33,456 research outputs found
Molecular Beams
Contains research objectives, summary of research and reports on three research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)Sloan Fund for Basic Research (M. I. T. Grant 249
Biochemical and metabolic effects of a six- month exposure of small animals to a helium- oxygen atmosphere
Biochemical and metabolic effects of exposure of mice to helium-oxygen atmospher
Late Miocene to early Pliocene stratigraphic record in northern Taranaki Basin: Condensed sedimentation ahead of Northern Graben extension and progradation of the modern continental margin
The middle Pliocene-Pleistocene progradation of the Giant Foresets Formation in Taranaki Basin built up the modern continental margin offshore from western North Island. The late Miocene to early Pliocene interval preceding this progradation was characterised in northern Taranaki Basin by the accumulation of hemipelagic mudstone (Manganui Formation), volcaniclastic sediments (Mohakatino Formation), and marl (Ariki Formation), all at bathyal depths. The Manganui Formation has generally featureless wireline log signatures and moderate to low amplitude seismic reflection characteristics. Mohakatino Formation is characterised by a sharp decrease in the GR log value at its base, a blocky GR log motif reflecting sandstone packets, and erratic resistivity logs. Seismic profiles show bold laterally continuous reflectors. The Ariki Formation has a distinctive barrel-shaped to blocky GR log motif. This signature is mirrored by the SP log and often by an increase in resistivity values through this interval. The Ariki Formation comprises (calcareous) marl made up of abundant planktic foraminifera, is 109 m thick in Ariki-1, and accumulated over parts of the Western Stable Platform and beneath the fill of the Northern Graben. It indicates condensed sedimentation reflecting the distance of the northern region from the contemporary continental margin to the south
Systematic treatment of displacements, strains and electric fields in density-functional perturbation theory
The methods of density-functional perturbation theory may be used to
calculate various physical response properties of insulating crystals including
elastic, dielectric, Born charge, and piezoelectric tensors. These and other
important tensors may be defined as second derivatives of the total energy with
respect to atomic-displacement, electric-field, or strain perturbations, or as
mixed derivatives with respect to two of these perturbations. The resulting
tensor quantities tend to be coupled in complex ways in polar crystals, giving
rise to a variety of variant definitions. For example, it is generally
necessary to distinguish between elastic tensors defined under different
electrostatic boundary conditions, and between dielectric tensors defined under
different elastic boundary conditions. Here, we describe an approach for
computing all of these various response tensors in a unified and systematic
fashion. Applications are presented for two materials, wurtzite ZnO and
rhombohedral BaTiO3, at zero temperature.Comment: 14 pages. Uses REVTEX macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/xfw_sys/index.htm
First Passage Time in a Two-Layer System
As a first step in the first passage problem for passive tracer in stratified
porous media, we consider the case of a two-dimensional system consisting of
two layers with different convection velocities. Using a lattice generating
function formalism and a variety of analytic and numerical techniques, we
calculate the asymptotic behavior of the first passage time probability
distribution. We show analytically that the asymptotic distribution is a simple
exponential in time for any choice of the velocities. The decay constant is
given in terms of the largest eigenvalue of an operator related to a half-space
Green's function. For the anti-symmetric case of opposite velocities in the
layers, we show that the decay constant for system length crosses over from
behavior in diffusive limit to behavior in the convective
regime, where the crossover length is given in terms of the velocities.
We also have formulated a general self-consistency relation, from which we have
developed a recursive approach which is useful for studying the short time
behavior.Comment: LaTeX, 28 pages, 7 figures not include
Quasi-Newtonian dust cosmologies
Exact dynamical equations for a generic dust matter source field in a
cosmological context are formulated with respect to a non-comoving
Newtonian-like timelike reference congruence and investigated for internal
consistency. On the basis of a lapse function (the relativistic
acceleration scalar potential) which evolves along the reference congruence
according to (), we find that
consistency of the quasi-Newtonian dynamical equations is not attained at the
first derivative level. We then proceed to show that a self-consistent set can
be obtained by linearising the dynamical equations about a (non-comoving) FLRW
background. In this case, on properly accounting for the first-order momentum
density relating to the non-relativistic peculiar motion of the matter,
additional source terms arise in the evolution and constraint equations
describing small-amplitude energy density fluctuations that do not appear in
similar gravitational instability scenarios in the standard literature.Comment: 25 pages, LaTeX 2.09 (10pt), to appear in Classical and Quantum
Gravity, Vol. 15 (1998
Using a fuzzy inference system to control a pumped storage hydro plant
The paper discusses the development of a fuzzy inference system (FIS) based governor control for a pumped storage hydroelectric plant. The First Hydro Company's plant at Dinorwig in North Wales is the largest of its kind in Europe and is mainly used for frequency control of the UK electrical grid. In previous investigations, a detailed model of the plant was developed using MATLAB(R)/SIMULINK(R) and this is now being used to compare FIS governor operation with the proportional-integral-derivative (PID) controller currently used. The paper describes the development of an FIS governor, and shows that its response to a step increase in load is superior to the PID under certain conditions of load. The paper proceeds to discuss the implications of these results in view of the possible practical application of an FIS governor at the Dinorwig plant
The State-of-the-Art HST Astro-Photometric Analysis of the core of \omega Centauri. III. The Main Sequence's Multiple Populations Galore
We take advantage of the exquisite quality of the Hubble Space Telescope
26-filter astro-photometric catalog of the core of Omega Cen presented in the
first paper of this series and the empirical differential-reddening correction
presented in the second paper in order to distill the main sequence into its
constituent populations. To this end, we restrict ourselves to the five most
useful filters: the magic "trio" of F275W, F336W, and F438W, along with F606W
and F814W. We develop a strategy for identifying color systems where different
populations stand out most distinctly, then we isolate those populations and
examine them in other filters where their sub-populations also come to light.
In this way, we have identified at least 15 sub-populations, each of which has
a distinctive fiducial curve through our 5-dimensional photometric space. We
confirm the MSa to be split into two subcomponents, and find that both the bMS
and the rMS are split into three subcomponents. Moreover, we have discovered
two additional MS groups: the MSd (which has three subcomponents) shares
similar properties with the bMS, and the MSe (which has four subcomponents),
has properties more similar to those of the rMS. We examine the fiducial curves
together and use synthetic spectra to infer relative heavy-element,
light-element, and Helium abundances for the populations. Our findings show
that the stellar populations and star formation history of Omega Cen are even
more complex than inferred previously. Finally, we provide as a supplement to
the original catalog a list that identifies for each star which population it
most likely is associated with.Comment: 22 pages, 17 figures (most in lower res), 2 tables, accepted for
publication in Ap
Atomic Beams
Contains research objectives and reports on two research projects.Lincoln Laboratory, Purchase Order DDL-B222Department of the ArmyDeparment of the NavyDepartment of the Air Force under Contract AF19(122)-45
Molecular Beams
Contains reports on three research projects.Lincoln Laboratory (Purchase Order DDL B-00283)United States ArmyUnited States NavyUnited States Air Force (Contract AF19(604)-5200
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