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Tian C.,Peking University | Lu Y.,Tsinglma University
Engineering Applications of Computational Fluid Mechanics | Year: 2013

In the present paper, based on typical jet flows in shock wave thrust vector nozzles, turbulence modeling in gas flow dynamics has been numerically explored in 2-D laval nozzle which has a secondary injection on one side of its divergent portion in order to simulate the complex strong pressure gradient and accurately capture flow separation point. Nine turbulence models have been adopted and assessed by comparing the obtained results which involve flow separation point and static wall pressure with the available experimental data. Another 3-D nozzle model is simulated using five different turbulence models and results are also compared with experimental data. The numerical results reveal that Goldberg's realizable k-epsilon model gives the best results compared with other models in predicting the shock wave position and separation point, while the SA model shows its advantage in predicting the static wall pressure under certain conditions compared to the Goldberg's realizable k-epsilon model. The computational results were analyzed and the change of the shock structure in different NPRs was discussed in laval nozzle with a secondary flow.

Bradford M.A.,University of South Australia | Dou C.,Tsinglma University
Recent Advances in Environmental Vibration - Proceedings of 6th International Symposium on Environmental Vibration, ISEV 2013 | Year: 2013

Non-linear dynamic buckling of a two degree-of-freedom arch model under suddenly-applied loads is investigated using three methods: the method of equations of motion, the phase-plane method, and the energy method. It is found that the energy method is a most accurate and conven-ient method to determine the dynamic buckling loads of the arch model. The merit of the energy method for dynamic buckling is that it allows the dynamic buckling load to be determined without needing to solve the equations of motion.

Li W.,Tsinglma University | Li W.-T.,Tsinglma University | Cao S.-J.,Tsinglma University | Yu W.-X.,Tsinglma University | And 3 more authors.
Progress in Biochemistry and Biophysics | Year: 2013

Selective binding of transcription factors (TFs) to cis-regulatory elements plays an important role in cell-type specific gene expression in mammalian cells. This process is potentially guided by epigenetic states of the chromatin. Recent studies provide large amounts of genome-wide ChlP-seq data for both TF binding and histone modification loci, enabling large-scale analysis of spatial and regulatory interplay between TFs and epigenetic marks. In this paper, the authors report an integrative analysis of multiple public ChlP-seq and RNA-seq data sets, concerning 85 TFs, 9 histone modifications and 5 cell lines, to investigate the genome-wide localization correlations between transcription factor binding sites (TFBSs), histone modification patterns and transcription in human. This study reveals that genome-wide co-localization with histone modifications follow the same pattern for different TFs, and active histone marks typically adjoin TFBSs at a distance around 500 bp. TF occupancy at conserved sequences is found positively correlated with levels and bimodal pattern of active histone marks, and the bimodal and co-localized patterns track with higher gene expression. The correlation among histone modification patterns, TF occupancy and gene transcription suggests the existence of a possible regulatory mechanism that cells may implement to regulate transcription.

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