2,603,455 research outputs found
Development of a Smart Waste Management System for City Application
A thesis presented to the faculty of the Elmer R. Smith College of Business and Technology Morehead State University in partial fulfillment of the requirements for the Degree Master of Science by Lawrence D. Fraction on April 14, 2023
Robust, Radiation Tolerant Command and Data Handling and Power System Electronics for SmallSats
In today's budgetary environment, there is significant interest within the National Aeronautics and Space Administration (NASA) to enable small robotic science missions that can be executed faster and cheaper than previous larger missions. To help achieve this, focus has shifted from using exclusively radiation-tolerant or radiation-hardened parts to using more commercial-off-the-shelf (COTS) components for NASA small satellite missions that can last at least one year in orbit. However, there are some portions of a spacecraft's avionics, such as the Command and Data Handling (C&DH) subsystem and the Power System Electronics (PSE) that need to have a higher level of reliability that goes beyond what is attainable with currently available COTS parts. While there are a number of COTS components that can withstand a total ionizing dose (TID) of tens or hundreds of kilorads, there is still a great deal of concern about tolerance to and mitigation of single-event effects (SEE)
Goddard Modular SmallSat Architecture (GMSA) Hardware Presentation
In today's rapidly advancing technology roadmap for space applications there is an emphasis on completing missions faster and cheaper than previous large-scale missions at the National Aeronautics and Space Administration (NASA) such as the Magnetospheric Multiscale (MMS) mission. As part of this effort, focus has shifted from using mostly radiation-tolerant or radiation-hardened parts to more commercial-off-the-shelf (COTS) components for missions that can last at least one year in orbit. However, there are some portions of a spacecraft's avionics, such as the command and data handling (C&DH) system and the Electrical Power Systems (EPS) that need to have some level of predictable reliability that goes beyond the capabilities of currently available COTS parts. While there are a number of COTS components that can withstand a total ionizing dose (TID) of tens or hundreds of kilorads, there is still a great deal of concern about tolerance to and mitigation of single-event effects (SEE)
Positron Fraction in the CMSSM
A fit to the present data on the cosmic ray positron fraction can be
considerably improved,if in addition to the positron production by nuclear
interactions in the universe the possible contribution from supersymmetric dark
matter annihilation is taken into account. We scan over the complete SUSY
parameter space of the Constrained Minimal Supersymmetric Model (CMSSM) and
find that in the acceptable regions the neutralino annihilation into b-bbar
quark pairs is the dominant channel with hard positrons emerging from the
semileptonic decays of the B-mesons.Comment: 6 pages, Latex, Proceedings of the 4th International Workshop on
Identification of Dark Matter (idm2002), York, England, 2-6 September, 200
A Farey Fraction Spin Chain
We introduce a new number-theoretic spin chain and explore its thermodynamics
and connections with number theory. The energy of each spin configuration is
defined in a translation-invariant manner in terms of the Farey fractions, and
is also expressed using Pauli matrices. We prove that the free energy exists
and exhibits a unique phase transition at inverse temperature beta = 2. The
free energy is the same as that of a related, non translation-invariant
number-theoretic spin chain. Using a number-theoretic argument, the
low-temperature (beta > 3) state is shown to be completely magnetized for long
chains. The number of states of energy E = log(n) summed over chain length is
expressed in terms of a restricted divisor problem. We conjecture that its
asymptotic form is (n log n), consistent with the phase transition at beta = 2,
and suggesting a possible connection with the Riemann zeta function. The spin
interaction coefficients include all even many-body terms and are translation
invariant. Computer results indicate that all the interaction coefficients,
except the constant term, are ferromagnetic.Comment: 15 pages + 5 figures, postscript. Contact: [email protected]
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