Self impedance matched Hall-effect gyrators and circulators

We present a model study of an alternative implementation of a two-port Hall-effect microwave gyrator. Our set-up involves three electrodes, one of which acts as a common ground for the others. Based on the capacitive-coupling model of Viola and DiVincenzo, we analyze the performance of the device and we predict that ideal gyration can be achieved at specific frequencies. Interestingly, the impedance of the three-terminal gyrator can be made arbitrarily small for certain coupling strengths, so that no auxiliary impedance matching is required. Although the bandwidth of the device shrinks as the impedance decreases, it can be improved by reducing the magnetic field; it can be realistically increased up to $150 \mathrm{MHz}$ at $50\mathrm{\Omega}$ by working at filling factor $\nu=10$. We examine also the effects of the parasitic capacitive coupling between electrodes and we find that, although in general they strongly influence the response of device, their effect is negligible at low impedance. Finally, we analyze an interferometric implementation of a circulator, which incorporates the gyrator in a Mach-Zender-like construction. Perfect circulation in both directions can be achieved, depending on frequency and on the details of the interferometer

Diseño sostenible – creando un paisaje urbano contemporáneo

Hoy en día tendemos a regresar al pasado a nuestra relación raíz con la naturaleza. Preservar el medio ambiente natural a través de diseño sostenible se ha hecho evidente. Los estudios sobre la creación de entornos sanos construidos para los humanos demostraron que el contacto con la naturaleza es inevitable. Así pues hay una tendencia que observa el introducir componentes de medio ambiente natural como elementos de composición espacial. A pesar de haberse reinventado debido a las posibilidades tecnológicas y los requisitos en términos de introducir sostenibilidad, la sustancia original permanece igual: vegetación, suelo, agua, iluminación natural, etc. El resultado es una nueva fisionomía de la arquitectura – el fenómeno de tallar el terreno, mezclándose con el paisaje del entorno o el entorno natural penetrante. La nueva relación arquitectura versus naturaleza se establece e introduce nuevos valores estéticos en el espacio arquitectónico y urbano. Este trabajo describe ejemplos de elementos naturales en composiciones arquitectónicas y urbanas; su papel sostenible y compositivo al crear un nuevo paisaje urbano en las ciudades europeas

RFI mitigation with phase-only adaptive beamforming

Connected radio interferometers are sometimes used in the tied-array mode: signals from antenna elements are coherently added and the sum signal applied to a VLBI backend or pulsar processing machine. Usually there is no computer-controlled amplitude weighting in the existing radio interferometer facilities. Radio frequency interference (RFI) mitigation with phase-only adaptive beamforming is proposed for this mode of observation. Small phase perturbations are introduced in each of the antenna's signal. The values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and RFI signals suppressed. An evolutionary programming algorithm is used for this task. Computer simulations, made for both one-dimensional and two-dimensional array set-ups, show considerable suppression of RFI and acceptable changes to the main array beam in the radio source direction.Comment: 7 pages, 11 figure

Biodiversity and Ecosystem Health of the Aldabra Group, Southern Seychelles: Scientific Report to the Government of Seychelles.

National Geographic's Pristine Seas project, in collaboration with the government of the Seychelles, the Island Conservation Society (ICS), the Seychelles Islands Foundation (SIF), and the Waitt Foundation, conducted an expedition to explore the poorly known marine environment around these islands. The goals were to assess the biodiversity of the nearshore marine environment and to survey the largely unknown deep sea realm. The data collected contribute to the marine spatial planning of the Seychelles, in particular the creation of large marine reserves

Neural networks as surrogate models for nonlinear, transient aerodynamics within an aeroelastic coupling-scheme in the time domain

In this paper the creation of a nonlinear, transient surrogate model is described that can be used within an aeroelastic coupling-scheme in the transonic range. The method is based on the theory of artifical neural networks as well as the autoregressive moving average method (ARMA). It can be shown that the method is able to approximate the nonlinear aeroelastic behaviour of the NLR7301 airfoil. Also limit cycle oscillations can be approximated with acceptable accuracy

Realization of an Economical Polymer Optical Fiber Demultiplexer

Polymer Optical Fiber (POF) can be and are being used in various fields of applications. Two of the main fields are the automotive and the home entertainment sector. The POF can be applied in several different optical communication systems as automotive multi-media busses or in-house Ethernet systems. The requirements of bandwidth are increasing very fast in these sectors and therefore solutions that satisfy these demands are of high actuality. One solution is to use the wavelength division multiplexing (WDM) technique. Here, several different wavelengths can carry information over one POF fiber. All wavelengths that are transmitted over the fiber, must be separated at the receiver to regain and redirect the information channels. These separators are so-called Demultiplexers. There are several systems available on the market, which are all afflicted with certain disadvantages. But all these solutions have one main disadvantage, they are all too expensive for most of the applications mentioned above. So the goal of this study is to develop an economical Demultiplexer for WDM transmission over POF. The main idea is to separate the chromatic light in its monochromatic components with the help of a prism with low reciprocal dispersive power. The prism and the other assemblies, which are needed to adjust the optical path, should be manufactured in injection molding technique. This manufacturing technique is a very simple and economical way to produce a mass production applicable Demultiplexer for POF.Comment: 2006 International Students and Young Scientists Workshop "Photonics and Microsystems

CNOT and Bell-state analysis in the weak-coupling cavity QED regime

We propose an interface between the spin of a photon and the spin of an electron confined in a quantum dot embedded in a microcavity operating in the weak coupling regime. This interface, based on spin selective photon reflection from the cavity, can be used to construct a CNOT gate, a multi-photon entangler and a photonic Bell-state analyzer. Finally, we analyze experimental feasibility, concluding that the schemes can be implemented with current technology.Comment: 4 pages, 2 figure