Synthesis methods of array antenna excitation laws

Standard numerical optimization methods become very computational time consuming when dealing with synthesis of array antenna excitation laws, especially when number of elements exceeds a few tenths. Array antenna designer needs a fast and efficient synthesis tool, since the design phase implies several reoptimizations within the definition phase, in order to satisfy tradeoffs on antagonistic requirements : performances, size, cost,… We propose the use of an efficient, from the computational time point of view, and secured, from the convergence point of view, synthesis method illustrated by two examples. The optimized solution satisfies a sta-tionarity condition, which leads to steady solutions in frequency but also with regard to errors (manufacturing, …). Based on analytical calculus performed before any numerical resolution and together with the use of fast Fourier transform algorithms, this method leads to reduced optimization times (in the order of a minute) for arrays of some tenths up to some hundred feeds, computations being performed on a pc. Two theoretical applications are presented and for each of them a computed example is also shown; moreover possible extensions are considered.     

Historical review of the concept of anhedonia

During the last decades, the term "anhedonia", conceptualized as a incapacity to experience pleasure, have become associated with conditions as different as schizophrenia and depression. This paper deals with the conceptual and historial frames in which anhedonia was first constructed, and shows that the sources for the current fuzziness of this concept include neglect of the fact that anhedonia is conceptually parasitical upon the notion of pleasure, that it has been rather superficially conceptualized as the reduction or abolition in a "putative" function which itself is unlikely to be unitary in nature, and that it has never been quite specified whether the mechanism concerns a deficit in brain signal or not.     

Three-dimensional space-vector modulation algorithm for four-leg multilevel converters using abc coordinates

In this paper, a novel three-dimensional (3-D) space-vector algorithm for four-leg multilevel converters is presented. It can be applied to active power filters or neutral-current compensator applications for mitigating harmonics and zero-sequence components using abc coordinates (referred from now on this paper as natural coordinates). This technique greatly simplifies the selection of the 3-D region where a given voltage vector is supposed to be found. Compared to a three-level modulation algorithm for three-leg multilevel converters, this algorithm does not increase its complexity and the calculations of the active vectors with the corresponding switching time that generate the reference voltage vector. In addition, the low-computational cost of the proposed algorithm is always the same and it is independent of the number of levels of the converter.     

Personal Fabrication: Fab Labs as Platforms for Citizen-Based Innovation, from Microcontrollers to Cities

The ??digital fabrication?? revolution being lived today, both in knowledge creation and in technological developments will become more than a simple formal exploration in architecture and design, or a set of tools exclusive to advanced industries. New tools and processes are becoming more accessible to the masses and are being shared all over the world through Internet platforms, with an open source philosophy, both in software and hardware. The collective mind that is being empowered everyday will define the future of production in the life of mankind and its relation with the environment. The role of architects, engineers, designers and many other professionals, will be reshaped and reconfigured to fit into new models of production and creation. These will need to be supported by new manufacturing platforms, knowledge generating and sharing know-how.     

Effect of Cu by Co substitution on Ca3Co4O9 thermoelectric ceramics

Ca₃Co_4?xCu_xO₉ polycrystalline thermoelectric ceramics with small amounts of Cu have been synthesized by the classical solid state method. X-ray diffraction data have shown that all the Cu has been incorporated into the Ca₃Co₄O₉ structure and no Cu-containing secondary phases have been produced. Apparent density measurements have shown that all samples are very similar, with densities around 75 % of the theoretical one. Electrical resistivity decreases when Cu content increases until x = 0.03 while Seebeck coefficient remains practically constant for all samples. The improvement in resistivity leads to higher power factor values than the obtained for the undoped samples.     

Environmental Degradation Effect on the Properties of Bi-2212 Highly Textured Rods

It is well know that H₂O and CO₂ (both present in the atmosphere) can react chemically with BSCCO superconductors, especially with the alkaline–earth cations, producing chemical degradation and reducing their performances. In this work, Bi-2212 highly textured rods were grown from the melt through a laser floating zone melting technique. In order to determine the influence of H₂O and CO₂ on these bulk textured samples, they were immersed in distilled water and in CO₂ saturated water. The evolution of the electrical and mechanical properties of these rods was determined as a function of the immersion time in both media and compared with their initial properties. It has been found that performance degradation was higher in distilled water than in CO₂ saturated one. Nevertheless, in any case, the degradation has been found to be not very important.