Effects of channel thickness variation on bias stress instability of InGaZnO thin-film transistors

Cho, E.N.,Kang, J.H.,Yun, I. Pergamon Press 2011 Microelectronics reliability Vol.51 No.9

Here, we report on the effects of channel (or active) layer thickness on the bias stress instability of InGaZnO (IGZO) thin-film transistors (TFTs). The investigation on variations of TFT characteristics under the electrical bias stress is very crucial for commercial applications. In this work, the initial electrical characteristics of the tested TFTs with different channel layer thicknesses (40, 50, and 60nm) are performed. Various gate bias (V<SUB>GS</SUB>) stresses (10, 20, and 30V) are then applied to the tested TFTs. For all V<SUB>GS</SUB> stresses with different channel layer thickness, the experimentally measured threshold voltage shift (ΔV<SUB>th</SUB>) as a function of stress time is precisely modeled with stretched-exponential function. It is indicated that the ΔV<SUB>th</SUB> is generated by carrier trapping but not defect creation. It is also observed that the ΔV<SUB>th</SUB> shows incremental behavior as the channel layer thickness increases. Thus, it is verified that the increase of total trap states (N<SUB>T</SUB>) and free carriers resulted in the increase of ΔV<SUB>th</SUB> as the channel layer thickness increases.

Contact resistance dependent scaling-down behavior of amorphous InGaZnO thin-film transistors

Cho, E.N.,Kang, J.H.,Yun, I. Elsevier 2011 Current Applied Physics Vol.11 No.4

Here, we report scaling effects on the electrical properties of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFTs had same channel width/length ratio (W/L = 20), but different channel lengths (L = 20, 10, 5, and 2.5 μm). To examine the scaling-down behaviors, short-channel effects and contact resistance of the TFTs were investigated. As the channel length decreased, apparent shift of threshold voltage (V<SUB>th</SUB>) and degradation of subthreshold swing (S<SUB>SUB</SUB>) were shown. In addition, it is also found that the field-effect mobility (μ<SUB>FE</SUB>) was degraded as the channel length was decreased which was originated from contact resistance. Due to this contact resistance effect, drain current (I<SUB>DS</SUB>) was decreased for short-channel devices.

The microRNA miR-124 inhibits vascular smooth muscle cell proliferation by targeting S100 calcium-binding protein A4 (S100A4)

Choe, N.,Kwon, D. H.,Shin, S.,Kim, Y. S.,Kim, Y. K.,Kim, J.,Ahn, Y.,Eom, G. H.,Kook, H. Elsevier Science B.V., Amsterdam. 2017 FEBS letters Vol.591 No.7

<P>S100 calcium-binding protein A4 (S100A4) induces proliferation and migration of vascular smooth muscle cells (VSMCs). We aimed to find the microRNA regulating S100A4 expression. S100A4 transcripts are abruptly increased in the acute phase of carotid arterial injury 1 day later (at day 1) but gradually decreases at days 7 and 14. Bioinformatics analysis reveals that miR-124 targets S100A4. VSMC survival is attenuated by miR-124 mimic but increased by miR-124 inhibitor. miR-124 decreases immediately after carotid arterial injury but dramatically increases at days 7 and 14. miR-124 inhibitor-induced cell proliferation is blocked by S100A4 siRNA, whereas miR-124-induced cell death is recovered by S100A4. Our findings suggest that miR-124 is a novel regulator of VSMC proliferation and may play a role in the development of neointimal proliferation.</P>

An Approach to the Spectral Signature Analysis and Supervised Classification for Forest Damages -An Assessment of Low Altitude Airborne MSS Data

Choen Kim 大韓遠隔探査學會 1991 大韓遠隔探査學會誌 Vol.7 No.2

This paper discusses the capabilities of airborne remotely sensed data to detect and classify forest damages. In this work the AMS (Aircraft Multiband Scanner) was used to obtain digital imagery at 300m altitude for forest damage inventory in the Black Forest of Germany. MSS (Multispectral Scanner) digital numbers were converted to spectral emittance and radiance values in 8 spectral bands from the visible to the thermal infrared and submitted to a maximum-likelihood classification for: (1) tree species; and, (2) damage classes. As expected, the results of MSS data with high spatial resolution 0.75m×0.75m enabled the detection and identification of single trees with different damages and were nearly equivalent to the truth information of ground checked data.

Use of Crown Feature Analysis to Separate the Two Pine Species in QuickBird imagery

Choen Kim 大韓遠隔探査學會 2008 大韓遠隔探査學會誌 Vol.24 No.3

Tree species-specific estimates with spacebome high-resolution imagery improve estimation of forest biomass which is needed to predict the long term planning for the sustainable forest management(SFM). This paper is a contribution to develop crown distinguishing coniferous species, Pinus densiflora and Pinus koraiensis, from QuickBird imagery. The proposed feature analysis derived from shape parameters and first and second-order statistical texture features of the same test area were compared for the two species separation and delineation. As expected, initial studies have shown that both formfactor and compactness shape parameters provided the successful differentiating method between the pine species within the compartment for single crown identification from spacebome high resolution imagery. Another result revealed that the selected texture parameters-the mean, variance, angular second moment(ASM)-in the infrared band image could produce good subset combination of texture features for representing detailed tree crown outline.

An Approach to the Spectral Signature Analysis and Supervised Classification for Forest Damages - An Assessment of Low Altitued Airborne MSS Data -

Kim, Choen The Korean Society of Remote Sensing 1991 大韓遠隔探査學會誌 Vol.7 No.2

This paper discusses the capabilities of airborne remotely sensed data to detect and classify forest damades. In this work the AMS (Aircraft Multiband Scanner) was used to obtain digital imagery at 300m altitude for forest damage inventory in the Black Forest of Germany. MSS(Multispectral Scanner) digital numbers were converted to spectral emittance and radiance values in 8 spectral bands from the visible to the thermal infrared and submitted to a maximum-likelihood classification for : (1) tree species ; and. (2) damage classes. As expected, the resulted, the results of MSS data with high spatial resolution 0.75m$\times$0.75m enabled the detection and identification of single trees with different damages and were nearly equivalent to the truth information of ground checked data.

IKONOS 화상 기반의 산불피해등급도 작성을 위한 정규산불해비율(NBR) 평가

김천 ( Choen Kim ) 大韓遠隔探査學會 2008 大韓遠隔探査學會誌 Vol.24 No.2

본 연구는 KOMPSAT-2호 및 3호의 화상활용의 일환으로 고해상도 위성화상을 이용한 산불피해비율(NBR) 기반의 산불피해등급도 작성 개발이다. 무엇보다 중적외선 밴드가 없는 IKONOS 화상에서 NBR 산법개발과 NBR 기초한 삼척과 청양·예산 산불피해지의 산불피해등급도를 기존의 다른 기법과 평가한 결과 우수성이 입증되었다. 향후 고해상도 KOMPSAT 화상을 이용한 NBR 기반의 산불피해등급도는 산불 후 피해복원에 중요한 정보를 제공할 것이다. Burn severity is an important role for rehabilitation of burned forest area. This factor led to the pilot study to determine if high resolution IKONOS images could be used to classify and delinenate the burn severity over burned areas of Samchock Fire and Cheongyang-Yesan Fire. The results of this study can be summarized as follows: 1. The modified Normalized Burn Ratio (NBR) for IKONOS imagery can be evaluated using burn severity mapping. 2. IKONOS-derived NBR imagery could provide fire scar and detail mapping of burned areas at Samchock Fire and Cheongyang-Yesan Burns.

Fuyo-1 OPS 자료를 이용한 낙동강 하류지역의 환경계측 시고

김천 ( Choen Kim ) 大韓遠隔探査學會 1996 大韓遠隔探査學會誌 Vol.12 No.2

본 연구는 낙동강 하류지역의 지속가능한 개발과 환경보전을 위하여 위성탑재 Fuyo-1 OPS VNIR 주사자료에 의한 겨울철 환경계측을 시범·고찰하였다. 따라서 그림자 효과가 강하게 발생하는 산림에 대해 방향성 분광반사특성과 식생지수를 중점분석하고 분광각대응분류를 통하여 겨울철 토지피복도를 산출하였다. 그리고 해·담수 분포도와 낙동강 하류의 수질오염도를 작성하기 위하여 가림기법, 최대우도추정분류기, 그리고 유색밀도편분기법을 응용하였다. 본 연구에서 획득된 결과를 요약하면 첫째로 양지사면의 분광반사치와 식생지수값 모두 음지사면보다 높다. 둘째로 위장반사현상이 일어나는 지역을 주제별 분류를 할 경우 분광각대응 분류 산법이 유용하다. 셋째로 겨울철 낮은 태양고도에도 해·담수분포도를 산출하는데 최대우도추정분류산법이 적합하다. 넷째로 근적외선밴드를 사용하여 가림·유색밀도편분기법에 의해 산출된 수질오염도는 낙동강의 수질상태를 분석할 수 있다. 마지막으로 유색코드 정규식생지수화상은 사면방위에 따른 임관밀도를 파악하는데 이용된다. The objectives of this investigation are: 1. To analyze spectral signature and the associated vegetation index for geometric illumination conditions influenced by low solar elevation and high slope orientations in mountainous forest. 2. To assess the accuracy of the spectral angle mapper classification for the a winter land cover in comparison with the maximum likelihood classification. 3. To produce the image of water quality and water properties that could be used to estimate the water pollution sources and the tide-included by turbid water in estuarine and coastal areas. These objectives are to characterize environmental and ecological monitoring applications of the Nak-Dong River Basin by using Fuyo-1 OPS VNIR data acquired on December 26, 1992. The Results of this paper are as follows: 1. The spectral digital numbers and vegetation indexes (NDVI and TVI) of mountainous forest are higher on the slope facing the sun than on the slope hidden the sun under low sun elevation condition. 2. The spectral angle mapper algorithm produces a more accurate land cover classification of areas with steep slope, various aspects and low solar elevation than the maximum likelihood classifier. 3. The maximum likelihood classification images can be used for identifying the location and movement of both freshwater and salt water, regardless of geometric illumination conditions. 4. The color-coded density sliced image of selected water bodies by using the near-infrared band 3 can provide distribution of the water quality of the Lower Nak-Dong River. 5. The color-coded normalized difference vegetation index image of the selected mountain forest is suitable to classify winter vegetation cover types, i.e., forest canopy densities for slope orientations.

QuickBird 화상을 이용한 산불 삼림교란도 작성

김천 ( Choen Kim ) 大韓遠隔探査學會 2009 大韓遠隔探査學會誌 Vol.25 No.1

본 논문은 중적외선 밴드가 없는 고해상도 QuickBird 화상을 이용하여 옥계 산불피해지의 삼림교란 지도화에 관한 연구이다. Landsat ETM+ △NBR에 기초한 QuickBird NBR을 통해 산불피해등급도 보다 발전된 산불후 삼림교란도를 작성하였다. 무엇보다 QuickBird 수분지수와 Landsat ETM+ 7(중적외선)밴드 간의 상관계수에 QuickBird 수분지수를 곱한 치환수치로 생성되는 MIR모의밴드를 통해 산불피해 등급도와 산불후 삼림교란도가 제작된다. QuickBird NBR기반의 산불후 삼림교란도는 Landsat ETM+ △NBR기반의 산불피해등급도와의 비교 정확도 평가에서 본질적 확실의 높은 일치성(KHAT값=0.7886)을 갖고 있어, 산불피해지의 자연복원 나아가 삼림벌채로 야기된 삼림교란에 유용하게 사용될 것이다. This paper presents the capability to use QuickBird imagery for effects of forest disturbance in Okgye burned area. Particular attention of this paper deals with the NBR-derived mapping burn severity on QuickBird imagery to locate reliable rehabilitation(namely, secondary succession) over postfire surface. Comparisons of the mapping forest disturbance derived from QuickBird NBR data and the mapping burn severity derived from Landsat △NBR data show substantial agreement (KHAT value=0.7886). The method calculated from the correlation between QuickBird wetness and Landsat ETM+ band7 may have application to forest harvest disturbance.

활엽수 산불피해등급을 위한 고해상도 화상 판독열쇠

김천(Choen Kim),정태웅(Tae-Woong Jung),윤보열(Bo-Yeol Yoon),홍성후(Sung-Hoo Hong) 대한공간정보학회 2006 한국지형공간정보학회 학술대회 Vol.2006 No.5

본 논문은 향후 운용될 국산 고해상도 위성화상의 활용일환으로 산불활엽수피해림 중 참나무(림)와(과) 밤나무(림)의 산불피해등급 육안판독열쇠에 관한 연구이다. 본 육안판 독열쇠는 참나무(림)와(과) 밤나무(림)의 산불피해등급 판별을 위해 4가지 요소, 즉 색, 형태, 구조 그리고 질감에 기초로 개발하였고, 개발에 사용된 화상자료는 0.3m 공간해상도의 천연색 항공사진을 수치화(digital)한 화상과 0.8m 공간해상도의 위성 QuickBird 화상 및 1m 공간해상도의 위성 IKONOS화상이다. GIS의 공간정보 입력에 사용된 고해상도 화상을 정량분석할 경우 지형효과의 그림자영향으로 인한 난제가 수반되기 때문에 실제로 육안에 의한 정성분석을 통해 정밀정보가 제공되고 있다. 개발된 판독열쇠는 항공 위색적외선 화상(CIR imagery)과 항공 흑백 적외선 사진(IR photos)에서도 이방향성 지형효과와 무관하게 산물활엽수(림)피해등급 판별을 위해 사용할 수 있다.