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Chuan-Jin Zhang,Yi Tang,Dong Han,Hui Zhang,Xiao Zhang,Ke Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.
Zhang, Chuan-Jin,Tang, Yi,Han, Dong,Zhang, Hui,Zhang, Xiao,Wang, Ke The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.
Chuan-Jin Zhang,Rui-Peng Wei,Yi Tang,Ke Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
A novel space vector modulation strategy in the non-orthogonal three-dimensional coordinate system for multi-level three-phase four-wire inverters is proposed in this paper. This new non-orthogonal three-dimensional space vector modulation converts original trigonometric functions in the orthogonal three-dimensional space coordinate into simple algebraic operations, which greatly reduces the algorithm complexity of three-dimensional space vector modulation and preserves the independent control of the zero-sequence component. Experimental results have verified the correctness and effectiveness of the proposed three-dimensional space vector modulation in the new non-orthogonal three-dimensional coordinate system.
Zhang, Chuan-Jin,Wei, Rui-Peng,Tang, Yi,Wang, Ke The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
A novel space vector modulation strategy in the non-orthogonal three-dimensional coordinate system for multi-level three-phase four-wire inverters is proposed in this paper. This new non-orthogonal three-dimensional space vector modulation converts original trigonometric functions in the orthogonal three-dimensional space coordinate into simple algebraic operations, which greatly reduces the algorithm complexity of three-dimensional space vector modulation and preserves the independent control of the zero-sequence component. Experimental results have verified the correctness and effectiveness of the proposed three-dimensional space vector modulation in the new non-orthogonal three-dimensional coordinate system.
Physical properties and chemical composition of the cores in the California molecular cloud
Zhang, Guo-Yin,Xu, Jin-Long,Vasyunin, A. I.,Semenov, D. A.,Wang, Jun-Jie,Dib, Sami,Liu, Tie,Liu, Sheng-Yuan,Zhang, Chuan-Peng,Liu, Xiao-Lan,Wang, Ke,Li, Di,Wu, Zhong-Zu,Yuan, Jing-Hua,Li, Da-Lei,Gao, Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-
<P><I>Aims.</I> We aim to reveal the physical properties and chemical composition of the cores in the California molecular cloud (CMC), so as to better understand the initial conditions of star formation.</P><P><I>Methods.</I> We made a high-resolution column density map (18.2′′) with <I>Herschel</I> data, and extracted a complete sample of the cores in the CMC with the fellwalker algorithm. We performed new single-pointing observations of molecular lines near 90 GHz with the IRAM 30m telescope along the main filament of the CMC. In addition, we also performed a numerical modeling of chemical evolution for the cores under the physical conditions.</P><P><I>Results.</I> We extracted 300 cores, of which 33 are protostellar and 267 are starless cores. About 51% (137 of 267) of the starless cores are prestellar cores. Three cores have the potential to evolve into high-mass stars. The prestellar core mass function (CMF) can be well fit by a log-normal form. The high-mass end of the prestellar CMF shows a power-law form with an index <I>α</I> = −0.9 ± 0.1 that is shallower than that of the Galactic field stellar mass function. Combining the mass transformation efficiency (<I>ε</I>) from the prestellar core to the star of 15 ± 1% and the core formation efficiency (CFE) of 5.5%, we suggest an overall star formation efficiency of about 1% in the CMC. In the single-pointing observations with the IRAM 30m telescope, we find that 6 cores show blue-skewed profile, while 4 cores show red-skewed profile. [HCO<SUP>+</SUP>]/[HNC] and [HCO<SUP>+</SUP>]/[N2H<SUP>+</SUP>] in protostellar cores are higher than those in prestellar cores; this can be used as chemical clocks. The best-fit chemical age of the cores with line observations is ~5 × 10<SUP>4</SUP> yr.</P>
Diverse Mycena Fungi and Their Potential for Gastrodia elata Germination
Jin Xiao-Han,Wang Yu-Chuan,Li Dong,Li Yu,He Hai-Yan,Zhang Han-Bo 한국미생물·생명공학회 2024 Journal of microbiology and biotechnology Vol.34 No.6
It remains to be determined whether there is a geographical distribution pattern and phylogenetic signals for the Mycena strains with seed germination of the orchid plant Gastrodia elata. This study analyzed the community composition and phylogenetics of 72 Mycena strains associated with G. elata varieties (G. elata. f. glauca and G. elata. f. viridis) using multiple gene fragments (ITS+nLSU+SSU). We found that (1) these diverse Mycena phylogenetically belong to the Basidiospore amyloid group. (2) There is a phylogenetic signal of Mycena for germination of G. elata. Those strains phylogenetically close to M. abramsii, M. polygramma, and an unclassified Mycena had significantly higher germination rates than those to M. citrinomarginata. (3) The Mycena distribution depends on geographic site and G. elata variety. Both unclassified Mycena group 1 and the M. abramsii group were dominant for the two varieties of G. elata; in contrast, the M. citrinomarginata group was dominant in G. elata f. glauca but absent in G. elata f. viridis. Our results indicate that the community composition of numerous Mycena resources in the Zhaotong area varies by geographical location and G. elata variety. Importantly, our results also indicate that Mycena’s phylogenetic status is correlated with its germination rate.
Optical Characters Measurement and Simulation of 2D Cross Grating Microstructures of Butterfly Wings
Zhang, Wang,Zhang, Di,Chen, Wei-Xin,Gu, Jia-Jun,Liu, Qin-Lei,Zhu, Shen-Ming,Su, Hui-Lan,Feng, Chuan-Liang,Moon, Won-Jin 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.9
In this paper, the reflectance of the butterfly wings are measured by using the microspectrophotometer as the optical character with the reflectance on several scales on the wings. Reflectance spectra from different wing scale zones with the same color are dramatically different. And it suggests that the tiny structural difference has the great influence on the reflectance property. In addition, the microstructures of the butterfly wings can be simplified to a 2D crossing grating. By simulating a two-dimensional model using rigorous coupled-wave analysis technique, the optical properties of the butterfly wings were investigated. The simulation results depend strongly on the structural parameters and refractive index. The research will reveal the mechanisms of the structural color of 2D crossing grating butterfly wings.
Zhiming Zhang,Jin Yan,Liangding Li,Hong Pan,Chuan-Zhi Dong 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.1
Stay cables play an essential role in cable-stayed bridges. Severe vibrations and/or harsh environment may result in cable failures. Therefore, an efficient structural health monitoring (SHM) solution for cable damage detection is necessary. This study proposes a data-driven method for immediately detecting cable damage from measured cable forces by recognizing pattern transition from the intact condition when damage occurs. In the proposed method, pattern recognition for cable damage detection is realized by time series classification (TSC) using a deep learning (DL) model, namely, the long short term memory fully convolutional network (LSTM-FCN). First, a TSC classifier is trained and validated using the cable forces (or cable force ratios) collected from intact stay cables, setting the segmented data series as input and the cable (or cable pair) ID as class labels. Subsequently, the classifier is tested using the data collected under possible damaged conditions. Finally, the cable or cable pair corresponding to the least classification accuracy is recommended as the most probable damaged cable or cable pair. A case study using measured cable forces from an in-service cable-stayed bridge shows that the cable with damage can be correctly identified using the proposed DL-TSC method. Compared with existing cable damage detection methods in the literature, the DL-TSC method requires minor data preprocessing and feature engineering and thus enables fast and convenient early detection in real applications.