7,263 research outputs found
Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes
We report two-dimensional MHD simulations which demonstrate that photospheric
5-min oscillations can leak into the chromosphere inside small-scale vertical
magnetic flux tubes. The results of our numerical experiments are compatible
with those inferred from simultaneous spectropolarimetric observations of the
photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter
(TIP) at 10830 A. We conclude that the efficiency of energy exchange by
radiation in the solar photosphere can lead to a significant reduction of the
cut-off frequency and may allow for the propagation of the 5 minutes waves
vertically into the chromosphere.Comment: accepted by ApJ
The Effect of Fines on the Surface Characteristics of Recycled Paper
With the steady increase in recycling comes an increasing need to understand the mechanisms involved with reused wood fibers. The purpose of this experiment is to determine the effects of fines on the surface characteristics of recycled paper, and to predict how an increase or decrease in fines loading might affect printing.
To meet these objectives, fines were removed from both virgin pulp and mill broke of similar composition. Each fines fraction was then reapplied to each long fraction at 0, 5, 10, and 15 percent loading by weight. British handsheets were made and evaluated for surface strength, absorbency, smoothness, and optical properties.
Fines from recycled stock were shown to be much less active than fines for virgin stock. Increasing recycled fines showed only a very slight improvement in surface strength, a reduction in liquid penetration, increased scattering/opacity, and slightly decreased brightness. No conclusions could be made for effects on smoothness. These results indicate that increased recycled fines would increase hold out and reduce ink penetration and ink show through.
Overall, with the exception of opacity, fines appear to play a much smaller role in paper making when the paper is recycled
Team leadership : core competencies in children\u27s ministries
https://place.asburyseminary.edu/ecommonsatsdissertations/2470/thumbnail.jp
Pattern formation during diffusion limited transformations in solids
We develop a description of diffusion limited growth in solid-solid
transformations, which are strongly influenced by elastic effects. Density
differences and structural transformations provoke stresses at interfaces,
which affect the phase equilibrium conditions. We formulate equations for the
interface kinetics similar to dendritic growth and study the growth of a stable
phase from a metastable solid in both a channel geometry and in free space. We
perform sharp interface calculations based on Green's function methods and
phase field simulations, supplemented by analytical investigations. For pure
dilatational transformations we find a single growing finger with symmetry
breaking at higher driving forces, whereas for shear transformations the
emergence of twin structures can be favorable. We predict the steady state
shapes and propagation velocities, which can be higher than in conventional
dendritic growth.Comment: submitted to Philosophical Magazin
Crack growth resistance in metallic alloys: The role of isotropic versus kinematic hardening
The sensitivity of crack growth resistance to the choice of isotropic or
kinematic hardening is investigated. Monotonic mode I crack advance under small
scale yielding conditions is modelled via a cohesive zone formulation endowed
with a traction-separation law. R-curves are computed for materials that
exhibit linear or power law hardening. Kinematic hardening leads to an enhanced
crack growth resistance relative to isotropic hardening. Moreover, kinematic
hardening requires greater crack extension to achieve the steady state. These
differences are traced to the non-proportional loading of material elements
near the crack tip as the crack advances. The sensitivity of the R-curve to the
cohesive zone properties and to the level of material strain hardening is
explored for both isotropic and kinematic hardening
Mode I crack tip fields: Strain gradient plasticity theory versus J2 flow theory
The mode I crack tip asymptotic response of a solid characterised by strain
gradient plasticity is investigated. It is found that elastic strains dominate
plastic strains near the crack tip, and thus the Cauchy stress and the strain
state are given asymptotically by the elastic K-field. This crack tip elastic
zone is embedded within an annular elasto-plastic zone. This feature is
predicted by both a crack tip asymptotic analysis and a finite element
computation. When small scale yielding applies, three distinct regimes exist:
an outer elastic K field, an intermediate elasto-plastic field, and an inner
elastic K field. The inner elastic core significantly influences the crack
opening profile. Crack tip plasticity is suppressed when the material length
scale of the gradient theory is on the order of the plastic zone size
estimation, as dictated by the remote stress intensity factor. A generalized
J-integral for strain gradient plasticity is stated and used to characterise
the asymptotic response ahead of a short crack. Finite element analysis of a
cracked three point bend specimen reveals that the crack tip elastic zone
persists in the presence of bulk plasticity and an outer J-field
Transcendental Thermodynamics
Thermodynamics is often viewed as a narrow, introspective discipline, trapped by its origins in the 18th and 19th centuries. By dramatic contrast, we show that the Fourth Law of Thermodynamics provides explanations and interpretations of all natural events, extending across artificial boundaries of tradition- al academic disciplines. The Fourth Law of Thermodynamics states that far-from-equilibrium systems increase entropy at the maximum rate available to them. This broadly inclusive paradigm applies to systems from molecules, to organisms, to the biosphere. The Fourth Law is the Law of Evolution. All systems that communicate with their environment exhibit self-organization and self-optimization, enabling the emergence and the evolution of life as a sustained optimization of entropy increase
Analyzing and Predicting Verification of Data-Aware Process Models – a Case Study with Spectrum Auctions
Verification techniques play an essential role in detecting undesirable behaviors in many applications like spectrum auctions. By verifying an auction design, one can detect the least favorable outcomes, e.g., the lowest revenue of an auctioneer. However, verification may be infeasible in practice, given the vast size of the state space on the one hand and the large number of properties to be verified on the other hand. To overcome this challenge, we leverage machine-learning techniques. In particular, we create a dataset by verifying properties of a spectrum auction first. Second, we use this dataset to analyze and predict outcomes of the auction and characteristics of the verification procedure. To evaluate the usefulness of machine learning in the given scenario, we consider prediction quality and feature importance. In our experiments, we observe that prediction models can capture relationships in our dataset well, though one needs to be careful to obtain a representative and sufficiently large training dataset. While the focus of this article is on a specific verification scenario, our analysis approach is general and can be adapted to other domains
Heavy Quark Fragmentation to Baryons Containing Two Heavy Quarks
We discuss the fragmentation of a heavy quark to a baryon containing two
heavy quarks of mass . In this limit the heavy quarks
first combine perturbatively into a compact diquark with a radius small
compared to , which interacts with the light hadronic
degrees of freedom exactly as does a heavy antiquark. The subsequent evolution
of this diquark to a baryon is identical to the fragmentation of a
heavy antiquark to a meson. We apply this analysis to the production of baryons
of the form , , and .Comment: 9 pages, 1 figure included, uses harvmac.tex and epsf.tex, UCSD/PTH
93-11, CALT-68-1868, SLAC-PUB-622
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