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Transformation of Ginsenosides Rb2 and Rc from <i>Panax ginseng</i> by Food Microorganisms
Chi, Hyun,Kim, Dong-Hyun,Ji, Geun-Eog Pharmaceutical Society of Japan 2005 BIOLOGICAL & PHARMACEUTICAL BULLETIN Vol.28 No.11
<P>Protopanaxadiol ginsenosides Rb2 and Rc were transformed using cell-free extracts from various edible food microorganisms and then analyzed by TLC and HPLC. Rb2 and Rc were transformed into compound K <I>via</I> Rd and F2 by <I>Bifidobacterium</I> sp. Int57 and <I>Bifidobacterium</I> sp. SJ32. <I>Lactobacillus delbrueckii</I> transformed Rb2 and Rc into ginsenoside Rh2. <I>Bifidobacterium</I> sp. SH5 transformed Rb2 and Rc into F2. <I>Aspergillus niger</I> transformed Rb2 into compound K <I>via</I> compound O and compound Y, whereas it transformed Rc into compound K <I>via</I> Mc. Taken together, these processes would allow a specific bioconversion process to obtain specific ginsenosides using an appropriate combination of ginsenoside substrates and specific microbial enzymes.</P>
Calibration and Uncertainty Analysis of Sample-Time Error on High Jitter of Samplers
Chihyun Cho,Joo-Gwang Lee,Tae-Weon Kang,No-Weon Kang 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.3
In this paper, we propose an estimation method using multiple in-phase and quadrature (IQ) signals of different frequencies to evaluate the sample-time errors in the sampling oscilloscope. The estimator is implemented by ODRPACK, and a novel iteration scheme is applied to achieve fast convergence without any prior information. Monte-Carlo simulation is conducted to confirm the proposed method. It clearly shows that the multiple IQ approach achieves more accurate results compared to the conventional method. Finally, the criteria for the frequency selection and the signal capture time are investigated.
Improved Wheeler Cap Method Based on an Equivalent High-Order Circuit Model
Chihyun Cho,Jin-Seob Kang,Hosung Choo Institute of Electrical and Electronics Engineers 2014 IEEE Transactions on Antennas and Propagation Vol. No.
<P>The conventional Wheeler cap method usually produces accurate radiation efficiency of small antennas when the antennas under test (AUTs) operate as a simple series or a parallel RLC resonance circuit. However, this method often gives unreliable radiation efficiency if the AUT has a complicated operating principle such as circular polarization (CP), multiple resonances, or broad-band properties. In this paper, we propose an improved Wheeler cap method based on the equivalent high-order circuit model including transformers to provide accurate radiation efficiency, although the AUT does not operate as a simple resonance circuit. For building equivalent high-order circuit models, a method for estimating the initial values of a genetic algorithm (GA) is also proposed, which effectively reduces the searching space and improves the convergence of the optimization. To verify the proposed method, we measure the radiation efficiency of a CP microstrip antenna, a UHF RFID tag antenna, and a triple-resonance microstrip antenna.</P>
Design of a Circularly Polarized Tag Antenna for Increased Reading Range
Chihyun Cho,Ikmo Park,Hosung Choo IEEE 2009 IEEE transactions on antennas and propagation Vol.57 No.10
<P>We introduce a novel circularly polarized tag antenna, consisting of a truncated patch, a shorting plate, and a ground plane, to increase the reading range while remaining in compliance with EIRP regulations. The reading range of the proposed tag is twice that of linearly polarized tags, due to the decreased polarization mismatch between the reader and tag antennas. An additional parasitic patch is loaded onto the structure to boost the reading range in the UHF RFID band. As a result, an average reading range of 8 m is achieved between 860 MHz and 960 MHz, compared to a range of about 3 m with conventional dipole tags.</P>
Chihyun Cho,Ikmo Park,Hosung Choo IEEE 2010 IEEE transactions on antennas and propagation Vol.58 No.9
<P>We propose a modified Wheeler cap method to accurately measure the radiation efficiency of patch antennas with multiple resonances by modeling their impedance as a high-order circuit model. The radiation efficiency is obtained from the power consumption ratio between the radiation and loss conductances using a circuit model we developed. Our technique is validated by measuring the efficiencies of a circularly polarized microstrip patch antenna and a triple-band microstrip patch antenna. The measurement results are in close agreement with those produced by simulations, whereas the Wheeler cap method with a series-(or parallel-) resonant circuit model is shown to be unreliable.</P>