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RISS 인기검색어
- 검색키워드
- 저자 : Lifu Zhang (검색결과 4 건)
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Nonlinear Increase of Spatial Noise for Ultrashort Pulses with Different Temporal Widths
Lifu Zhang,Xiquan Fu,Jianqin Deng,Hua Yang,Youwen Wang,Shuangchun Wen,Huiwen Xu,Jinggui Zhang,Jin Zhang,Dianyuan Fan 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
In this paper, the dynamic evolution of the spatial noise modulation of ultrashort laser pulses in carbon disulfide (CS2) is investigated experimentally, and different temporal widths of the stretched pulse are analyzed for spatial noise gain. The spatial noise evolution (i.e., small-scale self-focusing) of ultrashort laser pulses with different temporal widths as a function of the length of the CS2 has been observed. If the spectral bandwidth is invariant, the experimental results show that a stretched pulse with a broader temporal width can postpone the small-scale self-focusing of spatial noise for longer medium length with constant input power or for greater input power with the same medium length. In this paper, the dynamic evolution of the spatial noise modulation of ultrashort laser pulses in carbon disulfide (CS2) is investigated experimentally, and different temporal widths of the stretched pulse are analyzed for spatial noise gain. The spatial noise evolution (i.e., small-scale self-focusing) of ultrashort laser pulses with different temporal widths as a function of the length of the CS2 has been observed. If the spectral bandwidth is invariant, the experimental results show that a stretched pulse with a broader temporal width can postpone the small-scale self-focusing of spatial noise for longer medium length with constant input power or for greater input power with the same medium length.
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Morphology Evolution of Mn5Si3 Phase and Effect of Mn content on Wear Resistance of Special Brass
Lifu Bie,Xiaohong Chen,Ping Liu,Tao Zhang,Xiangliu Xu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.4
There is a surge of interests in developing newer materials with special properties and many areas are being explored byseveral groups. We wish to report our findings on the effect of Mn content on the microstructure and tribological behaviorof special brass. With the increase of Mn content in the range of 4–10 wt%, the hardness and wear resistance of the specialbrass were all changed, and the adhesion with abrasion is form the friction behavior, mainly for all brasses. It was observedthat the matrix grain size was the smallest, and the hard phase was precipitated the most when the Mn quantity attained the8 wt% mark. During this period, the brass has the highest hardness and best wear resistance, which results from the grainrefinement and load transferring effect of precipitates. It was characterized by SEM, EDS, XRD, TEM, etc., and the resultsconfirmed that the precipitates were Mn5Si3and its structure was hollow hexagonal prism. The morphology evolution of thehard phase and its growth mechanism have been investigated, analyzed and simulated the nucleation and growth process ofthe Mn5Si3phase based on crystallography. The outcomes also showed that the presence of defects on the {0001} faces wasthe crucial factor for one-dimensional elongated structure of Mn5Si3phase.
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Yuantao Sun,Zengzeng Zhang,Qing Zhang,Xian-rong Qin,Lifu Luo 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10
The fatigue failure of crack structure is influenced by fracture failure and static strength failure in the process of its growth. And the correlation characteristics between them change with the crack growth, which brings difficulties to safety assessment. To solve this problem, we propose a reliability model of failure crack propagation (FCP) based on time-varying copula. Meanwhile, a dynamic parameter estimation is put forward to build the time-varying copula. First, a flexible mixed copula model was constructed, by means of linear weighted model, to describe the nonlinear dependence among failure modes. Then the time-varying correlation parameters of copula were obtained by maximum likelihood estimation and least square polynomial fitting. Therefore, the dynamic parameter estimation of copula was realized, and then we used the built time-varying copula model to solve the reliability of joint failure. Finally, a numerical example was provided to illustrate the feasibility and application of the built time-varying copula model.
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Li, Fu,Cao, Yufeng,Luo, Yanyan,Liu, Tingwu,Yan, Guilong,Chen, Liang,Ji, Lilian,Wang, Lun,Chen, Bin,Yaseen, Aftab,Khan, Ashfaq A.,Zhang, Guolin,Jiang, Yunyao,Liu, Jianxun,Wang, Gongcheng,Wang, Ming-Kui The Korean Society of Ginseng 2019 Journal of Ginseng Research Vol.43 No.4
Background: The leaves and roots of Panax ginseng are rich in ginsenosides. However, the chemical compositions of the leaves and roots of P. ginseng differ, resulting in different medicinal functions. In recent years, the aerial parts of members of the Panax genus have received great attention from natural product chemists as producers of bioactive ginsenosides. The aim of this study was the isolation and structural elucidation of novel, minor ginsenosides in the leaves of P. ginseng and evaluation of their antiinflammatory activity in vitro. Methods: Various chromatographic techniques were applied to obtain pure individual compounds, and their structures were determined by nuclear magnetic resonance and high-resolution mass spectrometry, as well as chemical methods. The antiinflammatory effect of the new compounds was evaluated on lipopolysaccharide-stimulated RAW 264.7 cells. Results and conclusions: Two novel, minor triterpenoid saponins, ginsenoside $LS_1$ (1) and 5,6-didehydroginsenoside $Rg_3$ (2), were isolated from the leaves of P. ginseng. The isolated compounds 1 and 2 were assayed for their inhibitory effect on nitric oxide production in LPS-stimulated RAW 264.7 cells, and Compound 2 showed a significant inhibitory effect with $IC_{50}$ of $37.38{\mu}M$ compared with that of NG-monomethyl-L-arginine ($IC_{50}=90.76{\mu}M$). Moreover, Compound 2 significantly decreased secretion of cytokines such as prostaglandin $E_2$ and tumor necrosis factor-${\alpha}$. In addition, Compound 2 significantly suppressed protein expression of inducible nitric oxide synthase and cyclooxygenase-2. These results suggested that Compound 2 could be used as a valuable candidate for medicinal use or functional food, and the mechanism is warranted for further exploration.
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