22,560 research outputs found
Science Bots: a Model for the Future of Scientific Computation?
As a response to the trends of the increasing importance of computational
approaches and the accelerating pace in science, I propose in this position
paper to establish the concept of "science bots" that autonomously perform
programmed tasks on input data they encounter and immediately publish the
results. We can let such bots participate in a reputation system together with
human users, meaning that bots and humans get positive or negative feedback by
other participants. Positive reputation given to these bots would also shine on
their owners, motivating them to contribute to this system, while negative
reputation will allow us to filter out low-quality data, which is inevitable in
an open and decentralized system.Comment: WWW 2015 Companion, May 18-22, 2015, Florence, Ital
Impact of 4D channel distribution on the achievable rates in coherent optical communication experiments
We experimentally investigate mutual information and generalized mutual
information for coherent optical transmission systems. The impact of the
assumed channel distribution on the achievable rate is investigated for
distributions in up to four dimensions. Single channel and wavelength division
multiplexing (WDM) transmission over transmission links with and without inline
dispersion compensation are studied. We show that for conventional WDM systems
without inline dispersion compensation, a circularly symmetric complex Gaussian
distribution is a good approximation of the channel. For other channels, such
as with inline dispersion compensation, this is no longer true and gains in the
achievable information rate are obtained by considering more sophisticated
four-dimensional (4D) distributions. We also show that for nonlinear channels,
gains in the achievable information rate can also be achieved by estimating the
mean values of the received constellation in four dimensions. The highest gain
for such channels is seen for a 4D correlated Gaussian distribution
Old Times, Better Times? German Miners’ Knappschaften, Pay-as-you-go Pensions, and Implicit Rates of Return, 1854–1913
This paper contributes to the literature on the weakness of modern pay-as-you-go social security systems in financing pensions by taking a business and economic historical perspective on the issue. It focuses on Prussian Knappschaften (plural of Knappschaft), which provided miners with compulsory invalidity and implicit old-age insurance, and studies the period from 1854 to 1913. Knappschaften used the pay-as-you-go mechanism, and, in the long-term, came under financial pressure by the rising number of pensioners. The question to be answered is whether Knappschaften were able to off er cohorts of miners entering the system at diff erent times the same implicit rates of return. Did Knappschaften provide an intergenerationally sustainable policy, or did adjustments of contributions and other parameters decrease the dividend for insured miners over time?Insurance; implicit rates of return; Knappschaft; mining; pay-as-you-go; pensions; Prussia; welfare state
A monolithic fluid-structure interaction formulation for solid and liquid membranes including free-surface contact
A unified fluid-structure interaction (FSI) formulation is presented for
solid, liquid and mixed membranes. Nonlinear finite elements (FE) and the
generalized-alpha scheme are used for the spatial and temporal discretization.
The membrane discretization is based on curvilinear surface elements that can
describe large deformations and rotations, and also provide a straightforward
description for contact. The fluid is described by the incompressible
Navier-Stokes equations, and its discretization is based on stabilized
Petrov-Galerkin FE. The coupling between fluid and structure uses a conforming
sharp interface discretization, and the resulting non-linear FE equations are
solved monolithically within the Newton-Raphson scheme. An arbitrary
Lagrangian-Eulerian formulation is used for the fluid in order to account for
the mesh motion around the structure. The formulation is very general and
admits diverse applications that include contact at free surfaces. This is
demonstrated by two analytical and three numerical examples exhibiting strong
coupling between fluid and structure. The examples include balloon inflation,
droplet rolling and flapping flags. They span a Reynolds-number range from
0.001 to 2000. One of the examples considers the extension to rotation-free
shells using isogeometric FE.Comment: 38 pages, 17 figure
Universality and non-universality of mobility in heterogeneous single-file systems and Rouse chains
We study analytically the tracer particle mobility in single-file systems
with distributed friction constants. Our system serves as a prototype for
non-equilibrium, heterogeneous, strongly interacting Brownian systems. The long
time dynamics for such a single-file setup belongs to the same universality
class as the Rouse model with dissimilar beads. The friction constants are
drawn from a density and we derive an asymptotically exact
solution for the mobility distribution , where is the
Laplace-space mobility. If is light-tailed (first moment exists) we
find a self-averaging behaviour: with
. When is heavy-tailed,
for large we obtain
moments where
and no self-averaging. The results are corroborated by
simulations.Comment: 8 pages, 4 figures, REVTeX, to appear in Physical Review
Transition probabilities and measurement statistics of postselected ensembles
It is well-known that a quantum measurement can enhance the transition
probability between two quantum states. Such a measurement operates after
preparation of the initial state and before postselecting for the final state.
Here we analyze this kind of scenario in detail and determine which probability
distributions on a finite number of outcomes can occur for an intermediate
measurement with postselection, for given values of the following two
quantities: (i) the transition probability without measurement, (ii) the
transition probability with measurement. This is done for both the cases of
projective measurements and of generalized measurements. Among other
constraints, this quantifies a trade-off between high randomness in a
projective measurement and high measurement-modified transition probability. An
intermediate projective measurement can enhance a transition probability such
that the failure probability decreases by a factor of up to 2, but not by more.Comment: 23 pages, 5 figures, minor updat
The electromagnetic Nucleon to Delta transition in Chiral Effective Field Theory
We present a calculation of the three complex form factors parametrizing the
nucleon to Delta transition matrix element in the framework of chiral effective
field theory with explicit Delta degrees of freedom. The interplay between
short and long range physics is discussed and estimates for systematic
uncertainties due to higher order effect are given.Comment: Talk given at the 2nd international workshop "Shape of Hadrons",
April 27-29, 2006, Athens, Greec
- …