•Creep of the adhesive affects the performance of FRP-strengthened metallic beams.•Designers need to consider linear viscoelastic adhesive behaviour.•Multi-frequency DMA testing to characterise the ...viscoelastic response.•FE analysis of FRP-strengthened metallic beams at warm temperatures.•Effects of viscoelasticity, debonding criteria and differential thermal expansion.
Ambient cured epoxy adhesive is widely used for bonding fibre reinforced polymer (FRP) plates to metallic structures. The present paper examines a typical strengthening adhesive to investigate the effect of adhesive thermo-viscoelasticity. The response of the adhesive was determined using a series of tests using the multi-frequency scanning mode of a dynamic mechanical analyser (DMA). The thermo-mechanical properties of the adhesive were then characterised using time–temperature superposition parameters and a Prony series representation for generalised Maxwell creep. The adhesive response was in turn used within two finite element (FE) models to examine the effect of creep in the adhesive at warm temperatures (<100 °C) on the performance of a lab-scale carbon fibre-reinforced polymer (CFRP) plate strengthened steel beam and a real-scale CFRP plate strengthened cast-iron beam respectively. The study found that thermo-viscoelastic creep of the adhesive bonding layer causes an increase in the slip between the FRP and the structure, which could induce damage in the bonded joint and make the CFRP becomes less effective, potentially resulting in failure of the strengthening system during the long-term service. Differential thermal expansion effects can enhance the joint bonding stress and allow the plate to maintain its contribution to the moment capacity of the beam; however, this benefit could be lost when temperature decrease, and the additional irreversible damage caused by the increased joint stress could reduce the effectiveness of strengthening further..
ABSTRACT
We present sofia 2, the fully automated 3D source finding pipeline for the WALLABY extragalactic H i survey with the Australian SKA Pathfinder (ASKAP). sofia 2 is a reimplementation of parts ...of the original sofia pipeline in the c programming language and makes use of OpenMP for multithreading of the most time-critical algorithms. In addition, we have developed a parallel framework called sofia-X that allows the processing of large data cubes to be split across multiple computing nodes. As a result of these efforts, sofia 2 is substantially faster and comes with a much reduced memory footprint compared to its predecessor, thus allowing the large WALLABY data volumes of hundreds of gigabytes of imaging data per epoch to be processed in real time. The source code has been made publicly available to the entire community under an open-source licence. Performance tests using mock galaxies injected into genuine ASKAP data suggest that in the absence of significant imaging artefacts sofia 2 is capable of achieving near-100 per cent completeness and reliability above an integrated signal-to-noise ratio (SNR) of about 5–6. We also demonstrate that sofia 2 generally recovers the location, integrated flux, and w20 line width of galaxies with high accuracy. Other parameters, including the peak flux density and w50 line width, are more strongly biased due to the influence of the noise on the measurement. In addition, very faint galaxies below an integrated SNR of about 10 may get broken up into multiple components, thus requiring a strategy to identify fragmented sources and ensure that they do not affect the integrity of any scientific analysis based on the sofia 2 output.
This study investigates whether it is necessary to consider nonlinear (rather than linear) adhesive viscoelasticity when considering the behaviour of an FRP-bonded metallic beam at warm service ...temperatures (25 °C, 30 °C and 40 °C). The paper presents finite element analyses that compare the effects of nonlinear and linear creep in the bonded joint for two different FRP-strengthened metallic beams (steel and cast-iron). This modelling work incorporates a viscoelastic adhesive constitutive model determined using a dynamic mechanical analyser for a commonly used ambient cure structural epoxy adhesive. The nonlinear viscoelastic behaviour of the strengthening adhesive was characterised using time-temperature superposition combined with the parallel rheological framework model. The study found that a model incorporating nonlinear viscoelastic creep only leads to a slightly larger joint slip (maximum 1.0% after 1 year) and a slightly lower CFRP axial stress (maximum 2.4% after 1 year), compared to an equivalent model using linear creep. This has a limited impact on the structural performance for the cases studied. In most cases, the simpler linear viscoelastic constitutive model is sufficient to analyse the behaviour of the FRP-bonded metallic beam in a warm environment.
ABSTRACT
We present an analysis of the sky distribution of neutral hydrogen (H i) deficiency and spectral asymmetry for galaxies detected by the H i Parkes All-Sky Survey (HIPASS) as a function of ...projected environment density. Previous studies of galaxy H i deficiency using HIPASS were sensitive to galaxies that are extremely H i rich or poor. We use an updated binning statistic for measuring the global sky distribution of H i deficiency that is sensitive to the average deficiencies. Our analysis confirms the result from previous studies that galaxies residing in denser environments, such as Virgo, are on average more H i deficient than galaxies at lower densities. However, many other individual groups and clusters are not found to be on average significantly H i poor, in contradiction to previous work. In terms of H i spectral asymmetries, we do not recover any significant trend of increasing asymmetry with environment density as found for other galaxy samples. We also investigate the correlation between H i asymmetry and deficiency, but find no variation in the mean asymmetry of galaxies that are H i rich, normal, or poor. This indicates that there is either no dependence of asymmetry on H i deficiency, or a galaxy’s H i deficiency only has a small influence on the measured H i asymmetry that we are unable to observe using only integrated spectra.
ABSTRACT
We present an analysis of morphological, kinematic, and spectral asymmetries in observations of atomic neutral hydrogen (H i) gas from the Local Volume H i Survey (LVHIS), the VLA Imaging of ...Virgo in Atomic Gas (VIVA) survey, and the Hydrogen Accretion in Local Galaxies Survey. With the aim of investigating the impact of the local environment density and stellar mass on the measured H i asymmetries in future large H i surveys, we provide recommendations for the most meaningful measures of asymmetry for use in future analysis. After controlling for stellar mass, we find signs of statistically significant trends of increasing asymmetries with local density. The most significant trend we measure is for the normalized flipped spectrum residual (Aspec), with mean LVHIS and VIVA values of 0.204 ± 0.011 and 0.615 ± 0.068 at average weighted 10th nearest-neighbour galaxy number densities of log (ρ10/Mpc−3) = −1.64 and 0.88, respectively. Looking ahead to the Widefield ASKAP L-band Legacy All-sky Blind survey on the Australian Square Kilometre Array Pathfinder, we estimate that the number of detections will be sufficient to provide coverage over 5 orders of magnitude in both local density and stellar mass increasing the dynamic range and accuracy with which we can probe the effect of these properties on the asymmetry in the distribution of atomic gas in galaxies.
ABSTRACT We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a ...total of 16 years. The light curve showed two distinct peaks with absolute magnitudes and , on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of K and low expansion velocities ( km s−1) for the H i, Ca ii, Ba ii, and K i lines. From archival data spanning 15-8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L ∼ 8.7 L , K, and an estimated mass of M . This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5−10 M ) and NGC 4490-OT (30 M ).
ABSTRACT
We present an H i study of the galaxy group LGG 351 using Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) early science data observed with the Australian Square Kilometre Array ...Pathfinder (ASKAP). LGG 351 resides behind the M 83 group at a velocity range (cz) of ∼3500–4800 km s−1 within the rich Hydra-Centaurus overdensity region. We detect 40 sources with the discovery of a tidally interacting galaxy pair and two new H i sources that are not presented in previous optical catalogues. 23 out of 40 sources have new redshifts derived from the new H i data. This study is the largest WALLABY sub-sample to date and also allows us to further validate the performance of ASKAP and the data reduction pipeline askapsoft. Extended H i emission is seen in six galaxies indicating interaction within the group, although no H i debris is found. We also detect H i in a known ultra-faint dwarf galaxy (dw 1328−29), which demonstrates that it is not a satellite of the M 83 group as previously thought. In conjunction with multiwavelength data, we find that our galaxies follow the atomic gas fraction and baryonic Tully–Fisher scaling relations derived from the GALEX Arecibo SDSS Survey. In addition, majority of our galaxies fall within the star formation main sequence indicating inefficiency of gas removal processes in this loose galaxy group.
Metallic beams can be strengthened using fibre reinforced polymer (FRP) plates that are adhesively bonded to their soffit. This relies critically upon the bonded adhesive joint, and because the ...adhesives are viscoelastic it is known that creep at warm services temperatures can potentially result in large slips that can reduce the effectiveness of the strengthening. This paper examines the impact of adhesive creep upon the performance of an FRP-strengthened metallic beam when subjected to daily temperature cycles and daily load cycles. A finite element (FE) study was conducted that incorporates a linear viscoelastic constitutive model for the adhesive, temperature and load cycles of up to 50 years were considered, and the behaviour of the strengthened beam was examined. Differential thermal expansion between the FRP plate and metallic beam is shown to be significant because it results in both (a) additional instantaneous shear stress across the adhesive joint and (b) the shear stress due to sustained differential thermal expansion results in additional creep of the adhesive that can further reduce the effectiveness of the strengthening. An equivalent cumulative time approach is demonstrated to predict the creep response of the strengthened metallic beam without the need for a complex cyclic analysis.
•Examines the impact of temperature and load cycles on an FRP-strengthened metallic beam.•The viscoelastic adhesive creeps and affects the effectiveness of the strengthening.•Differential thermal expansion results in additional creep, as well instantaneous stresses.•A finite element study, incorporating an experimentally-derived adhesive model.•The impact of the creep is determined by an equivalent cumulative time approach.
Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic ...centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.
The role of CA125 in clinical practice Moss, E L; Hollingworth, J; Reynolds, T M
Journal of clinical pathology,
03/2005, Letnik:
58, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Background: CA125 is a high molecular weight glycoprotein, which is expressed by a large proportion of epithelial ovarian cancers. The sensitivity and specificity of CA125 are poor and there are no ...guidelines produced by the Royal College of Pathologists or the Association of Clinical Biochemists to aid clinicians and laboratories in its most appropriate use. Aim: To identify the patient population having a CA125 measurement and to determine its contribution to individual patient management. Methods: A retrospective case note audit looking at patients who had a CA125 measurement performed between April 2000 and April 2002. Results: The study comprised 799 patients; 751 (94%) were female and 48 (6%) male; 221 (29%) females and 22 (46%) males had an abnormal result. CA125 was mainly used to investigate a wide range of signs and symptoms, and few tests were for follow up or screening of ovarian cancer. In female patients having a CA125 for suspicion of malignancy/ovarian cancer, only 39 (20%) of the abnormal results were caused by ovarian cancer. False positive results were largely caused by another malignancy (48 cases; 26%), benign ovarian disease (26 cases; 14%), and benign gynaecological conditions, particularly leiomyomas (18 cases; 9%). The specificity of CA125 for ovarian cancer increased with concentrations >1000 kU/litre. Conclusions: These results confirm the high false positive rate and poor sensitivity and specificity associated with CA125. The substantial inappropriate usage of CA125 has led to results that are useless to the clinician, have cost implications, and add to patient anxiety and clinical uncertainty.
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