56,627 research outputs found
The measurement of near wall flows using pneumatic wedge probes.
Get PDFThe three hole, wedge-type pneumatic pressure probe represents a robust
traverse probe design which is widely used for total and static pressure and yaw angle
measurements in turbomachinery. However, unsteady flows are incorrectly averaged due
to pneumatic meaning errors in the pressure pipes. Wedge probes also fail to measure the
correct static pressure when operating in close proximity to a wall through which the
probe is inserted. Thirdly, the aerodynamic calibration obtained for a wedge-type probe
in a closed wind tunnel differs appreciably from that obtained in an open jet. If not
corrected, these errors will corrupt any calculation of turbomachinery blade row
performance.
In this investigation, the second and third effects described above have been
addressed. A factorial experiment was completed in which the influence of seven
variables on the wall proximity effect was quantified. Flow visualisation studies were
performed to understand the responsible flow mechanisms. Two regions of re-circulating
flow were identified in the probe wake, the structure of which depended on the probe
immersion. Similar re-circulatory flows were resolved from three-dimensional
computational fluid dynamics (CFD) calculations of the flow over a wedge probe. A link
between the probe wake re-circulations and flow over the wedge faces was established.
Based on this understanding of the flow structures, a model was developed from which
the wall proximity effect could be predicted for a given set of conditions.
Wedge probe calibrations were completed in a closed wind tunnel and in two
open jets. Discrepancies in the static pressure coefficient and yaw angle sensitivity results
were found. These were partially explained in terms of modifications to the probe wake
structure which occurred when the probes were calibrated in the open jet facilities.
Procedures for correcting the wall proximity effect and for avoiding the facility
dependence of wedge probe calibrations were developed from this understanding of the
flow mechanisms involved.
Based on the findings of this investigation, a novel wedge probe was designed to
minimise the wall proximity effect. This probe demonstrated a reduction in the wall
proximity effect, from 20% dynamic head with current designs, to 3% dynamic head at
flows typical of high speed turbomachinery
Cylindrical-wave diffraction by a rational wedge
No full textIn this paper, new expressions for the field produced by the diffraction of a cylindrical wave by a wedge, whose angle can be expressed as a rational multiple of π are given. The solutions are expressed in terms of source terms and real integrals that represent the diffracted field. The general result obtained includes as special cases, Macdonald's solution for diffraction by a half plane, a solution for Carslaw's problem of diffraction by a wedge of open angle 2π\3, and a new representation for the solution of the problem of diffraction by a mixed soft-hard half plane
Design of trials for interrupting the transmission of endemic pathogens
Get PDFBackground: Many interventions against infectious diseases have geographically diffuse effects. This leads to contamination between arms in cluster-randomized trials (CRTs). Pathogen elimination is the goal of many intervention programs against infectious agents, but contamination means that standard CRT designs and analyses do not provide inferences about the potential of interventions to interrupt pathogen transmission at maximum scale-up. Methods: A generic model of disease transmission was used to simulate infections in stepped wedge cluster-randomized trials (SWCRTs) of a transmission-reducing intervention, where the intervention has spatially diffuse effects. Simulations of such trials were then used to examine the potential of such designs for providing generalizable causal inferences about the impact of such interventions, including measurements of the contamination effects. The simulations were applied to the geography of Rusinga Island, Lake Victoria, Kenya, the site of the SolarMal trial on the use of odor-baited mosquito traps to eliminate Plasmodium falciparum malaria. These were used to compare variants in the proposed SWCRT designs for the SolarMal trial. Results: Measures of contamination effects were found that could be assessed in the simulated trials. Inspired by analyses of trials of insecticide-treated nets against malaria when applied to the geography of the SolarMal trial, these measures were found to be robust to different variants of SWCRT design. Analyses of the likely extent of contamination effects supported the choice of cluster size for the trial. Conclusions: The SWCRT is an appropriate design for trials that assess the feasibility of local elimination of a pathogen. The effects of incomplete coverage can be estimated by analyzing the extent of contamination between arms in such trials, and the estimates also support inferences about causality. The SolarMal example illustrates how generic transmission models incorporating spatial smoothing can be used to simulate such trials for a power calculation and optimization of cluster size and randomization strategies. The approach is applicable to a range of infectious diseases transmitted via environmental reservoirs or via arthropod vectors.</p
Sedimentary filling of a wedge-top basin and relationship with the foredeep (Middle Miocene Marnoso-arenacea Formation, northern Apennines)
No full textThe Middle Miocene Marnoso-arenacea Formation at Deruta in the northern Apennines of Italy rests unconformably on an orogenic wedge adjacent to the Adriatic foredeep. Based on a detailed facies analysis, the succession reveals two genetically related depositional systems: a distal delta-fed sand-rich system and a more proximal fan-delta slope system. Petrographic data confirm the genetic relationship between the two depositional systems, with the fan-delta slope feeding the basinward sand-rich system. The Deruta depositional setting shows a multi-step sedimentary evolution controlled by tectonically induced relative sea-level changes. The first stage, corresponding to a sea-level rise, promoted deposition in a wedge-top basin of pebbly sand and sand lobes (delta-fed). The second stage, characterized by intense tectonic activity (uplift) and sea-level fall, promoted accumulation of a prograding fan-delta slope replacing the sand-rich lobes. This phase was dominated by mass failures and methanogenic cold seepages. During these two stages, the wedge-top basin was isolated from the adjacent foredeep. Only during the third stage was a connection established, with the development of a deep-sea fan in the foredeep, fed by a deltaic depositional system. © Springer-Verlag 2008
Ghost story. I. Wedge states in the oscillator formalism
No full textThis paper is primarily devoted to the ghost wedge states in string field theory formulated with the oscillator formalism. Our aim is to prove, using such formalism, that the wedge states can be expressed asSCOPUS: ar.jinfo:eu-repo/semantics/publishe
High frequency diffraction of an electromagnetic plane wave by an imperfectly conducting rectangular cylinder
No full textCopyright @ 2011 IEEEWe shall consider the the problem of determining the scattered far wave field produced when a plane E-polarized wave is incident on an imperfectly conducting rectangular cylinder. By using the the uniform asymptotic solution for the problem of the diffraction of a plane wave by a right-angled impedance wedge, in conjunction with Keller's method, the a high frequency far field solution to the problem is given
A cluster randomised stepped wedge trial to evaluate the effectiveness of a multifaceted information technology-based intervention in reducing high-risk prescribing of non-steroidal anti-inflammatory drugs and antiplatelets in primary medical care: the DQIP study protocol
Get PDF<p>Background - High-risk prescribing of non-steroidal anti-inflammatory drugs (NSAIDs) and antiplatelet agents accounts for a significant proportion of hospital admissions due to preventable adverse drug events. The recently completed PINCER trial has demonstrated that a one-off pharmacist-led information technology (IT)-based intervention can significantly reduce high-risk prescribing in primary care, but there is evidence that effects decrease over time and employing additional pharmacists to facilitate change may not be sustainable.</p>
<p>Methods/design - We will conduct a cluster randomised controlled with a stepped wedge design in 40 volunteer general practices in two Scottish health boards. Eligible practices are those that are using the INPS Vision clinical IT system, and have agreed to have relevant medication-related data to be automatically extracted from their electronic medical records. All practices (clusters) that agree to take part will receive the data-driven quality improvement in primary care (DQIP) intervention, but will be randomised to one of 10 start dates. The DQIP intervention has three components: a web-based informatics tool that provides weekly updated feedback of targeted prescribing at practice level, prompts the review of individual patients affected, and summarises each patient's relevant risk factors and prescribing; an outreach visit providing education on targeted prescribing and training in the use of the informatics tool; and a fixed payment of 350 GBP (560 USD; 403 EUR) up front and a small payment of 15 GBP (24 USD; 17 EUR) for each patient reviewed in the 12 months of the intervention. We hypothesise that the DQIP intervention will reduce a composite of nine previously validated measures of high-risk prescribing. Due to the nature of the intervention, it is not possible to blind practices, the core research team, or the data analyst. However, outcome assessment is entirely objective and automated. There will additionally be a process and economic evaluation alongside the main trial.</p>
<p>Discussion - The DQIP intervention is an example of a potentially sustainable safety improvement intervention that builds on the existing National Health Service IT-infrastructure to facilitate systematic management of high-risk prescribing by existing practice staff. Although the focus in this trial is on Non-steroidal anti-inflammatory drugs and antiplatelets, we anticipate that the tested intervention would be generalisable to other types of prescribing if shown to be effective.</p>
Fluid expulsion in accretionary wedges: what can we learn from Miocene seep carbonates (Emilia and Tuscan Apennines, Italy)
No full textSeepage of hydrocarbon-rich fluids is a common process
in accre onary wedges where tectonic thickening and
underpla ng generate pore-fluid overpressures and
induce fluid migra on (Bohrmann et al., 2002; Gill et al.,
2005; Ding et al., 2010; Crutchley et al., 2015; Klaucke et
al., 2015). The migra on and expulsion of methane-rich
fluids promote the precipita on of a variety of authigenic
minerals on the seafloor or within the sediments, i.e.
carbonates (aragonite, calcite, dolomite), sulfides and
sulphates, forming crusts, concre ons and build-ups.
Reduced compounds in the fluids also sustain peculiar
microbial consor a and macrofaunal communi es
(Teichert et al., 2005; Campbell, 2006) (Fig. 1).
It is widely recognized that the most reliable indicators of
fossil cold seeps are the anomalously nega ve carbon
13 isotope composi on of the carbonates, with d C values as
low as -60‰ VPDB (Judd and Hovland, 2009), the peculiar
chemosynthe c bivalves (Lucinidae and Vesicomyidae)
and specific biomarkers (e.g. Taviani, 2014; Peckmann et
al., 2002; Grillenzoni et al., 2017).
In the northern Apennine orogenic belt, several outcrops
of authigenic carbonates tes fy for Miocene seepage
ac vity (Terzi et al., 1994; Dela Pierre et al., 2010; Con et
al., 2017). These carbonates show highly depleted d13C
signatures and host large chemosynthe c bivalve
assemblages (mainly giant lucinids)(Grillenzoni et al.,
2017), thus tes fying a long and complex history of
methane-rich fluid ven ng on the sea floor. Apenninic
carbonate deposits bearing fossil chemosynthe c fauna
have been found in various domains and basin types, from
wedge-top basins to the slope of the accre onary wedge,
and in the inner foredeep (Con and Fontana, 1999;
Argen no et al., 2019a) (Figs 2, 3).
In the following, we summarize and describe the main
features of the Apennine seep carbonates, from field
observa ons to geochemical features
Compact multi-anvil wedge-type high pressure apparatus
No full textApparatus for generating high pressures by application of force by an anvil against each face of a solid polyhedron is described. The equipment constructed utilizes a tetrahedron of pyrophyllite and four tungsten carbide anvils as described earlier by H. T. Hall. External force is applied to only one of the anvils, and wedge reaction forces act on the other anvils, permitting the equipment to be used in a conventional hydraulic press. Examples of results of use of the equipment are given. Success of the design has been shown by the repeated generation of pressures in excess of 100,000 atmospheres indicating that large existing presses might be used to generate pressures of this order in volumes of several cubic inches. For higher pressures a two-stage multi-anvil apparatus is proposed in which the second-stage anvils are embedded in a large pyrophyllite tetrahedron to obtain necessary supporting forces
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