How Push-To-Talk Makes Talk Less Pushy

This paper presents an exploratory study of college-age students using two-way, push-to-talk cellular radios. We describe the observed and reported use of cellular radio by the participants. We discuss how the half-duplex, lightweight cellular radio communication was associated with reduced interactional commitment, which meant the cellular radios could be used for a wide range of conversation styles. One such style, intermittent conversation, is characterized by response delays. Intermittent conversation is surprising in an audio medium, since it is typically associated with textual media such as instant messaging. We present design implications of our findings.Comment: 10 page

Making Space for Stories: Ambiguity in the Design of Personal Communication Systems

Pervasive personal communication technologies offer the potential for important social benefits for individual users, but also the potential for significant social difficulties and costs. In research on face-to-face social interaction, ambiguity is often identified as an important resource for resolving social difficulties. In this paper, we discuss two design cases of personal communication systems, one based on fieldwork of a commercial system and another based on an unrealized design concept. The cases illustrate how user behavior concerning a particular social difficulty, unexplained unresponsiveness, can be influenced by technological issues that result in interactional ambiguity. The cases also highlight the need to balance the utility of ambiguity against the utility of usability and communicative clarity.Comment: 10 page

Scalability Analysis of Parallel GMRES Implementations

Applications involving large sparse nonsymmetric linear systems encourage parallel implementations of robust iterative solution methods, such as GMRES(k). Two parallel versions of GMRES(k) based on different data distributions and using Householder reflections in the orthogonalization phase, and variations of these which adapt the restart value k, are analyzed with respect to scalability (their ability to maintain fixed efficiency with an increase in problem size and number of processors).A theoretical algorithm-machine model for scalability is derived and validated by experiments on three parallel computers, each with different machine characteristics

High-Speed Projects in the United States: Identifying the Elements for Success-Part 1, MTI Report 05-01

For almost half a century, high-speed ground transportation (HSGT) has held the promise of fast, convenient, and environmentally sound travel for distances between 40 and 600 miles. While a number of HSGT systems have been developed and deployed in Asia and Europe, none has come close to being implemented in the United States. Yet this is not for lack of trying. There have been several efforts around the country, most of which have failed, some of which are still in the early stages, and a few of which might come to pass. The goal of this study was to identify lessons learned for successfully developing and implementing high-speed rail (HSR) in the United States. Through a broad literature review, interviews, and three specific case studies—Florida, California, and the Pacific Northwest—this study articulates those lessons and presents themes for future consideration