Characterizing the Relationship Between Species Richness and the Seasonal Phenomenon of Tropical Fish Dispersal in New England Waters

The Gulf Stream exerts tremendous influence over oceanographic conditions in the Northwest Atlantic as it transports tropical water to higher latitudes. As the Gulf Stream’s path traverses the east coast of North America, there are implications for the biogeography of marine ecosystems within this range and beyond. While the meandering eddies and warm core rings generated by the Gulf Stream persist year-round, the seasonal warming of New England’s coastal waters afford many tropical species transported by the current temporary residence through the summer and fall. Many aspects that shape this phenomenon and its impact on coastal ecosystems remain a mystery. There is evidence that habitat choice by larval fish affects their distribution within tropical waters. Based on this evidence, tropical species incidence may serve as an indicator of critical nursery habitat and biodiversity hotspots for targeted conservation efforts. From 2015 to 2017, a biodiversity survey of Pleasant Bay, Massachusetts gathered incidence data to estimate species richness at unique sites within the estuary. This survey asserts that sampling species incidence may be a viable and efficient small-scale method to extrapolate native species richness and indicate desirable habitat for non-native tropical species. The distribution of teleost species is the result of many factors. To begin to address the conditions that shape observed richness, characteristics including sediment type and dominant benthic communities were applied as criteria to cluster survey sites for species richness analysis through sample-based rarefaction. The results of this study indicate that small-scale species incidence sampling can be used to highlight critical habitat for conservation protections. The evidence for habitat choice by juvenile fishes highlights the importance of evaluating biodiversity as an indicator for ecosystem health and resiliency. Paired with a broader citizen science network, characteristics including reported species frequency and a review of species life history, are beginning to reveal potential ecosystem impacts that result from the dispersal of expatriated species by the Gulf Stream. As climate change continues to alter marine coastal environments, furthering our understanding of the role expatriated species play in New England waters may improve the allocation of conservation effort and help anticipate future ecosystem changes

Second order effects of structural and material damage on ultrasonic waves.

Damage mechanics is a relatively new and powerful approach to the analysis of material degradation and failure. The idea is to build a continuum model of a solid containing a distribution of microcracks. Such a model, relying on the thermodynamics and statistical mechanics of microcracks, very naturally ties into other continuum models of solids, including acoustic and elastic models. In this dissertation, the impact of material and structural damage is investigated, with an emphasis on the relation between this effect and specific second order ultrasonic effects. The investigation has two main streams. The first, more experimental stream involves damage in the bulk. In this case, we chose to look at fatigue damage in the Ni-based alloy, waspaloy, which is used particularly for high strength, high temperature applications in the aerospace industry, as well as exhibiting very intriguing physical and thermodynamic properties. The approach was to monitor the changes in two second order parameters, the so-called nonlinearity, or beta parameter, and the acousto-elastic parameter. Results of these experiments seem to indicate that the latter is a better indicator of fatigue and damage, at least in this material. The second, more theoretical stream concerns damage along an individual weak interface. In this case, a nonlinear thin layer model was developed for propagation of ultrasonic waves through a weak bonded interface, as well as a time-domain approach to a general solution to this problem for a multiply layered system. This was combined with a simple damage model, and used to demonstrate how poorly bonded interfaces may be interpreted as locally damaged materials. It was also demonstrated how the nonlinearity of intensive ultrasound passing through or reflecting off an interface bond may be used, along with an appropriate damage model, to estimate the ultimate strength of this bond. Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5188. Adviser: Roman Gr. Maev. Thesis (Ph.D.)--University of Windsor (Canada), 2004

Analysis of body force effects on flow boiling and condensation with finite inlet quality

This study explores flow boiling pressure drop of FC-72 in a rectangular channel subjected to single-side and double-sided heating for vertical upflow, vertical downflow, and horizontal flow with positive inlet quality. Analysis of temporal records of pressure transducer signals is used to assess the influences of orientation, mass velocity, inlet quality, heat flux, and single-sided versus double-sided heating on magnitude of pressure drop oscillations, while fast Fourier transforms of the same records are used to capture dominant frequencies of oscillations. Time-averaged pressure drop results are also presented, with trends focusing on the competing influences of body force and flow inertia, and particular attention paid to the impact of vapor content at the test section inlet and the rate of vapor generation within the test section on pressure drop. Several popular pressure drop correlations are evaluated against the present pressure drop database. Predictions are presented for subsets of the database corresponding to low and high ranges of inlet quality and mass velocity. The correlations are ranked based on mean absolute error, overall data trends, and data spread. While most show general success in capturing the data trends, they do so with varying degrees of accuracy. Further, this study concerns the development of a set of mechanistic criteria capable of predicting the flow conditions for which gravity independent flow condensation heat transfer can be achieved. Using FC-72 as working fluid, a control-volume based annular flow model is solved numerically to provide information regarding the magnitude of different forces acting on the liquid film and identify which forces are dominant for different flow conditions. Separating the influence of body force into two components, one parallel to flow direction and one perpendicular, conclusions drawn from the force term comparison are used to model limiting cases, which are interpreted as transition points for gravity independence. Experimental results for vertical upflow, vertical downflow, and horizontal flow condensation heat transfer coefficients are presented, and show that, for the given test section, mass velocities above 425 kg/m2s ensure gravity independent heat transfer. Parametric evaluation of the criteria using different assumed values of mass velocity, orientation, local acceleration, and exit quality show that the criteria obey physically verifiable trends in line with those exhibited by the experimental results. As an extension, the separated flow model is utilized to provide a more sophisticated approach to determining whether a given configuration will perform independent of gravity. Results from the model show good qualitative agreement with experimental results. Additionally, analysis of trends indicate use of the separated flow model captures physics missed by simpler approaches, demonstrating that use of the separated flow model with the gravity independence criteria constitute a powerful predictive tool for engineers concerned with ensuring gravity independent flow condensation heat transfer performance