• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.36-41
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• 2016

Visible Light Communication (VLC) using Light Emitting Diodes (LEDs) within the existing lighting infrastructure can reduce the implementation cost and may gain higher throughput than radio frequency (RF) or Infrared (IR) based wireless systems. Current indoor VLC systems may suffer from poor downlink resource allocation problems and small system throughput. To address these two issues, we propose an algorithm called a conflict graph scheduling (CGS) algorithm, including a conflict graph and a scheme that is based on the conflict graph. The conflict graph can ensure that users are able to transmit data without interference. The scheme considers the user fairness and system throughput, so that they both can get optimum values. Simulation results show that the proposed algorithm can guarantee significant improvement of system throughput under the premise of fairness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.4
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• pp.194-208
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• 2008

In this paper, a multiple-input-multiple-output (MIMO) hybrid-automatic repeat request (HARQ) algorithm with antenna scheduling is proposed. It retransmits the packet using scheduled transmit antennas according to the state of the communication link, instead of retransmitting the packet via the same antennas. As a result, a combination of conventional HARQ systems, viz. chase combining (CC) and incremental redundancy (IR) are used to achieve better performance and lower redundancy. The proposed MIMO-OFDM HARQ system with antenna scheduling is shown to be superior to conventional MIMO HARQ systems, due to its spatial diversity gain.

• Rapid Communication in Photoscience
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• v.2 no.1
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• pp.24-27
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• 2013

A polymeric photobase generator containing oxime-urethane groups is applied to a fluorescence micropatterning material. Polymer bearing oxime-urethane groups was prepared by copolymerization of methyl methacrylate with methacryloyloxyethyl benzophenoneoxime urethane (MBU). The reaction of amino groups in the irradiated copolymer film with dansyl chloride (Dns-Cl) was monitored by using UV absorption, IR absorption and fluorescence spectroscopy. The fluorescence spectrum of the Dns-Cl-treated irradiated copolymer film shows a strong fluorescence with a fluorescence maximum wavelength at 510 nm. A blue fluorescent micropattern with a line width of $2{\sim}3{\mu}m$ was obtained. Treatment of the irradiated copolymer film with Dns-Cl and rhodamine B mixture led to the formation of green, red, and orange-colored fluorescence micropatterns. Thus, various colored micropatterns on a single polymer film can be obtained by selective excitation of each dye molecules.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.406-406
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• 2000

In this study, as a part developing an unmanned container terminal (UCT), Ive designed and implemented an Autonomous Ground Vehicle (AGV) that can deliver containers in the port fast and safely as they are scheduled. It is preferable to research the intelligent UCT/AGV for delivering containers all day long without causing any trouble. For the sake of safe and fast AGV driving, we implemented a multiple-sensor system with vision, ultrasonic, and IR sensors and we adapted the hight-speed wireless LAN that satisfies the IEEE 802.11 Standard for hi-directional communication between the main processor in AGV and a host computer. The Pentium-III processor board mounted on the bottom frame in AGV combines and computes the information from sensors and controls the AGV driving. There are also the 80C196KC micro-controllers to control the actuating and steering motors. In addition, a steering function that is defined newly in this paper is heavily concerned in the mechanical design, and it plays an important role when AGV moves along a curve. Experimental results show the fast and safe delivery operations are possible with this UCT/AGV

• Rapid Communication in Photoscience
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• v.1 no.2
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• pp.27-29
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• 2012

Noble diamine monomers containing thiophene moiety were prepared, such as 2,5'''-diamino-2, 2':5', 2'':5'', 2'''-quaterthiophene (4TDA) and 2, 5'''''-diamino-3'', 4'''-dihexyl-2,2':5', 2'':5'', 2''':5''', 2'''':5'''', 2'''''-sexithiophene (6TDA). Then, these monomers were utilized to prepare polyimides with 3,6-diphenylpromellitic dianhydride (DPPMDA), 3,6-di(4'-trifluoro-methylphenyl) pyromellitic dianhydride (6FPMDA) or 3,6-di(3',5'-bis (trifluoromethyl)phenyl) pyromellitic dianhydride (12FPMDA) via a conventional two-step process. The polyimides were characterized by FT-IR, TGA and DSC, and then subjected CV, UV-vis and PL measurements. The polyimides containing thiophene moiety exhibited high glass transition temperatures ($280{\sim}310^{\circ}C$) and excellent thermal stability (> $420^{\circ}C$) in air as well as green emission (535~586 nm).

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.1
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• pp.90-95
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• 2010

This paper describes the development of integrated head and eye tracker system. Vision based head tracker is performed and it has 7mm error in 300mm translation. The epi-polar method and point matching are used for determining a position of head and rotational degree. High brightness LEDs are installed on helmet and the installed pattern is very important to match the points of stereo system. Eye tracker also uses LED for constant illumination. A Position of gazed object(3m distance) is determined by pupil tracking and eye tracker has 1~5 pixel error. Integration of result data of each tracking system is important. RS-232C communication is applied to integrated system and triggering signal is used for synchronization.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.415-424
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• 2016

This paper describes a high data rate proximity transmitter design for high resolution smartphone-mirrored display applications. A 2 Gb/s transmitter is designed with a low transmission power of -70 dBm/MHz and a wide bandwidth of nearly 3 GHz. A digital pre-correction method is employed in the transmitter to mitigate the inter-symbol interference problem. A carrier-based digital pulse shaping and a reconfigurable digital envelope generation methods are employed for robust operation by utilizing 20 phases from a 2 GHz phase-locked loop. A 6.5-9.5 GHz transmitter implemented in 65 nm CMOS achieves the maximum data rate of 2 Gb/s, consuming only 7.6 mW from a 1 V supply.

• ETRI Journal
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• v.27 no.4
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• pp.449-452
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• 2005

The electrical characteristics of solid state devices such as the bipolar junction transistor (BJT), metal-oxide semiconductor field-effect transistor (MOSFET), and other active devices are altered by impinging photon radiation and temperature in the space environment. In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for two kinds of MOSFETs (200 V and 100 V of $V_{DSS}$) are tested for ${\gamma}-irradiation$ and compared with the electrical specifications under the pre- and post-irradiation low dose rates of 4.97 and 9.55 rad/s as well as at a maximum total dose of 30 krad. In our experiment, the ${\gamma}-radiation$ facility using a low dose, available at Korea Atomic Energy Research Institute (KAERI), has been applied on two commercially available International Rectifier (IR) products, IRFP250 and IRF540.

• Journal of Korean Port Research
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• v.14 no.2
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• pp.199-207
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• 2000

In this study, as the preliminary step for developing an unmanned vehicle to deliver a container-box, we designed and implemented Automatic Guided Vehicle(AGV) Simulator for the purpose of Port Facilities Automation. It is preferable to research the intelligent AGV for delivery all day long. For complementing AGV simulator driving, we used multiple-sensor systems with vision, ultrasonic, IR and adapted the high-speed wireless LAN that satisfies the IEEE 802.11 Standard for bi-directional communication between main processor in AGV and Host computer. Here, we mounted on bottom frame in AGV Pentium-III processor, which combine and compute the information from each sensor system and control the AGV driving, and used the 80C196KC micro-controller to control the actuating and steering motors.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.33-38
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• 2004

To investigate the reliability of the MTJs on the roughness of insulating tunnel barrier, we prepared two MTJs with the different uniformity of barrier thickness. Namely, the one has uniform insulating barrier thickness; the other has non-uniform insulating barrier thickness as compared to different thing. As to depositing amorphous layer CoZrNb under the pinning layer IrMn, we achieved MTJ with uniform barrier thickness. Toinvestigate the reliability of the MTJs dependent on the bottom electrode, time-dependent dielectric breakdown (TDDB) measurements were carried out under constant voltage stress. The Weibull fit of out data shows clearly that $t_{BD}$ scales with the thickness uniformity of MTJs tunnel barrier. Assuming a linear dependence of log($t_{BD}$) on stress voltages, we obtained the lifetime of $10^4$years at a operating voltage of 0.4 V at MTJs comprising CoNbZr layers. This study shows that the reliabilityof new MTJs structure was improved due to the ultra smooth barrier, because the surface roughness of the bottom electrode influenced the uniformity of tunnel barrier.