6,595 research outputs found
On a Possible Size/Color Relationship in the Kuiper Belt
Color measurements and albedo distributions introduce non-intuitive
observational biases in size-color relationships among Kuiper Belt Objects
(KBOs) that cannot be disentangled without a well characterized sample
population with systematic photometry. Peixinho et al. report that the form of
the KBO color distribution varies with absolute magnitude, H. However, Tegler
et al. find that KBO color distributions are a property of object
classification. We construct synthetic models of observed KBO colors based on
two B-R color distribution scenarios: color distribution dependent on H
magnitude (H-Model) and color distribution based on object classification
(Class-Model). These synthetic B-R color distributions were modified to account
for observational flux biases. We compare our synthetic B-R distributions to
the observed 'Hot' and 'Cold' detected objects from the Canada-France Ecliptic
Plane Survey and the Meudon Multicolor Survey. For both surveys, the Hot
population color distribution rejects the H-Model, but is well described by the
Class-Model. The Cold objects reject the H-Model, but the Class-Model (while
not statistically rejected) also does not provide a compelling match for data.
Although we formally reject models where the structure of the color
distribution is a strong function of H magnitude, we also do not find that a
simple dependence of color distribution on orbit classification is sufficient
to describe the color distribution of classical KBOs
Tentative Detection of the Rotation of Eris
We report a multi-week sequence of B-band photometric measurements of the
dwarf planet Eris using the {\it Swift} satellite. The use of an observatory in
low-Earth orbit provides better temporal sampling than is available with a
ground-based telescope. We find no compelling evidence for an unusually slow
rotation period of multiple days, as has been suggested previously. A
1.08 day rotation period is marginally detected at a modest level of
statistical confidence (97%). Analysis of the combination of the
data with the ground-based B-band measurements of \citet{2007AJ....133...26R}
returns the same period (1.08 day) at a slightly higher statistical
confidence (99%).Comment: Accepted to Icarus 2008-Aug-19. 19 pages total, including 4 figures
and 1 tabl
Polaron effective mass from Monte Carlo simulations
A new Monte Carlo algorithm for calculating polaron effective mass is
proposed. It is based on the path-integral representation of a partial
partition function with fixed total quasi-momentum. Phonon degrees of freedom
are integrated out analytically resulting in a single-electron system with
retarded self-interaction and open boundary conditions in imaginary time. The
effective mass is inversely proportional to the covariance of total energy
calculated on an electron trajectory and the square distance between ends of
the trajectory. The method has no limitations on values of model parameters and
on the size and dimensionality of the system although large statistics is
required for stable numerical results. The method is tested on the
one-dimensional Holstein model for which simulation results are presented.Comment: 4 pages + 1 figure, RevTeX. Accepted for publication as a Rapid
Communication in Phys.Rev.
Optimal coupling of entangled photons into single-mode optical fibers
We present a consistent multimode theory that describes the coupling of
single photons generated by collinear Type-I parametric down-conversion into
single-mode optical fibers. We have calculated an analytic expression for the
fiber diameter which maximizes the pair photon count rate. For a given focal
length and wavelength, a lower limit of the fiber diameter for satisfactory
coupling is obtained
Evaluation of the energy transfer in the char zone during ablation. Part 2: In-depth response of ablative composites, volume 1
The decomposition of ablative composites is described along with the transport phenomena of pyrolysis gases which result from the decomposition of these plastics as they flow through the porous char of char-forming ablators. The pyrolysis products are those formed by the thermal degradation of nylon-phenolic resin and silicone elastomer composites. Emphasis is placed on the nature and extent of chemical reactions of the pyrolysis products and the char, along with the energy absorbed by the combined pyrolysis and char zone. Chemical reactions with thermodynamically consistent kinetic data are determined in order to develop a realistic analysis for predicting the thermal performance of ablative heat shields
On the Localization of One-Photon States
Single photon states with arbitrarily fast asymptotic power-law fall-off of
energy density and photodetection rate are explicitly constructed. This goes
beyond the recently discovered tenth power-law of the Hellwarth-Nouchi photon
which itself superseded the long-standing seventh power-law of the Amrein
photon.Comment: 7 pages, tex, no figure
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Holistic facial composite systems: are they compatible with witness recall?
Facial composite systems offer a particular challenge to human-computer interaction as they must facilitate several cognitively complex tasks and also aid communication between the operator and the witness. This paper presents the findings from a survey conducted with UK police composite operators that explored some of the issues involved in composite construction. A particular emphasis was placed on the information that witnesses report and its compatibility with both the composite system interface and the underlying construction method used by the system
Computation of the equilibrium composition of reacting gas-solid mixtures with material and energy balance constraints Status report
Equilibrium composition computed for reacting- gas-solid composite materials using material and energy constraint
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The “Ethics” of Teaching Ethical Hacking
Programs teaching ethical hacking are growing steadily. The argument for teaching ethical hacking focuses on the need to better understand attacks and attackers. However, some believe that teaching offensive hacking skills increases risk to society by drawing students toward criminal acts. The proponents of teaching ethical hacking argue that ethics training permeates related curriculum providing students with ample preparation to understand the risks and choose healthy behaviors. This paper examines mechanisms beyond classroom-based curriculum to minimize the risk of students committing criminal acts with the skills acquired in an ethical hacking course
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