425 research outputs found
Meeting the design challenges of nano-CMOS electronics: an introduction to an upcoming EPSRC pilot project
The years of âhappy scalingâ are over and the fundamental challenges that the semiconductor industry faces, at both technology and device level, will impinge deeply upon the design of future integrated circuits and systems. This paper provides an introduction to these challenges and gives an overview of the Grid infrastructure that will be developed as part of a recently funded EPSRC pilot project to address them, and we hope, which will revolutionise the electronics design industry
Evaluation of rumble strips at rural stop-controlled intersections in Texas
Major safety concerns are present at rural high speed intersections. When long uninterrupted tangents are located near rural intersections, the drivers can become inattentive to upcoming decision points. Traffic control devices could aid in mitigating these occurrences by warning drivers of upcoming decision points. One such device is transverse rumble strips, which act to provide motorists with an audible and tactile warning that their vehicle is approaching a decision point of critical importance to safety. The objective of this research was to determine if the presence of transverse rumble strips were an effective warning device for drivers approaching rural stop-controlled intersections. To evaluate the effectiveness of transverse rumble strips, vehicle speeds were measured at three locations along the approach to an intersection both before and after the installation of rumble strips. Vehicle speeds were measured at nine rural stop-controlled intersection sites in Texas. Overall, the installation of rumble strips generally produced small, but statistically significant (p ? 0.05), reductions in traffic speeds. There were some negative driver behavioral impacts (i.e., speed increases) that occurred after the installation of rumble strips. There were a few instances where speed change reductions of greater than 1 mph occurred, however, the overall trend was that speed change reductions were equal to or less than 1 mph. Although the rumble strips did not produce meaningful reductions in traffic speeds, they should still be considered based upon previous accident reductions and minimal installation costs
Predicting the incidence and timing of central nervous system disease in metastatic melanoma: Implications for surveillance and preventative therapy
Illusory perceptions of space and time preserve cross-saccadic perceptual continuity
When voluntary saccadic eye movements are made to a silently ticking clock, observers sometimes think that the second hand takes longer than normal to move to its next position. For a short period, the clock appears to have stopped (chronostasis). Here we show that the illusion occurs because the brain extends the percept of the saccadic target backwards in time to just before the onset of the saccade. This occurs every time we move the eyes but it is only perceived when an external time reference alerts us to the phenomenon. The illusion does not seem to depend on the shift of spatial attention that accompanies the saccade. However, if the target is moved unpredictably during the saccade, breaking perception of the target's spatial continuity, then the illusion disappears. We suggest that temporal extension of the target's percept is one of the mechanisms that 'fill in' the perceptual 'gap' during saccadic suppression. The effect is critically linked to perceptual mechanisms that identify a target's spatial stability
Low Friction Flows of Liquids at Nanopatterned Interfaces
With the recent important development of microfluidic systems,
miniaturization of flow devices has become a real challenge. Microchannels,
however, are characterized by a large surface to volume ratio, so that surface
properties strongly affect flow resistance in submicrometric devices. We
present here results showing that the concerted effect of wetting . properties
and surface roughness may considerably reduce friction of the fluid past the
boundaries. The slippage of the fluid at the channel boundaries is shown to be
drastically increased by using surfaces that are patterned at the nanometer
scale. This effect occurs in the regime where the surface pattern is partially
dewetted, in the spirit of the 'superhydrophobic' effects that have been
recently discovered at the macroscopic scales. Our results show for the first
time that, in contrast to the common belief, surface friction may be reduced by
surface roughness. They also open the possibility of a controlled realization
of the 'nanobubbles' that have long been suspected to play a role in
interfacial slippag
Evaluation of coupled finite element/meshfree method for a robust full-scale crashworthiness simulation of railway vehicles
The crashworthiness of a railway vehicle relates to its passive safety performance. Due to mesh distortion and difficulty in controlling the hourglass energy, conventional finite element methods face great challenges in crashworthiness simulation of large-scale complex railway vehicle models. Meshfree methods such as element-free Galerkin method offer an alternative approach to overcome those limitations but have proved time-consuming. In this article, a coupled finite element/meshfree method is proposed to study the crashworthiness of railway vehicles. A representative scenario, in which the leading vehicle of a high-speed train impacts to a rigid wall, is simulated with the coupled finite element/element-free Galerkin method in LS-DYNA. We have compared the conventional finite element method and the coupled finite element/element-free Galerkin method with the simulation results of different levels of discretization. Our work showed that coupled finite element/element-free Galerkin method is a suitable alternative of finite element method to handle the nonlinear deformation in full-size railway vehicle crashworthiness simulation. The coupled method can reduce the hourglass energy in finite element simulation, to produce robust simulation
Groups, organizations, families and movements: The sociology of social systems between interaction and society
KĂŒhl S. Groups, organizations, families and movements: The sociology of social systems between interaction and society. Systems Research and Behavioral Science. 2020;37(3):496-515.In enhancing a proposal by Luhmann, this contribution shows that it is possible to locate different types of systems between âfaceâtoâfaceâinteractionâ and âsocietyâ: groups, organizations, families and protest movements. The common ground of these is that they use membership to attribute persons to the system or not. However, they differ fundamentally in regard to how they understand membership. In contrast to Luhmann's differentiation between interaction, organization and society, it is not only possible to imagine different types of interlocking systems but also coequal combinations of and transitions between the different types of social systems
Genesis and development of an interfluvial peatland in the central Congo Basin since the Late Pleistocene
The central Congo Basin contains the largest known peatland complex in the tropics. Here we present a detailed multi-proxy record from a peat core, CEN-17.4, from the centre of a 45 km wide interfluvial peatland (Ekolongouma), the first record of its kind from the central Congo peatlands. We use pollen, charcoal, sedimentological and geochemical data to reconstruct the site's history from the late Pleistocene to the present day. Peat began accumulating at the centre of the peatland âŒ19,600 cal BP (âŒ17,500â20,400 cal BP, 95% confidence interval), and between âŒ9500 (9430â9535 cal BP) and 10,500 (10,310â10,660 cal BP) cal BP towards the margins. Pollen data from the peatland centre show that an initial grass- and sedge-dominated vegetation, which burned frequently, was replaced by a Manilkara-type dominated flooded forest at âŒ12,640 cal BP, replaced in turn by a more mixed swamp forest at âŒ9670 cal BP. Mixed swamp forest vegetation has persisted to the present day, with variations in composition and canopy openness likely caused at least in part by changes in palaeo-precipitation. Stable isotope data (ÎŽDn-C29-v&icecorr) indicate a large reduction in precipitation beginning âŒ5000 and peaking âŒ2000 cal BP, associated with the near-complete mineralization of several metres of previously accumulated peat and with a transition to a drier, more heliophilic swamp forest assemblage, likely with a more open canopy. Although the peatland and associated vegetation recovered from this perturbation, the strong response to this climatic event underlines the ecosystem's sensitivity to changes in precipitation. We find no conclusive evidence for anthropogenic activity in our record; charcoal is abundant only in the Pleistocene part of the record and may reflect natural rather than anthropogenic fires. We conclude that autogenic succession and variation in the amount and seasonality of precipitation have been the most important drivers of ecological change in this peatland since the late Pleistocene
A global perspective on marine photosynthetic picoeukaryote community structure
A central goal in ecology is to understand the factors affecting the temporal dynamics and spatial distribution of microorganisms and the underlying processes causing differences in community structure and composition. However, little is known in this respect for photosynthetic picoeukaryotes (PPEs), algae that are now recognised as major players in marine CO2 fixation. Here, we analysed dot blot hybridisation and cloningâsequencing data, using the plastid-encoded 16S rRNA gene, from seven research cruises that encompassed all four ocean biomes. We provide insights into global abundance, α- and ÎČ-diversity distribution and the environmental factors shaping PPE community structure and composition. At the class level, the most commonly encountered PPEs were Prymnesiophyceae and Chrysophyceae. These taxa displayed complementary distribution patterns, with peak abundances of Prymnesiophyceae and Chrysophyceae in waters of high (25:1) or low (12:1) nitrogen:phosphorus (N:P) ratio, respectively. Significant differences in phylogenetic composition of PPEs were demonstrated for higher taxonomic levels between ocean basins, using Unifrac analyses of clone library sequence data. Differences in composition were generally greater between basins (interbasins) than within a basin (intrabasin). These differences were primarily linked to taxonomic variation in the composition of Prymnesiophyceae and Prasinophyceae whereas Chrysophyceae were phylogenetically similar in all libraries. These data provide better knowledge of PPE community structure across the world ocean and are crucial in assessing their evolution and contribution to CO2 fixation, especially in the context of global climate change
- âŠ