55,885 research outputs found
Astrotech 21: A technology program for future astrophysics missions
The Astrotech 21 technology program is being formulated to enable a program of advanced astrophysical observatories in the first decade of the 21st century. This paper describes the objectives of Astrotech 21 and the process that NASA is using to plan and implement it. It also describes the future astrophysical mission concepts that have been defined for the twenty-first century and discusses some of the requirements that they will impose on information systems for space astrophysics
Quantitative risk analysis for road tunnels complying with EU regulations
Tunnels have improved the connection of regions within the European Commission (EC) and have been used lately as a catalyst for economic development of previously isolated regions. However, the increasing number of these important infrastructures is raising upfront an endogenous problem, which is the severity of accidents that may occur. These risks have much greater impact when heavy goods vehicles (HGVs) or dangerous goods (DGs) are involved in the accident. As a result, the EC launched the EC Directive 2004/54/EC. In order to achieve a minimum acceptable level of safety, the EC Directive 2004/54/EC suggests, apart from the measures imposed based on tunnel characteristics, the implementation of a risk analysis in cases such as the opening of the road tunnel to DGs. The most widely accepted method for such quantitative risk analysis (QRA) is the OECD/PIARC QRA Model. This research exploits the QRA Model to perform a QRA for five illustrative cases in order to explore the sufficiency of the minimum tunnel safety measures imposed by the Directive when transportation of HGVs and DGs is allowed through the tunnel. The research concludes that, at least for tunnels with marginal values of the EC Directive classes for length and traffic, the risk exposure (F/N curves) lays over the acceptable safety limits of ALARP (as low as reasonably practicable) models. Thus, the manager of the tunnel should take seriously into account the provision of the Directive for further risk analysis and consider more safety measures as well as take into account the risk associated with the alternative routes
Renewable Energy Resources Impact on Clean Electrical Power by developing the North-West England Hydro Resource Model.
This paper describes the development of a sequential decision support system to promote hydroelectric power in North-West England. The system, composed of integrated models, addresses barriers to the installation of hydroelectric power schemes. Information is linked through an economic assessment which identifies different turbine options, assesses their suitability for location and demand; and combines the different types of information in a way that supports decision making. The system is structured into five components: the hydrological resource is modelled using Low Flows 2000, the turbine options are identified from hydrological, environmental and demand requirements; and the consequences of different solutions will be fed into other components so that the environmental impacts and public acceptability can be assessed and valued. A preliminary case study is presented on an old gunpowder works to illustrate how the resource model may be employed. Historical architectural structures, power uptake and educational instruction of hydro power technology are considered
Instability of nonminimally coupled scalar fields in the spacetime of slowly rotating compact objects
Nonminimally coupled free scalar fields may be unstable in the spacetime of
compact objects. Such instability can be triggered by classical seeds or, more
simply, by quantum fluctuations giving rise to the so-called {\em vacuum
awakening effect}. Here, we investigate how the parameter space which
characterizes the instability is affected when the object gains some rotation.
For this purpose, we focus on the stability analysis of nonminimally coupled
scalar fields in the spacetime of slowly spinning matter shells.Comment: 11 pages, 6 figure
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