653 research outputs found

    Evaluating the Relationship Between Meander-Bend Curvature, Sediment Supply, and Migration Rates

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    River meander migration plays a key role in the unsteady “conveyor belt” of sediment redistribution from source to sink areas. The ubiquity of river meandering is evident from remotely sensed imagery, which has allowed for long-term, high-resolution studies of river channel change and form-process relationships. Empirical, experimental, and theoretical research approaches have described two distinct relationships between channel curvature and river channel migration rates. In this study, we employ a novel application of time-series algorithms to calculate migration rates and channel curvature at sub-meander bend length scales using 6 decades of aerial imagery spanning 205 km of the Minnesota River and Root River, Minnesota, USA. Results from the Minnesota River provide the first empirical evidence demonstrating how migration-curvature relations break down for rivers with low sediment supply, which is supported by the Root River data set. This not only highlights the importance of sediment supply as a driver of river migration, but also supports a simple means to detect river reaches lacking sediment supply. Furthermore, results from both rivers demonstrate that sub-meander bend measurement scales are most appropriate for studying channel migration rates and further indicate that a quasi-linear relationship—rather than the more commonly inferred peaked relationship—exists between channel curvature and migration rates. The highest migration rates are associated with the highest measured channel curvatures in our data set, after accounting for a spatial lag of channel widths. These findings are consistent with flume experiments and empirical data across diverse geologic and climatic environments

    Afro-Indigenous Hondurans in Resistance: U.S. Drug War, Violent Displacement, and Migration (2015-10-15)

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    Lecture by Alfredo Lopez, Ofraneh, The Black Fraternal Organization of Honduras, titled Afro-Indigenous Hondurans in Resistance: U.S. Drug War, Violent Displacement, and Migratio

    Cuba as Sustainability Lab: Observations on Agriculture, Food, Health and Community in a Time of Change (2015-05-06)

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    Dr. Handel Hanson Professor, UMD Geography Department Director, UMD Sustainable Agricultural Project speaks on Cuba as Sustainability Lab: Observations on Agriculture, Food, Health and Community in a Time of Chang

    Identifying the Leaders: Applying Diffusion of Innovation Theory to Use of a Public Bikeshare System in Vancouver, Canada

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    Public bike share programs are growing in popularity globally with increasing recognition of their potential and accrued benefits for mobility, health, and the environment. Any city planning to launch a program will be keenly interested in understanding who may use it, in order to enable strategic marketing that will facilitate quick uptake and adoption. We applied the Diffusion of Innovation Theory to data from a population-based telephone survey to characterize who is most likely to use a new public bike share program. The telephone survey of 901 Vancouver residents was conducted prior to the launch of Vancouver\u27s public bike share program. Results showed that a majority (n=614/901, 69.1%, 95% CI: 66.3%/72.7%) of respondents thought that public bike share was a good idea, however, only a quarter (n=217/901, 24.2%, 95% CI: 21.1%, 27.3%) said they would be either likely or very likely to use the program. Logistic regression identified characteristics associated with greater and lower likelihood of use. These characteristics were used to create an adoption curve that defines population segments anticipated to be the leaders in adopting the program. The theory was used to develop implementation recommendations to maximize program uptake including ensuring that the program has tangible advantages over driving or transit; is affordable and easy to try out; integrates with transit and car share opportunities; and appeals to social trends such as environmental responsibility. These results can assist planning and promotion in cities set to launch public bike share programs

    Detecting Foundation Pile Length of High-Mast Light Towers

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    (c) 1006625 (wo) 62The goal of the project is to establish a non-destructive field testing technique, including a data analysis algorithm, for determining in-place pile lengths by way of seismic waves. The length of each pile supporting a high-mast light tower (HMLT) will be identified through a systematic sensing approach that includes (i) collection and classification of the pertinent foundation designs and soil conditions; (ii) use of ground vibration waveforms captured by a seismic cone penetrometer; (iii) three-dimensional visco-elastodynamic finite element analysis (FEA) used as a tool to relate the sensory data to in situ pile length; (iv) use of machine learning (ML) algorithms, trained with the outputs of FEA simulations, to solve the germane inverse problem; (v) HMLT field testing; and (vi) analysis-driven data interpretation. Several hundred HMLTs throughout Minnesota have foundation systems, typically concrete-filled steel pipe piles or steel H-piles, with no construction documentation (e.g., pile lengths). Reviews of designs within current standards suggest that some of these foundations may have insufficient uplift capacity in the event of peak wind loads. Without knowledge of the in situ pile length, an expensive retrofit or replacement program would need to be conducted. Thus, developing a screening tool to determine in situ pile length \u2014 as compared to a bulk retrofit of all towers with unknown foundations \u2014 would provide significant cost savings

    The Egypt labor market panel survey: introducing the 2012 round

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    This paper introduces the 2012 round of the Egypt Labor Market Panel Survey (ELMPS), a publicly-available nationally representative longitudinal household survey. We describe the key characteristics of the ELMPS, including the samples and questionnaires for each round. Additionally, we examine the attrition processes observed in the panel and discuss the creation of weights to correct for attrition. We compare our data to other statistical sources for Egypt to evaluate the sample's representativeness. To demonstrate how the ELMPS allows for an improved understanding of the labor market, we compare unemployment trends using the ELMPS and other data on unemployment in Egypt
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