770 research outputs found
YIELD PREDICTION IN 60ft\u3csup\u3e2\u3c/sup\u3e GRIDS
Large detailed yield databases incorporating GPS makes it possible to predict yield on a small scale. The objective of this study was to determine how closely yield could be predicted in grids of 60-ft2 units. Com and soybean yields were averaged to the 60-ft2 grid. The yields were modeled on previous yields, soil fertility, soil type, and terrain variables. Soil fertility variables were kriged from a I-acre grid to the 60-ft2 grid. Terrain data and soil type data were available at the same scale. Multiple regression models and models with spatial correlation determined from yield semivariograms differed some. Previous yields and wetness were the most significant variables. Soil variables alone were not good predictors
Rain, power laws, and advection
Localized rain events have been found to follow power-law size and duration
distributions over several decades, suggesting parallels between precipitation
and seismic activity [O. Peters et al., PRL 88, 018701 (2002)]. Similar power
laws are generated by treating rain as a passive tracer undergoing advection in
a velocity field generated by a two-dimensional system of point vortices.Comment: 7 pages, 4 figure
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Pt-, Rh-, Ru-, and Cu-Single-Wall Carbon Nanotubes Are Exceptional Candidates for Design of Anti-Viral Surfaces: A Theoretical Study
As SARS-CoV-2 is spreading rapidly around the globe, adopting proper actions for confronting and protecting against this virus is an essential and unmet task. Reactive oxygen species (ROS) promoting molecules such as peroxides are detrimental to many viruses, including coronaviruses. In this paper, metal decorated single-wall carbon nanotubes (SWCNTs) were evaluated for hydrogen peroxide (H2O2) adsorption for potential use for designing viral inactivation surfaces. We employed first-principles methods based on the density functional theory (DFT) to investigate the capture of an individual H2O2 molecule on pristine and metal (Pt, Pd, Ni, Cu, Rh, or Ru) decorated SWCNTs. Although the single H2O2 molecule is weakly physisorbed on pristine SWCNT, a significant improvement on its adsorption energy was found by utilizing metal functionalized SWCNT as the adsorbent. It was revealed that Rh-SWCNT and Ru-SWCNT systems demonstrate outstanding performance for H2O2 adsorption. Furthermore, we discovered through calculations that Pt- and Cu-decorated SWNCT-H2O2 systems show high potential for filters for virus removal and inactivation with a very long shelf-life (2.2 × 1012 and 1.9 × 108 years, respectively). The strong adsorption of metal decorated SWCNTs and the long shelf-life of these nanomaterials suggest they are exceptional candidates for designing personal protection equipment against viruses
Controlling the direction of steady electric fields in liquid using non-antiperiodic potentials
When applying an oscillatory electric potential to an electrolyte solution,
it is commonly assumed that the choice of which electrode is grounded or
powered does not matter because the time-average of the electric potential is
zero. Recent theoretical, numerical, and experimental work, however, has
established that certain types of multimodal oscillatory potentials that are
"non-antiperodic" can induce a net steady field toward either the grounded or
powered electrode [Hashemi et al., Phys. Rev. E 105, 065001 (2022)]. Here, we
elaborate on the nature of these steady fields through numerical and
theoretical analyses of the asymmetric rectified electric field (AREF) that
occurs in electrolytes where the cations and anions have different mobilities.
We demonstrate that AREFs induced by a non-antiperiodic electric potential,
e.g., by a two-mode waveform with modes at 2 and 3 Hz, invariably yields a
steady field that is spatially dissymmetric between two parallel electrodes,
such that swapping which electrode is powered changes the direction of the
field. Additionally, using a perturbation expansion, we demonstrate that the
dissymmetric AREF occurs due to odd nonlinear orders of the applied potential.
We further generalize the theory by demonstrating that the dissymmetric field
occurs for all classes of zero-time-average (no dc bias) periodic potentials,
including triangular and rectangular pulses, and we discuss how these steady
fields can tremendously change the interpretation, design, and applications of
electrochemical and electrokinetic systems
Diffusive transport and self-consistent dynamics in coupled maps
The study of diffusion in Hamiltonian systems has been a problem of interest
for a number of years.
In this paper we explore the influence of self-consistency on the diffusion
properties of systems described by coupled symplectic maps. Self-consistency,
i.e. the back-influence of the transported quantity on the velocity field of
the driving flow, despite of its critical importance, is usually overlooked in
the description of realistic systems, for example in plasma physics. We propose
a class of self-consistent models consisting of an ensemble of maps globally
coupled through a mean field. Depending on the kind of coupling, two different
general types of self-consistent maps are considered: maps coupled to the field
only through the phase, and fully coupled maps, i.e. through the phase and the
amplitude of the external field. The analogies and differences of the diffusion
properties of these two kinds of maps are discussed in detail.Comment: 13 pages, 14 figure
Relative Equilibria in the Four-Vortex Problem with Two Pairs of Equal Vorticities
We examine in detail the relative equilibria in the four-vortex problem where
two pairs of vortices have equal strength, that is, \Gamma_1 = \Gamma_2 = 1 and
\Gamma_3 = \Gamma_4 = m where m is a nonzero real parameter. One main result is
that for m > 0, the convex configurations all contain a line of symmetry,
forming a rhombus or an isosceles trapezoid. The rhombus solutions exist for
all m but the isosceles trapezoid case exists only when m is positive. In fact,
there exist asymmetric convex configurations when m < 0. In contrast to the
Newtonian four-body problem with two equal pairs of masses, where the symmetry
of all convex central configurations is unproven, the equations in the vortex
case are easier to handle, allowing for a complete classification of all
solutions. Precise counts on the number and type of solutions (equivalence
classes) for different values of m, as well as a description of some of the
bifurcations that occur, are provided. Our techniques involve a combination of
analysis and modern and computational algebraic geometry
Synchronization and oscillator death in oscillatory media with stirring
The effect of stirring in an inhomogeneous oscillatory medium is
investigated. We show that the stirring rate can control the macroscopic
behavior of the system producing collective oscillations (synchronization) or
complete quenching of the oscillations (oscillator death). We interpret the
homogenization rate due to mixing as a measure of global coupling and compare
the phase diagrams of stirred oscillatory media and of populations of globally
coupled oscillators.Comment: to appear in Phys. Rev. Let
Optical Fiber Communication Systems Based on End-to-End Deep Learning: (Invited Paper)
We investigate end-to-end optimized optical transmission systems based on feedforward or bidirectional recurrent
neural networks (BRNN) and deep learning. In particular, we report the first experimental demonstration of a BRNN auto-encoder,
highlighting the performance improvement achieved with recurrent processing for communication over dispersive nonlinear channels
Kinematic studies of transport across an island wake, with application to the Canary islands
Transport from nutrient-rich coastal upwellings is a key factor influencing
biological activity in surrounding waters and even in the open ocean. The rich
upwelling in the North-Western African coast is known to interact strongly with
the wake of the Canary islands, giving rise to filaments and other mesoscale
structures of increased productivity. Motivated by this scenario, we introduce
a simplified two-dimensional kinematic flow describing the wake of an island in
a stream, and study the conditions under which there is a net transport of
substances across the wake. For small vorticity values in the wake, it acts as
a barrier, but there is a transition when increasing vorticity so that for
values appropriate to the Canary area, it entrains fluid and enhances
cross-wake transport.Comment: 28 pages, 13 figure
Echoes in classical dynamical systems
Echoes arise when external manipulations to a system induce a reversal of its
time evolution that leads to a more or less perfect recovery of the initial
state. We discuss the accuracy with which a cloud of trajectories returns to
the initial state in classical dynamical systems that are exposed to additive
noise and small differences in the equations of motion for forward and backward
evolution. The cases of integrable and chaotic motion and small or large noise
are studied in some detail and many different dynamical laws are identified.
Experimental tests in 2-d flows that show chaotic advection are proposed.Comment: to be published in J. Phys.
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