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A VLSI implementation of the collision avoidance switch protocol for CAMB tree LANs
To solve a performance bottle neck in random access LANs due to packet collisions and their resolution, collision avoidance switches are introduced. These switches allow random access protocols to achieve high performance by resolving collisions among packets. A conventional hardware implementation of these switches is the use of TTL chips. In this implementation; a handful of TTL chips are required to forma single switch (e.g., 18 TTL chips are needed for an implementation of the CAMB switch [7]). Thus, implementation of a complete network, which requires several of these switches, could very well result in a large and complex hardware system.Today's modern chip technology allows us to pack large quantity of logic in a single chip. By transferring the conventional implementation of the collision avoidance switches into a VLSI chip, the complexity of the resultant hardware is greatly reduced, not to mention the improvement in hardware performance and ease of packaging.This report provides an overall study of the collision avoidance protocols for the tree LANs with emphasis on the implementation of collision avoidance switches. Hardware implementations of sorne of these switches are discussed. And a VLSI implementation of the CAMB switch protocol is introduced
Wavemoth -- Fast spherical harmonic transforms by butterfly matrix compression
We present Wavemoth, an experimental open source code for computing scalar
spherical harmonic transforms (SHTs). Such transforms are ubiquitous in
astronomical data analysis. Our code performs substantially better than
existing publicly available codes due to improvements on two fronts. First, the
computational core is made more efficient by using small amounts of precomputed
data, as well as paying attention to CPU instruction pipelining and cache
usage. Second, Wavemoth makes use of a fast and numerically stable algorithm
based on compressing a set of linear operators in a precomputation step. The
resulting SHT scales as O(L^2 (log L)^2) for the resolution range of practical
interest, where L denotes the spherical harmonic truncation degree. For low and
medium-range resolutions, Wavemoth tends to be twice as fast as libpsht, which
is the current state of the art implementation for the HEALPix grid. At the
resolution of the Planck experiment, L ~ 4000, Wavemoth is between three and
six times faster than libpsht, depending on the computer architecture and the
required precision. Due to the experimental nature of the project, only
spherical harmonic synthesis is currently supported, although adding support or
spherical harmonic analysis should be trivial.Comment: 13 pages, 6 figures, accepted by ApJ
A predictive model of energy savings from top of rail friction control
In this paper the authors present a predictive model of train energy requirements due to the application of a top of rail friction modifier (TOR-FM) versus dry wheel / rail conditions. Using the VAMPIRE® Pro simulation package, train energy requirements are modeled for two sets of TOR-FM frictional conditions, one using full Kalker coefficients and the other by using a Kalker factor of 18%. Both scenarios use a top of rail saturated coefficient of friction of 0.35. Under both TOR-FM frictional conditions, train energy savings are shown for complete laps of the Transportation Technology Center Inc.’s (TTCI) Transit Test Track (TTT) loop, and also when isolating only the tangent section of the loop. However, the magnitude of energy savings varies greatly depending on the Kalker coefficient factor used, highlighting the need to model this relationship as accurately as possible. These simulation results are compared with data obtained from a field study, in which train energy savings of 5.3% (lap) and 7.8% (tangent) are shown due to the application of TOR-FM
Electron-induced proton knockout from neutron rich nuclei
We study the evolution of the \eep cross section on nuclei with increasing
asymmetry between the number of neutrons and protons. The calculations are done
within the framework of the nonrelativistic and relativistic distorted-wave
impulse approximation. In the nonrelativistic model phenomenological
Woods-Saxon and Hartree-Fock wave functions are used for the proton bound-state
wave functions, in the relativistic model the wave functions are solutions of
Dirac-Hartree equations. The models are first tested against experimental data
on Ca and Ca nuclei, and then they are applied to a set of
spherical calcium isotopes.Comment: 5 pages, 2 figures. contribution to the XIX International School on
Nuclear Physics, Neutron Physics and Applications, Varna (Bulgaria) September
19-25, 201
Effect of Long-lived Strongly Interacting Relic Particles on Big Bang Nucleosynthesis
It has been suggested that relic long-lived strongly interacting massive
particles (SIMPs, or particles) existed in the early universe. We study
effects of such long-lived unstable SIMPs on big bang nucleosynthesis (BBN)
assuming that such particles existed during the BBN epoch, but then decayed
long before they could be detected. The interaction strength between an
particle and a nucleon is assumed to be similar to that between nucleons. We
then calculate BBN in the presence of the unstable neutral charged
particles taking into account the capture of particles by nuclei to form
-nuclei. We also study the nuclear reactions and beta decays of -nuclei.
We find that SIMPs form bound states with normal nuclei during a relatively
early epoch of BBN. This leads to the production of heavy elements which remain
attached to them. Constraints on the abundance of particles during BBN
are derived from observationally inferred limits on the primordial light
element abundances. Particle models which predict long-lived colored particles
with lifetimes longer than 200 s are rejected based upon these
constraints.Comment: 19 pages, 4 figure
Weighing matrices and spherical codes
Mutually unbiased weighing matrices (MUWM) are closely related to an
antipodal spherical code with 4 angles. In the present paper, we clarify the
relationship between MUWM and the spherical sets, and give the complete
solution about the maximum size of a set of MUWM of weight 4 for any order.
Moreover we describe some natural generalization of a set of MUWM from the
viewpoint of spherical codes, and determine several maximum sizes of the
generalized sets. They include an affirmative answer of the problem of Best,
Kharaghani, and Ramp.Comment: Title is changed from "Association schemes related to weighing
matrices
Stiffness Characterization of Cold Recycled Mixtures
AbstractOne of the objectives within the European research project CoRePaSol (supported within the CEDR Transnational Program) was to summarize assessment and research of stiffness modulus of cold recycled mixes determined according to repeated indirect tensile stress test (IT-CY). In most cases the stiffness modulus values were compared to the values of indirect tensile strength (ITS), which is currently the most commonly used characteristic for proving the quality of a cold recycled mix. The first part of experimental measurements was focused on the standard cold recycled mixes, thus mixes whose aggregate skeleton is formed entirely by RAP and which contain either just the bituminous binder (bituminous emulsion or foamed bitumen), or a combination of one of these binders and a hydraulic binder (cement). Later also combinations with other types of recyclable materials were done and tested. Stiffness modulus and in most cases also the indirect tensile strength values were investigated from many points of view, e.g. the effect of different bituminous / hydraulic binder content on these characteristics, time-dependent progress in change of these characteristics, effect of testing temperature or the influence of fines addition on the stiffness modulus value. This paper therefore brings some summarization of the gained experience
Droplet activation of wet particles: development of the Wet CCN approach
Relationships between critical supersaturation required for activation and
particle dry diameter have been the primary means for experimentally
characterizing cloud condensation nuclei (CCN) activity; however, use of the
dry diameter inherently limits the application to cases where the dry
diameter can be used to accurately estimate solute volume. This study
challenges the requirement and proposes a new experimental approach, Wet
CCN, for studying CCN activity without the need for a drying step. The new
approach directly measures the subsaturated portion of the Köhler
curves. The experimental setup consists of a humidity-controlled
differential mobility analyzer and a CCN counter; wet diameter equilibrated
at known relative humidity is used to characterize CCN activity instead of
the dry diameter. The experimental approach was validated against ammonium
sulfate, glucose, and nonspherical ammonium oxalate monohydrate. Further,
the approach was applied to a mixture of nonspherical iodine oxide
particles. The Wet CCN approach successfully determined the hygroscopicity
of nonspherical particles by collapsing them into spherical, deliquesced
droplets. We further show that the Wet CCN approach offers unique insights
into the physical and chemical impacts of the aqueous phase on CCN activity; a
potential application is to investigate the impact of
evaporation/co-condensation of water-soluble semivolatile species on CCN
activity
Decoherence, fluctuations and Wigner function in neutron optics
We analyze the coherence properties of neutron wave packets, after they have
interacted with a phase shifter undergoing different kinds of statistical
fluctuations. We give a quantitative (and operational) definition of
decoherence and compare it to the standard deviation of the distribution of the
phase shifts. We find that in some cases the neutron ensemble is more coherent,
even though it has interacted with a wider (i.e. more disordered) distribution
of shifts. This feature is independent of the particular definition of
decoherence: this is shown by proposing and discussing an alternative
definition, based on the Wigner function, that displays a similar behavior. We
briefly discuss the notion of entropy of the shifts and find that, in general,
it does not correspond to that of decoherence of the neutron.Comment: 18 pages, 7 figure
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