7007390
Wrinkled flames and cellular patterns
We model flames and fire using the Navier-Stokes equations combined with the level set method and jump conditions to model the reaction front. Previous works modeled the flame using a combination of propagation in the normal direction and a curvature term which leads to a level set equation that is parabolic in nature and thus overly dissipative and smooth. Asymptotic theory shows that one can obtain more interesting velocities and fully hyperbolic (as opposed to parabolic) equations for the level set evolution. In particular, researchers in the field of detonation shock dynamics (DSD) have derived a set of equations which exhibit characteristic cellular patterns. We show how to make use of the DSD framework in the context of computer graphics simulations of flames and fire to obtain interesting features such as flame wrinkling and cellular patterns.
18405227
Controlling fluid animation with geometric potential
We propose a new fluid control technique that uses a geometrically induced potential field. Instead of optimizing the control forces exerted at each frame, as was done in previous work, a potential is added as an extra dimension to the simulation space which coerces the fluid inside this space to form the target shape. This type of shape control requires practically no additional computing by the Navier-Stokes solver at run-time, and adds little overhead to implementation. The confinement potentials are induced from geometric information given by animators, and so the control forces that take fluids to a lower potential can be decided in a preprocessing step. We show that a slightly generalized Navier-Stokes equation for fluids in potential fields can be simulated without changing the solver itself. A harmonic potential function can be quickly found with the Poisson solver which is already implemented as a part of the Navier-Stokes solver. 2 and 3 dimensional flows designed by common methods such as hand drawing, traditional shape modeling and key-framing, can be animated efficiently with our control technique. Copyright © 2004 John Wiley & Sons, Ltd.
6805196
Putting people in their place: an anonymous and privacy-sensitive approach to collecting sensed data in location-based applications
The emergence of location-based computing promises new and compelling applications, but raises very real privacy risks. Existing approaches to privacy generally treat people as the entity of interest, often using a fidelity tradeoff to manage the costs and benefits of revealing a person's location. However, these approaches cannot be applied in some applications, as a reduction in precision can render location information useless. This is true of a category of applications that use location data collected from multiple people to infer such information as whether there is a traffic jam on a bridge, whether there are seats available in a nearby coffee shop, when the next bus will arrive, or if a particular conference room is currently empty. We present hitchhiking, a new approach that treats locations as the primary entity of interest. Hitchhiking removes the fidelity tradeoff by preserving the anonymity of reports without reducing the precision of location disclosures. We can therefore support the full functionality of an interesting class of location-based applications without introducing the privacy concerns that would otherwise arise.
703960
Protecting people from phishing: the design and evaluation of an embedded training email system
Phishing attacks, in which criminals lure Internet users to websites that impersonate legitimate sites, are occurring with increasing frequency and are causing considerable harm to victims. In this paper we describe the design and evaluation of an embedded training email system that teaches people about phishing during their normal use of email. We conducted lab experiments contrasting the effectiveness of standard security notices about phishing with two embedded training designs we developed. We found that embedded training works better than the current practice of sending security notices. We also derived sound design principles for embedded training systems.
1292565
WebQuilt: a framework for capturing and visualizing the web experience
is a web logging and visualization system that helps web design teams run usability tests (both local and remote) and analyze the collected data. Logging is done through a proxy, overcoming many of the problems with server-side and client-side logging. Captured usage traces can be aggregated and visualized in a zooming interface that shows the web pages people viewed. The visualization also shows the most common paths taken through the website for a given task, as well as the optimal path for that task as designated by the designer. This paper discusses the architecture of WebQuilt and also describes how it can be extended for new kinds of analyses and visualizations.
907383
Designing for serendipity: supporting end-user configuration of ubiquitous computing environments
The future world of ubiquitous computing is one in which we will be surrounded by an ever-richer set of networked devices and services. In such a world, we cannot expect to have available to us specific applications that allow us to accomplish every conceivable combination of devices that we might wish. Instead, we believe that many of our interactions will be through highly generic tools that allow enduser discovery, configuration, interconnection, and control of the devices around us. This paper presents a design study of such an environment, intended to support serendipitous, opportunistic use of discovered network resources. We present an examination of a generic browser-style application built on top of an infrastructure developed to support arbitrary recombination of devices and services, as well as a number of challenges we believe to be inherent in such settings.
1564080
Privacy risk models for designing privacy-sensitive ubiquitous computing systems
Privacy is a difficult design issue that is becoming increasingly important as we push into ubiquitous computing environments. While there is a fair amount of theoretical work on designing for privacy, there are few practical methods for helping designers create applications that provide end-users with a reasonable level of privacy protection that is commensurate with the domain, with the community of users, and with the risks and benefits to all stakeholders in the intended system. Towards this end, we propose privacy risk models as a general method for refining privacy from an abstract concept into concrete issues for specific applications and prioritizing those issues. In this paper, we introduce a privacy risk model we have developed specifically for ubiquitous computing, and outline two case studies describing our use of this privacy risk model in the design of two ubiquitous computing applications.