Observations of How Magnetofluid Turbulence Dissipates at Small Scales

The solar wind is a turbulent magneto fluid that can be studied intensively at multiple scales. Investigations using single spacecraft have revealed much about the properties of the solar wind throughout the heliosphere (from 0.3 AU to 100 AU). More recently, data from multiple spacecraft have provided further details of both the statistical properties of the turbulence and its small-scale structure. In particular, high time resolution magnetic field measurements from the four Cluster spacecrafl have led to the conclusion that at spatial scales of order the proton inertial length and smaller, the turbulence becomes strongly anisotropic and the power in fluctuations that are perpendicular to the (local) magnetic field is measured to be much larger than that in fluctuations that are parallel to the magnetic field. As the spatial scales approach the electron inertial length, the power is almost completely dissipated. Various analysis techniques and theoretical ideas have been put forward to account for the properties of those measurements. The talk will describe the current state of observations, theory and simulations

Adaptive maximum power point tracking using neural networks for a photovoltaic systems according grid

Introduction. This article deals with the optimization of the energy conversion of a grid-connected photovoltaic system. The novelty is to develop an intelligent maximum power point tracking technique using artificial neural network algorithms. Purpose. Intelligent maximum power point tracking technique is developed in order to improve the photovoltaic system performances under the variations of the temperature and irradiation. Methods. This work is to calculate and follow the maximum power point for a photovoltaic system operating according to the artificial intelligence mechanism is and the latter is used an adaptive modified perturbation and observation maximum power point tracking algorithm based on function sign to generate an specify duty cycle applied to DC-DC converter, where we use the feed forward artificial neural network type trained by Levenberg-Marquardt backpropagation. Results. The photovoltaic system that we chose to simulate and apply this intelligent technique on it is a stand-alone photovoltaic system. According to the results obtained from simulation of the photovoltaic system using adaptive modified perturbation and observation – artificial neural network the efficiency and the quality of the production of energy from photovoltaic is increased. Practical value. The proposed algorithm is validated by a dSPACE DS1104 for different operating conditions. All practice results confirm the effectiveness of our proposed algorithm.Вступ. У статті йдеться про оптимізацію перетворення енергії фотоелектричної системи, підключеної до мережі. Новизна полягає у розробці методики інтелектуального відстеження точок максимальної потужності з використанням алгоритмів штучної нейронної мережі. Мета. Методика інтелектуального відстеження точок максимальної потужності розроблена з метою поліпшення характеристик фотоелектричної системи в умовах зміни температури та опромінення. Методи. Робота полягає в обчисленні та відстеженні точки максимальної потужності для фотоелектричної системи, що працює відповідно до механізму штучного інтелекту, і в останній використовується адаптивний модифікований алгоритм збурення та відстеження точок максимальної потужності на основі знаку функції для створення заданого робочого циклу стосовно DC-DC перетворювача, де ми використовуємо штучну нейронну мережу типу «прямої подачі», навчену зворотному розповсюдженню Левенберга-Марквардта. Результати. Фотоелектрична система, яку ми обрали для моделювання та застосування цієї інтелектуальної методики, є автономною фотоелектричною системою. Відповідно до результатів, отриманих при моделюванні фотоелектричної системи з використанням адаптивних модифікованих збурень та спостереження – штучної нейронної мережі, ефективність та якість виробництва енергії з фотоелектричної енергії підвищується. Практична цінність. Запропонований алгоритм перевірено dSPACE DS1104 для різних умов роботи. Усі практичні результати підтверджують ефективність запропонованого нами алгоритму

Scaling of the electron dissipation range of solar wind turbulence

Electron scale solar wind turbulence has attracted great interest in recent years. Clear evidences have been given from the Cluster data that turbulence is not fully dissipated near the proton scale but continues cascading down to the electron scales. However, the scaling of the energy spectra as well as the nature of the plasma modes involved at those small scales are still not fully determined. Here we survey 10 years of the Cluster search-coil magnetometer (SCM) waveforms measured in the solar wind and perform a statistical study of the magnetic energy spectra in the frequency range [$1, 180$]Hz. We show that a large fraction of the spectra exhibit clear breakpoints near the electon gyroscale $\rho_e$, followed by steeper power-law like spectra. We show that the scaling below the electron breakpoint cannot be determined unambiguously due to instrumental limitations that will be discussed in detail. We compare our results to recent ones reported in other studies and discuss their implication on the physical mechanisms and the theoretical modeling of energy dissipation in the SW.Comment: 10 pages, submitte

Time-energy correlations in solar flare occurrence

The existence of time-energy correlations in flare occurrence is still an open and much debated problem. This study addresses the question whether statistically significant correlations are present between energies of successive flares as well as energies and waiting times. We analyze the GOES catalog with a statistical approach based on the comparison of the real catalog with a reshuffled one where energies are decorrelated. This analysis reduces the effect of background activity and is able to reveal the role of obscuration. We show the existence of non-trivial correlations between waiting times and energies, as well as between energies of subsequent flares. More precisely, we find that flares close in time tend to have the second event with large energy. Moreover, after large flares the flaring rate significantly increases, together with the probability of other large flares. Results suggest that correlations between energies and waiting times are a physical property and not an effect of obscuration. These findings could give important information on the mechanisms for energy storage and release in the solar corona

Observations and Interpretation of Magnetofluid Turbulence at Small Scales

High time resolution magnetic field measurements from the four Cluster spacecraft have revealed new features of the properties of magnetofluid turbulence at small spatial scales; perhaps even revealing the approach to the dissipation regime at scales close to the electron inertial length. Various analysis techniques and theoretical ideas have been put forward to account for the properties of those measurements. The talk will describe the current state of observations and theory, and will point out on-going and planned research that will further our understanding of how magnetofluid turbulence dissipates. The observations and theories are directly germane to studies being planned as part of NASA's forthcoming Magnetospheric Multiscale Mission

Spin-coated Tin-doped NiO thin films for third order nonlinear optical applications

A self-made spin-coater was employed to deposit pure and Sn doped nickel oxide thin films on glass substrates. The tin doping impact on the structural, linear and nonlinear optical properties of the spin-coated NiO thin films was studied. The XRD analysis showed that undoped and Sn doped NiO thin films have a cubic structure and are preferentially oriented along the (200) direction. The increase of doping concentration leads to a modification in the values of certain parameters such as the crystallite size and the structural strain as well as affecting the nonlinear optical properties of the doped nickel oxide thin films. The values of the third order nonlinear optical susceptibility, found to be between 2.25 × 10−21 m2/V2 and 3.13 × 10−21 m2/V2, were obtained and analyzed depending on the concentration of the doping

Amplified spontaneous emission in the spiropyran-biopolymer based system

Amplified spontaneous emission (ASE) phenomenon in the 6-nitro-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indolin] organic dye dispersed in a solid matrix has been observed. The biopolymer system deoxyribonucleic acid blended with cationic surfactant molecule cetyltrimethyl-ammonium chloride served as a matrix. ASE appeared under sample excitation by UV light pulses (λ=355 nm) coming from nanosecond or picosecond neodymium doped yttrium aluminum garnet lasers and has been reinforced with green (λ=532 nm) light excitation followed UV light pulse. The ASE characteristics in function of different excitation pulse energies as well as signal gain were measured

Comparison of structural, morphological, linear and nonlinear optical properties of NiO thin films elaborated by Spin-Coating and Spray Pyrolysis

The paper reports on a comparative study of nickel oxide thin films prepared via two different elaboration methods spin-coating and spray pyrolysis. The structure and the surface topography of the NiO thin films have been studied by X-ray diffraction and the atomic force microscope. The optical properties of the deposited films were characterized with the analysis of the experimentally recorded optical transmittance data in the spectral wavelength range of 300–850 nm, via a JENWAY6715 UV–vis spectrophotometer. To complete the comparison, the third order nonlinear optical susceptibility was determined from the third harmonic generation experiment, which in turn were explored by the rotational Maker fringe technique using the beam of Nd:YAG laser at 1064 nm in picoseconds regime. The present work is aimed to exhibit the influence of the elaboration method on the physical properties through analyzing the obtained experimental results