Lightning radiation field due to channel tortuosity and branching

The effect of lightning channel branching on the temporal waveform of the radiated fields of the return stroke is modeled. The effect of branching is isolated, and compared to the effect of tortuosity of an unbranched channe

Definition for polarization P and magnetization M fully consistent with Maxwell's equations

Dealing with the project of metamaterials scientists often have to design circuit elements at a subwavelength (or ``microscopic'') scale. At that scale, they use the set of Maxwell's equations in free-space, and neither permittivity ε nor permeability μ are formally defined. However, the objective is to use the unit cells in order to build a bulk material with some desired ``macroscopic'' properties. At that scale the set of Maxwell's equations in matter is adopted. To pass from one approach to the other is not obvious. In this paper we analyse the classic definitions of polarization P and magnetization M, highlighting their limits. Then we propose a definition for P and M fully consistent with Maxwell's equations at any scale

Optimization of a dual ring antenna by means of artifcial neural network

In literature, heuristic algorithms have been successfully applied to a number of electromagnetic problems. The associated cost functions are commonly linked to full-wave analysis, leading to complexity and high computational expense. Arti-cial Neural Network is one of the most e®ective biological inspired techniques. In this article, an e±cient surrogate model is trained to replace the full-wave analysis in optimizing the bandwidth of microstrip antenna. The numerical comparison between ANN substitution model and full-wave characterization shows signi-cant improvements in time convergence and computational cost. To verify the robustness of this approach, all these concepts are integrated into a case study represented by a rectangular ring antenna with proximity-coupled feed antenna

Disegno e Camera Lucida nel Carnet de voyage.

Da sempre il viaggiatore disegna. Annota graficamente ciò che osserva per poterlo assimilare attraverso la traduzione in segni, estrapolando quei particolari che lo portano a sintetizzare la descrizione del reale. Gli strumenti del disegnatore in viaggio sono elementi che condizionano tempi e modi di realizzazione portando i diversi autori a scegliere modalità espressive nel rispetto delle differenti finalità. Nell'ottocento, le evoluzioni della Camera Obscura (la Camera Lucida e successivamente la Fotografia), in modo diverso, hanno portato a una velocizzazione della rappresentazione del reale. Proprio nell'era della fotografia digitale, che non obbliga l'autore all'analisi, la riscoperta di questo piccolo strumento ottico impone una relazione biunivoca tra conoscenza e sintesi attraverso il disegno. L'esperienza diretta ha portato a ridefinire i tempi di esecuzione delle vedute, dilatando quelli di progettazione e riducendo quelli della realizzazione. Operare sotto la guida dello strumento permette di mantenere rapporti proporzionali e prospettici, basi certe per la successiva implementazione con la vestizione grafica. Nella dimensione del "carnet de voyage" dall'800 ad oggi, tale ridefinizione ha mostrato potenzialità che possono essere nuovi, attuali, veicoli di conoscenza.The traveler has always drawn. Graphically marking what he looks at, in order to assimilate it through a translation into signs, extrapolating those details that allow him to synthesize the description of reality. The tools of the drawer on the road affect the time and the manner of realization, driving the different authors to choose different modes of expression with respect to their different purposes.In the nineteenth century, the invention of the Camera Lucida and afterwards of the Photography (both evolutions of the Camera Obscura), in a different ways have led to a speeding up of the representationof reality. In the era of digital photography, which does not require the author to synthesize, the rediscovery of the Camera Lucida imposes a two-way relationship between knowledge and discretization, through ther process of drawing. Direct experience has led us to redefine the executiontimes of views, expanding the design part and reducing the production one. To operate under theguidance of the tool allows you to maintain proportional relationships and prospective, excellent basesfor a later improvement by a graphic dressing.In the dimension of the "carnet de voyage" from '800 to today, this redefinition has shown potentialthat may be new, current, vehicles of knowledge

Evolutionary techniques for sensor networks energy optimization in marine environmental monitoring

The sustainable management of coastal and offshore ecosystems, such as for example coral reef environments, requires the collection of accurate data across various temporal and spatial scales. Accordingly, monitoring systems are seen as central tools for ecosystem-based environmental management, helping on one hand to accurately describe the water column and substrate biophysical properties, and on the other hand to correctly steer sustainability policies by providing timely and useful information to decision-makers. A robust and intelligent sensor network that can adjust and be adapted to different and changing environmental or management demands would revolutionize our capacity to wove accurately model, predict, and manage human impacts on our coastal, marine, and other similar environments. In this paper advanced evolutionary techniques are applied to optimize the design of an innovative energy harvesting device for marine applications. The authors implement an enhanced technique in order to exploit in the most effective way the uniqueness and peculiarities of two classical optimization approaches, Particle Swarm Optimization and Genetic Algorithms. Here, this hybrid procedure is applied to a power buoy designed for marine environmental monitoring applications in order to optimize the recovered energy from sea-wave, by selecting the optimal device configuration

Advanced monitoring systems for biological applications in marine environments

The increasing need to manage complex environmental problems demands a new approach and new technologies to provide the information required at a spatial and temporal resolution appropriate to the scales at which the biological processes occur. In particular sensor networks, now quite popular on land, still poses many difficult problems in underwater environments. In this context, it is necessary to develop an autonomous monitoring system that can be remotely interrogated and directed to address unforeseen or expected changes in such environmental conditions. This system, at the highest level, aims to provide a framework for combining observations from a wide range of different in-situ sensors and remote sensing instruments, with a long-term plan for how the network of sensing modalities will continue to evolve in terms of sensing modality, geographic location, and spatial and temporal density. The advances in sensor technology and digital electronics have made it possible to produce large amount of small tag-like sensors which integrate sensing, processing, and communication capabilities together and form an autonomous entity. To successfully use this kind of systems in under water environments2 , it becomes necessary to optimize the network lifetime and face the relative hindrances that such a field imposes, especially in terms of underwater information exchange