Showing papers by "Vienna University of Technology published in 2017"
TL;DR: Improvements in the relative accuracy considering the amount of variation explained, in comparison to the previous version of SoilGrids at 1 km spatial resolution, range from 60 to 230%.
Abstract: This paper describes the technical development and accuracy assessment of the most recent and improved version of the SoilGrids system at 250m resolution (June 2016 update). SoilGrids provides global predictions for standard numeric soil properties (organic carbon, bulk density, Cation Exchange Capacity (CEC), pH, soil texture fractions and coarse fragments) at seven standard depths (0, 5, 15, 30, 60, 100 and 200 cm), in addition to predictions of depth to bedrock and distribution of soil classes based on the World Reference Base (WRB) and USDA classification systems (ca. 280 raster layers in total). Predictions were based on ca. 150,000 soil profiles used for training and a stack of 158 remote sensing-based soil covariates (primarily derived from MODIS land products, SRTM DEM derivatives, climatic images and global landform and lithology maps), which were used to fit an ensemble of machine learning methods-random forest and gradient boosting and/or multinomial logistic regression-as implemented in the R packages ranger, xgboost, nnet and caret. The results of 10-fold cross-validation show that the ensemble models explain between 56% (coarse fragments) and 83% (pH) of variation with an overall average of 61%. Improvements in the relative accuracy considering the amount of variation explained, in comparison to the previous version of SoilGrids at 1 km spatial resolution, range from 60 to 230%. Improvements can be attributed to: (1) the use of machine learning instead of linear regression, (2) to considerable investments in preparing finer resolution covariate layers and (3) to insertion of additional soil profiles. Further development of SoilGrids could include refinement of methods to incorporate input uncertainties and derivation of posterior probability distributions (per pixel), and further automation of spatial modeling so that soil maps can be generated for potentially hundreds of soil variables. Another area of future research is the development of methods for multiscale merging of SoilGrids predictions with local and/or national gridded soil products (e.g. up to 50 m spatial resolution) so that increasingly more accurate, complete and consistent global soil information can be produced. SoilGrids are available under the Open Data Base License.
2,228 citations
TL;DR: E engineered directional photonic reservoirs could lead to the development of complex quantum networks that, for example, could simulate novel classes of quantum many-body systems.
Abstract: Spinorbit coupling in electrons leads to many fascinating phenomena and important applications, from topological insulators to spintronics. Researchers have recently been exploring whether effects analogous to spinorbit coupling can arise in photons and, if so, what sort of perspectives this provides. Optical spinorbit coupling can lead to direction-dependent emissions and so may allow quantum optics to be chiral. This Review looks at experiments in the realm of chiral quantum optics and discusses how these demonstrations could add a new dimension of control to quantum networks and quantum many-body physics.
1,052 citations
Vienna University of Technology1, Centre national de la recherche scientifique2, European Centre for Medium-Range Weather Forecasts3, National Research Council4, ETH Zurich5, Finnish Meteorological Institute6, Nanjing University of Information Science and Technology7, VU University Amsterdam8, Ghent University9, Starlab10, University College Cork11
TL;DR: The European Space Agency (ESA) released the first multi-decadal, global satellite-observed soil moisture (SM) dataset as part of its Climate Change Initiative (CCI) program.
756 citations
Vienna University of Technology1, University of Potsdam2, Swedish Meteorological and Hydrological Institute3, University of Messina4, University of Split5, University of Padua6, University of Zagreb7, University of Bologna8, University of Naples Federico II9, Polytechnic University of Turin10, Moscow State University11, Dokuz Eylül University12, University of Bath13, Slovak University of Technology in Bratislava14, Finnish Environment Institute15, Czech Hydrometeorological Institute16, University of Liverpool17, University of Architecture, Civil Engineering and Geodesy18, Technical University of Madrid19, Helmholtz Centre for Environmental Research - UFZ20, ETH Zurich21, Maynooth University22, Polish Academy of Sciences23, ODESSA24, University of Ljubljana25, Roma Tre University26, Norwegian Water Resources and Energy Directorate27, Polytechnic University of Tirana28, University of Belgrade29
TL;DR: Analysis of the timing of river floods in Europe over the past 50 years found clear patterns of changes in flood timing that can be ascribed to climate effects, and highlights the existence of a clear climate signal in flood observations at the continental scale.
Abstract: A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.
557 citations
TL;DR: In this article, a review summarizes how insights from mesoscopic scattering theory have direct relevance for optical wave control experiments and vice versa, and the results are expected to have an impact on a number of fields ranging from biomedical imaging to nanophotonics, quantum information, and communication technology.
Abstract: Wave front shaping, the ability to manipulate light fields both spatially and temporally, in complex media is an emerging field with many applications. This review summarizes how insights from mesoscopic scattering theory have direct relevance for optical wave control experiments and vice versa. The results are expected to have an impact on a number of fields ranging from biomedical imaging to nanophotonics, quantum information, and communication technology.
492 citations
California Institute of Technology1, Agricultural Research Service2, University of Tsukuba3, University of Guelph4, University of Texas at Austin5, Princeton University6, Kuwait University7, University of Valencia8, University of Salamanca9, Agriculture and Agri-Food Canada10, University of Southern California11, European Academy of Bozen12, University of Grenoble13, Finnish Meteorological Institute14, National Autonomous University of Mexico15, University of Twente16, Comisión Nacional de Actividades Espaciales17, Vienna University of Technology18, Monash University19, Goddard Space Flight Center20, Massachusetts Institute of Technology21
TL;DR: The NASA Soil Moisture Active Passive (SMAP) mission has utilized a set of core validation sites as the primary methodology in assessing the soil moisture retrieval algorithm performance as mentioned in this paper.
487 citations
TL;DR: In this paper, the effects of surface textures under the operative lubrication regimes in the Stribeck curve, with a clear distinction between conformal-and non-conformal contacts, are discussed.
478 citations
Utrecht University1, United States Department of Energy2, National Autonomous University of Mexico3, National and Kapodistrian University of Athens4, University of Debrecen5, Commonwealth Scientific and Industrial Research Organisation6, Leiden University7, Maynooth University8, University of Göttingen9, University of Natural Resources and Life Sciences, Vienna10, University of Seville11, Broad Institute12, Huazhong Agricultural University13, State University of Campinas14, International Sleep Products Association15, Université libre de Bruxelles16, University of Nottingham17, Aix-Marseille University18, Pasteur Institute19, King Abdulaziz University20, Institut national de la recherche agronomique21, University of Helsinki22, University of Amsterdam23, University of Ioannina24, University of St Andrews25, Saint Petersburg State University26, Spanish National Research Council27, Federal University of São Carlos28, Swedish University of Agricultural Sciences29, Technical University of Berlin30, National Scientific and Technical Research Council31, Concordia University32, Kyungpook National University33, University of the Republic34, Karlsruhe Institute of Technology35, University of Sulaymaniyah36, University of Ljubljana37, Leibniz Association38, Stanford University39, Kansas State University40, Technical University of Denmark41, University of Wisconsin-Madison42, Pacific Northwest National Laboratory43, University of Jena44, University of São Paulo45, University of Kansas46, Imperial College London47, Université Paris-Saclay48, Vienna University of Technology49
TL;DR: In this article, a comparative genomics and experimental study of the aspergilli genus is presented, which allows for the first time a genus-wide view of the biological diversity of the Aspergillus and in many, but not all, cases linked genome differences to phenotype.
Abstract: Background: The fungal genus Aspergillus is of critical importance to humankind. Species include those with industrial applications, important pathogens of humans, animals and crops, a source of potent carcinogenic contaminants of food, and an important genetic model. The genome sequences of eight aspergilli have already been explored to investigate aspects of fungal biology, raising questions about evolution and specialization within this genus. Results: We have generated genome sequences for ten novel, highly diverse Aspergillus species and compared these in detail to sister and more distant genera. Comparative studies of key aspects of fungal biology, including primary and secondary metabolism, stress response, biomass degradation, and signal transduction, revealed both conservation and diversity among the species. Observed genomic differences were validated with experimental studies. This revealed several highlights, such as the potential for sex in asexual species, organic acid production genes being a key feature of black aspergilli, alternative approaches for degrading plant biomass, and indications for the genetic basis of stress response. A genome-wide phylogenetic analysis demonstrated in detail the relationship of the newly genome sequenced species with other aspergilli. Conclusions: Many aspects of biological differences between fungal species cannot be explained by current knowledge obtained from genome sequences. The comparative genomics and experimental study, presented here, allows for the first time a genus-wide view of the biological diversity of the aspergilli and in many, but not all, cases linked genome differences to phenotype. Insights gained could be exploited for biotechnological and medical applications of fungi.
349 citations
TL;DR: The International Energy Agency (IEA) Energy in Buildings and Community (EBC) Programme Annex 66 has established a scientific methodological framework for occupant behavior research, including data collection, behavior model representation, modeling and evaluation approaches, and the integration of behavior modeling tools with building performance simulation programs as mentioned in this paper.
338 citations
King Abdullah University of Science and Technology1, Goddard Space Flight Center2, Ohio State University3, Ghent University4, Wageningen University and Research Centre5, Vienna University of Technology6, University of Tasmania7, University of Nebraska–Lincoln8, Chinese Academy of Sciences9, Texas A&M University10, Princeton University11
TL;DR: In just the past five years, the field of Earth observation has progressed beyond the offerings of conventional space agency based platforms to include a plethora of sensing opportunities afforded by CubeSats, Unmanned Aerial Vehicles, and smartphone technologies that are being embraced by both for-profit companies and individual researchers.
Abstract: In just the past five years, the field of Earth observation has progressed beyond the offerings of conventional space agency based platforms to include a plethora of sensing opportunities afforded by CubeSats, Unmanned Aerial Vehicles (UAVs), and smartphone technologies that are being embraced by both for-profit companies and individual researchers. Over the previous decades, space agency efforts have brought forth well-known and immensely useful satellites such as the Landsat series and the Gravity Research and Climate Experiment (GRACE) system, with costs typically on the order of one billion dollars per satellite and with concept-to-launch timelines on the order of two decades (for new missions). More recently, the proliferation of smartphones has helped to miniaturise sensors and energy requirements, facilitating advances in the use of CubeSats that can be launched by the dozens, while providing ultra-high (3-5 m) resolution sensing of the Earth on a daily basis. Start-up companies that did not exist five years ago now operate more satellites in orbit than any space agency, and at costs that are a mere fraction of the cost of traditional satellite missions. With these advances come new space-borne measurements, such as real-time high-definition video for tracking air pollution, storm-cell development, flood propagation, precipitation monitoring, or even for constructing digital surfaces using structure-from-motion techniques. Closer to the surface, measurements from small unmanned drones and tethered balloons have mapped snow depths, floods, and estimated evaporation at sub-meter resolutions, pushing back on spatio-temporal constraints and delivering new process insights. At ground level, precipitation has been measured using signal attenuation between antennae mounted on cell phone towers, while the proliferation of mobile devices has enabled citizen-scientists to catalogue photos of environmental conditions, estimate daily average temperatures from battery state, and sense other hydrologically important variables such as channel depths using commercially available wireless devices. Global internet access is being pursued via high altitude balloons, solar planes, and hundreds of planned satellite launches, providing a means to exploit the Internet of Things as an entirely new measurement domain. Such global access will enable real-time collection of data from billions of smartphones or from remote research platforms. This future will produce petabytes of data that can only be accessed via cloud storage and will require new analytical approaches to interpret. The extent to which today's hydrologic models can usefully ingest such massive data volumes is unclear. Nor is it clear whether this deluge of data will be usefully exploited, either because the measurements are superfluous, inconsistent, not accurate enough, or simply because we lack the capacity to process and analyse them. What is apparent is that the tools and techniques afforded by this array of novel and game-changing sensing platforms present our community with a unique opportunity to develop new insights that advance fundamental aspects of the hydrological sciences. To accomplish this will require more than just an application of the technology: in some cases, it will demand a radical rethink on how we utilise and exploit these new observing systems to enhance our understanding of the Earth and its linked processes.
319 citations
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2333 more•Institutions (195)
TL;DR: In this paper, the authors acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies:======BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ,======And FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS======(Colombia); MSES and CSF (Croatia); RPF (
Abstract: we acknowledge the enduring support for the construction and
operation of the LHC and the CMS detector provided by the following funding agencies:
BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ,
and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS
(Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador);
MoER, ERC IUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland);
CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece);
OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN
(Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia);
BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New
Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna);
MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain);
Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR and
NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC
(United Kingdom); DOE and NSF (U.S.A.).
TL;DR: In this paper, the Higgs boson mass was measured in the H → ZZ → 4l (l = e, μ) decay channel and the signal strength modifiers for individual Higgs production modes were also measured.
Abstract: Properties of the Higgs boson are measured in the H → ZZ → 4l (l = e, μ) decay channel. A data sample of proton-proton collisions at $ \sqrt{s}=13 $ TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb$^{−1}$ is used. The signal strength modifier μ, defined as the ratio of the observed Higgs boson rate in the H → ZZ → 4l decay channel to the standard model expectation, is measured to be μ = 1.05$_{− 0.17}^{+ 0.19}$ at m$_{H}$ = 125.09 GeV, the combined ATLAS and CMS measurement of the Higgs boson mass. The signal strength modifiers for the individual Higgs boson production modes are also measured. The cross section in the fiducial phase space defined by the requirements on lepton kinematics and event topology is measured to be 2. 92$_{− 0.44}^{+ 0.48}$ (stat)$_{− 0.24}^{+ 0.28}$ (syst)fb, which is compatible with the standard model prediction of 2.76 ± 0.14 fb. Differential cross sections are reported as a function of the transverse momentum of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet. The Higgs boson mass is measured to be m$_{H}$ = 125.26 ± 0.21 GeV and the width is constrained using the on-shell invariant mass distribution to be Γ$_{H}$ < 1.10 GeV, at 95% confidence level.
TL;DR: A 1-bit implementation of a microprocessor using a two-dimensional semiconductor—molybdenum disulfide that can execute user-defined programs stored in an external memory, perform logical operations and communicate with its periphery is presented.
Abstract: The advent of microcomputers in the 1970s has dramatically changed our society. Since then, microprocessors have been made almost exclusively from silicon, but the ever-increasing demand for higher integration density and speed, lower power consumption and better integrability with everyday goods has prompted the search for alternatives. Germanium and III-V compound semiconductors are being considered promising candidates for future high-performance processor generations and chips based on thin-film plastic technology or carbon nanotubes could allow for embedding electronic intelligence into arbitrary objects for the Internet-of-Things. Here, we present a 1-bit implementation of a microprocessor using a two-dimensional semiconductor-molybdenum disulfide. The device can execute user-defined programs stored in an external memory, perform logical operations and communicate with its periphery. Our 1-bit design is readily scalable to multi-bit data. The device consists of 115 transistors and constitutes the most complex circuitry so far made from a two-dimensional material.
01 Dec 2017
TL;DR: This work model the service placement problem for IoT applications over fog resources as an optimization problem, which explicitly considers the heterogeneity of applications and resources in terms of Quality of Service attributes, and proposes a genetic algorithm as a problem resolution heuristic.
Abstract: The Internet of Things (IoT) leads to an ever-growing presence of ubiquitous networked computing devices in public, business, and private spaces. These devices do not simply act as sensors, but feature computational, storage, and networking resources. Being located at the edge of the network, these resources can be exploited to execute IoT applications in a distributed manner. This concept is known as fog computing. While the theoretical foundations of fog computing are already established, there is a lack of resource provisioning approaches to enable the exploitation of fog-based computational resources. To resolve this shortcoming, we present a conceptual fog computing framework. Then, we model the service placement problem for IoT applications over fog resources as an optimization problem, which explicitly considers the heterogeneity of applications and resources in terms of Quality of Service attributes. Finally, we propose a genetic algorithm as a problem resolution heuristic and show, through experiments, that the service execution can achieve a reduction of network communication delays when the genetic algorithm is used, and a better utilization of fog resources when the exact optimization method is applied.
Vienna University of Technology1, University of Florence2, University of Bern3, Newcastle University4, University of Natural Resources and Life Sciences, Vienna5, University of Padua6, Centre national de la recherche scientifique7, Spanish National Research Council8, Slovak Academy of Sciences9, University of Kiel10, Slovak University of Technology in Bratislava11, University of Innsbruck12, University of Rostock13, University of Kassel14, University of Hradec Králové15, Lancaster University16, University of Vienna17, Wageningen University and Research Centre18
TL;DR: In this article, the authors identified research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage, and terracing, and proposed strategies in addressing these gaps.
Abstract: Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage, and terracing are identified. Potential strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long-term experiments on physical-chemical-biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology.
TL;DR: This paper provides a unifying framework, discussion, and performance evaluation of FBMC and compares it with OFDM-based schemes and derives closed-form solutions for the signal-to-interference ratio in doubly-selective channels and shows that in many practical cases, one-tap equalizers are sufficient.
Abstract: Future wireless systems will be characterized by a large range of possible uses cases. This requires a flexible allocation of the available time-frequency resources, which is difficult in conventional orthogonal frequency division multiplexing (OFDM). Thus, modifications of OFDM, such as windowing or filtering, become necessary. Alternatively, we can employ a different modulation scheme, such as filter bank multi-carrier (FBMC). In this paper, we provide a unifying framework, discussion, and performance evaluation of FBMC and compare it with OFDM-based schemes. Our investigations are not only based on simulations, but are substantiated by real-world testbed measurements and trials, where we show that multiple antennas and channel estimation, two of the main challenges associated with FBMC, can be efficiently dealt with. In addition, we derive closed-form solutions for the signal-to-interference ratio in doubly-selective channels and show that in many practical cases, one-tap equalizers are sufficient. A downloadable MATLAB code supports reproducibility of our results.
TL;DR: In this paper, the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes are described.
TL;DR: Results show that the -value classification provides a robust basis for decisions regarding using either active or passive data alone, or an unweighted average in cases where relative weights cannot be estimated reliably, and that the weights estimated from TCA in almost all cases outperform the ternary decision upon which the ESA CCI SM v02.3 is based.
Abstract: We propose a method for merging soil moisture retrievals from spaceborne active and passive microwave instruments based on weighted averaging taking into account the error characteristics of the individual data sets. The merging scheme is parameterized using error variance estimates obtained from using triple collocation analysis (TCA). In regions where TCA is deemed unreliable, we use correlation significance levels ( $p$ -values) as indicator for retrieval quality to decide whether to use active data only, passive data only, or an unweighted average. We apply the proposed merging scheme to active retrievals from advanced scatterometer and passive retrievals from the Advanced Microwave Scanning Radiometer—Earth Observing System using Global Land Data Assimilation System-Noah to complement the triplet required for TCA. The merged time series is evaluated against soil moisture estimates from ERA-Interim/Land and in situ measurements from the International Soil Moisture Network using the European Space Agency’s (ESA’s) current Climate Change Initiative—Soil Moisture (ESA CCI SM) product version v02.3 as benchmark merging scheme. Results show that the $p$ -value classification provides a robust basis for decisions regarding using either active or passive data alone, or an unweighted average in cases where relative weights cannot be estimated reliably, and that the weights estimated from TCA in almost all cases outperform the ternary decision upon which the ESA CCI SM v02.3 is based. The proposed method forms the basis for the new ESA CCI SM product version v03.x and higher.
25 Jun 2017
TL;DR: In this article, a chiral interaction between single quantum emitters and transversally confined photons was observed in a whispering gallery mode microresonator, where the emission direction of light into the structure is controlled by the polarization of the excitation light or by the internal quantum state of the emitter.
Abstract: Controlling the interaction of light and matter is the basis for diverse applications ranging from light technology to quantum information processing. Nowadays, many of these applications are based on nanophotonic structures. It turns out that the confinement of light in such nanostructures imposes an inherent link between its local polarization and its propagation direction, also referred to as spin-momentum locking of light [1]. Remarkably, this leads to chiral, i.e., propagation direction-dependent effects in the emission and absorption of light, and elementary processes of light-matter interaction are fundamentally altered. For example, when coupling plasmonic particles or atoms to evanescent fields, the intrinsic mirror symmetry of the particles' emission can be broken. In our group, we observed this effect in the interaction between single rubidium atoms and the evanescent part of a light field that is confined by continuous total internal reflection in a whispering-gallery-mode microresonator [2]. In the following, this allowed us to realize chiral nanophotonic interfaces in which the emission direction of light into the structure is controlled by the polarization of the excitation light [3] or by the internal quantum state of the emitter [4], respectively. Moreover, we employed this chiral interaction to demonstrate an integrated optical isolator [5] as well as an integrated optical circulator [6] which operate at the single-photon level and which exhibit low loss. The latter are the first two examples of a new class of nonreciprocal nanophotonic devices which exploit the chiral interaction between single quantum emitters and transversally confined photons.
TL;DR: In this paper, a novel technique to separate high and fluctuating amounts of hydrogen sulphide from raw biogas is presented that relies on a highly intensified method of chemical-oxidative scrubbing.
TL;DR: A conceptual model capable of displaying an overview of the stakeholders taking part in the initiative in relation to the projects developed and the challenges they face is developed and applied to the case of the Vienna Smart City strategy.
TL;DR: In this article, the photon-energy-dependent emission timing of electrons, released from the helium ground state by an extreme-ultraviolet photon, either leaving the ion in its ground state or exciting it into a shake-up state.
Abstract: Photoemission of an electron is commonly treated as a one-particle phenomenon. With attosecond streaking spectroscopy we observe the breakdown of this single active-electron approximation by recording up to six attoseconds retardation of the dislodged photoelectron due to electronic correlations. We recorded the photon-energy-dependent emission timing of electrons, released from the helium ground state by an extreme-ultraviolet photon, either leaving the ion in its ground state or exciting it into a shake-up state. We identify an optical field-driven d.c. Stark shift of charge-asymmetric ionic states formed after the entangled photoemission as a key contribution to the observed correlation time shift. These findings enable a complete wavepacket reconstruction and are universal for all polarized initial and final states. Sub-attosecond agreement with quantum mechanical ab initio modelling allows us to determine the absolute zero of time in the photoelectric effect to a precision better than 1/25th of the atomic unit of time. Photoemission is not a simple process and it is not instantaneous. Delays of a few attoseconds have now been measured in helium and it seems that they are partly due to electronic correlations.
TL;DR: An overview of the almaBTE program structure is given and illustrative examples for some of its uses are presented, especially well suited to investigate novel materials and structures.
TL;DR: In this paper, a review of perovskite oxides to design and optimize next generation solar-to-fuel conversion materials operating on thermochemical cycles is presented, where the lattice structure and defect thermodynamics towards CO2 and water splitting are discussed.
Abstract: Thermochemical water and carbon dioxide splitting with concentrated solar energy is a technology for converting renewable solar energy into liquid hydrocarbon fuels as an alternative to fossil fuels, which are dominating in today's energy mix. For the conversion reaction to be efficient, special redox materials are necessary to perform the necessary chemical reactions in a thermochemical cycle. Through this review we carefully examine perovskite oxides to design and optimize next generation solar-to-fuel conversion materials operating on thermochemical cycles. To date efforts have primarily been directed to binary oxides among which most prominently ceria was selected. Despite the promise, ceria has an unfavorable high reduction temperature and is restricted in its opportunities to manipulate through extrinsic doping the oxygen nonstoichiometry and thermodynamic properties for oxygen exchange towards H2O and CO2 splitting. In contrast, recent reports highlight new opportunities to use and alter perovskite oxides in terms of elemental composition over a wider range to affect reduction temperature, oxygen exchange characteristics needed in the catalytic reactions and fuel yield. To further foster perovskites for solar-to-fuel conversion, we review basic concepts such as the lattice structure and defect thermodynamics towards CO2 and water splitting, discuss the role of oxygen vacancies and present strategies for an efficient search for new perovskite compositions. Summarizing, recent efforts on perovskite oxide compositions investigated are based on Fe, Mn, Co, or Cr with reported fuel yields of up to several hundred μmol per g per cycle in the literature. This article reviews the underlying principles, the latest advances and future prospects of perovskite oxides for solar-to-fuel technology.
TL;DR: This work studies a pair of tunnel-coupled one-dimensional atomic superfluids and characterize the corresponding quantum many-body problem by measuring correlation functions and concludes that in thermal equilibrium this system can be seen as a quantum simulator of the sine-Gordon model, relevant for diverse disciplines ranging from particle physics to condensed matter.
Abstract: Quantum systems can be characterized by their correlations Higher-order (larger than second order) correlations, and the ways in which they can be decomposed into correlations of lower order, provide important information about the system, its structure, its interactions and its complexity The measurement of such correlation functions is therefore an essential tool for reading, verifying and characterizing quantum simulations Although higher-order correlation functions are frequently used in theoretical calculations, so far mainly correlations up to second order have been studied experimentally Here we study a pair of tunnel-coupled one-dimensional atomic superfluids and characterize the corresponding quantum many-body problem by measuring correlation functions We extract phase correlation functions up to tenth order from interference patterns and analyse whether, and under what conditions, these functions factorize into correlations of lower order This analysis characterizes the essential features of our system, the relevant quasiparticles, their interactions and topologically distinct vacua From our data we conclude that in thermal equilibrium our system can be seen as a quantum simulator of the sine-Gordon model, relevant for diverse disciplines ranging from particle physics to condensed matter The measurement and evaluation of higher-order correlation functions can easily be generalized to other systems and to study correlations of any other observable such as density, spin and magnetization It therefore represents a general method for analysing quantum many-body systems from experimental data
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam +2325 more•Institutions (191)
TL;DR: In this paper, an upper bound on the branching fraction of the Higgs boson decay to invisible particles, as a function of the assumed production cross-sections, was established, and the results were also interpreted in the context of Higgs-portal dark matter models.
Abstract: Searches for invisible decays of the Higgs boson are presented. The data collected with the CMS detector at the LHC correspond to integrated luminosities of 5.1, 19.7, and 2.3 fb−1 at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The search channels target Higgs boson production via gluon fusion, vector boson fusion, and in association with a vector boson. Upper limits are placed on the branching fraction of the Higgs boson decay to invisible particles, as a function of the assumed production cross sections. The combination of all channels, assuming standard model production, yields an observed (expected) upper limit on the invisible branching fraction of 0.24 (0.23) at the 95% confidence level. The results are also interpreted in the context of Higgs-portal dark matter models.
TL;DR: Learning factories present a promising environment for education, training and research, especially in manufacturing related areas which are a main driver for wealth creation in any nation as mentioned in this paper. But, while n...
TL;DR: In this article, the Intrinsic Heat Treatment (IHT) was exploited to induce the precipitation of NiAl nanoparticles in an Fe-19Ni-xAl (at%) model maraging steel, a system known for rapid clustering.
30 Oct 2017
TL;DR: In this paper, the authors present Fulgor and Rayo, a payment protocol for PCNs that provides provable privacy guarantees for PCN and is fully compatible with the Bitcoin scripting system, but it is a blocking protocol and therefore prone to deadlocks of concurrent payments as in currently available PCNs.
Abstract: Permissionless blockchains protocols such as Bitcoin are inherently limited in transaction throughput and latency. Current efforts to address this key issue focus on off-chain payment channels that can be combined in a Payment-Channel Network (PCN) to enable an unlimited number of payments without requiring to access the blockchain other than to register the initial and final capacity of each channel. While this approach paves the way for low latency and high throughput of payments, its deployment in practice raises several privacy concerns as well as technical challenges related to the inherently concurrent nature of payments that have not been sufficiently studied so far. In this work, we lay the foundations for privacy and concurrency in PCNs, presenting a formal definition in the Universal Composability framework as well as practical and provably secure solutions. In particular, we present Fulgor and Rayo. Fulgor is the first payment protocol for PCNs that provides provable privacy guarantees for PCNs and is fully compatible with the Bitcoin scripting system. However, Fulgor is a blocking protocol and therefore prone to deadlocks of concurrent payments as in currently available PCNs. Instead, Rayo is the first protocol for PCNs that enforces non-blocking progress (i.e., at least one of the concurrent payments terminates). We show through a new impossibility result that non-blocking progress necessarily comes at the cost of weaker privacy. At the core of Fulgor and Rayo is Multi-Hop HTLC, a new smart contract, compatible with the Bitcoin scripting system, that provides conditional payments while reducing running time and communication overhead with respect to previous approaches. Our performance evaluation of Fulgor and Rayo shows that a payment with 10 intermediate users takes as few as 5 seconds, thereby demonstrating their feasibility to be deployed in practice.
University of Sydney1, North Carolina State University2, University of South Carolina3, Macquarie University4, RMIT University5, Rochester Institute of Technology6, University of New South Wales7, University of Michigan8, Qatar Computing Research Institute9, University of Trento10, Southeast University11, Swinburne University of Technology12, Sun Yat-sen University13, Commonwealth Scientific and Industrial Research Organisation14, Texas A&M University15, Qatar University16, University of Miami17, Vienna University of Technology18, University of Stuttgart19, Tilburg University20
TL;DR: Mapping out the challenges and strategies for the widespread adoption of service computing shows clear trends in adoption and a clear road map for the future direction is proposed.
Abstract: Mapping out the challenges and strategies for the widespread adoption of service computing.