1,403 research outputs found

    Transport in heterogeneous porous media

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    We present a new algorithm for modelling single phase transport of a tracer in porous media which demonstrates that structure on all scales affects macroscopic transport behaviour. We marry the robustness of the continuous time random walk (CTRW) framework with the simplicity of a Monte Carlo approach to reservoir simulation. We simulate transport as a series of particles transitioning between nodes with probability (t).dt that a particle will first arrive at a nearest neighbor in a time t to t + dt. To this end we first determine the mixing rules and transition probability ADE(t) for transport governed by the advection-dispersion equation (ADE) (Rhodes and Blunt, 2006). We validate our algorithm by simulating advective transport in bond percolation clusters at the critical point. We compute the histogram of flow speeds using the velocities from the bonds on the backbone and find the multifractal spectrum for two-dimensional lattices with linear dimension L _ 2000 and in three dimensions for L _ 250. We demonstrate that in the limit of large systems all the negative moments of the velocity distribution become ill-defined. However, to model transport, the velocity histogram should be weighted by the flux to obtain a well-defined mean travel time. Finally, we use CTRWtheory to demonstrate that anomalous transport is observed whose characteristics can be related to the multifractal properties of the system. We next demonstrate a pore-to-reservoir simulation methodology which is consistent across all scales of interest. At the micron scale, we fit a truncated power law (t) for the distribution of particle transition times from pore to pore simulations. To do this we use our transport algorithm on a geologically representative network model of Berea sandstone and compare the results to the explicit modelling of advection and molecular diffusion by Bijeljic and Blunt (2006). We find that the results are similar. We then demonstrate the effect of increasing pore scale heterogeneity on the power law exponent (_) by stretching the distribution of throat radii in our network model. We show that by increasing the spread of velocities within the network we decrease _ making the transport more anomalous - in keeping with the consensus currently in the literature. This (t) is then used to calculate transport on the mm to cm scale. We can then move up to the metre/grid block scale by using the transit time distribution from the mm-cm simulation to model transport in an explicit, geologically representative model of heterogeneity found within a grid block of the reservoir. From these numerical experiments we determine the (t) appropriate for transport on grid block scale systems characterized by Peclet (Pe) number and the type of heterogeneity within the system. This allows us to account for small scale uncertainty by interpreting (t) probabilistically and running simulations for different possible realizations of the reservoir heterogeneity. At the field scale, we represent the reservoir as an unstructured network of nodes connected by links. For each node-to-node transition, we use our upscaled (t) from a simulation of transport at the smaller scale. We account for small-scale uncertainty by parameterising (t) in terms of sub-scale heterogeneity and Peclet number. We demonstrate the methodology by finding a (t) for each scale of interest taking into consideration the relevant physics at that scale and using the appropriate function in a million-cell reservoir model. We show that the macroscopic behaviour can be very different from that predicted by assuming that the ADE operates at the small scale. Small-scale structure dramatically retards the advance of the plume with the particles becoming trapped in the slow moving pores/regions increasing breakthrough times by an order of magnitude compared to those predicted by the ADE

    COUNTERING ASOCIAL JUSTICE: CONSUMER CULTURE, STANCE AND A CARTOGRAPHY OF ENCOUNTER

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    In Social Foundations classrooms, social justice approaches to questions of difference are certainly part of the curriculum. After teaching numerous Social Foundations courses, I encountered several issues related to the way rigid identity categories were complemented by neoliberal narratives that seemed to limit class conversation in troubling ways—particularly in that students had a difficult time articulating a sense of connection with others beyond their circles of acquaintances. This dissertation is an exploration of how I might resolve some of those dilemmas. I problematize the neoliberal subject position as it relates to questions of social justice, and offer that a relational approach to others may be a useful counter. Inspired by several scholars who address theoretical relational curricular possibilities, I designed a course using a consumer culture approach to constructing Other as a conceptual lens through which to begin talking about difference. Using student data from that class, I introduce stance analysis as a way to interpret the data in terms of the ways students either reinscribed or interrupted a sense of neoliberal relationality. Finally, using the methodological approach of social cartography, I created a map wherein students could plot their encounters across difference. This map is intended as a pedagogical heuristic that could be used to destabilize a self-possessed and individualistic neoliberal sense of self. To this end, the map is oriented toward an approach to self and Other that is contingent, ongoing and contextually mediated. I explore the pedagogical implications of the map and suggest that such approaches may be useful for better understanding how we are relationally constituted. I argue that entering social justice conversations from this vantage point may avoid some of the trappings of rigid identity categories without resorting to commonsense neoliberal narratives

    Exploring Participation: A Study of Venezuelan Bolivarian Schools

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    This thesis examines different ways the process of participation is manifested in Venezuelan Bolivarian primary schools. I argue that the notion of participation in development is contested and has been oversimplified by both advocates and detractors. Using the Venezuelan study as an example, I show that in the same project of participatory development both problematic and positive elements of participation will exist. Problematic elements of participation address inadequate understandings of 'community', question the process of consensus building, and highlight the role of proximity to power centers. Promising developments in the Venezuelan case include incorporation of social programs into the schools, new educational quality indicators, and the establishment of a relationship between school curriculum and local development efforts. As these problematic and promising elements simultaneously occur, I suggest that a different approach to evaluating participation in a development context is necessary. This approach, theorized by social geographers, suggests that analysis of how the space of participation emerges would be more beneficial for assessing the merits of participation. From this perspective, continued study of participatory processes might move beyond the current oversimplification

    Implementing an Evangelism Strategy at Hornsby Baptist Church, Hornsby, Tennessee

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    IMPLEMENTING AN EVANGELISM STRATEGY AT HORNSBY BAPTIST CHURCH HORNSBY, TENNESSEE. Matthew Rhodes Emerson, D.Min. The Southern Baptist Theological Seminary, 2013 Faculty Supervisor: Dr. Jeff K. Walters The project explores an evangelistic interaction between Hornsby Baptist Church and its surrounding community. A strategy is developed for the church to be evangelistically active in a rural context. Chapter 1 describes the purpose, goals, ministry context, rational and definitions, limitations and delimitations. The second chapter presents the biblical and theological basis for personal evangelism. God's desire for personal evangelism is established by providing examples and instruction from both the Old and New Testaments. Chapter 3 provides the theoretical and sociological support. Characteristics of a rural context are presented and evaluated. This section explores the methods and techniques that are best suited for a rural church and community. The final chapters explain the creation and implementation of the rural evangelistic strategy. Detail is given to the church's role in establishing the plan and putting the strategy in place. An evaluation of the project gauged its helpfulness and benefits. This assessment included both strengths and weaknesses, along with adjustments that could be made for future use

    Harm reduction among injecting drug users - evidence of effectiveness

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    This chapter synthesises and evaluates the available direct evidence relating to the impact of needle and syringe programmes (NSPs), opioid substitution treatment (OST), drug consumption rooms (DCRs), and peer naloxone distribution (PND) on HIV/hepatitis C (HCV) incidence/prevalence, injecting risk behaviour and overdose-related mortality. To achieve this, we conducted a review of reviews; a systematic and explicit method used to identify, select and critically appraise relevant findings from secondary level research (systematic reviews and/or meta-analyses) into an evidence briefing. In the absence of high-quality reviews, appraisal of the evidence was supplemented with a targeted review of the primary literature. We find that there is sufficient review-level evidence that OST reduces HIV transmission, while the evidence in support of NSPs reducing HIV transmission is more tentative, and for DCRs currently insufficient. There is tentative evidence that OST has limited effectiveness in reducing HCV transmission, and insufficient evidence to support or discount NSPs or DCRs' ability to reduce HCV transmission. There is sufficient review-level evidence that NSPs, OST and DCRs reduce self-reported injecting risk behaviour. There is sufficient review evidence that OST reduces risk of overdose mortality, but insufficient evidence to support or discount the effect of DCRs or PND on overdose deaths at the community level. Our review shows evidence in support of a variety of harm reduction interventions but highlights an uneven presence of high-quality review evidence. Future evaluation of harm reduction programmes should prioritise methodologically robust study designs

    Is a VC Partnership Greater than the Sum of its Partners?

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    Budget 2016: a summary

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