A novel interplanetary communications relay

A case study of a potential Earth-Mars interplanetary communications relay, designed to ensure continuous communications, is detailed. The relay makes use of orbits based on artificial equilibrium points via the application of continuous low thrust, which allows a spacecraft to hover above the orbital plane of Mars and thus ensure communications when the planet is occulted with respect to the Earth. The artificial equilibria of two different low-thrust propulsion technologies are considered: solar electric propulsion, and a solar sail/solar electric propulsion hybrid. In the latter case it is shown that the combination of sail and solar electric propulsion may prove advantageous, but only under specific circumstances of the relay architecture suggested. The study takes into account factors such as the spacecraft's power requirements and communications band utilized to determine the mission and system architecture. A detailed contingency analysis is considered for recovering the relay after increasing periods of spacecraft motor failure, and combined with a consideration for how best to deploy the relay spacecraft to maximise propellant reserves and mission duration

Particle-laden swirling free jets - Measurements and predictions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76206/1/AIAA-1987-303-928.pd

Adult Cognitive and Non-cognitive Skills: An Overview of Existing PIAAC Data

As of summer 2019, more than 60 PIAAC datasets from participating countries worldwide were available for research purposes. These datasets can be differentiated, for example, in terms of their accessibility, the extent of the information provided, the population group in focus, and the design of the underlying study. PIAAC Public Use Files, for instance, are freely available and are therefore highly anonymised, whereas PIAAC Scientific Use Files are available only for scientific research purposes and provide access to more detailed variables. The majority of the PIAAC data are available as public use files, but some participating countries (e.g. Germany and the United States) have also made several scientific use files or other extended file versions available to the research community. Some of the available PIAAC datasets focus on specific population groups - for example, the incarcerated adult population in the United States. Regarding the design of the underlying studies, most available datasets are cross-sectional, but some longitudinal data already exist (e.g. PIAAC-L in Germany). The present chapter provides an overview of the structure, accessibility, and use of the PIAAC datasets available worldwide

Using Flight Manual Data To Derive Aero-Propulsive Models For

The Center/TRACON Automaton System (CTAS) is a set of air traffic management tools developed by NASA in conjunction with the FAA. As part of its functionality, CTAS predicts aircraft flight trajectories using aeropropulsive models and the kinetic equations of motion for various flight conditions including climbs. Precise aeropropulsive models for all aircraft types are not yet available to NASA researchers. In an effort to improve climb trajectory prediction of jet aircraft for which CTAS does not have a precise aero-propulsive model, a technique was developed to derive an aero-propulsive model from readily available time-to-climb data found in flight manuals. A case study was performed on a Boeing 737-400, for which time-to-climb data and aero-propulsive model data were known. A new aero-propulsive model, identified by three aerodynamic and one propulsive parameter, was derived from the time-to-climb data. The results showed it was possible to derive an aero-propulsive model for an aircraft type that will allow CTAS to compute time-to-climb for a range of climb speeds that agree closely with known data. This technique was then applied to a Learjet 60, an aircraft type for which a precise aero-propulsive model is not available. A comparison of top-of-climb predictions made with a derived aero-propulsive model and actual top-ofclimb from Learjet 60 radar track data reveal close agreement

Abstract Review Eye

In the last two decades, research has shown that eye movement trajectories can be modified by situational determinants. These modifications can inform us about the mechanisms that control eye movements and they can yield information about the oculomotor, memory and attention system that is not easily obtained via other sources. Eye movement trajectories can deviate either towards or away from elements in the visual field. We review the conditions in which these deviations are found and the mechanisms underlying trajectory deviations. It is argued that deviations towards an element are caused by the unresolved competition in the oculomotor system between elements in a visual scene. Deviations away from an element are mainly observed in situations in which top-down preparation can influence the target selection process, but the exact cause of such deviations remains unclear