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Kim Y.-H.,Korea Electrotechnology Research Institute
IEEE Transactions on Power Delivery | Year: 2010

We propose a multipath parameter estimation scheme for power-line communication (PLC) channel modeling. In the proposed scheme, we introduce a time-delay estimation scheme and an attenuation factor estimation scheme to analyze multipath parameters. For the time-delay estimation scheme, we employ the generalized eigenvalues utilizing signal subspace eigenvectors (GEESE) algorithm using frequency-domain channel measurements. Before the GEESE algorithm is used, spatial smoothing methods are applied to resolve the different paths in PLC channels. To estimate the attenuation factors, we derive a least-square estimator. Simulation results with theoretical channel models and experimental channel measurements show that the proposed scheme accurately estimates multipath parameters for PLC channel modeling. © 2010 IEEE. Source

Baeg K.-J.,Korea Electrotechnology Research Institute | Caironi M.,Italian Institute of Technology | Noh Y.-Y.,Dongguk University
Advanced Materials | Year: 2013

For at least the past ten years printed electronics has promised to revolutionize our daily life by making cost-effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point-of-care applications. While passive components, such as conductors, resistors and capacitors, had already been fabricated by printing techniques at industrial scale, printing processes have been struggling to meet the requirements for mass-produced electronics and optoelectronics applications despite their great potential. In the case of logic integrated circuits (ICs), which constitute the focus of this Progress Report, the main limitations have been represented by the need of suitable functional inks, mainly high-mobility printable semiconductors and low sintering temperature conducting inks, and evoluted printing tools capable of higher resolution, registration and uniformity than needed in the conventional graphic arts printing sector. Solution-processable polymeric semiconductors are the best candidates to fulfill the requirements for printed logic ICs on flexible substrates, due to their superior processability, ease of tuning of their rheology parameters, and mechanical properties. One of the strongest limitations has been mainly represented by the low charge carrier mobility (μ) achievable with polymeric, organic field-effect transistors (OFETs). However, recently unprecedented values of μ ∼ 10 cm2/Vs have been achieved with solution-processed polymer based OFETs, a value competing with mobilities reported in organic single-crystals and exceeding the performances enabled by amorphous silicon (a-Si). Interestingly these values were achieved thanks to the design and synthesis of donor-acceptor copolymers, showing limited degree of order when processed in thin films and therefore fostering further studies on the reason leading to such improved charge transport properties. Among this class of materials, various polymers can show well balanced electrons and holes mobility, therefore being indicated as ambipolar semiconductors, good environmental stability, and a small band-gap, which simplifies the tuning of charge injection. This opened up the possibility of taking advantage of the superior performances offered by complementary "CMOS-like" logic for the design of digital ICs, easing the scaling down of critical geometrical features, and achieving higher complexity from robust single gates (e.g., inverters) and test circuits (e.g., ring oscillators) to more complete circuits. Here, we review the recent progress in the development of printed ICs based on polymeric semiconductors suitable for large-volume micro- and nano-electronics applications. Particular attention is paid to the strategies proposed in the literature to design and synthesize high mobility polymers and to develop suitable printing tools and techniques to allow for improved patterning capability required for the down-scaling of devices in order to achieve the operation frequencies needed for applications, such as flexible radio-frequency identification (RFID) tags, near-field communication (NFC) devices, ambient electronics, and portable flexible displays. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Jung J.-H.,Korea Electrotechnology Research Institute
IEEE Transactions on Power Electronics | Year: 2012

A feed-forward frequency compensator for an asymmetrical pulsewidth modulated (APWM) half-bridge (HB) flyback converter is proposed to increase its power conversion efficiency. Under a variable input voltage, the APWM HB flyback converter cannot be satisfied with the zero-current switching (ZCS) condition of output rectifiers because the variation of the turn-ON duration of main switches, which regulate the output voltage, induces their improper turn-OFF duration. This means that the resonance of a primary current during the turn-OFF of the switches is out of the ZCS operation of the output rectifiers. To avoid this improper operation, the resonant network should be designed with a marginal turn-OFF duration that guarantees the ZCS. However, this makes the converter operate with poor efficiency because of increasing conduction losses. The proposed feed-forward frequency compensator can properly change the converters operating frequency to reduce the conduction losses according to the variation of the input voltage satisfying the ZCS condition of the output rectifiers. Operation principles, steady-state analysis, and soft-switching conditions are analyzed to derive the frequency compensation algorithm of the APWM HB flyback converter. Experimental results using a 240-W prototype converter show that the proposed compensation algorithm can improve the power conversion efficiency of the APWM HB flyback converter under the input-voltage variation. © 2011 IEEE. Source

Kowalski D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kim D.,Korea Electrotechnology Research Institute | Schmuki P.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schmuki P.,King Abdullaziz University
Nano Today | Year: 2013

Anodization of valve metals and alloys is a powerful tool to control nanoscale architecture for many metal oxides. Except for aluminum, the most explored system is self-organized oxide formed on titanium, namely self-organized TiO2 nanotubes, because of the unique combination of geometry with the semiconductive nature of titania that is applicable in photocatalysis, light harvesting systems, electrochromic devices, batteries, matrices, templates, filtration membranes, and bio-compatible materials. In this contribution, we review recent advances in the formation of nanostructured oxides in the form of nanotubes, nanopores with a through-hole morphology, mesosponges, nanochannels and microcones grown on Ti, Nb, Ta, Zr, Hf, W, V and their alloys. We discuss mechanisms of their formation, key functional features, and describe their applications in various fields of chemistry and electrochemistry. Source

Korea Electrotechnology Research Institute | Date: 2015-04-01

Provided is a reflection detection type measurement apparatus for skin fluorescence. The apparatus includes: a first light source irradiating excitation light on a measurement target; a second light source irradiating light of a wavelength different from that of light from the first light source on the measurement target; a first optical detector detecting a reflected light generated from the measurement target due to the excitation light of the first light source; and a second optical detector detecting a skin fluorescence generated from the measurement target due to the excitation light of the first light source, and detecting a reflected light generated from the measurement target due to the excitation light of the second light source. The first optical detector is disposed in an area other than a total reflection area to which the excitation light of the first light source is reflected after irradiating to the measurement target.

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