5,417 research outputs found
Regional similarities in the distributions of well yield from crystalline rocks in Fennoscandia
Well yields from Precambrian and Palaeozoic bedrock in Norway, Sweden and Finland exhibit very
similar and approximately log-normal distributions: all three data sets exhibit a median yield of
600–700 L hr-1, despite the differences in climate and lithology. This similarity is tentatively reflected
on a larger geographical scale by a meta-analysis of the international data sets on crystalline rock aquifers from other recently glaciated areas (i.e., without a thick regolith of weathered rock). An heuristic treatment of the Fennoscandian data sets suggests that this median yield is consistent with the following bulk properties of shallow (to c. 70–80 m depth) crystalline bedrock: transmissivity of
0.56 ± 0.30 m2 d-1 (6.4 ± 3.4 x 10-6 m2 s-1) and hydraulic conductivity of around 1.1 (± 0.6) x 10-7 m s-1
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Magnetic characterization of perpendicular recording media
In this paper, we describe techniques for the magnetic characterization of perpendicular recording media. Such measurements made using traditional techniques, such as the vibrating sample magnetometry (VSM) and alternating gradient force magnetometer (AGFM), have to be corrected for the sample shape demagnetizing factor, which is often found not to be equal to -4p. For measurements other than the simple hysteresis loop, such as remanence curves, this correction must be carried out in real time and we describe the method by which this can be achieved and the process for achieving the correct demagnetization of perpendicular films prior to measurements of the isothermal remanent magnetization curve. A further complication is that real perpendicular media have a soft underlayer beneath the recording layer, which swamps and confuses signals from instruments such as VSM or AGFM. Hence, we describe the construction and use of a magnetooptical Kerr effect magnetometer, which does not penetrate significantly into the soft layer and enables the perpendicular layer to be measured independently. We describe the properties of a traditional alloy perpendicular medium and a Co-Pd multilayer system, which in the latter case exhibits multiple switching behavior. We also address the issue of the effect of the soft underlayer on the coupling in similar longitudinal films and find that the presence of the underlayer induces significant additional coupling effects that may well give rise to an increase in noise in recorded signal
Optimal Timing of Control-Law Updates for Unstable Systems with Continuous Control
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77040/1/AIAA-38570-513.pd
Concepts in Animal Parasitology, Chapter 04: Hosts, Reservoirs, and Vectors
Chapter 4 in Concepts in Animal Parasitology on hosts, reservoirs, and vectors by Matthew G. Bolek, Kyle D. Gustafson, and Gabriel J. Langford. 2024. S. L. Gardner and S. A. Gardner, editors. Zea Books, Lincoln, Nebraska, United States. doi: 10.32873/unl.dc.ciap00
Concepts in Animal Parasitology, Chapter 05: Life Cycles
Chapter 5 in Concepts in Animal Parasitology on life cycles by Matthew G. Bolek, Kyle D. Gustafson, and Gabriel J. Langford. 2024. S. L. Gardner and S. A. Gardner, editors. Zea Books, Lincoln, Nebraska, United States. doi: 10.32873/unl.dc.ciap00
Spectra generated by a confined softcore Coulomb potential
Analytic and approximate solutions for the energy eigenvalues generated by a
confined softcore Coulomb potentials of the form a/(r+\beta) in d>1 dimensions
are constructed. The confinement is effected by linear and harmonic-oscillator
potential terms, and also through `hard confinement' by means of an
impenetrable spherical box. A byproduct of this work is the construction of
polynomial solutions for a number of linear differential equations with
polynomial coefficients, along with the necessary and sufficient conditions for
the existence of such solutions. Very accurate approximate solutions for the
general problem with arbitrary potential parameters are found by use of the
asymptotic iteration method.Comment: 17 pages, 2 figure
Dust Distribution in Gas Disks. A Model for the Ring Around HR 4796A
There have been several model analyses of the near and mid IR flux from the
circumstellar ring around HR4796A. In the vicinity of a young star, the
possibility that the dust ring is embedded within a residual protostellar gas
disk cannot be ruled out. In a gas-rich environment, larger sizes () are needed for the particles to survive the radiative blow out. The total
dust mass required to account for the IR flux is . The
combined influence of gas and stellar radiation may also account for the
observed sharp inner boundary and rapidly fading outer boundary of the ring.
The pressure gradient induced by a small (10%) amplitude variation in the
surface density distribution of a low-mass gaseous disk would be sufficient to
modify the rotation speed of the gas.Comment: proof read version, 26 pages, LaTex, 11 figures. To appear in The
Astronomical Journal June 200
Energies and wave functions for a soft-core Coulomb potential
For the family of model soft Coulomb potentials represented by V(r) =
-\frac{Z}{(r^q+\beta^q)^{\frac{1}{q}}}, with the parameters
Z>0, \beta>0, q \ge 1, it is shown analytically that the potentials and
eigenvalues, E_{\nu\ell}, are monotonic in each parameter. The potential
envelope method is applied to obtain approximate analytic estimates in terms of
the known exact spectra for pure power potentials. For the case q =1, the
Asymptotic Iteration Method is used to find exact analytic results for the
eigenvalues E_{\nu\ell} and corresponding wave functions, expressed in terms of
Z and \beta. A proof is presented establishing the general concavity of the
scaled electron density near the nucleus resulting from the truncated
potentials for all q. Based on an analysis of extensive numerical calculations,
it is conjectured that the crossing between the pair of states
[(\nu,\ell),(\nu',\ell')], is given by the condition \nu'\geq (\nu+1) and \ell'
\geq (\ell+3). The significance of these results for the interaction of an
intense laser field with an atom is pointed out. Differences in the observed
level-crossing effects between the soft potentials and the hydrogen atom
confined inside an impenetrable sphere are discussed.Comment: 13 pages, 5 figures, title change, minor revision
Brownian Thermal Noise in Multilayer Coated Mirrors
We analyze the Brownian thermal noise of a multi-layer dielectric coating,
used in high-precision optical measurements including interferometric
gravitational-wave detectors. We assume the coating material to be isotropic,
and therefore study thermal noises arising from shear and bulk losses of the
coating materials. We show that coating noise arises not only from layer
thickness fluctuations, but also from fluctuations of the interface between the
coating and substrate, driven by internal fluctuating stresses of the coating.
In addition, the non-zero photoeleastic coefficients of the thin films modifies
the influence of the thermal noise on the laser field. The thickness
fluctuations of different layers are statistically independent, however, there
exists a finite coherence between layers and the substrate-coating interface.
Taking into account uncertainties in material parameters, we show that
significant uncertainties still exist in estimating coating Brownian noise.Comment: 26 pages, 18 figure
Kinetic hindrance during the initial oxidation of Pd(100) at ambient pressures
The oxidation of the Pd(100) surface at oxygen pressures in the 10^-6 to 10^3
mbar range and temperatures up to 1000 K has been studied in-situ by surface
x-ray diffraction (SXRD). The results provide direct structural information on
the phases present in the surface region and on the kinetics of the oxide
formation. Depending on the (T,p) environmental conditions we either observe a
thin sqrt(5) x sqrt(5) R27 surface oxide or the growth of a rough, poorly
ordered bulk oxide film of PdO predominantly with (001) orientation. By either
comparison to the surface phase diagram from first-principles atomistic
thermodynamics or by explicit time-resolved measurements we identify a strong
kinetic hindrance to the bulk oxide formation even at temperatures as high as
675 K.Comment: 4 pages including 4 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
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