저항 값은 $1280^{\circ}C$에서 10분간 소결하였을 때 가장 작았고, 또한 $N_2$ 분위기에서 소결한 시료가 낮은 비저항 값을 나타내었다. 제작된 PTC 소자의 표면온도 측정결과, 단위면적($1mm^3$)당 소비전력은 약 $50^{\sim}60$ mW 정도로 되었으며, 이것은 기존의 가스센서에 사용되고 있는 히터와 비교해 1/3${\sim}$1/4배 정도 낮은 값이다.