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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Aerostructural Optimization of Non-planar Lifting Surfaces

Jansen, Peter Willi 14 July 2009 (has links)
Non-planar lifting surfaces offer potentially significant gains in aerodynamic efficiency by lowering induced drag. Non-aerodynamic considerations, such as structures can impact the overall efficiency. Here, a panel method and equivalent beam finite element model are used to explore non-planar configurations taking into account the coupling between aerodynamics and structures. A single discipline aerodynamic optimization and a multidisciplinary aerostructural optimization are investigated. Due to the complexity of the design space and the presence of multiple local minima, an augmented Lagrangian particle swarm optimizer is used. The aerodynamic optimum solution found for rectangular lifting surfaces is a box wing, while allowing for sweep and taper yields a joined wing. Adding parasitic drag in the aerodynamic model reduces the size of the non--planar elements. The aerostructural optimal solution found is a winglet configuration when the span is constrained and a wing rake when there is no such constraint.
212

Strategic Surveillance System Design for Ports and Waterways

Cimren, Elif I. 2009 May 1900 (has links)
The purpose of this dissertation is to synthesize a methodology to prescribe a strategic design of a surveillance system to provide the required level of surveillance for ports and waterways. The method of approach to this problem is to formulate a linear integer programming model to prescribe a strategic surveillance system design (SSD) for ports or waterways, to devise branch-and-price decomposition (B
213

Design, testing, and performance of a hybrid micro vehicle - the Hopping Rotochute

Beyer, Eric W. January 2009 (has links)
Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Costello, Mark. Part of the SMARTech Electronic Thesis and Dissertation Collection.
214

Restoration of Displaced Cast-in-Place Concrete Slabs on Grade with the Use of the ISB-07 Subsurface Support Bracket

Busquets, Jose Carlos 01 January 2011 (has links)
The restoration of foundations of residential and light commercial structures that have been affected by differential displacement resulting from problematic soil conditions has been an ongoing issue since early times. In Florida, the issue of structures being affected by subsidence of soils related to sinkhole activity has been a problem that has gained more interest and exposure within the last 20 years. Structures affected by sinkholes have been historically addressed by remediating the soil mechanism which caused the structure to displace and then structurally addressing the portions of the structure that have displaced with steel underpins installed on the foundation. More comprehensive soil investigations are revealing that multiple soil mechanisms are contributing to the displacement of structures. Based on case studies of structures being partially underpinned on soils affected by multiple problematic conditions, Engineers have been forced to develop more comprehensive foundation restoration plans. These comprehensive plans were intended to address the potential for differential movement between portions of the structure supported by post-construction deep foundations and those portions of the structure that remain bearing on the soil. With limited products available for Engineers to rely on to adequately support cast-in-place concrete slabs on grade, the comprehensive restoration of structures on problematic soils has become cost prohibitive and structures throughout the state of Florida are either being left in a distressed state or are being repaired with substandard repair methods. Being exposed to this ongoing trend manifested the need to develop a solution to this detrimental problem. Having been involved in the design phase and the restoration process of structures affected by displacement, a comprehension was developed on the products available to support and restore slabs on grade and where those products were deficient. After several prototypes, the development of a new support bracket was invented which would more efficiently support and lift displaced slabs. This slab support bracket was named the ISB-07. This thesis is based on the research and development that was conducted on the ISB-07 and on different slab specimens. This research was performed to demonstrate that a slab supported by the multi pivoting arm ISB-07 slab bracket can be more efficient than previous support methods. It was concluded, after performing full scale testing, ultimate load testing, stress analysis, computation and finite element analysis, that the influence area of support provided to a cast-in-place concrete slab by the ISB-07 is greater than previous support methods. Therefore, the required spacing between interior slab supports when the ISB-07 is utilized is significantly increased and therefore the amount of interior supports warranted is reduced. With this reduction in interior supports, the disturbance of the existing structures slab is minimized. This reduction in disturbance and materials needed to stabilize structures directly translates to a cost savings which in turn will lead to more structures being properly repaired.
215

Predicting the behavior of horizontally curved I-girders during construction

Stith, Jason Clarence 09 November 2010 (has links)
The majority of a bridge designer’s time is spent ensuring strength and serviceability limit states are satisfied for the completed structure under various dead and live loads. Anecdotally, the profession has done an admirable job designing safe bridges, but engineering the construction process by which bridges get built plays a lesser role in the design offices. The result of this oversight is the complete collapse of a few large bridges as well as numerous other serviceability failures during construction. According to the available literature there have been only a few attempts to monitor a full-scale bridge in the field during the entire construction process. Another challenge for engineers is the lack of analysis tools available which predict the behavior of the bridge during the intermediate construction phases. During construction, partial bracing is present and the boundary conditions can vary significantly from the final bridge configuration. The challenge is magnified for complex bridge geometries such as curved bridges or bridges with skewed supports. To address some of the concerns facing engineers a three span curved steel I-girder bridge was monitored throughout the entire construction process. Field studies collected data on the girder lifting behavior, partially constructed behavior, and concrete deck placement behavior. Additional analytical studies followed using the field measurements to verify the finite element models. Finally, conclusions drawn from the physical and analytical testing were utilized to derive equations that predicted behavior, and analysis tools were developed to provide engineers with solutions to a wide range of construction related problems. This dissertation describes the development of two design tools, UT Lift and UT Bridge. UT Lift is a macro-enabled Excel spreadsheet that predicts the behavior of curved I-girders during lifting. The derivation of the equations necessary to accomplish these calculations and the implementation are described in this dissertation. UT Bridge is a PC-based, user-friendly, 3-D finite element program for I-girder bridges. The basic design philosophy of UT Bridge aims to allow an engineer to take the information readily available in a set of bridge drawings and easily input the necessary information into the program. A straight or curved I-girder bridge with any number of girders or spans can then be analyzed with a robust finite element analysis for either the erection sequence or the concrete deck placement. The development of UT Bridge as well as the necessary element formulations is provided in this dissertation. / text
216

Το σχήμα ανόρθωσης για διακριτούς μετασχηματισμούς κυματιδίων μέσω πινάκων πολυωνύμων Laurent

Ανδρεοπούλου, Ευφροσύνη 10 June 2009 (has links)
Στόχος της παρούσας διπλωματικής εργασίας είναι η μελέτη του σχήματος ανόρθωσης (lifting) που πρότεινε ο Sweldens για την αναπαράσταση διακριτών μετασχηματισμών κυματιδίων και ειδικότερα η παρουσίαση του μαθηματικού υπόβαθρου της μεθόδου που χρησιμοποιεί γινόμενα πινάκων με συντελεστές πολυώνυμα Laurent. Ο μετασχηματισμός κυματιδίου προσφέρει μια διαφορετική προσέγγιση στο πρόβλημα της αποδόμησης ενός διακριτού σήματος στο επίπεδο χρόνου-συχνότητας, καθώς είναι βασισμένος στην πολυεπίπεδη τεχνική πολλαπλής ανάλυσης σήματος, γι’ αυτό και αποτελεί ένα ιδιαίτερα εύχρηστο και εύκολα προσαρμόσιμο εργαλείο σε πολλές εφαρμογές. Παρουσιάζουμε ένα παράδειγμα ενός διακριτού σήματος στο οποίο εφαρμόζουμε τεχνικές πρόβλεψης και διόρθωσης των συστατικών του, κάνοντας μια πολυεπίπεδη ανάλυση που ονομάζεται ανάλυση πολλαπλής ευκρίνειας. Στα διάφορα στάδια αυτής της ανάλυσης ακολουθείται η μέθοδος ανόρθωσης (lifting) που αποτελείται από μια σειρά βημάτων πρόβλεψης και διόρθωσης των συστατικών του διακριτού σήματος. Με τη χρήση αυτής της μεθόδου μπορούμε να αναλύσουμε όλους τους μετασχηματισμούς κυματιδίων τους οποίους χρησιμοποιούμε για να αποδομήσουμε ένα διακριτό σήμα στα συστατικά του. Για την εφαρμογή του σχήματος ανόρθωσης χωρίζουμε το διακριτό σήμα στα άρτια και περιττά μέρη του και στη συνέχεια εφαρμόζουμε διαδοχικούς μετασχηματισμούς πρόβλεψης και διόρθωσης για τα δύο αυτά μέρη του σήματος. Στη συνέχεια αναπαριστούμε την παραπάνω ανάλυση μέσω του z-μετασχηματισμού με χρήση πολυωνύμων Laurent. Ο μετασχηματισμός ανάλυσης κυματιδίου, στον z-μετασχηματισμό, μετατρέπεται σε πολλαπλασιασμό πινάκων με στοιχεία πολυώνυμα Laurent. Η εφαρμογή των βημάτων της μεθόδου ανόρθωσης, ουσιαστικά, οδηγεί σε μια σταδιακή απλοποίηση των παραπάνω πολυωνύμων, η οποία γίνεται με τη χρήση του αλγορίθμου διαίρεσης πολυωνύμων. Παρουσιάζουμε και αναλύουμε τα θεωρήματα στα οποία στηρίζεται η μέθοδος και δίνουμε συγκεκριμένα παραδείγματα. / -
217

Neuromuscular Control of Aerodynamic Power Output via Changes in Wingbeat Kinematics in the Flight Muscles of Ruby-throated Hummingbirds (Archilochus colubris)

Mahalingam, Sajeni 22 November 2012 (has links)
While producing the highest power output of any vertebrate, hovering hummingbirds must also precisely modulate the activity of their primary flight muscles to vary wingbeat kinematics and modulate lift production. By examining how electromyograms (EMGs) and wingbeat kinematics of hummingbirds change in response to varying aerodynamic power requirements during load lifting trials and air density reduction trials, we can better understand how aerodynamic power output is modulated via neuromuscular control. During both treatments increased lift was achieved through increased stroke amplitude, but wingbeat frequency only increased during air density reduction trials. These changes in wingbeat kinematics were matched by increased EMG intensities as aerodynamic power output requirements increased. Despite the relative symmetry of the hovering downstroke and upstroke, the timing of activation and number of spikes per EMG burst were consistently different in the supracoracoideus compared to the pectoralis, likely reflecting differences in muscle morphology.
218

Neuromuscular Control of Aerodynamic Power Output via Changes in Wingbeat Kinematics in the Flight Muscles of Ruby-throated Hummingbirds (Archilochus colubris)

Mahalingam, Sajeni 22 November 2012 (has links)
While producing the highest power output of any vertebrate, hovering hummingbirds must also precisely modulate the activity of their primary flight muscles to vary wingbeat kinematics and modulate lift production. By examining how electromyograms (EMGs) and wingbeat kinematics of hummingbirds change in response to varying aerodynamic power requirements during load lifting trials and air density reduction trials, we can better understand how aerodynamic power output is modulated via neuromuscular control. During both treatments increased lift was achieved through increased stroke amplitude, but wingbeat frequency only increased during air density reduction trials. These changes in wingbeat kinematics were matched by increased EMG intensities as aerodynamic power output requirements increased. Despite the relative symmetry of the hovering downstroke and upstroke, the timing of activation and number of spikes per EMG burst were consistently different in the supracoracoideus compared to the pectoralis, likely reflecting differences in muscle morphology.
219

Performance Prediction Of Horizontal Axis Wind Turbines Using Vortex Theory

Yucel, Burak 01 December 2004 (has links) (PDF)
iv Performance prediction of HAWTs is important because it gives an idea about the power production of a HAWT in out of design conditions without making any experiments. Since the experiments of fluid mechanics are difficult to afford, developing some models is very beneficial. There are some models developed about this subject using miscellaneous methods. In this study, one can find &ldquo / Vortex Theory&rdquo / among one of these theories. Some basic 3D aerodynamics was discussed in order to make the reader to understand the main subject of this study. Just after that, performance prediction of constant speed, stall controlled HAWTs was discussed. In order to understand the closeness of this theory to experiments, as a sample, NREL &ldquo / Combined Experiment Rotor&rdquo / was considered. Performances obtained by AEROPOWER, written in Visual Basic 6.0 and Excel combination, and experimental results were compared for different wind velocities. Acceptable results were obtained for wind speeds not much different than the design wind speed. For relatively lower wind speeds, due to &ldquo / turbulence&rdquo / , and for relatively higher wind speeds, due to &ldquo / stall&rdquo / , the program did not give good results. In the first case it has not given any numerical result. Power curves were obtained by only changing the settling angle, and only changing the rotor angular speed using AEROPOWER. It was seen that, both settling angle and rotor rpm values influence the turbine power output significantly.
220

A biomechanical analysis of patient handling techniques and equipment in a remote setting.

Muriti, Andrew John, Safety Science, Faculty of Science, UNSW January 2005 (has links)
Remote area staff performing manual patient handling tasks in the absence of patient lifting hoists available in most health care settings are at an elevated risk of musculoskeletal injuries. The objective of this project was to identify the patient handling methods that have the lowest risk of injury. The patient handling task of lifting a patient from floor to a chair or wheelchair is a common task performed in a remote health care setting. The task was performed utilising three methods, these being: (1) heads/tails lift, (2) use of two Blue MEDesign?? slings and (3) use of a drawsheet. The task of the heads/tails lift was broken down into two distinctly separate subtasks: lifting from the (1) head and (2) tail ends of the patient load. These techniques were selected based on criteria including current practice, durability, portability, accessibility, ease of storage and cost to supply. Postural data were obtained using a Vicon 370 three - dimensional motion measurement and analysis system in the Biomechanics & Gait laboratory at the University of New South Wales. Forty reflective markers were placed on the subject to obtain the following joint angles: ankle, knee, hip, torso, shoulder, elbow, and wrist. The raw data were converted into the respective joint angles (Y, X, Z) for further analysis. The postural data was analysed using the University of Michigan???s Three-Dimensional Static Strength Prediction Program (3D SSPP) and the relative risk of injury was based on the following three values: (1) a threshold value of 3,400 N for compression force, (2) a threshold value of 500 N for shear force, and (3) population strength capability data. The effects on changes to the anthropometric data was estimated and analysed using the in-built anthropometric data contained within the 3D SSPP program for 6 separate lifter scenarios, these being male and female 5th, 50th and 95th percentiles. Changes to the patient load were estimated and analysed using the same computer software. Estimated compressive and shear forces were found to be lower with the drawsheet and tail component of the heads/tails lift in comparison to the use of the Blue MEDesign?? straps and head component of the heads/tails lift. The results obtained for the strength capability aspect of each of the lifts indicated a higher percentage of the population capable of both the drawsheet and tail end of the heads/tails lift. The relative risk of back injury for the lifters is distributed more evenly with the drawsheet lift as opposed to the heads/tails (tail) lift where risk is disproportionate with the heavier end being lifted. The use of lifter anthropometrics does not appear to be a realistic variable to base assumptions on which group of the population are capable of safely performing this task in a remote setting. This study advocates the use of the drawsheet lift in a remote setting based on the author???s experience and the biomechanical results obtained in this study. The drawsheet lift is both more accessible and provides a more acceptable risk when more than two patient handlers are involved, in comparison to the other lifts utilised lifting patients from floor to a chair.

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