15,964 research outputs found
FEATS - Finite element thermal stress analysis of plane or axisymmetric solids
FEATS computer code uses finite element analysis to calculate steady state temperature and thermal stress fields for either axisymmetric or plane two-dimensional bodies with boundary conditions, including specified displacements, loads, and thermal boundary conditions
General series solution technique for bending of irregular laterally loaded flat plates
Computer program calculates the stresses and lateral deflections to a uniform thickness flat plate with a uniform pressure load. The plate to be analyzed may have several different boundary conditions. The program is written in FORTRAN 4 for use on the CDC 6600 computer
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Estimating the stochastic uncertainty in sample-based estimates of infant mortality in Ghana
The Infant Mortality Rate (IMR) is an important population health statistic often used as one of the indicators of the health status of a nation. In many countries lacking adequate vital registration systems, sample methods are used to estimate IMRs. However, evaluations of this approach are rare and the literature contains no assessments of the stochastic uncertainty underlying these estimated IMRs. Stochastic uncertainty reflects the fact that even where the underlying IMR is constant in a small population over time, there is a likelihood of yearly fluctuation in its empirical observations even if it is measured from a complete count of the events of interest. In this study a method is presented that can be used to assess this stochastic uncertainty. We use the country of Ghana as a case study for this purpose. The method, a beta-binomial model, is described, tested for validity, and illustrated using 2014 sample-based estimates of IMR for 13 sample regions in Ghana. As such, the approach we described regarding the revision of sample-based IMR estimates is aimed at taking into account of the stochastic uncertainty while preserving the information concerning the uncertainty due to sampling. In applying the method to Ghana, we find that the sample-based IMR estimates perform well in accounting for stochastic uncertainty and could be applied elsewhere
Factors affecting the retirement of commercial transport jet aircraft
A brief historical background of the technology and economics of aircraft replacement and retirement in the prejet era is presented to see whether useful insights can be obtained applicable to the jet area. Significant differences between the two periods were demonstated. Current technological and operational economic perspectives were investigated in detail. Some conclusions are drawn to aircraft retirement policies
An effective multigrid method for high-speed flows
The use is considered of a multigrid method with central differencing to solve the Navier-Stokes equations for high speed flows. The time dependent form of the equations is integrated with a Runge-Kutta scheme accelerated by local time stepping and variable coefficient implicit residual smoothing. Of particular importance are the details of the numerical dissipation formulation, especially the switch between the second and fourth difference terms. Solutions are given for 2-D laminar flow over a circular cylinder and a 15 deg compression ramp
Coupling hydrophobic, dispersion, and electrostatic contributions in continuum solvent models
Recent studies of the hydration of micro- and nanoscale solutes have
demonstrated a strong {\it coupling} between hydrophobic, dispersion and
electrostatic contributions, a fact not accounted for in current implicit
solvent models. We present a theoretical formalism which accounts for coupling
by minimizing the Gibbs free energy with respect to a solvent volume exclusion
function. The solvent accessible surface is output of our theory. Our method is
illustrated with the hydration of alkane-assembled solutes on different length
scales, and captures the strong sensitivity to the particular form of the
solute-solvent interactions in agreement with recent computer simulations.Comment: 11 pages, 2 figure
Friction factors for smooth pipe flow
Friction factor data from two recent pipe flow experiments are combined to provide a comprehensive picture of the friction factor variation for Reynolds numbers from 10 to 36,000,000
Interaction between Faraday rotation and Cotton-Mouton effects in polarimetry modeling for NSTX
The evolution of electromagnetic wave polarization is modeled for propagation
in the major radial direction in the National Spherical Torus Experiment (NSTX)
with retroreflection from the center stack of the vacuum vessel. This modeling
illustrates that the Cotton-Mouton effect-elliptization due to the magnetic
field perpendicular to the propagation direction-is shown to be strongly
weighted to the high-field region of the plasma. An interaction between the
Faraday rotation and Cotton-Mouton effects is also clearly identified.
Elliptization occurs when the wave polarization direction is neither parallel
nor perpendicular to the local transverse magnetic field. Since Faraday
rotation modifies the polarization direction during propagation, it must also
affect the resultant elliptization. The Cotton-Mouton effect also intrinsically
results in rotation of the polarization direction, but this effect is less
significant in the plasma conditions modeled. The interaction increases at
longer wavelength, and complicates interpretation of polarimetry measurements.Comment: Contributed paper published as part of the Proceedings of the 18th
Topical Conference on High-Temperature Plasma Diagnostics, Wildwood, New
Jersey, May, 201
Multigrid for hypersonic viscous two- and three-dimensional flows
The use of a multigrid method with central differencing to solve the Navier-Stokes equations for hypersonic flows is considered. The time dependent form of the equations is integrated with an explicit Runge-Kutta scheme accelerated by local time stepping and implicit residual smoothing. Variable coefficients are developed for the implicit process that removes the diffusion limit on the time step, producing significant improvement in convergence. A numerical dissipation formulation that provides good shock capturing capability for hypersonic flows is presented. This formulation is shown to be a crucial aspect of the multigrid method. Solutions are given for two-dimensional viscous flow over a NACA 0012 airfoil and three-dimensional flow over a blunt biconic
Coupling nonpolar and polar solvation free energies in implicit solvent models
Recent studies on the solvation of atomistic and nanoscale solutes indicate
that a strong coupling exists between the hydrophobic, dispersion, and
electrostatic contributions to the solvation free energy, a facet not
considered in current implicit solvent models. We suggest a theoretical
formalism which accounts for coupling by minimizing the Gibbs free energy of
the solvent with respect to a solvent volume exclusion function. The resulting
differential equation is similar to the Laplace-Young equation for the
geometrical description of capillary interfaces, but is extended to microscopic
scales by explicitly considering curvature corrections as well as dispersion
and electrostatic contributions. Unlike existing implicit solvent approaches,
the solvent accessible surface is an output of our model. The presented
formalism is illustrated on spherically or cylindrically symmetrical systems of
neutral or charged solutes on different length scales. The results are in
agreement with computer simulations and, most importantly, demonstrate that our
method captures the strong sensitivity of solvent expulsion and dewetting to
the particular form of the solvent-solute interactions.Comment: accpted in J. Chem. Phy
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