• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.323-327
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• 2024

The low-temperature coefficient of resistance (TCR) is a crucial factor in the development of space-grade resistors for temperature stability. Consequently, extensive research is underway to achieve zero TCR. In this study, resistors were deposited by co-sputtering nickel-chromium-based composite compositions, metals showing positive TCR, with SiO₂, introducing negative TCR components. It was observed that achieving zero TCR is feasible by adjusting the proportion of negative TCR components in the deposited thin film resistors within certain compositions. Additionally, the correlation between TCR and deposition conditions, such as sputtering power, Ar pressure, and surface roughness, was investigated. We anticipate that these findings will contribute to the study of resistors with very low TCR, thereby enhancing the reliability of space-level resistors operating under high temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.17-20
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• 1994

PTCRl(positive temperature coefficient of resistivity) thermistors in the thin file BaTiO$_3$ system were deposited by radio frequency (13.56 MHz) and dc radio frequency (13.56MHz) and dc magnerton sputter equipment. R-T(resistivity -temperature) properties was investigated as a function of substrate and the temperature variation. The specimens make a comperison between the thin films and the bulk in the resistivity variation. Substrate temperature. deposition time. and forward power are deposited at the 400$^{\circ}C$, 10 hours, and 210 watt. respectively. The aim of this work is to obtain lower than bulk specimen resistivity in thin films BaTiO$_3$ system thermistor by RF/DC magnetron sputter equipment.

• Journal of Astronomy and Space Sciences
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• v.27 no.3
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• pp.231-238
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• 2010

We analyzed global positioning system (GPS)-derived precipitable water vapor (PWV) trends of the Korea Astronomy and Space Science Institute 5 stations (Seoul, Daejeon, Mokpo, Milyang, Sokcho) where Korea Meteorological Administration meteorological data can be obtained at the same place. In the least squares analysis, the GPS PWV time series showed consistent positive trends (0.11 mm/year) over South Korea from 2000 to 2009. The annual increase of GPS PWV was comparable with the 0.17 mm/year and 0.02 mm/year from the National Center for Atmospheric Research Earth Observing Laboratory and Atmospheric InfraRed Sounder, respectively. For seasonal analysis, the increasing tendency was found by 0.05 mm/year, 0.16 mm/year, 0.04 mm/year in spring (March-May), summer (June-August) and winter (December-February), respectively. However, a negative trend (-0.14 mm/year) was seen in autumn (September-November). We examined the relationship between GPS PWV and temperature which is the one of the climatic elements. Two elements trends increased during the same period and the correlation coefficient was about 0.8. Also, we found the temperature rise has increased more GPS PWV and observed a stronger positive trend in summer than in winter. This is characterized by hot humid summer and cold dry winter of Korea climate and depending on the amount of water vapor the air contains at a certain temperature. In addition, it is assumed that GPS PWV positive trend is caused by increasing amount of saturated water vapor due to temperature rise in the Korean Peninsula. In the future, we plan to verify GPS PWV effectiveness as a tool to monitor changes in precipitable water through cause analysis of seasonal trends and indepth/long-term comparative analysis between GPS PWV and other climatic elements.

• Journal of Conservation Science
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• v.34 no.5
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• pp.387-396
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• 2018

Exposure to the natural environment can cause damage to domestic wooden cultural assets, such as temples. Deterioration is accelerated by biological damage and various environmental factors. In this study, meteorological factors were monitored by equipment installed at Beopjusa temple of Boeun province and Seonamsa temple of Suncheon province. A statistical model was applied to these data to predict the meteorological factors and to compare the predictive performance of each meteorological factor. The resulting correlation coefficient between air and dew point temperatures was highest, at 0.95, while the correlation coefficient for relative humidity had a moderate value(0.65) at both the Beopjusa and Seonamsa temples. Thus, a general linear model was found to be suitable for predicting air and dew point temperatures. An analysis of correlation between meteorological factors showed that there was strong positive correlation between air temperature and dew point temperature, and between solar radiation and evaporation at both sites. There was a weak positive correlation between air temperature and evaporation at Beopjusa temple. Wind speed was negatively correlated with both air temperature and relative humidity at Seonamsa temple. The wind speed at this location is higher than average in winter and lower than average in summer, and it was hypothesized that the low wind speed plays a role in reducing water evaporation in summer, when both air temperature and relative humidity are high. As a result, damage to the wooden buildings of Seonamsa temple is accelerated.

• Korean Journal of Environment and Ecology
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• v.18 no.1
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• pp.53-60
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• 2004

This study was carried out to investigate the effect of green area in apartment complexes to variation of temperature. The inside temperature of each site was estimated by analyzing Landsat ETM＋ image data. The factors on variation of temperature were landcover type, building density, and Normalised Difference Vegetation Index(NDVI). The results of correlation between inside temperature of apartment complex and land cover type showed that the green area ratio had negative(－) correlation and impermeable pavement ratio had positive(＋) correlation. Building-to-land ratio was not significant with inside temperature. A coefficient of correlation between the temperature value and the value of permeable pavement ratio added up green area ratio was higher than a coefficient of correlation between the temperature value and the value of permeable pavement ratio added up impermeable pavement ratio. Thus we may define that permeable pavement area decrease urban temperature with green area in apartment complex. Floor area ratio had no significant correlation with inside temperature. Inside temperature was decreased as the NDVI was increased. To establish the temperature distribution model in a development apartment complex, As the result of regression analysis between inside temperature as dependent variable and permeable pave ratio+green area ratio, green area ratio, building-to-land ratio and NDIT as independent variables, only permeable pavement ratio added up green area ratio of the independent variables was accepted fur regression equation in both two seasons and adjusted coefficient of determination was 41.4 on September, 2000 and 40.4 on June,2001.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.249-252
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• 1999

전도성 충진제가 포함된 결정성 고분자내에 대전류가 흐르게 될 경우 Joule 효과로 소재자체의 발열현상이 발생하며 온도가 증가함에 따라 고분자의 용융점 부근에서 급격한 열팽창으로 인하여 고분자 내에 분포되어 있던 전도성 충진재 입자사이의 간격이 증가하게 되며 전자들의 흐름이 방해를 받게 된다. 이에 따라 전기저항이 커져 전류의 흐름이 감소되는 철상이 발생하며 이를 PTC(Positive Temperature Coefficient)라 하고 온도 증감에 따른 전도성 충진제 간의 electron tunnelling과 고분자의 결정변화에 의해 민감한 전기저항변화 특성을 나타낸다. (중략)

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.104-106
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• 1995

A curious resistivity anomaly in high curie point barium-lead-titanate materials with positive temerature coefficient of resistivity (PTCR) has been observed just below the curie point, besides the normal PTCR anomaly. The additional resistivity anomaly was observed in the resistivity-temperature characteristics.

• Journal of Photoscience
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• v.11 no.1
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• pp.11-17
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• 2004

Fluorescence quenching of l,4-bis [2-(2-methylphenyl) ethenyl]-benzene (Bis-MSB) by carbon tetrachloride in five different solvents namely hexane, cyclohexane, toluene, benzene and dioxane has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern-Volmer plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the Ground state complex and Sphere of action static quenching models. Using these models various rate parameters have been determined. The magnitudes of these parameters imply that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation in the Stem-Volmer plots is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check whether these bimolecular reactions as diffusion limited and to estimate independently distance parameter R' and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R'and D with the values of the encounter distance R and the mutual diffusion coefficient D determined using the Edwardis empirical relation and Stokes-Einstein relation.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1545-1547
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• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta$-Sic-$TiB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_3$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_{5}Y_{3}O_{12}$). The relative density and the mechanical properties of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents because YAG of reaction between $Al_{2}O_3$ and $Y_{2}O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism. the fracture toughness showed 7.1MPa${\cdot}m^{1/2}$. For composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature The electrical resistivity and the resistance temperature coefficient respectively showed the lowest of 6.0${\sim}10^{-4}{\Omega}{\cdot}$ cm and 3.1${\times}10^{-3}/^{\circ}C$ for composite added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of 25$^{\circ}C$ to 700$^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.6
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• pp.263-270
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• 2001

The mechanical and electrical properties of the hot-pressed and annealed ${\beta}-SiC-TiB_2$,/TEX> electroconductive ceramic composites were investigated as function as functions of the liquid forming additives of $Al_2O_3+Y_2O_3$. The result of phase analysis of composites by XRD revealed ${\alpha}$-SiC(6H), $TiB_2$,/TEX>, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density and the mechanical properties of composites were increased with increasing $Al_2O_3+Y_2O_3$ contents in pressureless annealing method because YAG of reaction between $Al_2O_3$ was increased. The flexural strength showed the highest value of 458.9 MPa for composites added with 4 wt% $Al_2O_3+Y_2O_3$ additives in pressed annealing method at room temperature. Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism, the fracture toughness showed 7.1 MPa ${\cdot}\;m^{1/2}$ for composites added with 12 wt% $Al_2O_3+Y_2O_3$ additives in pressureless annealing method at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest value of $6.0{\times}10^{-4}\;{\Omega}\;{\cdot}\;cm(25\'^{\circ}C}$ and $3.0{\times}10^{-3}/^{\circ}C$ for composite added with 12 wt% $Al_2O_3+Y_2O_3$ additives in pressureless annealing method at room temperature, respectively. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature ranges from 25 $^{\circ}C$ to 700 $^{\circ}C$.