Flame spread in laminar mixing layers: the triple flame

In the present paper we investígate flame spread in laminar mixing layers both experimentally and numerically. First, a burner has been designed and built such that stationary triple ñames can be stabilised in a coflowing stream with well defined linear concentration gradients and well defined uniform flow velocity at the inlet to the combustión chamber. The burner itself as well as first experimental results obtained with it are presented. Second, a theoretical model is formulated for analysis of triple flames in a strained mixing laycr generated by directing a fuel stream and an oxidizer stream towards each other. Here attention is focused on the stagnation región where by means of a similarity formulation the three-dimensional flow can be described by only two spatial coordinates. To solve the governing equations for the limiting case in which a thermal-diffusional model results, a numerical solution procedure based on self-adaptive mesh refinement is developed. For the thermal-diffusional model, the structure of the triple flame and its propagation velocity are obtained by solving numerically the governing similarity equations for a wide range of strain rates

Jookin, Jiggin, Beatin Ya Feet and Gettin’ Light: African-American Footwork Traditions

This paper looks specifically at Memphis jookin, New Orleans jiggin, Washington DC’s beat ya feet and New York City’s litefeet. It explores common characteristics and regional differences in each dance, connecting them to older African and African-American dance aesthetics. Emphasizing shared cultural heritage, this paper argues that these dances form a singular body of work that is directly connected to African-American dance traditions developed during and after enslavement. In addition, it argues that these dances are important cultural institutions and act to preserve specifical African-American socio-cultural practices

Immobilized Candida antarctica Lipase Catalyzed Transesterification of Croton megalocarpus Seed Oil for Biodiesel Production

Methanolic transesterification of Croton megalocarpus seed oil to produce biodiesel was investigated using Immobilized Candida antarctica lipase as a catalyst. The reactions were optimized by varying the temperature, amount of methanol and the weight of lipase. The transesterification process yielded 98.71 % biodiesel conversion at optimal conditions of 30 % enzyme (m/m), 50 0C reaction temperature and oil to alcohol molar ratio of 1:4. Biodiesel from this process had a remarkably high acid value. All the other fuel properties measured were within the range stipulated in the American Society for Testing and Materials (ASTM) and International Standards Organization (ISO) standards.   Keywords: Biodiesel, Croton megalocarpus, Transesterification, lipas

Passiflora edulis seed oil methyl ester as a potential source of biodiesel

In recent years, there has been an increasing amount of literature on biodiesel as a feasible source of renewable energy. Compared to fossil energy, biodiesel is environmentally friendlier which makes it a viable option. This study set out with the aim of assessing the use of Passiflora edulis seed oil (purple passion fruit) obtained from an industrial fruit juice processing waste. The oil was evaluated as a good potential feedstock for production of biodiesel. In this study Passiflora edulis seed oil was transesterified using methanol and potassium hydroxide. A biodiesel yield of 80 % was obtained. The methyl ester had a viscosity of 4.60 mm2/s, acid value 0.45 mgKOH/g, density 0.89 g/ml, colour 1.60, water content 0.04 %, copper strip corrosion-No tarnish, and flash point > 150 0C. The fuel parameters measured were within range according to the American Society for Testing and Materials (ASTM) and International Standards Organization (ISO) standards. The current findings add substantially to our understanding of biodiesel and it sources. Keywords: Transesterification, Passiflora edulis seed oil, Methanol, Biodiesel, Methyl este

Premixed edge-flames under transverse enthalpy gradients

We describe flame propagation between two opposed reactive streams which may differ in their composition and temperature. A two-dimensional counterflow configuration and an irreversible Arrhenius reaction are adopted, along with the constant density approximation. Attention is focused on the influence of two nondimensional parameters. The first one, denoted by γ, represents the difference in the enthalpy of the feed streams. The second one, ε, quantifies the ratio between the characteristic chemical time and the strain time. After a general formulation of the problem, we begin by an analysis of the one-dimensional case consisting of two parallel planar flames of unequal strength. The flames behavior is described analytically and numerically. In particular, two extinction regimes are identified: for values of γ smaller than a critical value γ*, the flames extinguish by quenching against each other at the stagnation plane; for γ > γ* they extinguish while at a finite distance from each other which increases with γ. These behaviors are similar to those, known in the literature, associated with the influence of Lewis numbers on the extinction of twin-flames. We then describe the propagation of two-dimensional flame fronts along the stagnation line, in a direction perpendicular to the plane of strain. The flame front is thus curved under the combined effects of the flow field and the transverse enthalpy gradient in the frozen mixture ahead of it; far behind the state of the gas is that of the pair of flat flames introduced above. The problem is studied numerically and complemented by an analytical description of the fast-chemistry situations corresponding to small values of ε. In particular we describe, for different fixed values of γ, the evolution of ignition fronts, characterized by a positive propagation speed, to extinction fronts, characterized by negative speeds, as ε is increased. In addition to the marked change in the flame shape, the most noticeable effect of an increase in γ is the decrease in the propagation speed of the flame front. These effects are associated with the increased front curvature for higher values of γ, along with a shift of the front leading edge towards the stream with higher enthalpy

Hypothermia amongst neonatal admissions in Kenya: a retrospective cohort study assessing prevalence, trends, associated factors, and its relationship with all-cause neonatal mortality

BackgroundReports on hypothermia from high-burden countries like Kenya amongst sick newborns often include few centers or relatively small sample sizes.ObjectivesThis study endeavored to describe: (i) the burden of hypothermia on admission across 21 newborn units in Kenya, (ii) any trend in prevalence of hypothermia over time, (iii) factors associated with hypothermia at admission, and (iv) hypothermia's association with inpatient neonatal mortality.MethodsA retrospective cohort study was conducted from January 2020 to March 2023, focusing on small and sick newborns admitted in 21 NBUs. The primary and secondary outcome measures were the prevalence of hypothermia at admission and mortality during the index admission, respectively. An ordinal logistic regression model was used to estimate the relationship between selected factors and the outcomes cold stress (36.0°C–36.4°C) and hypothermia (<36.0°C). Factors associated with neonatal mortality, including hypothermia defined as body temperature below 36.0°C, were also explored using logistic regression.ResultsA total of 58,804 newborns from newborn units in 21 study hospitals were included in the analysis. Out of these, 47,999 (82%) had their admission temperature recorded and 8,391 (17.5%) had hypothermia. Hypothermia prevalence decreased over the study period while admission temperature documentation increased. Significant associations were found between low birthweight and very low (0–3) APGAR scores with hypothermia at admission. Odds of hypothermia reduced as ambient temperature and month of participation in the Clinical Information Network (a collaborative learning health platform for healthcare improvement) increased. Hypothermia at admission was associated with 35% (OR 1.35, 95% CI 1.22, 1.50) increase in odds of neonatal inpatient death.ConclusionsA substantial proportion of newborns are admitted with hypothermia, indicating a breakdown in warm chain protocols after birth and intra-hospital transport that increases odds of mortality. Urgent implementation of rigorous warm chain protocols, particularly for low-birth-weight babies, is crucial to protect these vulnerable newborns from the detrimental effects of hypothermia

Detailed structure of pipe flow with water hammer oscillations

Herein, the evolution and detailed structure of velocity and pressure fields of an oscillating axi-symmetric pipe flow arising from a rapid closure of a valve has been determined through the solution, by the Finite Volume technique, of the full Navier Stokes equations. The method correctly predicts the distortion of the pressure waveform. The two-dimensional solution obtained confirms the one-dimensional solution obtained by the Method of Characteristics of the two-equation model incorporating frequency dependent friction typically used in modelling of transient pipe flows. The velocity field following valve closure is seen to consist of the initial velocity profile upon which is superimposed an oscillating velocity component. The oscillating component is uniform in a pipe cross-section, at any instant. However, the profiles of initial steady state flow component and the uniform oscillating flow component are progressively distorted as the cumulative distance traversed by the wave increases. Journal of Agriculture, Science & Technology Vol. 9 (1) 2007: pp. 64-7