A methodology using health and usage monitoring system data for payload life prediction

© 2018 The Author(s).This paper presents a methodology to monitor the fatigue life of aerospace structures and hence the remaining allowable fatigue life. In fatigue clearance, conservative load assumptions are made. However, in reality, a structure may see much lower loads and so would be usable for much longer. An example ofthis is air carried guided missiles. In the UK, missiles must be decommissioned after a period of carriage. The implementation of a system that can monitor the usage of a missile during its time in service is advantageous to the military customer and provides a competitive advantage for the missile manufacture inexport markets where reduced through-life costs, longer in-service lives and increased safety are desired. The proposed methodology provides a means to monitor the service life of a missile. This paper describes how machine learning algorithms can be used with accelerometers to determine loads on a missile structure which would then be used to predict how long the missile has left in service

Evolutionary history of the ADRB2 gene in humans

No abstract available

Cerebrovascular disease associated with antiphospholipid antibodies: more questions than answers

Neurological syndromes occur in a significant number of patients with antiphospholipid antibodies. The optimal management for these patients however remains uncertain. Our study is a descriptive analysis looking retrospectively at 45 patients who presented to the principal tertiary referral centre in the Australian Capital Territory, with either cerebral arterial or venous thrombosis for which there was no obvious cause for their presentation when initially reviewed. The diagnosis was based on the clinical findings made by one of three neurologists attached to our centre. Radiological findings and the presence of either IgM or IgG anticardiolipin antibodies, IgG anti-beta-2 glycoprotein 1 antibodies or a lupus anticoagulant were then documented. In this group of patients three subgroups were identified: 1. Individuals that fulfilled the Sapporo Classification Criteria 2. Individuals with transiently positive antiphospholipid antibodies and 3. Individuals with persistently low positive antiphospholipid antibodies. The most interesting of these three groups are those individuals with transiently positive antiphospholipid antibodies. A potential cause for presentation was identified in only one patient of this group with documented infective endocarditis and bacteraemia. Comparison with the other two groups suggested that there was little in terms of clinical presentation, radiological findings or intercurrent risk factors for thrombotic disease to distinguish between them. With disappearance of antiphospholipid antibodies, the individuals within this group have not had further thrombotic events. Our observations emphasise the problems that continue to exist in relation to the occurrence of cerebrovascular disease in the context of antiphospholipid antibodies and the optimal management of these stratified groups. Our findings also raise an as yet unanswered question as to the signficance of these transiently positive antiphospholipid antibodies. In the absence of significant intercurrent risk factors our findings would suggest that in the group we describe that they are likely to be of clinical significance

Assurance Argument Patterns and Processes for Machine Learning in Safety-Related Systems

Machine Learnt (ML) components are now widely accepted for use in a range of applications with results that are reported to exceed, under certain conditions, human performance. The adoption of ML components in safety-related domains is restricted, however, unless sufficient assurance can be demonstrated that the use of these components does not compromise safety. In this paper, we present patterns that can be used to develop assurance arguments for demonstrating the safety of the ML components. The argument patterns provide reusable templates for the types of claims that must be made in a compelling argument. On their own, the patterns neither detail the assurance artefacts that must be generated to support the safety claims for a particular system, nor provide guidance on the activities that are required to generate these artefacts. We have therefore also developed a process for the engineering of ML components in which the assurance evidence can be generated at each stage in the ML lifecycle in order to instantiate the argument patterns and create the assurance case for ML components. The patterns and the process could help provide a practical and clear basis for a justifiable deployment of ML components in safety-related systems

Ageing and Degradation of Multiphase Polymer Systems

Ageing can be defined as a slow and irreversible variation as a function of time (in use conditions) of a material structure, morphology or composition leading to a detrimental change in its use properties. The cause of this change can be the own material instability or its interaction with the environment of exposure. The definition so given is that viewed from an application point of view. There are issues associated with this definition that deserve to be mentioned. First, there are ageing mechanisms, essentially of a physical nature as detailed below, that are not irreversible in nature (e.g. crystallinity change, structural recovery, water uptake without loss of the integrity of the chemical structure, etc.), but may lead to a change in the use properties of these materials. The reversibility is in principle achievable by, e.g. thermal treatment or drying. However, this is not necessarily compatible with the use of materials as pieces, or the material will evolve again anyway when exposed to use environmental stresses. Second, irreversible material evolution in itself does not necessarily imply a detrimental change of use properties. It can even result in an improvement of properties. This represents indeed a marked difficulty when attempting to define so-called ‘ageing markers’ for materials, i.e. material properties to be monitored for health monitoring purpose: the marker must be sensitive enough so as to provide the early signs of material evolution but, at the same time, there should be a correlation between the evolution of the marker and the changes in use properties

Planar and spherical stick indices of knots

The stick index of a knot is the least number of line segments required to build the knot in space. We define two analogous 2-dimensional invariants, the planar stick index, which is the least number of line segments in the plane to build a projection, and the spherical stick index, which is the least number of great circle arcs to build a projection on the sphere. We find bounds on these quantities in terms of other knot invariants, and give planar stick and spherical stick constructions for torus knots and for compositions of trefoils. In particular, unlike most knot invariants,we show that the spherical stick index distinguishes between the granny and square knots, and that composing a nontrivial knot with a second nontrivial knot need not increase its spherical stick index