Experimental analysis of crankcase oil aerosol generation and control

Crankcase ventilation contributes significantly to diesel engine particulate emissions. Future regulations will not only limit the mass of particulate matter, but also the number of particles. Controlling the source of crankcase emissions is critical to meeting the perennial legislation. Deficiency in the understanding of crankcase emissions generation and the contribution of lubricating oil has been addressed in detail by the experimental study presented in this thesis. A plethora of high speed laser optical diagnostics techniques have been employed to deduce the main mechanisms of crankcase oil aerosol generation. Novel images have captured oil atomisation and passive oil distribution around the crankcase of an optically accessed, motored, four cylinder, off highway, heavy duty, diesel engine. Rayleigh type ligament breakup of oil films present on the surface of dynamic components, most notably the crankshaft, camshaft and valve rockers generated oil drops below 10 micrometers. Data illustrated not only crankcase oil aerosol generation at source, but it has provided valuable information on methods to control oil aerosol generation and improve oil circuit efficiency. The feasibility of utilising computational fluid dynamics to predict crankcase oil aerosol generation has been successfully assessed using the experimental data. Particle sampling has characterised the crankcase emissions from both a fired and motored diesel engine crankcase. The evolution of submicron crankcase particles down to 5 nm has been recorded from both engines, including the isolated contribution of engine oil, at a wide range of engine test points. Results have provided constructive insight into the generation and control of this complex emission. The main mechanism of crankcase oil aerosol generation was found to be crankshaft oil atomisation. This atomisation process has been analysed in detail, involving high speed imaging of primary and satellite drop generation and high speed digital particle image velocity of the crankshaft air flow. A promising mechanism of regulating and controlling crankcase oil aerosol emissions at source has been studied experimentally

Centre-of-mass and internal symmetries in classical relativistic systems

The internal symmetry of composite relativistic systems is discussed. It is demonstrated that Lorentz-Poincar\'e symmetry implies the existence of internal moments associated with the Lorentz boost, which are Laplace-Runge-Lenz (LRL) vectors. The LRL symmetry is thus found to be the internal symmetry universally associated with the global Lorentz transformations, in much the same way as internal spatial rotations are associated with global spatial rotations. Two applications are included, for an interacting 2-body system and for an interaction-free many-body system of particles. The issue of localizability of the relativistic CM coordinate is also discussed

A Cost-based Optimizer for Gradient Descent Optimization

As the use of machine learning (ML) permeates into diverse application domains, there is an urgent need to support a declarative framework for ML. Ideally, a user will specify an ML task in a high-level and easy-to-use language and the framework will invoke the appropriate algorithms and system configurations to execute it. An important observation towards designing such a framework is that many ML tasks can be expressed as mathematical optimization problems, which take a specific form. Furthermore, these optimization problems can be efficiently solved using variations of the gradient descent (GD) algorithm. Thus, to decouple a user specification of an ML task from its execution, a key component is a GD optimizer. We propose a cost-based GD optimizer that selects the best GD plan for a given ML task. To build our optimizer, we introduce a set of abstract operators for expressing GD algorithms and propose a novel approach to estimate the number of iterations a GD algorithm requires to converge. Extensive experiments on real and synthetic datasets show that our optimizer not only chooses the best GD plan but also allows for optimizations that achieve orders of magnitude performance speed-up.Comment: Accepted at SIGMOD 201

Hazard Assessment of Personal Protective Clothing for Hydrogen Peroxide Service

Selection of personal protective equipment (PPE) for hydrogen peroxide service is an important part of the hazard assessment process. But because drip testing of chemical protective clothing for hydrogen peroxide service has not been reported for about 40 years, it is of great interest to test new protective clothing materials with new, high-concentration hydrogen peroxide following similar procedures. The suitability of PPE for hydrogen peroxide service is in part determined by observations made when hydrogen peroxide is dripped onto swatches of protective clothing material. Protective clothing material was tested as received, in soiled condition, and in grossly soiled condition. Materials were soiled by pretreating the material with potassium permanganate (KMnO4) solution then drying to promote a reaction. Materials were grossly soiled with solid KMnO4 to greatly promote reaction. Observations of results including visual changes to the hydrogen peroxide and materials, times to ignition, and self-extinguishing characteristics of the materials are reported

The Effect of Music Familiarity on Students’ Reading Comprehension Performance

The current study examined 85 university students’ performance in a reading comprehension task under three conditions: silence, familiar, or unfamiliar music. The results indicated that the students in the familiar music condition performed significantly worse than those in the silent conditions, as well as those in the unfamiliar music condition

Removal of Perfluorinated Grease Components from NTO Oxidizer

Perfluorinated greases are typically used as a thread lubricant in the assembly of non-welded nitrogen tetroxide (NTO) oxidizer systems. These greases, typically a perfluoroalkylether, with suspended polytetrafluoroethylene (PTFE) micro-powder, have attractive lubricating properties toward threaded components and are relatively chemically inert toward NTO oxidizers. A major drawback, however, is that perfluoroalkylether greases are soluble or dispersible in NTO oxidizers and can contaminate the propellant. The result is propellant that fails the non-volatile residue (NVR) specification analyses and that may have negative effects on test hardware performance and lifetime. Consequently, removal of the grease contaminants from NTO may be highly desirable. Methods for the removal of perfluorinated grease components from NTO oxidizers including distillation, adsorption, filtration, and adjustment of temperature are investigated and reported in this work. Solubility or dispersibility data for the perfluoroalkylether oil (Krytox(tm)143 AC) component of a perfluorinated grease (Krytox 240 AC) and for Krytox 240 AC in NTO were determined and are reported

Parameterized Model-Checking for Timed-Systems with Conjunctive Guards (Extended Version)

In this work we extend the Emerson and Kahlon's cutoff theorems for process skeletons with conjunctive guards to Parameterized Networks of Timed Automata, i.e. systems obtained by an \emph{apriori} unknown number of Timed Automata instantiated from a finite set $U_1, \dots, U_n$ of Timed Automata templates. In this way we aim at giving a tool to universally verify software systems where an unknown number of software components (i.e. processes) interact with continuous time temporal constraints. It is often the case, indeed, that distributed algorithms show an heterogeneous nature, combining dynamic aspects with real-time aspects. In the paper we will also show how to model check a protocol that uses special variables storing identifiers of the participating processes (i.e. PIDs) in Timed Automata with conjunctive guards. This is non-trivial, since solutions to the parameterized verification problem often relies on the processes to be symmetric, i.e. indistinguishable. On the other side, many popular distributed algorithms make use of PIDs and thus cannot directly apply those solutions

Calibrated cycles and T-duality

For Hitchin's generalised geometries we introduce and analyse the concept of a structured submanifold which encapsulates the classical notion of a calibrated submanifold. Under a suitable integrability condition on the ambient geometry, these generalised calibrated cycles minimise a functional occurring as D-brane energy in type II string theories, involving both so-called NS-NS- and R-R-fields. Further, we investigate the behaviour of calibrated cycles under T-duality and construct non-trivial examples.Comment: 43 pages. v4: formalism and T-duality part considerably expande