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Morgan C.,Julich Research Center | Morgan C.,JARA Julich Aachen Research Alliance | Schmalbuch K.,JARA Julich Aachen Research Alliance | Schmalbuch K.,RWTH Aachen | And 7 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2013

We present results showing the structural and magnetic properties of MBE-grown extended films and nanostructured elements of various CoPd alloys. X-ray diffraction studies show that the thin films are polycrystalline, yet exhibit a strong preferential growth orientation along the (111) direction. Magnetic force microscopy and SQUID are used to gain an understanding of the magnetic behavior of the CoPd system with respect to competing anisotropy contributions, based on temperature-dependent SQUID data, collected between 4 and 300 K. The idea and potential implications of using CoPd as a contact material to achieve spin injection in carbon nanotube-based devices is discussed. © 2012 Elsevier B.V. All rights reserved. Source


Axer M.,Julich Research Center | Strohmer S.,Julich Research Center | Grassel D.,Julich Research Center | Bucker O.,Julich Research Center | And 7 more authors.
Frontiers in Neuroanatomy | Year: 2016

Research of the human brain connectome requires multiscale approaches derived from independent imaging methods ideally applied to the same object. Hence, comprehensible strategies for data integration across modalities and across scales are essential. We have successfully established a concept to bridge the spatial scales from microscopic fiber orientation measurements based on 3D-Polarized Light Imaging (3D-PLI) to meso- or macroscopic dimensions. By creating orientation distribution functions (pliODFs) from high-resolution vector data via series expansion with spherical harmonics utilizing high performance computing and supercomputing technologies, data fusion with Diffusion Magnetic Resonance Imaging has become feasible, even for a large-scale dataset such as the human brain. Validation of our approach was done effectively by means of two types of datasets that were transferred from fiber orientation maps into pliODFs: simulated 3D-PLI data showing artificial, but clearly defined fiber patterns and real 3D-PLI data derived from sections through the human brain and the brain of a hooded seal. © 2016 Axer, Strohmer, Gräßel, Bücker, Dohmen, Reckfort, Zilles and Amunts. Source


Bussar C.,RWTH Aachen | Bussar C.,JARA Julich Aachen Research Alliance | Stocker P.,RWTH Aachen | Stocker P.,JARA Julich Aachen Research Alliance | And 12 more authors.
Journal of Energy Storage | Year: 2016

Driven by decreasing prices for photovoltaic (PV) systems and incentive programs of different governments, almost 100 GW of PV and over 100 GW of wind turbines (WT) have been integrated in the European power system by 2014. In some areas, the electricity generation already exceeds the demand, curtailing generation or pushing the existing power transmission infrastructure to its limits in certain hours. In order to reach the European Commission's targets for 2050, the integration of renewable energies will require flexibility sources, independent of conventional generation, in order to provide standard security of supply. Together different flexibility sources will ensure the match between demand and supply at any given time. Energy storage systems can provide this flexibility by shifting the load temporally while transmission grids provide the shift of load spatially. Up to a certain extent, transmission capacity and storage capacity can replace each other, i.e. storage can reduce the load on transmission infrastructure by mitigating local peaks in load and/or generation. For the transition to a fully renewable energy system by 2050, major changes have to be achieved in the structure of the power system. The planning tool GENESYS is a holistic approach that optimises the allocation and size of different generation technologies, storage systems and transnational transmission corridors of a European power system. The source code for the mentioned tool is available free of charge under LGPL license. It can be freely parameterized by the user which allows the study of different power systems under individual assumptions with regard to load, generation potential and cost of the different system components. This publication will give an introduction to the planning methodology, the system model and the optimisation approach. Optimisation results obtained with GENESYS for a fully renewable electricity system for Europe and a cost structure expected for 2050 will be presented together with sensitivity analyses investigating main assumptions. Outcomes show the optimal allocation of PV and WT in a European power system, the resulting demand for storage capacities of different technologies and the capacity of the overlay grid. © 2016 Elsevier Ltd. Source


Tappertzhofen S.,RWTH Aachen | Tappertzhofen S.,JARA Julich Aachen Research Alliance | Hempel M.,RWTH Aachen | Hempel M.,JARA Julich Aachen Research Alliance | And 6 more authors.
Materials Research Society Symposium Proceedings | Year: 2011

Silicon dioxide based Electrochemical Metallization (ECM) cells were intensively studied as a promising candidate for CMOS compatible non-volatile memory devices. The resistance of ECM cells can be switched between a high resistive (OFF) state and a low resistive (ON) state by applying a sufficient voltage or current pulse. This resistance transition is attributed to the formation and rupture of a few nanometers in diameter metallic filament. However, the metal ion transport which is believed to be responsible for the filamentary switching mechanism is not understood in detail. In case of SiO 2 we suppose protons or humidity may enhance the metal ion transport. In this work we report our studies on the proton incorporation in amorphous SiO 2 thin films focused on the impact of hydrogen and humidity on the resistive switching effect. The switching behavior was analyzed by current-voltage measurements performed at different ambient conditions. The incorporation of hydrogen has been confirmed by Time-of-Flight Secondary-Ion-Mass-Spectroscopy (ToF-SIMS). The results led to an expansion of the defect model proposed in the literature. © 2011 Materials Research Society. Source


Linn E.,RWTH Aachen | Linn E.,JARA Julich Aachen Research Alliance | Menzel S.,RWTH Aachen | Menzel S.,JARA Julich Aachen Research Alliance | And 9 more authors.
Proceedings of the IEEE Conference on Nanotechnology | Year: 2011

Complementary Resistive Switches (CRS) alleviate size limitations for passive crossbar array memory devices by the elimination of sneak paths. Since CRS cells consist of two anti-serially connected bipolar resistive elements, e.g. electro-chemical metallization (ECM) elements, it is straightforward to use their corresponding memristive models for circuit simulation. Here we show that simple linear memristive models, which are often used in literature, are inapplicable. Therefore, we apply a physics based nonlinear model for ECM elements which is capable of simulating correct CRS behavior for anti-serially combined elements. Interconnecting memristive element models in CRS configuration is an advantageous way to check for memristive model consistency. © 2011 IEEE. Source

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