Air Cooling of PV Panels

In the current study fluid flow and heat transfer characteristics over a heated flat plate were investigated in a closed loop wind tunnel. Two free stream flow regimes were considered; Laminar (turbulence intensity, Tu \u3c 0.5%) and Turbulent. For the laminar free stream case, velocities ranging from 4 to 10 m/s that resulted in Reynolds numbers (Re) up to 346,670 were examined. For the turbulent free stream case, Tu=4%, 8% 12%, and Λ=0.015, 0.021 0.030m were set at the leading edge of the 0.34 by 0.52m heated plate. The aluminum flat plate was heated with supplying powers of 52W and 224W. The heated flat plate was positioned at 0° and 20° tilt and the local heat transfer coefficient in terms of Nusselt number (Nu) was determined along the centreline span of the plate in the streamwise coordinate. Effects of Reynolds number, turbulence intensity (Tu) and integral length scale (Λ/x) on Nusselt number were investigated. The convection heat transfer rate increased in the range of 15% ∼ 40% while the turbulent intensity was raised from 4% to 8%. It was observed that the effect of integral length scale (Λ/x) on heat transfer rate is more significant at larger turbulence intensitie

Lunar Rover Model - Reengineering of an Existing Mobile Platform towards the realization of a Rover Autonomy Testbed

The Automation & Robotics Section of the European Space Agency (ESA) is developing a platform for investigation of different levels of autonomy of planetary rovers. Within this scope a physical flight model is required and the Lunar Rover Model (LRM) is chosen. The LRM is a 4 wheel, medium-scale (120kg) Moon exploration rover breadboard, equipped with a 5- DOF robotic arm. This paper presents the complete refurbishment and motion control redesign. Therefore the rover is equipped with a new distributed motion control architecture based on CANopen. Following the hardware upgrades, a complete dynamic model of the rover is developed in 20sim and algorithms for all the rover locomotion modes are analyzed and implemented. Subsequently all the locomotion control algorithms are ported on the rover and the control performance is evaluated using high accuracy measurement systems

Η σημασία των διακλαδικών ασκήσεων μαζικών απωλειών υγείας

Αυτή η βιβλιογραφική ανασκόπηση εξετάζει τη σημασία των ασκήσεων μαζικών ατυχημάτων (MCΙs) στο πλαίσιο της διαχείρισης και της απόκρισης έκτακτης ανάγκης. Ξεκινά περιγράφοντας την έννοια και τον σκοπό των MCΙs, διερευνώντας πώς είναι αναπόσπαστα στοιχεία για την προετοιμασία και την αποτελεσματική διαχείριση καταστάσεων έκτακτης ανάγκης μεγάλης κλίμακας. Μέσω ανάλυσης θεωρητικών πλαισίων, καθώς και συγκεκριμένων παραδειγμάτων τόσο στην Ελλάδα όσο και στο εξωτερικό, η εργασία υπογραμμίζει τον ρόλο των MCΙ στην ενίσχυση των πρακτικών δεξιοτήτων, των ικανοτήτων λήψης αποφάσεων και της συνεργασίας μεταξύ των υπηρεσιών μεταξύ των πρώτων ανταποκρινόμενων. Επιπλέον, διευκρινίζει τη θετική συσχέτιση μεταξύ της συχνότητας αυτών των ασκήσεων και των βελτιωμένων αποτελεσμάτων απόκρισης στην πραγματική ζωή. Αναφέρονται το Bataclan στη Γαλλία και η άσκηση Πύρανθος στη Μάνη ως παραδείγματα διαχείρισης τέτοιου είδους συμβάντων και προτείνονται συστάσεις για τη μεγιστοποίηση της αποτελεσματικότητας των MCI με βάση αναγνωρισμένες βέλτιστες πρακτικές, συμπεριλαμβανομένης της ενσωμάτωσης νέων τεχνολογιών και προσαρμοστικών στρατηγικών.This bibliographical review, examines the importance of Mass Casualty Exercises (MCIs) in the context of emergency and response management. It begins by describing the concept and purpose of MCIs, exploring the way they constitute an integral part of the preparation and the effective management of large-scale emergencies.Through analysis of theoretical frameworks, as well as specific examples both in Greece and abroad, the paper highlights the role of MCIs in enhancing practical skills, decision-making abilities and inter-agency cooperation among first responders.Furthermore, it clarifies the positive correlation between the frequency of these exercises and improved response outcomes in real life. The Bataclan in France and the Pyranthos exercise in Mani are cited as examples of such event management, and recommendations are proposed to maximize the effectiveness of MCIs based on prime recognized practices, including the integration of new technologies and adaptive strategies

Το Υδρογόνο και η χρήση του ως καύσιμο στις μεταφορές

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Συστήματα Αυτοματισμού

Echolocation clicks of free-ranging Cuvier's beaked whales (Ziphius cavirostris)

Author Posting. © Acoustical Society of America, 2005. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 117 (2005): 3919-3927, doi:10.1121/1.1910225.Strandings of beaked whales of the genera Ziphius and Mesoplodon have been reported to occur in conjunction with naval sonar use. Detection of the sounds from these elusive whales could reduce the risk of exposure, but descriptions of their vocalizations are at best incomplete. This paper reports quantitative characteristics of clicks from deep-diving Cuvier's beaked whales (Ziphius cavirostris) using a unique data set. Two whales in the Ligurian Sea were simultaneously tagged with sound and orientation recording tags, and the dive tracks were reconstructed allowing for derivation of the range and relative aspect between the clicking whales. At depth, the whales produced trains of regular echolocation clicks with mean interclick intervals of 0.43 s (±0.09) and 0.40 s (±0.07). The clicks are frequency modulated pulses with durations of ~200 µs and center frequencies around 42 kHz, –10 dB bandwidths of 22 kHz, and Q3 dB of 4. The sound beam is narrow with an estimated directionality index of more than 25 dB, source levels up to 214 dBpp re: 1 µPa at 1 m, and energy flux density of 164 dB re: 1 µPa2 s. As the spectral and temporal properties are different from those of nonziphiid odontocetes the potential for passive detection is enhanced.Tag was funded in part by a Cecil H. and Ida M. Green Award and the US Office of Naval Research. WHOI fieldwork and tag development was funded by the National Oceanographic Partnership Program (NOPP), the Strategic Environmental Research and Development Program (SERDP) under Program No. CS-1188, and the Packard Foundation, and was supported by BluWest and the NATO Undersea Research Center

Photovoltaics Business Models

This report summarizes work to better understand the structure of future photovoltaics business models and the research, development, and demonstration required to support their deployment

Why do dolphins form mixed-species associations in the Azores ?

Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response

Rooftop Photovoltaics Market Penetration Scenarios

The goal of this study was to model the market penetration of rooftop photovoltaics (PV) in the United States under a variety of scenarios, on a state-by-state basis, from 2007 to 2015