Collagen metabolism in normal heart and during cardiac hypertrophy

Imperial Users onl

Droplet size and morphology characterization for diesel sprays under atmospheric operating conditions

The shape of microscopic fuel droplets may differ from the perfect sphere, affecting their external surface area and thus the heat transfer with the surrounding gas. Hence there is a need for the characterization of droplet shapes, and the estimation of external surface area, in order to enable the development of physically accurate mathematical models for the heating and evaporation of diesel fuel sprays. We present ongoing work to automat-ically identify and reconstruct the morphology of fuel droplets, primarily focusing in this study on irregularly-shaped, partially-deformed and oscillating droplets under atmospheric conditions. We used direct imaging tech-niques based on long-working distance microscopy and ultra-high-speed video to conduct a detailed temporal investigation of droplet morphology. We applied purpose-built algorithms to extract droplet size, velocity, vol-ume and external surface area from the microscopic ultra-high-speed video frames. High resolution images of oscillating droplets and a formation of a droplet form ligament, sphericity factors, volume as well as external surface area are presented for 500 bar injection pressure in the near nozzle region (up to 0.7 mm from nozzle exit) under atmospheric conditions. We observed a range of different liquid structures, including perfectly spher-ical, non-spherical droplets and stretched ligaments. We found that large droplets and ligaments exceeding the size of the nozzle hole could be found at the end of injection. In order to estimate droplet volume and external surface area from two-dimensional droplet information, a discrete revolution of the droplet silhouette about its major centroidal axis was used. Special attention was paid to the estimation of actual errors in the prediction of volume and surface characteristics from a droplet silhouette. In addition to the estimation of droplet volume and external surface area, the actual shape reconstruction in 3D coordinates from a droplet silhouette was performed in order to enable future numerical modelling studies of real droplets

The effect of operating conditions on post-injection fuel discharge in an optical engine

After the end of injection, the needle closes and residual fuel present inside the injector sac and orifices is discharged due to the high fluid inertia. This so-called post-injection fuel discharge can present several problems. The excess fuel can undergo incomplete combustion due to its large, slow moving and often surface-bound nature. Not only does this have a negative effect on emissions and performance, but it has been speculated that the by-products of incomplete combustion are implicated in the growth of carbonaceous deposits on the tips of fuel injectors. Accumulation of these deposits is known to lead to premature fuel injector failure that can lead to re-ductions in power output and engine lifetime. Seeing as modern multiple-injection strategies give rise to an in-creased number of transient injection phases, post-injection discharges are an increasingly common occurrence during normal operating conditions. In order to develop a phenomenological model for the fluid dynamics after the end of injection, there is a need to characterise the causes of this discharge and how they might be influenced by engine operating conditions. In this study we present ongoing analysis into results from the first visualisation of post injection fuel discharge at the microscopic level under engine-like operating conditions. We observed the process of fuel discharge for multi-hole injectors, using a high-speed camera fitted with a long-distance micro-scope and a high-speed laser illumination source. We related the effect of a variety of operating conditions on the severity of this process, including injection pressure and in-cylinder pressure along with a characterisation of the dynamics of the various modes by which these undesired liquid structures are produced. We present the different modes by which this process occurs and we conclude that the extent of post-injection discharge depends on both the in-cylinder and injection pressures

Incorporating the mature students voice and lived experiences into continuous quality improvement

Improving academic quality requires feedback from students since they have specific insight in their lived educational experience. Most institutions assess educational experience by evaluating individual modules. Few institutions collectively review evaluation data from multiple modules or explore this data for evidence of curriculum transformation. The University of Pretoria developed four curriculum transformation drivers and the School of Health Systems and Public Health developed and implemented 19 transformation-related statements. We revised the standard end-of-module evaluations to explore student experiences regarding the implementation of these drivers. 45 modules were reviewed. The quantitative data were analysed in Excel. Qualitative data were analysed using an inductive approach with open-coding. We generated categories and themes before comparing these to the curriculum transformation drivers. Four major themes emerged from the qualitative data: reflecting the ‘what’, ‘why’, ‘when’, ‘where’, ‘how’ and ‘who’ of the student experience. Categories and subcategories were explored and linked to the quantitative results. The results show that the students valued their educational experience and felt valued as students. The students’ voices provided a rich source of data regarding curriculum transformation and included detailed suggestions for quality improvement. Our study presents substantive evidence of authentic educational and philosophical intentions that were realised in practice

A Variable Metric Variant of the Karmarkar Algorithm for Linear Programming

The most time-consuming part of the Karmarkar algorithm for linear programming is the projection of a vector onto the nullspace of a matrix that changes at each iteration. We present a variant of the Karmarkar algorithm that uses standard variable-metric techniques in an innovative way to approximate this projection. In limited tests, this modification greatly reduces the number of matrix factorizations needed for the solution of linear programming problems

Concepts for a multi-criteria sustainability assessment of a new more biobased economy in rural production landscapes

This study presents a new approach to model the biophysical potentials for increased biomass harvest in Denmark, and a multi-criteria sustainability assessment of the socio-economic and environmental effects of different scenarios for such increased production and new biobased economy in rural landscapes. Thereby the results serve as input to the ongoing productivism – post-productivism debate related to rural spaces in Europe. Empirical results from a case study of large scale conversion to biorefenery technologies, aiming to increase the total Danish harvest of biomass by 10 million tonnes via the conversion to new types of crop production and land management, is used as an example, and will be related to the common conceptual model presented by the workshop convenors, and a so called “Traffic-light” multi-criteria sustainability assessment scheme introduced and exemplified in the present paper. The aim is to contextualize how the problems in relation to the concrete scenario results can be considered with the landscape as the meeting basis, and used as input for a discussion of innovative models for future farming systems, landscape research and management

Family size attitudes : a comparison of measures

Photocop

Axion-photon Couplings in Invisible Axion Models

We reexamine the axion-photon couplings in various invisible axion models motivated by the recent proposal of using optical interferometry at the ASST facility in the SSCL to search for axion. We illustrate that the assignment of $U(1)_{PQ}$ charges for the fermion fields plays an important role in determining the couplings. Several simple non-minimal invisible axion models with suppressed and enhanced axion-photon couplings are constructed, respectively. We also discuss the implications of possible new experiments to detect solar axions by conversion to $X$-rays in a static magnetic apparatus tracking the sun.Comment: 14 pages, LaTeX fil

Cosmological implications of a light dilaton

Supersymmetric Peccei-Quinn symmetry and string theory predict a complex scalar field comprising a dilaton and an axion. These fields are massless at high energies, but it is known since long that the axion is stabilized in an instanton dominated vacuum. Instantons and axions together also provide a mechanism to stabilize a dilaton, thus accounting for a dilaton as a possible cold dark matter component accompanying the axion. We briefly review the prospects of this scenario and point out further implications.Comment: LaTeX, 9 pages incl. 1 figure, reference adde

Improving silage quality

Results at Kansas State University from over 200 laboratory-scale trials and 28 farm-scale trials showed that bacterial inoculants consistently improved preservation efficiency and nutritive value of the ensiled material. In contrast, anhydrous ammonia or urea decreased dry matter recovery and production per ton of crop ensiled. Economic analysis also favored the use of bacterial inoculants over nonprotein nitrogen additives. Research conducted using corn, sorghum, and alfalfa silages showed that sealing the exposed surface dramatically reduced top spoilage losses in bunker, trench, or stack silos