Typescript (photocopy). / Digitized by Kansas Correctional Industries

Thesis. 1978. M.Arch.A.S.--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / by George Szepesi. / M.Arch.A.S.

Solar energy harvesting using photovoltaic (PV) systems has gained popularity in recent years due to its relative ease of use and its cost efficiency compared to the rest of the clean energy sources. However, to further expand the application of PV systems requires making them more desirable than the other competitive energy sources. The improvement of safety and cost efficiency are requisites for further popularization of PV system application. To satisfy these requisites it is necessary to optimally design the system against the environmental conditions. Wind action is one of the main ambient loads affecting the performance of PV systems. This dissertation aims to investigate the effects of wind load on residential scale roof mounted PV panels and their supporting structures as well as evaluating the structural response of the system to the wind-induced vibration. To achieve these goals, several full- and large-scale experimental tests were performed at the Wall of Wind Experimental Facility at Florida International University (FIU). The wind effects on different PV system and roof configurations were investigated in these tests. The results shed light on the most influential parameters affecting the wind pressures acting on the PV panel surface. In addition, the findings are presented in the form of design pressure coefficients for adoption to future building codes and wind standards. The second phase of the physical testing included the investigation of the actual response of the PV system to the wind action. Because of the dynamic properties of the PV panel, it was expected that the wind induced vibration can affect the dynamic response of the system including the acceleration at the panel surface and support reactions at the racking system to roof interface. To test this theory, two different models of the system were developed, one with the real PV panels and the other one with wooden rigid panels. Comparing the results, it was concluded that the dynamic response of the system was not considerably affected by wind-induced fluctuations. Finally, and to better understand the dynamic response of the system, an analytical model was developed using ANSYS and dynamic analysis was carried out using as input the wind induced pressure data acquired from the physical testing. At the first step, the analytical model was verified by comparing the analytical modal frequencies to the experimental natural frequencies obtained from the hammer test. It was shown that the analytical model can well represent the dynamic properties of the actual model. However, once the reaction output was compared to the loadcell data recorded during the wind tunnel test, there was a considerable discrepancy between the results. It was assumed that the deflection of the supporting structure caused this discrepancy. This assumption was verified and it was concluded that the supporting structure can significantly influence the dynamic response of the system.

This paper investigates the power properties of the Sargan test in the presence of measurement errors in dynamic panel data models. The conclusion from Monte Carlo simulations, and an application on the data used by Arellano and Bond (1991), is that in the very likely case of measurement errors in either the dependent or any of the independent variables, we will, if we rely on the Sargan test, quite likely accept a mis-specified model and end up with biased results.

An examination of static and dynamic dent resistance of structural panel assemblies representing automotive hoods is described in this thesis. Fabricated panel assemblies incorporating typical components of real automotive parts were tested. The panel assemblies included an AA5754 inner panel using an array of teacup supports and an AA6111 closure panel joined with automotive mastic. The assemblies allowed for parametric assessment of numerous factors affecting dent resistance including: panel thickness, panel curvature, panel support configuration and dent site location. An extensive experimental program evaluated various panel combinations under both static and dynamic denting conditions. The measured results illustrate various trends of the different factors affecting dent resistance. The experimental database allows a qualitative assessment of dent resistance for full-scale automotive parts. The importance of support conditions is highlighted. The influence of mastic thickness is found to be a critical consideration. Numerical simulations of the dent test were undertaken using finite element techniques. The numerical predictions offer varying degrees of accuracy. The quantitative results are limited, due to numerical concerns, but the qualitative trends are generally well captured. As well, the relative importance of the various parametric factors is well represented in the numerical results. The interaction of the components at the teacup supports proved to critical to the predictive ability of the models. The method developed to model the interaction was somewhat limited by the available material models within the numerical code used, but offers promise for improved results in future simulations. The modelling method is readily transferred to full-scale automotive panels for assessment of dent resistance early in the design cycle.

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 364-367).

Σκοπός αυτής της διπλωματικής εργασίας, η οποία εκπονήθηκε στο Εργαστήριο Ασύρματης Τηλεπικοινωνίας του Πανεπιστημίου Πατρών, είναι η εξέταση του φαινομένου της υποβάθμισης των χαρακτηριστικών ιδιοτήτων φωτοβολταϊκών πλαισίων πυριτίου. Στα πλαίσια αυτά πραγματοποιήθηκαν μετρήσεις σε πλαίσια πολυκρυσταλλικού και μονοκρυσταλλικού πυριτίου με κατάλληλη πειραματική διάταξη εγκατεστημένη στην οροφή του κτιρίου του τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών. Πραγματοποιήσαμε ημερήσιες μετρήσεις, σε ηλιόλουστες ημέρες,και για μεγάλο χρονικό διάστημα έτσι ώστε να έχουμε όσο το δυνατόν περισσότερα δεδομένα κατάλληλα για επεξεργασία. Ο έλεγχος για πιθανή υποβάθμιση (PID) βασίστηκε σε σύγκριση των πειραματικών αποτελεσμάτων σε διάρκεια τριών ετών και σε ανάλυση αυτών με βάση δύο συγκεκριμένα μοντέλα ερευνητών. Συγκεκριμένα στη σύγκριση τριών ετών ο έλεγχος πραγματοποιήθηκε για παραπλήσιες τιμές προσπίπτουσας ακτινοβολίας και θερμοκρασίας των πλαισίων. Οι συγκρίσεις βάσει των μοντέλων των ερευνητών πραγματοποιήθηκαν σύμφωνα με τα πρότυπα της κάθε μεθόδου. Στο μοντέλο Kahoul συγκρίναμε τα πειραματικά μας δεδομένα σε STC συνθήκες με βάση τα δεδομένα του κατασκευαστή. Στην συνέχεια εξετάσαμε την εφαρμογή του μοντέλου Martinez-Moreno επεκτείνοντας το σε ένα μόνο πλαίσιο που λειτουργεί σε συγκεκριμένες συνθήκες ακτινοβολίας και θερμοκρασίας. Υπήρξαν περιορισμοί όμως σε εξειδικευμένο τεχνολογικό υλικό και αδυναμία εύρεσης περισσότερων παλαιών μετρήσεων κατάλληλων για σύγκριση ώστε να μπορέσουμε να παρουσιάσουμε περισσότερους τρόπους ελέγχου. Τα συμπεράσματα που εξήχθησαν συνηγορούν στην άποψη, η οποία έχει εκφραστεί και από αρκετούς ερευνητές, ότι τέτοια πλαίσια όταν λειτουργούν υπό αυτές τις συνθήκες δεν υφίστανται εμφανή υποβάθμιση των ιδιοτήτων τους, σε μικρό τουλάχιστον χρονικό διάστημα. / The purpose of this thesis, undertaken within the Wireless Communications Laboratory, University of Patras, is to examine the phenomenon of silicon photovoltaic module’s degradation. The experimentation field was held in the roof of the building of Electrical and Computer Engineering department. A polycrystalline and a monocrystalline solar module were used for this study. During the experiments, we tried to make daily measurements on sunny days, so we can collect as much data as possible for appropriate elaboration. Testing for possible degradation was based on a simple comparison of experimental results over three years. In addition, an evaluation of experimental results was held based on two specific researchers’ models. In particular, three years comparing control performed for similar values of incident radiation and temperature of the modules. The comparisons of models based on researchers performed according to the standards of each method. In order to apply the model Kahoul we compared our experimental data at STC conditions with the manufacturer's data. Then we examined the application of the model of MartinezMoreno, by extending it on a single module that works in well defined conditions of radiation and temperature. However, the limitations in our specialized materials technology and the weakness finding more old measurements suitable for comparison did not allow us to apply other methods of control. The conclusions drawn advocate the view, that has been expressed by several researchers, that such modules when operating under these conditions do not appear degradation of their properties, at least in short time.

This study addresses the flexural performance of sandwich panels composed of a polyurethane foam core and glass fibre-reinforced polymer (GFRP) skins. Panels with and without GFRP ribs connecting the skins have been studied. While the motivation of the study was to develop new insulated cladding panels for buildings, most of the work and findings are also applicable to other potential applications such as flooring, roofing and light-weight decking. The study comprises experimental, numerical, and analytical investigations. The experimental program included three phases. Phase I is a comprehensive material testing program of the polyurethane core and GFRP skins and ribs. In Phase II, six medium size (2500x660x78 mm) panels with different rib configurations were tested in one-way bending. It was shown that flexural strength and stiffness have increased by 50 to 150%, depending on the rib configuration, compared to a panel without ribs. In Phase III, two large-scale (9150x2440x78 mm) panels, representing a cladding system envisioned to be used in the field, were tested under a realistic air pressure and discrete loads, respectively. The deflection under service wind load did not exceed span/360, while the ultimate pressure was about 2.6 times the maximum factored wind pressure in Canada. A numerical study using finite element analysis (FEA) was carried out. The FEA model accounted for the significant material nonlinearities, especially for the polyurethane soft core, and the geometric nonlinearity, which is mainly a reduction in thickness due to core softness. Another independent analytical model was developed based on equilibrium and strain compatibility, accounting for the core excessive shear deformation. The model also captures the localized deformations of the loaded skin, using the principals of beam-on-elastic foundation. Both models were successfully validated using experimental results. Possible failure modes, namely core shear failure, and compression skin crushing or wrinkling were successfully predicted. A parametric study was carried out to explore further the core density, skin thickness, and rib spacing effects. As the core density increased, flexural strength and stiffness increased and shear deformations reduced. Also, increasing skin thickness became more effective as the core density increased. The optimal density was 95-130 kg/m3. Reducing the spacing of ribs enhanced the strength up to a certain level; It then stabilized at a spacing of 2.9 times the panel thickness. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-21 16:29:00.315

Ultra-lightweight thermoformed stiffened structures are emerging as a viable option for spacecraft applications due to their advantage over inflatable structures. Although pressurization may be used for deployment, constant pressure is not required to maintain stiffness. However, thermoformed stiffening features are often locally nonlinear in their behavior under loading. This thesis has three aspects: 1) to understand stiffness properties of a thermoformed stiffened ultra-lightweight panel, 2) to develop finite element models using a phased-verification approach and 3) to verify panel response to dynamic loading. This thesis demonstrates that conventional static and dynamic testing principles can be applied to test ultra-lightweight thermoformed stiffened structures. Another contribution of this thesis is by evaluating the stiffness properties of different stiffener configurations. Finally, the procedure used in this thesis could be adapted in the study of similar ultra-lightweight thermoformed stiffened spacecraft structures.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.200).