1,747 research outputs found
Autonomous integrated GPS/INS navigation experiment for OMV. Phase 1: Feasibility study
The phase 1 research focused on the experiment definition. A tightly integrated Global Positioning System/Inertial Navigation System (GPS/INS) navigation filter design was analyzed and was shown, via detailed computer simulation, to provide precise position, velocity, and attitude (alignment) data to support navigation and attitude control requirements of future NASA missions. The application of the integrated filter was also shown to provide the opportunity to calibrate inertial instrument errors which is particularly useful in reducing INS error growth during times of GPS outages. While the Orbital Maneuvering Vehicle (OMV) provides a good target platform for demonstration and for possible flight implementation to provide improved capability, a successful proof-of-concept ground demonstration can be obtained using any simulated mission scenario data, such as Space Transfer Vehicle, Shuttle-C, Space Station
Status of reaction theory for studying rare isotopes
Reactions are an important tool to study nuclear structure and for extracting
reactions relevant for astrophysics. In this paper we focus on deuteron induced
reactions which can provide information on neutron shell evolution as well as
neutron capture cross sections. We review recent work on the systematic
comparison of the continuum discretized coupled channel method, the adiabatic
wave approximation and the Faddeev momentum-space approach. We also explore
other aspects of the reaction mechanism and discuss in detail difficulties
encountered in the calculations.Comment: 7 pages, 5 figures, proceeding for HITES 201
A study of the reaction
A study of the reaction in the energy range where the
recent data from Uppsala are available, is done in the two-step model of
production including the final state interaction. The final state
interaction is incorporated through the solution of the Lippmann Schwinger
equation using an elastic scattering matrix element, ,
which is required to be half off-shell. It is written in a factorized form,
with an off-shell form factor multiplying an on-shell part given by an
effective range expansion up to the fourth power in momentum. The parameters of
this expansion have been taken from an existing recent relativistic Faddeev
equation solution for the system corresponding to different
scattering amplitudes. Calculations have also been done using few body
equations within a finite rank approximation (FRA) to generate . The final state interaction is included in the spirit of the
Watson-Migdal prescription by multiplying the matrix element by the inverse of
the Jost function. The interaction is found to be dominant in the
region of small invariant mass, . The interaction
enhances the cross section in the whole region of , but is larger
for large . We find nearly isotropic angular distributions of the
proton and the deuteron in the final state. All the above observations are in
agreement with data. The production mechanism for the entire range of the
existing data on the reaction seems to be dominated by the
two-step model of production.Comment: 22 pages, 12 figures, accepted for publication in Phys. Rev.
A systematic review of current knowledge of HIV epidemiology and of sexual behaviour in Nepal
OBJECTIVE: To systematically review information on HIV epidemiology and on sexual behaviour in Nepal with a view to identifying gaps in current knowledge.
METHODS: Systematic review covering electronic databases, web-based information, personal contact with experts and hand searching of key journals.
RESULTS: HIV-1 seroprevalence has been rising rapidly in association with high-risk behaviours, with current levels of 40% amongst the nation's injecting drug users and approaching 20% amongst Kathmandu's female commercial sex workers (FCSWs). HIV seroprevalence remains low in the general population (0.29% of 15–49 year olds). There are significant methodological limitations in many of the seroprevalence studies identified, and these estimates need to be treated with caution. There are extensive migration patterns both within the country and internationally which provide the potential for considerable sexual networking. However, studies of sexual behaviour have focused on FCSWs and the extent of sexual networks within the general population is largely unknown.
CONCLUSIONS: Whilst some of the ingredients are present for an explosive HIV epidemic in Nepal, crucial knowledge on sexual behaviour in the general population is missing. Research on sexual networking is urgently required to guide HIV control in Nepal. There is also a need for further good-quality epidemiological studies of HIV seroprevalence
- …