Publications

Publications
Publications
We strongly believe in open source and giving to our community. We work directly with researchers in academia and seek out new perspectives with our intern and fellowship programs. We generalize our solutions and release them to the world as open source projects. We host discussions and publish our results.

Publications

April 14, 2000, Breckenridge, Colorado

Hierarchical Map Learning for Robot Navigation, AIPS Workshop on Decision-Theoretic Planning

Charles Sutton, Khashayar Rohanimanesh, Andrew McCallum, Charles Sutton, Khashayar Rohanimanesh, Andrew McCallum

No Information

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J. Math. Anal. Appl., 234, pp. 660-674. 1999

Classical solutions for diffusion-induced grain-boundary motion

Uwe Mayer, Gieri Simonett

We prove existence and uniqueness of classical solutions for the motion of hypersurfaces driven by mean curvature and diffusion of a solute along the surface. This free boundary problem involves solving a coupled system of fully nonlinear partial differential equations.

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Nonlinear Partial Differential Equations, Gui-Qiang Chen and Emmanuele DiBenedetto (editors), Amer. Math. Soc., Providence, RI, pp. 231-240, 1999

On diffusion-induced grain-boundary motion

Uwe Mayer, Gieri Simonett

We consider a sharp interface model which describes diffusion-induced grain-boundary motion in a poly-crystalline material. This model leads to a fully nonlinear coupled system of partial differential equations. We show existence and uniqueness of smooth solutions.

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Journal of Computer Mediated Communication, JCMC 4 (4), 1999

Distributed Research Teams: Meeting Asynchronously in Virtual Space

Lai Adams, Lori Toomey, Elizabeth Churchill
 
As computer networks improve, more social and work interactions are carried out “virtually” by geographically separated group members. In this paper we discuss the design of a tool, PAVE, to support remote work interactions among colleagues in different time zones.
 
PAVE extends a 2D graphical MOO and supports synchronous and asynchronous interactions.
 
PAVE logs and indexes activities in the space. This capture facility enables playback and augmentation of meeting interactions by non-collocated group members. Thus, members can participate asynchronously in meetings they could not attend in real time, not just review them.
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IEEE Transactions on Information Theory, vol. 45, no. 3, pp. 920-938, April 1999

Minimax emission computed tomography using high resolution anatomical side information and B-spline models

Alfred O. Hero III, Robinson Piramuthu, Jeffrey A. Fessler, Stephen R.Titus

In this paper a minimax methodology is presented for combining information from two imaging modalities having different intrinsic spatial resolutions. The focus application is emission computed tomography (ECT), a low-resolution modality for reconstruction of radionuclide tracer density, when supplemented by high-resolution anatomical boundary information extracted from a magnetic resonance image (MRI) of the same imaging volume.

The MRI boundary within the two-dimensional (2-D) slice of interest is parameterized by a closed planar curve. The Cramer–Rao (CR) lower bound is used to analyze estimation errors for different boundary shapes. Under a spatially inhomogeneous Gibbs field model for the tracer density a representation for the minimax MRI-enhanced tracer density estimator is obtained. It is shown that the estimator is asymptotically equivalent to a penalized maximum likelihood (PML) estimator with resolution selective Gibbs penalty.

Quantitative comparisons are presented using the iterative space alternating generalized expectation maximization (SAGE-EM) algorithm to implement the PML estimator with and without minimax weight averaging.

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Information Theory Workshop on Detection, Estimation, Classification and Imaging, February, 1999

Theoretical limits of parametric shape estimation in resolution-limited imaging

Robinson Piramuthu and A.O. Hero
AAAI 1999 Conference. 1999

Combining Collaborative Filtering with Personal Agents for Better Recommendations

Nathan Good, Ben Schafer, Joseph Konstan, Al Borchers, Badrul Sarwar, Jon Herlocker, John Riedl, Nathan Good, Ben Schafer, Joseph Konstan, Al Borchers, Badrul Sarwar, Jon Herlocker, John Riedl

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Keywords
Quarterly Journal of Experimental Psychology, 51A(1), 1-17, 1998

Selection through rejection: Reconsidering the invariant learning paradigm

Elizabeth Churchill, David Gilmore

Two experiments are reported that investigate the nature of selections in the McGeorge and Burton (1990) invariant learning paradigm. McGeorge and Burton suggest that subjects implicitly acquire abstract knowledge of an invariant feature (usually the presence of the digit “3”) in a set of 30 stimuli.

McGeorge and Burton's analysis has recently been challenged by Cock, Berry, and Gaffan (1994) and by Wright and Burton (1995). In this paper, we demonstrate that performance is based on knowledge of other aspects of the learning set besides the invariant digit, but that this knowledge is still implicit.

Altering the nature of the learning stimuli to highlight these co-varying features enhances the effects and increases the reporting of explicit knowledge. Our results indicate that performance within this paradigm is more easily characterized as rejection of salient negatives than selection of positive instances, but that salience is not based simply on similarity.

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Virtual Reality, Research Developments and Applications, Vol 3, 1-2., 1998

Editorial for Special Issue of Virtual Reality, Research Developments and Applications

Dave Snowdon, Elizabeth Churchill

No Information

Keywords
In Virtual Reality. Research Developments and Applications, Vol 3, 3-15, 1998

Collaborative Virtual Environments: an introductory review

Elizabeth Churchill, Dave Snowdon

A Collaborative Virtual Environment or CVE is a distributed, virtual reality that is designed to support collaborative activities. As such, CVEs provide a potentially infinite, graphically realised digital landscape within which multiple users can interact with each other and with simple or complex data representations.

CVEs are increasingly being used to support collaborative work between geographically separated and between collocated collaborators. CVEs vary in the sophistication of the data and embodiment representations employed and in the level of interactivity supported.

It is clear that systems which are intended to support collaborative activities should be designed with explicit consideration of the tasks to be achieved and the intended users' social and cognitive characteristics.

In this paper, we detail a number of existing systems and applications, but first discuss the nature of collaborative and cooperative work activities and consider the place of virtual reality systems in supporting such collaborative work. Following this, we discuss some future research directions.

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