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RISS 인기검색어
- 검색키워드
- 저자 : He Meiling (검색결과 4 건)
- 무료
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- 유료
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Structural State Detection Using Transmissibility and Non-negative Matrix Factorization
Tongqun Ren,Meiling Hui,Junsheng Liang,Dazhi Wang,Liang He,Yonghang Chen 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.11
Transmissibility function (TF) was used in structural state detection which examined the change of the response-only vibration characteristics. The technology of signal correlation was utilized to obtain the TF between two testing points. Multiple TFs under different states were calculated as basic TFs and formed a state matrix. Subsequently, non-negative matrix factorization (NMF) was performed for the state matrix. Then both the basic and testing TFs were projected to the feature subspace derived from NMF so as to obtain the state feature index vectors, respectively. Finally, the Euclidean distance between state feature index vectors was defined as the state indicator. The experimental results indicated that this method can achieve better detection accuracy than that using magnitude indicator. Actually, a result with 100 percent correct detection was achieved when proper rule of dimensionality reduction was selected. This method is essentially a multivariate statistical process monitoring (MSPM) method. It is feasible in vibration-based structural state detection in the situation where the excitation signals are unavailable or inaccessible.
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A New Modulation to Eliminate the Impact of Overlap Time for Three-Phase Current Source Converters
Ding Hao,Guo Xiaoqiang,He Meiling,Shi Changli,Jia Dongqiang,Chen Chao,Guerrero Josep M. 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.5
Three-phase current source converter tends to be attractive in future industrial applications. In order to ensure the continuous current for the dc-link inductor of the current source converter (CSC), an overlap time is mandatory for each switch, so as to avoid the over-voltage spike caused by the dc-link inductor current interruption. However, the overlap time results in the undesirable harmonics and current distortion, which fails to comply with the relevant IEEE Standard in terms of power quality. Especially, the negative infl uence caused by overlap time eff ect is much more serious with the increasing of the switching frequency applied to CSC. In order to solve the problem, the impact of the overlap time on the CSC is investigated, and the error resulted from the overlap time is clearly demonstrated. Based on the pulse equivalent principle and the Fourier analysis, the quantitative relationship between the current harmonic and the overlap time is obtained. And then, a new approach to eliminate the impact of overlap time on the CSC is proposed. Finally, the simulation and experimental results are carried out to verify the eff ectiveness of the proposed solution.
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Xingjun Gao,Xiang Li,Yan He,Lin Fan,Meiling Tang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.11
In order to solve the problems of low efficiency, pollution and large damage of existing polishing methods, the electrical enhanced photocatalysis polishing method for single-crystal silicon carbide was proposed in this paper. The recombination of electrons and holes was inhibited by the combined action of applied electric field and chemical trapping agent, so the efficiency of oxidation was improved, and the polishing of silicon carbide with high efficiency and low damage can be achieved. The effects of various parameters such as polishing pressure, polishing speed, polishing pad, abrasive particles and oxygenation of slurry on polishing effect were studied. 0.025 MPa of polishing pressure, 60 r/min of polishing speed, 5 wt% of SiO2 abrasive particles and synthetic fiber polymer polishing pad can provide the higher MRR of 1.18 μm/h and the best surface quality (Ra = 0.348 nm). In addition, it has been proven that UV, optimized pH, types of photocatalysts, electron trapping agent and voltage are necessary factors for the slurry to exhibit strong oxidizing properties. The MRR is mainly determined by both mechanical action (introduced by abrasive particles) and chemical action (introduced by slurry). The above technology can basically meet the requirements of high-efficiency, ultra-smooth and low damage polishing of single-crystal silicon carbide.
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Tong Shen,Jianming Li,Xiaoshun He,Meiling Lei,Jingru Wang,Xiuming Li 한국유전학회 2014 Genes & Genomics Vol.36 No.6
Here, the major histocompatibility complex(MHC) class II alpha chain gene in the Chinese longsnoutcatfish (Leiocassis longirostris) was characterized throughcloning, sequencing, polymorphism analysis, and expressionpatterns in various tissues. The full-length LeloDAAcDNA comprises 1,114 bp with a 50-UTR region of 79 bp,an open reading frame of 714 bp and a 30-UTR of 302 bp. The deduced protein sequence shows the followingimportant features: leader peptide, a1, a2, and CP/TM/CYT regions. Using long PCR techniques, the genomicsequence was further identified to be 2,093 bp in length,containing four exons and three introns. Three class IIAalleles were identified from four individuals. Two differentalleles observed (at most) in each individual suggest theexistence of a single locus of class IIA gene in the Chineselongsnout catfish genome. This locus is polymorphic andmost of the amino acidic changes occurred in the a1domain containing the peptide-binding region. Lelo-DAAmRNA expression was mainly found in the intestine, gills,spleen, head kidney and liver; minor expression wasdetected in the stomach, skin, heart and muscle. Our resultsyield insight into Chinese longsnout catfish T cell immuneresponses and will aid future work on the genetic status ofthis economically important species.
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