• Title, Summary, Keyword: 비직선 지수

Search Result 83, Processing Time 0.034 seconds

Effect of Sintering Time on Degradation Characteristics of ZPCCY-Based Varistors (ZPCCY계 바리스터의 열화특성에 미치는 소결시간의 영향)

  • 남춘우;박종아
    • Journal of the Korean Ceramic Society
    • /
    • v.41 no.6
    • /
    • pp.464-470
    • /
    • 2004
  • The electrical stability of ZPCCY-based varistors composing of ZnO-Pr$_{6}$O$_{11}$-CoO-C $r_2$ $O_3$- $Y_2$ $O_3$ ceramics were investigated in various DC accelerated aging stress with sintering times. Sintering time greatly affected electrical properties and stability. Sintering time decreased nonlinear exponent in the range of 51.2∼23.8 and increased leakage current in the range of 1.3∼5.6 ${\mu}$A. The varistor sintered for 1 h exhibited high nonlinearity, whereas relatively low stability. On the contrary, the varistor sintered for 3 h exhibited low nonlinearity, whereas relatively high stability. But the varistor sintered for 2 h exhibited not only good nonlinearity, with nonlinear exponent of 38.6 and leakage current of 3.6 ${\mu}$A but also high stability, in which the variation rates of varistor voltage, nonlinear exponent, leakage current, and dissipation factor are -0.80%, -1.81 %, +74.4%, and +0.88%, respectively.

Speed Index of Logging Truck in Forest Road (임도에서 운재차량의 속도지수)

  • Lee, Joon Woo
    • Korean Journal of Agricultural Science
    • /
    • v.23 no.1
    • /
    • pp.138-149
    • /
    • 1996
  • This study was aimed at predicting to running speed related to alignment factors of forest road, and recommending the improvement method of forest road construction using the running speed of vehicles. For these purposes, this study proceeds to select forest roads after reviewing the planning papers and maps, to measure the road alignment factors such as longitudinal gradient, width of roadway, radius of curve, length of curve, superelevation, and conditions of road surface on the subject forest road. It was found that the average running speed of logging truck showed lower value than that of the expected speed of 'Forest Road Construction Regulations and Rules', and the average running speed of loaded truck showed 70-85% of the speed of empty truck. According to the road conditions, speed index (reductive ratio of running speed) was also calculated with respect to radius of curve, longitudinal dradient. The results of the study on the running speed of vehicle subject to the alignment of forest roads make it possible for one to judge the quality of the existed and to be constructed forest roads, to select the structure of forest road to improve the running speed of vehicle on forest road.

  • PDF

Electrical and Dielectric Properties of Zn-Pr-Co-Cr-Dy Oxides-based Varistors (Zn-Pr-Co-Cr-Dy 산화물계 바리스터의 전기적, 유전적 특성)

  • 남춘우;박종아;김명준;류정선
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.10
    • /
    • pp.943-948
    • /
    • 2003
  • The microstructure and electrical characteristics of Zn-Pr-Co-Cr-Dy oxides-based varistors were investigated with Dy$_2$ $O_3$ content in the range of 0.0∼2.0 ㏖%. As Dy$_2$ $O_3$ content is increased, the average grain size was decreased in the range of 18.2∼4.6 $\mu\textrm{m}$ and the ceramic density was decreased in the range of 5.49∼4.64 g/㎤. The incorporation of Dy$_2$ $O_3$ markedly enhanced the nonlinear properties of varistors more than 9 times in nonlinear exponent, compared with the varistor without Dy$_2$ $O_3$ The varistor with 0.5∼1.0 ㏖% Dy$_2$ $O_3$ exhibited the high nonlinearity, in which the nonlinear exponent is above 55 and the leakage current is below 1.0 ${\mu}\textrm{A}$. The donor concentration and the density of interface states were decreased in the range of (4.66∼0.25)${\times}$10$\^$18//㎤ and (5.70∼1.39)${\times}$10$\^$12//$\textrm{cm}^2$, respectively, with increasing Dy$_2$ $O_3$ content. The minimum dielectric dissipation factor of 0.0023 was obtained for 0.5 ㏖% Dy$_2$ $O_3$, but further addition of Dy$_2$ $O_3$ increased it.

Linear Solvation Energy Comparison Study in Normal Phase Liquid Chromatography Ⅰ (정상 액체크로마토그래피에서의 선형 용매화에너지 비교법 연구 Ⅰ)

  • Choe, Jang Deok;Jeong, Won Jo
    • Journal of the Korean Chemical Society
    • /
    • v.38 no.3
    • /
    • pp.221-223
    • /
    • 1994
  • We tried to apply the linear solvation energy comparison method to solute retention in normal phase liquid chromatography. Correlation coefficients of regression of lnk' collected in a fixed eluent against solute polarity indices have proven to be lower than those obtained from reversed phase liquid chromatography data. This event can be attributed to complexity of solute retention process in normal phase liquid chromatography. We concluded from the regression results that each specific polarity of the stationary phase is greater than that of the mobile phase and that the difference in each polarity between the stationary phase and the mobile phase decreases as the volume fraction(${\phi}$) of the more polar solvent in the mobile phase increases. Correlations of lnk' of a single solute against solvent polarity indices have proven to be meaningless owing to covariance among the solvent polarity indices. Instead, a good linear relationship between lnk' and solvent ${\pi}^*$ was observed, and its linearity is better than that between lnk' and ${\phi}$.

  • PDF

Fading characteristics of 2.4GHz band Wireless image signal for the Various Subway Tunnel Structures (지하철 터널 형태에 따른 2.4GHz 대역 무선영상 신호의 페이딩 특성)

  • Song, Ki-Hong
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.12 no.2
    • /
    • pp.223-230
    • /
    • 2008
  • This paper deals with the measurements of wireless image signal in subway tunnels at 2.45GHz. Measurements have been conducted in 3 subway stations with different types; a straight tunnel and two curved tunnels. As a analysis result for the measured data, we found that the signal level inside straight tunnel by the strong multipath waves fluctuate deeply compared to the curved tunnel. The path loss exponent for the Shin-hung station with the straight tunnel is 2.5, those for the Pan-am and Dae-dong station with curved tunnels are 1.6 and 1.9, respectively. The fade depth and width at 50% point became relatively serious at Shin-hung station, the level crossing rate inside the Pan-am station is larger than the other stations. Therefore, it can be concluded that the fading phenomena affect to the signal performance generate seriously at straight tunnel compared to the curved tunnel.

Electrical and Dielectric Characteristics of Zn-Pr-Co-Er-M(M=Ni, Mg, Cr) Oxides-Based Varistors (Zn-Pr-Co-Er-M(M=Ni, Mg, Cr)산화물계 바리스터의 전기적, 유전적 특성)

  • 남춘우;김명준
    • Journal of the Korean Ceramic Society
    • /
    • v.41 no.8
    • /
    • pp.605-609
    • /
    • 2004
  • The microstructure, electrical and dielectric characteristics of ZnO varistors were investigated at various metal oxide (NiO, MgO, and Cr$_2$O$_3$) additives. The average grain size was increased with addition of NiO while that was decreased with addition of Cr$_2$O$_3$-Thereby, the varistor voltage was higher in Cr$_2$O$_3$-added composition. Among varistors, the varistor added with Cr$_2$O$_3$ exhibited the highest nonlinearity, with 40.5 in the nonlinear exponent and 2.7 ${\mu}$A in the leakage current and its dielectric dissipation factor was relatively low value of 0.0589.

Electrical Stability of Zn-Pr-Co-Cr-Dy Oxides-based Varistor Ceramics (Zn-Pr-Co-Cr-Dy 산화물계 바리스터 세라믹스의 전기적 안정성)

  • 남춘우;박종아;김명준;류정선
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.11
    • /
    • pp.1067-1072
    • /
    • 2003
  • The electrical stability of the varistor ceramics composed of Zn-Pr-Co-Cr-Dy oxides-based varistors was investigated at 0.0∼2.0 mol% Dy$_2$O$_3$ content under DC accelerated aging stress. The ceramic density was increased up to 0.5 mol% Dy$_2$O$_3$ whereas further addition of Dy$_2$O$_3$ decreased sintered ceramic density. The density sailently affected the stability due to the variation of conduction path. The nonlinearity of varistor ceramics was greatly improved above 45 in the nonlinear exponent and below nearly 1.0 ${\mu}$A by incorporating Dy$_2$O$_3$. Under 0.95 V$\_$1mA/150$^{\circ}C$/24 h stress state, the varistor ceramics doped with 0.5 mol% Dy$_2$O$_3$ exhibited the highest electrical stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current were -0.9%, -14.4%, and +483.3%, respectively. The variation rates of relative permittivity and dissipation factor were +7.1% and +315.4%, respectively. The varistors with further addition of Dy$_2$O$_3$ exhibited very unstable state resulting in the thermal runaway due to low density.

Determination of Polarity Scales of Mixed Solvents for Normal Phase Liquid Chromatography (정상 액체 크로마토그래피에 사용되는 혼합용매들의 극성도 지수 결정에 관한 연구)

  • Won Jo Cheong;In Ki Kim;Byung Bae Park
    • Journal of the Korean Chemical Society
    • /
    • v.37 no.12
    • /
    • pp.1025-1034
    • /
    • 1993
  • We have measured ${\pi}^*$, $\alpha$ and $\beta$ polarity parameters of 2-propanol / hexane and ethyl acetate / hexane mixed solvents over the entire range of composition. For the ethyl acetate / hexane system, only ${\pi}^*$ and $\beta$ were measured since $\alpha$ of these mixed solvents are defined zero. We have corrected the measured polarity parameters to obtain consistent data with the existing literature data assuming a good linear correlation between the measured and the true values. The variation patterns are consistent with the expected trends based on the chemistry of the solvent components. The general trends of the two solvent systems are summarized as follows. ${\pi}^*$ merely increases as the content of the more polar solvent increases while $\alpha$ and $\beta$ increase with the increase of the content of the more polar solvent, then decrease upon continuing addition of the more polar solvent.

  • PDF

Degradation characteristics of Praseodymium-based ZnO Varistor (프라세오디윰계 산화아연 바리스터의 노화특성)

  • 이외천;박춘현;남춘우
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.343-346
    • /
    • 1998
  • Degradation characteristics of the Pr-based ZnO varistor with $Y_2O_3$content (0.0-4.0 mol!%j were investigated. It was appeared that the variation of the J-E characteristics in the reverse direction before and after the applied stress with increasing $Y_2O_3$ content was larger than that of the forward direction but the variation was extrernly small. For all varistor, the leakage current with the stress time during the applied stress somewhat increased initialy but afterthat was almost constant or slightly decreased. The overall varistor voltage and nonlinear coefficient were less than 5%. Especially, in the case of Pr-based ZnO varistor containing 2.0 mol% to 4.0 mol% $Y_2O_3$, the variation of breakdown voltage and nonlinear coefficient was less than 1% and 5%. respectively. As a result, they showed good stability.

  • PDF

Microstructure and Conduction Characteristics of Bismuth-Based Zinc Oxide Varistors with $Y_2O_3$Additive ($Y_2O_3$가 첨가된 비스무스계 산화아연 바리스터의 미세구조 및 전도특성)

  • 박춘현;남춘우
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.281-285
    • /
    • 1998
  • The microstructure and conduction characteristics of ZnO varistor fabricated in the range of 0.0 ~ 4.0mol% $Y_20_3$ were investigated. With increasing$Y_20_3$ content, distribution of spinel phase decreased, whereas Y-rich phase segregated to the nodal point increased, as a result, the average grain size decreased in the range of $20.0 ~ 4.8{\mu}m$. $Y_20_3$ content showing relatively good conduction characteristics was l.Omol%, then nonlinear exponent and leakage current was 55.3, 0.66mA.respectively.

  • PDF