574 research outputs found
Turbine blade tip heat transfer in low speed and high speed flows
No full textIn this paper, high and low speed tip flows are investigated for a high-pressure turbine blade. Previous experimental data are used to validate a CFD code, which is then used to study the tip heat transfer in high and low speed cascades. The results show that at engine representative Mach numbers the tip flow is predominantly transonic. Thus, compared to the low speed tip flow, the heat transfer is affected by reductions in both the heat transfer coefficient and the recovery temperature. The high Mach numbers in the tip region (M>1.5) lead to large local variations in recovery temperature. Significant changes in the heat transfer coefficient are also observed. These are due to changes in the structure of the tip flow at high speed. At high speeds, the pressure side corner separation bubble reattachment occurs through supersonic acceleration which halves the length of the bubble when the tip gap exit Mach number is increased from 0.1 to 1.0. In addition, shock/boundary-layer interactions within the tip gap lead to large changes in the tip boundary-layer thickness. These effects give rise to significant differences in the heat-transfer coefficient within the tip region compared to the low-speed tip flow. Compared to the low speed tip flow, the high speed tip flow is much less dominated by turbulent dissipation and is thus less sensitive to the choice of turbulence model. These results clearly demonstrate that blade tip heat transfer is a strong function of Mach number, an important implication when considering the use of low speed experimental testing and associated CFD validation in engine blade tip desig
Turbine blade tip heat transfer in low speed and high speed flows
No full textIn this paper, high and low speed tip flows are investigated for a high-pressure turbine blade. Previous experimental data are used to validate a computational fluid dynamics (CFD) code, which is then used to study the tip heat transfer in high and low speed cascades. The results show that at engine representative Mach numbers, the tip flow is predominantly transonic. Thus, compared with the low speed tip flow, the heat transfer is affected by reductions in both the heat-transfer coefficient and the recovery temperature. The high Mach numbers in the tip region (M>1.5) lead to large local variations in recovery temperature. Significant changes in the heat-transfer coefficient are also observed. These are due to changes in the structure of the tip flow at high speed. At high speeds, the pressure side corner separation bubble reattachment occurs through supersonic acceleration, which halves the length of the bubble when the tip-gap exit Mach number is increased from 0.1 to 1.0. In addition, shock/boundary-layer interactions within the tip gap lead to large changes in the tip boundary-layer thickness. These effects give rise to significant differences in the heat-transfer coefficient within the tip region compared with the low speed tip flow. Compared with the low speed tip flow, the high speed tip flow is much less dominated by turbulent dissipation and is thus less sensitive to the choice of turbulence model. These results clearly demonstrate that blade tip heat transfer is a strong function of Mach number, an important implication when considering the use of low speed experimental testing and associated CFD validation in engine blade tip design
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Rapid bacterial evaluation beyond the colony forming unit in osteomyelitis
No full textVersion of Record published 24 June 2024Examination of bacteria/host cell interactions is important for understanding the aetiology of many infectious diseases. The colony forming unit (CFU) has been the standard for quantifying bacterial burden for the past century, however, this suffers from low sensitivity and is dependent on bacterial culturability in vitro. Our data demonstrate the discrepancy between the CFU and bacterial genome copy number in an osteomyelitis-relevant co-culture system and we confirm diagnosis and quantify bacterial load in clinical bone specimens. This study provides an improved workflow for the quantification of bacterial burden in such cases.Qi Sun, Kimberley Huynh, Dzenita Muratovic, Nicholas J Gunn, Anja R Zelmer, Lucian Bogdan Solomon, Gerald J Atkins, Dongqing Yan
nicholasdavies/amr-competition-diversity: Full release for publication
No full textCode for model fitting associated with: Davies, N. G., Flasche, S., Jit, M., and Atkins, K. E. 2020. Competition and diversity determine vaccine impact on antibiotic resistance evolution. Requires a C++ compiler (tested with g++ 9) with OpenMP support, and the libraries lua, gsl, gslcblas, and nlopt. The v1.1. release contains both C++ and R source code associated with publication
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
Near-Bed Cohesive Sediment Processes: Development of a Self-Contained System for Long-Term Field Measurements
No full textThis report describes the development of a self-contained system for making long-term field measurements of bed elevation changes and the associated near-bed hydrodynamics and cohesive sedimentary parameters in estuarine environments. These measurements are required to ensure the understanding of these parameters and their interaction with bed elevation changes. In particular, more information is sought on the relative contributions of each tide in a spring-neap cycle and on the effect of waves. This knowledge is necessary to refine and verify the algorithms used in numerical models of the erosion and deposition processes. This should lead to improved confidence in these models, in particular when .making long-term predictions of bed elevation changes. The measurement system will be capable of unattended deployment for a complete spring-neap cycle (15 days) and measures the following: (1) Turbulent velocities in 3 orthogonal directions close to the bed. (2) Turbidity levels at 3 heights in the bottom 1m of the water column. (3) Water depths. (4) Wave characteristics. (5) Bed elevation changes. The system has integral signal conditioning, data logging facilities and power supplies. The basic calibrations of all the instruments in the measurement system have been established during laboratory tests. The instruments included in the measurement system have been selected not only on the grounds of the nature and range of the data required but also to minimise the system's power consumption. The choice of annular electromagnetic current meters ensures the system is suitable for use in wave or current only conditions or combined waves and currents. All the underwater components of the system have been pressure tested to a depth equivalent to approximately 10m of water column. A suite of data analysis computer programs has been developed to process the data collected by the measurement system efficiently
Turbulence measurements using a small electromagnetic current meter in open channel flows
No full textThe use of a small two-component electromagnetic current meter to record turbulent velocities in a laboratory flume is described. The results from these experiments are compared with results obtained previously using different measuring techniques
Validation of HR-pQCT against micro-CT for morphometric and biomechanical analyses: A review
No full textISSN:2352-187
Showing the essential science structure of a scientific domain and its evolution
No full textCategory cocitation and its representation through social networks is proving to be a very adequate technique for the visualization and
analysis of great scientific domains. Its combination with pathfinder networks using pruning values r=∞and q=n−1 makes manifest the essence of research in the domain represented, or what we might call the `most salient structure'. The possible loss of structural information, caused by aggressive pruning in peripheral areas of the networks, is overcome by creating heliocentric maps for each category. The depictions obtained with this procedure become tools of great usefulness in view of their capacity to reveal the evolution of a given scientific domain over time, to show differences and similarities between different domains, and to suggest possible new lines for development. This article presents the scientogram of the United States for the year 2002, identifying its essential structure. We also show the scientograms of China for the years 1990 and 2002, in order to study its particular national evolution.
Finally, we try to detect patterns and tendencies in the three scientograms that would allow one to predict or flag the evolution of a scientific domain
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