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금속폼 DPF의 Clean Filter 성능에 관한 연구
Khai Nguyen(Khai Nguyen),권오채(Oh Chae Kwon),성낙원(Nakwon Sung),조규백(Gyubaek Cho),오권오(Kwonoh Oh),이의성(Euisung Lee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Pressure drops in metallic foam diesel particulate filters (DPFs) were experimentally and computationally studied in order to understand effects of various design parameters on the fundamental clean filter performance. Axial type filters of Nickel-based super alloy (Inconel) foam, which is a new valuable medium for DPFs due to lower cost, higher temperature corrosion, light-weight. ductility and design flexibility compared to conventional honeycomb wall-flow monoliths, were considered for volume flow rates of 500 to 3000 1/min, filter thickness of 25 to 50 ㎜, pore size of 450 to 600 ㎛, and inlet cone angles of 0 to 50. Predicted and measured pressure drops for the various conditions agreed well each other, indicating that the present modeling using a 3-dimensional CFD code combined with a porous media model can provide reliable predictions.
Trong Luan NGUYEN,Nguyen Anh Ngu PHAM,Thi Kim Nhung NGUYEN,Ngoc Khai Vy NGUYEN,Hoang Thang NGO,Tran Thien Ly PHAM 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.2
At present, environmental problems are gradually becoming quite serious because of the expansion of the business scale of companies, factories, and enterprises, and that is also the reason for the global pollution of the world. Green entrepreneurship is playing an increasingly crucial role in influencing people’s intentions, behaviors, and attitudes toward environmental protection through sustainable development. The purpose of this research was to examine the factors affecting university students’ green entrepreneurship levels in Vietnam. To do this, we performed a scientific research survey with 773 students from reputable universities in Vietnam, 337 of whom are male and 436 of whom are female. To assess the reliability and correlation between observed and total variables, this study employs scale testing methods such as Cronbach alpha, EFA, CFA, and SEM. After evaluating the influencing elements, the findings reveal that the Subjective norm factor and the Risk-aversion component are two distinct aspects that influence university students’ green entrepreneurship intentions in Vietnam and of which, the greatest influence is Risk Aversion. Furthermore, the findings revealed that the level of interest in green entrepreneurship is mostly seen by students with university education between the ages of 18–25.
Nguyen Thi Minh Nguyet,Le Van Thang,Nguyen Huu HuyPhuc,Vinh-Dat Vuong,Tran Van Khai,Mai Thanh Phong 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2
MoS2 nanosheets (NS) were directly grown on carbon nanofiber (CF) and employed as electrocatalyst for hydrogen evolutionreaction (HER). The structural, surface morphology and chemical composition of the nanocomposites were characterized byfield emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energydispersiveX-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. XRD and TEM-EDS measurementsshowed that the molybdenum oxide precursor was successfully transferred into MoS2 nanosheets. It was confirmed from FESEMand TEM images that NS was uniformly distribution on surface of the CF. The HR-TEM images disclosed that the NSwas formed perpendicular to surface of CF fibers via the MoS2 layers growth parallel to CF surface which act as interface. The HER current density was about 12 mA cm−2 at catalyst loading of only 60 μg cm−2 at -0.384 V (vs. RHE).
Harmonics Reduction of 6/4 Switched Reluctance Motor by Randomized Turn-on Angle Control
Nguyen Minh Khai,Duck-Shick Shin,Young-Gook Jung,Young-Cheol Lim 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
In this paper a new method using random modulated strategy is described to decrease harmonic spectrum, and thus reduce the emitted acoustical noise of a 6/4 switched reluctance machine. The proposed method is random trigger turn-on angle while turn-off angle is fixed. A Harmonic Spread Factor (HSF) is used to evaluate the random modulation technique. Simulation results show that the high harmonics are reduced significantly. The harmonic intensity of proposed method is better than that of conventional method. The HSF of proposed method can reach at low value.
Z-Source Converter with Maximum Boost Voltage Gain
Nguyen Minh-Khai,Young-Gook Jung(정영국),Young-Cheol Lim(임영철) 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-
This paper proposes a new two-stage Z-source converter (TSZC). The purpose of the proposed system is to obtain the ac voltage with a maximum boost voltage for fuel cell applications as a renewable energy source. In order to provide a continuous current path, a switching strategy for the dc-ac ZSI and ac-ac ZSC of the proposed system was used. The operation principle, analysis and simulation results of 1.2 ㎾ fuel cell stack were also presented.
Nguyen Minh Khai,Duck-Shick Shin,Young-Gook Jung,Young-Cheol Lim 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
This paper describes a new method using random modulated strategies for switched reluctance machines. The proposed method is combined random tum-on, tum-off angle technique and random pulse width modulation technique. The purpose of this proposed method is to decrease harmonic spectrum, and thus reduce the emitted acoustical noise. A random generator is generated by linear congruential generator (LCG) using random pulse position (RPP) scheme. Simulation results show that the harmonic intensity of proposed method is better than that of conventional method.
A NEW SINGLE-PHASE Z-SOURCE CYCLOCONVERTER
NGUYEN MINH KHAI,YOUNG-GOOK JUNG,YOUNG- CHEOL LIM 전력전자학회 2007 전력전자학술대회 논문집 Vol.- No.-
Single-phase cycloconverters are widely used for ac-ac power conversion especially for speed control of ac drives. In this paper, a new single-phase to single-phase Z-source cycloconverter topology is proposed. The proposed singlephase Z-source cycloconverter can boost to a desired voltage with various frequency. Thus, it is called a frequency step-down and amplitude voltage step-up converter. The operating principle of the proposed topology is presented. Analysis and simulation for this single-phase Z-source cycloconverter are also presented.
Bubble formation in globe valve and flow characteristics of partially filled pipe water flow
Nguyen Quang Khai,정광효,Lee Gang Nam,Park Hyun Jung,To Peter,서성부,이재용 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1
Air bubble entrainment is a phenomenon that can significantly reduce the efficiency of liquid motion in piping systems. In the present study, the bubble formation mechanism in a globe valve with 90% water fraction flow is explained by visualization study and pressure oscillation analysis. The shadowgraph imaging technique is applied to illustrate the unsteady flow inside the transparent valve. This helps to study the effect of bubbles induced by the globe valve on pressure distribution and valve flow coefficient. International Society of Automation (ISA) recommends locations for measuring pressure drop of the valve to determine its flow coefficient. This paper presents the comparison of the pressures at different locations along with the upstream and the downstream of the valve with the values at recommended positions by the ISA standard. The results show that in partially filled pipe flow, the discrepancies in pressure between different measurement locations in the valve downstream are significant at valve openings less than 30%. The aerated flow induces the oscillation in pressure and flow rate, which leads to the fluctuation in the flow coefficient of the valve. The flow coefficients have a linear relationship with the Reynolds number. For the same increase of Reynolds number, the flow coefficients grow faster with larger valve openings and level off at the opening of 50%.
Switched-Capacitor Quasi-Switched Boost Inverters
Nguyen, Minh-Khai,Duong, Truong-Duy,Lim, Young-Cheol,Kim, Yi-Gon Institute of Electrical and Electronics Engineers 2018 IEEE transactions on industrial electronics Vol.65 No.6
<P>In this paper, two switched-capacitor quasi-switched boost inverters (qSBIs) are proposed. By adding one capacitor and one diode to the qSBIs, the proposed inverters achieve high voltage gain with low voltage stress on active switches, capacitors, and diodes. The proposed inverters can extend to <I>n</I>-cell for voltage gain improvement. The operating principle, steady-state analysis, and impedance parameter selections of the proposed inverter are presented. A full comparison between the proposed inverter and other impedance-source inverters is addressed. A 500-W prototype is built to verify the operating theory of the proposed inverter in both the standalone mode and the grid-connected mode. Simulation and experimental results validate the theoretical analysis.</P>
Khai Ngoc Nguyen,김윤아,Sawarot Maibunkaew,박지수,Mien Thi Nguyen,오두병,권오석 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.2
1-Deoxynojirimycin (DNJ) is a potent inhibitor of α-glucosidase having antidiabetic and antiviral activities. In the present study, DNJ production by Bacillus subtilis subsp. inaquosorum KCTC 13429 (B. subtilis IWT) was confirmed and a mutant B. subtilis I.247 strain showing 52% increased DNJ production than wild-type strain after cultivation in 5% defatted soybean meal (DFS) for five days was isolated by UV random mutagenesis. The optimum culture conditions to maximize DNJ production by B. subtilis I.247 was predicted using response surface methodology to cultivate in medium containing 3.4% sorbitol and 2.4% yeast extract as carbon and nitrogen sources, respectively, at a temperature of 32ºC. Under these conditions B. subtilis I.247 was able to produce 359 mg/L after five days of cultivation. Furthermore, when the B. subtilis I.247 transformant harboring a vector expressing a gabT1-yktc1- gutB1 DNJ biosynthetic gene cluster was cultured under the optimized condition, DNJ production was increased to 773 mg/L, representing a level 6.2-fold higher than that of the wild-type strain cultured in 5% DFS for five days.