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Xu, Yan,Lu, Guang-Xiang,Jiang, Li-Jie,Yi, Gui-Ping The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2
This paper analyses the harmonic pollution to power grids caused by several high-power rectifiers, summarizes the requirements for rectifiers in suppressing grid-side current harmonics and optimizes a new-type of current source PWM rectifier with a hybrid switch. The rectifier with a hybrid switch boasts significant current characteristics and cost advantages in the high-power area. To further enhance the working frequency of the current source rectifier with a hybrid switch for suppressing grid-side harmonics and reducing the inductance size, this paper proposes an optimal control strategy based on space vector. It also verifies that the optimal control strategy based on space vector can reduce the total harmonic distortion of the grid-side current of the rectifier with a hybrid switch via circuit simulation and experimental results.
Research on the Hybrid ant Colony Algorithm based on Genetic Algorithm
Xu Yan 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.3
Since the ant colony algorithm is proposed, it has achieved the remarkable achievements in many fields. With the development of the times, the traditional ant colony algorithm exposes its limitations for solving the questions. In this paper, we improve the ant colony algorithm. And we combine the ant colony algorithm with the genetic algorithm. Then, we propose the GAPSPAC algorithm. The algorithm combines the advantages of the genetic algorithm and the ant colony algorithm. And it overcomes the disadvantages to improve the efficiency of solving the questions. In the last experiment, we can see the algorithm has the better problem solving ability and the stability.
Xu, Yan,Selerio-Poely, Tshepiso,Ye, Xingru Korean Academy of Periodontology 2018 Journal of Periodontal & Implant Science Vol.48 No.1
Purpose: To evaluate the clinical and microbiological effects of the local use of egg yolk immunoglobulin against Porphyromonas gingivalis (anti-P.g. IgY) as an adjunct to scaling and root planing (SRP) in the treatment of moderate to severe chronic periodontitis. Methods: This was a randomized, placebo-controlled, double-blind trial involving 60 systematically healthy patients with moderate to severe chronic periodontitis. Subjects (n=20/group) were randomly assigned to receive SRP combined with subgingival irrigation of anti-P.g. IgY and anti-P.g. IgY mouthwash, subgingival irrigation of 0.2% chlorhexidine and 0.2% chlorhexidine mouthwash, or subgingival irrigation of placebo and placebo mouthwash for 4 weeks. Probing pocket depth, clinical attachment level, bleeding on probing, and the plaque index were evaluated at baseline and at 4 weeks. Subgingival plaque, gingival crevicular fluid, and saliva were simultaneously collected for microbiological analysis. Results: Our results showed that anti-P.g. IgY mouthwash was as effective as chlorhexidine at improving clinical parameters over a 4-week period. All the groups showed a significant reduction in levels of P.g. at 4 weeks. No significant difference was observed in the test group when compared to placebo regarding the reduction in the levels of P.g. Anti-P.g. IgY significantly suppressed the numbers of red complex bacteria (RCB) in subgingival plaque and saliva in comparison with placebo. No adverse effects were reported in any of the subjects. Conclusions: Within the limitations of the study, the present investigation showed that passive immunization with anti-P.g. IgY may prove to be effective in the treatment of chronic periodontitis due to its ability to improve clinical parameters and to reduce RCB. No significant differences were found between the anti-P.g. IgY and placebo groups in the reduction of P.g.
Seismic design strategy of cable stayed bridges subjected to strong ground motions
Xu, Yan,Duan, Xinzhi,Li, Jianzhong Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.6
In this paper, we present an alternative seismic design strategy for cable stayed bridges with concrete pylons when subjected to strong ground motions. The comparison of conventional seismic design using supplemental dampers (strategy A) and the new strategy using nonlinear seismic design of pylon columns (strategy B) is exemplified by one typical medium span cable stayed bridge subjected to strong ground motions from 1999 Taiwan Chi-Chi earthquake and 2008 China Wenchuan earthquake. We first conducted the optimization of damper parameters according to strategy A in response to the distinct features that strong ground motions contain. And then we adopted strategy B to carry out seismic analysis by introducing the elastic-plastic elements that allowing plasticity development in the pylon columns. The numerical results show that via strategy A, the earthquake induced structural responses can be kept in the desired range provided with the proper damping parameters, however, the extra cost of unusual dampers will be inevitable. For strategy B, the pylon columns may not remain elastic and certain plasticity developed, but the seismic responses of the foundation will be greatly decreased, meanwhile, the displacement at the top of pylon seems to be not affected much by the yielding of pylon columns, which indicates the pylon nonlinear design can be an alternative design strategy when strong ground motions have to be considered for the bridge.
ULTRA-NARROW NEGATIVE FLARE FRONT OBSERVED IN HELIUM-10830 Å USING THE 1.6 m NEW SOLAR TELESCOPE
Xu, Yan,Cao, Wenda,Ding, Mingde,Kleint, Lucia,Su, Jiangtao,Liu, Chang,Ji, Haisheng,Chae, Jongchul,Jing, Ju,Cho, Kyuhyoun,Cho, Kyungsuk,Gary, Dale,Wang, Haimin American Astronomical Society 2016 The Astrophysical journal Vol.819 No.2
<P>Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6. m New Solar Telescope at Big Bear Solar Observatory, we show a striking 'negative' flare with a narrow but unambiguous 'dark' moving front observed in He I 10830 angstrom, which is as narrow as 340 km and is associated with distinct spectral characteristics in Ha and Mg II lines. Theoretically, such negative contrast in He I 10830 angstrom can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects.</P>
Xu Yan,Ziyang Wu,Yong Zhao,Biao Liu,Yong Zhao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.08
Silver nanoparticles (NPs) and related semiconductors are a family of very important and widely applied photocatalysts. However, the preparation of high stability and activity of this photocatalyst is still a challenge. In this work, we report a stable Ag/AgCl/AgBi(MoO4)2 heterojunction photocatalyst fabricated via a simple in situ anion-exchange reaction followed by the photoreduction treatment. In the treatment of tetracycline (TC) wastewater under visible light, the AC-0.4 sample (prepared with 0.4 mmol KCl) exhibits the significantly improved activity (degradation ratio, DR of 71.3%) compared with the pristine AgBi(MoO4)2 (30% DR) and Ag/AgCl sample (synthesized by the photoreduction of AgCl) (37% DR) under identical experimental conditions. This activity promotion is from the fast interfacial electron transfer between the heterojunction phases of AgCl/AgBi(MoO4)2 and the SPR effect of Ag NPs. After five successive recycles, the AC-0.4 sample still maintains good stability and activity for TC degradation, which shows a great potential to be used in practical application. Through the ESR and controlled scavenged experiments, we found the · OH and · O- 2 are the major reactive intermediate species in the TC photodegradation reaction. Our work provides a new insight into the synthesis of stable and high efficient Ag-based heterojunction photocatalysts for the application of wastewater treatment.