49,151 research outputs found
Dynamics of freely moving plates connected by a shallow liquid bridge
We study the dynamics of freely moving plates connected by a shallow liquid bridge via analytic and experimental methods. The gap between the plates is used as a small parameter within a lubrication approximation, reducing the problem to an Abel equation of the second kind. Analysis of the governing differential equation yields two novel physical phenomena: (1) An impulse-like peak in the force applied by the liquid bridge on the plates, obtained from a uniform asymptotic solution for small capillary numbers. (2) Both linear and non-linear oscillations of the system for the case of surfaces with low wettability, obtained from small perturbations of the system around the equilibrium point. An experimental setup examining the motion of freely moving plates was constructed, yielding experimental data which compared favorably with the analytic results and specifically displayed the predicted oscillations and impulse-like peak of the applied force. The application of the current analysis to the manipulation of solid bodies and possible future research directions are discussed
Region-based memory management for Mercury programs
Region-based memory management (RBMM) is a form of compile time memory
management, well-known from the functional programming world. In this paper we
describe our work on implementing RBMM for the logic programming language
Mercury. One interesting point about Mercury is that it is designed with strong
type, mode, and determinism systems. These systems not only provide Mercury
programmers with several direct software engineering benefits, such as
self-documenting code and clear program logic, but also give language
implementors a large amount of information that is useful for program analyses.
In this work, we make use of this information to develop program analyses that
determine the distribution of data into regions and transform Mercury programs
by inserting into them the necessary region operations. We prove the
correctness of our program analyses and transformation. To execute the
annotated programs, we have implemented runtime support that tackles the two
main challenges posed by backtracking. First, backtracking can require regions
removed during forward execution to be "resurrected"; and second, any memory
allocated during a computation that has been backtracked over must be recovered
promptly and without waiting for the regions involved to come to the end of
their life. We describe in detail our solution of both these problems. We study
in detail how our RBMM system performs on a selection of benchmark programs,
including some well-known difficult cases for RBMM. Even with these difficult
cases, our RBMM-enabled Mercury system obtains clearly faster runtimes for 15
out of 18 benchmarks compared to the base Mercury system with its Boehm runtime
garbage collector, with an average runtime speedup of 24%, and an average
reduction in memory requirements of 95%. In fact, our system achieves optimal
memory consumption in some programs.Comment: 74 pages, 23 figures, 11 tables. A shorter version of this paper,
without proofs, is to appear in the journal Theory and Practice of Logic
Programming (TPLP
Effect of shell structure on the fission of sub-lead nuclei
Fission of atomic nuclei often produces mass asymmetric fragments. However,
the origin of this asymmetry was believed to be different in actinides and in
the sub-lead region [A. Andreyev {\it et al.}, Phys. Rev. Lett. {\bf 105},
252502 (2010)]. It has recently been argued that quantum shell effects
stabilising pear shapes of the fission fragments could explain the observed
asymmetries in fission of actinides[G. Scamps and C. Simenel, Nature {\bf 564},
382 (2018)]. This interpretation is tested in the sub-lead region using
microscopic mean-field calculations of fission based on the Hartree-Fock
approach with BCS pairing correlations. The evolution of the number of protons
and neutrons in asymmetric fragments of mercury isotope fissions is interpreted
in terms of deformed shell gaps in the fragments. A new method is proposed to
investigate the dominant shell effects in the pre-fragments at scission. We
conclude that the mechanisms responsible for asymmetric fissions in the
sub-lead region are the same as in the actinide region, which is a strong
indication of their universality.Comment: Accepted as a rapid communication by Phys. Rev.
Mercury Wetting and Non-wetting Condensing Research
Mercury wetting and non-wetting condensatio
The Power of General Relativity
We study the cosmological and weak-field properties of theories of gravity
derived by extending general relativity by means of a Lagrangian proportional
to . This scale-free extension reduces to general relativity when
. In order to constrain generalisations of general relativity of
this power class we analyse the behaviour of the perfect-fluid Friedmann
universes and isolate the physically relevant models of zero curvature. A
stable matter-dominated period of evolution requires or . The stable attractors of the evolution are found. By considering the
synthesis of light elements (helium-4, deuterium and lithium-7) we obtain the
bound We evaluate the effect on the power spectrum of
clustering via the shift in the epoch of matter-radiation equality. The horizon
size at matter--radiation equality will be shifted by for a value of
We study the stable extensions of the Schwarzschild
solution in these theories and calculate the timelike and null geodesics. No
significant bounds arise from null geodesic effects but the perihelion
precession observations lead to the strong bound assuming that Mercury follows a timelike geodesic. The combination of
these observational constraints leads to the overall bound on theories of this type.Comment: 26 pages and 5 figures. Published versio
Hinode Calibration for Precise Image Co-alignment between SOT and XRT (November 2006 -- April 2007)
To understand the physical mechanisms for activity and heating in the solar
atmosphere, the magnetic coupling from the photosphere to the corona is an
important piece of information from the Hinode observations, and therefore
precise positional alignment is required among the data acquired by different
telescopes. The Hinode spacecraft and its onboard telescopes were developed to
allow us to investigate magnetic coupling with co-alignment accuracy better
than 1 arcsec. Using the Mercury transit observed on 8 November 2006 and
co-alignment measurements regularly performed on a weekly basis, we have
determined the information necessary for precise image co-alignment and have
confirmed that co-alignment better than 1 arcsec can be realized between Solar
Optical Telescope (SOT) and X-Ray Telescope (XRT) with our baseline
co-alignment method. This paper presents results from the calibration for
precise co-alignment of CCD images from SOT and XRT.Comment: 8 pages, 9 figures, accepted for publication in PASJ (Hinode Special
issue
The contrasting fission potential-energy structure of actinides and mercury isotopes
Fission-fragment mass distributions are asymmetric in fission of typical
actinide nuclei for nucleon number in the range
and proton number in the range . For somewhat
lighter systems it has been observed that fission mass distributions are
usually symmetric. However, a recent experiment showed that fission of
Hg following electron capture on Tl is asymmetric. We calculate
potential-energy surfaces for a typical actinide nucleus and for 12 even
isotopes in the range Hg--Hg, to investigate the similarities
and differences of actinide compared to mercury potential surfaces and to what
extent fission-fragment properties, in particular shell structure, relate to
the structure of the static potential-energy surfaces. Potential-energy
surfaces are calculated in the macroscopic-microscopic approach as functions of
fiveshape coordinates for more than five million shapes. The structure of the
surfaces are investigated by use of an immersion technique. We determine
properties of minima, saddle points, valleys, and ridges between valleys in the
5D shape-coordinate space. Along the mercury isotope chain the barrier heights
and the ridge heights and persistence with elongation vary significantly and
show no obvious connection to possible fragment shell structure, in contrast to
the actinide region, where there is a deep asymmetric valley extending from the
saddle point to scission. The mechanism of asymmetric fission must be very
different in the lighter proton-rich mercury isotopes compared to the actinide
region and is apparently unrelated to fragment shell structure. Isotopes
lighter than Hg have the saddle point blocked from a deep symmetric
valley by a significant ridge. The ridge vanishes for the heavier Hg isotopes,
for which we would expect a qualitatively different asymmetry of the fragments.Comment: 8 pages, 9 figure
Recovery of the Schwarzschild Metric in Theories with Localized Gravity Beyond Linear Order
We solve the Einstein equations in the Randall-Sundrum framework with a
static, spherically symmetric matter distribution on the {\it physical brane}
and obtain an approximate expression for the gravitational field outside the
source to second order in the gravitational coupling. This expression when
confined on the {\it physical brane} coincides with the standard form of the
Schwarzschild metric. Therefore, the Randall-Sundrum scenario is consistent
with the Mercury precession test of General Relativity.Comment: 17 pages, plain Tex, references added, typos correcte
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