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Recent Vegetation History and Environmental Changes in Wangdeungjae Moor of Mt. Jiri
김재근,이양우 한국생태학회 2005 Journal of Ecology and Environment Vol.28 No.3
To reveal vegetation history and environmental changes in Mt. Jiri, sediment cores were collectedfrom Wangdeungjae moor of Mt. Jiri. Overall dry matter accumulation rates and sedimentation rates by 14C-dating were 0.027 kgㆍm-2ㆍyr-1and 0.184 mm/yr since 1250 (76040 yrs BP, 14 cm in depth). There are three pollen zones; the first zone is below 14 cm depth where Quercus dominated, the second zone is from 14 cm to 6 cm depth where Gramineae increased and Quercus and Salix dominated and the third zone is from 6 cm depth to the top where Pinus and dominated. Total pollen concentration gradually increased from bottom to the top of sediment core, which implies wet, anaerobic and cool condition during covered period by the core. Calcium and magnesium contents had increased since 14 cm depth, with peaks at 13 and 20 cm depths. This indicates that groundwater had recently become relatively more important than surface water as water source of Wangdeungjae moor. Exotic plant or Chenopodiacea pollen was less than 1%. There was little variation in total N and P contents along the length of the core. These results support that Wangdeungjae mor has been little affected by anthropogenic activities. Also, nutrients and heavy metal contents indicate the baseline condition of Wangdeungjae moor.
다결정 실리콘 박막 트랜지스터 Active Matrix OLED 디스플레이를 위한 이중 변조 구동
김재근,정주영 대한전자공학회 2004 電子工學會論文誌-SD (Semiconductor and devices) Vol.41 No.10
본 논문에서는 진폭 변조와 펄스 폭 변조를 모두 사용하는 새로운 AMOLED 디스플레이 구동 방식을 개발하였다. 펄스 폭 변조를 위해서 다섯 개의 서브 프레임으로 화상 프레임을 나누었고 진폭 변조를 위해 TFT 게이트 전압에 의해 제어되는 3가지의 OLED 휘도(전류) 레벨을 사용하였다. 이 두 종류의 변조를 조합하여 35(=243) 계조를 얻었다. 그리고 DAC를 사용하지 않고 2개의 쉬프트 레지스터를 갖는 새로운 데이터 전극 구동 회로를 설계하였다. 회로 동작은 6㎛ 채널 길이 다결정 TFT의 전류-전압 특성에서 추출된 TFT 파라미터를 이용한 HSpice 시뮬레이션을 통하여 검증하였다. 시뮬레이션 결과로부터 320×240, 이중 스캔, 243 계조 AMOLED 디스플레이를 구현할 수 있음을 확인하였다. We developed a new ANGLED display driving method which used both amplitude and pulse width modulation. For pulse width modulation, we divided a picture frame time into S sub-frames. For amplitude modulation, we used three OLED luminance(or current) levels which were controlled by TFT's gate voltages. By combining these two modulation methods, we obtained 35(=243) grey levels. And we designed a new data electrode driving circuit block with two shift registers without using DAC's. To verify the feasibility, we simulated the key circuit components by HSpice with TFT parameters extracted from current-voltage characteristics of 6${\mu}{\textrm}{m}$ channel length polysilicon TFT's. From the simulation results, we found that 320${\times}$240, dual scan, 243 grey level AMOLED display can be designed with this method.