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Frequency Slice Wavelet Transform for Dynamic Signal Analysis
Zhongwei Jiang,Zhonghong Yan 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.10
A new time-frequency analysis method, called frequency slice wavelet transform (FSWT), is introduced. The basic idea of FSWT comes from the short-time Fourier transform(STFT) by extension directly to frequency domain. The original signal can be decomposed by frequency slice function(FSF), which is similar to the wavelet base. Also the signal can be reconstructed by the FSWT representation in an easy way without the strict limitation in wavelet theory. In this paper, the basic theory of FSWT are described first. Tow application examples are demonstrated the efficiency of FSWT on structure dynamic analysis. First example shows how to identify or separate a complex impulse vibration signal. As the second example, FSWT is used to estimate the group velocity of A? Lamb wave in beam and to detect the reflection wave from a weak crack. The experimental result shows the accurate estimation of the arrival time of reflection wave from the crack and the group velocity with the aid of FSWT.
Power conditioning system of Flywheel Energy Storage
Zhongwei Chen,Xudong Zou,Shanxu Duan,Huarong Wei 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In a Flywheel Energy Storage system (FESS), the power conditioning system is the key component of controlling power transfer between the Flywheel and the power system. The dynamics of the power conditioning system directly affect the effect of FESS in dynamic regulation of power system. In this paper, power conditioning system which is made up of a doubly-fed induction machine (DFIM) connected with flywheel, a back-to-back converter for AC excitation and an excitation vector control system is studied. The excitation control strategy is presented for FESS DFIM to improve transient stability and increase transfer capability of power systems. The proposed control method has good dynamics that can respond to the system power demand quickly and accurately. Moreover, the proposed control method has good robust characteristic and applicability to improve the performance of power conditioning system. Simulation and experiment results are performed to evaluate the performance of the proposed control method.
Zhongwei Liang,Bangyan Ye,Yijun Wang,Richard Kars Brauwer 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10
In inspecting the detailed performance results of surface precision modeling in different external parameter conditions, the integrated chip surfaces should be evaluated and assessed during topographic spatial modeling processes. The application of surface-fitting algorithms exerts a considerable influence on topographic mathematical features. The influence mechanisms caused by different surfacefitting algorithms on the integrated chip surface facilitate the quantitative analysis of different external parameter conditions. By extracting the coordinate information from the selected physical control points and using a set of precise spatial coordinate measuring apparatus,several typical surface-fitting algorithms are used for constructing micro-topographic models with the obtained point cloud. In computing for the newly proposed mathematical features on surface models, we construct the fuzzy evaluating data sequence and present a new three-dimensional fuzzy quantitative evaluating method. Through this method, the value variation tendencies of topographic features can be clearly quantified. The fuzzy influence discipline among different surface-fitting algorithms, topography spatial features, and the external science parameter conditions can be analyzed quantitatively and in detail. In addition, quantitative analysis can provide final conclusions on the inherent influence mechanism and internal mathematical relation in the performance results of different surface-fitting algorithms, topographic spatial features, and their scientific parameter conditions in the case of surface micro modeling. The performance inspection of surface precision modeling will be facilitated and optimized as a new research idea for micro-surface reconstruction that will be monitored in a modeling process.
Zhongwei Zhao,Han Zhu,Zhi-Hua Chen,Yansheng Du 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.3
The erection phase is the most vulnerable period in the life of a structure. However, no mature and effective method for optimizing the construction procedures of large-span steel structures is yet available. Thus, proposing an optimization method for constructing such structures is critical. A real-coded genetic algorithm (GA) was proposed in the present work, and the selection, crossover, and mutation operators were programmed. The proposed algorithm is effective in optimizing integer combinations and sequences, such as an unloading sequence. A series of problems that occurred during the erection of conchshaped complex large steel structures was optimized using the proposed method. Optimum analysis was conducted using MATLAB and the general finite element software ANSYS. The optimal layouts of the lifting points, false work, and unloading sequence were derived. The influence of the GA parameters on its convergence efficiency was also studied. Therefore, the proposed GA method is reliable and effective for optimizing the construction procedures of large-span steel structures.
Zhongwei Gan,Jinkui Yang,Nan Tao,Zefen Yu,Ke-Qin Zhang 한국미생물학회 2007 The journal of microbiology Vol.45 No.5
Clonostachys rosea (syn. Gliocladium roseum) is a well-known biocontrol agent and widely distributed around the world. In this study, an endochitinase gene Crchi1 was isolated from the mycoparasitic fungus C. rosea using the DNA walking strategy. The Crchi1 ORF is 1,746 bp long and interrupted by three introns. The cloned gene Crchi1 encodes 426 amino acid residues and shares a high degree of similarity with other chitinases from entomopathogenic and mycoparasitic fungi. Several putative binding sites for transcriptional regulation of Crchi1 in response to carbon (5'-SYGGRG-3') and nitrogen (5'-GATA-3') were identified in the upstream of Crchi1. Expression of Crchi1 gene in different carbon sources was analyzed using real-time PCR (RT-PCR). We found that the Crchi1 expression was suppressed by glucose but strongly stimulated by chitin or solubilized components of the cell wall from Rhizoctonia solani. Phylogenetic analysis of chitinases from entomopathogenic and mycoparasitic fungi suggests that these chitinases have probably evolved from a common ancestor.
Zhongwei Zhao,Zhi-Hua Chen,Hongbo Liu,Bingzhen Zhao 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.3
The erection process of long-span spatial structures is significantly nonlinear which is often accompanied by variations in boundary condition and material property. Many researchers have conducted investigations on construction simulation of complex structures. But few investigate influence of erection process on buckling behavior of structures in service. A method for estimating the influence was proposed. The reliability and accuracy of this method was validated. Then three kinds of structures were analyzed to estimate influence of erection process. The results indicate that some kinds of structures are sensitive to erection process. Influence of erection process on buckling capacity should be considered appropriately.
Zhongwei Zhai,Haibo Wang,Benmei Wei,Peiwen Yu,Chengzhi Xu,Lang He,Juntao Zhang,Yuling Xu 한국고분자학회 2018 Macromolecular Research Vol.26 No.7
Self-assembled environment of collagen is one of the important factors for improving and regulating the properties of collagen-based biomaterials. This study aimed to investigate the effect of ionic liquids (ILs) on the fibril-formation and gel properties of grass carp (Ctenopharyngodon idellus) skin collagen. Fibrillogenic kinetics analysis showed that the collagen self-assembly can be suppressed by the introduction of ILs, and the inhibitory effect is influenced by concentration and types of ILs. Scanning electron microscopy test indicated that the assembled collagen fibrils in the presence of ILs had bigger diameters than that in the conventional buffer. Differential scanning calorimetry analysis revealed that the thermal stability of collagen fibrils can be significantly increased when self-assembly is performed in the presence of ILs. Moreover, the introduction of ILs enhanced the mechanical strength of collagen gels. Finding from this work provides a new idea for improving the performance of fish-sourced collagen biomaterials.