University of Alberta

About: University of Alberta is a education organization based out in Edmonton, Alberta, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 65403 authors who have published 154847 publications receiving 5358338 citations. The organization is also known as: Ualberta & UAlberta.

Tail reconnection triggering substorm onset.

Abstract: Magnetospheric substorms explosively release solar wind energy previously stored in Earth's magnetotail, encompassing the entire magnetosphere and producing spectacular auroral displays. It has been unclear whether a substorm is triggered by a disruption of the electrical current flowing across the near-Earth magnetotail, at approximately 10 R(E) (R(E): Earth radius, or 6374 kilometers), or by the process of magnetic reconnection typically seen farther out in the magnetotail, at approximately 20 to 30 R(E). We report on simultaneous measurements in the magnetotail at multiple distances, at the time of substorm onset. Reconnection was observed at 20 R(E), at least 1.5 minutes before auroral intensification, at least 2 minutes before substorm expansion, and about 3 minutes before near-Earth current disruption. These results demonstrate that substorms are likely initiated by tail reconnection.

Regret Minimization in Games with Incomplete Information

Abstract: Extensive games are a powerful model of multiagent decision-making scenarios with incomplete information. Finding a Nash equilibrium for very large instances of these games has received a great deal of recent attention. In this paper, we describe a new technique for solving large games based on regret minimization. In particular, we introduce the notion of counterfactual regret, which exploits the degree of incomplete information in an extensive game. We show how minimizing counterfactual regret minimizes overall regret, and therefore in self-play can be used to compute a Nash equilibrium. We demonstrate this technique in the domain of poker, showing we can solve abstractions of limit Texas Hold'em with as many as 1012 states, two orders of magnitude larger than previous methods.

An Autoethnography on Learning About Autoethnography

Abstract: Autoethnography is an emerging qualitative research method that allows the author to write in a highly personalized style, drawing on his or her experience to extend understanding about a societal phenomenon. Autoethnography is grounded in postmodern philosophy and is linked to growing debate about reflexivity and voice in social research. The intent of autoethnography is to acknowledge the inextricable link between the personal and the cultural and to make room for nontraditional forms of inquiry and expression. In this autoethnography, the author explores the state of understanding regarding autoethnography as a research method and describes the experience of an emerging qualitative researcher in learning about this new and ideologically challenging genre of inquiry.

Partial encryption of compressed images and videos

Abstract: The increased popularity of multimedia applications places a great demand on efficient data storage and transmission techniques. Network communication, especially over a wireless network, can easily be intercepted and must be protected from eavesdroppers. Unfortunately, encryption and decryption are slow, and it is often difficult, if not impossible, to carry out real-time secure image and video communication and processing. Methods have been proposed to combine compression and encryption together to reduce the overall processing time, but they are either insecure or too computationally intensive. We propose a novel solution called partial encryption, in which a secure encryption algorithm is used to encrypt only part of the compressed data. Partial encryption is applied to several image and video compression algorithms in this paper. Only 13-27% of the output from quadtree compression algorithms is encrypted for typical images, and less than 2% is encrypted for 512/spl times/512 images compressed by the set partitioning in hierarchical trees (SPIHT) algorithm. The results are similar for video compression, resulting in a significant reduction in encryption and decryption time. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying compression algorithm.

Accent, intelligibility, and comprehensibility

Abstract: This study was designed to extend previous research on the relationships among intelligibility, perceived comprehensibility, and accentedness. Accent and comprehensibility ratings and transcriptions of accented speech from Cantonese, Japanese, Polish, and Spanish intermediate ESL students were obtained from 26 native English listeners. The listeners were also asked to identify the first language backgrounds of the same talkers and to provide information on their familiarity with the four accents used in this study. When the results of this study were compared with the Munro and Derwing (1995, Language Learning, 45, 73–97) study of learners of high proficiency, speaker proficiency level did not appear to affect the quasi-independent relationships among intelligibility, perceived comprehensibility, and accentedness; however, the relative contributions of grammatical and phonemic errors and goodness of prosody differed somewhat. Ability to identify the speakers' first languages was influenced by familiarity.