This study considers a Hybrid Electrical Vehicle supplied by a Fuel Cell stack and supercapacitors used as Storage Element. In such an application, real time energy management is of paramount importance in order to increase autonomy and be able to deal on-line with perturbed power demand. Many offline power flow optimization principles are available but online algorithms are preferred and should be derived for optimal management of the instantaneous power splitting between the different available power sources. Based on particle swarm optimization algorithm, this study defines the parameters tuning of such algorithm. The final power splitting allows not only recovering energy braking but also is robust to some disturbances occurring during the trip. The solution provides good-quality and high-robustness results in a certain class of mission profile and power disturbance.

CuIn1-xAlxS2 (CIAS) thin films with different compositions were deposited by the evaporation of the powder of CuIn1-xAlxS2 on to glass substrates heated at 200 °C. The different thin films were obtained with increasing the content aluminium in the powder. Structural, morphological and optical properties of the films were studied in function of the Al content. Polycrystalline CIAS thin films orientated preferentially along the (112) plane were obtained. Then the crystallites have a similar shape as that of all as-deposited films. The incorporation of aluminium atoms moves the main absorption on the left with varied band gap between 1.5 eV and 1.90 eV.

This paper deals with multi-physics modelling of the stationary system. This modelling is the first step to reach the fuel cell system dimensioning aim pursued. Besides this modelling approach based on the stationary energetic system, the novelty in this paper is both the new approach of the photovoltaic EMR modelling and the EMR of the hydrogen storage process. The granular modelling approach is used to model each component of the system. Considering a stand alone PEM fuel cell system, hydrogen is expected to be produced and stored on the spot from renewable energy (photovoltaic) in order to satisfy the fuel availability. In fact, to develop a generic and modular model, energetic macroscopic representation (EMR) is used as graphical modelling tool. Allowing to be easily grasped by the experts even not necessarily gotten used to the modelling formalism, EMR is helpful to model the multi-domains energetic chain. The solar energy through solar module is converted in electrical energy; part of this energy is transformed in chemical energy (hydrogen) thanks to an electrolyser. Then the hydrogen is compressed into a tank across a storage system. The latter part of the solar module energy is stored as electrical energy within supercapacitor or lead-acid battery. Using the modularity feature of the EMR, the whole system is modelled entity by entity; afterwards by putting them together the overall system has been reconstructed. According to the scale effect of the system entities, some simulation and/or experimental results are given. Given to the different aims which are pursued in the sustainable energy framework like prediction, control and optimisation, EMR modelling approach is a reliable option for the energy management in real time of energetic system in macroscopic point of view.

Colossal ionic conductivity was recently discovered in YSZ/SrTiO3 multilayers and was explained in terms of strain- and interface-enhanced disorder of the O sublattice. In the present paper we use a combination of scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) and theoretical EELS simulations to confirm the presence of a disordered YSZ O sublattice in coherent YSZ/SrTiO3 multilayers. O K-edge fine structure simulated for the strained disordered O sublattice phase of YSZ possesses blurred-out features compared to that of ordered cubic bulk YSZ, and experimental EELS fine structure taken from the strained YSZ of coherent YSZ/SrTiO3 thin films is similarly blurred out. Elemental mapping is shown to be capable of resolving ordered YSZ O sublattices. Elemental mapping of O in the coherent YSZ/STO multilayers is presented in which the O sublattice is seen to be clearly resolved in the STO but blurred out in the YSZ, indicating it to be disordered. In addition, we present imaging and EELS results which show that strained regions exist at the incoherent interfaces of YSZ islands in STO with blurred out fine structure, suggesting these incoherent regions may also support high ionic conductivities. Recently, Cavallaro et al. reported electronic conductivities in samples of incoherent disconnected islands embedded in STO that are similar to the islands described herein. The presence of a region of O depleted STO at the interface with incoherent YSZ islands is revealed by EELS elemental mapping, implying the n-type doping of STO/YSZ nanocomposites with disconnected incoherent YSZ islands.

Solid Oxide Fuel Cells (SOFCs) are of great interest due to their high energy efficiency, low emission level, and multiple fuel utilization. SOFC can operate with various kinds of fuels such as natural gas, carbon monoxide, methanol, ethanol, and hydrocarbon compounds, and they are becoming one of the main competitors among environmentally friendly energy sources for the future. In this study, a mathematical model of a co-flow planar anode-supported solid oxide fuel cell with internal reforming of natural gas has been developed. The model simultaneously solves mass, energy transport equations, and chemical as well as electrochemical reactions. The model can effectively predict the compound species distributions as well as the cell performance under specific operating conditions. The main result is a rather small temperature gradient obtained at 800 °C with S/C = 1 in classical operating conditions. The cell performance is reported for several operating temperatures and pressures. The cell performance is specified in terms of cell voltage and power density at any specific current density. The influence of electrode microstructure on cell performance was investigated. The simulation results show that the steady state performance is almost insensitive to microstructure of cells such as porosity and tortuosity unlike the operating pressure and temperature. However, for SOFC power output enhancement, the power output could be maximized by adjusting the pore size to an optimal value, similarly to porosity and tortuosity. At standard operating pressure (1 atm) and 800 °C with 48% fuel utilization, when an output cell voltage was 0.73 V, a current density of 0.38 A cm-2 with a power density of 0.28 W cm-2 was predicted. The accuracy of the model was validated by comparing with existing experimental results from the available literature.

Imaging and chemical analysis of individual metallofullerene molecules were successfully carried out without massive destruction using a scanning transmission electron microscope (STEM) operated at 30 kV. Electron energy-loss spectroscopy (EELS) unambiguously identified the constituent atom of each metallofullerene molecule. The profile of EELS chemical map measured across the single atom provides a rough estimate of EELS signal delocalization, which is considerably reduced using accelerating voltage as low as 30 kV.

We present a study of purification of single-walled carbon nanotubes (SWCNTs) using different oxidation temperatures and chemical treatments. We have developed a simple two annealing-steps procedure resulting in high nanotube purity with minimal sample loss. The process involves annealing the SWCNTs at 300 °C for 2 h with subsequent reflux in 6 M HCl at 130 °C, followed by further annealing at 350 °C for 1 h with reflux in 6 M HCl at 130 °C. The process results in effective removal of carbon impurities and metal particles which are associated with SWCNTs production. The process is less time consuming (complete in 4.5 h) than conventional acid purification methods which require over 5 h, and less destructive than conventional methods with a yield of 26%. SWCNT purity was assessed using Raman spectroscopy, thermogravimetry and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy.

Chromium doped gamma ferrite nanopowders (16.91 nm to 25.61 nm) of the composition (Fe2-xCrxO3 for x = 0.00, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10) were successfully synthesized by a modified solution combustion method using citric acid as fuel at a temperature as low as 150 °C. The so prepared samples were examined by powder XRD for phase identification and crystallite size determination. The dimensions of particle size as calculated from XRD are in good agreement with those evaluated by transmission electron microscope (TEM). Fourier Transform Infrared (FTIR) analysis was carried out to identify the various chemical bonds present in the system. Magnetic examinations were performed in terms of magnetic susceptibility and hysteresis plots. A decrease in the blocking temperature with the increase of dopant concentration was observed which is explained on the basis of Néel's relaxation theory. A simple model has been suggested to explain the behaviour of hysteresis trends as the function of dopant concentration.

The electronic structure and the magnetic moment of metallic iron are strongly modified near the Fe(100)/Co(bcc) interface. This effect has been evaluated from the iron L2,3 energy loss near edge structure recorded for Fe/Co superlattices grown by molecular beam epitaxy with different periods. The interface-induced modification of the intensity ratio I(L3)/I(L2) which has been measured by electron energy loss spectroscopy is in good agreement with the enhancement of the magnetic moment calculated from first principles. This shows that the intensity ratio can be used to obtain information on magnetic moments at a nanometer scale in a transmission electron microscope.

Water management is one of the most crucial issues to drive PEM fuel cells. The challenge is enhanced in the case of micro air-breathing proton exchange membrane fuel cells (μABFC): their thinness and their reduced surface indeed make their hydration state fast changing and very sensitive to the experimental conditions (temperature and relative humidity (RH)). It can lead to strong flooding or drying out issues. Firstly, this study highlights this sensitivity by various measurements. Then a steady state macroscopic model for the μABFC is proposed, focusing on the cathode, using a rather original approach for diffusion in porous media. Finally, a literal steady state formula for the water content is provided, and its influences on the performances of the μABFC are explicitly proposed. The model is parameterized and compared to measures in several atmospheric conditions.

The focusing property of electromagnetic wave is investigated by a flat slab made of octagonal photonic quasicrystal. We obtain polarization-independent focusing by use of the all-dielectric photonic quasicrystal. The influence of geometrical factors of photonic quasicrystal on the focusing property for TM and TE polarizations is explored in detail. The results show that two orthogonal polarizations have a common focus point only under certain proper condition. Our results may be a useful guidance for the fabrication of lens devices capable of polarization-independent focusing by photonic quasicrystal.

In this article, a $\mathcal{H}_{\infty}$ control methodology is proposed for a hybrid power generation system composed by a 500 W PEM fuel cell and a 58 F supercapacitor. The control strategy consists in synthetizing a multivariable PI controller with $\mathcal{H}_{\infty}$ performance in order to manage powers between two electrochemical sources. The controller is then designed through an optimization procedure based on solving some linear matrix inequalities (LMI). The control performance in time and frequency domains are then analyzed and compared with classical controllers. Results show the efficiency of the proposed methodology in order to reduce time spent for design.

In this work two aspects of momentum-dependent electron energy loss spectrometry are studied, both in the core-loss and in the low-loss region. In the case of core losses, we focus on the demonstration and the interpretation of an unexpected non-Lorentzian behavior in the angular part of the double-differential scattering cross-section. The silicon L3 edge is taken as an example. Using calculations we show that the non-Lorentzian behavior is due to a change in the wavefunction overlap between the initial and the final states. In the case of low losses, we first analyze the momentum-dependent loss functions of coinage metals Cu, Ag, and Au. We then demonstrate how advanced electronic structure calculations can be used to build simple models for the dielectric function that can then serve as a basis for the calculation of more complicated sample geometries.

This paper presents a procedure dealing with the issue of fault detection and isolation (FDI) using nonlinear analytical redundancy (NLAR) technique applied in a proton exchange membrane (PEM) fuel cell system based on its mathematic model. The model is proposed and simplified into a five orders state space representation. The transient phenomena captured in the model include the compressor dynamics, the flow characteristics, mass and energy conservation and manifold fluidic mechanics. Nonlinear analytical residuals are generated based on the elimination of the unknown variables of the system by an extended parity space approach to detect and isolate actuator and sensor faults. Finally, numerical simulation results are given corresponding to a faults signature matrix.

Nanoparticles (NPs) have attracted a considerable interest in the last decades, owing to their remarkable physical and chemical properties. The most important characteristic of NPs is the size effect, that is, their properties differ from that of the corresponding bulk material. We will focus here on Electron Energy-Loss Spectroscopy (EELS) investigations of Gd2O3 NPs of different and controlled sizes. EELS spectra near the O-K edge of Gd2O3 were recorded and compared with feff8.2 ELNES simulations. The calculation of the EELS response from small particles by the feff code raises some particular problems which have been carefully examined and partially solved. The simulations are in fair agreement with experiment and reveal the existence of size effects.

A novel method for ionic collisions is presented based on a theoretical analysis of the long-standing wire fragmentation problem. Based on a Maxwellian approach of the transient electrodynamic forces we deduce a theoretical formula of the effective tensile force. A number of conducted experiments with low energy capacitor bank discharges are also reported with positive results. The new results show the possibility of building solid state ion colliders below the fragmentation threshold using high power electrical pulses with very low energy.

This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 A m-2 for a 1.2 mm diameter welding electrode.

We report on spatially resolved electron energy-loss spectroscopy studies of optical modes in individual star-shaped gold nanoparticles. We studied different morphologies, ranging from a spheroid to well-developed nanostars. For each shape, essentially two groups of modes are appearing: the first one is localized around the core of the nanostars and has an energy slightly less than the quasi-static dipolar mode of a gold sphere (about 2.2 eV); in the second group, the modes are localized at the end of the nanostar tips, with varying energies depending on the geometry of each tip and with energy down to 1.2 eV. The localization of the tip modes is interpreted with the help of boundary element methods simulations.

The accurate characterization of the parameters related to the charge and water transport in the ionomer membrane of polymer electrolyte fuel cells (PEFC) is highly important for the understanding and interpretation of the overall cell behavior. Despite the big efforts to experimentally determine these parameters, a large scatter of data is reported in the literature, due to the inherent experimental difficulties. Likewise, the porosity and tortuosity of the gas diffusion layers affect the membrane water content and the local cell performance, but the published data are usually measured ex-situ, not accounting for the effect of clamping pressure. Using a quasi two-dimensional model and experimental current density data from a linear cell of technical size, a multiparameter optimization procedure based on an evolutionary algorithm has been applied to determine eight material properties highly influencing the cell performance. The optimization procedure converges towards a well defined solution and the resulting parameter values are compared to those available in the literature. The quality of the set of parameters extracted by the optimization procedure is assessed by a sensitivity analysis.

This paper focuses on the hysteresis effect of the polarization characteristics of a polymer electrolyte membrane fuel cell (PEMFC), mainly due to the compressor-air supply system dynamics. Indeed in PEMFC/ultracapacitor hybrid vehicles, fuel cells can be used to supply the low frequencies of the power demand only. First, the different parts of a FC system are described and modeled in order to analyze the transient stack performance decrease and to identify its main influential factors for automotive applications. Then, apart from humidity and temperature variations, each phenomenon is dynamically described, leading to a complete mathematical model based on macroscopic component parameters. Thus, an analytical model based on this set of equations enables us to draw the static voltage versus current FC characteristics. Furthermore, the hysteresis effect on the V-I curve, which still occurs during low dynamic responses, is shown while temperature and humidity are kept constant. Finally, dynamic responses of the Ballard PEMFC Nexa 1200 W generator are analyzed, and detailed experimentation and simulation are carried out for a large magnitude sinusoidal waveform at different frequencies.