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Eye tracking (ET) holds potential for the early detection of autism spectrum disorder (ASD). To overcome the difficulties of working with young children, developing a short and informative paradigm is crucial for ET. We investigated the fixation times of 37 ASD and 37 typically developing (TD) children ages 4-6 watching a 10-second video of a female speaking. ASD children showed significant reductions in fixation time at six areas of interest. Furthermore, discriminant analysis revealed fixation times at the mouth and body could significantly discriminate ASD from TD with a classification accuracy of 85.1%, sensitivity of 86.5%, and specificity of 83.8%. Our study suggests that a short video clip may provide enough information to distinguish ASD from TD children.

Eye tracking (ET) holds potential for the early detection of autism spectrum disorder (ASD). To overcome the difficulties of working with young children, developing a short and informative paradigm is crucial for ET. We investigated the fixation times of 37 ASD and 37 typically developing (TD) children ages 4-6 watching a 10-second video of a female speaking. ASD children showed significant reductions in fixation time at six areas of interest. Furthermore, discriminant analysis revealed fixation times at the mouth and body could significantly discriminate ASD from TD with a classification accuracy of 85.1%, sensitivity of 86.5%, and specificity of 83.8%. Our study suggests that a short video clip may provide enough information to distinguish ASD from TD children., Author(s): Guobin Wan [sup.1] , Xuejun Kong [sup.2] , Binbin Sun [sup.1] , Siyi Yu [sup.3] , Yiheng Tu [sup.3] , Joel Park [sup.3] , Courtney Lang [sup.3] , Madelyn [...]

Background: Children with autism spectrum disorder (ASD) have been observed to be associated with fixation abnormality as measured eye tracking, but the dynamics behind fixation patterns across age remain unclear. Materials and Methods: In this study, we investigated gaze patterns between toddlers and preschoolers with and without ASD while they viewed video clips and still images (i.e., mouth-moving face, biological motion, mouthing face vs. moving object, still face picture vs. objects, and moving toys). Results: We found that the fixation time percentage of children with ASD showed significant decrease compared with that of TD children in almost all areas of interest (AOI) except for moving toy (helicopter). We also observed a diagnostic group (ASD vs. TD) and chronological age (Toddlers vs. preschooler) interaction for the eye AOI during the mouth-moving video clip. Support vector machine analysis showed that the classifier could discriminate ASD from TD in toddlers with an accuracy of 80% and could discriminate ASD from TD in preschoolers with an accuracy of 71%. Conclusion: Our results suggest that toddlers and preschoolers may be associated with both common and distinct fixation patterns. A combination of eye tracking and machine learning methods has the potential to shed light on the development of new early screening/diagnosis methods for ASD. [ABSTRACT FROM AUTHOR]

In order to decelerate a forward-moving submarine rapidly, often the propeller of the submarine is placed abruptly into reverse rotation, causing the propeller to generate a thrust force in the direction opposite to the submarine's motion. This maneuver is known as the 'crashback' maneuver. During crashback, the relative flow velocities in the vicinity of the propeller lead to the creation of a ring vortex around the propeller. This vortex has an unsteady asymmetry, which produces off-axis forces and moments on the propeller that are transmitted to the submarine. Tests were conducted in the William B. Morgan Large Cavitation Channel using an existing submarine model and propeller. A range of steady crashback conditions with fixed tunnel and propeller speeds was investigated. The dimensionless force and moment data were found to collapse well when plotted against the parameter [eta], which is defined as the ratio of the actual propeller speed to the propeller speed required for self-propulsion in forward motion. Unsteady crashback maneuvers were also investigated with two different types of simulations in which propeller and tunnel speeds were allowed to vary. It was noted during these simulations that the peak out-of-plane force and moment coefficient magnitudes in some cases exceeded those observed during the steady crashback measurements. Flow visualization and LDV studies showed that the ring vortex structure varied from an elongated vortex structure centered downstream of the propeller to a more compact structure that was located nearer the propeller as [eta] became more negative, up to [eta] = -0.8. For more negative values of [eta], the vortex core appeared to move out toward the propeller tip. [DOI: 10.1115/1.2813123]

The methodology for hydrodynamic characterization of a very large water tunnel is described. Results are presented for the U. S. Navy William B. Morgan Large Cavitation Channel in Memphis, Tennessee, the world's largest water tunnel. Three key characteristics of tunnel velocity were measured: temporal stability, spatial uniformity, and turbulence. The velocity stability at a single point for run times greater than 2 h was measured as [+ or -] 0.15% at the 95% confidence level for velocities from 0.5 to 18 m/s(1.6-59 ft/s). The spatial nonuniformity for the axial velocity component was [+ or -] 0.34 to [+ or -] 0.60% for velocities from 3 to 16 m/s(9.8-52 ft/s). The relative turbulence intensity was measured as 0.2-0.5% depending on tunnel velocity. [DOI: 10.1115/1.2060740]

When a submarine executes a high-speed turn, the sail experiences a crossflow velocity component, creating a vortex at the sail tip. The flowfield induced by the vortex creates higher pressures on the hull deck and lower pressures on the keel, leading to a nose-up pitching moment. Tests to examine such flows were conducted in the U.S. Navy's William B. Morgan Large Cavitation Channel in Memphis, Tennessee. A submarine model of 6.92-m length was tested at drift angles of 0, 5, and 9.5 deg, with the sail on and off, and at speeds up to 14.9 m/s. Pressure distributions and laser Doppler velocimeter surveys were obtained at two axial locations. Forces and moments were measured using an internal force balance. The pressure distributions were integrated to obtain section force coefficients, and the velocity data were used to estimate the vortex circulation. The pressure distributions were consistent with the hypothesized mechanism by which the vortex created the nose-up pitching moment. The pitching moment and sectional force coefficients demonstrated the nonlinear variations with drift angle predicted by theory. The circulation values were consistently somewhat higher than those obtained by other researchers.