1,782 research outputs found
The Simulation of Recovery Procedures from Engine Failures during Helicopter Offshore Operations. Internal report no. 9331
This report discusses the mathematical models and the specialised simulation
techniques developed for an investigation of helicopter offshore operations under
adverse conditions. The development of a mathematical model of a torque limited,
twin engine power plant capable of accommodating multiple or single gas turbine
failures is presented. In order to simulate engine failures during the critical phases of
takeoff or landing manoeuvres, a novel hybrid simulation technique called HIFIS
which incorporates both inverse and forward methods has been developed. Its
formulation and the subsequent specialised recovery trajectories that it requires are
detailed
Helicopter Takeoff and Landing Procedures in Adverse Conditions using Inverse Simulation. Progress note: Oct. 92 - Sept. 93. Internal report no. 9332
This report summarises the progress made in the second year of a study of helicopter offshore
operations in adverse conditions. Initially, a narrative description of key helicopter heli-deck
related manoeuvres in the presence and absence of engine failures, is given. Based on this
information, mathematical models of the manoeuvres are developed in a form suitable for use
as input to inverse simulation. The demands of simulating pilot strategies in the event of
engine failures has necessitated the development of a multistage inverse-forward-inverse
simulation technique of novel kind and a comprehensive description of this method is
presented. A dynamic graphics package has been created to demonstrate piloting strategies
and its formulation is briefly outlined. The piloting strategies as derived from simulation
studies are presented for the Towering Takeoff and Normal Approach and Landing
manoeuvres (with and without engine failures) and these are qualitatively validated against
descriptions provided by practicing pilots. Finally, some conclusions are drawn and
directions for future work highlighted
Local and non-local approaches to fatigue crack initiation and propogation
Copyright @ 2003 Kulwer Academic Publishers.A functional form of local strength conditions under fatigue loading is introduced and employed to formulation and analysis of fatigue crack initiation and propagation. For the strength conditions associated with the Palmgren-Miner linear damage accumulation rule and the power-type S-N diagram, the problem is reduced to a non-linear integral Volterra equation, which can be transformed to a linear one for the case of a single crack. An analytical solution of some simple problems are presented for the latter case and shortcomings of the local approach are pointed out. A non-local approach free from the shortcomings is presented along with an example of its implementation.This work was completed under the research grant GR/M24592 "Non-local approach to
high cyclic fatigue: Theoretical basis" of the Engineering and Physical Sciences Research Council, UK
Aggregation of Staphylococcus aureus following treatment with the antibacterial flavonol galangin.
Aim: The flavonol galangin, an antimicrobial constituent of the traditional medicines propolis and Helichrysum aureonitens, is being assessed as part of an ongoing investigation into the antibacterial activity of flavonoids. The present study sought to establish whether galangin has any aggregatory effect on bacterial cells. Methods and Results: In preparatory time-kill assays, 50 μg ml-1 of galangin was found to reduce colony counts of c. 5 × 107 CFU ml-1Staphylococcus aureus NCTC 6571 by approximately 15 000-fold during 60 min of incubation. Subsequent light microscopy studies demonstrated significant increases in the number of large clusters of bacterial cells in populations treated with the flavonol. Conclusion: Data presented here show that galangin causes aggregation of bacterial cells. Significance and Impact of the Study: The finding that galangin causes bacterial cells to clump together may implicate the cytoplasmic membrane as a target site for this compound's activity. More importantly, this observation indicates that decreases in CFU numbers detected in time-kill and minimum bactericidal concentration (MBC) assays in previous investigations were at least partially attributable to this aggregatory effect. This raises the possibility that galangin is not genuinely bactericidal in action, and calls into question the suitability of time-kill and MBC assays for determining the nature of activity of naturally occurring flavonoids
Magnetic field induced effects in the high source-drain bias current of weakly coupled vertical quantum dot molecules
We report on the basic properties of recently observed magnetic field
resonance, induced time dependent oscillation, and hysteresis effects in the
current flowing through two weakly coupled vertical quantum dots at high
source-drain bias (up to a few tens of mV). These effects bare some similarity
to those reported in the N=2 spin-blockade regime, usually for weak in-plane
magnetic field, of quantum dot molecules and attributed to hyperfine coupling,
except here the measurements are conducted outside of the spin-blockade regime
and the out-of-plane magnetic field is up to ~6 T.Comment: 3 pages, 3 figures, accepted for publication in Physica E in EP2DS 17
conference proceeding
The forgotten '45 : Donald Dubh's rebellion in an archipelagic context
The final rebellion of Donald Dubh, heir to the forfeited MacDonald lordship of the Isles, is usually examined within the context of Highland rebellions that occurred in the half century after forfeiture. However, the factors that motivated the Islesmen to rise in rebellion in 1545 are multi-faceted and can only be fully understood by placing the rising in a wider context, which considers national and archipelagic events. The discussion that follows explores the reasons why the Islesmen, almost unanimously, entered into agreement with Henry VIII to attack Scotland from the west and why this endeavour failed. At the same time, the article highlights Henry’s recognition of the strategic importance of the west which led him into alliance with Donald Dubh and his supporters
Liver fat in adults with GH deficiency: comparison to matched controls and the effect of GH replacement
CONTEXT:
Existing data regarding the association between growth hormone deficiency (GHD) and liver fat content are conflicting.
OBJECTIVE:
We aimed i) to assess intrahepatocellular lipid (IHCL) content in hypopituitary adults with GHD compared to matched controls and ii) to evaluate the effect of growth hormone (GH) replacement on IHCL content.
DESIGN:
Cross-sectional comparison and controlled intervention study.
PATIENTS, PARTICIPANTS:
Cross-sectional comparison: 22 hypopituitary adults with GHD and 44 healthy controls matched for age, BMI, gender and ethnicity. Intervention study: 9 GHD patients starting GH replacement (GH Rx group), 9 GHD patients not starting replacement therapy (non-GH Rx group).
INTERVENTION:
Intervention study:GH replacement for 6 months in the GH Rx group, dosage was titrated to achieve normal IGF-1 levels.
MAIN OUTCOME MEASURES:
IHCL content determined by proton magnetic resonance spectroscopy (1 H MRS).
RESULTS:
Cross-sectional comparison: There was no difference in IHCL content between GHD patients and healthy controls (1.89% (0.30, 4.03) vs. 1.14% (0.22, 2.32); p=0.2), the prevalence of patients with hepatic steatosis (IHCL of ≥ 5.56%) was similar in the two groups (22.7% vs. 15.9%; chi square probability = 0.4). Intervention study: The change in IHCL content over 6 months did not differ between the GH Rx group and the non-GH Rx group (-0.63 ± 4.53% vs. +0.11 ± 1.46%; p=0.6).
CONCLUSIONS:
In our study liver fat content and the prevalence of hepatic steatosis did not differ between hypopituitary adults with GHD and matched controls. In GHD patients GH replacement had no effect on liver fat content
Heat and the planning system: how can local authorities encourage deployment of low and zero-carbon heating?
There is widespread recognition of the need for new homes to feature only low or zero-carbon (LZC) heating. However, residential developers continue to choose conventional high-carbon options such as natural gas boilers over net-zero compatible alternatives. This study explores how UK local authorities (LAs) within the English planning system can encourage residential developers to deploy LZC heating systems within their projects. We adopt an embedded case study design and analyse 30 residential project proposals within two LA areas. Our study examines local planning policies and interactions between developers and LA officers, along with the resultant outcomes, through documentary analysis and expert interviews with local stakeholders. We find that LAs can encourage developers to adopt LZC heating technologies above and beyond what is required nationally. The conditions for this to occur are (1) a planning policy which restricts allowable heating technology options, (2) empowering LA officers to enforce policies, (3) advice and support for developers to consider alternatives, and where necessary, (4) political backing to challenge unwilling developers. Study findings highlight the important role of LAs in creating the conditions for the transition to LZC heating, which show how they can use powers within the planning system to encourage developers to make low carbon choices without the need for direct investment
A Nanophotonic Structure Containing Living Photosynthetic Bacteria
Photosynthetic organisms rely on a series of self-assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna-Matthews-Olson complex to the reaction center. Here, it is shown that by placing living Chlorobaculum tepidum bacteria within a photonic microcavity, the strong exciton-photon coupling regime between a confined cavity mode and exciton states of the chlorosome can be accessed, whereby a coherent exchange of energy between the bacteria and cavity mode results in the formation of polariton states. The polaritons have energy distinct from that of the exciton which can be tuned by modifying the energy of the optical modes of the microcavity. It is believed that this is the first demonstration of the modification of energy levels within living biological systems using a photonic structure
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