323 research outputs found
The statistical properties of technical trading rules
A portfolio of 200 heterogeneous technical trading rules is tested for their directional
predictabilities on the DJIAI from 1988 to 1999.
We also explore several nonparametric techniques designed for brain research,
and detected possibly other forms of dependencies more significant than the traditional
linear autocorrelation for the time series.
The overall conditional mean directional predictability is 46%. 36 percent of the
rules have more than 50% directional predictability, and the top 20 percent rules has a
73% directional predictability, whereas the bottom 80 percent has a directional
predictability of 40%. Buy signals consistently generate higher predictability than sell
signals but do not commensurate with their respective risk levels. The relationship
between two sub-periods is not stable, while the difference between the conditional mean
directional predictability of buy only and sell only signals is highly significance.
The belief that most successful rules have a directional predictability of 25% to
50% coincides with the mode of distribution.
We observe counter intuitive relationship between volatility and directional
predictability. The results of directional predictability in a downtrend concur with the
argument that buy-and-hold strategy is not a suitable benchmark.
Attempts are made to tackle the issues of small sample bias, data snooping, size of
test window, bootstrap or t-test, and homogeneity. Issues are discussed on empirical
testing for their real world applications, statistical and non-statistical interpretations; also
randomness test; physical or biological science approach
Use of Amendments to Reduce Water Requirements for Stand Establishment of Small-Seeded Crops
Soil crusting after planting is a serious problem in stand establishment
of small-seeded crops in the Southwest. When crusting occurs in a
saline, warm soil, stand establishment problems are especially severe. It
is customary to use costly irrigation water to keep seedbed surfaces moist
after planting to reduce soil crusting and to lower soil temperatures.
Phosphoric acid (24% and 12%) and sulfuric acid (95%) were evaluated
to determine their effectiveness in reducing soil crusting and reducing
the amount of water required to obtain stands of sugarbeets, alfalfa,
wheat and barley.
Phosphoric acid, applied in 4-6 cm bands over the seed row at
planting and before irrigation, reduced crusting and increased sugarbeet
and alfalfa seedling emergence. Emerged seedlings from phosphoric acid
treated plots were larger and one irrigation (10-15 ha cm/ha) was saved
in stand establishment. Sulfuric acid applied in bands reduced soil
crusting. Soluble salts in the seed zone resulting from band application
of sulfuric acid killed or damaged seedlings. Sulfuric acid, when applied
in irrigation water to saline-sodic soils, improved plant growth and water
use efficiency
Captive broodstock management and photothermal induction of gonadal maturation in Gag, Mycteroperca microlepis, and Jewfish Epinephelus itajara, for controlled production of Fry
Processes affecting the emigration of reef fishes from reserve areas: ontogenetic migrations and habitat requirements of Haemulid Fishes
Vortex lines of the electromagnetic field
Relativistic definition of the phase of the electromagnetic field, involving
two Lorentz invariants, based on the Riemann-Silberstein vector is adopted to
extend our previous study [I. Bialynicki-Birula, Z. Bialynicka-Birula and C.
Sliwa, Phys. Rev. A 61, 032110 (2000)] of the motion of vortex lines embedded
in the solutions of wave equations from Schroedinger wave mechanics to Maxwell
theory. It is shown that time evolution of vortex lines has universal features;
in Maxwell theory it is very similar to that in Schroedinger wave mechanics.
Connection with some early work on geometrodynamics is established. Simple
examples of solutions of Maxwell equations with embedded vortex lines are
given. Vortex lines in Laguerre-Gaussian beams are treated in some detail.Comment: 11 pages, 6 figures, to be published in Phys. Rev.
Iso-singlet Down Quark Mixing And CP Violation Experiments
We confront the new physics models with extra iso-singlet down quarks in the
new CP violation experimental era with and
measurements, events, and
limits. The closeness of the new experimental results to the standard
model theory requires us to include full SM amplitudes in the analysis. In
models allowing mixing to a new isosinglet down quark, as in E, flavor
changing neutral currents are induced that allow a mediated contribution
to mixing and which bring in new phases. In ,
, and plots we still find much
larger regions in the four down quark model than in the SM, reaching down to
, , , and down to zero, all at 1. We elucidate
the nature of the cancellation in an order four down quark mixing
matrix element which satisfies the experiments and reduces the number of
independent angles and phases. We also evaluate tests of unitarity for the
CKM submatrix.Comment: 14 pages, 16 figures, REVTeX
Tunneling and propagation of vacuum bubbles on dynamical backgrounds
In the context of bubble universes produced by a first-order phase transition
with large nucleation rates compared to the inverse dynamical time scale of the
parent bubble, we extend the usual analysis to non-vacuum backgrounds. In
particular, we provide semi-analytic and numerical results for the modified
nucleation rate in FLRW backgrounds, as well as a parameter study of bubble
walls propagating into inhomogeneous (LTB) or FLRW spacetimes, both in the
thin-wall approximation. We show that in our model, matter in the background
often prevents bubbles from successful expansion and forces them to collapse.
For cases where they do expand, we give arguments why the effects on the
interior spacetime are small for a wide range of reasonable parameters and
discuss the limitations of the employed approximations.Comment: 29 pages, 8 figures, typos corrected, matches published versio
On the fourth-order accurate compact ADI scheme for solving the unsteady Nonlinear Coupled Burgers' Equations
The two-dimensional unsteady coupled Burgers' equations with moderate to
severe gradients, are solved numerically using higher-order accurate finite
difference schemes; namely the fourth-order accurate compact ADI scheme, and
the fourth-order accurate Du Fort Frankel scheme. The question of numerical
stability and convergence are presented. Comparisons are made between the
present schemes in terms of accuracy and computational efficiency for solving
problems with severe internal and boundary gradients. The present study shows
that the fourth-order compact ADI scheme is stable and efficient
Spinodal Decomposition in a Binary Polymer Mixture: Dynamic Self Consistent Field Theory and Monte Carlo Simulations
We investigate how the dynamics of a single chain influences the kinetics of
early stage phase separation in a symmetric binary polymer mixture. We consider
quenches from the disordered phase into the region of spinodal instability. On
a mean field level we approach this problem with two methods: a dynamical
extension of the self consistent field theory for Gaussian chains, with the
density variables evolving in time, and the method of the external potential
dynamics where the effective external fields are propagated in time. Different
wave vector dependencies of the kinetic coefficient are taken into account.
These early stages of spinodal decomposition are also studied through Monte
Carlo simulations employing the bond fluctuation model that maps the chains --
in our case with 64 effective segments -- on a coarse grained lattice. The
results obtained through self consistent field calculations and Monte Carlo
simulations can be compared because the time, length, and temperature scales
are mapped onto each other through the diffusion constant, the chain extension,
and the energy of mixing. The quantitative comparison of the relaxation rate of
the global structure factor shows that a kinetic coefficient according to the
Rouse model gives a much better agreement than a local, i.e. wave vector
independent, kinetic factor. Including fluctuations in the self consistent
field calculations leads to a shorter time span of spinodal behaviour and a
reduction of the relaxation rate for smaller wave vectors and prevents the
relaxation rate from becoming negative for larger values of the wave vector.
This is also in agreement with the simulation results.Comment: Phys.Rev.E in prin
A shooting algorithm for problems with singular arcs
In this article we propose a shooting algorithm for a class of optimal
control problems for which all control variables appear linearly. The shooting
system has, in the general case, more equations than unknowns and the
Gauss-Newton method is used to compute a zero of the shooting function. This
shooting algorithm is locally quadratically convergent if the derivative of the
shooting function is one-to-one at the solution. The main result of this paper
is to show that the latter holds whenever a sufficient condition for weak
optimality is satisfied. We note that this condition is very close to a second
order necessary condition. For the case when the shooting system can be reduced
to one having the same number of unknowns and equations (square system) we
prove that the mentioned sufficient condition guarantees the stability of the
optimal solution under small perturbations and the invertibility of the
Jacobian matrix of the shooting function associated to the perturbed problem.
We present numerical tests that validate our method.Comment: No. RR-7763 (2011); Journal of Optimization, Theory and Applications,
published as 'Online first', January 201
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