Showing papers by "Vienna University of Technology published in 2007"

A survey on context-aware systems

Abstract: Context-aware systems offer entirely new opportunities for application developers and for end users by gathering context data and adapting systems behaviour accordingly. Especially in combination with mobile devices, these mechanisms are of high value and are used to increase usability tremendously. In this paper, we present common architecture principles of context-aware systems and derive a layered conceptual design framework to explain the different elements common to most context-aware architectures. Based on these design principles, we introduce various existing context-aware systems focusing on context-aware middleware and frameworks, which ease the development of context-aware applications. We discuss various approaches and analyse important aspects in context-aware computing on the basis of the presented systems.

Service-Oriented Computing: State of the Art and Research Challenges

Abstract: Service-oriented computing promotes the idea of assembling application components into a network of services that can be loosely coupled to create flexible, dynamic business processes and agile applications that span organizations and computing platforms An SOC research road map provides a context for exploring ongoing research activities

‘Click’ Chemistry in Polymer and Materials Science

Abstract: The modification of polymers after the successful achievement of a polymerization process represents an important task in macromolecular science. Cycloaddition reactions, among them the metal catalyzed azide/alkyne ‘click’ reaction (a variation of the Huisgen 1,3-dipolar cycloaddition reaction between terminal acetylenes and azides) represents an important contribution towards this endeavor. They combine high efficiency (usually above 95%) with a high tolerance of functional groups and solvents, as well as moderate reaction temperatures (25–70 °C). The present review assembles recent literature for applications of this reaction in the field of polymer science (linear polymers, dendrimers, gels) as well as the use of this and related reactions for surface modification on carbon nanotubes, fullerenes, and on solid substrates, and includes the authors own publications in this field. A number of references (>100) are included.

Ultramicroscopy: three-dimensional visualization of neuronal networks in the whole mouse brain.

Abstract: Visualizing entire neuronal networks for analysis in the intact brain has been impossible up to now. Techniques like computer tomography or magnetic resonance imaging (MRI) do not yield cellular resolution, and mechanical slicing procedures are insufficient to achieve high-resolution reconstructions in three dimensions. Here we present an approach that allows imaging of whole fixed mouse brains. We modified 'ultramicroscopy' by combining it with a special procedure to clear tissue. We show that this new technique allows optical sectioning of fixed mouse brains with cellular resolution and can be used to detect single GFP-labeled neurons in excised mouse hippocampi. We obtained three-dimensional (3D) images of dendritic trees and spines of populations of CA1 neurons in isolated hippocampi. Also in fruit flies and in mouse embryos, we were able to visualize details of the anatomy by imaging autofluorescence. Our method is ideally suited for high-throughput phenotype screening of transgenic mice and thus will benefit the investigation of disease models.

Non-equilibrium coherence dynamics in one-dimensional bose gases

Abstract: This paper reports a direct experimental study of the coherence dynamics in both isolated and coupled degenerate one-dimensional (1D) Bose gases. Completely isolated 1D Bose gases exhibit coherence decay in excellent agreement with recent predictions. The coherence of two coupled 1D Bose gases decays to a finite value, analogous to the phase locking of two lasers by injection. Low-dimensional systems provide beautiful examples of many-body quantum physics1. For one-dimensional (1D) systems2, the Luttinger liquid approach3 provides insight into universal properties. Much is known of the equilibrium state, both in the weakly4,5,6,7 and strongly8,9 interacting regimes. However, it remains a challenge to probe the dynamics by which this equilibrium state is reached10. Here we present a direct experimental study of the coherence dynamics in both isolated and coupled degenerate 1D Bose gases. Dynamic splitting is used to create two 1D systems in a phase coherent state11. The time evolution of the coherence is revealed through local phase shifts of the subsequently observed interference patterns. Completely isolated 1D Bose gases are observed to exhibit universal sub-exponential coherence decay, in excellent agreement with recent predictions12. For two coupled 1D Bose gases, the coherence factor is observed to approach a non-zero equilibrium value, as predicted by a Bogoliubov approach13. This coupled-system decay to finite coherence is the matter wave equivalent of phase-locking two lasers by injection. The non-equilibrium dynamics of superfluids has an important role in a wide range of physical systems, such as superconductors, quantum Hall systems, superfluid helium and spin systems14,15,16. Our experiments studying coherence dynamics show that 1D Bose gases are ideally suited for investigating this class of phenomena.

Short Note: A global model of pressure and temperature for geodetic applications

Abstract: The empirical model GPT (Global Pressure and Temperature), which is based on spherical harmonics up to degree and order nine, provides pressure and temperature at any site in the vicinity of the Earth’s surface. It can be used for geodetic applications such as the determination of a priori hydrostatic zenith delays, reference pressure values for atmospheric loading, or thermal deformation of Very Long Baseline Interferometry (VLBI) radio telescopes. Input parameters of GPT are the station coordinates and the day of the year, thus also allowing one to model the annual variations of the parameters. As an improvement compared with previous models, it reproduces the large pressure anomaly over Antarctica, which can cause station height errors in the analysis of space-geodetic data of up to 1 cm if not considered properly in troposphere modelling. First tests at selected geodetic observing stations show that the pressure biases considerably decrease when using GPT instead of the very simple approaches applied to various Global Navigation Satellite Systems (GNSS) software packages so far. GPT also provides an appropriate model for the annual variability of global temperature.

Cross Site Scripting Prevention with Dynamic Data Tainting and Static Analysis.

Abstract: Cross-site scripting (XSS) is an attack against web applications in which scripting code is injected into the output of an application that is then sent to a user’s web browser In the browser, this scripting code is executed and used to transfer sensitive data to a third party (ie, the attacker) Currently, most approaches attempt to prevent XSS on the server side by inspecting and modifying the data that is exchanged between the web application and the user Unfortunately, it is often the case that vulnerable applications are not fixed for a considerable amount of time, leaving the users vulnerable to attacks The solution presented in this paper stops XSS attacks on the client side by tracking the flow of sensitive information inside the web browser If sensitive information is about to be transferred to a third party, the user can decide if this should be permitted or not As a result, the user has an additional protection layer when surfing the web, without solely depending on the security of the web application

Survey of channel and radio propagation models for wireless MIMO systems

Abstract: This paper provides an overview of the state-of-the-art radio propagation and channel models for wireless multiple-input multiple-output (MIMO) systems. We distinguish between physical models and analytical models and discuss popular examples from both model types. Physical models focus on the double-directional propagation mechanisms between the location of transmitter and receiver without taking the antenna configuration into account. Analytical models capture physical wave propagation and antenna configuration simultaneously by describing the impulse response (equivalently, the transfer function) between the antenna arrays at both link ends. We also review some MIMO models that are included in current standardization activities for the purpose of reproducible and comparable MIMO system evaluations. Finally, we describe a couple of key features of channels and radio propagation which are not sufficiently included in current MIMO models.

New materials for micro-scale sensors and actuators An engineering review

Abstract: This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.

Correction of laser scanning intensity data: Data and model-driven approaches

Abstract: Most airborne and terrestrial laser scanning systems additionally record the received signal intensity for each measurement. Multiple studies show the potential of this intensity value for a great variety of applications (e.g. strip adjustment, forestry, glaciology), but also state problems if using the original recorded values. Three main factors, a) spherical loss, b) topographic and c) atmospheric effects, influence the backscatter of the emitted laser power, which leads to a noticeably heterogeneous representation of the received power. This paper describes two different methods for correcting the laser scanning intensity data for these known influences resulting in a value proportional to the reflectance of the scanned surface. The first approach – data-driven correction – uses predefined homogeneous areas to empirically estimate the best parameters (least-squares adjustment) for a given global correction function accounting for all range-dependent influences. The second approach – model-driven correction – corrects each intensity independently based on the physical principle of radar systems. The evaluation of both methods, based on homogeneous reflecting areas acquired at different heights in different missions, indicates a clear reduction of intensity variation, to 1/3.5 of the original variation, and offsets between flight strips to 1/10. The presented correction methods establish a great potential for laser scanning intensity to be used for surface classification and multi-temporal analyses.

Source apportionment of PM2.5 organic aerosol over Europe: Primary/secondary, natural/anthropogenic, and fossil/biogenic origin

Abstract: On the basis of a 2-year comprehensive data set obtained within the CARBOSOL project, seasonal source apportionment of PM2.5 aerosol is attempted for five rural/remote sites in Europe. The approach developed combines radiocarbon measurements with bulk measurements of organic carbon (OC), elemental carbon (EC), and two organic tracers ( levoglucosan and cellulose). Source types are lumped into primary emissions from fossil fuel combustion and biomass burning, bioaerosol, and secondary organic aerosol from precursors emitted by fossil and nonfossil sources. Bulk concentration ratios reported for these source types in the literature are used to estimate the source contributions which are constrained by measured radiocarbon concentrations. It has been found that while fossil-related sources predominate EC throughout the year at all sites, the sources of OC are primarily biogenic and markedly different between summer and winter. In winter biomass burning primary emission is the main source, with sizable additional contribution from fossil fuel combustion. In contrast, in summer secondary organic aerosol (SOA) from nonfossil sources becomes predominant (63-76% of TC), with some contribution of SOA from fossil fuel combustion. The results agree well with recent findings of other authors who established the predominance of biogenic SOA for rural sites in summer in Europe. An uncertainty analysis has been conducted, which shows that the main conclusions from this study are robust.

Operational readiness of microwave remote sensing of soil moisture for hydrologic applications

Abstract: Microwave remote sensing of soil moisture has been an active area of research since the 1970s but has yet found little use in operational applications Given recent advances in retrieval algorithms and the approval of a dedicated soil moisture satellite, it is time to re-assess the potential of various satellite systems to provide soil moisture information for hydrologic applications in an operational fashion This paper reviews recent progress made with retrieving surface soil moisture from three types of microwave sensors - radiometers, Synthetic Aperture Radars (SARs), and scatterometers The discussion focuses on the operational readiness of the different techniques, considering requirements that are typical for hydrological applications It is concluded that operational coarse-resolution (25-50 km) soil moisture products can be expected within the next few years from radiometer and scatterometer systems, while scientific and technological breakthroughs are still needed for operational soil moisture retrieval at finer scales (< 1 km) from SAR Also, further research on data assimilation methods is needed to make best use of the coarse-resolution surface soil moisture data provided by radiometer and scatterometer systems in a hydrologic context and to fully assess the value of these data for hydrological predictions

COFI RANK - Maximum Margin Matrix Factorization for Collaborative Ranking

Abstract: In this paper, we consider collaborative filtering as a ranking problem. We present a method which uses Maximum Margin Matrix Factorization and optimizes ranking instead of rating. We employ structured output prediction to optimize directly for ranking scores. Experimental results show that our method gives very good ranking scores and scales well on collaborative filtering tasks.

Initial soil moisture retrievals from the METOP-A Advanced Scatterometer (ASCAT)

Abstract: [1] This article presents first results of deriving relative surface soil moisture from the METOP-A Advanced Scatterometer. Retrieval is based on a change detection approach which has originally been developed for the Active MicrowaveInstrument flownonboardtheEuropeansatellites ERS-1 and ERS-2. Using model parameters derived from eight years of ERS scatterometer data, first global soil moisture maps have been produced from ASCAT data. The ASCAT data were distributed by EUMETSAT for validation purposes during the ASCAT product commissioning activities. Several recent cases of drought and excessive rainfall are clearly visible in the soil moisture data. The results confirm that seamless soil moisture time series can be expected from the series of two ERS and three METOP scatterometers, providing global coverage on decadal time scales (from 1991 to about 2021). Thereby, operational, nearreal-time ASCAT soil moisture products will become available for weather prediction and hydrometeorological applications. Citation: Bartalis, Z., W. Wagner, V. Naeimi, S. Hasenauer, K. Scipal, H. Bonekamp, J. Figa, and C. Anderson (2007), Initial soil moisture retrievals from the METOP-A Advanced Scatterometer (ASCAT), Geophys. Res. Lett., 34, L20401, doi:10.1029/2007GL031088.

Levoglucosan levels at background sites in Europe for assessing the impact of biomass combustion on the European aerosol background

Abstract: Atmospheric levoglucosan has been determined as a proxy for “biomass smoke” in samples from six background stations on a west–east transect extending from the Atlantic (Azores) to the mid-European background site KPZ (K-Puszta, Hungary). Concentration levels of levoglucosan (biannual averages) in the west–east transect range from 0.005 μg/m3 at the oceanic background site AZO (Azores) to 0.52 μg/m3 at AVE (Aveiro, Portugal). The atmospheric concentration of “biomass smoke” (biannual averages) was derived from the levoglucosan data with wood-type-specific conversion factors. Annual averages of wood smoke levels ranged from 0.05 μg/m3 at AZO to 4.3 μg/m3 at AVE. Winter (DJF) averages at the low-level sites AVE and KPZ were 10.8 and 6.7 μg/m3, respectively. Relative contributions of biomass smoke to organic matter (OM) range from around 9–11% at the elevated sites SIL, PDD and SBO, as well as for AZO, to 36% at the low-level site AVE and 28% at KPZ. Surprisingly high relative concentrations of biomass smoke in OM (68 and 47%) were observed for wintry conditions at the continental low-level CARBOSOL sites AVE and KPZ. Thus biomass smoke is a very important constituent of the organic material in the mid and west European background with summer contributions to organic matter of around 1–6% and winter levels of around 20% at the elevated mountain sites and 47–68% at rural flat terrain sites, not including secondary organic aerosol from biomass combustion sources.

Novel Three-Phase AC–AC Sparse Matrix Converters

Abstract: A novel three-phase ac-ac sparse matrix converter having no energy storage elements and employing only 15 IGBTs, as opposed to 18 IGBTs of a functionally equivalent conventional ac-ac matrix converter, is proposed. It is shown that the realization effort could be further reduced to only nine IGBTs in an ultra sparse matrix converter (USMC) in the case where only unidirectional power flow is required and the fundamental phase displacement at the input and at the output is limited to plusmnpi/6. The dependency of the voltage and current transfer ratios of the sparse matrix converters on the operating parameters is analyzed and a space vector modulation scheme is described in combination with a zero current commutation method. Finally, the sparse matrix concept is verified by simulation and experimentally using a 6.8-kW/400-V very sparse matrix converter, which is implemented with 12 IGBT switches, and USMC prototypes.

Architectural Geometry

Abstract: Around 2005 it became apparent in the geometry processing community that freeform architecture contains many problems of a geometric nature to be solved, and many opportunities for optimization which however require geometric understanding. This area of research, which has been called architectural geometry, meanwhile contains a great wealth of individual contributions which are relevant in various fields. For mathematicians, the relation to discrete differential geometry is significant, in particular the integrable system viewpoint. Besides, new application contexts have become available for quite some old-established concepts. Regarding graphics and geometry processing, architectural geometry yields interesting new questions but also new objects, e.g. replacing meshes by other combinatorial arrangements. Numerical optimization plays a major role but in itself would be powerless without geometric understanding. Summing up, architectural geometry has become a rewarding field of study. We here survey the main directions which have been pursued, we show real projects where geometric considerations have played a role, and we outline open problems which we think are significant for the future development of both theory and practice of architectural geometry. Graphical abstractDisplay Omitted HighlightsThis is a survey paper on 'architectural geometry' as a geometric discipline, together with references to real projects.

PWM Converter Power Density Barriers

Abstract: Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for a continuation of this trend. For identifying and quantifying such technological barriers this paper investigates the volume of the cooling system and of the main passive components for the basic forms of power electronics energy conversion in dependency of the switching frequency and determines switching frequencies minimizing the total volume. The analysis is for 5 kW rated output power, high performance air cooling, advanced power semiconductors, and single systems in all cases. A power density limit of 28 kW/dm3@300 kHz is calculated for an isolated DC-DC converter considering only transformer, output inductor and heat sink volume. For single-phase AC-DC conversion a general limit of 35 kW/dm3 results from the DC link capacitor required for buffering the power fluctuating with twice the mains frequency. For a three-phase unity power factor PWM rectifier the limit is 45 kW/dm3@810 kHz just taking into account EMI filter and cooling system. For the sparse matrix converter the limiting components are the input EMI filter and the common mode output inductor; the power density limit is 71 kW/dm3@50 kHz when not considering the cooling system. The calculated power density limits highlight the major importance of broadening the scope of research in power electronics from traditional areas like converter topologies, and modulation and control concepts to cooling systems, high frequency electromagnetics, interconnection technology, multi-functional integration, packaging and multi-domain modeling and simulation to ensure further advancement of the field along the power density trajectory.

At what scales do climate variability and land cover change impact on flooding and low flows

Abstract: 1 Institute of Hydraulic and Water Resources Engineering, Vienna University of Technology, Karlsplatz 13, A-1040 Vienna, Austria 2 UMR HydroSciences Montpellier, France 3 UNESCO Division of Water Sciences, Paris, France 4 University of Vienna, Austria 5 USDA-ARS-SWRC, Tucson, AZ, USA 6 FIMCM-ESPOL, Campus Gustavo Galindo, Guayaquil, Ecuador 7 GeoForschungsZentrum Potsdam, Germany 8 CSIRO Land and Water, Glen Osmond, Australia 9 Slovak University of Technology, Bratislava, Slovakia

Driver models in automobile dynamics application

Abstract: Understanding the driver of an automobile has been attractive to researchers from many different disciplines for more than half a century. On the basis of their acquirements, models of the (human) driver have been developed to better understand, analyse and improve the combined couple of driver and automobile. Due to distinctive demands on the models in accordance with different kinds of applications, a variety of driver models is available. An overview of driver models is given with respect to their application and different methodical modelling approaches. The emphasis is put on the interest of engineers, who generally focus on the automobile (like design and optimization of vehicle components and the overall vehicle dynamics behaviour) by applying their approved (mathematical) methods. Nonetheless, a brief look beyond is added to better complete the view on the involved task of driving and driver modelling for automobile dynamics application.

Performance on molecules, surfaces, and solids of the Wu-Cohen GGA exchange-correlation energy functional

Abstract: We present the results of Kohn-Sham calculations on molecules, surfaces, and solids which were obtained using a recently proposed exchange-correlation energy functional [Z. Wu and R. E. Cohen, Phys. Rev. B 73, 235116 (2006)]. The Wu-Cohen (WC) functional, like the well-known PBE functional [J. P. Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)], is of the generalized gradient approximation form and was derived from the homogeneous electron gas and mathematical relations obeyed by the exact functional. The results on molecular systems show that among the functionals we tested, PBE remains superior for the energetics of covalent and noncovalent bonds. While this is not too surprising for noncovalent bonds due to the very good performance of PBE, unfortunately this holds also for covalent bonds, where PBE is a functional of rather poor quality. Calculations on transition-metal surfaces show that WC improves over local-density approximation (LDA) and PBE for the surface formation energy of $3d$ elements, while LDA is the best for heavier elements. In most cases, the lattice constant of solids as determined by the WC functional is in between the LDA and PBE results and on average closer to experiment. We show for each group of compounds which functional performs best and provide trends. In the particular case of lattice constants whose values are determined by weak interactions (e.g., the interlayer distance in graphite), the LDA functional is more accurate than the generalized gradient approximation functionals.

Geometric modeling in shape space

Abstract: We present a novel framework to treat shapes in the setting of Riemannian geometry. Shapes -- triangular meshes or more generally straight line graphs in Euclidean space -- are treated as points in a shape space. We introduce useful Riemannian metrics in this space to aid the user in design and modeling tasks, especially to explore the space of (approximately) isometric deformations of a given shape. Much of the work relies on an efficient algorithm to compute geodesics in shape spaces; to this end, we present a multi-resolution framework to solve the interpolation problem -- which amounts to solving a boundary value problem -- as well as the extrapolation problem -- an initial value problem -- in shape space. Based on these two operations, several classical concepts like parallel transport and the exponential map can be used in shape space to solve various geometric modeling and geometry processing tasks. Applications include shape morphing, shape deformation, deformation transfer, and intuitive shape exploration.

From Words to Numbers: How to Transform Qualitative Data into Meaningful Quantitative Results

Abstract: In proposing a procedure for transforming qualitative data into quantitative results, we address the manifold requests for discovery-oriented research in the business disciplines. We present a systematic classification of combined qualitative-quantitative research designs and argue in favor of the generalization model. We give guidelines for its implementation and provide a blueprint for systematically converting respondents' words into numbers that can be used for further (statistical) analyses. We delimit and discuss the stages of unitization, categorization, and coding. We also raise quality issues and propose relevant quality criteria in the transformation process. In particular, we suggest the intercoder consistency-matrix for determining the incisiveness of categories developed through content analysis. Finally, we demonstrate in an exemplary study how the blueprint can be applied and highlight the benefits of the proposed research design.

Magnetic properties and critical currents of MgB2

Abstract: This review focuses on the superconducting properties of MgB2 that are relevant for power applications. The reversible mixed state parameters are the most important, since they define the limiting conditions for loss-free currents: the transition temperature, the upper critical field and the depairing current. They also determine the flux pinning energy, the pinning force and the elastic properties of the flux line lattice and, therefore, strongly influence the critical current densities. The magnetic properties of magnesium diboride are anisotropic and influenced by the two different energy gaps of the σ- and π-bands. Whereas the transition temperature could not be enhanced significantly during the past five years, the upper critical field was considerably increased by impurity scattering or doping. Flux pinning is very weak in MgB2 single crystals and was only improved by irradiation techniques so far. In polycrystalline samples, grain boundary pinning seems to play the dominant role. High critical currents close to the theoretical limit were found in c-axis oriented thin films. The anisotropy of the upper critical field strongly reduces the critical currents in untextured MgB2 at high magnetic fields, where the supercurrents become highly percolative, since not all grains are superconducting anymore. The performance of polycrystalline wires and tapes was significantly improved during the past few years by increasing the upper critical field and by reducing its anisotropy. Pinning seems to be nearly optimized in many forms of this material, but the connectivity between the grains might be further improved.

Soil moisture from Operational Meteorological Satellites

Abstract: In recent years, unforeseen advances in monitoring soil moisture from operational satellite platforms have been made, mainly due to improved geophysical retrieval methods. In this study, four recently published soil-moisture datasets are compared with in-situ observations from the REMEDHUS monitoring network located in the semi-arid part of the Duero basin in Spain. The remotely sensed soil-moisture products are retrieved from (1) the Advanced Microwave Scanning Radiometer (AMSR-E), which is a passive microwave sensor on-board NASA’s Aqua satellite, (2) European Remote Sensing satellite (ERS) scatterometer, which is an active microwave sensor on-board the two ERS satellites and (3) visible and thermal images from the METEOSAT satellite. Statistical analysis indicates that three satellite datasets contribute effectively to the monitoring of trends in surface soil-moisture conditions, but not to the estimation of absolute soil-moisture values. These sensors, or rather their successors, will be flown on operational meteorological satellites in the near future. With further improvements in processing techniques, operational meteorological satellites will increasingly deliver high-quality soil-moisture data. This may be of particular interest for hydrogeological studies that investigate long-term processes such as groundwater recharge.

In-Depth Analysis of the Felder-Silverman Learning Style Dimensions

Abstract: Learning styles are increasingly being incorporated into technology-enhanced learning. Appropriately, a great deal of recent research work is occurring in this area. As more information and details about learning styles becomes available, learning styles can be better accommodated and integrated into all aspects of educational technology. The aim of this paper is to analyse data about learning styles with respect to the Felder-Silverman learning style model (FSLSM) in order to provide a more detailed description of learning style dimensions. The analyses show the most representative characteristics of each learning style dimension as well as how representative these characteristics are. As a result, we provide additional information about the learning style dimensions of FSLSM. This information is especially important when learning styles are incorporated in technology-enhanced learning.

Band gap calculations with Becke?Johnson exchange potential

Abstract: Recently, a simple analytical form for the exchange potential was proposed by Becke and Johnson. This potential, which depends on the kinetic-energy density, was shown to reproduce very well the shape of the exact exchange potential (obtained with the optimized effective potential method) for atoms. Calculations on solids show that the Becke–Johnson potential leads to a better description of band gaps of semiconductors and insulators with respect to the standard local density and Perdew–Burke–Ernzerhof approximations for the exchange–correlation potential. Comparison is also made with the values obtained with the Engel–Vosko exchange potential which was also developed using the exact exchange potential.

Climatology of aerosol composition (organic versus inorganic) at nonurban sites on a west-east transect across Europe

Abstract: in central Europe. Aerosols were analyzed for 210 Pb, inorganic ions, elemental (EC) and organic (OC) carbon, water soluble organic carbon (WSOC), macromolecular type (humic-like) organic substances (HULIS), C2–C5 diacids, cellulose, and levoglucosan. Pooled aerosol filters were also used for the identification of different families of organic compounds by gas chromatography/mass spectrometry, GC/MS, as well as 14 C determinations. The data resulted in a climatological overview of the aerosol composition over Europe in the various seasons, from west to east, and from the boundary layer to the free troposphere. The paper first summarizes the characteristics of the sites and collected samples and then focuses on the aerosol mass partitioning (mass closure, inorganic versus organic, EC versus OC, water soluble versus insoluble OC), giving an insight on the sources of carbonaceous aerosol present in rural and natural background areas in Europe. It also introduces the main role of other companion papers dealing with CARBOSOL aerosol data that are also presented in this issue.

Equilibria in heterogeneous nonmonotonic multi-context systems

Abstract: We propose a general framework for multi-context reasoning which allows us to combine arbitrary monotonic and nonmonotonic logics. Nonmonotonic bridge rules are used to specify the information flow among contexts. We investigate several notions of equilibrium representing acceptable belief states for our multi-context systems. The approach generalizes the heterogeneous monotonic multi-context systems developed by F. Giunchiglia and colleagues as well as the homogeneous nonmonotonic multi-context systems of Brewka, Serafini and Roelofsen.