Optical Non-Contact Railway Track Measurement with Static Terrestrial Laser Scanning to Better than 1.5mm RMS

The railway industry requires track to be monitored for a variety of reasons, particularly when any type of physical works take place within the vicinity of the asset (e.g. demolition, construction and redevelopment works). Terrestrial laser scanning (TLS) has considerable potential as a survey method for rail measurement due to its non-contact nature and independence from physical targeting at track level. The consensus from recently published work using static terrestrial laser scanning is that rail measurements to the order of 3mm RMS are routinely possible. Such measures are appropriate for extracting the gauge, cant and twist parameters required by the rail industry, however engineering specifications designed to ensure safe and comfortable running of the trains ideally require measurements of better quality. This paper utilises standard design rail profiles from the UK industry to optimise the way in which TLS point cloud data are fitted to the rail geometry. The work is based on the use of off the shelf phase-based TLS systems each capable of delivering single point measurements of the order of 5mm to cooperative surfaces. The paper describes a workflow which focuses the fitting process onto discrete planar rail elements derived from the design rail geometry. The planar fitting process is improved through understanding how data from these scanners respond to rail surfaces. Of particular importance is the removal of noisy data from the shiny running surfaces. Results from a sequence of multi-station TLS surveys of the same set of double tracks taken from platform level highlight the capability to obtain fits to the rail model of better than 1.5mm RMS. Whilst fitting can be carried out on a single side of a rail, the paper highlights the challenge of obtaining an accurate TLS registration necessary to extract both sides of each rail to the same level of accuracy. This configuration is proven over inter-TLS instrument separations of the order of 30m and demonstrates the TLS network coverage necessary to achieve such results even in the presence of an occluding electric third rail

Observing the emergence of phase biaxiality in a polar smectic A system via polarised Raman spectroscopy

We report polarised Raman spectroscopy, optical and dielectric properties of an asymmetric bent-core compound derived from 3-hydroxybenzoic acid with a long terminal chain at one end and a nitro group at the other. Earlier X-ray scattering experiments on the compound suggested a partial bilayer smectic A phase (SmA_d) and a partial bilayer biaxial antiferroelectric smectic A phase (SmA_d P_A) in the material. The dielectric behaviour, the microscopic textures and conoscopy experiments all explicitly show that the compound exhibits two different phases, with the lower temperature phase biaxial in nature. Raman spectroscopy was used to determine the temperature evolution of the uniaxial order parameters 〈P_2 〉 and 〈P_4 〉, deduced from analysis of the depolarisation ratio, informed by modelling the bent-core structure. Anomalously low values were measured (less than 0.5 and 0.15 respectively) which could suggest that the smectic A phase may be de Vries like in nature, rather than a partial bilayer structure. Raman spectroscopy was also used to investigate the biaxial nature of the SmA_d P_A phase. The effect that the biaxial order parameters 〈P_220 〉,〈P_420 〉 and 〈P_440 〉 has have on the depolarisation ratio is calculated. By making the assumption of an approximately continuous increase in the 〈P_2 〉 and 〈P_4 〉 order parameters, it was possible to deduce the behaviour of the biaxial order parameters in the biaxial SmA_d P_A phase; the emergence of biaxial order in the system is clearly demonstrated as all of the biaxial order parameters increase in magnitude as the temperature decreases in the (SmA_d P_A) phase. The dielectric studies show that the perpendicular component of the dielectric permittivity increases from 10 to 70 in the SmA_d phase and decreases from 70 to 45 in the SmA_d P_A phase. A strongly temperature dependent relaxation frequency with a large value ~400 kHz is observed in the SmA_d phase. On the other, the SmA_d P_A phase exhibits a weakly temperature dependent relaxation frequency at ~100 kH

Does My Stigma Look Big in This? Considering the acceptability and desirability in the inclusive design of technology products

This paper examines the relationship between stigmatic effects of design of technology products for the older and disabled and contextualizes this within wider social themes such as the functional, social, medical and technology models of disability. Inclusive design approaches are identified as unbiased methods for designing for the wider population that may accommodate the needs and desires of people with impairments, therefore reducing ’aesthetic stigma’. Two case studies illustrate stigmatic and nonstigmatic designs

On the Growth of Al_2 O_3 Scales

Understanding the growth of Al2O3 scales requires knowledge of the details of the chemical reactions at the scale–gas and scale–metal interfaces, which in turn requires specifying how the creation/annihilation of O and Al vacancies occurs at these interfaces. The availability of the necessary electrons and holes to allow for such creation/annihilation is a crucial aspect of the scaling reaction. The electronic band structure of polycrystalline Al2O3 thus plays a decisive role in scale formation and is considered in detail, including the implications of a density functional theory (DFT) calculation of the band structure of a Σ7 View the MathML source bicrystal boundary, for which the atomic structure of the boundary was known from an independent DFT energy-minimization calculation and comparisons with an atomic-resolution transmission electron micrograph of the same boundary. DFT calculations of the formation energy of O and Al vacancies in bulk Al2O3 in various charge states as a function of the Fermi energy suggested that electronic conduction in Al2O3 scales most likely involves excitation of both electrons and holes, which are localized on singly charged O vacancies, View the MathML source and doubly charged Al vacancies, View the MathML source, respectively. We also consider the variation of the Fermi level across the scale and bending (“tilting”) of the conduction band minimum and valence band maximum due to the electric field developed during the scaling reaction. The band structure calculations suggest a new mechanism for the “reactive element” effect—a consequence of segregation of Y, Hf, etc., to grain boundaries in Al2O3 scales, which results in improved oxidation resistance—namely, that the effect is due to the modification of the near-band edge grain-boundary defect states rather than any blocking of diffusion pathways, as previously postulated. Secondly, Al2O3 scale formation is dominated by grain boundary as opposed to lattice diffusion, and there is unambiguous evidence for both O and Al countercurrent transport in Al2O3 scale-forming alloys. We postulate that such transport is mediated by migration of grain boundary disconnections containing charged jogs, rather than by jumping of isolated point defects in random high-angle grain boundaries

Communication with young people in paediatric and adult endocrine consultations: an intervention development and feasibility study

Background: Communication is complex in endocrine care, particularly during transition from paediatric to adult services. The aims of this study were to examine the feasibility of interventions to support young people to interact with clinicians. Methods: Development and evaluation of a complex intervention in 2 phases: Pre-intervention observational study; Intervention feasibility study. Purposive sample of recordings of 62 consultations with 58 young people aged 11-25 years with long-term endocrine conditions in two paediatric and two adult endocrine clinics. Proportion of time talked during consultations, number and direction of questions asked; Paediatric Consultation Assessment Tool (PCAT); OPTION shared decision making tool; Medical Information Satisfaction Scale (MISS- 21). Young people were invited to use one or more of: a prompt sheet to help them influence consultation agendas and raise questions; a summary sheet to record key information; and the www.explain.me.uk website. Results: Nearly two thirds of young people (63%) chose to use at least one communication intervention. Higher ratings for two PCAT items (95% CI 0.0 to 1.1 and 0.1 to 1.7) suggest interventions can support consultation skills. A higher proportion of accompanying persons (83%) than young people (64%) directed questions to clinicians. The proportion of young people asking questions was higher (84%) in the intervention phase than in the observation phase (71%). Conclusions: Interventions were acceptable and feasible. The Intervention phase was associated with YP asking more questions, which implies that the availability of interventions could promote interactivity

Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers

The nematic twist-bend (NTB) phase, exhibited by certain thermotropic liquid crystalline (LC) dimers, represents a new orientationally ordered mesophase -- the first distinct nematic variant discovered in many years. The NTB phase is distinguished by a heliconical winding of the average molecular long axis (director) with a remarkably short (nanoscale) pitch and, in systems of achiral dimers, with an equal probability to form right- and left-handed domains. The NTB structure thus provides another fascinating example of spontaneous chiral symmetry breaking in nature. The order parameter driving the formation of the heliconical state has been theoretically conjectured to be a polarization field, deriving from the bent conformation of the dimers, that rotates helically with the same nanoscale pitch as the director field. It therefore presents a significant challenge for experimental detection. Here we report a second harmonic light scattering (SHLS) study on two achiral, NTB-forming LCs, which is sensitive to the polarization field due to micron-scale distortion of the helical structure associated with naturally-occurring textural defects. These defects are parabolic focal conics of smectic-like ``pseudo-layers", defined by planes of equivalent phase in a coarse-grained description of the NTB state. Our SHLS data are explained by a coarse-grained free energy density that combines a Landau-deGennes expansion of the polarization field, the elastic energy of a nematic, and a linear coupling between the two

Substrate Effect on the High Temperature Oxidation Behavior of a Pt-modified Aluminide Coating. Part II: Long-term Cyclic-oxidation Tests at 1,050 C

This second part of a two-part study is devoted to the effect of the substrate on the long-term, cyclic-oxidation behavior at 1,050 C of RT22 industrial coating deposited on three Ni-base superalloys (CMSX-4, SCB, and IN792). Cyclicoxidation tests at 1,050 C were performed for up to 58 cycles of 300 h (i.e., 17,400 h of heating at 1,050 C). For such test conditions, interdiffusion between the coating and its substrate plays a larger role in the damage process of the system than during isothermal tests at 900, 1,050, and 1,150 C for 100 h and cyclicoxidation tests at 900 C which were reported in part I [N. Vialas and D. Monceau, Oxidation of Metals 66, 155 (2006)]. The results reported in the present paper show that interdiffusion has an important effect on long-term, cyclic-oxidation resistance, so that clear differences can be observed between different superalloys protected with the same aluminide coating. Net-mass-change (NMC) curves show the better cyclic-oxidation behavior of the RT22/IN792 system whereas uncoated CMSX-4 has the best cyclic-oxidation resistance among the three superalloys studied. The importance of the interactions between the superalloy substrate and its coating is then demonstrated. The effect of the substrate on cyclic-oxidation behavior is related to the extent of oxide scale spalling and to the evolution of microstructural features of the coatings tested. SEM examinations of coating surfaces and cross sections show that spalling on RT22/CMSX-4 and RT22/SCB was favored by the presence of deep voids localized at the coating/oxide interface. Some of these voids can act as nucleation sites for scale spallation. The formation of such interfacial voids was always observed when the b to c0 transformation leads to the formation of a two-phase b/c0 layer in contact with the alumina scale. On the contrary, no voids were observed in RT22/IN792, since this b to c0 transformation occurs gradually by an inward transformation of b leading to the formation of a continuous layer of c0 phase, parallel to the metal/scale interface

Beyond clustering: mean-field dynamics on networks with arbitrary subgraph composition

Clustering is the propensity of nodes that share a common neighbour to be connected. It is ubiquitous in many networks but poses many modelling challenges. Clustering typically manifests itself by a higher than expected frequency of triangles, and this has led to the principle of constructing networks from such building blocks. This approach has been generalised to networks being constructed from a set of more exotic subgraphs. As long as these are fully connected, it is then possible to derive mean-field models that approximate epidemic dynamics well. However, there are virtually no results for non-fully connected subgraphs. In this paper, we provide a general and automated approach to deriving a set of ordinary differential equations, or mean-field model, that describes, to a high degree of accuracy, the expected values of system-level quantities, such as the prevalence of infection. Our approach offers a previously unattainable degree of control over the arrangement of subgraphs and network characteristics such as classical node degree, variance and clustering. The combination of these features makes it possible to generate families of networks with different subgraph compositions while keeping classical network metrics constant. Using our approach, we show that higher-order structure realised either through the introduction of loops of different sizes or by generating networks based on different subgraphs but with identical degree distribution and clustering, leads to non-negligible differences in epidemic dynamics