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Conservation laws are among the most fundamental geometric properties of a given partial differential equation. However, standard finite difference approximations rarely preserve more than a single conservation law. A novel symbolic-numerical approach, introduced in [1], exploits the fact that divergences belong to the kernel of the Euler operator to construct schemes that preserve multiple conservation laws. However, this approach is limited by the complexity of the symbolic computations, whose cost is high even when the nonlinearity in the PDE is only quadratic. Some key simplifications, making the symbolic computations tractable, have been introduced in [2]. We apply this simplified strategy to the modified Korteweg-de Vries equation, having a cubic nonlinearity, to construct new bespoke finite-difference schemes that preserve the local conservation laws of the mass and of the energy.

Multilayer Graphene (MLG), a nanoparticle with a specific surface of BET = 250 m2/g and thus made of only approximately 10 graphene sheets, is proposed as a nanofiller for rubbers. When homogenously dispersed, it works at low loadings enabling the replacement of carbon black (CB), increase in efficiency, or reduction in filler concentration. Actually the appropriate preparation yielded nanocomposites in which just 3 phr are sufficient to significantly improve the rheological, curing and mechanical properties of different rubbers, as shown for Chlorine-Isobutylene-Isoprene Rubber (CIIR), Nitrile-Butadiene Rubber (NBR), Natural Rubber (NR), and Styrene-Butadiene Rubber (SBR). A mere 3 phr of MLG tripled the Young’s modulus of CIIR, an effect equivalent to 20 phr of carbon black. Similar equivalents are observed for MLG/CB mixtures. MLG reduces gas permeability, increases thermal and electrical conductivities, and retards fire behavior. The later shown by the reduction in heat release rate in the cone calorimeter. The higher the nanofiller concentration is (3 phr, 5 phr, and 10 phr was investigated), the greater the improvement in the properties of the nanocomposites. Moreover, the MLG nanocomposites improve stability of mechanical properties against weathering. An increase in UV-absorption as well as a pronounced radical scavenging are proposed and were proved experimentally. To sum up, MLG is interesting as a multifunctional nanofiller and seems to be quite ready for rubber development.

The family of EQUIP (Energy and QUadratic Invariants Preserving) methods for Hamiltonian systems is here recasted in the framework of Line Integral Methods, in order to provide a more efficient discrete problem.

The numerical solution of Hamiltonian PDEs has been the subject of many investigations in the last years, specially concerning the use of multi-symplectic methods. We shall here be concerned with the use of energy-conserving methods in the HBVMs class, when a spectral space discretization is considered.

In this paper we show that energy conserving methods, in particular those in the class of Hamiltonian Boundary Value Methods, can be conveniently used for the numerical solution of Hamiltonian Partial Differential Equations, after a suitable space semi-discretization.

We here investigate the efficient implementation of the energy-conserving methods named Hamiltonian Boundary Value Methods (HBVMs) recently introduced for the numerical solution of Hamiltonian problems. In this note, we describe an iterative procedure, based on a triangular splitting, for solving the generated discrete problems, when the problem at hand is separable., Comment: 4 pages

The recent finding on the effect of a small bias in Sprott-like systems, i.e., the stabilization of the unstable equilibrium point through the addition of a small bias [1], paves the way to efficient methods for chaos control in such systems. In this work, we investigate the control of one of such systems both in the ideal case of absence of noise and in the presence of noise. We then propose an experimental setup for the experimental verification of the introduced method.

A Brain Computer Interface (BCI) system processes and translates neuronal signals, that mainly comes from EEG instruments, into commands for controlling electronic devices. This system can allow people with motor disabilities to control external devices through the real‐time modulation of their brain waves. In this context an EEG‐based BCI system that allows creative luminous artistic representations is here presented. The system that has been designed and realized in our laboratory interfaces the BCI2000 platform performing real‐time analysis of EEG signals with a couple of moving luminescent twin robots. Experiments are also presented.

In this paper, pinning control in a system of moving agents (each one associated to a chaotic dynamical system) has been investigated. In particular, we have studied and compared two different strategies for pinning control and discussed the not trivial relation between synchronization and control of the chaotic agents. Our results show how system parameters like agent density are critical in order to reach a synchronous behavior of the agents as well as to reach global control of the system by only pinning a reduced set of agents.

In this work, the electronic implementation of the Bouali’s equations exhibiting a rich repertoire of nonlinear dynamical phenomena is introduced. The robust plug and play chaotic circuit is designed to be easily realized using standard components in a rigorous, fast and inexpensive way. We find that experimental results display periodicity, bifurcations and chaos that match with high accuracy the corresponding theoretical values.

Post T Tauri stars (PTTS) are late-type stars in the age range between 10 and 100 Myr filling the gap between T Tauri (TTs) and zero-age: main sequence phases. This period of evolution remains ambiguous and until now different studies of young stars have failed to find the numbers of PTTS that are expected. In the last years, some PTTS have been identified among the X-ray detected pre-main sequence stars in some star-forming regions. More recently, additional PTTS have been identified in young associations and moving groups (β Pic, TW Hya, Tucana/Horologium, and the AB Dor). However, many isolated PTTS still remain undiscovered. In this contribution, we compiled the PTTS previously identified in the literature, and identified new candidates using the information provided by the high resolution spectra obtained during our surveys of late-type stars possible members to young moving groups, FGK stars in the solar neighborhood, and RasTyc sample. To identify PTTS we applied an age-oriented definition using relative age indicators (Li abundance, chromospheric and coronal emission and the kinematics) as well as color-magnitude diagrams and pre-main sequence isochrones.

We present the work in progress of a study based on photometric and spectroscopic observations of young Weak-line T Tauri and Post T Tauri stars just attiving on the Zero Age Main Sequence. This study is part of a project based on high-resolution spectra obtained with FOCES@CAHA (Spain) and SARG@TNG (Spain) and contemporaneous photometry performed at Catania (Italy) and Ege (Turkey) observatories. The main aim is to investigate the topology of magnetic active regions at photospheric and chromospheric levels in young single stars. Since our targets are slow rotators (vsini < 25 km/s), corresponding to rotation periods larger than about 2 days, we are able to apply the spectroscopic technique based on line-depth ratio for the measure of the photospheric temperature modulation. These stars, possible members of Stellar Kinematic Groups, display emission cores in the CaII H&K and IRT lines, as well as a conspicuous filling-in of the Halpha core. Moreover, we detect absorption of the HeI-D3 line, coming from the upper chromospheric layers, derive the lithium abundance (age indicator), and measure the rotational and radial velocities. We find a clear rotational modulation, due to photospheric spots, both in the light and the temperature curves. The Halpha and the CaII-IRT emissions display a fair variation correlated with the rotation. Finally, we are developing a spot/plage model to reproduce the data and derive the spot parameters (namely, filling factor and temperature) and to recover information about the chromospheric inhomogeneities (flux contrast and filling factor). This study is very important to explore the correlations between global stellar parameters (e.g., surface gravity, effective temperature) and spot/plage characteristics in stars with different activity level and evolutionary stage., 4 pages, 4 figures, poster paper presented at the Cool Stars 15 (St. Andrews, Scotland), to be published in the Conference Proceedings Series of the American Institute of Physics (AIP)

Complex systems made of nonlinear interacting cells are gaining ever and ever interest. An universal environment for the study these systems should provide to the user the possibility of defining the dynamics of the cells as well as the connections among them in a simple and flexible way. In this paper the main characteristics of E∧3, an universal emulator of complex systems, are discussed. This simulator is based on the paradigm of Cellular Nonlinear Network and makes use of parallel computing allowing to considerably extend the size of the simulated system. Each cell is conceived as a nth‐order dynamical system. Moreover, numerical results obtained by emulating a complex system made of a large number (more than 500000) of interacting chaotic units arranged in a 3D lattice are presented. These simulations show an emerging result: organized forms and structure arise from the dynamic evolution of such systems.

In this paper the possibility of observing chaotic behaviour in an electronic circuit including a nonlinear ferroelectrics has been investigated. The ferroelectrics constitutes the medium interposed between the two plates of a capacitor, and is obtained by successive vapour deposition of Strontium, Tantalum and Bismuth on Platinum substrates in small areas. The device is characterized by a nonlinear hysteretic behaviour observed by estimating the output voltage by using a Sawyer‐Tower configuration. Different circuits showing chaos and based on hysteretic behaviour of the nonlinearities have been reported in literature. In particular, in the circuit reported in [1] the nonlinearity consists of a piecewise linear resistor, only the two tracts with positive slope are effectively involved in the dynamics and an hysteretic behaviour switching between these two linear segments of the nonlinearity can be addressed as responsible of the emergence of iperchaos in the circuit. Starting from the chaos generator rep...

In this paper the design of a motor map to control a chaotic system is presented. A feedback entrainment scheme is adopted: a system with different parameters is used to generate the reference trajectory for the chaotic system to be controlled, while the motor map provides the appropriate gain value of the feedback signal. As input of the motor map the state of the system to be controlled is considered. The motor map based adaptive controller offers high performances, specially in the case when the reference trajectory is switched into another one. In this case, a specialization of the neurons constituting the motor map is observed: while a group of neurons learns the appropriate control law for a reference trajectory, another group specializes itself to control the system when the other trajectory is used as reference. Moreover, a discrete components hardware implementation of the motor map has been realized.

The passage of cosmic rays has been observed to excite mechanical vibrations in the resonant gravitational wave detector NAUTILUS operating at temperature of 100 mK. A very significant correlation (more than ten standard deviations) is found.

Searching for patterns originating from continuous signals in time-frequency diagrams-such diagrams are produced by the very first states of a hierarchical procedure which are described in [2]—is the issue that we shall address in this presentation. We shall outline the main features of a strategy based on the use of the Hough transform by presenting the concept with an easy example and then illustrating the way we will apply it to the specific continuous gravitational wave signal search.

The effects of nuclear radiation and high temperature environments must be fully known and understood for the electronic components and materials used in both the Power Conditioning and Control subsystem and the reactor Instrumentation and Control subsystem of future high capacity nuclear space power systems. This knowledge is required by the designer of these subsystems in order to develop highly reliable, long-life power systems for future NASA missions. A review and summary of the experimental results obtained for the electronic components and materials investigated under the power management element of the Civilian Space Technology Initiative (CSTI) high capacity power project are presented: (1) neutron, gamma ray, and temperature effects on power semiconductor switches, (2) temperature and frequency effects on soft magnetic materials; and (3) temperature effects on rare earth permanent magnets.

The electrical and switching characteristics of high power semiconductor switches subjected to high levels of neutron fluences and gamma doses must be known by the designer of the power conditioning, control and transmission subsystem of space nuclear power systems. Location and the allowable shielding mass budget will determine the level of radiation tolerance required by the switches to meet performance and reliability requirements. Neutron and gamma ray interactions with semiconductor materials and how these interactions affect switch performance are briefly discussed. The effects of post‐irradiation thermal anneals at 300 K and up to 425 K for NPN Bipolar Junction Transistors (BJTs), N‐channel Metal‐Oxide‐Semiconductor Field Effect Transistors (MOSFETs), and N‐channel Static Induction Transistors (SITs) are discussed in terms of recovery of degraded electrical and switching parameters caused by either neutron or gamma irradiation. The important experimental results from these annealing tests show that BJTs have very good recovery to leakage current degradation but poor recovery to current gain degradation; MOSFETs show some recovery in gate‐source threshold voltage degradation but no significant recovery in drain‐source on‐resistance degradation; and likewise, SITs show no significant recovery in drain‐source on‐resistance degradation.