2,749 research outputs found
Effect of flow on the acoustic reflection coefficient at a duct inlet
The effect of duct Mach number upon the acoustic reflection coefficient at the inlet of a duct with mean
flow is investigated. An analysis, which models the duct inlet as a very short, one-dimensional nozzle over
which the mean flow is accelerated from rest, gives good agreement with some recent experimental results.
Discrepancies between the analysis and the experimental results are discussed in terms of radiation losses at
the inlet and real fluid-flow effects within the duct
Tunable asymmetric magnetoimpedance effect in ferromagnetic NiFe/Cu/Co films
We investigate the magnetization dynamics through the magnetoimpedance effect
in ferromagnetic NiFe/Cu/Co films. We observe that the magnetoimpedance
response is dependent on the thickness of the non-magnetic Cu spacer material,
a fact associated to the kind of the magnetic interaction between the
ferromagnetic layers. Thus, we present an experimental study on asymmetric
magnetoimpedance in ferromagnetic films with biphase magnetic behavior and
explore the possibility of tuning the linear region of the magnetoimpedance
curves around zero magnetic field by varying the thickness of the non-magnetic
spacer material, and probe current frequency. We discuss the experimental
magnetoimpedance results in terms of the different mechanisms governing the
magnetization dynamics at distinct frequency ranges, quasi-static magnetic
properties, thickness of the non-magnetic spacer material, and the kind of the
magnetic interaction between the ferromagnetic layers. The results place
ferromagnetic films with biphase magnetic behavior exhibiting asymmetric
magnetoimpedance effect as a very attractive candidate for application as probe
element in the development of auto-biased linear magnetic field sensors.Comment: 5 figure
Chaotic Orbits in Thermal-Equilibrium Beams: Existence and Dynamical Implications
Phase mixing of chaotic orbits exponentially distributes these orbits through
their accessible phase space. This phenomenon, commonly called ``chaotic
mixing'', stands in marked contrast to phase mixing of regular orbits which
proceeds as a power law in time. It is operationally irreversible; hence, its
associated e-folding time scale sets a condition on any process envisioned for
emittance compensation. A key question is whether beams can support chaotic
orbits, and if so, under what conditions? We numerically investigate the
parameter space of three-dimensional thermal-equilibrium beams with space
charge, confined by linear external focusing forces, to determine whether the
associated potentials support chaotic orbits. We find that a large subset of
the parameter space does support chaos and, in turn, chaotic mixing. Details
and implications are enumerated.Comment: 39 pages, including 14 figure
The role of elastic stresses on leaf venation morphogenesis
We explore the possible role of elastic mismatch between epidermis and
mesophyll as a driving force for the development of leaf venation. The current
prevalent 'canalization' hypothesis for the formation of veins claims that the
transport of the hormone auxin out of the leaves triggers cell differentiation
to form veins. Although there is evidence that auxin plays a fundamental role
in vein formation, the simple canalization mechanism may not be enough to
explain some features observed in the vascular system of leaves, in particular,
the abundance of vein loops. We present a model based on the existence of
mechanical instabilities that leads very naturally to hierarchical patterns
with a large number of closed loops. When applied to the structure of high
order veins, the numerical results show the same qualitative features as actual
venation patterns and, furthermore, have the same statistical properties. We
argue that the agreement between actual and simulated patterns provides strong
evidence for the role of mechanical effects on venation development.Comment: 10 figures, published in PLoS Computational Biolog
Fermionization of two distinguishable fermions
In this work we study a system of two distinguishable fermions in a 1D
harmonic potential. This system has the exceptional property that there is an
analytic solution for arbitrary values of the interparticle interaction. We
tune the interaction strength via a magnetic offset field and compare the
measured properties of the system to the theoretical prediction. At the point
where the interaction strength diverges, the energy and square of the wave
function for two distinguishable particles are the same as for a system of two
identical fermions. This is referred to as fermionization. We have observed
this phenomenon by directly comparing two distinguishable fermions with
diverging interaction strength with two identical fermions in the same
potential. We observe good agreement between experiment and theory. By adding
one or more particles our system can be used as a quantum simulator for more
complex few-body systems where no theoretical solution is available
Distribution and morphometry of shallow lakes in a temperate zone (Buenos Aires Province, Argentina)
We have developed a database of water bodies to characterise and assess the distribution and morphometry of Pampean shallow lakes and reservoirs in a temperate zone (Buenos Aires Province, Argentina). In the study area, there are over 2000 shallow lakes with a mean area 2. In the last two cases, geomorphology determines the morphometry and location of these shallow lakes. The development of numerous water bodies with areas 2). En los Ăşltimos dos casos, la morfometrĂa y la localizaciĂłn de los lagos fue influenciada por la geomorfologĂa. El desarrollo de numerosos cuerpos de agua cuya área media es menor a 1 km2 causĂł un incremento en el nĂşmero de cuerpos de agua durante el año hĂşmedo. El área cubierta por agua y la densidad de los lagos fue más baja en la zona de mesetas (situada al oeste del área de estudio), baja en la zona serrana, moderada en el centro del área de estudio y alta en las planicies del sector este del área de estudio
Wave Mechanics of a Two Wire Atomic Beamsplitter
We consider the problem of an atomic beam propagating quantum mechanically
through an atom beam splitter. Casting the problem in an adiabatic
representation (in the spirit of the Born-Oppenheimer approximation in
molecular physics) sheds light on explicit effects due to non-adiabatic passage
of the atoms through the splitter region. We are thus able to probe the fully
three dimensional structure of the beam splitter, gathering quantitative
information about mode-mixing, splitting ratios,and reflection and transmission
probabilities
Correlation of bio- and magnetostratigraphy of Badenian sequences from western and northern Hungary
Lithological, magnetostratigraphic and paleontological (nannoplankton, foraminifers, molluscs) studies were carried out on the Badenian successions of boreholes Sopron-89, Nagylozs-1 and Sata-75 in Hungary. The correlations with the ATNTS2004 scale show that the Badenian sedimentation began during Chron C5Br thus the earliest Badenian deposits are missing in the sections. The first occurrence of Orbulina suturalis Bronnimann has been observed in Subchron C5Bn.1r, at 14.9 Ma. Although it is older than the interpolated age of 14.74 Ma in Chron C5ADr in the ATNTS2004, it is consistent with the age of 15.1 Ma obtained from recent calibration of planktonic foraminiferal bioevents. The base of the Bulimina-Bolivina Zone has been determined at 13.7 Ma in Chron C5ABr, and the Badenian/Sarmatian boundary is recorded within Chron C5AAn, at 13.15 Ma
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