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

Mirage Cosmology of U(1) Gauge Field on Unstable D3 Brane Universe

An unstable $D3$-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

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