Evaluation of Mix Design Methods for Reclaimed Asphalt Pavement Mixes with Foamed Bitumen

AbstractThe main objective of this work is to evaluate the use of two mix design procedures for designing bituminous pavement mixes with foamed bitumen. Mix design was carried out following the South African and Caltrans guidelines. The RAP materials used for mix design were collected from the NH-5, Chennai-Tada section. Using foamed bitumen produced from Wirtgen WLB 10 foaming equipment, a mix with RAP material, virgin aggregate and active filler were produced in the pug mill mixer. Marshall compaction effort was used for fabricating the samples. Using the indirect tensile strength test on dry and wet specimens, the optimum binder content was determined. It was seen that the two mix design procedure adopted showed different mix constituents despite using the same RAP source

Tailored fuel injection within a Mach 12 shape transitioning scramjet

Three-dimensional computational fluid dynamic simulations were performed for the Mach 12 Rectangular-to-Elliptical Shape-Transitioning scramjet. Present injector arrangements at the combustor entrance displayed low jet penetration, resulting in a oxygen-based combustion efficiency of 84.9%. It is proposed to convert three cowl-side injectors into one larger injector located further upstream. To support this, injector configurations were investigated computationally, taking injectors optimised for penetration at lower Mach numbers, and evaluating their performance at higher Mach number flight conditions. It was determined that reduced performance of these optimised injectors was encountered at scramjet flight conditions above their design point, with circular injectors at equal or greater injection angles displaying greater penetration and mixing capabilities

Numerical study of the effect of wall temperature profiles on the premixed methane–air flame dynamics in a narrow channel

Time-accurate simulations of premixed CH/air flame in a narrow, heated channel are performed using the DRM-19 reaction mechanism. The effect of different wall temperature profiles on the flame dynamics is investigated for three different inflow velocity conditions. At a low inflow velocity of 0.2 m s, the flame shows instabilities in the form of spatial oscillations and even flame extinction. With the increase of the inflow velocity, flames are prone to showing more stability at a medium inflow velocity of 0.4 m s, and eventually show flame stabilisation at a high inflow velocity condition of 0.8 m s for all the wall temperature profiles examined. The total chemical heat release rate and total gas-solid heat exchange rate are found to have a combined effect on the flame propagation speed that determines flame behaviours. Since the flame behaviours in terms of the oscillation frequency and amplitude for spatially oscillating flames, or the stream-wise stabilisation location for steady-state flames, are very sensitive to the chosen wall temperature profile, a "real" conjugate heat transfer model is recommended in order to capture all of the relevant combustion physics accurately

On the influence of modelling choices on combustion in narrow channels

This paper examines the effect of modelling choices on the numerical simulation of premixed methane/air combustion in narrow channels. Knowledge on standard and well-accepted numerical methods in literature are collected in a cohesive document. The less well-established modelling choices have been thoroughly evaluated and discussed. A systematic method of computing the grid convergence index (GCI) has been presented for refining the computational grid. Two types of inflow boundary conditions have been tested and compared in terms of their wave-damping characteristics. The effect of different reaction schemes on simulation results have been examined and an appropriate mechanism (DRM-19) has been selected. Various types of ignition strategies to initiate the flame have been tested and compared. The transient ignition process which has not been discussed extensively in existing literature has been quantitatively described in this paper

Ghrelin as a novel locally produced relaxing peptide of the iris sphincter and dilator muscles

Ghrelin is a recently described acylated peptide, which works as a somatosecretagogue and has described effects on the smooth, skeletal and cardiac muscle. We examined the production and effects of ghrelin on relaxation of the iris muscles. Contractile effects of 1-5 human ghrelin (frGhr, 10(-9)-6 x 10(-5)M) and 1-5 human des-octanoyl-ghrelin (d-frGhr; 10(-9)-6 x 10(-5)M) were tested on iris rabbit sphincter (n=11 frGhr; n=7 d-frGhr), dilator (n=6 frGhr; n=6 d-frGhr) and rat sphincter (n=6 frGhr; n=8 d-frGhr) precontracted muscles. On rabbit sphincter the effect of frGhr was also tested in presence of: i) L-NA (10(-5)M; n=7); ii) indomethacin (10(-5)M; n=7); iii) DLys(3)GHRP6 (10(-4)M; n=6); and iv) apamin+carybdotoxin (10(-6)M; n=6). Furthermore, on rabbit dilator the effect of frGhr was tested in presence of DLys(3)GHRP6 (10(-4)M; n=7). Finally, ghrelin mRNA production was assessed by "in situ" hybridization in Wistar rat eyes (n=8). In all muscles, frGhr promoted a concentration-dependent relaxation, maximal at 6 x 10(-5)M, 1.5-3 min after its addition, decreasing tension by 34.1+/-12.1%, 25.8+/-4.8% and 52.1+/-10.3% in the rabbit sphincter, dilator and rat sphincter, respectively. In the rabbit sphincter the relaxing effects of frGhr were: (i) enhanced in presence of DLys(3)GHRP6 (118.1+/-21.1%); (ii) blunted by indomethacin; and (iii) not altered by apamin+carybdotoxin (36.4+/-14.4%) or L-NA (52.4+/-11.4%). Relaxing effects of d-frGhr in rabbit (43.3+/-5.2%) and rat (77.1+/-15.3%) sphincter muscles were similar to those of frGhr. In rabbit dilator muscle, d-frGhr did not significantly alter active tension and the relaxing effect of frGhr was blunted by GHSR-1a blockage. Ghrelin mRNA was identified in iris posterior epithelium. In conclusion, ghrelin is a novel, locally produced, relaxing agent of iris dilator and sphincter muscles, an effect that is mediated by GHSR-1a in the former, but not in the latter. Furthermore, in the sphincter it seems to be mediated by prostaglandins, but not by NO or K(Ca) channels.Portuguese Foundation for Science and Technology (nr. POCI/SAU-FCF/60803/2004) through Cardiovascular R&D Unit (FCT nr. 51/94). Authors are sincerely grateful to RS. Moura (SFRH/BPD/15408/2005), Development Unit, Health and Life Sciences Institute, School of Health Sciences, University of Minho, Braga, Portugal for her excellent contribution in the in-situ hybridization techniques

Hazard-rating scores for prioritization of accident-prone sections on highways

Various techniques are available for monitoring, improving, and assessing safety needs on the total road network. These techniques generally include procedures that look subjectively at the standards of road safety being achieved and maintained by road-controlling authorities over their total road networks. Accident reduction studies, audits of compliance with specific standards, and highway safety management strategies have been progressively developed during the past decade; although these contribute to the overall improvement of the provision of safety elements of the road network, a quantifiable technique to undertake an audit of the result has not been available. Road safety audits are concerned with the safety of all road users - motorists, pedestrians, and bicyclists - and are to be conducted for all projects, regardless of size or type. A comprehensive road safety audit was conducted on State Highway 17 in Karnataka in India, which links Bangalore and Mysore. On the basis of the road safety audit, an attempt was made to develop hazard-rating scores for a 23-km stretch of the highway. From the hazard-rating scores, a hazard ratio was also derived; it gives an indication of the safety performance of individual kilometer sections with respect to the overall average. The hazard ratio can hence be used to prioritize the sections in the stretch for improvement to enhance the overall safety of the highway

Laboratory Fatigue Studies on Bituminous Concrete Mixes Utilizing Waste Shredded Plastic Modifier

The behavior of the bituminous concrete mix containing a binder additive in the form of recycled shredded waste plastic bags was discussed. Marshall stability tests were carried out to determine the optimum bitumen content (OBC) and optimum modifier content (OMC) of the bituminous concrete mix. The fatigue life of the plastic modified bituminous concrete specimens for equal tensile strain was much higher than than that of bituminous concrete specimens tested at same temperature. It was also found that bituminous concrete mixes with plastic modifier exhibited much longer fatigue life than the conventional bituminous concrete