Incrementally baked global illumination

Global Illumination is affected by the slightest change in a 3D scene, requiring a complete reevaluation of the distributed light. In cases where real-time algorithms are not applicable due to high demands on the achievable accuracy, this recomputation from scratch results in artifacts like flickering or noise, disturbing the visual appearance and negatively affecting interactive lighting design workflows. We propose a novel system tackling this problem by providing incremental updates of a baked global illumination solution after scene modifications, and a re-convergence after a few seconds. Using specifically targeted incremental data structures and prioritization strategies in a many-light global illumination algorithm, we compute a differential update from one illumination state to another. We further demonstrate the use of a novel error balancing strategy making it possible to prioritize the illumination updates.Comp Graphics & Visualisatio

Future e-government research: 13 research themes identified in the eGovRTD2020 project

E-government research has become a recognized research domain and many policies and strategies are formulated for e-government implementations. Most of these target the next few years and limited attention has been giving to the long term. The eGovRTD2020, a European Commission co-funded project, investigated the future research on e-government driven by changing circumstances and the evolution of technology. This project consists of an analysis of the state of play, a scenario-building, a gap analysis and a roadmapping activity. In this paper the roadmapping methodology fitting the unique characteristics of the e-government field is presented and the results are briefly discussed. The use of this methodology has resulted in the identification of a large number of e-government research themes. It was found that a roadmapping methodology should match the unique characteristics of e-government. The research shows the need of multidisciplinary research.Infrastructures, Systems and ServicesTechnology, Policy and Managemen

Subspace Recycling Techniques for the Accelerated Solution of Implicit Discrete Field Formulations

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Supercurrent carried by nonequilibrium quasiparticles in a multiterminal Josephson junction

We theoretically study coherent multiple Andreev reflections in a biased three-terminal Josephson junction. We demonstrate that the direct current flowing through the junction consists of supercurrent components when the bias voltages are commensurate. This dissipationless current depends on the phase in the superconducting leads and stems from the Cooper pair transfer processes induced by nonlocal Andreev reflections of the quasiparticles originating from the superconducting leads. We identify supercurrent-enhanced lines in the current and conductance maps of the recent measurement [PNAS 115, 6991 (2018)10.1073/pnas.1800044115] on a nanowire Josephson junction and show that the magnitude of the phase-dependent current components is proportional to the junction transparency with the power corresponding to the component order.QRD/Wimmer LabQN/Akhmerov GroupQN/Quantum Nanoscienc

Observation of the spin Nernst effect

The observation of the spin Hall effect triggered intense research on pure spin current transport. With the spin Hall effect, the spin Seebeck effect and the spin Peltier effect already observed, our picture of pure spin current transport is almost complete. The only missing piece is the spin Nernst (-Ettingshausen) effect, which so far has been discussed only on theoretical grounds. Here, we report the observation of the spin Nernst effect. By applying a longitudinal temperature gradient, we generate a pure transverse spin current in a Pt thin film. For readout, we exploit the magnetization-orientation-dependent spin transfer to an adjacent yttrium iron garnet layer, converting the spin Nernst current in Pt into a controlled change of the longitudinal and transverse thermopower voltage. Our experiments show that the spin Nernst and the spin Hall effect in Pt are of comparable magnitude, but differ in sign, as corroborated by first-principles calculations.QN/Nazarov GroupQN/Bauer Grou

Scenario building for E-Government in 2020: Consolidating the results from regional workshops

E-government research is currently at a stage of consolidation and new orientation. Smaller steps of government modernization have in part been successfully implemented; larger ones still lie ahead of us. Within an EC funded project, a roadmap for egovernment is being defined. Thereby, scenario building about the future is being used to grasp pictures of the future. From these future scenarios, research actions shall be derived. In this paper we present the results of the scenario building workshops in four regions for e-government in the year 2020. In total 15 scenarios were developed shaping aspects of different dimensions of alternative futures. A wide range of topics were addressed, varying from interoperability, division of power, corruption, cyber war to changing democratic systems, religious activities, participations and the role of individualisms in society. Next steps are to assess the scenario results in respect to the current EC agenda and to derive from there actions of research in order to ensure that desired futures will come true and that unwanted futures are being avoided.Infrastructures, Systems and ServicesTechnology, Policy and Managemen

Unified numerical approach to topological semiconductor-superconductor heterostructures

We develop a unified numerical approach for modeling semiconductor-superconductor heterostructures. All the key physical ingredients of these systems - orbital effect of magnetic field, superconducting proximity effect, and electrostatic environment - are taken into account on equal footing in a realistic device geometry. As a model system, we consider indium arsenide (InAs) nanowires with an epitaxial aluminum (Al) shell, which is one of the most promising platforms for Majorana zero modes. We demonstrate qualitative and quantitative agreement of the obtained results with the existing experimental data. Finally, we characterize the topological superconducting phase emerging in a finite magnetic field and calculate the corresponding topological phase diagram.QRD/Wimmer La

Giant Spin-Orbit Splitting in Inverted InAs/GaSb Double Quantum Wells

Transport measurements in inverted InAs/GaSb quantum wells reveal a giant spin-orbit splitting of the energy bands close to the hybridization gap. The splitting results from the interplay of electron-hole mixing and spin-orbit coupling, and can exceed the hybridization gap. We experimentally investigate the band splitting as a function of top gate voltage for both electronlike and holelike states. Unlike conventional, noninverted two-dimensional electron gases, the Fermi energy in InAs/GaSb can cross a single spin-resolved band, resulting in full spin-orbit polarization. In the fully polarized regime we observe exotic transport phenomena such as quantum Hall plateaus evolving in e2/h steps and a nontrivial Berry phase.QRD/Wimmer LabQuTech(OLD) Chair of Relation to Practice urQRD/Kouwenhoven La

Electronic Government and Electronic Participation

Electronic government and electronic participation continue to transform the public sector and society worldwide and are constantly being transformed themselves by emerging information and communication technologies. This book presents papers from the 14th International Federation for Information Processing’s EGOV conference (IFIP EGOV 2015), and its sister conference, the 7th Electronic Participation (ePart) conference, held in Thessaloniki, Greece, from 30 August to 2 September 2015, with the support and sponsorship of the University of Macedonia. Through the years, both of these conferences have established themselves as leading scientific events in their field, providing a forum for scholars to present and discuss their work. Included here are 31 accepted ongoing research papers, grouped under the following headings: eParticipation; policy modeling; open government and smart cities; general e-government; and e-government services; as well as 6 Ph.D. colloquium papers, 5 accepted posters and 3 workshops. With their combination of scientific credibility and rigor and with high relevance to practice, the papers presented here will be of interest to all those whose work involves electronic government and electronic participation.Multi Actor SystemsTechnology, Policy and Managemen

Ballistic superconductivity in semiconductor nanowires

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.QRD/Kouwenhoven LabQN/Conesa-Boj LabQRD/Wimmer LabQubit Research DivisionQN/Bakkers LabBUS/GeneralQRD/Goswami La