Ryan Schubert

Nanoparticle Diffusion Measures Bulk Clot Permeability

A clots function is to achieve hemostasis by resisting fluid flow. Permeability is the measurement of a clots hemostatic potential. It is sensitive to a wide range of biochemical parameters and pathologies. In this work, we consider the hydrodynamic phenomenon that reduces the mobility of fluid near the fiber surfaces. This no-slip boundary condition both defines the gels permeability and suppresses nanoparticle diffusion in gel interstices. Here we report that, unlike previous work where steric effects also hindered diffusion, our system-nanoparticles in fibrin gel-was subject exclusively to hydrodynamic diffusion suppression. This result enabled an automated, high-throughput permeability assay that used small clot volumes. Permeability was derived from nanoparticle diffusion using the effective medium theory, and showed one-to-one correlation with measured permeability. This technique measured permeability without quantifying gel structure, and may therefore prove useful for characterizing similar materials (e.g., extracellular matrix) where structure is uncontrolled during polymerization and difficult to measure subsequently. We also report that PEGylation reduced, but did not eliminate, the population of immobile particles. We studied the forces required to pull stuck PEG particles free to confirm that the attachment is a result of neither covalent nor strong electrostatic binding, and discuss the relevance of this force scale to particle transport through physiological clots.

A general approach for closed-loop registration in AR

The typical registration process in augmented reality (AR) consists of three independent consecutive stages: static calibration, dynamic tracking, and graphics overlay. The result is that the real-virtual registration is “open loop”-inaccurate calibration or tracking leads to misregistration that is seen by the users but not the system. To cope with this, we propose a general approach to “close the loop” in the displayed appearance by using the visual feedback of registration for pose tracking to achieve accurate registration. Specifically, a model-based method is introduced to simultaneously track and augment real objects in a closed-loop fashion, where the model is comprised of the combination of the real object to be tracked and the virtual object to be rendered. This method is applicable to paradigms including video-based AR, projector-based AR, and diminished reality. Both qualitative and quantitative experiments are presented to demonstrate the feasibility and effectiveness of our approach.

The wobbly table: Increased social presence via subtle incidental movement of a real-virtual table

While performing everyday interactions, we often incidentally touch and move objects in subtle ways. These objects are not necessarily directly related to the task at hand, and the movement of an object might even be entirely unintentional. If another person is touching the object at the same time, the movement can transfer through the object and be experienced - however subtly - by the other person. For example, when one person hands a drink to another, at some point both individuals will be touching the glass, and consequently exerting small (often unnoticed) forces on the other person. Despite the frequency of such subtle incidental movements of shared objects in everyday interactions, few have examined how these movements affect human-virtual human (VH) interaction. We ran an experiment to assess how presence and social presence are affected when a person experiences subtle, incidental movement through a shared real-virtual object. We constructed a real-virtual room with a table that spanned the boundary between the real and virtual environments. The participant was seated on the real side of the table, which visually extended into the virtual world via a projection screen, and the VH was seated on the virtual side of the table. The two interacted by playing a game of “Twenty Questions,” where one player asked the other a series of 20 yes/no questions to deduce what object the other player was thinking about. During the game, the “wobbly” group of subjects experienced subtle incidental movements of the real-virtual table: the entire real-virtual table tilted slightly away/toward the subject when the virtual/real human leaned on it. The control group also played the same game, except the table did not wobble. Results indicate that the wobbly group had higher presence and social presence with the virtual human in general, with statistically significant increases in presence, co-presence, and attentional allocation. We present the experiment and results, and discuss some potential implications for virtual human systems and some potential future studies.

Can social presence be contagious? Effects of social presence priming on interaction with Virtual Humans

This paper explores whether witnessing a Virtual Human (VH) in what appears to be a socially engaging discussion with another virtual human confederate/accomplice (VHC) can prime a person to feel and behave more socially engaged with the VH in a subsequent interaction. To explore this social priming phenomenon, we conducted an experiment in which participants in a control group had no priming while those in an experimental group were briefly exposed to an engaging social interaction between a VH and a nearby VHC. The participants primed by exposure to the brief VHC-VH interaction reported being significantly more excited and alert, perceiving the VH closer, and showed significantly higher measures of Co-Presence, Attentional Allocation, and Message Understanding dimensions of social presence towards the VH, compared to those who were not primed.

Exploring social presence transfer in real-virtual human interaction

We explore whether a peripheral observation of apparent mutual social presence between a real human (RH) and a virtual human (VH) can in turn increase a subjects sense of social presence with the VH. In other words, we explore whether social presence can “transfer” from one RH-VH interaction to another. Specifically, we carried out an experiment where human subjects were asked to play a game with a VH. As they entered the game room, approximately half of the subjects were exposed to a brief but apparently engaging conversation between an RH and the VH. The subjects who were exposed to the brief RH-VH interaction had significantly higher measures of both emotional connection and the attentional allocation dimension of social presence for the VH, compared to those who were not. We describe the motivation, the experiment, and the results.

Advances in Shader Lamps Avatars for telepresence

Since the introduction of the animatronic Shader Lamps Avatar in 2009, several aspects of the systems design have been improved to create a more effective telepresence experience. This includes an analysis of the tradeoffs between front and rear projection and bethardware deviceween rigidly aligning the projector with the display surface or needing to track it. A new control mode is implemented for the pan-tilt unit that enables the avatar head pose to better emulate real human motion and a new hardware device allows the motorized wheelchair that carries the avatar to be controlled by the remote inhabiter. With the recognition of the importance of high quality audio, the audio components for both the inhabiter and the avatar have also been updated. Finally, some preliminary live tests are presented and areas of continued research are discussed.

Effects of Social Priming on Social Presence with Intelligent Virtual Agents

This paper explores whether witnessing an Intelligent Virtual Agent (IVA) in what appears to be a socially engaging discussion with a Confederate Virtual Agent (CVA) prior to a direct interaction, can prime a person to feel and behave more socially engaged with the IVA in a subsequent interaction. To explore this social priming phenomenon, we conducted an experiment in which participants in a control group had no priming while those in an experimental group were briefly exposed to an engaging social interaction between an IVA and a nearby CVA (i.e. a virtual actor). The participants primed by exposure to the brief CVA-IVA interaction reported being significantly more excited and alert, perceiving the IVA as more responsive, and showed significantly higher measures of Co-Presence, Attentional Allocation, and Message Understanding dimensions of social presence for the IVA, compared to those who were not primed.

A Large-Scale Study of Surrogate Physicality and Gesturing on Human–Surrogate Interactions in a Public Space

Technological human surrogates, including robotic and virtual humans, have been popularly used in various scenarios including training, education, and entertainment. Prior research has investigated the effects of the surrogate’s physicality and gesturing in human perceptions and social influence of the surrogate. However, those studies have been carried out in research laboratories, where the participants were aware it was an experiment, and the participant demographics are typically relatively narrow—e.g., college students. In this paper, we describe and share results from a large-scale exploratory user study involving 7685 people in a public space, where they were unaware of the experimental nature of the setting, to investigate the effects of surrogate physicality and gesturing on their behavior during human–surrogate interactions. We evaluate human behaviors using several variables, such as proactivity and reactivity, and proximity. We have identified several interesting phenomena that could lead to hypotheses developed as part of future hypothesis-based studies. Based on the measurements of the variables, we believe people are more likely to be engaged in a human–surrogate interaction when the surrogate is physically present, but movements and gesturing with its body parts have not shown the expected benefits for the interaction engagement. Regarding the demographics of the people in the study, we found higher overall engagement for females than males, and higher reactivity for younger than older people. We discuss implications for practitioners aiming to design a technological surrogate that will directly interact with real humans.

Exploring the Impact of Environmental Effects on Social Presence with a Virtual Human

We explore how and in what ways the surrounding environment can be an important factor in human perception during interactions with virtual humans. We also seek to leverage any such knowledge to increase the sense of Social/Co-Presence with virtual humans. We conducted a user study to explore the influence of environmental events on social interaction between real and virtual humans in a Mixed Reality setting. Specifically we tested two different treatments to see the effects on Social/Co-Presence: (i) enhanced physical-virtual connectivity/influence via a real fan blowing on virtual paper, and (ii) the virtual human’s corresponding awareness of the environmental factor as she looks at the fan and holds the fluttering paper. While a statistical analysis for the study did not support the positive effects of the two treatments, we have developed some new insights that could be useful for future studies involving virtual humans.

HuSIS: A Dedicated Space for Studying Human Interactions

To support the study of effective human-surrogate interaction techniques and modalities, the Office of Naval Research awarded an equipment grant to support the development of a Human-Surrogate Interaction Space (HuSIS) at the University of Central Florida in the Institute for Simulation & Training. The HuSIS consists of a dedicated physical space, structures, and components designed specifically for carrying out controlled studies related to human-surrogate interactions. This article describes the motivation, design, and realization of the HuSIS and the benefits of the common data-collection and analysis framework developed for HuSIS research.