A fractal antenna is an antenna that uses a fractal, self-similar design to maximize the effective length, or increase the perimeter, of material that can receive or transmit electromagnetic radiation within a given total surface area or volume. Such fractal antennas are referred to as multilevel and space filling curves, but the key aspect lies in their repetition of a motif over two or more scale sizes, or "iterations". For this reason, fractal antennas are compact, multiband or wideband, have useful applications in cellular telephone and microwave communications. A fractal antenna's response differs markedly from traditional antenna designs, in that it is capable of operating with good-to-excellent performance at many different frequencies simultaneously. Standard antennas have to be "cut" for the frequency for which they are to be used—and thus the standard antennas only work well at that frequency. In addition the fractal nature of the antenna shrinks its size, without the use of any components, such as inductors or capacitors.
The first fractal "antennas" were, in fact, fractal "arrays", with fractal arrangements of antenna elements, not recognized as having self-similarity as their attribute. Log-periodic antennas are arrays, around since the 1950s, they are a common form used in TV antennas, are arrow-head in shape. Antenna elements made from self-similar shapes were first created by Nathan Cohen a professor at Boston University, starting in 1988. Cohen's efforts with a variety of fractal antenna designs were first published in 1995. Cohen's publication marked the inaugural scientific publication on fractal antennas. Many fractal element antennas use the fractal structure as a virtual combination of capacitors and inductors; this makes the antenna so that it has many different resonances which can be chosen and adjusted by choosing the proper fractal design. This complexity arises because the current on the structure has a complex arrangement caused by the inductance and self capacitance. In general, although their effective electrical length is longer, the fractal element antennas are themselves physically smaller, again due to this reactive loading.
Thus fractal element antennas are shrunken compared to conventional designs, do not need additional components, assuming the structure happens to have the desired resonant input impedance. In general the fractal dimension of a fractal antenna is a poor predictor of its performance and application. Not all fractal antennas set of applications. Computer search methods and antenna simulations are used to identify which fractal antenna designs best meet the need of the application. Studies during the 2000s showed advantages of the fractal element technology in real-life applications, such as RFID and cell phones. Fractals have been used in antennas since 1988and their advantages are good multiband performance, wide bandwidth, small area and that reference showed that the gain with small size results from constructive interference with multiple current maxima, afforded by the electrically long structure in a small area; some researchers have disputed. Steven R. Best in 2003 observed "that antenna geometry alone, fractal or otherwise, does not uniquely determine the electromagnetic properties of the small antenna".
In 2011, Robert C. Hansen and Robert E. Collin reviewed many papers on fractal antennas and concluded that they offer no advantage over fat dipoles, loaded dipoles, or simple loops, that nonfractals are always better. Balanis reported on several fractal antennas and found them equivalent in performance to the electrically small antennas they were compared to. Log periodics, a form of fractal antenna, have their electromagnetic characteristics uniquely determined by geometry, via an opening angle. A different and useful attribute of some fractal element antennas is their self-scaling aspect. In 1957, V. H. Rumsey presented results that angle-defined scaling was one of the underlying requirements to make antennas "invariant" at a number, or range of, frequencies. Work by Y. Mushiake in Japan starting in 1948 demonstrated similar results of frequency independent antennas having self-complementarity, it was believed that antennas had to be defined by angles for this to be true, but in 1999 it was discovered that self-similarity was one of the underlying requirements to make antennas frequency and bandwidth invariant.
In other words, the self-similar aspect was the underlying requirement, along with origin symmetry, for frequency'independence'. Angle-defined antennas are self-similar, but other self-similar antennas are frequency independent although not angle-defined; this analysis, based on Maxwell's equations, showed fractal antennas offer a closed-form and unique insight into a key aspect of electromagnetic phenomena. To wit: the invariance property of Maxwell's equations; this is now known as the HCR Principle. Mushiake's earlier work on self complementarity was shown to be limited to impedance smoothness, as expected from Babinet's Principle, but not frequency invariance. In addition to their use as antennas, fractals have found application in other antenna system components including loads and ground planes. Fractal inductors and fractal tuned circuits were discovered and invented with fractal element antennas. An emerging example of such is in metamaterials. A recent invention demonstrates using close-packed fractal resonators to make the first wideband metamaterial invisibility cl
Walk the Plank are a British group of artists, theatre makers and event engineers who specialise in outdoor arts/theatre, touring performance and pyrotechnics. Their shows are on land and on water and mix performance, lighting, visual images and fireworks; the company was established by John Wassell and Liz Pugh in 1991, who identified a niche market for a touring theatre ship, other aquatic shows on the waterways. The company's work began when the pair purchased the MV Fitzcarraldo; the company's work has now extended far beyond the ship and they work on delivering shows and events, varying in scale from intimate to epic. Walk the Plank have produced work for Toronto’s Wintercity Festival, Singapore Festival, Euro 2004, Tall Ships 2005, Sir Paul McCartney, the Commonwealth Games, as well as multiple city and local councils, their most well known credit are the opening and closing ceremonies for Liverpool's Capital of Culture celebrations. Their administrative base is in Salford, Greater Manchester and they have workshop facilities in Ramsbottom and Rawtenstall.
Their work involves community engagement and they are known for scheduling and leading participation elements which fit the context of the event they are organising. The company's Senior Management Team are trusted advisers in the areas of outdoor arts and cultural events; the Fitzcarraldo was built in 1971 in Norway for TFDS as the MV Bjarkøj. She was 20 years a general cargo and passenger ferry working the islands around Tromsø in north Norway. In 2000,'s co-production of "Moby Dick" won Best Fringe Production at the Manchester Evening News Theatre Awards. Jim Burke won the Best New Play award for this adaptation. In 2003 the ship went on a national tour to 19 ports with a stage adaption of Twenty Thousand Leagues under the Sea, to positive reviews. At first the audience sits on the quayside, the Fitzcarraldo represents the Abraham Lincoln. Due to prohibitive expenses the MV Fitzcarraldo was sold in 2010 to Dutch owners who plan to turn it into a floating nightspot. Walk the Plank continue to focus on delivering large scale outdoor events, creating touring performances and providing pyrotechnics and firework displays to both public sector and private corporate organisations.
Gordon College of Education is a teachers college in Haifa, Israel. Gordon College was established in Haifa in 1953, merging the Teacher’s Seminary of the Labor Movement with the Teacher’s Seminary of the Hebrew Reali School of Haifa. From its foundation, it has focused on the development of teaching skills and furthered Zionist and humanistic values. From 1953 until 1995, Gordon College was accredited to certify teachers. In 1995, it received academic accreditation to grant the Bachelor of Education Degree. Gordon College is a center of teacher’s enrichment programs for the Ministry of Education of Northern Israel; the school has a teaching staff of 200, ranging from full professors to lecturers, a student body of over 1,600. Education in Israel Official website