Gravito-electromagnetic perturbations of MOG black holes with a cosmological constant: Quasinormal modes and Ringdown waveforms

In this paper, we present black hole solutions with a cosmological constant in the MOG theory, where the strength of the gravitational constant is determined by $G = G_\text{N}(1+\alpha)$. We derive the master equations for gravito-electromagnetic perturbations and numerically solve for the Quasinormal Mode (QNM) spectrum and the ringdown waveforms. Our results show that increasing either the MOG parameter $\alpha$ or the cosmological constant $\Lambda$ leads to a decrease in both the real and imaginary parts of the QNM frequencies for electromagnetic and gravitational modes, compared to standard Schwarzschild-de Sitter (S-dS) or MOG black holes, respectively. Meanwhile, the result indicates that in the MOG-de Sitter spacetime, the frequencies for electromagnetic and gravitational modes display strict isospectrality, and exhibit the same ringdown waveforms. Our findings have implications for the ringdown phase of mergers involving massive compact objects, which is of particular relevance given the recent detections of gravitational waves by LIGO.Comment: 16pages, 6 figure

QNMs of slowly rotating Einstein-bumblebee Black Hole

We have studied the quasinormal modes (QNMs) of a slowly rotating black hole with Lorentz-violating parameter in Einstein-bumblebee gravity. We analyse the slow rotation approximation of the rotating black hole in the Einstein-bumblebee gravity, and obtain the master equations for scalar perturbation, vector perturbation and axial gravitational perturbation, respectively. Using the matrix method and the continuous fraction method, we numerically calculate the QNM frequencies. In particular, for scalar field, it shows that the QNMs up to the second order of rotation parameter have higher accuracy. The numerical results show that, for both scalar and vector fields, the Lorentz-violating parameter has a significant effect on the imaginary part of the QNM frequencies, while having a relatively smaller impact on the real part of the QNM frequencies. But for axial gravitational perturbation, the effect of increasing the Lorentz-violating parameter $\ell$ is similar to that of increasing the rotation parameter $\tilde{a}$.Comment: 16 pages, 6 figure

Neural learning enhanced variable admittance control for human-robot collaboration

© 2013 IEEE. In this paper, we propose a novel strategy for human-robot impedance mapping to realize an effective execution of human-robot collaboration. The endpoint stiffness of the human arm impedance is estimated according to the configurations of the human arm and the muscle activation levels of the upper arm. Inspired by the human adaptability in collaboration, a smooth stiffness mapping between the human arm endpoint and the robot arm joint is developed to inherit the human arm characteristics. The estimation of stiffness term is generalized to full impedance by additionally considering the damping and mass terms. Once the human arm impedance estimation is completed, a Linear Quadratic Regulator is employed for the calculation of the corresponding robot arm admittance model to match the estimated impedance parameters of the human arm. Under the variable admittance control, robot arm is governed to be complaint to the human arm impedance and the interaction force exerted by the human arm endpoint, thus the relatively optimal collaboration can be achieved. The radial basis function neural network is employed to compensate for the unknown dynamics to guarantee the performance of the controller. Comparative experiments have been conducted to verify the validity of the proposed technique

Study on Emergency Response Rank Mode of Flammable and Explosive Hazardous Materials Road Transportation

AbstractHazardous Materials (Hazmat) road transport is a hot issue of societal public safety, and it is extremely important to quickly response and rescue emergency accidents. In this paper, according to fire risk characteristics of transporting flammable and explosive hazmat by road, it was identified and analyzed on the representative hazmat leakage scenarios and the methods of determination of accident emergency regions, and a comprehensive systematic framework of emergency response rank mode for hazmat accidents by road was proposed. Moreover, some recommended practice about initial accident region of transportation of hazmat from NFPA471 and ERG2008 was described, and it was put forward on a quantitative approach to determine the emergency response rank for hazmat road accidents, based utilizing death toll, individual risk and societal risk as an emergency rank criterion. This research pays a very important role in the emergency response and helps the fire commanders to implement the rescue efficiently in hazmat transport accidents by road

Upregulation of NUAK2: A novel prognostic marker in breast cancer

Background. Breast cancer is the most commonly diagnosed neoplasm in women worldwide. New molecular biomarkers and effective prognostic models are being developed. This study aimed to investigate the clinical and prognostic significance of NUAK2 expression in patients with breast cancer. Methods. The expression of NUAK 2 was examined in breast cancer cells and tissues by real-time PCR, western blotting, and immunohistochemical staining. CCK-8 and colony formation assays were performed to verify the effect of NUAK2 on the proliferation and tumor progression of breast cancer cells. A tumor formation assay in nude mice was performed to analyze the effect of NUAK2 on the tumorigenicity of breast cancer cells. Results. The expression of NUAK2 in breast cancer tissues was higher than that in paracarcinoma and normal breast tissues. The overall survival of patients with high NUAK2 expression was significantly lower than that of patients with low NUAK2 expression. Multivariate analyses indicated that NUAK2 was an independent prognostic indicator of survival in breast cancer. In vitro experiments demonstrated that knocking down NUAK2 in breast cancer cells inhibited cell proliferation and tumor-forming ability, and overexpression of NUAK2 showed the opposite effects. NUAK2 overexpression promoted the tumorigenicity of breast cancer cells in vivo. Conclusion. These findings suggest that NUAK2 is involved in breast cancer development and progression. NUAK2 may be a valuable prognostic indicator in patients with breast cancer

Learning compliant robotic movements based on biomimetic motor adaptation

It is one of the great challenges for a robot to learn compliant movements in interaction tasks. The robot can easily acquire motion skills from a human tutor by kinematics demonstration, however, this becomes much more difficult when it comes to the compliant skills. This paper aims to provide a possible solution to address this problem by proposing a two-stage approach. In the first stage, the human tutor demonstrates the robot how to perform a task, during which only motion trajectories are recorded without the involvement of force sensing. A dynamical movement primitives (DMPs) model which can generate human-like motion is then used to encode the kinematics data. In the second stage, a biomimetic controller, which is inspired by the neuroscience findings in human motor learning, is employed to obtain the desired robotic compliant behaviors by online adapting the impedance profiles and the feedforward torques simultaneously. Several tests are conducted to validate the effectiveness of the proposed approach

Substantially enhanced plasticity of bulk metallic glasses by densifying local atomic packing

Common wisdom to improve ductility of bulk metallic glasses (BMGs) is to introduce local loose packing regions at the expense of strength. Here the authors enhance structural fluctuations of BMGs by introducing dense local packing regions, resulting in simultaneous increase of ductility and strength

Superconducting Ti15Zr15Nb35Ta35 High-Entropy Alloy With Intermediate Electron-Phonon Coupling

The body-centered cubic (BCC) Ti15Zr15Nb35Ta35 high-entropy alloy showed superconducting behavior at around 8 K. The electronic specific heat coefficient γ and the lattice specific heat coefficient β were determined to be γ = 9.3 ± 0.1 mJ/mol K2 and β = 0.28 ± 0.01 mJ/mol K4, respectively. It was found that the electronic specific heat Ces does follow the exponential behavior of the Bardeen-Cooper-Schrieffer (BCS) theory. Nevertheless, the specific heat jump (ΔC/γTc) at the superconducting transition temperature which was determined to be 1.71 deviates appreciably from that for a weak electron-phonon coupling BCS superconductor. Within the framework of the strong-coupled theory, our analysis suggests that theTi15Zr15Nb35Ta35 HEA is an intermediate electron-phonon coupled BCS-type superconductor