Characterizing peers communities and dynamics in a P2P live streaming system

Despite the large number of works devoted to understand P2P live streaming applications, most of them put forth so far rely on characterizing the static view of these systems. In this work, we characterize the SopCast, one of the most important P2P live streaming applications. We focus on its dynamics behavior as well as on the community formation phenomena. Our results show that SopCast presents a low overlay topology diameter and low end-to-end shortest path. In fact, diameter is smaller than 6 hops in almost 90 % of the observation time. More than 96 % of peers’ end-to-end connections present only 3 hops. These values combined may lead to low latencies and a fast streaming diffusion. Second, we show that communities in SopCast are well defined by the streaming data exchange process. Moreover, the SopCast protocol does not group peers according to their Autonomous System. In fact, the probability that a community contains 50 % of its members belonging to the same AS (when we observe the largest AS of our experiments) is lower then 10 %. Peers exchange more data with partners belonging to the same community instead of peers inside the same AS. For the largest AS we have, less than 18 % of peer traffic has been exchanged with another AS partners. Finally, our analysis provides important information to support the future design of more efficient P2P live streaming systems and new protocols that exploit communities’ relationships.     

Using Courseware Discussion Boards to Engage Graduate Students in Online Library Workshops

ABSTRACT

Librarians at Oregon State University (OSU) Libraries used the discussion board features of Blackboard courseware to create an interactive experience for graduate students at a distance who could not attend the on-campus “Literature Review Workshops.” These recently developed workshops have been extremely popular with graduate students across the disciplines and have generated a growing demand from distance education graduate students and faculty to offer similar information online. Reluctant to simply deliver content via an online tutorial, librarians sought to duplicate the workshop atmosphere by making the sessions available for a short time-period online, asking participants to respond to discussion questions at specific points in the workshop, and offering audio-mediated online demonstrations of tools and resources. Student feedback and follow-up requests for more workshops support the perception that this approach offered a rewarding learning experience that addressed their specific adult learning needs.     

Line patterning of graphite and the fabrication of cheap, inexpensive, “throw-away” sensors

A new simple method (“line patterning technique”) using only standard office equipment is described whereby clearly defined, electrically conducting patterns of graphite can be deposited on polymer (plastic) or paper substrates. The properties of the conductive patterns have been characterized by electrical conductivity and SEM measurements. Sensors were constructed by using interdigitated patterns of graphite deposited on plastic and paper, and coated with a thin film of conducting electronic polymer, e.g. polyaniline emeraldine salt.     

New approach for optimizing the interpretation and representation of the degree of historical-archaeological evidence in the virtual reconstructions

Virtual Reality - Virtual reconstruction is defined as the visual recovery of a building or object through the creation of a three-dimensional model of the asset to be reconstructed, in a...     

Floral nectar phenolics as biochemical markers for the botanical origin of heather honey

In order to find out biochemical markers for the botanical origin of heather (Erica) honey, the phenolic metabolites present in heather floral nectar, collected from the honey-stomach of bees gathering nectar from these flowers, were analysed. The flavonoid fraction of nectar contained four main flavonoids. Two of them were quercetin and kaempferol 3-rhamnosides, and the other two were tentatively identified as myricetin 3-methyl ether and isorhamnetin 3-rhamnosides. Since the natural glycosides are hydrolysed by bee enzymes to render the corresponding aglycones, which are the metabolites detected in honey, acid hydrolysis of the nectar glycosides was achieved. The aglycones quercetin, myricetin 3-methyl ether, kaempferol and isorhamnetin were identified, as well as the gallic acid derivative ellagic acid. The analysis of Portuguese heather honey samples showed that ellagic acid was present in all the samples in significant amounts ranging between 100 g and 600 g per 100 g honey. The other nectar-derived flavonoids were also present, although some of them in very variable amounts. Ellagic acid and myricetin 3-methyl ether, which have not been detected in any of the monofloral honey samples investigated so far, with the only exception being a French honey sample of the botanically relatedCalluna (Ericaceae) which also contained ellagic acid, seem to be the most useful potential markers for the floral origin of heather honey. However, more detailed and extensive investigations are needed to prove the utility of these markers.     

Simple procedures of choice in multicriteria problems without precise information about the alternatives’ values

The additive model of multiattribute value theory is widely used in multicriteria choice problems. But often it is not easy to obtain precise values for the scaling weights or the alternatives’ value in each function. Several decision rules which require weaker information, such as ordinal information, have been proposed to select an alternative under these circumstances. We propose new decision rules and test them using Monte-Carlo simulation, considering that there is ordinal information both on the scaling weights and on the alternatives’ values. Results show the new rules constitute a good approximation. We provide guidelines about how to use these rules in a context of selecting a subset of the most promising alternatives, considering the contradictory objectives of keeping a low number of alternatives yet not excluding the best one.     

Time-relevant stability of 2D systems

For many 2D systems, one of the independent variables plays a distinct role in the evolution of the trajectories; since often this special independent variable is time, we call such systems ‘time-relevant’. In this paper, we introduce a stability notion for time-relevant systems described by higher-order difference equations. We give algebraic tests in terms of the location of the zeros of the determinant of a polynomial matrix describing the system. We also give an LMI characterization of time-relevant stability involving only constant matrices.