1,032 research outputs found

    Fluvial system restoration – case study: river Tua

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    Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente, Perfil de Engenharia de Sistemas AmbientaisThe purpose of this thesis is to provide river basin managers with a framework for river restoration. To that end, it presents and discusses the relevant information on the current condition of the river Tua, in northern Portugal, and establishes what can be done to restore the river basin in order to protect the most important drainage basin's functions and ecosystems. It is intended that this thesis will serve as an example of the application of current knowledge on freshwater restoration which can be emulated by future managers in their efforts to restore this, or any water body they wish to. To this purpose, the thesis analyzes demographic data on the municipalities of the Tua drainage basin. It discusses literature and research on the subject of river restoration and important river processes in the following chapter, so as to introduce important theory concepts to have in mind when designing any restoration efforts. In its methodology, the techniques and data assessment tools used in the process of evaluating the river basin's conditions are described and defined, allowing interested managers to review and adapt to the specific needs of drainage basins anywhere. Finally, it presents a practical point-of-view intended to be applied on other freshwater bodies. The thesis includes the realization of an assessment physical characteristics and status of the Tua river reach, it splits up the drainage basin into several different sub-basins, for individual study, and, after a discussion of the conclusions drawn from the assessment for the whole drainage basin, it presents arguments for choosing the sub-sections which present the highest risk to the drainage basin and, as such, require priority action. This section also includes a presentation of the arguments in support of specific techniques to be put into place, given the specific needs of the sub-basin and the restoration goals for the entire drainage basin

    Optimal active vibration absorber: Design and experimental results

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    An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback

    Greek ts/dz as Internally Complex Segments: Phonological and Phonetic Evidence

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    The "affricate dream" of Householder (1964), in which Modern Greek ts/dz are reduced to clusters of independently occurring segments (thus, ts is analyzed as /t + s/), is examined here in the light of two types of evidence not previously considered: instrumental measurements of the duration of the sounds in question compared with related sounds, and the proper formulation of a dissimilatory dialectal sound change. This evidence shows that the best analysis recognizes these sounds as single segments but with internal complexity, as suggested, but not overtly argued for, in Joseph & Philippaki-Warburton (1987)

    Intraoperative Indocyanine Green Laser Angiography in Pediatric Autologous Ear Reconstruction.

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    Skin flap vascularity is a critical determinant of aesthetic results in autologous ear reconstruction. In this study, we investigate the use of intraoperative laser-assisted indocyanine green angiography (ICGA) as an adjunctive measure of skin flap vascularity in pediatric autologous ear reconstruction. Twenty-one consecutive pediatric patients undergoing first-stage autologous total ear reconstruction were retrospectively evaluated. The first 10 patients were treated traditionally (non-ICGA), and the latter 11 patients were evaluated with ICGA intraoperatively after implantation of the cartilage construct and administration of suction. Relative and absolute perfusion units in the form of contour maps were generated. Statistical analyses were performed using independent sample Student t test. Statistically significant differences in exposure and infection were not found between the 2 groups. However, decreased numbers of surgical revisions were required in cases with ICGA versus without ICGA (P = 0.03), suggesting that greater certainty in skin flap perfusion correlated with a reduction in revision surgeries. In cases of exposure, we found an average lowest absolute perfusion unit of 14.3, whereas cases without exposure had an average of 26.1 (P = 0.02), thereby defining objective parameters for utilizing ICGA data in tailoring surgical decision making for this special population of patients. Defined quantitative parameters for utilizing ICGA in evaluating skin flap vascularity may be a useful adjunctive technique in pediatric autologous ear reconstruction
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