• Title/Summary/Keyword: Bias-stress

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Evaluation of NDVI Retrieved from Sentinel-2 and Landsat-8 Satellites Using Drone Imagery Under Rice Disease (드론 영상을 이용한 Sentinel-2, Landsat-8 위성 NDVI 평가: 벼 병해 발생 지역을 대상으로)

  • Ryu, Jae-Hyun;Ahn, Ho-yong;Na, Sang-Il;Lee, Byungmo;Lee, Kyung-do
    • Korean Journal of Remote Sensing
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    • v.38 no.6_1
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    • pp.1231-1244
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    • 2022
  • The frequency of exposure of field crops to stress situations is increasing due to abnormal weather conditions. In South Korea, large-scale diseases in representative paddy rice cultivation area were happened. There are limits to field investigation on the crop damage due to large-scale. Satellite-based remote sensing techniques are useful for monitoring crops in cities and counties, but the sensitivity of vegetation index measured from satellite under abnormal growth of crop should be evaluated. The goal is to evaluate satellite-based normalized difference vegetation index (NDVI) retrieved from different spatial scales using drone imagery. In this study, Sentinel-2 and Landsat-8 satellites were used and they have spatial resolution of 10 and 30 m. Drone-based NDVI, which was resampled to the scale of satellite data, had correlation of 0.867-0.940 with Sentinel-2 NDVI and of 0.813-0.934 with Landsat-8 NDVI. When the effects of bias were minimized, Sentinel-2 NDVI had a normalized root mean square error of 0.2 to 2.8% less than that of the drone NDVI compared to Landsat-8 NDVI. In addition, Sentinel-2 NDVI had the constant error values regardless of diseases damage. On the other hand, Landsat-8 NDVI had different error values depending on degree of diseases. Considering the large error at the boundary of agricultural field, high spatial resolution data is more effective in monitoring crops.

Header-Based Power Gating Structure Considering NBTI Aging Effect (NBTI 노화 효과를 고려한 헤더 기반의 파워게이팅 구조)

  • Kim, Kyung-Ki
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.49 no.2
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    • pp.23-30
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    • 2012
  • This paper proposes a novel adaptive header-based power gating structure to compensate for the performance loss and the increased wake-up time of the power gating structures induced by the negative bias temperature instability (NBTI) effect. The proposed structure consists of variable width footers based on the two-pass power gating and a new NBTI sensing circuit for an adaptive control. The simulation results of the proposed structure are compared to those of power gating without the adaptive control and show that both the circuit-delay and wake-up time dependence of the power gating structure on the NBTI stress is minimized with only 3% and 4% increase, respectively while keeping small leakage power and rush-current. In this paper, a 45 nm CMOS technology and predictive NBTI model have been used to implement the proposed circuits.

Characterization of Electrical Properties on Cu Diffusion in Low-k Dielectric Materials for ULSI Interconnect (반도체 배선용 저 유전 물질에서의 구리 확산에 대한 전기적 신뢰성 평가)

  • Lee Hee-Chan;Joo Young-Chang;Ro Hyun-Wook;Yoon Do-Young;Lee Jin-kyu;Char Kook-Heon
    • Journal of the Microelectronics and Packaging Society
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    • v.11 no.3 s.32
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    • pp.9-15
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    • 2004
  • We investigated the electrical properties of copolymer low-k materials that are compromised of the PMSSQ(Poly Methyl Silsesquioxane)-based matrix with the BTMSE (Bis Tri Methoxy Silyl Ethane) additives. We manufactured MIS-type test samples using the copolymer as the insulator and measured their leakage current and failure time by means of the BTS (bias-temperature-stress) test. The failure time was observed to decrease drastically when the porosity of the copolymer was increased over $30\%$. From the measurement of failure time with respect to temperature. the activation energy of Cu drift through the copolymer was calculated to be 1.51 eV.

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Effects of $SiO_2$ or SiON tunneling gate oxide on Au nano-particles floating gate memory (Au 나노 입자를 이용한 floating gate memory에서 $SiO_2$ or SiON 터널링 게이트 산화막의 영향)

  • Koo, Hyun-Mo;Lee, Woo-Hyun;Cho, Won-Ju;Koo, Sang-Mo;Chung, Hong-Bay;Lee, Dong-Uk;Kim, Jae-Hoon;Lee, Min-Seung;Kim, Eun-Kyu
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.11a
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    • pp.67-68
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    • 2006
  • Floating gate non-volatile memory devices with Au nano-particles embedded in SiON or $SiO_2$ dielectrics were fabricated by digital sputtering method. The size and the density of Au are 4nm and $2{\times}10^{-12}cm^{-2}$, respectively. The floating gate memory of MOSFET with 5nm tunnel oxide and 45nm control oxide have been fabricated. This devices revealed a memory effect which due to proGrainming and erasing works perform by a gate bias stress repeatedly.

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Electrical and Mechanical Properties of Cu(Mg) Film for ULSI Interconnect (고집적 반도체 배선용 Cu(Mg) 박막의 전기적, 기계적 특성 평가)

  • 안재수;안정욱;주영창;이제훈
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.3
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    • pp.89-98
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    • 2003
  • The electrical and mechanical properties of sputtered Cu(Mg) films are investigated for highly reliable interconnects. The roughness, adhesion, hardness and resistance to thermal stress of Cu(Mg) film annealed in vacuum at $400^{\circ}C$ for 30min were improved than those of pure Cu film. Moreover, the flat band voltage(V$_{F}$ ) shift in the Capacitance-Voltage(C-V) curve upon bias temperature stressing(BTS) was not observed and leakage currents of Cu(Mg) into $SiO_2$ were three times less than those of pure Cu. Because Mg was easy to react with oxide than Cu and Si after annealing, the Mg Oxide which formed at surface and interface served as a passivation layer as well.

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MALADAPTIVE COGNITIONS ACCORDING TO DEPRESSION, ANXIETY, AND AGE OF CHILDREN WITH ADHD - FOCUS ON COGNITIVE ERROR AND ATTRIBUTIONAL BIAS - (ADHD 아동의 우울, 불안, 공격성과 연령에 따른 부적응적 인지 특성 - 인지 오류와 귀인 편파를 중심으로 -)

  • Kim, Young-Mi;Choi, Eun-Ju
    • Journal of the Korean Academy of Child and Adolescent Psychiatry
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    • v.12 no.2
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    • pp.275-281
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    • 2001
  • This study examined the relationship between psychopathology(depression, anxiety, aggression), maladaptive cognitions(negative cognitive errors, attributional biases), and age of children with ADHD. 40 ADHD children and their mother completed questionnaires assessing depression, anxiety, aggression level and maladaptive cognitions of children. The results showed that maladaptive cognitions of children with ADHD was not significantly associated with their depression, anxiety, aggression level. Age was negatively related to internal stable attributions for negative events that was characteristic in depression, and had significantly effect on internal stable attributions for negative events. As age of ADHD children increased, their internal attribution for negative events reduced. It seems that their depression and anxiety level is associated with current stress event rather than maladaptive cognitions. Suggestions and limitations of this study, and the directions for future study were discussed.

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Predictors of Postpartum Depression: Prospective Cohort Study (산후우울증 관련요인: 전향적 코호트 연구)

  • Youn, Ji Hyang;Jeong, Ihn Sook
    • Journal of Korean Academy of Nursing
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    • v.43 no.2
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    • pp.225-235
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    • 2013
  • Purpose: This prospective cohort study was done to investigate recall bias to antepartum variables measured at postpartum periods and predictors of postpartum depression. Methods: Participants were 215 women who answered a self-administered questionnaire which included demographics, Postpartum Depression Predictors Inventory-Revised and Korean version of Edinburgh Postpartum Depression Scale at antepartum 36-40 weeks and postpartum 2 weeks and 6 weeks. Data were analyzed using kappa, and hierarchical multiple logistic regression. Results: Agreement between antepartum variables at both antepartum and two postpartum periods was relatively high (${\kappa}$=.55- .95). Postpartum depression rates were 36.3% and 36.7% at two follow-up points. In hierarchical multiple logistic regression analysis, prenatal depression (OR=4.32, 95% CI: 1.41-13.19; OR=5.19, 95% CI: 1.41-19.08), social support (OR=1.40, 95% CI: 1.18-1.66; OR=1.27, 95% CI: 1.06-1.53) and maternity blues (OR=4.75, 95% CI: 1.89-11.98; OR=4.22, 95% CI: 1.60-11.12) were commonly associated with postpartum depression at two follow-up points. Child care stress (OR=1.85, 95% CI: 1.01-3.37) was only associated with postpartum depression at 2 weeks postpartum and pregnancy intendedness (OR=1.57, 95% CI: 1.09-2.27) was only associated with postpartum depression at 6 weeks postpartum. Conclusions: The results indicate a need to apply nursing interventions such as prenatal education and counseling with families from antenatal period.

Fabrication Process of Single Flux Quantum ALU by using Nb Trilayer (Nb Trilayer를 사용한 단자속양자 논리연산자의 제작공정)

  • Kang, J.H.;Hong, H.S.;Kim, J.Y.;Jung, K.R.;Lim, H.R.;Park, J.H.;Hahn, T.S.
    • Progress in Superconductivity
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    • v.8 no.2
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    • pp.181-185
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    • 2007
  • For more than two decades Nb trilayer ($Nb/Al_2O_3/Nb$) process has been serving as the most stable fabrication process of the Josephson junction integrated circuits. Fast development of semiconductor fabrication technology has been possible with the recent advancement of the fabrication equipments. In this work, we took an advantage of advanced fabrication equipments in developing a superconducting Arithmetic Logic Unit (ALU) by using Nb trilayers. The ALU is a core element of a computer processor that performs arithmetic and logic operations on the operands in computer instruction words. We used DC magnetron sputtering technique for metal depositions and RF sputtering technique for $SiO_2$ depositions. Various dry etching techniques were used to define the Josephson junction areas and film pattering processes. Our Nb films were stress free and showed the $T{_c}'s$ of about 9 K. To enhance the step coverage of Nb films we used reverse bias powered DC magnetron sputtering technique. The fabricated 1-bit, 2-bit, and 4-bit ALU circuits were tested at a few kilo-hertz clock frequency as well as a few tens giga-hertz clock frequency, respectively. Our 1-bit ALU operated correctly at up to 40 GHz clock frequency, and the 4-bit ALU operated at up to 5 GHz clock frequency.

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Electrical performance and improvement of stability in ultra thin amorphous IGZO TFT on flexible substrate of surface roughness (Flexible한 기판 표면 거칠기에 따른 초박형 비정질 IGZO TFT의 전기적 특성 및 안정성 개선)

  • Sin, Dae-Yeong;Jeong, Seong-Hyeon;Jo, Hyeong-Gyun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.126-126
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    • 2018
  • 최근 차세대 디스플레이인 flexible 하고 transparent 한 디스플레이 개발이 진행 중 이며, 이러한 디스플레이가 개발 되기 위해 백 플레인으로 사용되는 Thin Film Transistor (TFT) 또한 차세대 디스플레이 못지 않게 연구가 진행 되고 있다. 기존의 무기물을 기반으로 하고 Rigid한 TFT는 현재 많은 곳에 적용이 되어 사람들이 사용 하고 있다. 하지만 이미 시장은 포화상태이며 차세대 디스플레이 컨셉인 flexible 하고 투명한 것과 맞지 않는다. 그래서 유연하며 투명한 특성을 가진 TFT에 대한 연구가 활발히 진행 되고 있으며 많은 성과를 이루었다. 이러한 소자를 이용하여 훗날 Electronic-skin(e-skin)이라 부르는 전자 피부를 활용하여 실시간 모니터링 할 수 있는 헬스 케어 분야 등에 활용 가치 또한 높다. 현재 유연하며 투명한 기판 및 물질 개발에 많은 연구 개발이 진행 되고 있다. 하지만 유연한 기판을 사용하여 TFT를 제작한 후 stress나 bending에 대한 내구성과 안정성, 신뢰성 등이 무기물을 기반으로 한 TFT에 비해 좋지 않은 실정이다. 따라서 유연하며 투명한 기판을 사용한 TFT에 대한 안정성, 신뢰성 등을 확보하여야 한다. 본 연구 에서는 유연한 기판을 사용하여 TFT를 제작 한 후, TFT특성과 안정성을 확보하는 것을 목표로 실험을 진행하였다. 우리는 Mo전극과 Parylene 기판을 사용하여 유연한 TFT소자를 탑 게이트 구조로 제작 하였고 Rigid한 Glass기판 위에 Floating Process를 진행하기 위해 PVA층을 코팅 후 그 위에 Parylene을 CVD로 증착 하고 IGZO를 Sputter를 사용해 증착했다. Parylene은 DI Water 70도에서 Floating 공정을 통해 Rigid 기판에서 탈착 시켰다. 유연한 기판 위에 TFT를 제작 후 bending에 대한 특성 변화 및 안정성에 대한 측정을 실시하였다. Bending에 대한 특성 변화는 우수한 결과가 나왔지만 안정성 측정 중 Negative Bias Stress(NBS) 상에서 비정상적인 On Current Drop 현상이 발생 되었다. Parylene과 Channel층 사이 interface roughness로 인해 charge trap이 되고 이로 인해 On Current Drop 이라는 현상으로 나타났다. 그래서 우리는 Parylene 기판과 Channel 층간의 surface roughness를 개선하기 위한 방법으로 UV Treatment를 사용하였고 시간을 다르게 하여 surface 개선을 진행했다. Treatment 시간을 증가 시킴에 따라 Surface roughness가 많이 좋아 졌으며, Surface를 개선하고자 비정상적인 On Current Drop 현상이 없어졌으며 위 실험으로 Polymer의 surface roughness에 따라 TFT에 대한 안정성에 대한 신뢰성이 확보 될 수 있는 것을 확인 하였다.

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Improved Contact property in low temperature process via Ultrathin Al2O3 layer (Al2O3 층을 이용한 저온공정에서의 산화물 기반 트랜지스터 컨택 특성 향상)

  • Jeong, Seong-Hyeon;Sin, Dae-Yeong;Jo, Hyeong-Gyun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.55-55
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    • 2018
  • Recently, amorphous oxides such as InGaZnO (IGZO) and InZnO (IZO) as a channel layer of an oxide TFT have been attracted by advantages such as high mobility, good uniformity, and high transparency. In order to apply such an amorphous oxide TFTs to a display, the stability in various environments must be ensured. In the InGaZnO which has been studied in the past, Ga elements act as a suppressor of oxygen vacancy and result in a decreased mobility at the same time. Previous studies have been showed that the InZnO, which does not contain Ga, can achieve high mobility, but has relatively poor stability under various instability environments. In this study, the TFTs using $IZO/Al_2O_3$ double layer structure were studied. The introduction of an $Al_2O_3$ interlayer between source/drain and channel causes superior electrical characteristics and electrical stability as well as reduced contact resistance with optimally perfect ohmic contact. For the IZO and $Al_2O_3$ bilayer structures, the IZO 30nm IZO channels were prepared at $Ar:O_2=30:1$ by sputtering and the $Al_2O_3$ interlayer were depostied with various thickness by ALD at $150^{\circ}C$. The optimal sample exhibits considerably good TFT performance with $V_{th}$ of -3.3V and field effect mobility of $19.25cm^2/Vs$, and reduced $V_{th}$ shift under positive bias stress stability, compared to conventional IZO TFT. The enhanced TFT performances are closely related to the nice ohmic contact properties coming from the defect passivation of the IZO surface inducing charge traps, and we will provide the detail mechanism and model via electrical analysis and transmission line method.

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