时域谐波平衡求解器中非物理解出现根源探析

The time domain harmonic balance method is an attractive reduced order method of analyzing unsteady flow for turbomachines. However, the method can admit non-physical solutions. Non-physical solutions were encountered from a three-blade-row compressor configuration in a time domain harmonic balance analysis. This paper aims to investigate the root cause of the non-physical solutions. The investigation involves several strategies, which include increasing the number of harmonics, increasing the number of time instants, including scattered modes,including the rotor-rotor interaction, and the use of a new method-the approximate time domain nonlinear harmonic method. Numerical analyses pertinent to each strategy are presented to reveal the root cause of the non-physical solution. It is found that the nonlinear interaction of unsteady flow components with different fundamental frequencies is the cause of the non-physical solution. The non-physical solution can be eliminated by incorporating extra scattered modes or using the approximate time domain nonlinear harmonic method.

Low Frequency of Leisure-Time Activities Correlates with Cognitive Decline and Apathy in Patients with Parkinson’s Disease

Objective: The purpose of this study is to investigate habitual leisure-time activities (physical and non-physical leisure activities) in patients with Parkinson’s disease (PD), and to determine any potential benefits of these activities on cognitive functions and emotional symptoms. Methods: Thirty-two patients with PD and 25 demographically-matched healthy controls participated in the present study. Neuropsychological tests (Wisconsin Card Sorting Test, Trail Making Test, Digit Span Test, Verbal Fluency Test, and Japanese Verbal Learning Test), assessment of emotional sym- ptoms, and interviews for confirmation of habitual leisure-time activities were conducted for all participants. Results: Patients with PD significantly showed the lower frequency of both physical and non-physical leisure activities than healthy controls. Compared to patients who engaged in physical leisure activities, patients who did not engage in such activities performed worse on the Trail Making Test (TMT-B, and TMT-B minus A). Moreover, patients who engaged in non-physical leisure activities were less apathetic than patients who did not engage in such activities. Conclusions: Our preliminary study shows that habitual leisure-time activities correlate with cognitive function and emotions in patients with PD. Reducing sedentary lifestyles and promoting habitual leisure-time activities may be helpful for preventing cognitive decline and apathy.

Correlates of Parental Choice of Child Discipline Methods in Ghana: A Multilevel Modeling Approach

This study applied multilevel modeling to investigate the impact of observed predictors and different levels or groups that households belong, on parents’ choice of discipline methods using data from 8156 households derived from a nationwide survey by the Ghana Statistical Service (GSS) in 2011. The aim of the study is to provide in-depth information on why parents choose particular discipline methods as corrective measures to reduce unwanted child behaviour in the present and to increase desirable ones in the future. The results of the study show that, religion and age-group of household heads have significant effect on household’s likelihood to choose physical discipline methods whereas the wealth index of a household and ethnicity of the household head, have significant effect on households’ likelihood to choose non-physical and psychological aggression methods. The results further show significant contextual effect on the differences in choices of parents at the household and regional levels. The choice of physical discipline methods by parents was consistent across households and regional levels unlike non-physical and psychological aggression methods whose application varied across the regions. Households in the Northern, Eastern and Volta regions mostly chose to apply physical discipline methods whereas in the Upper West, Western and Northern regions the most chosen discipline methods were non-physical discipline methods. Psychological aggression discipline methods were predominantly applied in the Upper East, Central and Northern regions of the country.

A Robust Immersed Boundary-Lattice Boltzmann Method for Simulation of Fluid-Structure Interaction Problems

A robust immersed boundary-lattice Boltzmann method(IB-LBM)is proposed to simulate fluid-structure interaction(FSI)problems in this work.Compared with the conventional IB-LBM,the current method employs the fractional step technique to solve the lattice Boltzmann equation(LBE)with a forcing term.Consequently,the non-physical oscillation of body force calculation,which is frequently encountered in the traditional IB-LBM,is suppressed greatly.It is of importance for the simulation of FSI problems.In the meanwhile,the no-slip boundary condition is strictly satisfied by using the velocity correction scheme.Moreover,based on the relationship between the velocity correction and forcing term,the boundary force can be calculated accurately and easily.A few test cases are first performed to validate the current method.Subsequently,a series of FSI problems,including the vortex-induced vibration of a circular cylinder,an elastic filament flapping in the wake of a fixed cylinder and sedimentation of particles,are simulated.Based on the good agreement between the current results and those in the literature,it is demonstrated that the proposed IB-LBMhas the capability to handle various FSI problems effectively.