School of Medicine and Department of Anatomy History

This departmental history was written on the occasion of the UND Centennial in 1983. Supplemental information on the Anatomy Department was added at a later date.https://commons.und.edu/departmental-histories/1109/thumbnail.jp

Subsonic phase transition waves in bistable lattice models with small spinodal region

Phase transitions waves in atomic chains with double-well potential play a fundamental role in materials science, but very little is known about their mathematical properties. In particular, the only available results about waves with large amplitudes concern chains with piecewise-quadratic pair potential. In this paper we consider perturbations of a bi-quadratic potential and prove that the corresponding three-parameter family of waves persists as long as the perturbation is small and localised with respect to the strain variable. As a standard Lyapunov-Schmidt reduction cannot be used due to the presence of an essential spectrum, we characterise the perturbation of the wave as a fixed point of a nonlinear and nonlocal operator and show that this operator is contractive in a small ball in a suitable function space. Moreover, we derive a uniqueness result for phase transition waves with certain properties and discuss the kinetic relation.Comment: revised version with extended introduction, improved perturbation method, and novel uniqueness result; 20 pages, 5 figure

Quantum dynamics of two bosons in an anharmonic trap: Collective vs internal excitations

This work deals with the effects of an anharmonic trap on an interacting two-boson system in one dimension. Our primary focus is on the role of the induced coupling between the center of mass and the relative motion as both anharmonicity and the (repulsive) interaction strength are varied. The ground state reveals a strong localization in the relative coordinate, counteracting the tendency to fragment for stronger repulsion. To explore the quantum dynamics, we study the system's response upon (i) exciting the harmonic ground state by continuously switching on an additional anharmonicity, and (ii) displacing the center of mass, this way triggering collective oscillations. The interplay between collective and internal dynamics materializes in the collapse of oscillations, which are explained in terms of few-mode models.Comment: 8 pages, 7 figure

Water Detection Based on Sky Reflections

This software has been designed to detect water bodies that are out in the open on cross-country terrain at mid- to far-range (approximately 20 100 meters), using imagery acquired from a stereo pair of color cameras mounted on a terrestrial, unmanned ground vehicle (UGV). Non-traversable water bodies, such as large puddles, ponds, and lakes, are indirectly detected by detecting reflections of the sky below the horizon in color imagery. The appearance of water bodies in color imagery largely depends on the ratio of light reflected off the water surface to the light coming out of the water body. When a water body is far away, the angle of incidence is large, and the light reflected off the water surface dominates. We have exploited this behavior to detect water bodies out in the open at mid- to far-range. When a water body is detected at far range, a UGV s path planner can begin to look for alternate routes to the goal position sooner, rather than later. As a result, detecting water hazards at far range generally reduces the time required to reach a goal position during autonomous navigation. This software implements a new water detector based on sky reflections that geometrically locates the exact pixel in the sky that is reflecting on a candidate water pixel on the ground, and predicts if the ground pixel is water based on color similarity and local terrain feature

Multi-Sensor Mud Detection

Robust mud detection is a critical perception requirement for Unmanned Ground Vehicle (UGV) autonomous offroad navigation. A military UGV stuck in a mud body during a mission may have to be sacrificed or rescued, both of which are unattractive options. There are several characteristics of mud that may be detectable with appropriate UGV-mounted sensors. For example, mud only occurs on the ground surface, is cooler than surrounding dry soil during the daytime under nominal weather conditions, is generally darker than surrounding dry soil in visible imagery, and is highly polarized. However, none of these cues are definitive on their own. Dry soil also occurs on the ground surface, shadows, snow, ice, and water can also be cooler than surrounding dry soil, shadows are also darker than surrounding dry soil in visible imagery, and cars, water, and some vegetation are also highly polarized. Shadows, snow, ice, water, cars, and vegetation can all be disambiguated from mud by using a suite of sensors that span multiple bands in the electromagnetic spectrum. Because there are military operations when it is imperative for UGV's to operate without emitting strong, detectable electromagnetic signals, passive sensors are desirable. JPL has developed a daytime mud detection capability using multiple passive imaging sensors. Cues for mud from multiple passive imaging sensors are fused into a single mud detection image using a rule base, and the resultant mud detection is localized in a terrain map using range data generated from a stereo pair of color cameras

Using Thermal Radiation in Detection of Negative Obstacles

A method of automated detection of negative obstacles (potholes, ditches, and the like) ahead of ground vehicles at night involves processing of imagery from thermal-infrared cameras aimed at the terrain ahead of the vehicles. The method is being developed as part of an overall obstacle-avoidance scheme for autonomous and semi-autonomous offroad robotic vehicles. The method could also be applied to help human drivers of cars and trucks avoid negative obstacles -- a development that may entail only modest additional cost inasmuch as some commercially available passenger cars are already equipped with infrared cameras as aids for nighttime operation

Intraspeaker Comparisons of Acoustic and Articulatory Variability in American English /r/ Productions

The purpose of this report is to test the hypothesis that speakers utilize an acoustic, rather than articulatory, planning space for speech production. It has been well-documented that many speakers of American English use different tongue configurations to produce /r/ in different phonetic contexts. The acoustic planning hypothesis suggests that although the /r/ configuration varies widely in different contexts, the primary acoustic cue for /r/, a dip in the F3 trajectory, will be less variable due to tradeoffs in articulatory variability, or trading relations, that help maintain a relatively constant F3 trajectory across phonetic contexts. Acoustic data and EMMA articulatory data from seven speakers producing /r/ in different phonetic contexts were analyzed. Visual inspection of the EMMA data at the point of F3 minimum revealed that each speaker appeared to use at least two of three trading relation strategies that would be expected to reduce F3 variability. Articulatory covariance measures confirmed that all seven speakers utilized a trading relation between tongue back height and tongue back horizontal position, six speakers utilized a trading relation between tongue tip height and tongue back height, and the speaker who did not use this latter strategy instead utilized a trading relation between tongue tip height and tongue back horizontal position. Estimates of F3 variability with and without the articulatory covariances indicated that F3 would be much higher for all speakers if the articulatory covariances were not utilized. These conclusions were further supported by a comparison of measured F3 variability to F3 variabilities estimated from the pellet data with and without articulatory covariances. In all subjects, the actual F3 variance was significantly lower than the F3 variance estimated without articulatory covariances, further supporting the conclusion that the articulatory trading relations were being used to reduce F3 variability. Together, these results strongly suggest that the neural control mechanisms underlying speech production make elegant use of trading relations between articulators to maintain a relatively invariant acoustic trace for /r/ across phonetic contexts

Intraspeaker Comparisons of Acoustic and Articulatory Variability in American English /r/ Productions

The purpose of this report is to test the hypothesis that speakers utilize an acoustic, rather than articulatory, planning space for speech production. It has been well-documented that many speakers of American English use different tongue configurations to produce /r/ in different phonetic contexts. The acoustic planning hypothesis suggests that although the /r/ configuration varies widely in different contexts, the primary acoustic cue for /r/, a dip in the F3 trajectory, will be less variable due to tradeoffs in articulatory variability, or trading relations, that help maintain a relatively constant F3 trajectory across phonetic contexts. Acoustic data and EMMA articulatory data from seven speakers producing /r/ in different phonetic contexts were analyzed. Visual inspection of the EMMA data at the point of F3 minimum revealed that each speaker appeared to use at least two of three trading relation strategies that would be expected to reduce F3 variability. Articulatory covariance measures confirmed that all seven speakers utilized a trading relation between tongue back height and tongue back horizontal position, six speakers utilized a trading relation between tongue tip height and tongue back height, and the speaker who did not use this latter strategy instead utilized a trading relation between tongue tip height and tongue back horizontal position. Estimates of F3 variability with and without the articulatory covariances indicated that F3 would be much higher for all speakers if the articulatory covariances were not utilized. These conclusions were further supported by a comparison of measured F3 variability to F3 variabilities estimated from the pellet data with and without articulatory covariances. In all subjects, the actual F3 variance was significantly lower than the F3 variance estimated without articulatory covariances, further supporting the conclusion that the articulatory trading relations were being used to reduce F3 variability. Together, these results strongly suggest that the neural control mechanisms underlying speech production make elegant use of trading relations between articulators to maintain a relatively invariant acoustic trace for /r/ across phonetic contexts

Numerical modeling of the equilibrium shapes of a ferrofluid drop in an external magnetic field

A numerical solution strategy for calculating equilibrium free surfaces of a magnetic fluid under the action of a magnetic field is proposed and applied to determine shapes of a linear magnetizable ferrofluid drop in a uniform magnetic field. Hysteresis phenomena for the drop deformation and the drop shapes with ends, close to conical, were observed numericall

Feeding live prey to zoo animals: response of zoo visitors in Switzerland

In summer 2007, with the help of a written questionnaire, the attitudes of more than 400 visitors to the zoological garden of Zurich, Switzerland, toward the idea of feeding live insects to lizards, live fish to otters, and live rabbits to tigers were investigated. The majority of Swiss zoo visitors agreed with the idea of feeding live prey (invertebrates and vertebrates) to zoo animals, both off- and on-exhibit, except in the case of feeding live rabbits to tigers on-exhibit. Women and frequent visitors of the zoo disagreed more often with the on-exhibit feeding of live rabbits to tigers. Study participants with a higher level of education were more likely to agree with the idea of feeding live invertebrates and vertebrates to zoo animals off-exhibit. In comparison to an earlier study undertaken in Scotland, zoo visitors in Switzerland were more often in favor of the live feeding of vertebrates. Feeding live prey can counter the loss of hunting skills of carnivores and improve the animals’ well-being. However, feeding enrichments have to strike a balance between optimal living conditions of animals and the quality of visitor experience. Our results show that such a balance can be found, especially when live feeding of mammals is carried out off-exhibit. A good interpretation of food enrichment might help zoos to win more support for the issue, and for re-introduction programs and conservation