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Characterization of Dilution Chamber System for Particle Volatility Study
Duong Hoang Do,Yanfang Chen,Hyungu Kang,Jeong Jiwoo,Hwajin Kim 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
Studying of particle properties in well-controlled environment chamber is significant for the purpose of parameterization as well as enhancing the efficiency of experiment by reducing the timescale. System composed of two connected smog chambers, to generate and measure particle volatility via diluting particles, has been developed. To obtain accurate results, this technique requires optimum diluting rate and correction factors. We conducted experiments at various initial conditions including RH, NOx, mass concentration in 27 m³ chamber. A bellows pump transported sample air to a 6 m³ chamber for dilution. Particle phase was monitered by Aerosol Mass Spectrometer (AMS) and scanning mobility particle sizer (SMPS). Our particle-wall loss rate were consistent with other chamber studies. However, we found that particle at the humid condition (>50%) was likely to coagulate and lost to the Teflon wall faster than lower relative humidity condition. Second, transport flow rate and dilution ratios effects were investigated to determine losses of particles in system. The results provided optimum experimental condition with Seoul relevant condition. Dilution of 10:1 zero air to sample air with transporting flow rate of 100 Lpm resulted less than 20% of particle loss in major particle size range from 100 nm to 400 nm. Further investigation results on SOA mass yield and particle aging will be presented.
Do, Nhu Tri,da Costa, Daniel Benevides,Duong, Trung Q.,Bao, Vo Nguyen Quoc,An, Beongku IEEE 2017 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.16 No.8
<P>In this paper, we analyze the downlink outage performance of opportunistic scheduling in dual-hop cooperative networks consisting of one source, multiple radio-frequency energy harvesting relays, and multiple destinations. To this end, two low-complexity, suboptimal, yet efficient, relay-destination selection schemes are proposed, namely direct links plus opportunistic channel state information (CSI)-based selection (DOS) scheme and direct links plus partial CSI-based selection (DPS) scheme. Considering three relaying strategies, i.e., decode-and-forward (DF), variable-gain amplify-and-forward (VG-AF), and fixed-gain amplify-and-forward (FG-AF), the performance analysis in terms of outage probability (OP) is carried out for each selection scheme. For the DF and VG-AF strategies, exact analytical expressions and tight closed-form approximate expressions for the OP are derived. For the FG-AF strategy, an exact closed-form expression for the OP is provided. Additionally, we propose a gradient-based search method to find the optimal values of the power-splitting ratio that minimizes the attained OPs. The developed analysis is corroborated through Monte Carlo simulation. Comparisons with the optimal joint selection scheme are performed and it is shown that the proposed schemes significantly reduce the amount of channel estimations while achieving comparable outage performance. In addition, regardless of relaying strategy used, numerical results show that the DOS scheme achieves full diversity gain, i.e., M+K, and the DPS scheme achieves the diversity gain of M+1, where M and K are the numbers of destinations and relays, respectively.</P>
Improving the Performance of Cell-Edge Users in NOMA Systems Using Cooperative Relaying
Do, Tri Nhu,da Costa, Daniel Benevides,Duong, Trung Q.,An, Beongku Institute of Electrical and Electronics Engineers 2018 IEEE Transactions on Communications Vol. No.
<P>In this paper, we study the performance improvement methods for a cell-edge user of two-user non-orthogonal multiple access (NOMA) systems in downlink scenarios. To this end, we propose two cooperative relaying schemes, namely ON/OFF-full-duplex relaying (ON/OFF-FDR) and ON/OFF-half-duplex relaying (ON/OFF-HDR) schemes. More specifically, in order to improve the performance of the cell-edge user, we consider a cell-center user as a relay, where either FDR or HDR can be employed to assist the direct NOMA transmission from a base station (BS) to the cell-edge user. An ON/OFF mechanism is proposed to decide whether the cooperative relaying transmission is necessary or not. The ON/OFF relaying decision is made based on the quality of the direct and relaying links from the BS to the cell-edge user. The performance of the two proposed schemes is investigated in terms of outage probability and sum throughput. Numerical results reveal that the proposed schemes not only provide essential outage performance improvements for the cell-edge user, but also are able to improve the sum throughput of the two-user NOMA systems. The advantages and drawbacks of each proposed scheme are highlighted and insightful discussions are provided.</P>
Thermal Analysis of a High Speed Induction Motor Considering Harmonic Loss Distribution
Duong, Minh-Trung,Chun, Yon-Do,Park, Byoung-Gun,Kim, Dong-Jun,Choi, Jae-Hak,Han, Pil-Wan The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.8 No.1
In this paper, a thermal analysis of a high speed induction motor with a PWM voltage source was performed by considering harmonic loss components. The electromagnetic analysis of the high speed induction motor was conducted using the time-varying finite element method, and its thermal characteristics were carried out using the lump-circuit method. Harmonic losses from tests in the high frequency region were divided into core loss and conductor loss components using various ratios, in order to determine the loss distributions for the thermal analysis. The results from both the calculations and experiment were validated using a high speed induction motor prototype operating at 20,000rpm.