44,802 research outputs found
Application of the domain-integrated field relations method to the solution of large scale static and stationary magnetic field problems
No full textAuthor accepted manuscript of: “Application of the domain-integrated field relations method to the solution of large scale static and stationary magnetic field problems” IEEE Transactions on Magnetics, vol. 38, no. 2, pp. 465-468, Mar., 2002Electrical Engineering, Mathematics and Computer Scienc
Doelpuntdetectie met behulp van radartechnologie
No full textMaxad is een onlangs opgericht bedrijf dat begin 2009 op de markt zal komen met een systeem dat de reclameopbrengsten bij voetbalwedstrijden aanzienlijk zal verhogen. Het systeem is in staat om accuraat en snel doelpunten te detecteren. Bij de detectie van een doelpunt, worden alle elektronische reclameborden op elkaar afgestemd. Het op dat moment vertoonde item geniet dan exclusief alle aandacht. Derhalve wordt voor adverteerders een meerwaarde gecreëerd, met alle voordelen van dien. Het systeem combineert radartechnologie met beeldverwerking. De radars worden gebruikt om de positie van de bal te bepalen. Zodra de bal zich dicht bij het doel bevindt, zal een signaal worden afgeven aan het beeldverwerkingsysteem. Dit systeem zal bepalen of de bal de doellijn is gepasseerd. Maxad heeft onder andere het adviesbureau MaxRadar in het leven geroepen, dat als specialist in radartechnologie het radarsysteem zal ontwerpen. Overige adviesbureaus aangesteld door Maxad zijn MaxSoft en MaxImage, verantwoordelijk voor respectievelijk de software van het radarsysteem en het beeldverwerkingsysteem. In dit rapport zijn de verrichtingen weergegeven van MaxRadar. Er wordt beschreven hoe het ontwerp van de radaropstelling tot stand is gekomen. Tevens zijn de overwegingen weergegeven voor de bepalende onderdelen van een dergelijke opstelling. Het ontwerp van de verschillende onderdelen neemt veel tijd in beslag. Gezien de korte looptijd van het project, is de keuze gemaakt het ontwerpproces van één onderdeel specifiek uit te werken: de microstrip patch-antenne. In dit rapport wordt kort gekeken naar de verschillende methodes die beschikbaar zijn om de bal beter zichtbaar te maken voor de radar. Vervolgens wordt de evaluatie van het gebouwde prototype behandeld. Tot slot wordt een conclusie getrokken over het eindontwerp en er worden aanbevelingen gegeven voor verder onderzoek naar doelpuntendetectiesystemen met radartechnologie. Verschillende radaropstellingen zijn bedacht en geëvalueerd aan de hand van het programma van eisen. Uit de bestudering van de verscheidene opstellingen, is bepaald dat per doel drie radars nodig zijn, hetgeen het totaal aantal radars per stadion op zes brengt. Gekozen is voor de frequency modulated continuous wave (FMCW) radar. FMCW wordt hedendaags veel gebruikt en leent zich uitstekend voor afstandsbepaling met hoge resolutie. Bovendien is de productie van FMCW relatief goedkoop, omdat het ook volop wordt gebruikt in de auto-industrie. Voor de antenne zijn verschillende alternatieven beschikbaar. Deze antennes zijn beoordeeld aan de hand van een aantal specifieke eisen. De conclusie luidt dat microstrip patch-antennes het meest bruikbaar zijn. Deze antenne heeft de vereiste brede bundel. Bovendien zijn patch-antennes goedkoop, robuust en onderhoudsarm. Er zijn een aantal mogelijkheden om de bal beter zichtbaar te maken voor de radar. Een eerste mogelijkheid is om de bal inwendig te bekleden met reflectieverhogende materialen, zoals een laag aluminiumfolie. Uit metingen is gebleken dat deze methode de reflecties van de bal aanzienlijk vergroot. Door het materiaal een bepaald profiel te geven, kan de reflectiviteit nog verder worden verhoogd. Ook kan gebruik worden gemaakt van een verborgen eigenschap van golven, te weten de polarisatie. Tevens bestaat de optie om RFID technologie toe te passen.Electrical Engineering, Mathematics and Computer Scienc
ChildFinder Hardware: Technologiekeuzes, ontwerp en conceptdemonstratie
No full textThis bachelor thesis is written for the bachelorproject 'Where is my baby?'. This is one of the three thesis for the project, describing the technology choices, hardware design and concept demonstration of the ChildFinder. The ChildFinder is device that keeps an eye on children.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
Emulation of a Photovoltaic System with Simulink
No full textNew research on the impact of home batteries, such as the Tesla Powerwall, on the electricity grid needs photovoltaic emulators, enabling to test independent of weather conditions. However, current PV emulators give little flexibility, are hard to implement, or very expensive. Current models are mostly focused on qualitative analysis, and not so much on quantitative analysis, for when one would like to simulate a full day. In this thesis, we describe how we have built a photovoltaic emulator that is digitally controlled by a Simulink model. The model contains the typical characteristics of a PV array and is optimized with Maximum Power Point Tracking (MPPT) and a Buck-Boost converter. The output signals of this model will communicate via the Modbus communication protocol to a programmable AC/DC-converter. This converter will provide a configurable power output to the household grid, simulating realistic day-to-day conditions of a typical PV panel. This enables a flexible and easy to use solution for future research topics like smart-grids and DC-grids.Electrical Engineering, Mathematics and Computer ScienceMicroelectronic
Efficient implementation of the domain-integrated field relations method for quasi-static magnetic fields
No full textAuthor accepted manuscript of the 17th Annual Review of Progress in Applied Computational Electromagnetics, Monterey, pp. 337-344, 19 Mar 2001 → 23 Mar 2001Electrical Engineering, Mathematics and Computer Scienc
The Time-Domain Optical Theorem in Antenna Theory
No full textA special form of the time-domain optical theorem related to a general receiving antenna system is rigorously derived. It is shown that the total energies dissipated in the antenna load and in the antenna system itself can be directly related to the electromagnetic energy of the scattered field and its time-domain far-fieldcharacteristics. A practical implication of the result in optimizing antenna scattering properties with regard to the maximum energy dissipated in the antenna loading is discussed.Accepted Author ManuscriptTera-Hertz Sensin
Signal Integrity in Pulse-train Excited Array Antennas in Time and Space - A Full TD Analysis
No full textSignal integrity in the far-field radiation from pulse-train excited array antennas is studied via full timedomain instruments. The disturbance in the received signal is related to the fidelity factor. At any point in our analysis, the disturbance is evaluated based on a reduced, well defined set of parameters: pulse parameters and pulse repetition rate – temporal dependence, and elementary radiator location – spatial dependence. Their effect is examined by means of illustrative numerical experiments. These results are expedient for enhancing the detectability of the signals radiated by pulse-train excited array antennas, as needed in wireless digital transfer.Accepted author manuscriptEEMS - GeneralTera-Hertz Sensin
A defence of Mr. Garrick, in answer to the letter-writer. With remarks upon plays and players, and the present state of the stage. By a dramatic author [electronic resource].
No full textThe letter-writer = H. W., i.e. Edward Purdon, author of 'A letter to David Garrick, Esq; on opening the Theatre' published 13 October, 1759.Price from imprint: price One-Shilling.Electronic reproduction.English Short Title Catalog,Reproduction of original from British Library
Sunflower array antenna for multi-beam satellite applications
No full textSaving space on board, reducing costs and improving the antenna performances are tasks of outmost importance in the field of satellite communication. In this work it is shown how a non-uniformly spaced, direct radiating array designed according to the so called ‘sunflower’ law is able to satisfy stringent requirements with a reduced number of active chains, all employing amplifiers working at the same, optimised, operation point. The aim of this PhD thesis is to identify several array configurations characterized by a reduced complexity and cost when compared with conventional arrays or to reflector configurations. These arrays must satisfy stringent requirements of a GEOstationary satellite communication mission, especially in terms of a minimum directivity to be guaranteed in several spot beam areas and sidelobe levels to be kept below an assigned value. The dissertation starts with the discussion of the pattern characteristics of regularly spaced array. Since regularly spaced arrays do not allow pattern shaping without making use of an amplitude distribution, non-uniformly spaced arrays are introduced and their pattern behaviour is discussed at length. These arrays are proven to offer the freedom for shaping the pattern according to the imposed requirements and, at the same time, avoid the occurrence of grating lobes. Several innovative techniques for designing this particular class of arrays are proposed and compared. Among them, the sunflower positioning technique is chosen as the best candidate to deterministically design non-uniform planar arrays with really low sidelobe levels and a good rotational symmetry of the radiation patterns. This simple technique is based on the application of two separate laws for finding the radial and angular element positions. The first one comes directly from the relation established in the thesis between the amplitude distribution law and the density distribution one. Regarding the angular positioning law, the concept of optimal angular spreading, inherited from the natural world, is applied to the sunflower array antenna in order to guarantee the sparsity of the element positions both in the radial and angular coordinates.This angular sparsity is achieved by ensuring that each element of the array is placed at a different angular position. The sunflower synthesis technique is then generalized for employing differently sized sub-arrays in the same aperture. Two different options are presented, in which the sub-arrays composing the sunflower array have the same amplitude or the same power. In the first one, the planar aperture is divided into convex cells associated with the spatial locations obtained by means of the sunflower positioning. These cells are then filled with the best fitting (regular) sub-arrays. In this sense, several shapes are experimented with, ranging from circular ones to some that present clear technological advantages. In the latter case, the selected sub-arrays may induce a slight alteration of the rigorous sunflower placement. However, the easier technological implementation makes them the preferred choice for the design of the large planar array that is able to satisfy the satellite mission requirements. In order to physically validate the positioning principle of the sunflower array antenna, a demonstrator at a scaled frequency has been manufactured and measured. Four different sub-arrays are assembled starting from a standard 4x4 square, circularly polarized tile, and their radiation patterns are superimposed in order to compute the total array radiated pattern. Measurements and simulated results are shown to be in very good agreement. The dissertation attests the sunflower placement technique as an innovative, successful, deterministic method for designing large arrays. This technique can be complemented with a modular sub-array design, the combination of the two yielding an effective instrument for implementing highly demanding antennas, such as those required by satellite communication applications.Microwaves Radar and Remote Sensing TechnologyElectrical Engineering, Mathematics and Computer Scienc
Modeling of PV Penetration in Residential Neighborhoods on Aruba
No full textAruba is a small island in the Caribbean. It has 101,484 inhabitants and its main income is tourism. As an island it is dependent on fossil fuel to generate its electric energy. As a result of the increasing oil price, it is attractive to be an island that generates its own electric energy through sustainable generators. This is the reason that the Aruban government made an ambitious plan to make the Aruba a self-sustainable island by 2020. To accomplish this plan, one of the goals that need to be accomplished is, to know what the current status is on integration of Photovoltaic (PV) systems is, and what is needed for in the future for integration more PV systems. To summarized; the main goal of this thesis is to know how many PV systems can be integrated in the current grid without modification and what modification is needed to integrate more PV systems into the grid.Electrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
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