We introduce context-aware scalable authentication (CASA) as a way of balancing security and usability for authentication. Our core idea is to combine a number of passive factors for authentication (e.g., a user’s current location) with appropriate active factors. In this paper, we provide a probabilistic framework for dynamically selecting an active authentication scheme that satisfies a secur...

Clutter contamination is common in radar observations and is one of the major factors impacting quantitative applications. This can be particularly severe for ground based weather radar when observing the precipitation at low attitude and close range. Strong clutter can project observations with intense reflectivity as well as bias the Doppler moments. The NSF engineering research center of col...

Speech is typically perceived against a background of other sounds. Listeners are adept at extracting target sources from the acoustic mixture reaching the ears. The auditory scene analysis account holds that this feat is the result of a two stage process. In the first stage, sound is decomposed both within and across auditory nuclei. Subsequent processes of perceptual organisation are informed...

Results from the CASA-MIA cosmic ray experiment are presented. I discuss the apparatus and its performance, including new results on the identification of the shadows of the sun and moon used to determine the angular resolution. Limits on the emission of 100 TeV v-rays from the Crab Nebula are well below extrapolations from TeV observations. A search for diffuse "),-rays from the Galactic plane...

A project to detect the radio-frequency pulse associated with extensive air showers of cosmic rays is described briefly. Prototype work is being performed at the CASA/MIA array in Utah, with the intention of designing equipment that can be used in conjunction with the Auger Giant Array proposal.

1 In August 2003, while many Europeans were heading to the beaches to mitigate the effects of the worst heat wave on record, José Eduardo Sampaio, the CEO of Casa XXI, was faced with another kind of heat. Cartão 21, the innovative payment system of Casa XXI that he had personally conceived and subcontracted, had dramatically failed on August 6 th during the high-visibility inauguration of Alval...

Separating voiced speech from its mixtures with interferences in monaural condition is not only an important but also challenging task. As multipitch tracking can enable much better performance of speech separation for CASA systems, we propose a new multipitch determination algorithm, which can be used under various kinds of noise conditions. In the process of multipitch estimation, a new repre...

For the problem of separating sound mixtures, periodicity is a powerful cue used by both human listeners and automatic systems. Short-term autocorrelation of subband envelopes, as in the correlogram, accounts for much perceptual data. We present a discrete representation of common-period sounds, derived from the correlogram, for use in computational auditory scene analysis: The weft describes a...

An Hochschulen ist heute eine hochgradig heterogene IT-Landschaft mit Diensten und Web-Anwendungen etabliert. Durch die gewachsenen Strukturen an vielen Fakultäten und die häufig dezentral verwalteten Anwendungen ergibt sich für die Studierenden die Notwendigkeit, eine Vielzahl von Diensten zu kennen und regelmäßig aufzusuchen. Das in diesem Beitrag vorgestellte CASA-Konzept (Context-Aware Serv...

Techniques for separating speech from background noise and other sources of interference have important applications for robust speech recognition and speech enhancement. Many traditional computational auditory scene analysis (CASA) based approaches decompose the input mixture into a time-frequency (T-F) representation, and attempt to identify the T-F units where the target energy dominates tha...