The Microscopic Dynamics of Liquid and Solid Parahydrogen

We have measured the almost-pure incoherent scattering function of liquid and solid parahydrogen, using inelastic neutron scattering. The experiment was carried out on TOSCA, a time-of-flight, inverse-geometry, crystal-analyser spectrometer, operating on the pulsed neutron source ISIS (UK). The measured double differential cross section gives a direct experimental access to the microscopic dynamics of condensed hydrogen. From the high energy region of the spectrum, where the Impulse Approximation for the center of mass motion applies, we have been able to extract the translational mean kinetic energy, which turns out to be density dependent. The density behaviors of the liquid and solid mean kinetic energy are slightly different. In the low energy region we used the Gaussian approximation to compare, in the liquid phase, the results of a novel quantum simulation calculation with the experimental data. Results are encouraging, but suggest further work, possibly beyond the Gaussian approximation.     

PROQOS—Dynamic SLA Management in DiffServ Space Links

Several base elements for the provision of quality of service guarantees have been developed in the recent past. Of these, the Differentiated Services (DiffServ) architecture stands out as the most promising. In spite of this, various issues remain, especially when multidomain DiffServ services are concerned. In this case, some forms of distributed management of Service Level Agreements that allow the specification, exchange, enforcement and monitoring of quality of service data must be in place. Although, again, some isolated solutions exist for each of these problems, considerable effort is necessary to make them work together. The project presented in this paper tried to assess the feasibility of providing differentiated quality of service in satellite IP networks, by developing a dynamic Service Level Agreement management solution for an IP over Digital Video Broadcast Satellite system. The functionality of the implemented system comprises system configuration, dynamic SLA negotiation, QoS monitoring and metering, SLA conformance checking, and QoS reporting to customers.