Bifurcation and dynamic response analysis of rotating blade excited by upstream vortices

Acknowledgements The authors acknowledge the projects supported by the National Basic Research Program of China (973 Project)(No. 2015CB057405) and the National Natural Science Foundation of China (No. 11372082) and the State Scholarship Fund of CSC. DW thanks for the hospitality of the University of Aberdeen.Peer reviewedPostprin

Data-Driven Energy Levels Calculation of Neutral Ytterbium (ZZ = 70)

In view of the difficulty in calculating the atomic structure parameters of high-$Z$ elements, the HFR (Hartree-Fock with relativistic corrections) theory in combination with the ridge regression (RR) algorithm rather than the Cowan code's least squares fitting (LSF) method is proposed and applied. By analyzing the energy level structure parameters of the HFR theory and using the fitting experimental energy level extrapolation method, some excited state energy levels of the {Yb~I} ($Z=70$) atom including the $4f$ open shell are calculated. The advantages of the ridge regression algorithm are demonstrated by comparing it with Cowan's least squares results. In addition, the results obtained by the new method are compared with the experimental results and other theoretical results to demonstrate the reliability and accuracy of our approach

Vibration suppression of rotating nonlinear beam by nonlinear energy sink

In this paper, vibration suppression of a rotating nonlinear beam under the action of an external harmonic force is studied by a Nonlinear Energy Sink (NES). Dynamic model of the rotating nonlinear beam coupled with a NES is obtained by using quasi-Hamilton’s principle and Galerkin method. Then, harmonic balance method is used to acquire the analytic solution of the vibration amplitude of beam. In addition, the influences of rotating speed and NES parameters (mass, damping, nonlinear stiffness, and position of NES) are investigated in details

The polynomial dimensional decomposition method in a class of dynamical system with uncertainty

In this paper, polynomial dimensional decomposition (PDD) method is applied to study the dynamical model for the first time. PDD method can reserve the amplitude-frequency characteristics of the exact solution which is obtained by the Monte Carlo simulation (MCS) method except the frequency close to the resonance, the perturbations appear around the resonance frequency. All these results are shown on the two degrees of freedom (DOF) spring system with uncertainties; the dynamical characteristics of stiffness and hybrid uncertainty uncertainty are studied in seven cases respectively. The higher PDD order approximates better to the MCS results

Redefining the Caenorhabditis elegans DEG/ENaC Mechanosensory Channel Complex

Mechanosensation underlies multiple senses, such as touch, pain, hearing, and proprioception. The molecules that mediate most of the mechanical senses have not been identified. Genetic and molecular methods have identified several putative mechanosensitive proteins. However, how the mechanotransduction machineries organize and function remains largely unknown. To understand the organization of the mechanotransduction complex, I studied the DEG/ENaC mechanosensory channel that detects gentle touch in the six touch receptor neurons (TRNs) of C. elegans. Previous studies from our lab have suggested that this channel complex contains two pore-forming subunits MEC-4 and MEC-10 (DEG/ENaC proteins) and two auxiliary subunits MEC-6 (paraoxonase-like protein) and MEC-2 (stomatin-like protein). However, questions remain about what molecules really constitute this mechanosensory channel complex. Studying this particular DEG/ENaC channel in C. elegans will not only elucidate the organization of one major mechanosensory complex, but also improve our knowledge of other DEG/ENaC proteins, which are found in both vertebrates and invertebrates, and involved in various functions, e.g. mechanosensation, sodium taste, acid sensation, synaptic plasticity, and sodium homeostasis. My thesis research investigated the molecular organization and formation of the DEG/ENaC mechanosensory channel in C. elegans. In collaboration with Ehud Isacoff's lab, I analyzed the stoichiometry and co-localization of the potential channel subunits using single molecule optical imaging. In Xenopus oocytes, MEC-4 and MEC-10 form trimers, either of MEC-4 alone or of MEC-4 and MEC-10 in a ratio of 2:1. MEC-2 and MEC-6 do not seem to colocalize with the MEC-43 or MEC-42MEC-10 trimers at the single molecule level, and thus, may not be part of the channel complex. To study the role of MEC-6, I characterized its homologous protein POML-1. Compared to MEC-6, POML-1 appears to play a similar but relatively minor role in the TRNs. As with mec-6, loss of poml-1, completely suppressed mec-4(d) induced neuronal degeneration. [mec-4(d) encodes a hyperactive channel and causes neuronal degeneration in vivo]. Loss of poml-1 alone had no effect, but in sensitized background, it completely abolished touch sensitivity. Surprisingly, most of MEC-6 and POML-1 proteins were found in the endoplasmic reticulum (ER), rather than on the plasma membrane, consistent with the finding in Xenopus oocytes that MEC-6 is not part of the MEC-4 mechanosensory channel. I provided several lines of compelling evidence to demonstrate that MEC-6 and POML-1 are required for MEC-4 folding and transport, and likely function as ER chaperones. First, loss of these proteins dramatically reduced MEC-4 protein level, eliminated the punctate distribution of MEC-4 in the neuronal process, and altered the MEC-4 folding status in the TRNs. These phenotypes are also shared by calreticulin (CRT-1), a chaperone in the ER. Second, MEC-6 also substantially increased MEC-4 surface expression in Xenopus oocytes, though POML-1 and CRT-1 did not have the same effect in oocytes. Third, overexpressing a transport protein, SEC-24, partially rescued the transport defects caused the poml-1 and crt-1 mutations. Based on the finding that loss of poml-1 reduces MEC-4 protein levels and suppresses neurodegeneration caused by the hyperactive MEC-4(d) channel, I used the poml-1 deletion as a sensitized background to identify genes that normally inhibit MEC-4(d) neurotoxicity through a genetic screen. I found that the loss of two genes, mec-10 and C49G9.1, makes mec-4(d) more toxic. The proteins encoded by these genes affect mec-4(d) neurotoxicity through different mechanisms. MEC-10 inhibits MEC-4(d) without affecting MEC-4 surface expression. In contrast, both in vivo and in vitro data suggested that C49G9.1, a membrane protein specific to nematodes, can reduce MEC-4 surface expression, which contributes to, at least in part, its inhibitory effect on MEC-4(d). C49G9.1 does not incorporate into the MEC-4/MEC-10 channel, though they may transiently interact, because C49G9.1 did not appear to co-localize with MEC-4 either in vivo or in vitro, but co-immunoprecipitated with MEC-4. In summary, my doctoral research has refined the model of the MEC-4/MEC-10 complex. In particular, my studies resolved the subunits composition of DEG/ENaC channel at the single molecule level, by showing that they form MEC-42MEC-10 trimers in Xenopus oocytes. Notably, MEC-2 and MEC-6 may not be part of the complex. Indeed, I provided compelling evidence to demonstrate that MEC-6 and POML-1 are needed for MEC-4 folding and transport, and likely function as chaperones and/or assembly factors. In addition, I identified a novel membrane protein, C49G9.1, which negatively regulates MEC-4 surface expression and/or activities. This work has revised our understanding of a major mechanosensory complex and described a new class of chaperone proteins as well as a new inhibitor protein for DEG/ENaC proteins

Application of the polynomial dimensional decomposition method in a class of random dynamical systems

The polynomial dimensional decomposition (PDD) method is applied to study the amplitude-frequency response behaviors of dynamical system model in this paper. The first two order moments of the steady-state response of a dynamical random system are determined via PDD and Monte Carlo simulation (MCS) method that provides the reference solution. The amplitude-frequency behaviors of the approximately exact solution obtained by MCS method can be retained by PDD method except the interval close to the resonant frequency, where the perturbations may occur. First, the results are shown on the two degrees of freedom (DOFs) spring system with uncertainties; the dynamic behaviors of the uncertainties for mass, damping, stiffness and hybrid cases are respectively studied. The effects of PDD order to amplitude-frequency behaviors are also discussed. Second, a simple rotor system model with four random variables is studied to further verify the accuracy of the PDD method. The results obtained in this paper show that the PDD method is accurate and efficient in the dynamical model, providing the theoretical guidance to complexly nonlinear rotor dynamics models