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Tuyen Quang Le,이광수,박진순,고진환 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
In this study, flow-driven rotor simulations with a given load are conducted to analyze the operational characteristics of a vertical-axis Darrieus turbine, specifically its self-starting capability and fluctuations in its torque as well as the RPM. These characteristics are typically observed in experiments, though they cannot be acquired in simula-tions with a given tip speed ratio (TSR). First, it is shown that a flow-driven rotor simulation with a two-dimensional (2D) turbine model obtains power coefficients with curves similar to those obtained in a simulation with a given TSR. 3D flow-driven rotor simulations with an optimal geometry then show that a helical-bladed turbine has the following prominent advantages over a straight-bladed turbine of the same size: an improvement of its self-starting capabilities and reduced fluctuations in its torque and RPM curves as well as an increase in its power coefficient from 33% to 42%. Therefore, it is clear that a flow-driven rotor simulation provides more information for the design of a Darrieus turbine than a simula-tion with a given TSR before experiments.
Carrier Phase-Shift PWM to Reduce Common-Mode Voltage for Three-Level T-Type NPC Inverters
Tuyen D. Nguyen,Dzung Quoc Phan,Dat Ngoc Dao,Hong-Hee Lee 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6
Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.
Synthesis and Antiinflammatory Activity of 1,5-Diarylimidazoles
Tuyen Truong Ngoc,Sin Kwang-Seog,Kim Hyun Pyo,Park Haeil The Pharmaceutical Society of Korea 2005 Archives of Pharmacal Research Vol.28 No.9
A number of 1,5-diarylimidazoles has been synthesized and evaluated for their inhibitory activities of COX-2 catalyzed $PGE_2$ production. 1,5-Diarylimidazoles were obtained from imimes and p-toluenesulfonylmethyl cyanide (TosMIC). Imines were prepared from commercially available amines and aldehydes. Among the compounds tested, 1-(2,4-difluorophenyl)-5-(4methylsulfonylphenyl)imidazole (2r) showed strong inhibitory activity, however, most diarylimidazoles exhibited little to low inhibitory activities against COX-2 catalyzed $PGE_2$ production.
A proposed biosynthesis pathway of minor ginsenosides from red ginseng residue
Tuyen Thi My Nguyen,Dong Hyun Jang,Sang ManYoun,Jong Tae Park,Jae Han Kim 한국당과학회 2018 한국당과학회 학술대회 Vol.2018 No.07
Minor ginsenosides, those have low content in white or red ginseng, are proved to have strong pharmaceutical activities in literature. There are many minor ginsenosides can be formed during transformation in various pathways. In which, the biotransformation pathway of Rb2→Rd→F2→C-K or Rc, Rbl, Rb2→Rg3→Rh2 by using various bacteria, yeast, and fungus was well-known. However, the other pathway that converts Rb2→C-0→C-Y→C-K or Rc→C-Mc→C-K were seldom occurred. In this study, utilization of red ginseng residue (RGR), a byproduct of red ginseng extraction, for minor ginsenoside production by using enzyme cellulose, hemicellulase, and lactic acid fermentation was performed. Biotransformation of ginsenosides was analyzed by UPLC-UV /EIS-QQQ mass spectrometry. During enzymatic reaction and lactic acid fermentation, the relative abundance of ginsenoside Rbl, Rg3, Rb2, and Rc were decreased while a significant increase in rare ginsenoside F2, Rh2 , C-K, C-0, and C-Mc were obtained. Our results suggested that combination of cell wall degrading enzyme and metabolism of lactic acid bacteria (LPlantarium and LLactis) could remove glucosyl moieties from ginsenosides. Particularly, C-0, C-Mc could be obtained during enzymatic treatment and lactic acid fermentation. This method could be applied for production of C-0, C-Mc, and C-K from RGR. For further research, this result may open a new direction toward RGR utilization for minor ginsenosides.
Tuyen, N.V.,Ryu, J.H.,Yae, J.B.,Kim, H.G.,Hong, S.W.,Ahn, D.H. Elsevier 2018 Journal of industrial and engineering chemistry Vol.67 No.-
<P><B>Abstract</B></P> <P>In this study, the result shows that polyvinyl alcohol–sodium alginate (PVA–SA) gel bead crosslinked with sodium sulfate are better among the different methods by comparing the relative mechanical strength, mechanical strength swelling and expansion coefficient of beads in water. Subsequently, anammox biomass entrapment by PVA–SA gel was introduced into continuous stirred tank reactor (CSTR). After 24 operation days, the nitrogen removal efficiency achieved 60%, while the nitrogen loading rate (NLR) was 0.14kgN/m<SUP>3</SUP>/d and the experiment data indicated that PVA–SA gel bead crosslinked with sodium sulfate can be used to initiate anammox process. Furthermore, it is an alternative for culturing anammox in a long-term operation.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Tuyen Danh Pham ),( Gi Pyo Nam ),( Kwang Yong Shin ),( Kang Ryoung Park ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.7
The increase in the number of music files in smart phone and MP3 player makes it difficult to find the music files which people want. So, Query-by-Singing/Humming (QbSH) systems have been developed to retrieve music from a user`s humming or singing without having to know detailed information about the title or singer of song. Most previous researches on QbSH have been conducted using musical instrument digital interface (MIDI) files as reference songs. However, the production of MIDI files is a time-consuming process. In addition, more and more music files are newly published with the development of music market. Consequently, the method of using the more common MPEG-1 audio layer 3 (MP3) files for reference songs is considered as an alternative. However, there is little previous research on QbSH with MP3 files because an MP3 file has a different waveform due to background music and multiple (polyphonic) melodies compared to the humming/singing query. To overcome these problems, we propose a new QbSH method using MP3 files on mobile device. This research is novel in four ways. First, this is the first research on QbSH using MP3 files as reference songs. Second, the start and end positions on the MP3 file to be matched are estimated by using multi-layered perceptron (MLP) prior to performing the matching with humming/singing query file. Third, for more accurate results, four MLPs are used, which produce the start and end positions for dynamic time warping (DTW) matching algorithm, and those for chroma-based DTW algorithm, respectively. Fourth, two matching scores by the DTW and chroma-based DTW algorithms are combined by using PRODUCT rule, through which a higher matching accuracy is obtained. Experimental results with AFA MP3 database show that the accuracy (Top 1 accuracy of 98%, with an MRR of 0.989) of the proposed method is much higher than that of other methods. We also showed the effectiveness of the proposed system on consumer mobile device.
Effects of pretreatment and air drying temperature on Noni fruit powder
Tuyen Chan Kha,Cong Thanh Nguyen,Luyen Thi Tran,Trung Tan Truong 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.12
The plant Morinda citrifolia L. (Noni) has beenthe subject of several recent research due to its positiveimpact on the treatment and prevention of a variety ofdiseases. Noni fruits contain a variety of phytochemicals,including flavonoid, polyphenol, and triterpenoid saponin. This study aimed to determine the best pre-treatment (includingblanching, soaking in ascorbic acid solution andmetabisulfite solution) and air-drying temperature (50, 60,70, and 80 C) to maximize the total polyphenol content(TPC), flavonoid content (TFC), and triterpenoid saponincontents (TSC) of the resultant Noni fruit powder. Theresults revealed that pre-soaked Noni fruit samples inascorbic acid or metabisulfite solution before air-drying at60 C were beneficial in preserving TPC, TFC, and TSC. TPC, TFC, and TSC losses increased as drying temperatures(70 and 80 C) rose. The optimum sample was held atfive different relative humidity conditions until theyattained weight equilibrium. The results indicated that thesorption isotherm curve of the Noni powder was the sigmoidshape and fitted with the BET and GAB models.
SVPWM Strategies for Three-level T-type Neutral-point-clamped Indirect Matrix Converter
Tuyen, Nguyen Dinh,Phuong, Le Minh,Lee, Hong-Hee The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4
In this paper, the three-level T-type neutral-point-clamped indirect matrix converter topology and the relative space vector modulation methods are introduced to improve the voltage transfer ratio and output voltage performance. The presented converter topology is based on combinations of cascaded-rectifier and three-level T-type neutral-point-clamp inverter. It can overcome the limitation of voltage transfer ratio of the conventional matrix converter and the high voltage rating of power switches of conventional matrix converter. Two SVPWM strategies for proposed converter are described in this paper to achieve the advantages features such as: sinusoidal input/output currents and three-level output voltage waveforms. Results from Psim 9.0 software simulation are provided to confirm the theoretical analysis. Hence, a laboratory prototype was implemented, and the experimental results are shown to validate the simulation results and to verify the effectiveness of the proposed topology and modulation strategies.