• Title/Summary/Keyword: Sensing layer

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Trends of Cognitive Radio Technology (Cognitive Radio 기술 동향)

  • Kim, C.J.
    • Electronics and Telecommunications Trends
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    • v.21 no.4 s.100
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    • pp.62-69
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    • 2006
  • 유비쿼터스 정보화사회의 도래와 함께 한정된 주파수자원에 대한 수요가 증가됨에 따라 이를 효율적으로 이용하기 위한 기술이 더욱 각광을 받고 있다. 이중에서도 스펙트럼 환경을 측정하여 사용하지 않은 주파수를 선정, 기존의 전파환경과 양립하면서 통신을 하는 CR 기술은 미래 무선통신의 핵심 기술로 인식되고 있다. CR 기술은 SDR 기술을 기반으로 스펙트럼 센싱(spectrum sensing) 기능을 활용하여 가용한 주파수를 선정하여 통신하는 기본적인 기능과 여러 가지 환경 파라미터를 지속적으로 업데이트하는 learning algorithm이 합쳐진 기술이다. 본 고에서는 CR 기술을 설명하고, CR의 응용으로 현재 표준화가 진행되고 있는 IEEE 802.22 WRAN 표준화 활동과 WG에서 검토되고 있는 기술, 즉 physical layer, MAC layer, 그리고 spectrum sensing의 주요기술을 소개한다.

Sensing Properties of Porous Silicon Layer for Organic Vapors (다공질 실리콘의 유기가스 검지 특성)

  • 김성진;이상훈;최복길
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.11
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    • pp.963-968
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    • 2002
  • In this work, porous silicon (PS) layer is investigated as a sensing material to detect organic vapors such as ethanol (called alcohol), methanol, and acetone in low concentrations. To do this, PS sensors were fabricated. They have a membrane structure and comb-type electrodes were used to detect the change of electrical resistance effectively. PS layer on Si substrates was formed by anodization in HF solution of 25%. From fabricated sensors, current-voltage (Ⅰ-Ⅴ) curves were measured for gases evaporated from 0.1 to 0.5% organic solution concentrations at 36$\^{C}$. As the result, all curves showed rectifying behavior due to a diode structure between Si and the PS layer. The conductance of most sensors increased largely at high voltage of 5V, but the built-in potential on the measured Ⅰ-Ⅴ curve was lowered inversely by the adsorption effect of the organic vapors with high dipole moment.

CO Gas Sensing Characteristics of Nanostructured ZnO Thin Films (산화아연 나노구조 박막의 일산화탄소 가스 감지 특성)

  • Hung, Nguyen Le;Kim, Hyo-Jin;Kim, Do-Jin
    • Korean Journal of Materials Research
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    • v.20 no.5
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    • pp.235-240
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    • 2010
  • We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of $500^{\circ}C$. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at $250^{\circ}C$ and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.

Abnormal current-voltage characteristics of $SnO_2$ oxide semiconductor and their application to gas sensors ($SnO_2$ 산화물 반도체의 비정상적 전류 - 전압 특성과 가스센서로의 응용)

  • Lee Kyu-chung;Yoon Ho-Kun;Hur Chang-Wu
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.7
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    • pp.1436-1441
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    • 2004
  • Abnormal current-voltage characteristics of an oxide semiconductor have been investigated and a novel method of detecting reducing gases utilizing self-heating mechanism of sensing layer without an additional heater has been developed. Planar-type sensors based on WO3-doped SnO2 were fabricated using a screen-printing technique. The applied voltage across the sensing layer caused heating of the sensing layer and the current abruptly varied upon exposure to a gas mostly as a result of surface reactions. A unique and fascinating aspect of the gas sensing scheme is that no additional heater is necessary for detection. The new sensing method has been applied to C2H5OH gas in this preliminary work.

REMOTE SENSING OF ATMOSPHERIC FRONTAL DYNAMICS OVER THE OCEAN

  • Levy, Gad;Patoux, Jerome
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.1003-1006
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    • 2006
  • Frontal regions in midlatitude storms exhibit a wide range of behavior, which can be observed by remote sensors. These include decay, strengthening, rotating, and sometimes spawning of new cyclones. Here we refine and apply recent theories of front and frontal wave development to a case of a front clearly observed and analyzed in remote sensing data. By applying innovative analysis techniques to the data we assess the respective roles of ageostrophy, background deformation, and Boundary Layer processes in determining the evolution of the surface front. Our analysis comprises of diagnosis of the terms appearing in the vorticity and divergence equations using remotely sensed observations.

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Pt-AlGaN/GaN HEMT-based hydrogen gas sensors with and without SiNx post-passivation

  • Vuong, Tuan Anh;Kim, Hyungtak
    • Journal of IKEEE
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    • v.23 no.3
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    • pp.1033-1037
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    • 2019
  • GaN-based sensors have been widely investigated thanks to its potential in detecting the presence of hydrogen. In this study, we fabricated hydrogen gas sensors with AlGaN/GaN heterojunction and investigated how the sensing performance to be affected by SiN surface passivation. The gas sensor employed a high electron mobility transistors (HEMTs) with 30 nm platinum catalyst as a gate to detect the hydrogen presence. SiN layer was deposited by inductively-coupled chemical vapor deposition as post-passivation. The sensors with SiN passivation exhibited hydrogen sensing characteristics with various gas flow rates and concentrations of hydrogen in inert background gas at $200^{\circ}C$ similar to the ones without passivation. Aside from quick response time for both sensors, there are differences in sensitivity and recovery time because of the existence of the passivation layer. The results also confirmed the dependence of sensing performance on gas flow rate and gas concentration.

Development of Bioinspired Robotic Gripping Technology for Gripping Rough & Wet Surfaces based on Tactile Sensing (촉각센싱기반 거칠고 젖은 표면 파지가 가능한 생체모사 로봇용 그리핑 기술 개발)

  • Kim, Da Wan
    • The Journal of Korea Robotics Society
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    • v.17 no.3
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    • pp.282-287
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    • 2022
  • High shear adhesion on wet and rough surfaces and tactile feedback of gripping forces are highly important for realizing robotic gripper systems. Here, we propose a bioinspired robotic gripper with highly shear adhesion and sensitive pressure sensor for tactile feedback systems. To achieve them, we fabricated multi-walled carbon nanotube sensing layer on a thin polymeric adhesive layer of polydimethylsiloxane. With densely hexagonal-packed microstructures, the pressure sensor achieved 9 times the sensing property of a sensor without microstructures. We then assembled hexagonal microstructures inspired by the toe pads of a tree frog, giving strong shear adhesion under both dry and wet surfaces such as silicon (42 kPa for dry and ~30 kPa for underwater conditions) without chemical-residues after detachment. Our robotic gripper can prevent damage to weak or smooth surfaces that can be damaged at low pressure through pressure signal feedback suggesting a variety of robotic applications.

On the Spatial and Temporal Variability of L-band Polarimetric SAR Observations of Permafrost Environment in Central Yakutia

  • Park, Sang-Eun
    • Korean Journal of Remote Sensing
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    • v.33 no.1
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    • pp.47-60
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    • 2017
  • The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

Fabrication of a Humidity Sensing Device using Silicon Thermopile (실리콘 Thermopile을 이용한 감습 소자의 제작)

  • 김태윤;주병권;오명환;박정호
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.4
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    • pp.70-76
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    • 1994
  • A humidity sensing device based on a new humidity sensing principle is designed and fabricated in this study. The silicon thermopile is consisted of 25 couples of p-type diffused layer/Al strips. The internal resistance and the Seebeck coefficient are 300kl and 537$\mu$V/K, respectively Fabricated sensors showed linear response characteristics proportional to relative humidity changes with a sensitivity of 9$\mu$V/%RH in the range from 20% to 90%.

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REMOTE SENSING OF THE CHINA SEAS AT ORSI/OUC

  • HE, Ming-Xia;Zeng, Kan;Chen, Haihua;Zhang, Tinglu;Hu, Lianbo;Liu, Zhishen;Wu, Songhua;Zhao, Chaofang;Guan, Lei;Hu, Chuanmin
    • Proceedings of the KSRS Conference
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    • v.1
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    • pp.11-14
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    • 2006
  • We present an overview on the observation and research for the China seas using both field experiments and multi-sensor satellite data at ORSI/OUC, covering two topics: (1) Spatial and temporal distribution of internal waves in the China Seas and retrieval of internal wave parameters; (2) Retrieval, validation, and cross-comparison of multi-sensor ocean color data as well as ocean optics in situ experiments in the East China Sea. We also present an incoherent Doppler wind lidar, developed by ORSI, and its observation for marine-atmospheric boundary layer.

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