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Errors and Accuracy Issues
Published in Basudeb Bhatta, Global Navigation Satellite Systems, 2021
Just six parameters (the Keplerian elements) can be used to describe a satellite following Keplerian motion with respect to the earth. They are: The semi major axis of the elliptical orbit.The eccentricity of the elliptical orbit.The inclination of the orbital plane to the equatorial plane.The right ascension of the ascending node.The argument of the perigee.The time at which the satellite passes the perigee.
Positioning peripheral vision warning devices for snowplough operations
Published in Don Harris, Engineering Psychology and Cognitive Ergonomics Volume Five, 2017
Jason Ward, Kip C.S. Smith, Brent Anders
The optimal location of a warning light will be a complex function determined by the interaction of the human visual system and the driver’s focus of attention. In this context, the chief constraint imposed by the visual system is the threshold for detecting objects on the visual periphery. The elliptical shape of the human eye is known to produce anisotropic changes in this threshold as function of the eccentricity from foveal focus. Lamble, Lassko and Summala (1999) found that resolution of moving stimuli degrades at a greater rate in the vertical periphery than in the horizontal periphery. In addition, research in the realm of attentional resolution suggests that resolution is more diminished in the lower visual field (in the distal field, the world) than the upper visual field (He, Cavanagh and Intriligator, 1996). Thus both psychophysical and cognitive studies provide reason to that the resolution of peripheral warning devices is sensitive to vertical and lateral location.
Why Are Rockets Needed?
Published in Travis S. Taylor, Introduction to Rocket Science and Engineering, 2017
We have discussed trajectories and orbits in enough detail at this point to look deeper at the flight path of ballistic missiles. In actuality, the flight path of a ballistic missile consists of three parts: (1) powered flight, (2) free-flight, and (3) reentry. Figure 2.25 illustrates these flight path components, as well as the fact that the free-flight trajectory of the missile is actually an elliptical conic section. The free-flight trajectory can be assumed to be a symmetrical ellipse that begins at MECO or at missile propellant burnout and continues until reentry. Reentry height, hre, and burnout height, hbo, are equal to each other. Also note that the periapsis of the ellipse is inside the radius of the Earth; otherwise, the missile would be in an elliptical orbit about the planet. There are solutions where the periapsis is outside the radius of the Earth, but the path of the ellipse is not. Such cases are not clear orbits about the planet and are instead a trajectory.
The effects of a standard elliptical vs. a modified elliptical with a converging footpath on lower limb kinematics and muscle activity
Published in Journal of Sports Sciences, 2020
Erik Hummer, Eryn Murphy, David N. Suprak, Lorrie Brilla, Jun G. San Juan
Elliptical trainers are a popular mode of cardiovascular exercise for people ranging from healthy individuals to those undergoing rehabilitation. When compared to overground walking, elliptical trainers had high coefficients of multiple correlations for hip (r = 0.85–0.89) and knee (r = 0.87–0.89) kinematics; although, elliptical trainers do elicit a greater amount of hip and knee flexion compared to overground walking (Lu et al., 2007; Burnfield et al., 2010, 2011). In addition, elliptical trainers have similar metabolic demands to treadmill jogging during submaximal exercise based on peak oxygen uptake (Brown et al., 2010). Elliptical trainers elicit higher muscle activity of the gluteus maximus (GM) and vastus lateralis (VL), and lower muscle activity for the semitendinosus (ST) and medial gastrocnemius muscles compared to walking (Burnfield et al., 2010). One favourable characteristic of elliptical trainers is lower tibial loads compared to common activities such as jogging (D’Lima et al., 2008; Kaplan et al., 2014). With similar kinematics and lower tibial loading, elliptical trainers have been used as an exercise modality for healthy populations, total knee arthroplasty (TKA) patients, and traumatic brain injuries (Buster et al., 2013; Burnfield et al., 2017; Chester et al., 2016; D’Lima et al., 2008). Exercising on elliptical trainers may be preferential for those wishing to decrease the amount of tibial loading while maintaining a similar exertion and oxygen uptake to jogging.