64,424 research outputs found
Physical modelling of low-cost modifications to the Crump Weir in order to improve fish passage : evelopment of favourable swimming conditions and investigation of the hydrometric effect
No full textMore than 350 Crump-type weirs (which are triangular in profile) form part of the
Environment Agency's hydrometric network in rivers across England and Wales.
These weirs operate as effective measurement structures and are useful over a large
flow range. However, they also act as barriers that impede the passage of many
species of coarse fish within their natural habitat.
The primary aim of this research project was to recommend modifcations to Crump
weirs in order to improve fish passage, while still allowing the weirs to fulfll their
hydrometric purpose in a reliable way. It was an additional requirement that any
proposed solution(s) be both practical and achievable at low-cost. This is in contrast
to conventional fish pass solutions, that tend to be expensive, are generally not
hydrometrically rated, and most of which were not designed with coarse fish in
mind.
The method used was a model study conducted in the laboratory, which allowed for
a great number of layouts to be trialled. Laboratory research combined with fish
swimming data provides a basis for projecting successful fish ascents. Brimpton weir
on the River Enborne was chosen as a suitable reference on which to base laboratory
model tests.
The preferred arrangement (termed a `rotated-V' layout) was found to be a series of
baffles located on the downstream slope of the Crump weir. These baffles effectively
act as weirs at low
flows and roughness elements at high
flows. Each baffle has a
slot which helps to form a path of ascent for fish. The base closest to the crest was
set at the same height as the crest, as this led to optimum low velocities in the slots
on the downstream slope.
Extensive testing revealed that the proposed solution results in a change in a weir's
hydrometric characteristics. However, it was demonstrated that the deviation of the
coefficient of discharge is predictable. Therefore, it allows for reliable
flow measure-
ment to be achieved (subject to a standardised calibration trial using volumetric
flow
measurement techniques). In addition, a detailed measurement and analysis of wa-
ter velocities within the recommended solution strongly suggest that it substantially
improves on the fish passage capability of a Crump weir
Full-scale performance assessment of aircraft secondary sandwich structure using thermoelastic stress analysis
No full textThe use of resin film infusion (RFI) has been proven to reduce the cost of production of aircraft secondary sandwich structure. In this paper thermoelastic stress analysis (TSA) is used to assess the performance of full scale aircraft sandwich structure panels produced using both the conventional autoclave process and RFI. Finite element (FE) models of both panel types are developed and TSA is used to validate the models
Fennell-Crump House
No full textQueen Anne style house built for Ellen Jackson Murphy (1849-1939), widow of Dallas M. Fennell (1848-1895), bookkeeper. Purchased in 1920 by Edward P. Crump (1862-1943), native of Alabama, chemical corporation superintendent; and wife, Cora B. Toombs (1864-1945), native of Virginia. Remained in family for thirty-nine years
Full Field Strain Analysis of Aircraft Sandwich Structures
No full textA study of the application of two full field optical strain analysis techniques to aircraft standard carbon fibrecomposites is carried out. The goal of the work is to assess the feasibility of using the techniques on full scaletests of secondary sandwich structure aircraft panels. The work concentrates on two techniques: Digital ImageCorrelation (DIC) and Thermoelastic Stress Analysis (TSA). The DIC work focuses on the accuracy of the strainmeasured using different correlation patterns and parameters and the TSA concentrates on the interpretation ofthe data from different surface ply configurations. The work shows that it is possible to obtain meaningful datafrom the two techniques and acts as the preliminary confirmation exercise prior to full scale testing
Design and commission of an experimental test rig to apply a full-scale pressure load on composite sandwich panels representative of aircraft secondary structure
No full textThis paper describes the design of a test rig, which is used to apply a representative pressure load to a full-scale composite sandwich secondary aircraft structure. A generic panel was designed with features to represent those in the composite sandwich secondary aircraft structure. To provide full-field strain data from the panels, the test rig was designed for use with optical measurement techniques such as thermoelastic stress analysis (TSA) and digital image correlation (DIC). TSA requires a cyclic load to be applied to a structure for the measurement of the strain state; therefore, the test rig has been designed to be mounted on a standard servo-hydraulic test machine. As both TSA and DIC require an uninterrupted view of the surface of the test panel, an important consideration in the design is facilitating the optical access for the two techniques. To aid the test rig design a finite element (FE) model was produced. The model provides information on the deflections that must be accommodated by the test rig, and ensures that the stress and strain levels developed in the panel when loaded in the test rig would be sufficient for measurement using TSA and DIC. Finally, initial tests using the test rig have shown it to be capable of achieving the required pressure and maintaining a cyclic load. It was also demonstrated that both TSA and DIC data can be collected from the panels under load, which are used to validate the stress and deflection derived from the FE model
Development of improved methods for the characterisation of organic chemicals emitted into indoor air by building and furnishing products
No full textA wide range of organic compounds are released from building and furnishing products
and these have the potential to adversely affect indoor air quality. There are growing
international requirements for testing and controlling these emissions for the protection
of public health. The test methods require specialist analytical chemistry facilities based
on thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). This
project has addressed the need for better performance and greater automation of the
analysis, as well as development of simpler screening tests.
A variety of products were tested using screening techniques, with an emission cell
method being used as a reference test. Short duration tests, using a micro-scale chamber
at slightly elevated temperature, were shown to have the potential to predict emissions
occurring during longer term reference tests.
Multi-sorbent air sampling tubes, that have the potential to extend the volatility range of
compounds determined by a single TD/GC/MS analysis, were compared with Tenax TA
tubes specified by current standard methods. This showed no difference in performance
for the range of compounds for which Tenax is optimal, with improved performance for
a number of more volatile compounds.
The determination of formaldehyde was investigated using 2-hydroxymethylpiperidine
as a derivatising agent, followed by TD/GC/MS. The results showed the possibility of
this method being developed as an alternative to the current standard method that
involves solvent elution and liquid chromatography.
The performance of a newly developed time-of-flight mass spectrometer was compared
with a standard quadrupole instrument. This showed its potential, with the use of
re-collection, to extend the concentration range of compounds quantified from a single
air sample, of particular benefit for the determination of carcinogens.
New compound identification software was applied to increase automation of analysis
of the TD/GC/MS data. Good correlation with manual processing was achieved,
demonstrating the possibility of routine application to material emissions testing
Performance analysis of a reduced cost manufacturing process for composite aircraft secondary structure
No full textIn the current, environmentally-aware, climate aircraft designers are under increasing pressure toproduce fuel efficient vehicles. Weight reduction is an important method for increasing fuelefficiency. Fibre reinforced polymer (FRP) composites are known to offer weight savings overtraditional metallic components, due to their excellent stiffness and strength to weight ratios.However, the major limiting factor for the use of aerospace quality composites is themanufacturing cost. The costs incurred in the conventional process of prepreg cured in anautoclave are well documented. The research in this thesis is concerned with reducing the cost ofmanufacturing aircraft standard carbon fibre composite sandwich panels, whilst maintainingmechanical performance.The overall aim of the EngD is to provide a unified approach for assessing the performance ofcarbon fibre sandwich secondary structure that are manufactured using several differenttechniques. Cost and performance criteria are defined so that an optimal panel can be produced.The work has been motivated by the industrial sponsor, GE Aviation Systems. Five combinationsof raw material and processing techniques, manufacturing options (MOs) were considered inincremental steps from the baseline of unidirectional prepreg cured in an autoclave to the noncrimpfabric (NCF) infiltrated using resin film infusion (RFI) and cured in a conventional oven.For cost and performance analysis a generic panel has been designed that is representative ofsecondary wing structure on commercial passenger aircraft. The cost was estimated by monitoringthe manufacture of generic panels using each MO, whilst the performance was measured by bothmechanical characterisation tests and by full scale tests on a custom designed rig. The rig applies apressure load using a water cushion and allows optical access to the surface of the panel enablingthe use of optical techniques, i.e. thermoelastic stress analysis (TSA) and digital image correlation(DIC). Feasibility tests on TSA and DIC demonstrated their use on the materials considered inthis thesis, and were used to validate finite element (FE) models.The RFI out-of-autoclave process was found to reduce generic panel manufacture time by almost30%, and the material cost was reduced by almost 40%. The mechanical characterisation testssuggested the ‘new’ process could produce laminates with a similar fibre volume fraction to that ofthe original process and similar in and out-of-plane mechanical properties. The in-plane stiffnesswas slightly reduced by 7 %, but the strength showed an increase of 12%. Full scale tests on thegeneric panels using point out-of-plane deflection measurements and full field TSA demonstratedthe panel produced using the ‘new’ process has adequate performance. Moreover the full-fieldtests indicated an improvement in performance. Further work is required to optimise the design ofthe panel for weight, in particular the weight of the raw material, and investigating methods formodelling the NCF for certification
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Leverage of Environmental Pollutant Crump Rubber on the Dry Sliding Wear Response of Epoxy Composites.
No full textThe effect of crump rubber on the dry sliding wear behavior of epoxy composites is investigated in the present study. Wear tests are carried out for three levels of crump rubber (10, 20, and 30 vol.%), normal applied load (30, 40, and 50 N), and sliding distance (1, 3, and 5 km). The wear behavior of crump rubber-epoxy composites is investigated against EN31 steel discs. The hybrid mathematical approach of Taguchi-coupled Grey Relational Analysis (GRA)-Principal Component Analysis (PCA) is used to examine the influence of crump rubber on the tribological response of composites. Mathematical and experimental results reveal that increasing crump rubber content reduces the wear rate of composites. Composites also show a significant decrease in specific wear values at higher applied loads. Furthermore, the coefficient of friction also shows a decreasing trend with an increase in crump rubber content, indicating the effectiveness of reinforcing crump rubber in a widely used epoxy matrix. Analysis of Variance (ANOVA) results also reveal that the crump rubber content in the composite is a significant parameter to influence the wear characteristic. The post-test temperature of discs increases with an increase in the applied load, while decreasing with an increase in filler loading. Worn surfaces are analyzed using scanning electron microscopy to understand structure-property correlations. Finally, existing studies available in the literature are compared with the wear data of the present study in the form of a property map
The existence of a giant cluster for percolation on large Crump–Mode–Jagers trees
No full textIn this paper we consider random trees associated with the genealogy of Crump-Mode-Jagers processes and perform Bernoulli bond-percolation whose parameter depends on the size of the tree. Our purpose is to show the existence of a giant percolation cluster for appropriate regimes as the size grows. We stress that the family trees of Crump-Mode-Jagers processes include random recursive trees, preferential attachment trees, binary search trees for which this question has been answered by Bertoin [7], as well as (more general) m-ary search trees, fragmentation trees, and median-of-(2l + 1) binary search trees, to name a few, where to our knowledge percolation has not yet been studied.</p
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