15,299 research outputs found
Statistical Modelling of Information Sharing: Community, Membership and Content
File-sharing systems, like many online and traditional information sharing
communities (e.g. newsgroups, BBS, forums, interest clubs), are dynamical
systems in nature. As peers get in and out of the system, the information
content made available by the prevailing membership varies continually in
amount as well as composition, which in turn affects all peers' join/leave
decisions. As a result, the dynamics of membership and information content are
strongly coupled, suggesting interesting issues about growth, sustenance and
stability.
In this paper, we propose to study such communities with a simple statistical
model of an information sharing club. Carrying their private payloads of
information goods as potential supply to the club, peers join or leave on the
basis of whether the information they demand is currently available.
Information goods are chunked and typed, as in a file sharing system where
peers contribute different files, or a forum where messages are grouped by
topics or threads. Peers' demand and supply are then characterized by
statistical distributions over the type domain.
This model reveals interesting critical behaviour with multiple equilibria. A
sharp growth threshold is derived: the club may grow towards a sustainable
equilibrium only if the value of an order parameter is above the threshold, or
shrink to emptiness otherwise. The order parameter is composite and comprises
the peer population size, the level of their contributed supply, the club's
efficiency in information search, the spread of supply and demand over the type
domain, as well as the goodness of match between them.Comment: accepted in International Symposium on Computer Performance,
Modeling, Measurements and Evaluation, Juan-les-Pins, France, October-200
Ceramic automotive Stirling engine study
A conceptual design study for a Ceramic Automotive Stirling Engine (CASE) is performed. Year 1990 structural ceramic technology is assumed. Structural and performance analyses of the conceptual design are performed as well as a manufacturing and cost analysis. The general conclusions from this study are that such an engine would be 10-26% more efficient over its performance map than the current metal Automotive Stirling Reference Engine (ASRE). Cost of such a ceramic engine is likely to be somewhat higher than that of the ASRE but engine cost is very sensitive to the ultimate cost of the high purity, ceramic powder raw materials required to fabricate high performance parts. When the design study is projected to the year 2000 technology, substantinal net efficiency improvements, on the order of 25 to 46% over the ASRE, are computed
Analysis Tools for Discovering Strong Parity Violation at Hadron Colliders
Several arguments suggest parity violation may be observable in high energy
strong interactions. We introduce new analysis tools for describing the
azimuthal dependence of multi-particle distributions, or "azimuthal flow."
Analysis uses the representations of the orthogonal group O(2) and dihedral
groups necessary to define parity correctly in two dimensions.
Classification finds that collective angles used in event-by-event statistics
represent inequivalent tensor observables that cannot generally be represented
by a single "reaction plane". Many new parity-violating observables exist that
have never been measured, while many new parity-conserving observables formerly
lumped together are now distinguished. We use the concept of "event shape
sorting" to suggest separating right- and left-handed events, and we discuss
the effects of transverse and longitudinal spin. The analysis tools are
statistically robust, and can be applied equally to low or high multiplicity
events at the Tevatron, or , and the .Comment: 18 pages, 2 figures. Final version, accepted for publication in PRD.
Updated references. Modified presentation and discussion of previous wor
Draft Genome Sequence of Mycobacterium arupense Strain GUC1.
We report the draft genome sequence of Mycobacterium arupense strain GUC1 from a sputum sample of a patient with bronchiectasis. This is the first draft genome sequence of Mycobacterium arupense, a rapidly growing nonchromogenic mycobacteria
Draft Genome Sequence of Mycobacterium elephantis Strain Lipa.
We report the draft genome sequence of Mycobacterium elephantis strain Lipa from a sputum sample of a patient with pulmonary disease. This is the first draft genome sequence of M. elephantis, a rapidly growing mycobacterium
Draft Genome Sequence of Mycobacterium obuense Strain UC1, Isolated from Patient Sputum.
We report the draft genome sequence of Mycobacterium obuense strain UC1 from a patient sputum sample. This is the first draft genome sequence of Mycobacterium obuense, a rapidly growing scotochromogenic mycobacterium
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