1,422 research outputs found
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 -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}3\times10^{12}h^{-1}M_{\odot}R=5h^{-1}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
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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
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