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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, Yoonjung,Choi, Jin-Ha,Liu, Lichun,Oh, Byung-Keun,Park, Sungho American Chemical Society 2013 Chemistry of materials Vol.25 No.6
<P>In this work, we tested multiblock nanorods (NRs) with Au and Ag segments for the surface plasmonic detection of dopamine (DA). A change in the quadrupole surface plasmon mode was found to be sensitive to the Au/Ag block length and relative block ratio in a single NR. The surfaces of the NRs were decorated with monoclonal antibody (Mab) against DA. By comparing the results for pure Au NRs with those obtained for multiblock Au–Ag–Au NRs, we found that the magnitude of peak-shifting for the multiblock NRs was much larger than that for pure Au NRs. This result was attributed to the higher sensitivity of Ag to a change in the dielectric constant of the surrounding medium when compared to Au and the sensitive surface plasmon coupling at the junction between Au and Ag blocks. The magnitude of peak-shifting was tuned as a function of both the length of the Ag block and the number of repeating units of Au and Ag in the NRs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-6/cm304030r/production/images/medium/cm-2012-04030r_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm304030r'>ACS Electronic Supporting Info</A></P>
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>
Choi, Sungho,Yun, Young Jun,Kim, Sue Jin,Jung, Ha-Kyun Optical Society of America 2013 Optics letters Vol.38 No.8
<P>Eu(2+) and Mn(2+) codoped, white-emitting Na(Sr,Ba)PO(4) phosphors are prepared, and their emission properties, especially for thermal stability, are thoroughly investigated. The thermal quenching and Eu(2+)/Mn(2+) energy transfer efficiency are totally different in the ratio of alkaline earth metals in host composition, NaBaPO(4), Na(Sr(0.5)Ba(0.5))PO(4), and NaSrPO(4), respectively. Furthermore, by using near-ultraviolet light-emitting diodes (LEDs) and the corresponding Na(Sr(0.5)Ba(0.5))PO(4):Eu(2+), Mn(2+) phosphor as light converters, we demonstrate a bright and thermally stable white-emitting LED. The resultant LED exhibits a warm white light [~4900 K, CIE coordinates of (0.33, 0.31)] with excellent thermal and hydrolytic stabilities comparable to those of commercially available ones, Y(3)Al(5)O(12):Ce(3+) and BaMg(2)Al(16)O(27):Eu(2+). The proposed composition, with its efficient energy transfer, could enable Eu(2+) and Mn(2+) codoped Na(Sr,Ba)PO(4) to be a promising single component phosphor for cost-effective white-emitting LEDs.</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.
Sungho Choi,Sangmin Kim,Kyung-Young Jhang 한국비파괴검사학회 2019 한국비파괴검사학회지 Vol.39 No.3
The synthetic aperture focusing technique (SAFT) can be easily adapted to laser ultrasonic testing and can improve the signal-to-noise ratio (SNR) of laser ultrasonic images, to enhance defect detectability. In this study, the imaging and sizing of surface defects were carried out when SAFT was adopted for laser-generated surface waves. Six different surface breaking notches were made on an aluminum plate and were visualized using a laser ultrasonic scanning system consisting of a pulsed laser for ultrasonic generation and a laser interferometer for ultrasonic reception. B-scan images and SAFT-processed images for the six different notches were compared, which highlighted the advantages of the SAFT post-processing compared to B-scan imaging. A methodology to size the defects in SAFT-processed images was also proposed. The methodology utilizes the linear relationship between the suitable threshold decibel value, which determines the exact defect length with the use of an amplitude-drop method, along with the SNR of the defect echo in the SAFT-processed images. The experimental results demonstrate that the estimated defect lengths are similar to actual defect lengths, which showing that the proposed methodology can be effectively used for sizing of surface defects in SAFT-processed images.