628 research outputs found

    An appreciative inquiry into the transformative learning experiences of students in a family literacy project

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    Educational discourse has often struggled to genuinely move beyond deficit-based language. Even action research, a predominant model for teacher development, starts with the identification of a problem (Cardno 2003). It would appear that the vocabulary for a hope-filled discourse which captures the imagination and infiuences our future educational activity seems to have escaped us. Moreover, we seem bereft of educational contexts where the experience for students is holistic and transformative

    A contrasting look at self-organization in the Internet and next-generation communication networks

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    This article examines contrasting notions of self-organization in the Internet and next-generation communication networks, by reviewing in some detail recent evidence regarding several of the more popular attempts to explain prominent features of Internet structure and behavior as "emergent phenomena." In these examples, what might appear to the nonexpert as "emergent self-organization" in the Internet actually results from well conceived (albeit perhaps ad hoc) design, with explanations that are mathematically rigorous, in agreement with engineering reality, and fully consistent with network measurements. These examples serve as concrete starting points from which networking researchers can assess whether or not explanations involving self-organization are relevant or appropriate in the context of next-generation communication networks, while also highlighting the main differences between approaches to self-organization that are rooted in engineering design vs. those inspired by statistical physics

    Diversity of graphs with highly variable connectivity

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    A popular approach for describing the structure of many complex networks focuses on graph theoretic properties that characterize their large-scale connectivity. While it is generally recognized that such descriptions based on aggregate statistics do not uniquely characterize a particular graph and also that many such statistical features are interdependent, the relationship between competing descriptions is not entirely understood. This paper lends perspective on this problem by showing how the degree sequence and other constraints (e.g., connectedness, no self-loops or parallel edges) on a particular graph play a primary role in dictating many features, including its correlation structure. Building on recent work, we show how a simple structural metric characterizes key differences between graphs having the same degree sequence. More broadly, we show how the (often implicit) choice of a background set against which to measure graph features has serious implications for the interpretation and comparability of graph theoretic descriptions

    Contrasting Views of Complexity and Their Implications For Network-Centric Infrastructures

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    There exists a widely recognized need to better understand and manage complex “systems of systems,” ranging from biology, ecology, and medicine to network-centric technologies. This is motivating the search for universal laws of highly evolved systems and driving demand for new mathematics and methods that are consistent, integrative, and predictive. However, the theoretical frameworks available today are not merely fragmented but sometimes contradictory and incompatible. We argue that complexity arises in highly evolved biological and technological systems primarily to provide mechanisms to create robustness. However, this complexity itself can be a source of new fragility, leading to “robust yet fragile” tradeoffs in system design. We focus on the role of robustness and architecture in networked infrastructures, and we highlight recent advances in the theory of distributed control driven by network technologies. This view of complexity in highly organized technological and biological systems is fundamentally different from the dominant perspective in the mainstream sciences, which downplays function, constraints, and tradeoffs, and tends to minimize the role of organization and design

    The magnitude distribution of earthquakes near Southern California faults

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    We investigate seismicity near faults in the Southern California Earthquake Center Community Fault Model. We search for anomalously large events that might be signs of a characteristic earthquake distribution. We find that seismicity near major fault zones in Southern California is well modeled by a Gutenberg-Richter distribution, with no evidence of characteristic earthquakes within the resolution limits of the modern instrumental catalog. However, the b value of the locally observed magnitude distribution is found to depend on distance to the nearest mapped fault segment, which suggests that earthquakes nucleating near major faults are likely to have larger magnitudes relative to earthquakes nucleating far from major faults

    Correlation Between Computed Contact Parameters and Wear Patterns on a Retrieved UHMWPE Tibial Insert

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    Throughout the life of a total knee arthroplasty implant repeated loading causes wear on the contact surfaces. Attempts have been made in the past to predict locations of wear through computational modeling and physical testing. This study examines a method of using computer modeling techniques to describe the kinematics of an implant, and to use kinematic data in finding areas of contact and internal shear stress that correlate to observed wear damage. A retrieved cruciate-retaining knee implant was reverse engineered and analyzed in one cycle of simulated gait using multibody dynamics and aligned according to resulting kinematic data for finite element analysis. Results showed a correlation between the predicted areas of contact and internal shear stresses and the observed wear damage

    Connecting Carrier\u27s Liability for Loss or Damage to Shipments

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    Is a carrier liable for a shipment it did not receive? What is the situation when a carrier receives only part of the goods from the preceding carrier, or when it receives them all but in damaged condition? How is the carrier\u27s liability affected if the damage is latent or patent? Discussion of these questions will be limited to shipments in interstate commerce and in three basic areas: (1) carrier\u27s common law liability,1 (2) effect of federal enactments, and (3) establishment of a prima facie case

    Towards a Theory of Scale-Free Graphs: Definition, Properties, and Implications (Extended Version)

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    Although the ``scale-free'' literature is large and growing, it gives neither a precise definition of scale-free graphs nor rigorous proofs of many of their claimed properties. In fact, it is easily shown that the existing theory has many inherent contradictions and verifiably false claims. In this paper, we propose a new, mathematically precise, and structural definition of the extent to which a graph is scale-free, and prove a series of results that recover many of the claimed properties while suggesting the potential for a rich and interesting theory. With this definition, scale-free (or its opposite, scale-rich) is closely related to other structural graph properties such as various notions of self-similarity (or respectively, self-dissimilarity). Scale-free graphs are also shown to be the likely outcome of random construction processes, consistent with the heuristic definitions implicit in existing random graph approaches. Our approach clarifies much of the confusion surrounding the sensational qualitative claims in the scale-free literature, and offers rigorous and quantitative alternatives.Comment: 44 pages, 16 figures. The primary version is to appear in Internet Mathematics (2005

    Optimal vaccination in a stochastic epidemic model of two non-interacting populations

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    Developing robust, quantitative methods to optimize resource allocations in response to epidemics has the potential to save lives and minimize health care costs. In this paper, we develop and apply a computationally efficient algorithm that enables us to calculate the complete probability distribution for the final epidemic size in a stochastic Susceptible-Infected-Recovered (SIR) model. Based on these results, we determine the optimal allocations of a limited quantity of vaccine between two non-interacting populations. We compare the stochastic solution to results obtained for the traditional, deterministic SIR model. For intermediate quantities of vaccine, the deterministic model is a poor estimate of the optimal strategy for the more realistic, stochastic case.Comment: 21 pages, 7 figure
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