A unified gas kinetic scheme for transport and collision effects in plasma

In this study, the Vlasov-Poisson equation with or without collision term for plasma is solved by the unified gas kinetic scheme (UGKS). The Vlasov equation is a differential equation describing time evolution of the distribution function of plasma consisting of charged particles with long-range interaction. The distribution function is discretized in discrete particle velocity space. After the Vlasov equation is integrated in finite volumes of physical space, the numerical flux across a cell interface and source term for particle acceleration are computed to update the distribution function at next time step. The flux is decided by Riemann problem and variation of distribution function in discrete particle velocity space is evaluated with central difference method. A electron-ion collision model is introduced in the Vlasov equation. This finite volume method for the UGKS couples the free transport and long-range interaction between particles. The electric field induced by charged particles is controlled by the Poisson's equation. In this paper, the Poisson's equation is solved using the Green's function for two dimensional plasma system subjected to the symmetry or periodic boundary conditions. Two numerical tests of the linear Landau damping and the Gaussian beam are carried out to validate the proposed method. The linear electron plasma wave damping is simulated based on electron-ion collision operator. Compared with previous methods, it is shown that the current method is able to obtain accurate results of the Vlasov-Poisson equation with a time step much larger than the particle collision time. Highly non-equilibrium and rarefied plasma flows, such as electron flows driven by electromagnetic field, can be simulated easily.Comment: 33 pages, 13 figure

On the location of plumes and lateral movement of thermochemical structures with high bulk modulus in the 3-D compressible mantle

The two large low shear velocity provinces (LLSVPs) at the base of the lower mantle are prominent features in all shear wave tomography models. Various lines of evidence suggest that the LLSVPs are thermochemical and are stable on the order of hundreds of million years. Hot spots and large igneous province eruption sites tend to cluster around the edges of LLSVPs. With 3-D global spherical dynamic models, we investigate the location of plumes and lateral movement of chemical structures, which are composed of dense, high bulk modulus material. With reasonable values of bulk modulus and density anomalies, we find that the anomalous material forms dome-like structures with steep edges, which can survive for billions of years before being entrained. We find that more plumes occur near the edges, rather than on top, of the chemical domes. Moreover, plumes near the edges of domes have higher temperatures than those atop the domes. We find that the location of the downwelling region (subduction) controls the direction and speed of the lateral movement of domes. Domes tend to move away from subduction zones. The domes could remain relatively stationary when distant from subduction but would migrate rapidly when a new subduction zone initiates above. Generally, we find that a segment of a dome edge can be stationary for 200 million years, while other segments have rapid lateral movement. In the presence of time-dependent subduction, the computations suggest that maintaining the lateral fixity of the LLSVPs at the core-mantle boundary for longer than hundreds of million years is a challenge

The relationship between physical exercise and cognition in children with typical development and neurodevelopmental disorders

This research project sought to investigate the relationship between physical exercise and cognition in children with and without a neurodevelopmental condition. To achieve this aim, three approaches were undertaken to explore the exercise and cognition relationship. The first approach sought to understand the efficacy of exercise interventions on cognition in individuals with a neurodevelopmental disorder. The second approach was to understand the effectiveness of an exercise activity when compared to a cognitively-engaging tablet game activity on measures of implicit learning and attention in children with and without a neurodevelopmental condition. The third approach was to investigate if psychophysiological measures could account for the cognitive effect observed after exercising in children with and without a neurodevelopmental condition. Taking the approaches together, this research project focused on investigating the efficacy, effect, and mechanism of the exercise-cognition relationship. To investigate the efficacy of the exercise interventions, a meta-analytic review was conducted on 22 studies from the neurodevelopmental literature. The main findings from this meta-analysis revealed an overall small-to-medium effect size of exercise on cognition, supporting the efficacy of applying exercise interventions to young individuals with a neurodevelopmental disorder. Similar to the general population, physical exercise has been demonstrated to improve some but not all cognitive functions, with some individuals demonstrating no change in cognitive function after exercising. In terms of the effects of physical exercise, this project conducted an experimental study comparing a moderate-intensity exercise activity with a tablet game activity for a period of 12 minutes in 35 children aged 6-11 years. Overall, the study found that the effect of exercise was comparable to the tablet activity across the reaction time measures, but not on the accuracy performance of the implicit learning and attention tasks. Overall, exercise activity led to a better accuracy performance on implicit learning and executive attention compared to the tablet activity, particularly in children with a neurodevelopmental condition. The last part of this project was an extension of the experimental study whereby psychophysiological measures were investigated based on a proposed detrended fluctuation analysis (DFA). This investigation found that galvanic skin response (GSR), as indexed by its scaling exponent, was related to whether children revealed a change in cognitive function after receiving the exercise activity, particularly on executive attention. Importantly, this relationship was also able to account for children who did not demonstrate a cognitive effect of exercise. This result was not evident in the electroencephalogram (EEG) measures. This investigation concluded that the effect of exercise on executive attention was dependent on the interplay between an individual’s arousal system, cognitive task demand, and the novelty of the exercise activity. Taking the findings together, this project highlights the importance of individual differences to the exercise and cognition relationship. Specifically, this project demonstrated the feasibility of investigating the scaling exponent, via fractal analysis (e.g., DFA), as an index of individual differences. Additionally, fractal analysis is a valuable tool to assist in further understanding the mechanism underlying the exercise-cognition relationship, particularly on the influence of individual difference

Physical activity: Its implication on attention span and quality of life in children with autism spectrum disorder

The current study was designed to partially extend previous research (Nicholson, Kehle, Bray, & Heest, 2011; Rosenthal-Malek & Mitchell, 1997) by examining the effects of physical activity on the 1) attention span and 2) health-related quality of life (HRQoL) of autism spectrum disorder (ASD) children in Singapore. Male participants (N = 12) aged 2-6 years, diagnosed with ASD were randomly assigned to either a physical activity (experimental) or non-physical activity group (control). In the physical activity group, participants were administered 8 tri-cycling sessions; together, both groups of participants were measured for their attention span, and their parents completed the HRQoL questionnaires. The results revealed that as the exercise session increases, participants in the physical activity group demonstrated increasingly longer duration of attention span compared to the control group. These results further extended the findings of Nicholson et al. (2011) and Rosenthal-Malek and Mitchell (1997) that physical activity enhances cognition of ASD children. However, the results do not support the effects of physical activity on the overall HRQoL and instead revealed the improvement on the social functioning subscale. In general, these results suggested the beneficial effects of physical activity on ASD children and its incorporation into the early intervention should be recommended

An Optimization Scheduling Model for Wind Power and Thermal Power with Energy Storage System considering Carbon Emission Trading

Wind power has the characteristics of randomness and intermittence, which influences power system safety and stable operation. To alleviate the effect of wind power grid connection and improve power system’s wind power consumptive capability, this paper took emission trading and energy storage system into consideration and built an optimization model for thermal-wind power system and energy storage systems collaborative scheduling. A simulation based on 10 thermal units and wind farms with 2800 MW installed capacity verified the correctness of the models put forward by this paper. According to the simulation results, the introduction of carbon emission trading can improve wind power consumptive capability and cut down the average coal consumption per unit of power. The introduction of energy storage system can smooth wind power output curve and suppress power fluctuations. The optimization effects achieve the best when both of carbon emission trading and energy storage system work at the same time

A Robust Hessian-based Trust Region Algorithm for Spherical Conformal Parameterizations

Surface parameterizations are widely applied in computer graphics, medical imaging and transformation optics. In this paper, we rigorously derive the gradient vector and Hessian matrix of the discrete conformal energy for spherical conformal parameterizations of simply connected closed surfaces of genus-$0$. In addition, we give the sparsity structure of the Hessian matrix, which leads to a robust Hessian-based trust region algorithm for the computation of spherical conformal maps. Numerical experiments demonstrate the local quadratic convergence of the proposed algorithm with low conformal distortions. We subsequently propose an application of our method to surface registrations that still maintains local quadratic convergence

Yiqi Huoxue Huatan formula attenuates inflammation in chronic obstructive pulmonary disease by suppressing the activation of PI3K/AKT and NF-κB signaling pathways

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Polarization-based cyclic weak value metrology for angular velocity measurement

Weak value has been proved to amplify the detecting changes of the meters at the cost of power due to post-selection. Previous power-recycling schemes enable the failed post-selection photons to be reselected repeatedly, thus surpassing the upper noise limit and improving the precision of interferometric systems. Here we introduce three cyclic methods to improve the sensitivity of polarization-based weak-value-based angular velocity measurement: power-, signal- and dual-recycling schemes. By inserting one or two partially transmitting mirrors inside the system, both the power and precision of detected signals are greatly enhanced, and the dual-recycling scheme has wider optimal region than that of power- or signal-recycling schemes. Compared to non-polarization schemes, polarization-based schemes enjoy lower optical loss and unique cyclic directions. These reduce the crosstalk among different paths of light and, theoretically, eliminate the walk-off effect, thus towering in both theoretical performance and application.Comment: 7 pages, 3 figure

Strength distribution of cemented waste rock backfill: a similarity simulation experiment

Backfill of cemented waste rock into underground mined-out areas is an effective way to eliminate solid wastes and potential hazards in mines. To understand the backfill strength distribution law throughout the stope, similarity simulation experiments were conducted for direct-irrigating cemented waste rock backfill, and OpenCV and neural network were employed to analyze particle segregation and the spatial distribution of backfill strength. Results show that distinct gravitational segregation leads to an uneven and heterogeneous distribution of natural graded waste rocks in a similar model. Backfill strength near sidewalls and bottom of the model surpasses that of other areas. In the vertical direction, the average backfill strength increases with depth, ranging from 1.15 MPa at the topmost layer to 1.91 MPa at the bottommost layer. Horizontally, the average backfill strength near model boundaries is consistently higher than that at the model center, irrespective of the layer depth and orientation. Neural network prediction on spatial backfill strength proves reliable, exhibiting an average relative error of 4.12%, compared to the traditional surface fitting with a 10.20% error. Verification tests affirm the capability of the neural network model to accurately predict the anisotropic and nonlinear distribution of backfill strength in a large stope