An experimental study of the dual-fuel performance of a small compression ignition diesel engine operating with three gaseous fuels

A dual-fuel engine is a compression ignition (CI) engine where the primary gaseous fuel source is premixed with air as it enters the combustion chamber. This homogenous mixture is ignited by a small quantity of diesel, the ‘pilot’, that is injected towards the end of the compression stroke. In the present study, a direct-injection CI engine, was fuelled with three different gaseous fuels: methane, propane, and butane. The engine performance at various gaseous concentrations was recorded at 1500 r/min and quarter, half, and three-quarters relative to full a load of 18.7 kW. In order to investigate the combustion performance, a novel three-zone heat release rate analysis was applied to the data. The resulting heat release rate data are used to aid understanding of the performance characteristics of the engine in dual-fuel mode. Data are presented for the heat release rates, effects of engine load and speed, brake specific energy consumption of the engine, and combustion phasing of the three different primary gaseous fuels. Methane permitted the maximum energy substitution, relative to diesel, and yielded the most significant reductions in CO2. However, propane also had significant reductions in CO2 but had an increased diffusional combustion stage which may lend itself to the modern high-speed direct-injection engine

Effect of Different Prosthetic Knees/feet on the Roll-Over Shape

Roll-over shape (ROS) of knee-ankle-foot (KAF) is a scientific method which has been used to compare performance and design of the different prosthetic foot. In the current study, however, we aimed to understand the influence of the prosthetic components (i.e. knee and foot) on the knee-ankle-foot roll-over shape in a unilateral transfemoral amputee. We performed a case study based on series of experiments with repeated measures on single amputee wearing two different commercially available microprocessor prosthetic knees, during two weeks adaptation period to understand the influence of the prosthetic knee/foot using KAF ROS as an objective measure during level ground walking. The kinematics of the center of pressure (COP), lateral knee and ankle markers were collected and processed to obtain ROS and the results were used to fit a circular shape arc to obtain radius of curvature (ROC). The results indicated that the prosthetic knees have influenced ROC outcomes. The analysis of variance (ANOVA) and post hoc test of the normalized radius of curvature showed the mean of ROC were significantly different between Rheo3 knee, Orion2 and Orion2 with Echelon foot. The amputee reflected his comfort with Rheo3 plus College park foot and Orion with Echelon foot. A conclusion is drawn that multiple comfort zones may exists based on amputee’s ROS metrics. This finding suggests that the design of prosthetic knee should not be considered as a single component but rather as part of a whole system with different comfort zones

Rotating perfect fluid sources of the NUT metric

Locally rotationally symmetric perfect fluid solutions of Einstein's gravitational equations are matched along the hypersurface of vanishing pressure with the NUT metric. These rigidly rotating fluids are interpreted as sources for the vacuum exterior which consists only of a stationary region of the Taub-NUT space-time. The solution of the matching conditions leaves generally three parameters in the global solution. Examples of perfect fluid sources are discussed.Comment: 8 pages, late

Cyberinfrastructure Software Sustainability and Reusability: Report from an NSF-funded workshop

Contributing writers: Guy Almes, Amy Apon, Geoffrey Brown, David Lifka, Andrew Lumsdaine, Marlon Pierce, Beth Plale, Ruth Pordes, Craig A. Stewart, Von Welch1, Bradley C. Wheele

General Relativistic 1+3 Orthonormal Frame Approach Revisited

The equations of the 1+3 orthonormal frame approach are explicitly presented and discussed. Natural choices of local coordinates are mentioned. A dimensionless formulation is subsequently given. It is demonstrated how one can obtain a number of interesting problems by specializing the general equations. In particular, equation systems for ``silent'' dust cosmological models also containing magnetic Maxwell fields, locally rotationally symmetric spacetime geometries and spatially homogeneous cosmological models are presented. We show that while the 3-Cotton--York tensor is zero for Szekeres dust models, it is nonzero for a generic representative within the ``silent'' class.Comment: 41 pages, uufiles encoded postscript file, submitted to Phys. Rev.

Implications of the PEGASUS-TIMI 54 Trial for US Clinical Practice

Objectives This study aims to determine the proportion of real-world patients with myocardial infarction (MI) who would have been eligible for the PEGASUS-TIMI 54 (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin-Thrombolysis in Myocardial Infarction 54) trial, to characterise their current use of P2Y12 inhibitors and to explore the estimated costs and ischaemic event consequences of increasing P2Y12 inhibitor use among these patients. Methods In the US national ACTION Registry–GWTG (Acute Coronary Treatment and Intervention Outcomes Network Registry–Get With The Guidelines), we identified 273 328 patients with MI and determined the proportion that would have met the eligibility criteria for the PEGASUS trial. We described longitudinal P2Y12 inhibitor use among patients eligible for PEGASUS and estimated the cost and ischaemic consequences of increasing P2Y12 use among eligible patients. Results A total of 112 222 (41.1%) patients with MI in ACTION Registry–GWTG met eligibility for the PEGASUS trial. Among 83 871 eligible patients with pharmacy claims data, 23 042 (27.5%) were on a P2Y12 inhibitor at 1 year, 9661 (11.5%) at 2 years and 5246 (6.3%) at 3 years, with the majority (79.2%) of these patients on clopidogrel. The use of ticagrelor in eligible patients not yet on a P2Y12 inhibitor at 1 year post-MI would cost an estimated US$885 000 per MI, stroke or cardiovascular death averted over a 3-year time horizon, while the use of clopidogrel would cost an estimated US$19 800 per ischaemic event averted. Conclusion In contemporary clinical practice, a minority of patients are on a P2Y12 inhibitor beyond 1-year post-MI. Applying PEGASUS trial findings to clinical practice would result in a large increase in P2Y12 inhibitor use, with a cost per ischaemic event averted that is strongly influenced by the choice of therapy

Principal null directions of perturbed black holes

The properties of principal null directions of a perturbed black hole are investigated. It shown that principal null directions are directly observable quantities characterizing the space-time. A definition of a perturbed space-time, generalizing that given by Stewart and Walker is proposed. This more general framework allows one to include descriptions of a given space-time other than by a pair $(M,g)$ where $M$ is a four-dimensional differential manifold and $g$ a Lorentz metric. Examples of alternative characterizations are the curvature representation of Karlhede and others, the Newman-Penrose representation or observable quantities involving principal null directions. The conditions are studied under which the various alternative choices of observables provide equivalent descriptions of the space-time.Comment: To appear in Class. Quantum Gra

The Burden of Uterine Fibroids for African-American Women: Results of a National Survey

Uterine fibroids have a disproportionate impact on African-American women. There are, however, no data to compare racial differences in symptoms, quality of life, effect on employment, and information-seeking behavior for this disease