8,810 research outputs found
Final Project Report: Laboratory Investigation Armor Layer for Protective Cap Manistique River and Harbor, Michigan
https://deepblue.lib.umich.edu/bitstream/2027.42/154188/1/39015101405093.pd
Experimental and analytical comparison of flowfields in a 110 N (25 lbf) H2/O2 rocket
A gaseous hydrogen/gaseous oxygen 110 N (25 lbf) rocket was examined through the RPLUS code using the full Navier-Stokes equations with finite rate chemistry. Performance tests were conducted on the rocket in an altitude test facility. Preliminary parametric analyses were performed for a range of mixture ratios and fuel film cooling pcts. It is shown that the computed values of specific impulse and characteristic exhaust velocity follow the trend of the experimental data. Specific impulse computed by the code is lower than the comparable test values by about two to three percent. The computed characteristic exhaust velocity values are lower than the comparable test values by three to four pct. Thrust coefficients computed by the code are found to be within two pct. of the measured values. It is concluded that the discrepancy between computed and experimental performance values could not be attributed to experimental uncertainty
Toward An Axiomatic Approach to Information Systems Development
This paper advocates an approach called the axiomatic method to reduce the costs of constructing an information system. Further, we contrast the applicability of the axiomatic method to the more traditional approach of enumerating alternatives (the algorithmic method) in constructing an information system. We delineate the steps involved in building an information system, present a set of pilot axioms, and offer some derivative theorems. We then apply these axioms and theorems to each phase (specification, design, implementation, and maintenance) of the information system life cycle, and confirm a number of empirical results other information system builders have observed
Dark Energy and Right-Handed Neutrinos
We explore the possibility that a CP violating phase of the neutrino mass
matrix is promoted to a pseudo-Goldstone-boson field and is identified as the
quintessence field for Dark Energy. By requiring that the quintessence
potential be calculable from a Lagrangian, and that the extreme flatness of the
potential be stable under radiative corrections, we are led to an essentially
unique model. Lepton number is violated only by Majorana masses of light,
right-handed neutrinos, comparable to the Dirac masses that mix right- with
left-handed neutrinos. We outline the rich and constrained neutrino
phenomenology that results from this proposal.Comment: 10 pages, 2 figure
`Mass without mass' from thin shells in Gauss-Bonnet gravity
Five tensor equations are obtained for a thin shell in Gauss-Bonnet gravity.
There is the well known junction condition for the singular part of the stress
tensor intrinsic to the shell, which we also prove to be well defined. There
are also equations relating the geometry of the shell (jump and average of the
extrinsic curvature as well as the intrinsic curvature) to the non-singular
components of the bulk stress tensor on the sides of the thin shell.
The equations are applied to spherically symmetric thin shells in vacuum. The
shells are part of the vacuum, they carry no energy tensor. We classify these
solutions of `thin shells of nothingness' in the pure Gauss-Bonnet theory.
There are three types of solutions, with one, zero or two asymptotic regions
respectively. The third kind of solution are wormholes. Although vacuum
solutions, they have the appearance of mass in the asymptotic regions. It is
striking that in this theory, exotic matter is not needed in order for
wormholes to exist- they can exist even with no matter.Comment: 13 pages, RevTex, 8 figures. Version 2: includes discussion on the
well-defined thin shell limit. Version 3: typos fixed, a reference added,
accepted for publication in Phys. Rev.
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