Time filter

Source Type

Tang Y.-Q.,Shanghai Institute of Applied Mathematics and Mechanics | Tang Y.-Q.,Shanghai Institute of Technology | Chen L.-Q.,Shanghai Institute of Applied Mathematics and Mechanics | Chen L.-Q.,Shanghai University | And 2 more authors.
Nonlinear Dynamics | Year: 2012

Nonlinear forced vibrations of in-plane translating viscoelastic plates subjected to plane stresses are analytically and numerically investigated on the steady-state responses in external and internal resonances. A nonlinear partial-differential equation with the associated boundary conditions governing the transverse motion is derived from the generalized Hamilton principle and the Kelvin relation. The method of multiple scales is directly applied to establish the solvability conditions in the primary resonance and the 3:1 internal resonance. The steady-state responses are predicted in two patterns: single-mode and two-mode solutions. The Routh-Hurvitz criterion is used to determine the stabilities of the steady-state responses. The effects of the in-plane translating speed, the viscosity coefficient, and the excitation amplitude on the steady-state responses are examined. The differential quadrature scheme is developed to solve the nonlinear governing equations numerically. The numerical calculations confirm the approximate analytical results regarding the single-mode solutions of the steady-state responses. © 2011 Springer Science+Business Media B.V.


Li Z.,Shanghai University | Hu G.,Shanghai University | Hu G.,stitutes of Shanghai Universities | Hu G.,Shanghai Key Laboratory of Mechanics in Energy | And 7 more authors.
Physics of Fluids | Year: 2013

It is of both fundamental and practical interest to study the flow physics in the manipulation of droplets. In this paper, we investigate complex flow in liquid droplets actuated by a linear gradient of wettability using dissipative particle dynamics simulation. The wetting property of the substrate ranging from hydrophilic to hydrophobic is achieved by adjusting the conservative solid-liquid interactions which results in a variation of solid-liquid surface tension. The internal three-dimensional velocity field with transverse flow in droplet is revealed and analyzed in detail. When the substrate is hydrophobic, it is found that there is slight deformation but strong flow circulation inside the droplet, and the droplet rolling is the dominant mechanism for the movement. However, large deformation of the droplet is generated after the droplet reaches the hydrophilic surface, and a mechanism combining rolling and sliding dominates the transportation of the droplet. Another interesting finding is that the thermal fluctuation can accelerate the spontaneous motion of a liquid droplet under a wetting gradient. The effects of the steepness of wetting gradient and the size of droplet on the translation speed are studied as well. © 2013 AIP Publishing LLC.


Chen L.-Q.,Shanghai University | Chen L.-Q.,stitutes of Shanghai Universities | Tang Y.-Q.,Shanghai University | Tang Y.-Q.,Shanghai Institute of Technology
Journal of Sound and Vibration | Year: 2011

Nonlinear parametric vibration is investigated for axially accelerating viscoelastic beams subject to parametric excitations resulting from longitudinally varying tensions and axial speed fluctuations. The effects of the longitudinally varying tension due to the axial acceleration are highlighted, while the tension was assumed to be longitudinally uniform in previous studies. The dependence of the tension on the finite axial support rigidity is also modeled. The governing equations of coupled planar vibration and the associated boundary conditions are derived from the generalized Hamilton principle and the viscoelastic constitutive relation. The equation is simplified into a governing equation of transverse nonlinear vibration in small but finite stretching problems. The governing equation of transverse vibration is a nonlinear integro-partial-differential equation with time-dependent and space-dependent coefficients. The method of multiple scales is employed to analyze the combination and the principal parametric resonances with the focus on steady-state responses. In the difference resonance, there is only trivial zero response which is always stable. In the summation and the principal resonances, the trivial responses may become unstable and bifurcate into nontrivial responses for certain excitation frequencies. Some numerical examples indicate that the longitudinal tension variation makes the instability frequency intervals of trivial responses small and the nontrivial response amplitudes large (small) in the summation (principal) resonance. It is also found that the nontrivial responses are not sensitive to the axial support rigidity. Numerical solutions are calculated via the differential quadrature to support results via the method of multiple scales. © 2011 Elsevier Ltd. All rights reserved.


Chen L.-Q.,Shanghai University | Chen L.-Q.,Shanghai Institute of Applied Mathematics and Mechanics | Chen L.-Q.,Shanghai Key Laboratory of Mechanics in Energy Engineering | Chen L.-Q.,stitutes of Shanghai Universities | And 2 more authors.
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2012

In this paper, the parametric stability of axially accelerating viscoelastic beams is revisited. The effects of the longitudinally varying tension due to the axial acceleration are highlighted, while the tension was approximately assumed to be longitudinally uniform in previous studies. The dependence of the tension on the finite support rigidity is also considered. The generalized Hamilton principle and the Kelvin viscoelastic constitutive relation are applied to establish the governing equations and the associated boundary conditions for coupled planar motion of the beam. The governing equations are linearized into the governing equation in the transverse direction and the expression of the longitudinally varying tension. The method of multiple scales is employed to analyze the parametric stability of transverse motion. The stability boundaries are derived from the solvability conditions and the Routh-Hurwitz criterion for principal and sum resonances. In terms of stability boundaries, the governing equations with or without the longitudinal variance of tension are compared and the effects of the finite support rigidity are also examined. Some numerical examples are presented to demonstrate the effects of the stiffness, the viscosity, and the mean axial speed on the stability boundaries. The differential quadrature scheme is developed to numerically solve the governing equation, and the computational results confirm the outcomes of the method of multiple scales. © 2012 American Society of Mechanical Engineers.


Zhou T.,Shanghai JiaoTong University | Wang L.,Shanghai JiaoTong University | Zhu K.-Y.,Shanghai JiaoTong University | Dong M.,Shanghai JiaoTong University | And 7 more authors.
Blood | Year: 2011

The primitive hematopoietic stem/progenitor cells (HSPCs) during embryonic hematopoiesis are thought to be short-lived (SL) with limited self-renewal potential. The fate and consequence of these short-lived HSPCs, once reprogrammed into "long-lived" in a living animal body, remain unknown. Here we show that targeted expression of a dominant-negative C/ebpα (C/ebpαDN) in the primitive SL-HSPCs during zebrafish embryogenesis extends their life span, allowing them to survive to later developmental stage to colonize the definitive hematopoietic sites, where they undergo a proliferative expansion followed by erythropoietic dysplasia and embryonic lethality because of circulation congestion. Mechanistically, C/ebpαDN binds to a conserved C/EBP-binding motif in the promoter region of bmi1 gene, associated with a specific induction of bmi1 transcription in the transgenic embryos expressing C/ebpαDN. Targeted expression of Bmi1 in the SL-HSPCs recapitulates nearly all aberrant phenotypes induced by C/ebpαDN, whereas knockdown of bmi1 largely rescues these abnormalities. The results indicate that Bmi1 acts immediately downstream of C/ebpαDN to regulate the survival and self-renewal of HSPCs and contribute to the erythropoietic dysplasia. © 2011 by The American Society of Hematology.


Xu W.,Shanghai JiaoTong University | Zhu H.,stitutes of Shanghai Universities | Gu M.,stitutes of Shanghai Universities | Luo Q.,Shanghai JiaoTong University | And 4 more authors.
FEBS Letters | Year: 2013

Maintaining the functional integrity of mitochondria is crucial for cell function, signal transduction and overall cell activities. Mitochondrial dysfunctions may alter energy metabolism and in many cases are associated with neurological diseases. Recent studies have reported that mutations in dehydrogenase E1 and transketolase domain-containing 1 (DHTKD1), a mitochondrial protein encoding gene, could cause neurological abnormalities. However, the function of DHTKD1 in mitochondria remains unknown. Here, we report a strong correlation of DHTKD1 expression level with ATP production, revealing the fact that DHTKD1 plays a critical role in energy production in mitochondria. Moreover, suppression of DHTKD1 leads to impaired mitochondrial biogenesis and increased reactive oxygen species (ROS), thus leading to retarded cell growth and increased cell apoptosis. These findings demonstrate that DHTKD1 contributes to mitochondrial biogenesis and function maintenance. © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.


Lu N.,Huazhong University of Science and Technology | Zhang Y.,Huazhong University of Science and Technology | Li H.,Huazhong University of Science and Technology | Gao Z.,Huazhong University of Science and Technology | Gao Z.,stitutes of Shanghai Universities
Free Radical Biology and Medicine | Year: 2010

Many studies have reported that oxidative and nitrative stress might be important in the pathogenesis of diabetes. By means of immunoprecipitation analysis, α-enolase (EC 4.2.1.11, 2-phospho-d-glycerate hydrolyase) was identified as the important target for oxidative and nitrative modifications in diabetic cardiac proteins. The levels of protein carbonyls and 3-nitrotyrosine residues in α-enolase (biomarkers of oxidative and nitrative damage, respectively) from cardiac proteins of diabetic rats were determined and compared with age-matched controls. After 6 weeks of streptozotocin administration, the cardiac proteins from diabetic rats showed: (a) the levels of α-enolase expression and nitration were clearly increased, whereas (b) the enolase activity and oxidation status were not significantly changed. By means of immunoprecipitation and liquid chromatography-tandem mass spectrometry analysis, it was found that Tyr 257 and Tyr 131 of α-enolase were the most susceptible to nitration in diabetic rat heart. Further studies in vitro revealed a significant contribution of protein tyrosine nitration to the inactivation of enolase. These results suggest that tyrosine nitration of α-enolase could contribute to an impaired glycolytic activity in diabetic cardiomyopathy. Meanwhile, the up-regulation of α-enolase expression could be a protective mechanism to neutralize oxidative and nitrative stress in diabetes. © 2010 Elsevier Inc. All rights reserved.


Mo J.-Q.,Anhui Normal University | Mo J.-Q.,stitutes of Shanghai Universities
Communications in Theoretical Physics | Year: 2010

The corresponding solution for a class of disturbed KdV equation is considered using the analytic method. From the generalized variational iteration theory, the problem of solving soliton for the corresponding equation translates into the problem of variational iteration. And then the approximate solution of the soliton for the equation is obtained. © 2010 Chinese Physical Society and IOP Publishing Ltd.


Chen L.-W.,Anhui University of Science and Technology | Wang G.-L.,Anhui University of Science and Technology | Lu X.-Y.,Anhui University of Science and Technology | Lu X.-Y.,stitutes of Shanghai Universities
Journal of Fluid Mechanics | Year: 2011

Numerical investigation of a sonic jet from a blunt body opposing a supersonic flow with a free stream Mach number M∞ = 2. 5 was carried out using large-eddy simulation for two total pressure ratios of the jet to the free stream, i.e. P = 0. 816 and 1.633. Results have been validated carefully against experimental data. Various fundamental mechanisms dictating the flow phenomena, including shock/jet interaction, shock/shear-layer interaction, turbulent shear-layer evolution and coherent structures, have been studied systematically. Based on the analysis of the flow structures and features, two typical flow states, i.e. unstable and stable states corresponding to the two values of P, are identified and the behaviours relevant to the flow states are discussed. Small-scale vortical structures mainly occur in the jet column, and large-scale vortices develop gradually in a recirculation region when the jet terminates through a Mach disk and reverses its orientation as a conical free shear layer. The turbulent fluctuations are enhanced by the rapid deviation of the shear layer and the interaction with shock waves. Moreover, the coherent structures of the flow motion are analysed using the proper orthogonal decomposition technique. It is found that the dominant mode in the cross-section plane exhibits an antisymmetric character for the unstable state and an axisymmetric one for the stable state, while statistical analysis of unsteady loads indicates that the side loads can be seen as a rotating vector uniformly distributed in the azimuthal direction. Further, we clarify a feedback mechanism whereby the unsteady motion is sustained by the upstream-propagating disturbance to the Mach disk through the recirculation subsonic region and downstream propagation in the conical shear layer. Feedback models are then proposed which can reasonably well predict the dominant frequencies of the two flow states. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the opposing jet/supersonic flow interaction. © 2011 Cambridge University Press.


Mo J.-Q.,Anhui Normal University | Mo J.-Q.,stitutes of Shanghai Universities | Lin Y.-H.,CAS Institute of Atmospheric Physics | Lin W.-T.,CAS Institute of Atmospheric Physics
Chinese Physics B | Year: 2010

A reduces equation of the Kelvin wave is considered. By using the homotopic mapping solving method, the approximate solution is obtained. The homptopic mapping method is an analytic method, the obtained solution can analyse operations sequentially. © 2010 Chinese Physical Society and IOP Publishing Ltd.

Loading stitutes of Shanghai Universities collaborators
Loading stitutes of Shanghai Universities collaborators