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In transport application, long high power PEM fuel cell stacks could suffer from voltage discrepancy between cells due to severe constraints or appearance of localized faults in case of bad water management, moreover the output power of the stack is limited by the weakest group of cells. This article proposes a three-part segmented fuel cell associated with an isolated four-source DC/DC converter which makes possible a power sharing between the fuel cell segments according to their state-of-health. This topology allows an enhanced utilization of the stack as well as fault tolerance. ZVS operation is achieved to improve global converter efficiency.

Background Stem-relatives of many winged insect orders have been identified among Pennsylvanian fossils (Carboniferous Period). Owing to their presumed 'basal' position in insect phylogeny, stoneflies were expected to occur at this period. However, no relative has ever been designated convincingly. Results In this paper, we report specimens belonging to a new fossil insect species collected from the Tupo Formation (Pennsylvanian; China). The wing venation of Gulou carpenteri gen. et sp. nov. exhibits character states diagnostic of the order Plecoptera, but lack character states shared by unequivocal representatives of the order. Derived from this identification, the delimitation of the fossil species is ascertained based on comparison of several extant stonefly species. This comparative analysis allowed a trait present in G. carpenteri gen. et sp. nov., but rarely occurring in extant species, to be documented and highlighted as atavistic. Affinities of taxa formerly proposed as putative stem-stoneflies are reconsidered in the light of the new discovery. Conclusions Gulou carpenteri gen. et sp. nov. is considered the only genuine Plecoptera reported from the Pennsylvanian. Continuing efforts on the systematics of Pennsylvanian winged insects indicate a fauna more diverse than previously appreciated. It suggests that insects already had a long, yet undocumented, history by this time.

In this paper the authors propose a design strategy that utilizes the passivity concept and a load observer in order to develop combined controller-observer systems for coordination of converters in a Fuel Cell System. The controller-observer tuning is constructed such that the fuel cell current variation is less than a maximal value in order to ensure a good state of health of the fuel cell.

12 pages; International audience; 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.

International audience; PEM fuel cell performance and lifetime strongly depend on the polymer membrane and MEA hydration. As the internal moisture is very sensitive to the operating conditions (temperature, stoichiometry, load current, water management...), keeping the optimal working point is complex and requires real-time monitoring. This article focuses on PEM fuel cell stack health diagnosis and more precisely on stack fault detection monitoring. This paper intends to define new, simple and effective methods to get relevant information on usual faults or malfunctions occurring in the fuel cell stack. For this purpose, the authors present a fault detection method using simple and non-intrusive on-line technique based on the space signature of the cell voltages. The authors have the objective to minimize the number of embedded sensors and instrumentation in order to get a precise, reliable and economic solution in a mass market application. A very low number of sensors are indeed needed for this monitoring and the associated algorithm can be implemented on-line. This technique is validated on a 20-cell PEMFC stack. It demonstrates that the developed method is particularly efficient in flooding case. As a matter of fact, it uses directly the stack as a sensor which enables to get a quick feedback on its state of health.

LGEP 2011 ID = 762; International audience; In this article, we aim at optimizing an innovative tandem structure based on polymorphous and microcrystalline silicon for the top and bottom elementary cells, respectively, combined with an originalDC-DC converter. The studied tandem structure is composed of two cells, each being connected to its own separate electrodes making the structure electrically decoupled but optically coupled. In those conditions, the constraint of current matching usually needed in the classical micromorph structures is avoided. As a result, the robustness against the current variations is enhanced and the efficiency of the structure is improved. Since the top cell plays the main role in the determination of the transmitted part of the incoming flux to the bottom cell, the thickness of the intrinsic layer of the polymorphous cell is tuned so that the output power of the global structure becomes maximal. To implement the electric decoupling of two sub cells, the studied structure needs two static converters. In order to minimize the converters bulk, we design an innovative output electric architecture and its optimized related control signals.

In this paper, an innovative control strategy for hybrid power sources dedicated to automotive applications is detailed. First, an analysis of classical hybrid architectures using fuel cell (FC)/supercapacitors is presented. Then, an analysis of load requirements for automotive applications is proposed. A new control strategy of a single converter, based on a cascaded control loop with a decoupling strategy in the frequency domain, is fully explained. Finally, experimental results on a Ballard proton exchange membrane FC are presented to illustrate the effectiveness of the proposed method.

International audience; This paper presents three current control strategies for a switched reluctance machine (SRM). Two classical controllers are recall : the hysteresis and the proportional-integral controller. Dynamic and current ripples with both controllers are compared and discussed. Then, a new current controller qualified as "hybrid controller" is proposed. It is a combination of the two previous structures. The principle of this controller is detailed and its influence on the current control performance is described. The three strategies are first tested by simulation, and then on an experimental test bench.

International audience; This paper deals with the optimization of a parallel hybrid Fuel Cell (FC)/ Ultracapacitors (UCs) power source for automotive applications. The aim of this hybridization and its control are to fulfil the load requirements as well as to comply with the component constraints (high efficiency, reduced weight and cost, etc.). First, a classical hybrid architecture using FC/UCs and a two-converter structure is presented. After that, power requirements for automotive applications are analyzed, and the load power demands for the FC/UCs sources are deduced. Secondly, the model-based design approach is used for the optimization, and a selection of the main components to be optimized is presented. Thus, the simulation model and the control strategy are detailed. This model has been validated experimentally. Finally, an optimization algorithm is designed using Parallel Computing and the Genetic Algorithm toolbox of Matlab/Simulink. The retained criterion is based on the reduction of the total volume of the system.

In this paper, a new control strategy including saturation management of hybrid fuel cell/ultracapacitors power source is described. First, an analysis of hybrid architectures using fuel cells and ultracapacitors for automotive applications is presented. Then, a two-converter parallel configuration is more precisely detailed. The model and the control strategy are described using the Energetic Macroscopic Representation (EMR). So, the main originality of this paper is based on the consideration of the systems limits. This leads to a very complete Energy Management Strategy, which has been evaluated and validated in simulation.

LGEP 2011 ID = 907; International audience; A non linear passivity-based control can be suitably used to achieve stability of a Parallel Hybrid Fuel Cell/Supercapacitor (FC/SC) Power Source Architecture. Nevertheless, passivity properties are usually lost when such a controller is implemented in a sampled-data context and, as a consequence, stabilization objectives are degraded. This paper proposes a direct sampled-data control strategy based on the IDA-PBC techniques, ensuring the stabilization of the (FC/SC) system at its desired equilibrium point. Such a controller guarantees good energetic performances for a large range of sampling periods and small current amplitudes. Arguing so such a digital controller avoids the premature usage of FC and SCs, maintains a good transient response and can be implemented by cheaper computers, dealing important industrial requirements.

This paper deals with the corrective action with a power converter for a 100kW multiple fuel cells (FC) generator under fault and used for vehicle propulsion, or high power onboard electrical assistance. The objective is to permit, through the power converter and its control strategy, a soft shut-down of a FC stack in fault and guarantee a continuous of operation at a reduced power, acceptable by the specifications. The power converter should also realize the power management during the degraded working situation. Two power system architectures are studied and compared by numerical simulation.

International audience; This paper scope is centered in the PEM fuel cell stack health diagnosis. For this purpose, authors present fault detection and identification methods using simple and non-intrusive on-line monitoring techniques. The approach is gradual based on detection and identification methods applied to a single cell up to multi-cells stacks used for power applications like transportation. A very low number of sensors are needed for the monitoring and the technique can be implemented on-line. Numerical simulation results illustrate the advantages of the different techniques.

This paper deals with the use of supercapacitors as ancillary power supply in transport applications powered by a PEM fuel cell. These applications are known for strong transient power demand which makes supercapacitors a relevant choice. The aim of this association and its associated power management is to guarantee load requirements as well as to minimize fuel consumption and to ensures that each component constraint is satisfied (lifetime, reliability, high efficiency, …). The designed strategy uses a cascade control allowing a frequency decomposition of the power demand cycle: supercapacitors supply the high band of the load power frequency spectrum whereas low frequencies are provided by the fuel cell which contributes to the longterm autonomy. An experimental 1 kW power test bench has been designed to illustrate the effectiveness of the proposed method. Experimental results are presented demonstrating that this approach provides improvements in terms of a significant energy savings when ancillary power supply is implemented.

This paper is in the scope of fuel cell robust control. As a matter of fact, reliability and lifetime are the two major key points for fuel cell commercialization, especially as far as proton exchange membrane technology is concerned. To bring about these essential properties, the system designer needs to build a robust control law based on a suitable and on-line state of health knowledge. For this latter diagnosis purpose, we describe a new on-line impedance spectroscopy which gets accurate data while still allowing load monitoring.

In this paper, two control strategies for two parallel hybrid fuel cell/supercapacitors power source are described. First, different hybrid architectures using fuel cells for automotive applications are analyzed. Two parallel hybrid configurations are more precisely detailed and their control strategies are explained. Then, experimental validations using a Nexa Ballard PEM-FC as main source and BOOSTCAP Maxwell supercapacitors as auxiliary source are presented to illustrate the effectiveness of the proposed control strategies.

This paper deals with reliability of motor drive systems. It focuses on the switching power converter which is the weakest drive part. It investigates a new architecture which provides intrinsic redundancy. The method used in this fault switch detection and diagnosis is based on a sliding mode observer. The original aspect of this new approach is that the observer influences the control algorithm in order to rule out or accept the possibility of the device failure. This leads to the right decision which induces the rebuilding of the converter topology. This fault tolerant control strategy assures continuous operation even though one switch failure occurs.

This paper describes a control system that has been designed to handle sensor faults and therefore could be considered as fault-tolerant control one. The fault tolerant controller is based on the output of the speed sensor and two speed observers. The first one is a suboptimal Kalman filter based on the state model of the machine. The second one is based on the estimation of the frequency of one "rotor slot harmonic" present in the DC current signal which contains speed information. The two observers guarantee the best dynamic and steady state performances required by the application and also improve the reliability in the event of sensor loss or sensor recovery. The fault tolerant controller reorganization is based on a control decision block which depends on the steady state and dynamic performances of the two observers. The results of the control system show the effectiveness of this approach in the event of speed sensor loss and recovery. (6 pages)

9 pages; International audience; Based on published data and review of Mecynoptera splendida Handlirsch, 1904, a wing venation ground plan applicable to most taxa of the Palaeozoic superorder Palaeodictyopteroidea is proposed, where each major vein system has a simple anterior sector, and, primitively, a dichotomously branched posterior sector. Lodetiella magnifica nov. gen. and sp. is described, based on an isolated hind wing from the Salagou Formation (Middle to Late Permian; He´rault, France). The venation of Lodetiella magnifica conforms to the predicted ground plan, but differs by its simple posterior cubitus sector. This character is diagnostic of the family Calvertiellidae (Palaeodictyoptera), whose diagnosis is updated.Wing movement in flight is inferred from the peculiar wing vein organization of Lodetiella magnifica. Some ecological preferences might explain the relative rarity of calvertiellids in the fossil record.

This paper deals with reliability of motor drive systems. It focuses on the switching power converter which is the weakest drive part. It investigates a new architecture which provides intrinsic redundancy. The method used in this fault switch detection and diagnosis is based on a sliding mode observer. The original aspect of this new approach is that the observer influences the control algorithm in order to rule out or accept the possibility of the device failure. This leads to the right decision which induces the rebuilding of the converter topology. This fault tolerant control strategy assures a limp-back operation.

Assessing the insect evolution around the Permian/Triassic boundary faces various pitfalls. The taxonomic and phylogenetic frames are not consensually established, and diverse evidences suggest that the record is incomplete. Nevertheless, extensive studies in progress on the super-ordinal clades Archaeorthoptera and Odonatoptera reveal common trends. Several important lineages get extinct, and groups underrepresented or absent in Late Permian became major components of the entomofauna in Middle Triassic. In addition, the radiation of the Diptera and the diversification of the Coleoptera in the Triassic also support the hypothesis of an important renewal of the entomofauna at the Permian/Triassic boundary. To cite this article: O. Bethoux et al., C. R. Palevol 4 (2005) .

After optimization of the Au-concentration and the annealing temperature highly sensitive Au Ge-film thermometers for the temperature range 30 mK–300 K were obtained. The thermometers slow a good reproducibility, a very short relaxation time constant (determined by measurements of the heat capacity of the thermometer and the thermal contact resistance of a usual grease contact) and they are quite insensitive to the magnetic field.

Arising from R. Garrouste et al. , 82–85 (2012)10.1038/nature11281 The origin of winged insects (Pterygota), one of the planet’s most diverse lineages of organisms, is assumed to lie in the Devonian, but as an extremely sparse fossil record impedes our understanding of their early diversification, any well-preserved insect fossil from this time would be particularly valuable1. Garrouste et al.2 described an arthropod from Upper Devonian freshwater sediments from the Strud locality in Belgium (∼360 million years ago) as an insect, Strudiella devonica. However, based on a thorough re-investigation of the specimen, we conclude that this interpretation is untenable. Hence we believe that, like several other Devonian arthropod remains3,4,5,6,7, Strudiella is not an insect, and utmost diligence should be taken in interpreting poorly preserved Devonian arthropods.

International audience; Series multi-cell converters provide many degrees of freedom. Direct control laws make perfect use of them during transient behaviours but leads to disorderly and imperfect steady-state cycles [4]. The direct command, we propose in this paper, enables the multi-cell converter to reach the optimal steady-state trajectory defined by a P.W.M. control technique. As usual, this control strategy enforce naturally high dynamic properties. Thus, it combines the best features of PWM techniques and direct control strategies. Moreover, this control scheme only needs external variables measurement (input voltage and output current). For the sake of simplicity, the control algorithm, the observer structure as well as the association of both of them are described carefully in the case of a two-cell chopper.

Revision of Protagrion audouini Brongniart, 1893, from Upper Carboniferous (Palaeoptera). The enigmatic Upper Carboniferous 'palaeopteron' Protagrion audouini Brongniart, 1893, is re-described and its phylogenetic position discussed. Even if the main currently accepted groups of the 'palaeodictyopterid' lineage are not based on clear synapomorphies, Protagrion has none of those of the Odonatoptera and Ephemeroptera. It shares with the Megasecoptera a probable synapomoiphy, not present in others 'palaeodictyopterid' groups., Protagrion audouini Brongniart, 1893, Paléoptère énigmatique du Carbonifère supérieur, est redécrit et sa position phylogénétique discutée. Même si les grands groupes de la lignée palaéodictyoptère ne sont pas basés sur des synapomorphies bien définies, Protagrion n'en présente aucune des Odonatoptera ou des Ephemeroptera. Il partage avec les Megasecoptera une synapomorphie probable, absente dans les autres lignées de type palaéodictyoptère., Béthoux Olivier, Nel André. Révision de Protagrion audouini Brongniart, 1893, du Carbonifère supérieur (Palaeoptera). In: Bulletin de la Société entomologique de France, volume 108 (3), août 2003. pp. 237-244.

Levitation bearings are intrinsically unstable, nonlinear and highly uncertain systems. In this paper, we focus our attention on sliding mode controllers which allow robust design and more particularly on second order sliding mode control which appears very relevant with respect to the process structure.

After the revision of several fossils and observations of recent taxa, we propose a new interpretation of the wing venation pattern for the ‘orthopteroid lineage’. The Orthoptera and several taxa previously assigned to the paraphyletic group ‘Protorthoptera’ are included in a common clade, Archaeorthoptera taxon nov. The Orthoptera and some closest relative groups are included in the Panorthoptera sensu nov. These assignments are based on new autapomorphies based on venation patterns. A cladistic phylogenetic analysis of the Orthoptera is performed for the first time on the fossil record of this group, based on 74 characters (131 informative states). Three taxa assigned to the Archaeorthoptera nec Panorthoptera compose the outgroup. The ingroup is composed of three Panorthoptera nec Orthoptera and 63 Orthoptera, mainly from the Palaeozoic and Mesozoic. Following this initial phylogeny, we propose several nomenclatural changes; the Ensifera are redefined and the relationships between Caelifera and Ensifera sensu nov., and those between the major clades of modern Ensifera sensu nov., are clarified. Relationships within the ‘oedischioid’ stem-group remain unclear. The evolution of the venational structures within the Orthoptera is discussed and in this analysis the Orthoptera were not clearly affected by the Permo-Triassic biodiversity “crisis”. The capacity of the fossil taxa to be used in phylogenetic analyses is discussed, using the example of the ‘orthopteroid’ insects.

In this paper, the fundamental problem of residual generation is studied. The solution of this problem is the first step for the solution of the fault detection problem. Here, a class of nonlinear perturbed input-affine system is considered. The technique proposed is based on two steps: the first one consists of decoupling the perturbation with respect to the fault by using the technique of output injection; and the second one consists of fault detection by logic decision. A nonlinear observer with linearizable estimated error dynamics decoupled from the input and the disturbance is used as a residual generator. An illustrative example is presented.

International audience; In embedded systems such as electric vehicles, Proton exchange membrane fuel cell (PEMFC) has been an attractive technology for many years especially in automotive applications. This paper deals with PEMFC operation monitoring which is a current target for improvement for attaining extended durability. In this paper, supervision of the PEMFC is done using knowledge-based models. Without extra sensors, it enables a clear insight of state variables of the gases in the membrane electrode assembly (MEA) which gives the PEMFC controller the ability to prevent abnormal operating conditions and associated irreversible degradations. First, a new state-observer oriented model of the PEM fuel cell is detailed. Based on this model, theoretical and practical observability issues are discussed. This analysis shows that convection phenomena can be considered negligible from the dynamic point of view; this leads to a reduced model. Finally a state-observer enables the estimation of the inner partial pressure of the cathode by using only the current and voltage measurements. This proposed model-based approach has been successfully tested on a PEM fuel cell simulator using a set of possible fault scenarios.

It has been argued that adopting alternative nomenclatural procedures would jeopardize the importance of natural history collection by relegating reference specimens to a secondary role. Based on published statements and applications, the present contribution argues that reference specimens are an essential aspect of both the PhyloCode and the cladotypic procedures. Consequently, the latter procedures might actually result in a revival of interest in those collections, mostly by augmenting the number of reference specimens and, for the cladotypic approach, by necessitating appropriate curation and access to up-to-date research facilities.

To fulfill the transport applications, either for traction or on-board auxiliaries systems, a power generator based on fuel cell needs significant power. For this purpose, long fuel cell stacks, either mono- or multi-stack systems, are already implemented as technological solutions. Long stacks though may be affected by spatial discrepancies (fluidics, temperature) causing possible failures. The latter often occur on localized stack sections. A corrective action has to be taken to quickly restore the fuel cell’s state of health. As an alternative to fluidic action, segmented electric action is explored in this paper. First, an “All or Nothing” solution achieved with electrical by-pass circuits is analyzed: it proved simple to implement but restrictive to exploit. Consequently, a “gradual” action is proposed by using the power electronics converter associated to the fuel cell. Hence, the present work investigates the approach consisting in individually driving the electric power delivered by each segment of a long polymer electrolyte membrane fuel cell stack. Each segment is controlled independently according to its state of health. To achieve this objective, the article provides an extended multi-criteria analysis of several power converter topologies. The converter topology has to be in agreement with transportation specifications: simple, compact, having a high efficiency and should be adapted to manage fuel cell degraded modes. Among several studied topologies, resonant isolated boost stands out as a candidate topology. The related multi-port architecture and algorithm structure are analyzed by numerical simulations, taking into account degraded modes and technology considerations.

This article investigates the optimal efficiency of a photovoltaic system based on a silicon thin film tandem cell using polymorphous and microcrystalline silicon for the top and bottom elementary cells, respectively. Two ways of connecting the cells are studied and compared: (1) a classical structure in which the two cells are electrically and optically coupled; and (2) a new structure for which the “current-matching” constraint is released by the electrical decoupling of the two cells. For that purpose, we used a computer simulation to perform geometrical optimization of the studied structures as well as their electrical performance evaluation. The simulation results show that the second structure is more interesting in terms of efficiency.

Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andujar, F. Segura, Renew. Sust. Energy Rev. 13 , 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained , 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51 , 56 (2010)]. This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the rated power whereas conventional boost efficiency barely achieves 91.5% in the same operating conditions.

We report critical field results on sputtered amorphous Zr76Cu24 and Zr76Ni24 alloys. TheH c (T) obtained from calorimetric measurements is well described by assuming that both systems are weak coupling superconductors. A similar good agreement is not found forHc2(T) obtained by a resistive method; tentative explanations of this discrepancy are suggested. We also report resistivity measurements in the normal state on Zr76Ni24 alloys. Results are well interpreted in the framework of the Faber-Ziman diffraction model. An alternative explanation, the Kondo-like model for two-level systems, is also discussed.

We have measured the low temperature (from 0.1 K up to 5 K) specific heat and thermal conductivity of an amorphous ZrNi superconducting alloy "as sputtered" and after annealing. We observe a variation of the Debye temperature and of the thermal conductivity related to a structural relaxation caused by the annealing.

We report critical field results on sputtered amorphous Zr76Cu24 and Zr76Ni24 alloys. Hc(T) obtained from calorimetric measurements is well described by assuming that both systems are weak-coupling superconductors. A similar good agreement is not found for Hc2(T) obtained by a resistive method ; tentative explanations of this result is suggested.

We have measured the low temperature (from 50 mK up to 5 K) specific heat and thermal conductivity of an amorphous ZrNi superconducting alloy as sputtered and after annealing in the amorphous state. We observe after annealing a decrease of the specific heat anomaly below 0.5 K together with an increase of the thermal conductivity. These variations are in agreement with a decrease of the density of two-level systems (T.L.S.) due to the structural relaxation.

The authors report and discuss measurements of low-temperature specific heat and thermal conductivity, upper critical field near Tc, electrical resistivity, mass density and X-ray diffraction, performed on an amorphous superconducting Zr76Cu24 alloy obtained by high-rate sputtering deposition at 77K. A thermal annealing of the samples in the amorphous state before crystallisation induces a large decrease of the very low-temperature specific heat related to the two-level system excitations, whereas the thermal conductivity increases in a correlative way. Both electron and phonon contributions to the specific heat in the normal state decrease and tend towards the values of liquid-quenched (LQ) alloys of corresponding composition. At the same time, the other properties studied are less affected, likewise in LQ alloys. The occurrence upon annealing of a chemical phase separation in the amorphous state is proposed to explain the results.

In the amorphous sputtered Zr1−xFex alloy with x = 24% we observe the separation of two amorphous phases upon annealing or aging. One is Fe-rich and behaves like an assembly of superparamagnetic grains. The other is superconducting.

Publisher Summary The structural relaxation of metallic glasses obtained by annealing induces a decrease of their free-energy and consequently significant changes for some of their properties. This chapter presents the effect of structural relaxation on the low-temperature thermal conductivity, which is determined by intrinsic excitations of the disordered state together with very sensitive X-ray scattering experiments, which give direct information about the structural evolution. In the experiments, samples of Zr76Cu24 and Zr80Cu20 were prepared in the form of large foils by a high-rate DC magnetron sputtering technique. X-ray measurements were carried out with a specific small-angle scattering camera. It allows measurements over a large angular scale from the small-angle region to the first diffraction halo. Furthermore, heating of the sample can be carried out in situ inside the vacuum chamber; consequently, tiny variations of the scattered intensities upon annealing can be revealed by this highly sensitive device.

For temperatures well below their superconducting transition Tc, the thermal properties of amorphous superconducting alloys become very similar to amorphous insulators, that means governed by the low-energy excitations (Two-Level Systems) successfully proposed by the tunneling model [1]: T1.9–T2 regime for thermal conductivity below about 1 K and a residual specific heat anomaly roughly linear with T and almost universal in magnitude, of the order of a few erg/g.K at 100 mK.

Efficient regulation of the energy transfer between generating, storage and load subsystems is a topic of current practical interest. A new strategy to achieve this objective, together with its corresponding power electronics implementation, was recently proposed by the authors. The device is called dynamic energy router (DER) because, in contrast with current practice, the regulation of the direction and rate of change of the power flow is done without relying on steady–state considerations. A key assumption for the correct operation of the DER is that dissipation in the system is negligible. Unfortunately, in the presence of dissipation the original DER ceases to be operational. In this paper a new DER that takes into account the presence of losses is proposed. Simulation and experimental evidence of the performance improvement with the new DER are presented.