2,454 research outputs found
The Bouncing Jet: A Newtonian Liquid Rebounding off a Free Surface
We find that a liquid jet can bounce off a bath of the same liquid if the
bath is moving horizontally with respect to the jet. Previous observations of
jets rebounding off a bath (e.g. Kaye effect) have been reported only for
non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian
fluids, including mineral oil poured by hand. A thin layer of air separates the
bouncing jet from the bath, and the relative motion replenishes the film of
air. Jets with one or two bounces are stable for a range of viscosity, jet flow
rate and velocity, and bath velocity. The bouncing phenomenon exhibits
hysteresis and multiple steady states.Comment: 9 pages, 7 figures. submitted to Physical Review
Assisted Tachyonic Inflation
The model of inflation with a single tachyon field generates larger
anisotropy and has difficulties in describing the formation of the Universe .
In this paper we consider a model with multi tachyon fields and study the
assisted inflationary solution. Our results show that this model satisfies the
observation.Comment: 5 pages, no figures, a revised version and reference adde
Spectrum of Curvature Perturbation of Multi-field Inflation with Small-Field Potential
In this paper, we have studied the spectrum of curvature perturbation of
multi-field inflation with general small-field potential. We assume that the
isocurvature perturbation may be neglected, and by using the Sasaki-Stewart
formalism, we found that the spectrum may be redder or bluer than of its
corresponding single field. The result depends upon the values of fields and
their effective masses at the horizon-crossing time. We discuss the relevant
cases.Comment: 8 pages, no figure, to publish in JCA
Self calibration iso-pathlength point in cylindrical tissue geometry: Solution of steady-state photon diffusion based on the extrapolated zero-boundary
Near-infrared optical techniques permit tissue diagnosis by surface measurement. However, the geometrical shape of this interface profiles the intensity of the surface measurement, which is found to have an iso-pathlength (IPL) point allowing for absorption identification independent of tissue scattering. The IPL point was projected in Monte Carlo (MC) simulation, validated experimentally in cylindrical tissues, but remains under-appreciated through analytical approaches. In this work, we present an analytical solution of an IPL point for steady-state diffusion based on the extrapolated zero-boundary condition. The same IPL points were found when comparing this solution to 3-D MC simulations for a tissue radius range of 5-8mm.Electrical and Computer Engineerin
Effect of waste PET and CR as sand replacement on the durability and acoustical properties of semi dense asphalt (SDA) mixtures
Construction materials research is consistently striving to improve sustainability, in the reduction of virgin materials by use of otherwise landfilled materials of the same purpose. Crumb rubber (CR) from end-of-life tires
and polyethylene terephthalate (PET) from post-consumer liquid containers are two of the most commonly circulating forms of waste in the urban environment. This study investigated the replacement of semi-dense asphalt
(SDA) sand by untreated mechanically shredded CR and PET, at 2.5 and 5.1% respectively by total mass of aggregates. The mixtures were evaluated by compactability, indirect tensile strength (ITS), fracture energy (FE), water
sensitivity by ITS ratio (ITSR%), surface texture and acoustic absorption tests. After compaction, the CR and PET
samples experienced an elastic rebound effect, which resulted in the air voids being higher than expected.
Also, the PET samples required more compaction energy. The ITS, FE and ITSR% were significantly reduced
with CR replacement, while the PET mixture performed similar to the control, especially in FE. The sound absorption was related more to the air voids than the material type, although the absorption coefficients of the SDA was
not found to be significant. The CR reduced the texture level of the pavement significantly in comparison to the
control, while texture level remained the same for the PET mixture, despite a difference in the porosity. Further
studies were performed using a mixture replacing PET by aggregate volume at 5.1%, comparing it to the control
SDA in terms of low temperature cracking and permanent deformation at 50 °C. While the compactability of the
PET mixture was now similar to that of the control, the resistance to cracking and permanent deformation was
lower. Although the PET mixture had some interesting ductility properties, the replacement of sand by CR and
PET is not recommended, and the more common use as asphalt mixture modifiers with fairly low addition contents of around 1% is more sound
Urban mining for asphalt pavements: A review
The increasing consumption of natural resources for road construction and generation of urban waste
materials are two global ecological problems. Urban mining aims to convert waste materials into raw
materials for industrial production, and as a result, address both problems simultaneously. This study
explores the potential of urban mining for asphalt pavement surface courses. In the first part, as each
country/region has its unique challenge with waste materials, a screening method taking the EU and
Switzerland as case studies is employed to select waste materials that potentially qualify for asphalt
surface courses. The second part presents a review of laboratory studies regarding the performance of
asphalt mixtures with selected waste materials. Based on the industrial experience, the third part dis-
cusses the technology, specifications and cost considerations of asphalt surface courses with waste
materials. Furthermore, the technical maturities for using waste materials are estimated in terms of
technology readiness level (TRL). Overall, the paper demonstrates that various categories of waste ma-
terials can be potentially used in asphalt surface courses, revealing urban mining opportunities. The
selected waste materials may improve the performance of asphalt mixtures with optimization of several
factors, such as the fraction size and amounts of waste materials for addition or replacement. The TRL
results showed that using crumb rubber (wet process) and steel slag are currently more mature than
using other waste materials in asphalt surface course
Mirage Cosmology of U(1) Gauge Field on Unstable D3 Brane Universe
An unstable -brane universe governed by the DBI action of the tachyon
field minimally coupled to a U(1) gauge boson is examined. The cosmological
evolution of this coupled system, is further analyzed, in terms of the
expansion rate of the inflating brane, which is highly affected by the presence
of the tachyonic and gauge field charges. We show, that the minimal coupling
makes the effective brane density less divergent. However, for some sectors of
the theory the tachyon is not able to regulate it in an efficient fashion.
Also, a detailed analysis of the dependance of the effective brane density on
the scale factor of the universe is performed, which leads to various
cosmological models.Comment: ReVTeX format 20 pages; v2 1 figure added, one additional paragraph
with extra comments added, enlarged list of references, version to appear in
JHE
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