1,079 research outputs found
FAST FLUX TEST FACILITY MONTHLY INFORMAL TECHNICAL PROGRESS REPORT: MARCH 1969
This report was prepared by Battelle-Northwest under Contract No. AT(4S-l)-1830 for the Atomic Energy Commission, Division of Reactor Development and Technology, to summarize technical progress made in the Fast Flux Test Facility Program during March 1969
A point collocation approach to modelling large dissipative silencers
A numerical matching technique known as point collocation is used to model mathematically large dissipative splitter silencers of a type commonly found in HVAC ducts. Transmission loss predictions obtained using point collocation are compared with exact analytic mode matching predictions in the absence of mean flow. Over the frequency range in which analytic mode matching predictions are available, excellent agreement with point collocation transmission loss predictions is observed for a range of large splitter silencers. The validity of using point collocation to tackle large dissipative silencers is established, as is the computational efficiency of the method and its suitability for tackling dissipative silencers of arbitrary, but axially uniform, cross sections
An integral formulation for wave propagation on weakly non-uniform potential flows
An integral formulation for acoustic radiation in moving flows is presented.
It is based on a potential formulation for acoustic radiation on weakly
non-uniform subsonic mean flows. This work is motivated by the absence of
suitable kernels for wave propagation on non-uniform flow. The integral
solution is formulated using a Green's function obtained by combining the
Taylor and Lorentz transformations. Although most conventional approaches based
on either transform solve the Helmholtz problem in a transformed domain, the
current Green's function and associated integral equation are derived in the
physical space. A dimensional error analysis is developed to identify the
limitations of the current formulation. Numerical applications are performed to
assess the accuracy of the integral solution. It is tested as a means of
extrapolating a numerical solution available on the outer boundary of a domain
to the far field, and as a means of solving scattering problems by rigid
surfaces in non-uniform flows. The results show that the error associated with
the physical model deteriorates with increasing frequency and mean flow Mach
number. However, the error is generated only in the domain where mean flow
non-uniformities are significant and is constant in regions where the flow is
uniform
A systems engineering approach to servitisation system modelling and reliability assessment
Companies are changing their business model in order to improve their long term
competitiveness. Once where they provided only products, they are now
providing a service with that product resulting in a reduced cost of ownership.
Such a business case benefits both customer and service supplier only if the
availability of the product, and hence the service, is optimised. For highly
integrated product and service offerings this means it is necessary to assess the
reliability monitoring service which underpins service availability.
Reliability monitoring service assessment requires examination of not only
product monitoring capability but also the effectiveness of the maintenance
response prompted by the detection of fault conditions. In order to address these
seemingly dissimilar aspects of the reliability monitoring service, a methodology
is proposed which defines core aspects of both the product and service
organisation. These core aspects provide a basis from which models of both the
product and service organisation can be produced.
The models themselves though not functionally representative, portray the
primary components of each type of system, the ownership of these system
components and how they are interfaced. These system attributes are then
examined to establish system risk to reliability by inspection, evaluation of the
model or by reference to model source documentation.
The result is a methodology that can be applied to such large scale, highly
integrated systems at either an early stage of development or in latter
development stages. The methodology will identify weaknesses in each system
type, indicating areas which should be considered for system redesign and will
also help inform the analyst of whether or not the reliability monitoring service as
a whole meets the requirements of the proposed business case
Application of steady state finite element and transient finite difference theory to sound propagation in a variable area duct: A comparison with experiment
Sound propagation without flow in a rectangular duct with a converging-diverging area variation was studied experimentally and theoretically. The area variation was of sufficient magnitude to produce large reflections and induce modal scattering. The rms (root-mean-squared) pressure and phase angle on both the flat and curved surface were measured and tabulated. The steady state finite element theory and the transient finite difference theory are in good agreement with the data. It is concluded that numerical finite difference and finite element theories appear ideally suited for handling duct propagation problems which encounter large area variations
Effect of culling on individual badger (Meles meles) behaviour: potential implications for bovine tuberculosis transmission
1. Culling wildlife as a form of disease management can have unexpected and sometimes counterproductive outcomes. In the UK, badgers (Meles meles) are culled in efforts to reduce badger-to-cattle transmission of Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). However, culling has previously been associated with both increased and decreased incidence of M. bovis infection in cattle. 2. The adverse effects of culling have been linked to cull-induced changes in badger ranging, but such changes are not well documented at the individual level. Using GPS-collars, we characterised individual badger behaviour within an area subjected to widespread industry-led culling, comparing it with the same area before culling and with three unculled areas. 3. Culling was associated with a 61% increase (95% CI 27-103%) in monthly home range size, a 39% increase (95% CI 28-51%) in nightly maximum distance from the sett, and a 17% increase (95% CI 11-24%) in displacement between successive GPS-collar locations recorded at 20-minute intervals. Despite travelling further, we found a 91.2 minute (95% CI 67.1-115.3 minute) reduction in the nightly activity time of individual badgers associated with culling. These changes became apparent while culls were ongoing and persisted after culling ended. 4. Expanded ranging in culled areas was associated with individual badgers visiting 45% (95% CI 15-80%) more fields each month, suggesting that surviving individuals had the opportunity to contact more cattle. Moreover, surviving badgers showed a 19.9-fold increase (95% CI 10.8-36.4 increase) in the odds of trespassing into neighbouring group territories, increasing opportunities for intergroup contact. 5. Synthesis and Applications: Badger culling was associated with behavioural changes among surviving badgers which potentially increased opportunities for both badger-to-badger and badger-to-cattle transmission of M. bovis. Furthermore, by reducing the time badgers spent active, culling may have reduced badgers’ accessibility to shooters, potentially undermining subsequent population control efforts. Our results specifically illustrate the challenges posed by badger behaviour to cull-based TB control strategies and furthermore, they highlight the negative impacts culling can have on integrated disease control strategies
A method for exploratory repeated-measures analysis applied to a breast-cancer screening study
When a model may be fitted separately to each individual statistical unit,
inspection of the point estimates may help the statistician to understand
between-individual variability and to identify possible relationships. However,
some information will be lost in such an approach because estimation
uncertainty is disregarded. We present a comparative method for exploratory
repeated-measures analysis to complement the point estimates that was motivated
by and is demonstrated by analysis of data from the CADET II breast-cancer
screening study. The approach helped to flag up some unusual reader behavior,
to assess differences in performance, and to identify potential random-effects
models for further analysis.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS481 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
FAST FLUX TEST FACILITY MONTHLY INFORMAL TECHNICAL PROGRESS REPORT AUGUST 1969
This report was prepared by Battelle-Northwest under Contract No. AT(45-1)-1830 for the Atomic·Energy Commission, Division of Reactor Development and Technology, to summarize technical progress made in the Fast Flux Test Facility Program during August 1969
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