On the Acoustical Dynamics of Bubble Clouds

Recently, Morch [1,2,3,4] Chahine [5,6] and others have focused attention on the dynamics of a cloud or cluster of cavitating bubbles and have expanded on the work of van Wijngaarden [7,8] and others. Unfortunately, there appear to be a number of inconsistencies in this recent work which will require further study before a coherent body of knowledge on the dynamics of clouds of bubbles is established. For example, Morch and his co-workers [1,2,3] have visualized the collapse of a cloud of cavitating bubbles as involving the inward propagation of a shock wave; it is assumed that the bubbles collapse virtually completely when they encounter the shock. This implies the virtual absense of non-condensable gas in the bubbles and the predominance of vapor. Yet in these circumstances the mixture in the the cloud will not have any real sonic speed. As implied by a negative L.H.S. of equation (9), the fluid motion equations for the mixture would be elliptic not hyperbolic and hence shock wave solutions are inappropriate

Socioeconomic factors that lead to Latino male students leaving school before graduating

Thesis (M.Ed.) University of Alaska Fairbanks, 2012Students of color make up a predominant number of learners that leave high school before graduating (National Center for Education Research, 2009). I selected to study Latino males to narrow the scope of my research. The literature I reviewed pointed directly at socioeconomics as one of the primary factors. I feel there are more specific factors involved for many of the individuals impacted. I used a qualitative approach and utilized an anonymous survey and individual interviews to pinpoint some of these factors. The findings from my research further supported that socioeconomics were a leading factor. My data and literature review showed that school environment and stereotyping/discrimination also played a role. I intend to conduct further research to identify the additional sub-factors that are most prevalent to Latino males. My long-term goal is to provide information to my peers that can assist in the construction or reconstruction of programs that can offer the best support for these students

Sensitivity of regional monsoons to idealised equatorial volcanic eruption of different sulfur emission strengths

The impact of volcanic forcing on tropical precipitation is investigated in a new set of sensitivity experiments within the Max Planck Institute Grand Ensemble framework. Five ensembles are created, each containing 100 realizations for an idealized "Pinatubo-like" equatorial volcanic eruption with emissions covering a range of 2.5 - 40 Tg sulfur (S). The ensembles provide an excellent database to disentangle the influence of volcanic forcing on monsoons and tropical hydroclimate over the wide spectrum of the climate's internal variability. Monsoons are generally weaker for two years after volcanic eruptions and their weakening is a function of emissions. However, only a stronger than Pinatubo-like eruption ($\geq$ 10 Tg S) leads to significant and substantial monsoon changes, and some regions (such as North and South Africa, South America and South Asia) are much more sensitive to this kind of forcing than the others. The decreased monsoon precipitation is strongly tied to the weakening of the regional tropical overturning. The reduced atmospheric net energy input and increased gross moist stability at the Hadley circulation updraft due to the equatorial volcanic eruption, require a slowdown of the circulation as a consequence of less moist static energy exported away from the ITC

Forecasting constraints on deviations from general relativity in f(Q)f(Q) gravity with standard sirens

In this work, we explore how modified gravity theories based on the non-metricity scalar, known as $f(Q)$ gravity, affect the propagation of gravitational waves from inspiraling of binary systems. We discuss forecast constraints on $f(Q)$ gravity by considering standard siren events in two contexts: i) simulated sources of gravitational waves as black hole - neutron star binary systems, emitting in the frequency band of the third-generation detector represented by the Einstein Telescope (ET); ii) three standard siren mock catalogs based on the merger of massive black hole binaries that are expected to be observed in the operating frequency band of the Laser Interferometer Space Antenna (LISA). We find that, within the ET sensitivity, in combination with supernova and cosmic chronometer data, it will be possible to test deviations from general relativity at $<3\%$ accuracy in the redshift range $0<z<5$, while the main free parameter of the theory is globally constrained at 1.6\% accuracy within the same range. In light of LISA's forecasts, combined with supernova and cosmic chronometer data, in the best scenario, we find that the main free parameter of the theory will be constrained at 1.6\% accuracy up to high redshifts. Therefore, we conclude that future gravitational wave observations by ET and LISA will provide a unique way to test, with good accuracy, the nature of gravity up to very large cosmic distances.Comment: 12 pages, 5 figures. Accepted for publication in Physical Review

A local composition model for the prediction of mutual diffusion coefficients in binary liquid mixtures from tracer diffusion coefficients

In a recent publication (Moggride, 2012a), a simple equation was shown to accurately predict the mutual diffusion coefficients for a wide range of non-ideal binary mixtures from the tracer diffusion coefficients and thermodynamic correction factor, on the physical basis that the dynamic concentration fluctuations in the liquid mixture result in a reduction of the mean thermodynamic correction factor relative to the hypothetical case in which such fluctuations do not occur. The analysis was extended to cases where strong molecular association was hypothesised to occur in the form of dimerization of a polar species in mixtures with a non-polar one. This required modification of the average molecular mobility in the form of doubling the tracer diffusivity of the dimerized species (Moggridge, 2012b). Predictions were found to show good accuracy for the mixtures investigated. One of the difficulties with this approach is that it is an a posteriori correction: there is no a priori way of knowing whether strong cluster formation influences the observed molecular mobility, or what the appropriate size of the cluster is. In this work, a modification is made to the average molecular mobility in the original equation by replacing the bulk mole fraction with local mole fraction calculated using the NRTL (non-random two liquid) model, to take account of strong molecular association that results in highly correlated movement during diffusion. The new equation enables an accurate description of mutual diffusion coefficients in mixtures of one strongly self-associating species and one non-polar species, as well as in non-ideal, non-associating mixtures. This result is significant because in this way there is no need of any prior knowledge on the degree of molecular association in the mixture for the prediction of mutual diffusion coefficients from tracer diffusivities.Carmine D’Agostino would like to acknowledge Wolfson College, University of Cambridge, for supporting his research activities.This is the accepted manuscript. The final version is available at http://www.sciencedirect.com/science/article/pii/S0009250915002821

Palmitoylethanolamide is a disease-modifying agent in peripheral neuropathy : pain relief and neuroprotection share a PPAR-alpha-mediated mechanism

Peer reviewedPublisher PD

Adsorption of pyridine from aqueous solutions by polymeric adsorbents MN 200 and MN 500. Part 2: Kinetics and diffusion analysis

The adsorption kinetics of pyridine adsorption on Macronet adsorbents MN 200 and MN 500 from aqueous solution was investigated at various initial pyridine concentrations and temperatures. The Weber-Morris plots revealed the influence of both external film diffusion and intraparticle diffusion resistances. The two linear regions in Weber-Morris plots were attributed to macropore and micropore diffusion, respectively, which was associated to the bimodal pore size distribution of the adsorbents. New insights into the diffusion mechanisms were highlighted, with the proposed internal film diffusion resistance dominating into the macropore region, whereas homogeneous particle diffusion resistance describes diffusion in the micropore region. The importance of pore and surface diffusion in the micropores was noted in contributing to the observed diffusion kinetics. The pore diffusion coefficient was estimated from PFG (pulsed-field gradient) parameter and molecular diffusion coefficient of pyridine in bulk liquid. A greater contribution of the surface diffusion to the overall diffusion kinetics was found for MN 500 as inferred from a proposed calculation method, which agrees with its better adsorption performance. The overall findings highlight the effect of pore structure onto the diffusion mechanisms inside the pores and help to gain a better understanding into the adsorption kinetics of these Macronet adsorbents which are promising materials for the removal of N-heterocyclic compounds from waste water.Wolfson College, CambridgeThis is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.cej.2016.07.08

Assessment of the Propulsive Performance of Fuel Vapor Pressurized Hydrogen Peroxide-Ethane Rocket Engines

In the last years low-toxicity “green” storable liquid propellants have become considerably more attractive as possible substitutes for nitrogen oxides and hydrazines. The main advantage of “green” propellants is represented by the significant cost savings associated with the drastic simplification of the health and safety protection procedures necessary during propellant production, storage and handling. Fuel Vapor Pressurization (FVP) technology of “green” bipropellant rocket engines potentially offers very significant additional advantages in terms of system cost, complexity, reliability, safety and mass, with practically no penalty in propulsive performance compared to traditional storable propellants such as mixed nitrogen oxides and hydrazines. Pioneering FVP experiments were carried out by Goddard, Wyld and others. Detailed studies have been conducted and several tests have been successfully performed since 1994 in the US, but no such experience is presently available in Europe, nor FVP has ever attained flight readiness anywhere in the world. The main characteristics of the FVP system examined in this work consist in the use of storable, non-toxic, inexpensive, non hypergolic, high-energy propellants such as hydrogen peroxide (HP, H2O2) and ethane (C2H6) and in the storage of these propellants in a single lightweight tank, using a flexible diaphragm or a bladder to separate the fuel from the oxidizer and a catalytic reactor to decompose the hydrogen peroxide before mixing and combustion with ethane. This configuration therefore yields a very simple and yet highly efficient and reliable propulsion system by eliminating the cost, the weight and complexity of propellant tanks and pressurization bottles, pressure and flow regulators and ignition systems. These advantages are of special relevance in low- or mediumthrust rocket engines for the rapidly expanding market of “small” space missions and led the authors to focus on the analysis and assessment of propulsion systems operating according to this concept. The present paper reports therefore the preliminary evaluation of fuel vapor pressurized H2O2-C2H6 rocket propulsion systems. The results of the analysis confirm that the development of FVP technology may represent a significant contribution to the containment of the propulsion cost of small- and medium-size spacecrafts

A Simplified Analytical Model for Evaluating the Noncavitating Performance of Axial Inducers

The present paper describes an analytical model for the preliminary prediction of the noncavitating flow field and performance of helical inducers. The proposed model is based on the traditional troughflow theory approximations with empirical corrections for outlet flow deviation and hydraulic losses due to inlet incidence effects and friction in the blade channels. Unlike most classical models, it allows – even if under still rather restrictive assumptions – for the prediction of the radial and circumferential flow velocity fields at the inducer exit section and for the approximate evaluation of the head coefficient as a function of the flow coefficient in terms of the static pressure rise generated by the inducer. The results are presented of the model validation by comparison with the experimental data obtained for several inducers tested in different facilities worldwide

BIM-ORIENTED ALGORITHMIC RECONSTRUCTION OF BUILDING COMPONENTS FOR EXISTING HERITAGE

Abstract. This study is part of a more complex research aimed at establishing guidelines to simplify the digitalization process used to manage existing building heritage. Working in a BIM environment, this paper will present two different algorithms: a modelling algorithm, a data analysis algorithm, and relative applications in the digitalization of a contemporary building. All the archival data required for the digitalization process was collected and those in two-dimensional digital vector format have aroused particular interest because they enabled initiation of the reconstruction process of the BIM model. One of the two algorithms allowed us to identify recurrent elements in a CAD drawing, based on geometric 2D primitives. The final outcome of the first phase involves quadrilateral or circular surfaces and can be viewed in algorithmic environment. The next phase involves applying a unique coloured sign to the identified sections and then export them all in a BIM software. This tool produced unexpected positive results: the presence of a small coloured grid emphasized the discrepancies created between the two-dimensional drawings and the vertical elements. We were thus able to identify the objects with these inconsistencies: they were verified using accurate surveys and then corrected.</p