6,542 research outputs found
Scattering theory without large-distance asymptotics
In conventional scattering theory, to obtain an explicit result, one imposes
a precondition that the distance between target and observer is infinite. With
the help of this precondition, one can asymptotically replace the Hankel
function and the Bessel function with the sine functions so that one can
achieve an explicit result. Nevertheless, after such a treatment, the
information of the distance between target and observer is inevitably lost. In
this paper, we show that such a precondition is not necessary: without losing
any information of distance, one can still obtain an explicit result of a
scattering rigorously. In other words, we give an rigorous explicit scattering
result which contains the information of distance between target and observer.
We show that at a finite distance, a modification factor --- the Bessel
polynomial --- appears in the scattering amplitude, and, consequently, the
cross section depends on the distance, the outgoing wave-front surface is no
longer a sphere, and, besides the phase shift, there is an additional phase
(the argument of the Bessel polynomial) appears in the scattering wave
function
Crossing by a single scalar field coupling with matter and the observational constraints
Motivated by Yang-Mills dark energy model, we propose a new model by
introducing a logarithmic correction. we find that this model can avoid the
coincidence problem naturally and gives an equation of state smoothly
crossing -1 if an interaction between dark energy and dark matter exists. It
has a stable tracker solution as well. To confront with observations based on
the combined data of SNIa, BAO, CMB and Hubble parameter, we obtain the best
fit values of the parameters with errors for the
noncoupled model: ,
, and for the coupled model with a decaying
rate : ,
. In particular, it is found that the
non-coupled model has a dynamic evolution almost undistinguishable to
CDM at the late-time Universe.Comment: 12 pages, 3 figures, the published versio
Where is Mr. Berg ?
Where is Mr. Berg? is a narrative short film that contemplates the relationship between parents and their children. This paper documents the growth of the story, how the story gets shaped and blossomed from the seed, and how the film is produced with minimal compromise to the original idea during the pandemic. I, as the Director and Director of Photography in this film, will break down the tangible process from different mindsets and visions in this thesis from scene to screen
PocketCare: Tracking the Flu with Mobile Phones using Partial Observations of Proximity and Symptoms
Mobile phones provide a powerful sensing platform that researchers may adopt
to understand proximity interactions among people and the diffusion, through
these interactions, of diseases, behaviors, and opinions. However, it remains a
challenge to track the proximity-based interactions of a whole community and
then model the social diffusion of diseases and behaviors starting from the
observations of a small fraction of the volunteer population. In this paper, we
propose a novel approach that tries to connect together these sparse
observations using a model of how individuals interact with each other and how
social interactions happen in terms of a sequence of proximity interactions. We
apply our approach to track the spreading of flu in the spatial-proximity
network of a 3000-people university campus by mobilizing 300 volunteers from
this population to monitor nearby mobile phones through Bluetooth scanning and
to daily report flu symptoms about and around them. Our aim is to predict the
likelihood for an individual to get flu based on how often her/his daily
routine intersects with those of the volunteers. Thus, we use the daily
routines of the volunteers to build a model of the volunteers as well as of the
non-volunteers. Our results show that we can predict flu infection two weeks
ahead of time with an average precision from 0.24 to 0.35 depending on the
amount of information. This precision is six to nine times higher than with a
random guess model. At the population level, we can predict infectious
population in a two-week window with an r-squared value of 0.95 (a random-guess
model obtains an r-squared value of 0.2). These results point to an innovative
approach for tracking individuals who have interacted with people showing
symptoms, allowing us to warn those in danger of infection and to inform health
researchers about the progression of contact-induced diseases
Synthesis, structure and photoluminescence of (HgCl3)n (C6NO2H6)n(C6NO2H5)n•nH2O
A new isonicotinic acid compound with infinite mercury halide anionic chains, (HgCl3)n (C6NO2H6)n(C6NO2H5)n•nH2O (1), was obtained from the hydrothermal reaction and structurally characterized by X-ray single diffraction. The title compound is characteristic of a one-dimensional structure, based on one-dimensional (HgCl3)- anionic chains, protonated isonicotinic acid, neutral isonicotinic acid molecules and lattice water molecules. The protonated isonicotinic acid, neutral isonicotinic acid molecules and lattice water molecules are interconnected via hydrogen bonds to form a three-dimensional supramolecular framework. The (HgCl3)- anionic chains are anchored in the voids of the supramolecular framework via hydrogen bonds. Photoluminescent investigation reveals that the title compound displays a strong emission in blue region. The emission band is identified as the π-π* transitions of the isonicotinic acid moieties.KEY WORDS: Crystal, Isonicotinic, Halide, Mercury, Photoluminescence  Bull. Chem. Soc. Ethiop. 2011, 25(2), 233-238
Hydrodynamic Modeiingfor Tanjung Kepah, Perak
The objective ofthis report is to detail the progress ofthe computer simulation of coastal
hydrodynamic, which is MIKE 21. Firstly, a study has been carried out at Tanjung
Kepah, Lumut to study the impacts of wave distribution patterns in that area. Tanjung
Kepah is chosen because there are erosion activities going on at the coast. Tanjung Kepah
is studied and modeled with the MIKE 21 software to provide the best solution to prevent
the erosion acivities. The primary data and secondary data on oceanographical condition,
site topography and bathymetry are collected from various sources. Thus, the existing
hydraulic environment conditions are analyzed based on the parameters relating to
currents, tides, waves and wind. And also, the wave data analysis is carried out to predict
the extreme wave heights in various return periods. The execution of computer modeling
will cover several phases, which are bathymetry modeling, simulation of wave analysis,
and simulation of coastal hydrodynamic incorporated with wave radiation stress. The
simulation has been successfully completed, the results are interpreted and analyzed.
From the analysis, the incoming waves at a distance of 100 meter from the Tanjung
Kepah coast have a maximum wave height of 0.70 meter above ACD during spring high
tide at return period of 50 years. The incoming current flow is 0.22 m/s at 320° during
flood tide and outgoing current flow is 0.27 m/s at 138° during ebb tide. Thus, this report
can be used by the authorities as a reference in order to study the existing coastal
hydrodynamic of Tanjung Kepah and decide the preventive actions to be taken to protect
the coast. Besides that, the authorities can use this report to do a preliminary design of
protective structure, such as breakwaters
Dynamical Mean Field Theory for the Bose-Hubbard Model
The dynamical mean field theory (DMFT), which is successful in the study of
strongly correlated fermions, was recently extended to boson systems [Phys.
Rev. B {\textbf 77}, 235106 (2008)]. In this paper, we employ the bosonic DMFT
to study the Bose-Hubbard model which describes on-site interacting bosons in a
lattice. Using exact diagonalization as the impurity solver, we get the DMFT
solutions for the Green's function, the occupation density, as well as the
condensate fraction on a Bethe lattice. Various phases are identified: the Mott
insulator, the Bose-Einstein condensed (BEC) phase, and the normal phase. At
finite temperatures, we obtain the crossover between the Mott-like regime and
the normal phase, as well as the BEC-to-normal phase transition. Phase diagrams
on the plane and on the plane are
produced ( is the scaled hopping amplitude). We compare our results
with the previous ones, and discuss the implication of these results to
experiments.Comment: 11 pages, 8 figure
Probability Thermodynamics and Probability Quantum Field
In this paper, we introduce probability thermodynamics and probability
quantum fields. By probability we mean that there is an unknown operator,
physical or nonphysical, whose eigenvalues obey a certain statistical
distribution. Eigenvalue spectra define spectral functions. Various
thermodynamic quantities in thermodynamics and effective actions in quantum
field theory are all spectral functions. In the scheme, eigenvalues obey a
probability distribution, so a probability distribution determines a family of
spectral functions in thermodynamics and in quantum field theory. This leads to
probability thermodynamics and probability quantum fields determined by a
probability distribution. There are two types of spectra: lower bounded
spectra, corresponding to the probability distribution with nonnegative random
variables, and the lower unbounded spectra, corresponding to probability
distributions with negative random variables. For lower unbounded spectra, we
use the generalized definition of spectral functions. In some cases, we
encounter divergences. We remove the divergence by a renormalization procedure.
Moreover, in virtue of spectral theory in physics, we generalize some concepts
in probability theory. For example, the moment generating function in
probability theory does not always exist. We redefine the moment generating
function as the generalized heat kernel, which makes the concept definable when
the definition in probability theory fails. As examples, we construct examples
corresponding to some probability distributions. Thermodynamic quantities,
vacuum amplitudes, one-loop effective actions, and vacuum energies for various
probability distributions are presented
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