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Introduction of Mobile-based Interactive Identification Key
Suwon Chun,Sungho Choi,Won-Young Choi,Yang-Seop Bae 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.04
Species identification, the process of finding the taxon to which a specimen belongs, is a difficult and frustrating task for most biologists but is absolutely fundamental to most biological research. However, proper species identification requires extensive knowledge on the particular taxon, thus can be problematic and confusing for non-professionals. To increase the accuracy of identification, computer-based interactive identification key has been widely used. In order to improve the identification process and promote effective utilization of Korean species, Korean Indigenous Interactive Key System (KIIS) was developed. Moreover, image-based online identification system was developed to broaden the range of users from non-experts to professionals. As the use of mobile device became significant in people’s lives, we further developed mobile web-based identification system.
Choi, Sungho,Jhang, Kyung-Young The Korean Society for Nondestructive Testing 2013 한국비파괴검사학회지 Vol.33 No.3
Acoustic nonlinearity of surface waves is an effective method to evaluate the micro damage on the surface of materials. In this method, the $A_1$ (magnitude of the fundamental wave) and $A_2$ (magnitude of the second-order harmonic wave) are measured for evaluation of acoustic nonlinearity. However, if there is another source of second-order harmonic wave other than the material itself, the linear relationship between $A_1{^2}$ and $A_2$ will not be guaranteed. Therefore, the second-order harmonic generation by another source should be fully suppressed. In this paper, we investigated the initial second-order harmonic generation in narrowband surface waves by multi-line laser beams. The spatial profile of laser beam was considered in the cases of Gaussian and square-like. The temporal profile was assumed to be Gaussian. In case of Gaussian spatial profile, the generation of the initial second-order harmonic wave was inevitable. However, when the spatial profile was square-like, the generation of the initial second-order harmonic wave was able to be fully suppressed at specific duty ratio. These results mean that the multi-line laser beams of square-like profile with a proper duty ratio are useful to evaluate the acoustic nonlinearity of the generated surface waves.
Optically Assisted Charge Pumping on Floating-Body FETs
Sungho Kim,Sung-Jin Choi,Yang-Kyu Choi IEEE 2010 IEEE electron device letters Vol.31 No.12
<P>An optical charge-pumping (CP) method is proposed to extract the interface trap density in floating-body (FB) field-effect transistors (FETs). Optically generated majority carriers are removed from the FB by applying a burst of charge-pumping pulses to the gate. The change of the drain current after each CP pulse is used to determine the interface trap density. The advantage of this method lies in the possibility to characterize FB FETs without the unnecessary generation of interface traps by measurement bias. In addition, it can be applied to various types of FB devices directly without structural modification.</P>
Digital Predistortion Based on Combined Feedback in MIMO Transmitters
Sungho Choi,Eui-Rim Jeong IEEE 2012 IEEE communications letters Vol.16 No.10
<P>An adaptive digital predistortion (PD) technique is proposed for linearization of power amplifiers (PAs) in multiple-input multiple-output (MIMO) transmitters. Instead of constructing a separate feedback path at each PA, we propose a PD technique based on a combined feedback, which adds all the PAs' outputs to form a single feedback. We develop an algorithm for finding the multiple PA characteristics jointly from the combined feedback. The PD parameters are calculated from the identified PA characteristics. Although the proposed method requires more computations for PA identification than the conventional method, its hardware implementation is much simpler and can overcome the crosstalk problem of a radio frequency (RF) selector, which is necessary for multiple feedback selection. The simulation results show that, despite its simple structure, the linearization performance of the proposed method is almost the same as the separate multiple feedback method.</P>
BaLa2WO7:Eu3+ as a Novel Red-emitting Phosphor for UV LEDs
Sungho Choi,Byung-Yoon Park,정하균,Young-Min Moon 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.1
The luminescence properties of a novel red-emitting phosphor, Eu3+-activated BaLa2WO7, were investigated for application in lighting phosphors. The strong red emission of this compound is centered at 618 nm under excitation of both the charge transfer band and the inner shell f-f transitions of Eu3+ activators. In comparison with the charge-transfer transition of other Eu3+-activated oxides, the Eu3+ ion in BaLa2WO7 has the same coordination number as that of perovskite-structured oxides, such as BaLaLiWO6:Eu3+. Therefore, the characteristic red emission under long-wavelength UV light and the chemical stabilities of rare-earth-activated oxotungstates might be sufficient for their use as luminescent materials for new red phosphors in energy-saving lighting elements such as LEDs.