Development of ultrasonic guided wave techniques for examination of non-cylindrical components

AbstractIn the past ten years ultrasonic guided wave systems have become widely used for the rapid large-scale examination of pipes and pipelines in pressure containing systems, for the detection of corrosion and other degradation in service. As a result, the characteristics of the guided wave modes existing in pipes have been studied extensively and are well understood. Advantage is taken of the fact that a pipe is essentially a one-dimensional object and that guided waves travelling along it will return to the sensor location for detection. Guided waves may also be applied to other components which are non-cylindrical, either those of constant cross-section such as railway rails or structural I beams, or constructions consisting of plates. However, in both cases the guided wave systems are more complex than in simple cylinders and successful application of this technique for large scale examination of these constructions requires further development of the understanding of the properties of the waves propagating and regularities of their generation. This paper describes work carried out under the EU-funded LRUCM project to develop techniques for detection of corrosion and cracking in railway rails and structural sheet piles used to retain earth embankments, river banks etc. The work described involved identification of wave modes present, derivation of dispersion curves to describe propagation behaviour and evaluation of experimental data to explain mode conversions and interactions with interfaces observed in the results

Compensation of Strong Thermal Lensing in High Optical Power Cavities

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors such as Advanced LIGO, we show that strong thermal lenses form in accordance with predictions and that they can be compensated using an intra-cavity compensation plate heated on its cylindrical surface. We show that high finesse ~1400 can be achieved in cavities with internal compensation plates, and that the cavity mode structure can be maintained by thermal compensation. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.Comment: 8 page

Using ancient DNA analysis and radiocarbon dating to determine the provenance of an unusual whaling artifact

Natural history collections provide a critical temporal view of past biodiversity and are instrumental in the study of extinct populations. However, the value of historical specimens relies on correct species identification, collection date and collection locality. The Australian National Maritime Museum (ANMM) holds an unusual artifact – an electric lamp made from a dried whale penis – with unknown age, species-of-origin and collection locality. We used ancient DNA methods to generate a partial mitochondrial DNA (mtDNA) genome sequence to establish the identity and provenance of the whale, and accelerator mass spectrometry (AMS) radiocarbon dating to determine the approximate year of death. Mitochondrial DNA sequences from the 16S rRNA gene and the control region indicate that the specimen belonged to a sperm whale (Physeter macrocephalus) and a modern radiocarbon age suggests it was collected post-1950s. We were unable to determine the collection locality of the whale due to the very broad geographic distribution of its mtDNA haplotype. Our results suggest the specimen was possibly collected as a souvenir during post-war whaling, where nearly 30,000 male sperm whales were killed annually. This study supports and extends previous research that applies ancient DNA and radiocarbon dating techniques to enhance the value of natural history collections, by identifying the species-of-origin and age of historical specimens.Caitlin Mudge, Rebecca Dallwitz, Bastien Llamas and Jeremy J. Austi

The cultural capitalists: notes on the ongoing reconfiguration of trafficking culture in Asia

Most analysis of the international flows of the illicit art market has described a global situation in which a postcolonial legacy of acquisition and collection exploits cultural heritage by pulling it westwards towards major international trade nodes in the USA and Europe. As the locus of consumptive global economic power shifts, however, these traditional flows are pulled in other directions: notably for the present commentary, towards and within Asia

Mobility deficit – Rehabilitate, an opportunity for functionality

There are many pathological conditions that cause mobility deficits and that ultimately influence someone’s autonomy.Aims: to evaluate patients with mobility deficits functional status; to implement a Rehabilitation Nursing intervention plan; to monitor health gains through mobility deficits rehabilitation.Conclusion: Early intervention and the implementation of a nursing rehabilitation intervention plan results in health gains (direct or indirect), decreases the risk of developing Pressure Ulcers (PU) and the risk of developing a situation of immobility that affects patients’ autonomy and quality of life

Use of Guided Wave Inspections to Monitor the Integrity of Nuclear Power Station Boilers

This paper describes a ground-breaking application of guided wave testing for the nuclear power industry. Hartlepool and Heysham 1 power stations in the UK contain boilers of a unique ‘pod’ design in which the spiral boiler tubes are supported from above by a central vertical ‘spine’, which is a tubular component approximately 520mm in diameter and 21m long with complex changes in cross-section and attachments along its length. There are 32 boilers in the two stations. The gas which has passed through the reactor core flows down over the boiler tubes, heating the water inside. Only the top 2m of each spine is accessible above the top of the boiler pod. Plant Integrity Ltd was engaged by to inspect these ‘spine’ supports in 2003 using its Teletest guided wave system at statutory outages, which occur on a 3-year interval for each reactor. The Teletest tool was positioned in the only accessible place, just below the inlet header which protrudes approximately 2m from the top of the boiler. A procedure was developed to enable the full 21m length of the spine inside the boiler pod itself to be examined. During one of the regular Teletest inspections, at Heysham 1 power station in September 2013, a significant change in response was detected from the central part of one of the boiler spines. As a result, two of the eight boilers at Heysham 1 Reactor 1 were shut down pending further investigations. The indication was confirmed to be a structurally significant crack in the spine concerned. The crack detected was at the exact position and of the approximate extent reported by Teletest, which had detected the flaw from some 10m away. All four reactors at Hartlepool and Heysham 1 power stations were shut down in the latter part of 2014 while a new safety case for return to service of the remaining boilers was made. There is currently no viable alternative to guided wave inspection for monitoring the integrity of these boiler spines and a significant programme of work has been carried out to demonstrate the performance of Teletest for detection of flaws in these components under a variety of circumstances in order to support the safety case for operation. This has involved theoretical modelling, review of information contained in historical inspection data, practical tests on a full scale mock-up component, development of high temperature Teletest tooling to allow in- service tests and production of automated Teletest data collection equipment to allow real time in-service monitoring of the spines. TWI’s and Plant Integrity’s support enabled all four reactors to be returned to service before the end of 2014

Assessment of Elkhorn Coral Populations and Associated Herbivores in Akumal, Mexico

Coral decline in the Caribbean is marked by the loss of habitat-forming corals, such as elkhorn coral (Acropora palmata). Elkhorn coral recovery has been isolated and patchy, but recently a “re-sheeting” phenomenon, in which elkhorn tissue grows over standing dead coral skeletons, was observed along the reefs in the Mexican Yucatán peninsula. Little is known about the ecological factors contributing to “re-sheeting,” but it is hypothesized that grazing from herbivores provides top-down control of algal growth and promotes coral recovery. The purpose of this study was to evaluate the status of elkhorn populations in Akumal, Mexico and determine if Diadema urchins or parrotfish populations are associated with higher elkhorn abundance and lower algal cover. To achieve this objective, we surveyed 12 spur and groove reef sites in Akumal, where re-sheeting was recently observed, and measured elkhorn coral and herbivore population metrics. We found that both herbivore groups are associated with increasing elkhorn coral presence and cover, and lower macroalgal cover. Additionally, we tested for sampling bias in counting Diadema urchins and found that a significant difference in urchins counts between paired day and night transects on shallow, high complexity reefs. Our results suggest that historically important herbivore groups may be contributing to the recovery of elkhorn coral in Akumal by facilitating tissue re-sheeting