Ill-Posedness and the Bias-Variance Tradeoff in Residual Stress Measurement Inverse Solutions

Background Relaxation methods determine residual stresses by measuring the deformations produced by incremental removal of a subdomain of the specimen. Measured strains at any given increment, determined by the cumulative effect of the relieved stresses, appear as an integral equation, which must be inverted to obtain residual stresses. In practice, stress distributions are discretized by a finite-dimensional basis, to transform the integral equations into a linear system of equations, which is often ill-conditioned. Objective This article demonstrates that the problem is actually ill-posed and comes with an inherent bias-variance tradeoff. Methods The hole drilling method is used as an example application, and the practical effects of ill-posedness are illustrated. Results Traditional regularization of the solution by limiting the resolution of the discretization reduces solution variance (noise) at the expense of increased bias and often results in the ultimately harmful practice of taking fewer data points. A careful analysis including the alternate Tikhonov regularization approach shows that the highest number of measurements should always be taken to reduce the variance for a given regularization scheme. Unfortunately, the variability of a regularized solution cannot be used to build a valid confidence interval, since an unknown bias term is always present in the true overall error. Conclusions The mathematical theory of ill-posed problems provides tools to manage the bias-variance tradeoff on a reasonable statistical basis, especially when the statistical properties of measurement errors are known. In the long run, physical arguments that provide constraints on the true solution would be of utmost importance, as they could regularize the problem without introducing an otherwise unknown bias. Constraining the minimum length scale to some physically meaningful value is one promising possibility

The impact of tidal lagoons on future flood risk on the North Wirral and Conwy coastline, UK

This report considers the viability of tidal lagoons in the North Wirral and Conwy coastlines, to mitigate future flood risk and reduce the cost of damage in these areas. The report is aims to provide information on the feasibility and benefits of tidal lagoons as mitigation and adaptation strategies to future sea-level rise, as part of the RISES-AM project. Sea-level has been rising since instrumental records began in the 1700s, and has been rising at a rate of 3.0 ± 0.7 mm / yr-1 since 1990 (Hay et al., 2015). Low probability, plausible high-end sea-level rise scenarios, where global average warming exceeds 2oC in respect to the pre-industrial level, estimate up to 0.98 m sea-level rise (SLR) by 2100 (Church et al., 2013). There is a move away from hard defences in favour of strategies which can mitigate flood risk benefit and allow coastal communities to adapt to and benefit from high-end SLR scenarios (Linham and Nicholls, 2010). Tidal lagoons could be one such innovative option. The report aims to assess the impact of the construction of tidal lagoons on flood risk on the North Wirral and Conwy coastline, under future high-end sea-level rise scenarios. Computer simulations of extreme flood events, using a 2D hydrodynamic model called LISFLOOD, will estimate changes in the extent and depth of flooding following the construction of a lagoon under both present day and future extreme climate conditions. The results of LISFLOOD suggest that: • Colwyn Bay and the North Wirral coastline are not areas at increased flood risk under baseline future high-end SLR, due to steep topography and existing defences. • Infrastructure at Stanlow oil refinery and Connah’s Quay in the North Wirral domain and residential areas in the Colwyn Bay domain at Llandudno, Rhyl and Prestatyn experience increased flood risk under RCP 4.5 (0.72 m SLR) and RCP 8.5 (0.98 m SLR) with no tidal lagoon. This is due to low-lying topography. • The presence of a tidal lagoon on the North Wirral provides flood risk benefit to infrastructure at Stanlow and Connah’s Quay as the magnitude of tidal currents is limited through the Dee and Mersey Estuary. However the size of the lagoon and the bathymetry of Liverpool Bay may mean the lagoon in this study may not be financially feasible. • The construction of a tidal lagoon at Colwyn Bay increases extent and depth of inundation at Llandudno, Rhyl and Prestatyn under all sea-level rise scenarios. Increased flood risk in these areas following the construction of a tidal lagoon is reason enough not to build a lagoon in this location. Tidal lagoons have the potential to offer flood risk benefit and become part of integrated strategies to minimise flood risk in coastal areas. The benefits of tidal lagoons are dependent on their shape, size and location, and feasibility studies should consider impacts in the near- and far-field

Application of flood risk modelling in a web-based geospatial decision support tool for coastal adaptation to climate change

This is the discussion paper that was under review for the for the journal Natural Hazards and Earth System Sciences (NHESS).The final paper is available from the publisher via DOI: 10.5194/nhess-15-1457-2015A pressing problem facing coastal decision makers is the conversion of “high-level” but plausible climate change assessments into an effective basis for climate change adaptation at the local scale. Here, we describe a web-based, geospatial decision support tool (DST) that provides an assessment of the potential flood risk for populated coastal lowlands arising from future sea-level rise, coastal storms, and high river flows. This DST has been developed to support operational and strategic decision making by enabling the user to explore the flood hazard from extreme events, changes in the extent of the flood-prone areas with sea-level rise, and thresholds of sea-level rise where current policy and resource options are no longer viable. The DST is built in an open-source GIS that uses freely available geospatial data. Flood risk assessments from a combination of LISFLOODFP and SWAB (Shallow Water And Boussinesq) models are embedded within the tool; the user interface enables interrogation of different combinations of coastal and river events under rising-sea-level scenarios. Users can readily vary the input parameters (sea level, storms, wave height and river flow) relative to the present-day topography and infrastructure to identify combinations where significant regime shifts or “tipping points” occur. Two case studies demonstrate the attributes of the DST with respect to the wider coastal community and the UK energy sector. Examples report on the assets at risk and illustrate the extent of flooding in relation to infrastructure access. This informs an economic assessment of potential losses due to climate change and thus provides local authorities and energy operators with essential information on the feasibility of investment for building resilience into vulnerable components of their area of responsibilit

Using milk flow rate to investigate milk ejection in the left and right breasts during simultaneous breast expression in women

<p>Abstract</p> <p>Background</p> <p>Milk ejection is essential for a successful lactation, however techniques to measure milk ejection in women are often complex and invasive. Recent research has demonstrated that at milk ejection, milk duct diameter increased in the breast (measured by ultrasound) at the same time as milk flow rate increased (measured using a weigh balance). This study aimed to evaluate a purpose-built continuous weigh balance (Showmilk, Medela AG) to measure changes in milk flow rate from the breast to identify milk ejections during milk expression. In addition, the Showmilk was used to determine if milk ejection occurred simultaneously in both breasts during double pumping.</p> <p>Methods</p> <p>Increased milk flow rates during single pumping were compared to simultaneous ultrasound measurements of increased milk duct diameters in 14 mothers. In addition, increases in milk flow rate were compared between the left and right breasts of 28 mothers during double pumping for 15 minutes with two separate electric breast pumps attached to two Showmilks to record milk flow rate.</p> <p>Results</p> <p>Increased milk flow rates were associated with increased milk duct diameters during single pumping. The mean number of milk ejections was not different between the Showmilk (4.2 ± 2.0) and ultrasound (4.5 ± 1.5) techniques. Overall, 67 milk ejections were measured and of these, 48 (72%) were identified by both techniques. The left and right breasts responded synchronously with 95.5% of the flow rate increases corresponding between the breasts. The mean number of milk ejections identified by an increase in milk flow rate during double pumping was 5.1 ± 1.7 and 5.0 ± 1.7 for the left and right breasts, respectively. In addition, mothers chose the same expression vacuum for the left (-198 ± 31 mmHg) and right (193 ± 33 mmHg) breasts.</p> <p>Conclusion</p> <p>The Showmilk can simply and non-invasively record milk ejections by measuring increases in milk flow rate that correspond with increases in milk duct diameter. For the first time measurement of milk flow rate has been used to confirm that milk ejections occur simultaneously in the left and right breasts during double pumping. The use of the Showmilk will facilitate further research into the relationship of milk ejection and milk removal.</p

Analysis of Residual Stresses in Laser-Shock-Peened and Shot-Peened Marine Steel Welds

Laser peening is now the preferred method of surface treatment in many applications. The magnitude and depth of the compressive residual stress induced by laser peening can be influenced strongly by the number of peen layers (the number of laser hits at each point) and by processing conditions including the use of a protective ablative layer. In this study, residual stresses have been characterized in laser and shot-peened marine butt welds with a particular focus at the fatigue crack initiation location at the weld toe. X-ray diffraction, synchrotron X-ray diffraction, incremental center-hole drilling, and the contour method were used for determination of residual stress. Results showed that the use of ablative tape increased the surface compressive stress, and the depth of compressive stress increased with an increase in number of peening layers. A key result is that variation of residual stress profile across laser peen spots was seen, and the residual stress magnitude varies between the center and edges of the spots

p53 gene aberrations in non-small-cell lung carcinomas from a smoking population.

We examined 46 non-small-cell lung carcinomas (NSCLCs) for the presence of p53 mutations in exons 4-9, positive p53 immunostaining and loss of heterozygosity (LOH) in the TP53 locus. p53 mutations were detected in 13 tumour samples (28.3%), whereas overexpression of the p53 protein was found in 30 of 45 (67%) samples. Allelic loss was found in 9 of 38 (23.6%) informative cases. The statistical analysis revealed no significant correlation between p53 mutations and clinicopathological data, although mutations appear to occur more frequently in squamous cell carcinomas (7 of 18) than in adenocarcinomas (2 of 15). All but three individuals in this study group smoked. In contrast to previous reports, we found a higher prevalence of GC-->AT transitions than of GC-->TA transversions, as expected in a smoking population. A trend was found between p53-positive immunostaining and a history of heavy smoking (76-126 pack-years) and was inversely correlated with allelic deletion (LOH) at the TP53 locus. Eight of the 12 NSCLCs containing p53 mutations also had concomitant p53 overexpression, and it is of specific note that three of the four tumours containing p53 'mutations' with no overexpression of the p53 protein had either insertions or deletions in the p53 gene. No correlation was found between p53 mutations and fractional allele loss or ras mutations. p53 mutations in this Merseyside population in the UK do not appear to be as common as in other reports for NSCLC and exhibit predominance of GC-->AT transitions preferentially at non-CpG sites, suggesting that other carcinogens in addition to those in tobacco smoke may be involved in NSCLC in the Merseyside area of the UK

Socioeconomic deprivation, urban-rural location and alcohol-related mortality in England and Wales

Background: Many causes of death are directly attributable to the toxic effects of alcohol and deaths from these causes are increasing in the United Kingdom. The aim of this study was to investigate variation in alcohol-related mortality in relation to socioeconomic deprivation, urban-rural location and age within a national context. Methods: An ecological study design was used with data from 8797 standard table wards in England and Wales. The methodology included using the Carstairs Index as a measure of socioeconomic deprivation at the small-area level and the national harmonised classification system for urban and rural areas in England and Wales. Alcohol-related mortality was defined using the National Statistics definition, devised for tracking national trends in alcohol-related deaths. Deaths from liver cirrhosis accounted for 85% of all deaths included in this definition. Deaths from 1999-2003 were examined and 2001 census ward population estimates were used as the denominators. Results: The analysis was based on 28,839 deaths. Alcohol-related mortality rates were higher in men and increased with increasing age, generally reaching peak levels in middle-aged adults. The 45-64 year age group contained a quarter of the total population but accounted for half of all alcohol-related deaths. There was a clear association between alcohol-related mortality and socioeconomic deprivation, with progressively higher rates in more deprived areas. The strength of the association varied with age. Greatest relative inequalities were seen amongst people aged 25-44 years, with relative risks of 4.73 (95% CI 4.00 to 5.59) and 4.24 (95% CI 3.50 to 5.13) for men and women respectively in the most relative to the least deprived quintiles. People living in urban areas experienced higher alcohol-related mortality relative to those living in rural areas, with differences remaining after adjustment for socioeconomic deprivation. Adjusted relative risks for urban relative to rural areas were 1.35 (95% CI 1.20 to 1.52) and 1.13 (95% CI 1.01 to 1.25) for men and women respectively. Conclusions: Large inequalities in alcohol-related mortality exist between sub-groups of the population in England and Wales. These should be considered when designing public health policies to reduce alcohol-related harm