6,296 research outputs found
Sensitivity analysis of the space shuttle to ascent wind profiles
A parametric sensitivity analysis of the space shuttle ascent flight to the wind profile is presented. Engineering systems parameters are obtained by flight simulations using wind profile models and samples of detailed (Jimsphere) wind profile measurements. The wind models used are the synthetic vector wind model, with and without the design gust, and a model of the vector wind change with respect to time. From these comparison analyses an insight is gained on the contribution of winds to ascent subsystems flight parameters
Stretching and relaxation dynamics in double stranded DNA
We study numerically the mechanical stability and elasticity properties of
duplex DNA molecules within the frame of a network model incorporating
microscopic degrees of freedom related with the arrangement of the base pairs.
We pay special attention to the opening-closing dynamics of double-stranded DNA
molecules which are forced into non-equilibrium conformations. Mechanical
stress imposed at one terminal end of the DNA molecule brings it into a
partially opened configuration. We examine the subsequent relaxation dynamics
connected with energy exchange processes between the various degrees of freedom
and structural rearrangements leading to complete recombination to the
double-stranded conformation. The similarities and differences between the
relaxation dynamics for a planar ladder-like DNA molecule and a twisted one are
discussed in detail. In this way we show that the attainment of a
quasi-equilibrium regime proceeds faster in the case of the twisted DNA form
than for its thus less flexible ladder counterpart. Furthermore we find that
the velocity of the complete recombination of the DNA molecule is lower than
the velocity imposed by the forcing unit which is in compliance with the
experimental observations for the opening-closing cycle of DNA molecules.Comment: 21 pages, 9 figure
GAMBLINGLESS: FOR LIFE study protocol: a pragmatic randomised trial of an online cognitive–behavioural programme for disordered gambling
This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0
Numerical simulations of string networks in the Abelian-Higgs model
We present the results of a field theory simulation of networks of strings in
the Abelian Higgs model. Starting from a random initial configuration we show
that the resulting vortex tangle approaches a self-similar regime in which the
length density of lines of zeros of reduces as . We demonstrate
that the network loses energy directly into scalar and gauge radiation. These
results support a recent claim that particle production, and not gravitational
radiation, is the dominant energy loss mechanism for cosmic strings. This means
that cosmic strings in Grand Unified Theories are severely constrained by high
energy cosmic ray fluxes: either they are ruled out, or an implausibly small
fraction of their energy ends up in quarks and leptons.Comment: 4pp RevTeX, 3 eps figures, clarifications and new results included,
to be published in Phys. Rev. Let
Prevention of mother-to-child transmission of HIV and the health-related Millennium Development Goals: time for a public health approach.
Aviation Psychology: Cognition and Personality
This study has two main objectives. The first is to measure the personality traits of aviation students at EKU. Recent research indicates the existence of a distinct pilot personality profile, characterized by heightened emotional stability and conscientiousness compared to the general population. The current study will evaluate aviation students at EKU and see how they compare to that specific profile. The second objective is to evaluate aviation students\u27 confidence in their visual abilities during flight and to see whether certain interventions can help them better calibrate their confidence with their actual abilities. Awareness of cognitive limitations is vital for pilots as failure to recognize them can lead to catastrophic consequences. Results will be analyzed to determine the relationship between personality traits, aviation outcomes, and perceptions of visual awareness. Findings from this study could inform aviation instructors, advisors, and others about the role of personality in aviation education and the efficacy of interventions targeting perceptual limitations. This integrated approach aims to enhance aviation training by addressing both individual differences and perceptual challenges encountered in real-world aviation settings
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