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- 저자 : Xiang Sun (검색결과 240 건)
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Sun, Xiang,Park, Jinsoo,Choi, Jung-Il,Rhee, Gwang Hoon Elsevier 2017 Building and environment Vol.125 No.-
<P><B>Abstract</B></P> <P>The single-sided ventilation rate in a building can be estimated using an empirical correlation that developed based on the results of deterministic experiments or numerical simulations. Owing to the complex flow patterns near a building, it is difficult to establish a robust correlation considering upstream wind uncertainties such as wind speed and direction. We perform RANS simulations and generalized polynomial chaos-based uncertainty quantification analysis to investigate the effects of the upstream uncertainties on the ventilation rate. It was found that the reference wind speed and the incident angle significantly affect the ventilation rate. Warren and Parkins' correlation shows a reasonable prediction of the average ventilation rate over the incident angle, while Larsen's correlation, in general, underestimates the ventilation rates. Further, the average ventilation rates in the side direction are lower than those in the windward and leeward directions, while larger variations of the ventilation rate in the leeward direction are found at high speeds, compared to those in the other directions. Owing to unresolved turbulent induced ventilation rates in the RANS model, the present ventilation rates may not accurately provide actual ventilation rates. Nevertheless, the present UQ analysis indicates that the existing correlation between the ventilation rate and the wind speed must account for the influence of the wind direction, especially at high wind speeds, in order to estimate the single-sided ventilation rate in a building with greater accuracy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Numerical simulations of single-sided ventilation in a building are performed using the RANS model. </LI> <LI> Uncertainty quantifications (UQ) of upstream wind effects on ventilation rates are analyzed using the gPC approach. </LI> <LI> Warren and Parkins' correlation gives a reasonable prediction of the average ventilation rate over the incidence angle. </LI> <LI> The influence of the wind direction should be considered in the existing ventilation correlation. </LI> </UL> </P>
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Xiang-Dong Sun,Mikihiko Matsui,Byung-Gyu Yu 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
An active anti-islanding method based on the current control for a three-phase grid-connected PV inverter is proposed in this paper. The current of phase a is synchronous with the corresponding voltage at the common coupling point in its positive half cycle, and a zero-current zone is inserted into the end of the cycle in a negative half cycle. As for phase c, the zero-current zone is inserted in the positive half cycle of the current, and the current of phase c in a negative half cycle is synchronous with the corresponding voltage. Therefore the currents of phase a and c in one cycle become asymmetrical slightly. Before the islanding takes place, because of the operation of utility voltage the positive and negative half cycles of three-phase voltages are symmetrical. While the islanding occurs, the time differences between the positive and negative half cycles of the voltages of phase a and c will generate and the islanding is detected in accordance with the repetitive cycles fulfilling the conditions of the time differences. On the basis of the above analysis for three-phase four-wire power systems, three-phase three-wire systems are designed. The experiment on a 0.3㎾ PV inverter system connected to 200V/50㎐ utility are carried out, and it is verified that the method can detect the islanding for the parallel RLC loads even if the voltage frequency is within the non-detection zone. It is seen from the analysis of the detecting principle that there is no influence on the proposed method even if a large load connected in parallel frequently starts up or stops.
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Efficient snoring and breathing detection based on sub-band spectral statistics.
Sun, Xiang,Kim, Jin Young,Won, Yonggwan,Kim, Jung-Ja,Kim, Kyung-Ah Pergamon Press 2015 Bio-medical materials and engineering Vol.26 No.1
<P>Snoring, a common symptom in the general population may indicate the presence of obstructive sleep apnea (OSA). In order to detect snoring events in sleep sound recordings, a novel method was proposed in this paper. The proposed method operates by analyzing the acoustic characteristics of the snoring sounds. Based on these acoustic properties, the feature vectors are obtained using the mean and standard deviation of the sub-band spectral energy. A support vector machine is then applied to perform the frame-based classification procedure. This method was demonstrated experimentally to be effective for snoring detection. The database for detection included full-night audio recordings from four individuals who acknowledged having snoring habits. The performance of the proposed method was evaluated by classifying different events (snoring, breathing and silence) from the sleep sound recordings and comparing the classification against ground truth. The proposed algorithm was able to achieve an accuracy of 99.61% for detecting snoring events, 99.16% for breathing, and 99.55% for silence.</P>
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A Novel Single-Voltage-Sensor-Based Maximum Power Point Tracking Method
Xiang-Dong Sun,Mikihiko Matsui,Kouji Yanagimura 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
A novel maximum power point tracking method for photovoltaic systems based on a single voltage sensor is proposed in this paper. By means of the simulation studies with PSIM software, it has been found that there are similar relationship curves between the expression (C-d)ㆍ(-ΔVPV)and the actual power PPV of a photovoltaic array regardless of the chopper stage topology connected to the array. Therefore the maximum power point tracking based on PPV is replaced with the expression (C-d)ㆍ(-ΔVPV). For the purpose of diminishing the power fluctuation in the steady state, the averaged voltages of a photovoltaic array and the average duty ratios are used for the calculation. Experimental results obtained on a 50W prototype of a lead acid battery charger show high performance such as the less power fluctuation and the less ambient, i.e. irradiation and temperature, influence.
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Xiang Liu,Lizhong Jiang,Ping Xiang,Yulin Feng,Zhipeng Lai,Xiaoyun Sun 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.2
Due to the large number of railway bridges along China's high-speed railway (HSR) lines, which cover a wide area with many lines crossing the seismic zone, the possibility of a HSR train running over a bridge when an earthquake occurs is relatively high. Since the safety performance of the train will be threatened, it is necessary to study the safety of trains running over HSR bridges during earthquakes. However, ground motion (GM) is highly random and selecting the appropriate groundmotion intensity measures (IMs) for train running safety analysis is not trivial. To deal this problem, a model of a coupled trainbridge system under seismic excitation was established and 104 GM samples were selected to evaluate the correlation between 16 different IMs and train running safety over HSR bridges during earthquakes. The results show that spectral velocity (SvT1) and displacement (SdT1) at the fundamental period of the structure have good correlation with train running safety for mediumand long-period HSR bridges, and velocity spectrum intensity (VSI) and Housner intensity (HI) have good correlation for a wide range of structural periods. Overall, VSI and HI are the optimal IMs for safety analysis of trains running over HSR bridges during earthquakes. Finally, based on VSI and HI, the IM thresholds of an HSR bridge at different speed were analyzed.
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Sun Xiang,Zhang Bo,Xu Guangjian,Chen Junwen,Shang Yongpeng,Lin Zhiwei,Yu Zhijian,Zheng Jinxin,Bai Bing 대한진단검사의학회 2021 Annals of Laboratory Medicine Vol.41 No.3
Background: Tigecycline, eravacycline, and omadacycline are recently developed tetracyclines. Susceptibility of microbes to these tetracyclines and their molecular mechanisms have not been well elucidated. We investigated the susceptibility of Moraxella catarrhalis to tigecycline, eravacycline, and omadacycline and its resistance mechanisms against these tetracyclines. Methods: A total of 207 non-duplicate M. catarrhalis isolates were collected from different inpatients. The minimum inhibitory concentrations (MICs) of the tetracyclines were determined by broth microdilution. Tigecycline-, eravacycline-, or omadacycline-resistant isolates were induced under in vitro pressure. The tet genes and mutations in the 16S rRNA was detected by PCR and sequencing. Results: Eravacycline had a lower MIC50 (0.06 mg/L) than tigecycline (0.125 mg/L) or omadacycline (0.125 mg/L) against M. catarrhalis isolates. We found that 136 isolates (65.7%) had the tetB gene, and 15 (7.2%) isolates were positive for tetL; however, their presence was not correlated with high tigecycline, eravacycline, or omadacycline (≥1 mg/L) MICs. Compared with the initial MIC after 160 days of induction, the MICs of tigecycline or eravacycline against three M. catarrhalis isolates increased ≥eight-fold, while those of omadacycline against two M. catarrhalis isolates increased 64-fold. Mutations in the 16S rRNA genes (C1036T and/or G460A) were observed in omadacycline-induced resistant isolates, and increased RR (the genes encoding 16SrRNA (four copies, RR1-RR4) copy number of 16S rRNA genes with mutations was associated with increased resistance to omadacycline. Conclusions: Tigecycline, eravacycline, and omadacycline exhibited robust antimicrobial effects against M. catarrhalis. Mutations in the 16S rRNA genes contributed to omadacycline resistance in M. catarrhalis.
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Xiang-Dong Sun,Kang-Hoon Koh,Byung-Gyu Yu,Matsui, M. IEEE 2009 IEEE transactions on industrial electronics Vol.56 No.8
<P>Since natural distribution power generation systems such as wind energy contain electric power fluctuation, flywheel energy storage (FWES) equipment for power compensation is used. Fuzzy-logic-based <I>V</I>/<I>f</I> control of the induction motor is proposed for the speed sensorless power-leveling system in this paper. Only two sensors, including one DC voltage sensor and one DC current sensor, are utilized. The flywheel is composed of two modes, namely, the speed picking-up control mode and the power control mode. According to the DC-link average current of an inverter, the rotating speed of the flywheel in the speed picking-up control mode is detected by regulating the output frequency and the output voltage based on fuzzy logic control. The power control mode consists of the outer voltage loop and the inner current loop. Although the outer loop is also realized by fuzzy logic control, the inner loop is the key object in this paper, i.e., the proportional and integral gains of a proportional-integral regulator are optimized by means of fuzzy logic reasoning for the purpose of the reliability and rapid response of leveling power. The experiments are carried out with the FWES equipment of 40-kJ energy, and the results verify that the proposed method is reliable, and better dynamic and static performance is demonstrated.</P>
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