• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04a
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• pp.74-75
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• 2009

White light emitting device based on a red fluorescence material (5,6,11,12)-Tetraphenylnaphthacene(Rubrene) has been fabricated. The white OLED consists of it and a blue phosphorescent material FIrPic (iridum-bis(4,6,-difluorophenylpyridinato-N,C2)-picolinate) The threshold voltage is 5.3V, and the brightness reaches $1000\;cd/m^2$ at 11V, $14.5\;mA/cm^2$. The color of the light corresponds to a CIE coordinate of (0.30, 0.38). The highest efficiency of the device can reach 9.5 cd/A or 5.5 1m/W at 6V, $0.1mA/cm^2$.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.634-639
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• 2013

We investigated the effects of a cathode underlayer on the electroluminescence (EL) characteristics of organic light-emitting diodes (OLEDs) using various metal acetates (M-acetate, M = Li, Na, K, Cs) as a cathode underlayer. When 1 nm thick M-acetate layers were used as a cathode underlayer, the OLEDs with M-acetate showed better EL performance than the device with the conventional LiF electron injection layer except the device with Cs-acetate. More enhanced current density and improved EL characteristics were obtained when lower work function metal acetate was employed. In addition, the optimum M-acetate layer thickness that gives the best device performance proved to be 0.7 and 2.0 nm for Li-acetate and Cs-acetate, respectively, probably depending on the molecular size of M-acetate. The OLEDs with the M-acetate layers of optimized thickness demonstrated more than 60% enhanced current efficiency compared with that of the device using an LiF layer at the same applied voltage.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1213-1222
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• 2021

This study is a digitalization study based on ICT technology as part of the development of innovative technologies in the new energy industry as a 2050 carbon-neutral policy. It is the development of an oneM2M-based IoT server platform that can be integrated and managed in conjunction with the external interface of each energy facility. It analyzes KEPCO's e-IoT standard specifications through the Power Research Institute's 'SPIN' and develops representative standards, LWM2M and oneM gateway platforms. OneM2M secures and analyzes the recently announced standard for Release 2 instead of the existing Release 1. In addition, the e-IoT standard oneM2M platform is developed based on R2. In addition, it selects the specifications for e-IoT gateway devices that can sufficiently implement KEPCO's e-IoT standards. In addition, a technology and system for developing a high-performance gateway device that considers future scalability were proposed.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.203-210
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• 2015

The ecological environment monitoring system configured with Sensor Node, Gateway, Service Platform, and Web Browser. In this paper, we designed gateway resource tree and service function to do handling in the ecological environment monitoring service. Gateway Service Function based on oneM2M Common Service Function, Gateway Resource Tree configured with Application Part handling Sensor Data and Gateway link handling. lastly Device Registration, Sensing, Control, Profile Management.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.230-233
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• 2011

In this paper, highly-efficient optical gating in a junction device based on vanadium dioxide($VO_2$) thin film grown by a sol-gel method was investigated as a gate terminal of a three-terminal device using infrared light with a wavelength of ~1554.6 nm. Due to the photoinduced phase transition, the threshold voltage of the $VO_2$ junction device, at which the device current abruptly jumps, could be tuned with a sensitivity of ~96.5 V/W by adjusting the optical power of the infrared light directly illuminating the device. Compared with the tuning efficiency of the previous device fabricated using $VO_2$ thin film deposited by a pulsed laser deposition method, the threshold voltage of this device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which is ~4.9 times larger than the previous device.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.568-577
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• 2014

We consider a mobile content delivery network (mCDN) in which special mobile devices designated as caching servers (caching-server device: CSD) can provide mobile stations with popular contents on demand via device-to-device (D2D) communication links. On the assumption that mobile CSD's are randomly distributed by a Poisson point process (PPP), an optimization problem is formulated to determine the probability of storing the individual content in each server in a manner that minimizes the average caching failure rate. Further, we present a low-complexity search algorithm, optimum dual-solution searching algorithm (ODSA), for solving this optimization problem. We demonstrate that the proposed ODSA takes fewer iterations, on the order of O(log N) searches, for caching N contents in the system to find the optimal solution, as compared to the number of iterations in the conventional subgradient method, with an acceptable accuracy in practice. Furthermore, we identify the important characteristics of the optimal caching policies in the mobile environment that would serve as a useful aid in designing the mCDN.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.751-754
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• 2003

Metamorphic HEMTs (MHEMTs) have emerged as excellent challenges for the design and fabrication of high-speed HEMTs for millimeter-wave applications. Some of improvements result from improved mobility and larger conduction band discontinuity in the channel, leading to more efficient modulation doping, better confinement, and better device performance compared with pseudomorphic HEMTs. We have studied the calibration on the DC and RF characteristics of the MHEMT device using I $n_{0.53}$G $a_{0.47}$As/I $n_{0.52}$A1$_{0.48}$As modulation-doped heterostructure on the GaAs wafer. For the optimized device performance simulation, we calibrated the device performance of 0.1-${\mu}{\textrm}{m}$ $\Gamma$-gate MHEMT fabricated in our research center using the 2D ISE-DESSIS device simulator. With this calibrated parameter set, we have obtained very good reproducibility. The device simulation on the DC and RF characteristics exhibits good reproducibility for our 0.1-${\mu}{\textrm}{m}$ -gate MHEMT device compared with the measurements. We expect that our calibration result can help design over-100-GHz MHEMT devices for better device performance.ormance.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.291-296
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• 2019

Nuclear medicine have often used to diagnose cancers. The main absorbed dose from radiation to a radiation worker resulted from open radioisotopes. Methods for reducing the radiation dose to a radiation worker from radioisotopes injected to patients were studied. The shield device of 0.2 mmPb was manufactured as a size of $300mm{\times}500mm{\times}150mm$. By using dosimeters of Nanodot, the absorbed doses for thyroid, chest and genital organ were measured with and without a shielding device and with syringe shield and shielding device together. The highest absorbed dose of 0.908 mGy reduction of 20.8% as 0.719 mGy was in the genital organ by using the syringe shield and a shielding device together. A effective dose for a radiation worker during 1 year was expected to 1.223 mSv at the chest, which was decrease as 0.994 mSv by shielding device and syringe shield together. When open radioisotope is injected to a patient for examination, the only use of a shielding device results in the reduction of radiation dose to radiation workers.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.6
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• pp.600-607
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• 2006

For the effective operation of manufacturing system, FMS(Flexible Manufacturing System) and CIM(Computer Integrated Manufacturing) system are developed. In these systems, a machine tool is the target of integration in last 3 decades. In nowadays, the conventional concept of machine tools is changing to the autonomous manufacturing device based on knowledge-evolution through applying advanced information technology in which open architecture controller, high speed network and internet technology are contained. In this environment, a machine tool is not the target of integration but the subject of cooperation. In the future, a machine tool will be more improved in the form of a knowledge-evolution based device. In order to develop the knowledge-evolution based machine tools, this paper proposes the structure of knowledge evolution in M2M(Machine To Machine) and the scheme of a dialogue agent among agent-based modules such as a sensory module, a dialogue module, and an expert system. The dialogue agent has a role of interfacing with another machine for cooperation. To design the dialogue agent module in M2M environment, FIPA-OS and ping agent based on FIPA-OS are analyzed in this study. Through this, it is expected that the dialogue agent module can be more efficiently designed and the knowledge-evolution based machine tools can be hereafter more easily implemented.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1407-1410
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• 2007

This work reports on three primary color fluorescent white organic light emitting diode (WOLED) with simple device structure where only a part of the hole transporting layer was doped with dye. The maximum luminance of the device reaches $35000\;cd/m^2$ at a drive voltage below 11V and external quantum efficiency of the device is above 1% in the wide range of luminance from 10 to $35000\;cd/m^2$ and reaches its highest 1.6% at $500\;cd/m^2$. The chromaticity coordinate shift of the device is negligible in this wide range of luminance. The blue shift of emission color with an increase of current density was attributed to the narrowing of recombination zone width with raise of current density.