Multi-scale evolution of a derecho-producing MCS

September 10, 1997.Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1997.Includes bibliographical references.In this dissertation we address one type of severe weather: strong straight-line winds. In particular, we focus on derechos, a type of wind storm caused by a convective system and characterized by its long duration and by the large area it covers. One interesting characteristic of these storms is that they develop at night, on the cold side of a thermal boundary. This region is not characterized by large convective instability. In fact, surface parcels are generally stable with respect to vertical displacements. To gain understanding of the physical processes involved in these storms, we focused on the case of a MCS that developed in eastern Colorado on 12-13 May, 1985. The system formed in the afternoon, was active until early morning, and caused strong winds during the night. A multi-scale full physics simulation of this case was performed using a non-hydrostatic mesoscale model. Four telescopically nested grids covering from the synoptic scale down to cloud scale circulations were used. A Lagrangian model was used to follow trajectories of parcels that took part in the updraft and in the downdraft, and balance of forces were computed along the trajectories. Our results show that the synoptic and mesoscale environment of the storm largely influences convective organization and cloud-scale circulations. During the day, when the boundary layer is well mixed, the source of air for the clouds is located within the boundary layer. A night, when the boundary layer becomes stable, the source of air shifts to the top of the boundary layer. It is composed of warm, moist air that is brought by the nocturnal low-level jet. The downdraft structure also changes from day to night. During the day, parcels acquire negative buoyancy because of cooling due to evaporation and melting. As they sink, they remain colder than the environment, and end up at the surface constituting the cold pool. During the night, downdrafts are stronger, generating the strong surface winds. The most important branch of the downdraft has an "up-down" trajectory. Parcels start close to the ground, are lifted up by a strong pressure gradient force, and become colder than their surroundings as they ascend in a stable environment. Then, as they go through the precipitation shaft, they sink due to negative buoyancy enhanced by condensate loading. The upward pressure gradient force is partially related to mid-level rotation in the storm, which has characteristics of a high-precipitation supercell.Sponsored by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil National Science Foundation un grant ATM-9420045

An Eye Gaze Model for Controlling the Display of Social Status in Believable Virtual Humans

Abstract—Designing highly believable characters remains a major concern within digital games. Matching a chosen personality and other dramatic qualities to displayed behavior is an important part of improving overall believability. Gaze is a critical component of social exchanges and serves to make characters engaging or aloof, as well as to establish character’s role in a conversation. In this paper, we investigate the communication of status related social signals by means of a virtual human’s eye gaze. We constructed a cross-domain verbal-conceptual computational model of gaze for virtual humans to facilitate the display of social status. We describe the validation of the model’s parameters, including the length of eye contact and gazes, movement velocity, equilibrium response, and head and body posture. In a first set of studies, conducted on Amazon Mechanical Turk using prerecorded video clips of animated characters, we found statistically significant differences in how the characters’ status was rated based on the variation in social status. In a second step based on these empirical findings, we designed an interactive system that incorporates dynamic eye tracking and spoken dialog, along with real-time control of a virtual character. We evaluated the model using a presential, interactive scenario of a simulated hiring interview. Corroborating our previous finding, the interactive study yielded significant differences in perception of status were found (p = .046). Thus, we believe status is an important aspect of dramatic believability, and accordingly, this paper presents our social eye gaze model for realistic procedurally animated characters and shows its efficacy. Index Terms—procedural animation, believable characters, virtual human, gaze, social interaction, nonverbal behaviour, video game

Simulink toolbox for real-time virtual character control

Building virtual humans is a task of formidable complexity. We believe that, especially when building agents that interact with biological humans in real-time over multiple sensorial channels, graphical, data flow oriented programming environments are the development tool of choice. In this paper, we describe a toolbox for the system control and block diagramming environment Simulink that supports the construction of virtual humans. Available blocks include sources for stochastic processes, utilities for coordinate transformation and messaging, as well as modules for controlling gaze and facial expressions

An Architecture for Personality-based, Nonverbal Behavior in Affective Virtual Humanoid Character

As humans we perceive other humans as individually different based – amongst other things – on a consistent pattern of affect, cognition, and behavior. Here we propose a biologically and psychologically grounded cognitive architecture for the control of nonverbal behavior of a virtual humanoid character during dynamic interactions with human users. Key aspects of the internal states and overt behavior of the virtual character are modulated by high-level personality parameters derived from the scientific literature. The virtual character should behave naturally and consistently while responding dynamically to the environment's feedback. Our architecture strives to yield consistent patterns of behavior though personality traits that have a modulatory influence at different levels of the hierarchy. These factors affect on the one hand high-level components such as ‘emotional reactions’ and ‘coping behavior’, and on the other hand low-level parameters such as the ‘speed of movements and repetition of gestures. Psychological data models are used as a reference to create a map between personality factors and patterns of behavior. We present a novel hybrid computational model that combines the control of discrete behavior of the virtual character moving through states of the interaction with continuous updates of the emotional state of the virtual character depending on feedback from interactions with the environment. To develop and evaluate the hybrid model, a testing scenario is proposed that is based on a turn-taking interaction between a human participant and a 3D representation of the humanoid character. We believe that our work contributes to individualized, and ultimately more believable humanoid artifacts that can be deploy in a wide range of application scenarios

The spinorial ball: a macroscopic object of spin-1/2

Historically, the observation of half-spin particles was one of the most surprising features of quantum mechanics. They are often described as "objects that do not come back to their initial state after one turn but do after two turns". There are macroscopic implementations using constraints such as clamping a belt or ribbon that purport to show similar behavior (the "Dirac belt trick"). However, a demonstration of an unconstrained macroscopic object with half-spin behavior remains elusive. In this article, we propose to fill this gap and introduce the spinorial ball. It consists of a translucent plastic ball with internal LED illumination that behaves as a freely movable macroscopic half-spin object. It provides a new tool to introduce and visualize half-integer spins as well as the covering group homomorphism from SU(2) to SO(3), and offers in particular a clear visualization of the different homotopy classes of SO(3). We discuss its development and function, and how one can mimic quantum measurement and wave function collapse using this the spinorial ball. The entire system is open source hardware, with build details, models, 3d printing files, etc., provided under an open source license

An Interactive Space as a Creature:Mechanisms of Agency Attribution and Autotelic Experience

Interacting with an animal is a highly immersing and satisfactory experience. How can interaction with an artifact can be imbued with the quality of an interaction with a living being? The authors propose a theoretical relationship that puts the predictability of the human-artifact interaction at the center of the attribution of agency and experience of “flow.” They empirically explored three modes of interaction that differed in the level of predictability of the interactive space's behavior. The results of the authors' study give support to the notion that there is a sweet spot of predictability in the reactions of the space that leads users to perceive the space as a creature. Flow factors discriminated between the different modes of interaction and showed the expected nonlinear relationship with the predictability of the interaction. The authors' results show that predictability is a key factor to induce an attribution of agency, and they hope that their study can contribute to a more systematic approach to designing satisfactory and rich interaction between humans and machines

Towards accessible mental healthcare through augmented reality and self-assessment tools

Mental health presents a growing public health concern worldwide with mental illnesses affecting people's quality of life and causing an economic impact on societies. The rapidly increasing demand for mental healthcare is calling for new ways of disseminating mental health knowledge and for supporting people with mental health illnesses. As an alternative to traditional mental health therapies and treatments, mental health self-assessment and self-management tools become widely available to the public. While such tools can potentially offer more timely personalised support, individuals seeking help are faced with the challenge of making an appropriate choice from an exhaustive number of online tools, mobile apps, and support programs. In this article, we present myGRaCE-a self-assessment and self-management mental health tool made accessible to users via Augmented Reality technologies. The advantage of the system is that it provides a direct pathway to relevant and reliable mental health resources and offers a positive incentive and interventions for at-risk users. To investigate the usability and intuitiveness of the system, we conducted a pilot evaluation study with 10 participants. The results showed that the majority of study participants found the system intuitive and easy to use

Microdisplacements induced by a local perturbation inside a granular packing

International audienceThe microdisplacements generated by a small localized overload at the free surface are visualized experimentally inside a packing of steel beads. For a triangular packing, beads rearrangements remain confined in two inverted triangles on both sides of the applied overload. This pattern disappears for stronger disorder. A simple model allows us to account for these observations and to relate them to the stress function response measured via photoelastic visualizations. This provides a different tool to probe the mechanical Green's function in weakly confined packings of rigid grains the description of which is the most challenged