2,975 research outputs found
Mixed Data and Classification of Transit Stops
An analysis of the characteristics and behavior of individual bus stops can
reveal clusters of similar stops, which can be of use in making routing and
scheduling decisions, as well as determining what facilities to provide at each
stop. This paper provides an exploratory analysis, including several possible
clustering results, of a dataset provided by the Regional Transit Service of
Rochester, NY. The dataset describes ridership on public buses, recording the
time, location, and number of entering and exiting passengers each time a bus
stops. A description of the overall behavior of bus ridership is followed by a
stop-level analysis. We compare multiple measures of stop similarity, based on
location, route information, and ridership volume over time
Geometry and Topology of Escape II: Homotopic Lobe Dynamics
We continue our study of the fractal structure of escape-time plots for
chaotic maps. In the preceding paper, we showed that the escape-time plot
contains regular sequences of successive escape segments, called epistrophes,
which converge geometrically upon each endpoint of every escape segment. In the
present paper, we use topological techniques to: (1) show that there exists a
minimal required set of escape segments within the escape-time plot; (2)
develop an algorithm which computes this minimal set; (3) show that the minimal
set eventually displays a recursive structure governed by an ``Epistrophe Start
Rule'': a new epistrophe is spawned Delta = D+1 iterates after the segment to
which it converges, where D is the minimum delay time of the complex.Comment: 13 pages, 8 figures, to appear in Chaos, second of two paper
Stats 101 in P4: Towards In-Switch Anomaly Detection
Data plane programmability is greatly improving network monitoring. Most new proposals rely on controllers pulling information (e.g., sketches or packets) from the data plane. This architecture is not a good fit for tasks requiring high reactivity, such as failure recovery, attack mitigation, and so on. Focusing on these tasks, we argue for a different architecture, where the data plane autonomously detects anomalies and pushes alerts to the controller. As a first step, we demonstrate that statistical checks can be implemented in P4 by revisiting definition and online computation of statistical measures. We collect our techniques in a P4 library, and showcase how they enable in-switch anomaly detection
First Steps Toward Change in Teacher Preparation for Elementary Science
Unless introductory undergraduate science classes for prospective elementary teachers actively incorporate the philosophy of inquiry-based learning called for in K-l2 science education refom little will change in elementary science education. Thus, at James Madison University, we have developed a new integrated science core curriculum called Understanding our World [1]. This course sequence was not only designed to fulfill general education science requirements. but also to focus on content areas our students will need to know as teachers. The objectives of these courses are based on the National Science Education Standards and Virginia’s Science Standards of Learning, including earth and space science, chemistry, physics, life sciences, and environmental science [2,3]. As an integrated package, this course sequence addresses basic science content, calculation skills, the philosophy and history of science, the process of how science is done, the role of science in society, and applications of computers and technology in science. Keeping in mind that students tend to teach in the same way they were taught, Understanding our World core classes embrace the concepts associated with reform in elementary math and science
Geometry and Topology of Escape I: Epistrophes
We consider a dynamical system given by an area-preserving map on a
two-dimensional phase plane and consider a one-dimensional line of initial
conditions within this plane. We record the number of iterates it takes a
trajectory to escape from a bounded region of the plane as a function along the
line of initial conditions, forming an ``escape-time plot''. For a chaotic
system, this plot is in general not a smooth function, but rather has many
singularities at which the escape time is infinite; these singularities form a
complicated fractal set. In this article we prove the existence of regular
repeated sequences, called ``epistrophes'', which occur at all levels of
resolution within the escape-time plot. (The word ``epistrophe'' comes from
rhetoric and means ``a repeated ending following a variable beginning''.) The
epistrophes give the escape-time plot a certain self-similarity, called
``epistrophic'' self-similarity, which need not imply either strict or
asymptotic self-similarity.Comment: 15 pages, 9 figures, to appear in Chaos, first of two paper
RAI’s First Annual Postgraduate Conference
The Royal Anthropological Institute’s first annual one-day postgraduate conference was hosted by the Department of Anthropology at Durham University on 20 September 2011. In their opening remarks, Bob Simpson, and Stephen M Lyon referred to the RAI’s vision for this annual conference, where 30 postgraduate students from more than 17 universities and institutes presented their research. Stephen Lyon then introduced the use of the Anthropological Index Online in anthropological research. RAI’s Film Officer, Susanne Hammacher and Education and Communication Officer, Nafisa Fera introduced the range of RAI’s activities, inviting participants to take an active role. Both sessions showed how the RAI can help to increase the visibility of students’ research in the discipline. In an interactive session with journal editors (Stephen M. Lyon of History and Anthropology, Claudia Merli of Durham Anthropology Journal, and Simone Gritter and Ely Rosenblum of the online multimedia journal ART/E/FACT), students gained information about getting published in anthropological journals
Low-Latency Routing on Mesh-Like Backbones
Early in in the Internet's history, routing within a single provider's WAN centered on placing traffic on the shortest path. More recent traffic engineering efforts aim to reduce congestion and/or increase utilization within the status quo of greedy shortest-path first routing on a sparse topology. In this paper, we argue that this status quo of routing and topology is fundamentally at odds with placing traffic so as to minimize latency for users while avoiding congestion. We advocate instead provider backbone topologies that are more mesh-like, and hence better at providing multiple low-latency paths, and a routing system that directly considers latency minimization and congestion avoidance while dynamically placing traffic on multiple unequal-cost paths. We offer a research agenda for achieving this new low-latency approach to WAN topology design and routing
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