Pulse-Echo Harmonic Generation Measurements for Non-destructive Evaluation

Ultrasonic harmonic generation measurements have shown great potential for detecting nonlinear changes in various materials. Despite this, the practical implementation of the technique in non-destructive evaluation (NDE) has typically been limited to the through transmission setup case, with which problems arise in certain situations. Recently, works in the fields of nonlinear fluids and biomedical imaging have reported different application of the harmonic generation theory by making use of reflective boundaries and beam focusing. It is thought that such techniques may be similarly applied in the field of NDE to enable single-sided nonlinear inspection of components. In this paper, we initially describe a numerical model which has been used to determine the effects of attenuation and acoustic beam diffraction on measurements of the nonlinear parameter beta. We then extend the model to incorporate first the effects of multiple reflecting boundaries in the propagation medium, then of focused source excitation. Simulations, supported by experimental data, show that nonlinear pulse-echo measurements have the potential to provide a viable (and practical) alternative to the usual through-transmission type as a means of measuring beta in solids. Furthermore, it is shown that such measurements may be optimised, both by adjusting the excitation frequency, and by focusing the acoustic source at a certain point relative to the specimen boundary.</p

Data visualization within urban models

Models of urban environments have many uses for town planning, pre-visualization of new building work and utility service planning. Many of these models are three-dimensional, and increasingly there is a move towards real-time presentation of such large models. In this paper we present an algorithm for generating consistent 3D models from a combination of data sources, including Ordnance Survey ground plans, aerial photography and laser height data. Although there have been several demonstrations of automatic generation of building models from 2D vector map data, in this paper we present a very robust solution that generates models that are suitable for real-time presentation. We then demonstrate a novel pollution visualization that uses these models

Suspended timber ground floors: measured heat loss compared with models

There are approximately 6.6 million dwellings in the UK built before 1919, predominantly constructed with suspended timber ground floors whose thermal performance has not been extensively investigated. The results are presented from an in-situ heat-flow measuring campaign conducted at 27 locations on a suspended timber ground floor, and the estimated whole-floor U-value compared with modelled results. Findings highlight a significant variability in heat flow, with increased heat loss near the external perimeter. In-situ measured-point U-values ranged from 0.54 ± 0.09 Wm−2 K−1, when away from the external wall perimeter, to nearly four times as high (2.04 ± 0.21 Wm−2 K−1) when near the perimeter. The results highlight the fact that observing only a few measurements is likely to bias any attempts to derive a whole-floor U-value, which was estimated to be 1.04 ± 0.12 Wm−2 K−1 and nearly twice that derived from current models. This raises questions about the validity of using such models in housing stock models to inform retrofit decision-making and space-heating-reduction interventions. If this disparity between models and measurements exists in the wider stock, a reappraisal of the performance of suspended timber ground floors and heat-loss-reduction potential through this element will be required to support the UK’s carbon-emission-reduction targets

Passive autonomic computing with 'heat-motors' and their compounds

The heat-motor is a simple device that converts thermal-to-mechanical energy, individual heat-motors may be considered as inputs to a ‘class of machine’ that can perform simple Boolean logic operands. This research explores some of the properties of this ‘class of machine’ and an application that uses multiple heatmotors. The high mechanical actuation energy that is generated by the heat-motor is inherted by this ‘class of machine’ and suggests the possibilities for an architecture of reconfiguration in response to different external thermal conditions. The possibility of conditional response to the thermal environment is explored through a case-study project

How plants inspire façades. From plants to architecture: Biomimetic principles for the development of adaptive architectural envelopes

Façades have an important role in the control of energy waste in buildings, nevertheless most of them are designed to provide static design solutions, wasting large amounts of energy to maintain the internal comfort. However, biological adaptation solutions are complex, multi-functional and highly responsive. This paper proposes a biomimetic research of the relationship that can be developed between Biology and Architecture in order to propose innovative façade design solutions. We focus on plants, because of plants, like buildings, lack of movement and remain subject to a specific location. Nevertheless, plants have adapted to the environment developing special means of interaction with changing external issues. This paper provides a methodology to create a data collection of plant adaptations and a design mapping to guide the transfer from biological principles to architectural resources, as well as two design concept cases, opening new perspectives for new possible technical solutions and showing the potential of plant adaptations to environmental conditions at a specific climate. Further step is the transformation of some design concepts into technical solutions through experiments with new technologies that include multi-material 3D printing or advances in material science

Active materials for adaptive architectural envelopes based on plant adaptation principles

In this paper, the authors present research into adaptive architectural envelopes that adapt to environmental changes using active materials, as a result of application of biomimetic principles from plants to architecture. Buildings use large amounts of energy in order to maintain their internal comfort, because conventional buildings are designed to provide a static design solution. Most of the current solutions for facades are not designed for optimum adaptation to contextual issues and needs, while biological solutions to adaptation are often complex, multi-functional and highly responsive. We focus on plant adaptations to the environment, as, due to their immobility, they have developed special means of protection against weather changing conditions. Furthermore, recent developments in new technologies are allowing the possibility to transfer these plant adaptation strategies to technical implementation. These technologies include: multi-material 3D printing, advances in materials science and new capabilities in simulation software. Unlike traditional mechanical activation used for dynamic systems in kinetic facades, adaptive architectural envelopes require no complex electronics, sensors, or actuators. The paper proposes a research of the relationship that can be developed between active materials and environmental issues in order to propose innovative and low-tech design strategies to achieve living envelopes according to plant adaptation principles

Trends and predictors of linkage to HIV outpatient care following diagnosis in the era of expanded testing in England, Wales and Northern Ireland: Results of a national cohort study

OBJECTIVES: We explore trends in linkage to HIV care following diagnosis and investigate the impact of diagnosis setting on linkage in the era of expanded testing. METHODS: All adults (aged ≥ 15 years) diagnosed with HIV between 2005 and 2014 in England, Wales and Northern Ireland (EW&NI) were followed up until the end of 2017. People who died within 1 month of diagnosis were excluded (n = 1009). Trends in linkage to outpatient care (time to first CD4 count) were examined by sub-population and diagnosis setting. Logistic regression identified predictors of delayed linkage of > 1 month, > 3 months and > 1 year post-diagnosis (2012-2014). RESULTS: Overall, 97% (60 250/62 079) of people linked to care; linkage ≤ 1 month was 75% (44 291/59 312), ≤ 3 months was 88% (52 460) and ≤ 1 year was 95% (56 319). Median time to link declined from 15 days [interquartile range (IQR): 4-43] in 2005 to 6 (IQR: 0-20) days in 2014 (similar across sub-populations/diagnosis settings). In multivariable analysis, delayed linkage to care was associated with acquiring HIV through injecting drug use, heterosexual contact or other routes compared with sex between men (> 1 month/3 months/1 year), being diagnosed in earlier years (> 1 month/3 months/1 year) and having a first CD4 ≥ 200 cells/μL (> 3 months/1 year). Diagnosis outside of sexual health clinics, antenatal services and infectious disease units predicted delays of > 1 month. By 3 months, only diagnosis in 'other' settings (prisons, drug services, community and other medical settings) was significant. CONCLUSIONS: Linkage to care following HIV diagnosis is relatively timely in EW&NI. However, non-traditional testing venues should have well-defined referral pathways established to facilitate access to care and treatment

Quality assurance and evaluation (QAE) in Scotland: promoting self-evaluation within and beyond the country

This article looks at policy for quality assurance and evaluation in Scotland, its history and more recent developments, and in particular, at the emphasis on school self-evaluation. It examines the history of the concept, its constituent elements and the role of the Inspectorate in establishing it. Further, the article discusses the Scottish self-evaluation model as a means of promoting the country’s distinctive identity in education within a European frame. It discusses the role of the Standing International Conference of Inspectorates as a major forum for the transmission of ideas about self-evaluation that illuminates the role of networks in promoting Europeanisation