Numerical Study on Interactional Aerodynamics of a Quadcopter in Hover with Overset Mesh in OpenFOAM

Interactional aerodynamics of a quadcopter in hover is numerically investigated in this study. The main objective is to understand major flow structures associated with unsteady airloads on multirotor aircraft. The overset mesh approach is used to resolve flow structures in unsteady simulation using the flow solver OpenFOAM. The current computational study demonstrates that aerodynamic interaction between quadcopter components strongly affects the rotor wake, generating interesting vortical structures. Multiple rotors in close proximity generate $\Omega$-shaped vortical structures merged from rotor-tip vortices. The fuselage of the current quadcopter deflects the wake flow of the four rotors towards the center of the vehicle. Such interactional aerodynamics, i.e., rotor-rotor and rotor-fuselage interaction, varies the inflow condition of a rotor blade during the rotor revolution. Therefore, the quadcopter experiences unsteady airloads per rotor revolution. Our study indicates that a typical quadcopter would experience 8/rev thrust variations, which are a combined outcome from 4/rev thrust variations on the rotor and 2/rev fluctuations on the fuselage. The current understanding of interactional aerodynamics could help to design reliable and efficient multicopter aircraft

A Second-order bias model for the Logarithmic Halo Mass Density

We present an analytic model for the local bias of dark matter halos in a LCDM universe. The model uses the halo mass density instead of the halo number density and is searched for various halo mass cuts, smoothing lengths, and redshift epoches. We find that, when the logarithmic density is used, the second-order polynomial can fit the numerical relation between the halo mass distribution and the underlying matter distribution extremely well. In this model the logarithm of the dark matter density is expanded in terms of log halo mass density to the second order. The model remains excellent for all halo mass cuts (from M_{cut}=3\times10^{11}$to$3\times10^{12}h^{-1}M_{\odot}$), smoothing scales (from$R=5h^{-1}$Mpc to$50h^{-1}$Mpc), and redshift ranges (from z=0 to 1.0) considered in this study. The stochastic term in the relation is found not entirely random, but a part of the term can be determined by the magnitude of the shear tensor.Comment: 8 pages, 7 figures, accepted for publication on Ap

Family Trips and Academic Achievement in Reading during Early Childhood: Evidence from a National Study

This study investigates a popular belief: family trips provide educational benefits for children. Based on the theoretical background of experiential learning, we empirically examine the impact of family trips on academic achievement in early childhood using Early Childhood Longitudinal Study - Kindergarten Class of 1998–99 (ECLS-K) data collected by the National Center for Educational Statistics (NCES). The 3,224 children included in the study are a nationally representative sample. The results show that family trips–especially those to museums, art galleries, and historical sites–has positive impact on children’s academic achievement in reading. As the experiential learning requires reflection and experimentation and is enhanced with repetition, learning from family trips occurs not immediately but rather over time. This study provides rationale for the promotion of family trips for their educational benefits and endorses further examination of different types of trips and travel

News Representation and Sense of Belonging Among Multicultural Audiences

This study seeks to understand the role of representation in news media, trust in news, and participation in multicultural audiences' sense of belonging to society. A multimodal survey combining online, CATI, and CAPI methods was conducted in Australia at the end of 2021 and early 2022 (N = 1,084). The top five non-English language communities in Australia (Arabic, Cantonese, Italian, Mandarin, and Vietnamese) were included in the survey, of which n = 851 were born overseas. The findings reveal a significant link between the perception of sufficient representation in Australian news media, trust in news, confidence to participate in society, and sense of belonging. When multicultural audiences see themselves fairly and adequately represented in the news, they are more likely to trust the news and participate in the community by discussing the news and current affairs. This, in turn, leads to a stronger sense of belonging to society. We also found confidence in English and time spent in Australia were important factors contributing to perceptions of representation. While the length of stay has a positive impact on the perception of representation among those with high confidence in English, this perception is significantly lower among those who have lower confidence. This result confirms the significant role language proficiency plays in migrants' experiences in the host country