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류주현 한국 지리·환경 교육학회 1999 한국지리환경교육학회지 Vol.7 No.1
The use of color for representing geographic data on maps raises many questions. This study addresses questions about which color ensures accurate map reading and which color scheme is suitable for a specific geographic data. Two internal and external experiments and a review of previous color research have been conducted to establish and evaluate criteria for selecting colors to be used to represent geographic data. As a result, color use has proved to be effective in increasing accuracy in map reading. Maps are a unique way of communication and they convey geographic and spatial data. Generally, hue-value color schemes are the most effective method to represent geographic data. Hue-value schemes obviously have the advantages of hue differences and value variation. But I think that common rule is not enough. This study focuses on establishing guidelines which will enable optimal use of colors in map making. Previous research has confirmed the importance of colors, but colors have never been dealt with as an independent factor in map making. I would like to provide these guidelines here: First, map makers should select appropriate color schemes according to the haracteristics of data. For instance, they should select a hue-based scheme for qualitative data and a value-based scheme for the quantitative data. Second, quantitative data can be divided into three groups. Therefor, different schemes should be applied according to the characteristics of quantitative data. Third, the type of map task or the correlation between geograhic data and space is also a major factor in selecting color schemes. For instance, hue-based scheme is the most suitable to provide individual regional geographic data. Value-based scheme is the most suitable to provide the general trend of map. And the color scheme is influenced by direct acquisition task or recall task Forth, the education level of map users should be considered in map making. Specially numbers of data classes. Research on color symbolization is important in that computer mapping software is now widely available. Guidelines should be provided to improve the design of customized color schemes. Appropriate use of color schemes can improve the effectiveness of maps, improved color schemes will help map makers, including geography teachers, to gain insights into data.
무연 (Na<sub>1</sub>,K)NbO<sub>3</sub> 계 세라믹스를 이용한 AE센서의 감도특성
류주현,이갑수,홍재일,Yoo, Ju-Hyun,Lee, Gab-Soo,Hong, Jae-Il 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.3
In this study, Acoustic emission(AE) sensors were fabricated using lead-free piezoelectric ceramics for prohibiting environmental pollution. Structure of AE sensors were designed as Langvin type air backing form. Here, the piezoelectic element was used as PZT(EC-65)(AE1) and NKN(AE2), respectively. The measured resonant frequency, the maximum sensitivity frequency and sensitivity of AE sensors were as follows ; 143 kHz, 29.4 kHz and 69.3 dB in AE1 and 179 kHz, 29.4 kHz and 66.3dB in AE2, respectively.
저온에서 소결된 Ba(Ti0.9Zr0.1)O3 세라믹스의 유전 특성 및 전기 열량 효과
류주현 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.1
In this study, in order to develop composition ceramics for refrigeration device application, Ba(Ti0.9Zr0.1)O3composition was fabricated using conventional solid-state method. Electrocaloric effect of this ceramic was investigatedusing the characteristics of P-E hysteresis loops at wide temperature range from room temperature to 150℃. Curietemperature of Ba(Ti0.9Zr0.1)O3 ceramics showed 80℃. The maximum value of ⊿T = 0.12℃ in ambient temperatureof 115℃ under 30 kV/cm was appeared. It is concluded that Ba(Ti0.9Zr0.1)O3 ceramics can be applied as refrigerationdevice application. 본 연구에서는 Ba(Ti0.9Zr0.1)O3 조성을 선택하여 시편을 제조한 후, 인가 전계변화에 따른 유전 및 전기열량 특성을 관찰하였으며 그결과 , 1. 1150도에서 소성된 시편은 전형적인 페로브스카이트상을 나타내었고, 2차상은 관찰되지 않았다. 전계를 5.13kV/cm ∼ 30kV/cm로 변화시켰을 때 분극 값은 온도가 증가함에 따라 유사한 경향으로 감소하였는데 상전이 온도(Tc)에서 선형적으로 감소하였다. 전계 인가에 따른 시편의 온도변화 ΔT는 인가 전계가 클수록 증가하는 경향을 나타내었고 30kV/cm의 전계를 인가하고 측정온도가 상전이 온도(Tc) 부근(80℃)에서부터 크게 증가하다가 115℃에서 최댓값 0.12℃을 나타내었다
PbO량에 따른 저온소결 PMN-PNN-PZT 세라믹스의 유전 및 압전특성
류주현,이석태,김도형,이상호,김국진,Yoo, Ju-Hyun,Lee, Seok-Tae,Kim, Do-Hyung,Lee, Sang-Ho,Kim, Kook-Jin 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.1
In this study, in order to develop multilayer ceramics vibrator for ultrasonic nozzle, PMN-PNN-PZT ceramics were fabricated using $Li_{2}CO_{3}-Na_{2}_CO_{3}$ as sintering aids and their piezoelectric and dielectric characteristics were investigated according to the amount of PbO. With increasing PbO contents, secondary phases were increased and phase structure was changed from tetragonal structure to rhombohedral structure and also electromechanical coupling factor was linearly decreased. At the composition ceramics with the sintering temperature of $870^{\circ}C$ and 1 mol% excess PbO, density, electromechanical coupling factor, dielectric constant, piezoelectric d constant and mechanical quality factor showed the optimum value of $7.879\;g/cm^{3}$, 0.55, 1149, 328 pC/N, 1224, respectively for multilayer ceramics vibrator application for ultrasonic nozzle.
류주현,이갑수,Yoo, Ju-Hyun,Lee, Kab-Soo 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.3
In this study, in order to improve the electrical properties of low temperature sintering piezoelectric ceramics, $[0.05Pb(Zn_{1/2}W_{1/2})-0.07Pb(Mn_{1/3}Nb_{2/3})-0.088Pb(Zr_{0.48}Ti_{0.52})]O_3$(abbreviated as PZW-PMN-PZT) ceramic systems were fabricated using $Bi_2O_3$, CuO and $Li_2CO_3$ as sintering aids and then their piezoelectric and dielectric properties were investigated according to the amount of $Li_2CO_3$ and post-annealing process. Post-annealing process enhanced all physical properties except for mechanical quality factor (Qm). 0.2 wt% $Li_2CO_3$ added and post-annealed specimen showed the excellent values suitable for low loss piezoelectric actuator application as follow: the density = 7.86 $g/cm^3$ electromechanical coupling factor (kp) = 0.575, piezoelectric constant $d_{33}$ = 370 pC/N, dielectric constant ($\varepsilon_r$) = 1546, and mechanical quality factor (Qm) = 1161, respectively.
류주현,이광민 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.5
In this paper, in order to develop the composition ceramics for piezoelectric actuator. (1 − x)(Na 0.52 K 0.443 Li 0.037 )(Nb 0.883 Sb 0.08 Ta 0.037 )O 3 − x(Sr 0.95 Ca 0.05 )ZrO 3 ceramics were sintered at 1020 °C by the conventional solid-state method. The eff ects of (Sr 0.95 Ca 0.05 )ZrO 3 substitution on their microstructure and piezoelectric properties were systematically investigated. The orthorhombic-tetragonal coexistence phase has been found in the ceramics with x = 0.01, 0.015 and x = 0.02. Themaximum value of d 33 was 322 pC/N at x = 0.025 composition ceramics with the rhombohedral phase. The (Sr 0.95 Ca 0.05 )ZrO 3substitution increased the density and then aided the grain growth of specimens. When x = 0.01, the optimal physical propertiesof d 33 = 254 pC/N, ε r = 1096, k p = 0.46, and Q m = 156 were obtained, respectively, for piezoelectric actuator application.
류주현 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.4
Piezoelectric actuators have been utilized in piezoelectric speakers. In this study, in order to develop a piezoelectric actuatorcapable of being used in piezoelectric speakers, Pb(Mn 1/3 Nb 2/3 )0.07(Ni 1/3 Nb 2/3 )0.10(Zr 0.5 Ti 0.5 )0.83O 3 composition ceramicswere fabricated by the conventional mixed oxide method. The eff ects of ZnO and Nb 2 O 5 on their microstructure andpiezoelectric properties were systematically investigated. The tetragonality has been increased in the ceramics with theincrease of the Nb 2 O 5 addition. When Nb 2 O 5 content and sintering temperatures were 0.2 wt%, 940 °C, respectively, theexcellent physical properties of d 33 = 386 p C/N , ε r = 1667, k p = 0.661, Q m = 1285 and FOM = 935 103 were obtained for lowloss piezoelectric actuator application.