Rotational and Translational Components of Motion Parallax: Observers' Sensitivity and Implications for Three-Dimensional Computer Graphics

The motion of objects during motion parallax can be decomposed into 2 observer-relative components: translation and rotation. The depth ratio of objects in the visual field is specified by the inverse ratio of their angular displacement (from translation) or equivalently by the inverse ratio of their rotations. Despite the equal mathematical status of these 2 information sources, it was predicted that observers would be far more sensitive to the translational than rotational component. Such a differential sensitivity is implicitly assumed by the computer graphics technique billboarding, in which 3-dimensional (3-D) objects are drawn as planar forms (i.e., billboards) maintained normal to the line of sight. In 3 experiments, observers were found to be consistently less sensitive to rotational anomalies. The implications of these findings for kinetic depth effect displays and billboarding techniques are discussed

Nutritional and Demographic Consequences of Varying Elk Migratory Behaviors

Elk (Cervus elaphus) populations in the American West exhibit wide variation in migratory behavior. The traditional view of elk migration holds that migratory elk move from winter range in order to track growth of highly nutritious fresh vegetation into higher elevation areas. Non-migratory elk forego this seasonal movement, typically foraging in lower elevation winter range areas throughout the summer. Although the effect of summer nutrition on elk body condition and reproductive success is well known, the nutritional and demographic consequences of these differing migratory behaviors remain unclear. We developed a predictive model of summer forage quality to compare the nutrition available to migrants and non-migrants in a partially migratory population of elk in western Montana. Non-migratory elk had access to significantly higher forage quality than their migratory counterparts; the lower forage quality available to migrants is predicted to result in reduced reproductive success based on published studies linking nutrition with elk demographic rates. We therefore expect non-migrants to have higher fecundity rates and to comprise a higher proportion of the population relative to migrants. Harvest management actions that reduce survival rates of non-migrants or increase survival rates of migrants may be an effective tool for maintaining migratory behavior in partially migratory populations

Spectroscopic Sensitivity

We describe the overall performance of the STIS CCD after HST Servicing Mission #4 and the associated updates to calibration reference files. Most aspects of CCD performance are found to be fairly consistent with extrapolations of the trends seen prior to the failure of STIS in August 2004. The CCD gain value for the CCDGAIN = 4 setting has been redetermined using net count ratios of standard star spectra taken in the CCDGAIN = 1 and CCDGAIN = 4 settings, resulting in a gain value of 4.016 ± 0.003 e − /DN, which is 0.5% lower than the value used for the calibration of archival STIS CCD data taken before August 2004. Finally, we identify two independent indications of a temperature dependence of the Charge Transfer Efficiency (CTE). However, more calibration data are needed to verify the significance of this effect and, if verified, to calibrate it as a function of CCD housing temperature (as a proxy for CCD chip temperature). This option will be reassessed later during the Cycle 17 calibration program.

High-Alpha Research Vehicle (HARV) longitudinal controller: Design, analyses, and simulation resultss

This paper describes the design, analysis, and nonlinear simulation results (batch and piloted) for a longitudinal controller which is scheduled to be flight-tested on the High-Alpha Research Vehicle (HARV). The HARV is an F-18 airplane modified for and equipped with multi-axis thrust vectoring. The paper includes a description of the facilities, a detailed review of the feedback controller design, linear analysis results of the feedback controller, a description of the feed-forward controller design, nonlinear batch simulation results, and piloted simulation results. Batch simulation results include maximum pitch stick agility responses, angle of attack alpha captures, and alpha regulation for full lateral stick rolls at several alpha's. Piloted simulation results include task descriptions for several types of maneuvers, task guidelines, the corresponding Cooper-Harper ratings from three test pilots, and some pilot comments. The ratings show that desirable criteria are achieved for almost all of the piloted simulation tasks

Hubble Space Telescope search for the transit of the Earth-mass exoplanet α Centauri Bb

Results from exoplanet surveys indicate that small planets (super-Earth size and below) are abundant in our Galaxy. However, little is known about their interiors and atmospheres. There is therefore a need to find small planets transiting bright stars, which would enable a detailed characterization of this population of objects. We present the results of a search for the transit of the Earth-mass exoplanet α Centauri Bb with the Hubble Space Telescope (HST). We observed α Centauri B twice in 2013 and 2014 for a total of 40h. We achieve a precision of 115ppm per 6-s exposure time in a highly saturated regime, which is found to be consistent across HST orbits. We rule out the transiting nature of α Centauri Bb with the orbital parameters published in the literature at 96.6 per cent confidence. We find in our data a single transit-like event that could be associated with another Earth-sized planet in the system, on a longer period orbit. Our programme demonstrates the ability of HST to obtain consistent, high-precision photometry of saturated stars over 26h of continuous observation

Hubble Space Telescope search for the transit of the Earth-mass exoplanet α Centauri B b

Results from exoplanet surveys indicate that small planets (super-Earth size and below) are abundant in our Galaxy. However, little is known about their interiors and atmospheres. There is therefore a need to find small planets transiting bright stars, which would enable a detailed characterization of this population of objects. We present the results of a search for the transit of the Earth-mass exoplanet α Centauri B b with the Hubble Space Telescope (HST). We observed α Centauri B twice in 2013 and 2014 for a total of 40 h. We achieve a precision of 115 ppm per 6-s exposure time in a highly saturated regime, which is found to be consistent across HST orbits. We rule out the transiting nature of α Centauri B b with the orbital parameters published in the literature at 96.6 per cent confidence. We find in our data a single transit-like event that could be associated with another Earth-sized planet in the system, on a longer period orbit. Our programme demonstrates the ability of HST to obtain consistent, high-precision photometry of saturated stars over 26 h of continuous observations

Design Specification for a Thrust-Vectoring, Actuated-Nose-Strake Flight Control Law for the High-Alpha Research Vehicle

Specifications for a flight control law are delineated in sufficient detail to support coding the control law in flight software. This control law was designed for implementation and flight test on the High-Alpha Research Vehicle (HARV), which is an F/A-18 aircraft modified to include an experimental multi-axis thrust-vectoring system and actuated nose strakes for enhanced rolling (ANSER). The control law, known as the HARV ANSER Control Law, was designed to utilize a blend of conventional aerodynamic control effectors, thrust vectoring, and actuated nose strakes to provide increased agility and good handling qualities throughout the HARV flight envelope, including angles of attack up to 70 degrees

Influence of Motor Planning on Distance Perception within the Peripersonal Space

We examined whether movement costs as defined by movement magnitude have an impact on distance perception in near space. In Experiment 1, participants were given a numerical cue regarding the amplitude of a hand movement to be carried out. Before the movement execution, the length of a visual distance had to be judged. These visual distances were judged to be larger, the larger the amplitude of the concurrently prepared hand movement was. In Experiment 2, in which numerical cues were merely memorized without concurrent movement planning, this general increase of distance with cue size was not observed. The results of these experiments indicate that visual perception of near space is specifically affected by the costs of planned hand movements