The finite element method is used to investigate failure mechanisms in pin-hanger connection in aging highway bridges. Bridge pins and hangers are typically considered as critical elements whose failure may result in partial or entire collapse of the structure. The primary function of a pin-hanger connection is to allow for...
This report includes the findings of acoustic emission (AE) tests on the Fremont tied arch bridge in Portland Oregon conducted by research engineers from the Infrastructure Technology Institute of Northwestern University on March 24th, 1997.
Acoustic emission (AE) testing was used to identify the source of audible “bangs” generated during opening and closing of a large, double-leaf rolling-lift bascule bridge. The data were analyzed using a combination of well-established AE
techniques, including first hit analysis (FHA), planar location analysis, and linear location analysis. The FHA...
Past efforts to reintroduce the native legume species Desmodium glutinosum and Lespedeza violacea into restored woodlands have not produced self-sustaining populations. Proposed factors preventing reintroduction include herbivory, persistent environmental effects of invasive shrubs, poor performance of commercial Rhizobium inoculants, and competitive displacement associated with elevated nitrogen availability. To address these...
Because long-chain n-alkanes (n-C21 to n-C37) are found in the epicuticular leaf waxes of all vascular plants and are stable, long-lived molecules, the study of their molecular and isotopic compositions stands to serve as a potentially powerful tool in the fields of modern chemotaxonomy and paleoecology. This study attempts to...
Understanding the factors that drive the maintenance of polymorphisms in plant populations has long been of interest to evolutionary biology. Variation in floral traits has often been attributed to selection by pollinators, but recent evidence suggests that other biotic and abiotic agents may also contribute to floral trait differentiation. In...
Many preventable behaviors contribute to adolescent mortality and morbidity. Non-adherence to preventive measures represents a challenge and has been associated with worse health outcomes in this population. The widespread use of electronic communication technologies by adolescents, particularly the use of text messaging (short message service, SMS) and mobile phones, presents...
Since Reduced Emissions from Deforestation and Degradation “Plus” (REDD+) starting gaining traction in the UN climate negotiations in 2007, its architects and scholars have grappled with its community-level justice implications. On the one hand, supporters argue that REDD+ will help the environment and forest-dependent communities by generating payments for forest...
US surveillance of sexually transmitted diseases (STDs) is often delayed and incomplete which creates missed opportunities to identify and respond to trends in disease. Internet search engine data has the potential to be an efficient, economical and representative enhancement to the established surveillance system. Google Trends allows the download of...
One of the most notable recent developments in survey research is the increased usage of online convenience samples
drawn from Amazon’s Mechanical Turk (MTurk). While scholars have noted various social and political differences (e.g.,
age, partisanship) between MTurk and population-based samples, the breadth and depth of these variations remain unclear....