Academic literature on the topic 'LD5655.V851 1995.S539'

Humans and other animals typically consume less of novel foods than of familiar ones, a phenomenon termed ingestional neophobia. Young children display especially high levels of neophobia, spitting out new foods but accepting those same foods after familiarization. Rejection of novel foods presumably reflects the aversiveness of the food's novel sensory cues, which thereby occasions withdrawal. Familiar foods typically evoke acceptance, suggesting that familiar foods are not categorically aversive. According to a biphasic model of emotion, negative affective behaviors (e.g., withdrawal) are enhanced during negative emotional states and inhibited during positive states. Positive affective behaviors (e.g., approach, consumption) are enhanced during positive emotional states but inhibited during negative states. If neophobia (withdrawal) and food acceptance (approach) reflect negative and positive affective behaviors respectively, according to the biphasic model, emotional state at the moment of food presentation should mediate the display of neophobia and food acceptance. To induce mood, preschool children were asked to think of things that make them happy (positive), sad (negative) or asked to count (neutral). Following mood-induction (MI), children received a familiar- or novel-appearing food. Acceptance was assessed as latency to touch the food, latency to Bite 1, latency to Bites 2-5, amount eaten, rate of eating, and degree of food contact. Acceptance was expected to be greater for the familiar- than for the novel-appearing food, and greater in the positive MI than in the neutral MI than in the negative MI condition. An interaction between food appearance and MI condition was expected. Results indicated that children who received a novel-appearing food ate reliably less and reliably slower than children who received the same food in its familiar appearance. There were no effects of MI condition. However manipulation checks indicated that MI procedures were ineffective. Participants were therefore reassigned to mood groups based on ratings of expressed affect. Analysis of reassigned groups indicated that the negative mood group took significantly longer to touch the food, to Bite 1, and to Bites 2-5 than did neutral and positive groups. The negative mood group ate reliably less than the neutral group, who ate reliably less than the positive group.<br>Ph. D.

A method for coordinating a homogeneous swarm of autonomous mobile robots is presented. The broadcast-based coordination scheme was developed for the Army Ant swarm—a system of small, relatively inexpensive mobile robots that can accomplish complex tasks by cooperating as a team. The primary drawback of the Army Ant system is that the absence of a central supervisor poses difficulty in the coordination and control of the agents. Our coordination scheme provides a global "group dynamic" that controls the actions of each robot using only local interactions. Coordination of the swarm is achieved with signals we call "heartbeats". Each agent broadcasts a unique heartbeat and responds to the collective behavior of all other heartbeats. We generate heartbeats with van der Pol oscillators, which are nonlinear oscillators that modify their output when coupled to other oscillators. Van der Pol oscillators have long been utilized in simulations, particularly to model rhythmic behavior in biological systems. In this application, we use the known properties of coupled van der Pol oscillators to create predictable group behavior. We emphasize the use of this controller to allow agents to simultaneously perform an action such as lifting, steering, or changing speed. For this research we synthesize a three oscillator network to show that we can achieve multi-agent coordination. An inexpensive FM communication link is used to broadcast and receive oscillator signals. We show that the network may be configured to entrain to a leader or to a common frequency. Additionally, we use our coordination scheme to provide global speed control to our three agent system.<br>Master of Science

Zinc gallate and Mn2+ -activated zinc gallate were identified as potential low-voltage cathodoluminescent phosphors for use in vacuum fluorescent displays. The stability of these oxide phosphors in high-vacuum and absence of corrosive gas emission under electron bombardment, offer advantages over commonly used sulfide phosphors. A low-voltage cathodoluminescence spectrophotometer was _ developed for phosphor characterization. Sample brightness was measured as a function of anode voltage (10-300 VDC). The effects of activator concentration, phosphor layer thickness, deposition process, and internal pressure were examined. From photoluminescence measurements, absorption and emission centers were identified, the role of composition in the luminescence process explained, and host-to-activator, non-radiative energy transfer identified for ZnGa204:Mn2+. Samples of the general composition Znl_xMnxGa204, with x ranging from 0 to 0.03, were synthesized by solid-state reaction techniques using oxide precursors fired in air, followed by reduction firing in 98%N2, 2%H2. The phase-pure ZnGa204 spinel structure of all the compositions was characterized by X-ray diffraction.<br>Master of Science