The effect of magnetic islands on ITG turbulence driven transport

In this work, we address the question of the influence of magnetic islands on the perpendicular transport due to steady-state ITG turbulence on the energy transport time scale. We demonstrate that turbulence can cross the separatrix and enhance the perpendicular transport across magnetic islands. As the perpendicular transport in the interior of the island sets the critical island size needed for growth of neoclassical tearing modes, this increased transport leads to a critical island size larger than that predicted from considering collisional conductivities, but smaller than that using anomalous effective conductivities. We find that on Bohm time scales, the turbulence is able to re-establish the temperature gradient across the island for islands widths $w \lesssim \lambda_{turb}$, the turbulence correlation length. The reduction in the island flattening is estimated by comparison with simulations retaining only the perpendicular temperature and no turbulence. At intermediate island widths, comparable to $\lambda_{turb}$, turbulence is able to maintain finite temperature gradients across the island

Perturbative approach to the nonlinear saturation of the tearing mode for any current gradient

Within the traditional frame of reduced MHD, a new rigorous perturbation expansion provides the equation ruling the nonlinear growth and saturation of the tearing mode for any current gradient. The small parameter is the magnetic island width w. For the first time, the final equation displays at once terms of order w ln(1/w) and w which have the same magnitude for practical purposes; two new O(w) terms involve the current gradient. The technique is applicable to the case of an external forcing. The solution for a static forcing is computed explicitly and it exhibits three physical regimes.Comment: 4 pages, submitted to Physical Review Letter

Plasma turbulence simulations with X-points using the flux-coordinate independent approach

In this work, the Flux-Coordinate Independent (FCI) approach to plasma turbulence simulations is formulated for the case of generic, static magnetic fields, including those possessing stochastic field lines. It is then demonstrated that FCI is applicable to nonlinear turbulent problems with and without X-point geometry. In particular, by means of simulations with the FENICIA code, it is shown that the standard features of ITG modes are recovered with reduced toroidal resolution. Finally, ITG turbulence under the influence of a static island is studied on the transport timescale with ITER-like parameters, showing the wide range of applicability of the method

Quantum theory of a polarization phase-gate in an atomic tripod configuration

We present the quantum theory of a polarization phase-gate that can be realized in a sample of ultracold rubidium atoms driven into a tripod configuration. The main advantages of this scheme are in its relative simplicity and inherent symmetry. It is shown that the conditional phase shifts of order $\pi$ can be attained.Comment: X International Conference on Quantum Optics, Minsk, Belaru

Does project portfolio management approach fit smart city management?

Nowadays public administrations have to face many challenges related to Smart City initiatives and must coordinate these projects executing effective Smart City strategies with the adoption of an efficient portfolio management framework. Except for a few aspects, literature about this topic is scarce so this study was carried out as an attempt to evaluate the feasibility of adopting PMI’s Project Portfolio Management methodology to handle Smart City initiatives. A specific survey investigating how much Smart City projects mirror portfolio dynamics has been submitted to experts across the globe and the collected results have been analysed according to our possibilities. Results are twofold: on the one hand, it appears that the Project Portfolio Management approach could be beneficial for managing Smart City project sets, on the other hand, the Project Portfolio Management seems to be a very suitable tool when the Smart City project portfolio is heavily influenced by external stakeholders

Improving Project Estimates at Completion through Progress-Based Performance Factors

From a managerial perspective, project success hinges on estimates at completion as they allow tailoring response actions to cost and schedule overruns. While the literature is moving towards sophisticated approaches, standard methodologies, such as Earned-Value Management (EVM) and Earned Schedule (ES), are barely implemented in certain contexts. Therefore, it is necessary to improve performance forecasting without increasing its difficulty. The objective of this study was twofold. First, to guide modeling and implementing project progress within cost and to schedule Performance Factors (PFs). Second, to test several PFs utilized within EVM and ES formulae to forecast project cost and duration at completion. Progress indicators dynamically adjust the evaluation approach, shifting from neutral to conservative as the project progresses, either physically or temporally. This study compared the performance of the progress-based PFs against EVM and ES standard, combined, and average-based PFs on a dataset of 65 real construction projects, in both cost and duration forecasting. The results show that progress-based PFs provide more accurate, precise, and timely forecasts than other PFs. This study allows practitioners to select one or more of the proposed PFs, or even to develop one, following the guidelines provided, to reflect best their assumptions about the future course of project performance

Cu-catalyzed Si-NWS grown on “carbon paper” as anodes for Li-ion cells

The very high theoretical capacity of the silicon (4200mAh/g more than 10 times larger than graphite), environmental-friendly, abundant and low-cost, makes it a potential candidate to replace graphite in high energy density Li-ion batteries. As a drawback, silicon suffers from huge volume changes (300%) on alloying and dealloying with Li, leading a structural deformation that induces disruption. The use of nanostructured silicon materials has been shown to be an effective way to avoid this mechanical degradation of the active material. In this paper the synthesis of silicon nanowires, grown on a highly porous 3D-like carbon paper substrate by CVD using Cu as the catalyst, is presented. The use of carbon paper allows to achieve remarkable loadings of active material (2-5 mg/cm2) and, consequently, high capacity densities. The silicon electrode was investigated both morphologically and electrochemically. To improve the electrochemical performance various strategies have been carried out. It was observed that a very slow first cycle (C/40), which helps the formation of a stable solid electrolyte interphase on the silicon surface, improves the performance of the cells; nevertheless, their cycle life has been found not fully satisfactory. Morphological analysis of the Si-NWs electrodes before and after cycling showed the presence of a dense silicon layer below the nanowires which could reduce the electrical contact between the active material and the substrate