MEGAPOLI: concept of multi-scale modelling of megacity impact on air quality and climate

The EU FP7 Project MEGAPOLI: "Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation" (http://megapoli.info) brings together leading European research groups, state-of-the-art scientific tools and key players from non-European countries to investigate the interactions among megacities, air quality and climate. MEGAPOLI bridges the spatial and temporal scales that connect local emissions, air quality and weather with global atmospheric chemistry and climate. The suggested concept of multi-scale integrated modelling of megacity impact on air quality and climate and vice versa is discussed in the paper. It requires considering different spatial and temporal dimensions: time scales from seconds and hours (to understand the interaction mechanisms) up to years and decades (to consider the climate effects); spatial resolutions: with model down- and up-scaling from street- to global-scale; and two-way interactions between meteorological and chemical processes

The IntCal20 Northern Hemisphere radiocarbon age calibration curve (0-55 cal kBP)

Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals

Modeling and optimization of a tubular generator for vibration energy harvesting application

The modeling and optimization of a direct-drive contactless tubular linear generator are investigated to ensure a highly reliable device with long lifetime for vibration energy harvesting application. A slotless structure is considered to minimize force ripples and simplify the later control. A semi-analytical model based on harmonic Fourier modeling is considered for the calculation of the magnetic field generated by the permanent magnets. Electrical and thermal iterative models are coupled with the magnetic Fourier model into a general optimization tool that is fast and accurate, which is validated by means of a finite element model

Dynamic analysis of a tubular generator for automotive suspension applications

In this paper, a slotless three-phase tubular permanent magnet generator applied to vibration energy harvesting in automotive suspensions is considered. A two-dimensional finite element method model of the harvester is created as well as an experimental setup, containing the generator. Signal decomposition utilizing Fourier series is applied to suspension displacement data and the resulting signal components are applied to the model. The individual responses of the model are superposed, from which the corresponding harvested energy is derived. Comparisons are made with measurements on the setup that act as reference to determine the error of the harmonic reconstruction

Adaptive isogeometric analysis applied to an electromagnetic actuator

In this paper, a magnetostatic solver for linear and nonlinear soft-magnetic material characteristics, a time-harmonic eddy current solver, and the corresponding function-based error estimates are implemented in an established adaptive isogeometric analysis framework. The simplified truncated hierarchical B-spline basis functions are investigated on the multipatch geometry of a magnetic circuit, as they offer several beneficial properties, including a drastic reduction of the number of degrees of freedom compared to the references under uniform refinement. Global error estimate and global parameters convergence are illustrated for different refinement strategies and polynomial orders. Finally, the computational effort is analyzed

High-order methods applied to nonlinear magnetostatic problems

This paper presents a comparison between two high-order modeling methods for solving magnetostatic problems under magnetic saturation, focused on the extraction of machine parameters. Two formulations are compared, the first is based on the Newton-Raphson approach, and the second successively iterates the local remanent magnetization and the incremental reluctivity of the nonlinear soft-magnetic material. The latter approach is more robust than the Newton-Raphson method, and uncovers useful properties for the fast and accurate calculation of incremental inductance. A novel estimate for the incremental inductance relying on a single additional computation is proposed to avoid multiple nonlinear simulations which are traditionally operated with finite difference linearization or spline interpolation techniques. Fast convergence and high accuracy of the presented methods are demonstrated for the force calculation, which demonstrates their applicability for the design and analysis of electromagnetic devices

Design of an axial-flux permanent magnet machine for a solar-powered electric vehicle

This paper concerns the design optimization of two axial-flux permanent magnet (AFPM) machines, aimed to be used as a direct drive in-wheel motor for the propulsion of a solar-powered electric vehicle. The internal stator twin external rotor AFPM machine topology having either a distributed or toroidal stator winding configuration is investigated. The objective of the design optimization is to minimize the total volume of the machine. A gradient-based optimization algorithm is employed on a non-linear 2D equivalent motor model. The motor model consists of coupled electromagnetic and thermal models based on an Isogeometric Analysis (IGA) approach. A wide range of pole-pair numbers are optimized and compared in terms of power density and efficiency. Finally, the radius to evaluate the 2D model as a function of the pole-pair number is given, which minimizes the discrepancy with respect to the 3D finite element method (FEM)