The analysis of paths in graphs is highly relevant in many domains. Typically, path‐related tasks are performed in node‐link layouts. Unfortunately, graph layouts often do not scale to the size of ...many real world networks. Also, many networks are multivariate, i.e., contain rich attribute sets associated with the nodes and edges. These attributes are often critical in judging paths, but directly visualizing attributes in a graph layout exacerbates the scalability problem. In this paper, we present visual analysis solutions dedicated to path‐related tasks in large and highly multivariate graphs. We show that by focusing on paths, we can address the scalability problem of multivariate graph visualization, equipping analysts with a powerful tool to explore large graphs. We introduce Pathfinder, a technique that provides visual methods to query paths, while considering various constraints. The resulting set of paths is visualized in both a ranked list and as a node‐link diagram. For the paths in the list, we display rich attribute data associated with nodes and edges, and the node‐link diagram provides topological context. The paths can be ranked based on topological properties, such as path length or average node degree, and scores derived from attribute data. Pathfinder is designed to scale to graphs with tens of thousands of nodes and edges by employing strategies such as incremental query results. We demonstrate Pathfinder's fitness for use in scenarios with data from a coauthor network and biological pathways.
Enabling parallel computing in crash Partl, A. M.; Maselli, A.; Ciardi, B. ...
Monthly Notices of the Royal Astronomical Society,
06/2011, Letnik:
414, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present the new parallel version (pcrash2) of the cosmological radiative transfer code crash2 for distributed memory supercomputing facilities. The code is based on a static domain decomposition ...strategy inspired by geometric dilution of photons in the optical thin case that ensures a favourable performance speed-up with an increasing number of computational cores. Linear speed-up is ensured as long as the number of radiation sources is equal to the number of computational cores or larger. The propagation of rays is segmented and rays are only propagated through one sub-domain per time-step to guarantee an optimal balance between communication and computation. We have extensively checked pcrash2 with a standardized set of test cases to validate the parallelization scheme. The parallel version of crash2 can easily handle the propagation of radiation from a large number of sources and is ready for the extension of the ionization network to species other than hydrogen and helium.
The nature of blending of virgin materials with reclaimed asphalt pavement (RAP) has been investigated using a multi scale approach using the dynamic shear rheometer (DSR), electron microscopy and ...computer tomography (CT). In order to simplify the visualization of the blending of the virgin and reclaimed materials five specially engineered hot asphalt mixtures were produced incorporating large mineral fraction (8/11mm) of virgin aggregates and small fraction (2/4mm) from RAP mixed with virgin bitumen. The complex modulus and phase angle of reclaimed binder from the blended mixtures were found to be between that of RAP and virgin binder. The CT slices of compacted cylindrical samples (150mm diameter×120mm height) could incorporate the effect of compaction on the blending. They show lumped regions with virgin large aggregates as well as lumped regions of RAP aggregates. Using micro CT the spatial distribution of the different binders was investigated at the micro-scale. Millimeter size distinct clusters of virgin binder and clusters of RAP binder could be distinguished. The existence of RAP binder next to large virgin aggregates indicated the migration of the old RAP binder from the RAP aggregates to the virgin aggregates. From these CT images, it was not possible to verify if blending between the virgin and old binders occurred. Using electron microscopy micro-crack formations in the zone between old and new binder were identified suggesting weak spots that could lead to larger crack formation and propagation. However, using energy-dispersive X-ray spectroscopy good qualitative distribution of titanium dioxide tracer in the virgin binder in the mixture could be seen, indicating good blending at the investigated location. Hence, the results show that blending is not homogeneous throughout the sample. Some locations show good blending whereas other locations appear non-blended with micro-cracks forming at the binder boundaries.
During the last 50 years, Rilem was continuously active in pre-standardization efforts aiming at gradually improving scientific and technological testing and analysis methods for refined ...understanding and characterization of bituminous binders and asphalt, both under well-defined laboratory and performance driven in-field conditions. This paper intends to highlight and provide a short overview on the international activities of Rilem’s to date 18 technical committees (TC) on asphalt and bituminous binders. After some general background information, underlining the specific complexity of asphalt pavement materials in terms of rheological behavior and basic structural functioning, it is shown that these activities resulted in numerous recommendations, state of the art reports and conference proceedings, all produced on a voluntary basis by scientific and technical commitment of individual experts. This wealth of results was created by the TCs following an own systematic methodology for many years which, at the end of the day, allowed building up activities through the new TCs of today in a much more specialized but at the same time also more diverse way. In view of this new flexibility and keeping in mind the previous success story of Rilem towards improved testing of asphalt pavements, future developments, challenges and interdisciplinary issues regarding bituminous road materials are outlined as potential starting point for future TC initiatives.
Reclaimed asphalt pavement (RAP) is harder than virgin bitumen due to ageing and it needs to be rejuvenated. Three bio-based rejuvenators are used and the rejuvenating effects are evaluated. ...Rheological tests show how the rejuvenators may restore the mechanical properties of RAP binder. An ageing index is proposed to show that the rejuvenators are affected differently by ageing. Despite their addition, physio-chemical oxidation did not reverse. Mechanical changes were not caused by chemical changes at functional groups level but a rearrangement of polar/nonpolar components. The results show that considering the effect of aging is vital in identifying how rejuvenators affect the RAP binder chemically and mechanically.
Display omitted
•Bio-based rejuvenators were able to restore the mechanical properties of RAP binder.•Ageing index demonstrated how various rejuvenators had a different impact on the aged RAP.•No changes at functional groups level was seen after rejuvenation.•Due to ageing a rearrangement of polar/nonpolar components was observed.
Display omitted
•CR blending properties with bitumen are highly influenced by the production process of CR.•High pressure water jet technology produces CR with rougher and larger surface area.•Larger ...rubber particle size (<1000 µm) increased the cold temperatures ductility.•CR increased modulus at higher temperatures and lowered it at lower temperatures.
The quality of the bitumen modified with crumb rubber (CR) largely depends on the process parameters when blending CR with bitumen. The larger the specific surface of the CR particles, the better the final properties of the CR-modified bitumen. A novel high-pressure water jet (WJ) based technology has been shown to produce CR with a rougher and larger surface area compared to other traditional techniques such as mechanical shredding (ME) or cryogenic processing (CG). This, in turn, resulted in superior low temperature properties when used as modifier in bitumen. Specifically, the results showed a clear tendency of WJ technology to improve the strength in fracture toughness tests at −10 °C more so than CG and ME. The larger rubber particle size (<1000 µm) the higher the ductility of the material investigated showing improved performance under cold temperatures. From the rheological analysis, it can be concluded that addition of CR to bitumen increases the complex modulus at high temperatures and reduces stiffness at low temperatures. In comparison to SBS polymer modified bitumen there is a flattening of the complex modulus curve indicating less temperature susceptibility. This implies enhanced rutting resistance at high temperatures and enhanced low temperature cracking resistance at low temperatures for CR modified bitumen compared to neat and SBS modified bitumen.
Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and ...indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use.
•Waste materials in the urban and peri-urban environment is reviewed and quantified.•Waste materials suitable for re-use in roads reviewed.•Many waste materials have similar or superior properties to ...virgin materials used in roads.•It is estimated that 16% of the available waste quantities in Europe could be recycled in roads.•Use of waste materials in roads can lead to significant cost, CO2 and energy savings.
This paper demonstrates how a considerable amount of waste produced in the urban and peri-urban environment can be recycled in asphalt roads. The example presented is from Europe, however, the barriers and conclusions are universal. It was shown that various waste materials such as glass, asphalt, concrete, wood, plastics etc. have a potential for re-use in asphalt roads. The available quantities of the European target waste materials that would otherwise be incinerated or disposed in landfills were considered. It was shown that there is high potential in Europe for recycling in road construction, in particular, under the hypothetical scenario where 33% of new roads would be made of the target waste materials (excluding RAP which is already recycled), it is estimated that 16% of the available waste quantities could be recycled in roads. Four hypothetical roads were analysed showing a considerable savings in costs, CO2 and energy in comparison to conventional asphalt mixtures using all virgin components.
Reclaimed asphalt pavement (RAP) is stiffer than the virgin material due to aging, thus it is expected to have worse cracking resistance. By adding bio-based rejuvenators, RAP binder mechanical ...performances at low temperatures improve: fracture toughness temperature of RAP decreases after the addition of rejuvenators to a level similar to the virgin binder. Furthermore, work to fracture of RAP binder increases after the addition of rejuvenators. Addition of rejuvenators to RAP binder can restore both mechanical properties and toughness at low temperature. However, despite the rejuvenators’ addition, physio-chemical oxidation did not reverse as mechanical changes were not caused by chemical changes at functional groups level. Results confirmed how considering the effect of aging is crucial when studying how rejuvenators affect the RAP binder chemically and mechanically.
Display omitted
•Fracture toughness transition temperature of RAP decreases after the addition of rejuvenators.•After the addition of rejuvenators, work up to fracture of RAP improves.•Bio-based rejuvenators are able to restore the mechanical properties of RAP binder.•The viscoelastic characteristics depend on aging and can be influenced by RAP's rejuvenators.•Mechanical changes due to rejuvenators were not caused by changes at chemical bonds/functional groups level.
PDF
