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Mechanical characterization of flat specimens in tensile test and numerical simulation
Saijun Zhang,Qinxiang Xia,Ning Yuan 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.2
Tensile test experiments with flat specimens for SPCC and JAC340H are presented and simulated in this paper. Digital image correlation (DIC) technology is used to measure the deformation during tension procedure, and the accuracy of the home-developed DIC equipment is discussed. The 3-D finite element models of tensile specimens are developed to analyze the influences of different yield functions upon evaluating the engineering stress-engineering strain relationship, load-true strain curve, transversal-longitudinal true strain relationship and the distribution of longitudinal strain after necking. The comparisons between the simulations and the experimental results show that the Barlat 1991 yield function offers better results than the von Mises yield function and Hill 1948 yield function do.
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Mao Saijun,Wang Huizhen,Yan Yangguang The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Electrical Mach Vol.b5 No.4
This paper proposes a novel zero-voltage-switching (ZVS) Push-pull DC-DC Converter for high input voltage and high power applications. This topology utilizes two switches in series to replace one switch in conventional push-pull converter, and two clamping diodes are introduced. The voltage stress of the switches is the input voltage, and the switches can realize ZVS with the use of the leakage inductance of the transformer. Furthermore, secondary full-wave rectifier with a clamping capacitor is used to eliminate the voltage oscillation and spike of the rectifier diodes due to the reverse recovery. Therefore, the electromagnetic interference is reduced effectively. The operation principle of the proposed converter is analyzed theoretically. The output characteristic, ZVS condition and design principle of the clamping capacitor are discussed. Experimental results obtained from a 270V input 2kW prototype with $95.8\%$ high efficiency confirms the design.
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Tianzhu Tang,J.A.Ferreira,Saijun Mao,Wenbo Wang,M.Ghaffarian Niasar 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper presents a medium frequency transformer with high insulation level design which is used for the DAB DC-DC converter. The transformer size is largely reduced when operating at medium frequency compared with conventional power frequency transformer which provides the possibility for higher power density. However, there is a trade-off between the high power density and thermal performance. First of all, the exposed cooling surface is reduced accordingly. And the dissipated heat is proportional to the exposed cooling surface directly. Secondly with higher frequencies, effects such as skin and proximity and hysteresis losses are significantly increased compared to transformer operation at 50/60 Hz. Besides the design process should consider high isolation requirement. And this again defects the transformer thermal performance and this is because firstly insulation material adds extra losses to the system, secondly the construction of the insulation will block some cooling surfaces and thirdly those insulation materials normally have relatively low thermal conductivity. As a consequence, the thermal design should be carefully considered and evaluated. To solve this problem, only the high voltage side winding is impregnated in epoxy resin which reduces the insulation material. The stacked transformer cores are gapped from each other which have helped the transformer heat dissipation. Such that, a design with low thermal resistance and high power density is achieved. FEM models are developed to analyze the transformer electric and thermal performances. Finally prototypes are built and tested to verify our design concept.
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Wang Bin,Chen Xuheng,Chen Zhiyuan,Xiao Huiwen,Dong Jiali,Li Yuan,Zeng Xiaozhou,Liu Jinjian,Wan Guoyun,Fan Saijun,Cui Ming 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-
Gut microbial preparations are widely used in treating intestinal diseases but show mixed success. In this study, we found that the therapeutic efficacy of A. muciniphila for dextran sodium sulfate (DSS)-induced colitis as well as intestinal radiation toxicity was ~50%, and mice experiencing a positive prognosis harbored a high frequency of A. muciniphila in the gastrointestinal (GI) tract. Stable GI colonization of A. muciniphila elicited more profound shifts in the gut microbial community structure of hosts. Coexisting with A. muciniphila facilitated proliferation and reprogrammed the gene expression profile of Lactobacillus murinus, a classic probiotic that overtly responded to A. muciniphila addition in a time-dependent manner. Then, a magnetic-drove, mannose-loaded nanophase material was designed and linked to the surface of A. muciniphila. The modified A. muciniphila exhibited enhancements in inflammation targeting and intestinal colonization under an external magnetic field, elevating the positive-response rate and therapeutic efficacy against intestinal diseases. However, the unlinked cocktail containing A. muciniphila and the delivery system only induced negligible improvement of therapeutic efficacy. Importantly, heat-inactivated A. muciniphila lost therapeutic effects on DSS-induced colitis and was even retained in the GI tract for a long time. Further investigations revealed that the modified A. muciniphila was able to drive M2 macrophage polarization by upregulating the protein level of IL-4 at inflammatory loci. Together, our findings demonstrate that stable colonization of live A. muciniphila at lesion sites is essential for its anti-inflammatory function.
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