15,357 research outputs found
First steps towards the certification of an ARM simulator using Compcert
The simulation of Systems-on-Chip (SoC) is nowadays a hot topic because,
beyond providing many debugging facilities, it allows the development of
dedicated software before the hardware is available. Low-consumption CPUs such
as ARM play a central role in SoC. However, the effectiveness of simulation
depends on the faithfulness of the simulator. To this effect, we propose here
to prove significant parts of such a simulator, SimSoC. Basically, on one hand,
we develop a Coq formal model of the ARM architecture while on the other hand,
we consider a version of the simulator including components written in
Compcert-C. Then we prove that the simulation of ARM operations, according to
Compcert-C formal semantics, conforms to the expected formal model of ARM. Size
issues are partly dealt with using automatic generation of significant parts of
the Coq model and of SimSoC from the official textual definition of ARM.
However, this is still a long-term project. We report here the current stage of
our efforts and discuss in particular the use of Compcert-C in this framework.Comment: First International Conference on Certified Programs and Proofs 7086
(2011
Complete hyperfine Paschen-Back regime at relatively small magnetic fields realized in Potassium nano-cell
A one-dimensional nano-metric-thin cell (NC) filled with potassium metal has
been built and used to study optical atomic transitions in external magnetic
fields. These studies benefit from the remarkable features of the NC allowing
one to use - and -methods for effective investigations of
individual transitions of the K D_1 line. The methods are based on strong
narrowing of the absorption spectrum of the atomic column of thickness L equal
to and to (with \lambda = 770\un{nm} being the resonant
laser radiation wavelength). In particular, for a -polarized radiation
excitation the -method allows us to resolve eight atomic transitions
(in two groups of four atomic transitions) and to reveal two remarkable
transitions that we call Guiding Transitions (GT). The probabilities of all
other transitions inside the group (as well as the frequency slope versus
magnetic field) tend to the probability and to the slope of GT. Note that for
circular polarization there is one group of four transitions and GT do not
exist. Among eight transitions there are also two transitions (forbidden for
= 0) with the probabilities undergoing strong modification under the
influence of magnetic fields. Practically the complete hyperfine Paschen-Back
regime is observed at relatively low (\sim 1\un{kG}) magnetic fields. Note
that for K line GT are absent. Theoretical models describe the experiment
very well.Comment: 6 page
NASA RECON: Course development, administration, and evaluation. A research and development proposal
This proposal addresses the development, administration, and evaluation of a set of transportable, college-level courses to educate science and engineering students in the effective use of automated scientific and technical information storage and retrieval systems, and, in particular, in the use of the NASA RECON system. Chapter 1 presents a brief introduction. Chapter 2 identifies general and specific objectives, i.e., needs analysis, course development, course administration, and course evaluation. Chapter 3 proposes the methodology to be used in successfully accomplishing these objectives. Chapter 4 highlights expected results and product deliverables, and Chapter 5 presents the project evaluation plan to be followed. Chapter 6 is a brief overview of the institutional resources available at the proposing institutions, i.e., at the University of Southwestern Louisiana and at Southern University to support the project. Chapter 7 proposes a budget, time schedule, and management plan. Chapter 8 is a summary of the foregoing
Transportable, university-level educational programs in interactive information storage and retrieval systems
Pursuant to the specifications of a research contract entered into in December, 1983 with NASA, the Computer Science Departments of the University of Southwestern Louisiana and Southern University will be working jointly to address a variety of research and educational issues relating to the use, by non-computer professionals, of some of the largest and most sophiticated interactive information storage and retrieval systems available. Over the projected 6 to 8 year life of the project, in addition to NASA/RECON, the following systems will be examined: Lockheed DIALOG, DOE/RECON, DOD/DTIC, EPA/CSIN, and LLNL/TIS
Spacecraft attitude control for a solar electric geosynchronous transfer mission
A study of the Attitude Control System (ACS) is made for a solar electric propulsion geosynchronous transfer mission. The basic mission considered is spacecraft injection into a low altitude, inclined orbit followed by low thrust orbit changing to achieve geosynchronous orbit. Because of the extended thrusting time, the mission performance is a strong function of the attitude control system. Two attitude control system design options for an example mission evolve from consideration of the spacecraft configuration, the environmental disturbances, and the probable ACS modes of operation. The impact of these design options on other spacecraft subsystems is discussed. The factors which must be considered in determining the ACS actuation and sensing subsystems are discussed. The effects of the actuation and sensing subsystems on the mission performance are also considered
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