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Effect of LSP in Phosphor-Converted WLEDs by Application of Ag NPs With/Without Silica Shell
Kim, Myeongcheol,Shin, Jeong Bin,Choi, Kyung Cheol IEEE 2016 Photonics Technology Letters Vol.28 No.17
<P>We report improved efficiency of a phosphor (Lu3Al5O12: Ce3+) by exploiting the plasmonic effect of silver nanoparticles (Ag NPs) for white light-emitting diodes (WLEDs). In a position close to the Ag NPs, the phosphor leads to higher quantum efficiency. Ag NPs are synthesized in various shapes for different spectral overlaps, and coated with a dielectric material to enhance the localized surface plasmon resonance. We present a new method that can improve the efficiency of WLEDs at appropriate concentrations of Ag NPs.</P>
Kim, Myeongcheol,Choi, Kyung Cheol IEEE 2017 IEEE transactions on electron devices Vol.64 No.8
<P>We report a transparent and flexible resistive random access memory (ReRAM) using a multi-thin-layer electrode. The transparent and flexible ReRAM includes a multi-thin-layerelectrodethat is transparentand flexible and an Al2O3 layer as a transparent oxide material. When the multi-thin-layer electrode is used for the top and bottom electrode for the ReRAM, the ReRAM has transparent and flexible properties. The stable memory operation uses a Ti layer and an MgO layer between the Al2O3 layer andmultithin- layer electrodes. The transmittance of the ReRAM is over 70% at a visible wavelength on a PET substrate. We believe this transparent and flexible ReRAM will be useful for transparent and flexible electronic devices in the future.</P>
An Efficient Multimode Quantized Precoding Technique for MIMO Wireless Systems
Myeongcheol Shin,Sangheon Kim,Jiwon Kang,Lee, C. IEEE 2009 IEEE Transactions on Vehicular Technology VT Vol.58 No.2
<P>Multimode quantized precoding (QP) can provide full diversity gain or high capacity gain by adapting the number of substreams, as well as the precoding matrix, according to the instantaneous channel condition with low-rate feedback. Conventional multimode QP (MM-QP), however, does not consider the adaptive rate allocation among substreams; thus, it cannot have the additional gain by adaptive modulation. Furthermore, it is computationally complex since exhaustive matrix inversions are required to determine the optimal mode. In this paper, we propose an efficient MM-QP system that improves the performance of a conventional system in terms of error rate and has a lower computational complexity than the conventional system. First, we define the rate-partitioning vector as the mode and control the rate among substreams and the number of substreams according to the channel instantaneous condition. Second, to reduce the computational complexity for the receiver to determine the optimal mode, the simplified mode-selection technique using estimates of the modal metric is proposed. In the proposed mode-selection technique, the optimal mode can be obtained by several multiplication and division operations. Finally, the mode-reduction technique eliminating the less-frequently used modes is proposed, which leads to a significant reduction of the feedback information with negligible performance loss. In numerical experiments, it was verified that the proposed MM-QP system gives a better error-rate performance than the conventional system, with much less computational complexity for the same amount of feedback information.</P>
Heonyoung Kim,Myeongcheol Kang,황문영,강래형,Chulmin Joo,Donghoon Kang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.1
Gravel scattering, which occurs from snow-ice that develops on trains during winter, is a major cause of damage to train parts. An exothermic technology that uses copper wires to solve the problem of gravel scattering is ineffective on the snow-ice produced on the surface of the trains. Therefore, studies have been conducted to overcome the weaknesses of the conventional methods and to develop a paint-type surface exothermic technology that can be efficiently applied to complicated structures. However, multi-layered paint-type coatings can lead to problems such as a delamination or exfoliation of the layers when used for a long period of time within an environment undergoing variations in temperature. Therefore, this study assesses the long-term effects of temperature on multi-layered exothermic coating technology based on nano-solutions for an application of self-heating function on railway infrastructures. To do so, we developed an exothermic coating test specimen using the paint applied to train cars and commercial nano-solutions. To conduct an experiment on accelerated aging, the specimen was subjected to regular changes in the temperature within a thermal chamber. The results revealed that there is a nonlinear decline in the performance as the specimen is worn out in comparison to the exothermic performance achieved during the early stages. Further, it is possible to identify the structural causes of the decline in performance from the specimen applied thermal load by analyzing the morphology. However, it is possible to observe a high stability from noninvasive overheating or short-circuits based on the structural changes to the coating, which are observed during the assessment of the exothermic uniformity. Therefore, it can be concluded that a multi-layer exothermic coating, which can be effectively applied as an exothermic technology based on self-heating surfaces, can be applied for a long period to prevent disasters from freezing or snow-ice in trains during winter.
Quantized Precoding Techniques for Spatially Correlated Channels without Correlation Feedback
Myoung-Seok Kim,Myeongcheol Shin,Wonwoo Park,Chungyong Lee 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
This thesis deals with the quantized precoding techniques for spatially correlated MISO (multiple-input single-output) channels. The transformed codebook, which has been proposed recently for correlated channel, has problem of loosing diversity despite using additional feedback for channel correlation matrix. In this thesis, an efficient algorithm to estimate the correlation matrix without additional feedback and also prevent diversity loss is proposed. In the proposed algorithm, the estimation can be done using the codeword selection patterns. In order to estimate and get SNR gain simultaneously, the proposed algorithm uses both transformed codebook and specific forms of IID (independent identically distributed) codebook for estimation, which also prevents diversity loss.