3,383 research outputs found
Increasing Endurance of an Autonomous Robot using an Immune-Inspired Framework
This paper describes the implementation of an online immune-inspired framework to help increase endurance of an autonomous robot. Endurance is defined as the ability of the robot to exert itself for a long period of time. The immune-inspired framework provides such capability by monitoring the behavior of the robot to ensure continuous and safe behavior. The immune-inspired framework combines innate and adaptive immune inspired algorithms. Innate uses a dendritic cell based innate immune algorithm, and adaptive uses an instance based B-cell approach. Results presented in this paper shows that when the robot is implemented with the immune-inspired framework, health and survivability of a robot is improved, therefore increasing its endurance
AdS black holes with arbitrary scalar coupling
A general class of axionic and electrically charged black holes for a
self-interacting scalar field nonminimally coupled to Einstein gravity with a
negative cosmological constant is presented. These solutions are the first
examples of black holes with an arbitrary nonminimal coupling in four
dimensions. Moreover, due to the presence of two three-forms fields, the
topology of the horizon of these black holes is planar. We discuss some
properties of these solutions electing particular values of the nonminimal
coupling parameter. A special case arises when , for which the
gravitational field is confined in a region close to the event horizon. We also
show that these black holes emerge from stealth AdS configurations as the
axionic fields are switched on, and that they can be generated through a
Kerr-Schild transformation. Finally, in the appendix, we extend these results
to arbitrary dimension.Comment: 23 page
Laser ignition of iso-octane air aerosols
Iso-octane aerosols in air have been ignited with a focused Nd:YAG laser at pressures and temperatures of 100kPa and 270K and imaged using schlieren photography. The aerosol was generated using the Wilson cloud chamber technique. The droplet diameter, gas phase equivalence ratio and droplet number density were determined. The input laser energy and overall equivalence ratio were varied. For 270mJ pulse energies initial breakdown occurred at a number of sites along the laser beam axis. From measurements of the shock wave velocity it was found that energy was not deposited into the sites evenly. At pulse energies of 32mJ a single ignition site was observed. Overall fuel lean flames were observed to locally extinguish, however both stoichiometric and fuel rich flames were ignited. The minimum ignition energy was found to depend on the likelihood of a droplet existing at the focus of the laser beam
Impact of EU-FDI on economic growth in Middle Eastern countries
This paper develops a simultaneous equations model to test the process of
interaction between foreign direct investment, exports and economic growth in
three Middle Eastern countries: Egypt, Jordan, Oman, and test for any possible
feedback effects. Most of the FDI in these countries flows from the EU. The
simultaneous equations model results suggest that higher rates of economic
growth result in a greater inflow of foreign capital. The regression results also
suggest that interest rate differentials exert a much stronger effect than economic
growth on the attraction of foreign capital in the case of Egypt. However, this
variable does not seem to play a significant role in the case of Oman. Moreover,
the simultaneous equations model results suggest that there is a feedback effect in
the relationship between economic growth and capital inflow in all sample
countries. A greater inflow of foreign capital leads to growth in the exports of
good and services. The expansion in exports leads to growth in GNP, which in
turn, encourages the attraction of more foreign capital.peer-reviewe
Control of Solar Thermal Linear Fresnel Collector Plants in Single Phase and Direct Steam Generation Modes
Ein wesentlicher Unterschied erneuerbarer Energiequellen zu fossilen EnergietrÀgern
liegt in der zeitlichen VerfĂŒgbarkeit. Im Gegensatz zu fossil
angetriebenen Prozessen lÀsst sich die Energiezufuhr nicht regeln. Dies
stellt vor allem die Solarenergie vor eine wesentliche Herausforderung. Die
Sonne als Energiequelle unterliegt nicht nur tages bzw. jahreszeitlichen
Schwankungen, sie ist oft auch nicht vorhersehbar. Dieser scheinbar kleine
Unterschied zur fossilen Energiegewinnung, hat zu weitreichenden Forschungsak
tivitÀten in verschiedenen Bereichen der Wissenschaft und des Ingenieurwesens
gefĂŒhrt, darunter die Entwicklung von Speichertechnologien und
hybrider Systeme, die Abbildung des dynamischen Verhaltens, insbesondere
im Teillastbetrieb und nicht zu Letzt die entsprechende Ausarbeitung
verschiedener Regelsysteme.
Das Hauptziel der vorliegenden Arbeit ist die Entwicklung geeigneter
Regelgesetze fĂŒr solarthermische Anlagen um der intermittierenden Natur
der Sonne als Energieressource gerecht zu werden. Eine gute Regelung
erhöht den Solarertrag, reduziert StillstÀnde, bietet eine optimierte Wahl
des Betriebspunktes und garantiert die StabilitÀt und Robustheit des Systems,
mit der Personen und Anlagensicherheit als oberste PrioritÀt.
Die Thesis gliedert sich in zwei Hauptteile. Der erste Teil beinhaltet
die Regelungstechnik konzentrierender, solarthermischer Systeme mit einphasigen
Strömungen. Als wesentliche RegelgröĂe dient die Kollektoraustritttemperatur.
Mehrere Regelsysteme wurden unter verschiedenen Rahmenbedingungen und
Prozessanforderungen experimentell getestet. Eine erweiterte PID-Regelung
mit geeigneten Vorsteuerungsschleifen zeigt sehr gute Resultate, zudem lÀsst
sich die Gestaltung und Umsetzung des Regelsystems einfach halten.
Der zweite Teil der Arbeit widmet sich dem Regelsystem im solaren
Direktverdampfungsbetrieb. Hierbei ist die HauptregelgröĂe der benötigte
Dampfdruck an der Prozessschnittstelle. Im Direktverdampfungsbetrieb
wird die Anlage als MehrgröĂenregelsystem betrachtet. Zwei Regelkonzepte
wurden mit der vorliegenden Arbeit entwickelt und getestet. Eines der
Konzepte basiert auf einer erweiterten PID-Regelung mit Vorsteuerung.
Dieses wurde erfolgreich umgesetzt und unter Realbedingungen ĂŒber mehrere
Jahre intensiv getestet. Das zweite Konzept stĂŒtzt sich auf die Theorie der
modellbasierten, ModellprÀdiktive Regelung (MPC). Hierbei handelt es sich
um ein komplexes, entwicklungsintensives, Regelkonzept. Der wesentliche
Vorteil ist die universelle Anwendbarkeit, mit reduziertem Aufwand fĂŒr
Implementierung, Bewirtschaftung und Inbetriebnahme.
Die vorliegende Thesis zeigt, dass sich trotz der komplexen Dynamik
solarthermischer Grossanlagen mit den vorgeschlagenen Regelkonzepten
eine zuverlÀssige, robuste und wartungsarme Energieversorgung bewerkstelligen lÀsst
Adaptive and Online Health Monitoring System for Autonomous Aircraft
Good situation awareness is one of the key attributes required to maintain safe flight, especially for an Unmanned Aerial System (UAS). Good situation awareness can be achieved by incorporating an Adaptive Health Monitoring System (AHMS) to the aircraft. The AHMS monitors the flight outcome or flight behaviours of the aircraft based on its external environmental conditions and the behaviour of its internal systems. The AHMS does this by associating a health value to the aircraft's behaviour based on the progression of its sensory values produced by the aircraft's modules, components and/or subsystems. The AHMS indicates erroneous flight behaviour when a deviation to this health information is produced. This will be useful for a UAS because the pilot is taken out of the control loop and is unaware of how the environment and/or faults are affecting the behaviour of the aircraft. The autonomous pilot can use this health information to help produce safer and securer flight behaviour or fault tolerance to the aircraft. This allows the aircraft to fly safely in whatever the environmental conditions. This health information can also be used to help increase the endurance of the aircraft. This paper describes how the AHMS performs its capabilities
Attitudes of Private Firms in GCC Countries Towards Employing Indian Nationals: A Case Study
This paper tries to find out how private firms engaged in different economic activities in GCC countries differ in terms of their preference ratings of various attributes of Indian employees
Rapidly reconfigurable optical phase encoder-decoders based on fiber Bragg gratings
We demonstrate the capacity for fast dynamic reconfiguration of optical code-division multiple access (OCDMA) phase en/decoders based on fiber Bragg gratings and a thermal phase-tuning technique. The tuning time between two different phase codes is measured to be less than 2 s. An OCDMA system using tunable-phase decoders is compared with a system using fixed-phase decoders and, although the system using fixed-phase decoders exhibits a shorter output autocorrelation pulsewidth and lower sidelobes, the system using tunable-phase decoders has advantages of flexibility and a more relaxed requirement on the input pulsewidth
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