Bioinspired low-frequency material characterisation

New-coded signals, transmitted by high-sensitivity broadband transducers in the 40–200 kHz range, allow subwavelength material discrimination and thickness determination of polypropylene, polyvinylchloride, and brass samples. Frequency domain spectra enable simultaneous measurement of material properties including longitudinal sound velocity and the attenuation constant as well as thickness measurements. Laboratory test measurements agree well with model results, with sound velocity prediction errors of less than 1%, and thickness discrimination of at least wavelength/15. The resolution of these measurements has only been matched in the past through methods that utilise higher frequencies. The ability to obtain the same resolution using low frequencies has many advantages, particularly when dealing with highly attenuating materials. This approach differs significantly from past biomimetic approaches where actual or simulated animal signals have been used and consequently has the potential for application in a range of fields where both improved penetration and high resolution are required, such as nondestructive testing and evaluation, geophysics, and medical physics

Exploring community level multi-agency communication and collaboration during the emergency response to the covid-19 pandemic

Objectives This study assesses multi-agency communication and collaboration during the community emergency response to the covid-19 pandemic. Study design Qualitative case-study research. Methods Semi-structured qualitative interviews were conducted with ten officers from organisations involstved in the community response to the pandemic, at strategic or tactical level, within an English local authority (LA) area. Interviews were thematically analysed. Results Horizontal (local/regional) communication and collaboration between the multi-agencies was found to be effective. Participants felt multi-agency groups had a sense of shared identity, partly from pre-existing relationships and a sense of shared common fate. The unified command model, with incident management co-chaired by the local authority, fire and police was found to support joint working, bolstering response effectiveness. There was frustration with vertical (national) communication and collaboration. Messages to local responders were often delivered via daily Government briefings to the public, meaning local responders had little time to consider and implement appropriate actions. Conclusions The study provides new and impactful insights into the community response in an English MBC area during the Covid-19 pandemic. However, findings apply to any high-or-low-income country if their emergency planning/response considers community level integration with multiple-agencies to improve the public health emergency response. Set against existing international literature, show good command-and-control structures, including leadership, training and positive local culture were important for successful communication and collaboration between the multi-agencies. This study highlights some beneficial practices which support recovery and preparedness for future emergencies

Human-induced earthquakes: E-PIE—a generic tool for Evaluating Proposals of Induced Earthquakes

The HiQuake database documents all cases of earthquake sequences proposed on scientific grounds to have been induced by anthropogenic industrial activity. Because these cases range from being highly plausible to unpersuasive, stakeholders have requested cases to be allocated plausibility grades. Since no questionnaire scheme existed that was sufficiently generalized to be applied to the diverse cases in HiQuake, we developed a new scheme for the task. Our scheme for Evaluating Proposals of Induced Earthquakes (E-PIE) comprises nine generalized questions with a simple weighting system to adjust for the variable diagnostic strength of different observations. Results are illustrated using a simple colored pie chart. We describe the E-PIE scheme and illustrate its application in detail using the example cases of the Groningen gas field in the Netherlands, the November 2017 M5.4 Pohang Enhanced Geothermal Systems-related earthquake sequence in South Korea, and the 2001 deep-penetrating bombing of Tora Bora, Afghanistan. To test the performance of E-PIE, five analysts independently applied it to a suite of 23 diverse cases from HiQuake. By far the most diagnostic questions are those concerning spatial and temporal correlations with industrial effects. Other data are diagnostically subsidiary. For individual cases, the agreement between analysts correlated positively with the strength of evidence for human induction. E-PIE results agree well with those from a specialist scheme tailored to fluid-injection cases. Its strong performance confirms its suitability to apply to the entire HiQuake database

Quantum beat photoelectron imaging spectroscopy of Xe in the VUV

Time resolved pump probe measurements of Xe, pumped at 133 nm and probed at 266 nm, are presented. The pump pulse prepared a long lived hyperfine wave packet in the Xe 5p5 2P amp; 8728;1 2 6s2[1 2] amp; 8728;1 manifold E 77185cm amp; 8722;1 9.57eV . The wave packet was monitored via single photon ionization and velocity map photoelectron images were measured. The images provide angle and time resolved data which, when obtained over a large time window 900 ps , constitute a precision quantum beat spectroscopy measurement of the hyperfine state splittings. Additionally, analysis of the full photoelectron image stack provides a quantum beat imaging modality, in which the Fourier components of the photoelectron images correlated with specific beat components can be obtained. This may also permit the extraction of isotope resolved photoelectron images in the frequency domain, in cases where nuclear spins hence beat components can be uniquely assigned to specific isotopes as herein , and also provides phase information relating to the ionization dynamics. The information content of both raw and inverted image stacks is investigated, suggesting the utility of the Fourier analysis methodology in cases where images cannot be inverte

Environmental Regulation Can Arise Under Minimal Assumptions

Models that demonstrate environmental regulation as a consequence of organism and environment coupling all require a number of core assumptions. Many previous models, such as Daisyworld, require that certain environment-altering traits have a selective advantage when those traits also contribute towards global regulation. We present a model that results in the regulation of a global environmental resource through niche construction without employing this and other common assumptions. There is no predetermined environmental optimum towards which regulation should proceed assumed or coded into the model. Nevertheless, polymorphic stable states that resist perturbation emerge from the simulated co-evolution of organisms and environment. In any single simulation a series of different stable states are realised, punctuated by rapid transitions. Regulation is achieved through two main subpopulations that are adapted to slightly different resource values, which force the environmental resource in opposing directions. This maintains the resource within a comparatively narrow band over a wide range of external perturbations. Population driven oscillations in the resource appear to be instrumental in protecting the regulation against mutations that would otherwise destroy it. Sensitivity analysis shows that the regulation is robust to mutation and to a wide range of parameter settings. Given the minimal assumptions employed, the results could reveal a mechanism capable of environmental regulation through the by-products of organisms

Low frequency acoustic and ultrasound waves to characterise layered media

Poor penetration and excessive absorption of high frequencies limit spectroscopic approaches using fast rise pulses for inspecting many engineered structures. So, this study focused on the alternative application of low frequency acoustic and ultrasound waves for the characterisation of challenging structures in airborne and waterborne environments. A simple, transfer matrix model approach was developed for the simulation of 1D sound propagation through layered media that comprise many engineered structures. This model was used to test the feasibility of using sound waves for non-destructive characterisation of an articulated lorry transported trailer and offshore foundation infrastructure. The targets were not in contact with the sound sensors and incorporated highly attenuating layers with acoustic contrasts to the surrounding medium that result in over 90% reflection of incident wave pressure. In both cases, resonances controlled by the thicknesses and interval velocities of component layers modulated sound reflection from, and transmission through the whole structure. These effects were observed as local maxima and minima in the spectra of the transmission and reflection coefficients. These spectral coefficients also determined the modulation to the temporal envelope of a linear frequency modulated pulse used to insonify the targets. In the acoustic study, which comprised only theoretical modelling, discrimination of differing cargo widths and between solid versus empty cargo trailers was possible using the transmission coefficient. In the ultrasound study, which comprised theoretical modelling and experimental testing, discrimination of differing steel and concrete substructure thicknesses and also of gaps between them was possible using the reflection coefficient. The model outcomes indicated while an acoustic system would require around 90–100 dB of dynamic range, an ultrasound system would only require around 40 dB to be effective

Holstein polarons in a strong electric field: delocalized and stretched states

The coherent dynamics of a Holstein polaron in strong electric fields is considered under different regimes. Using analytical and numerical analysis, we show that even for small hopping constant and weak electron-phonon interaction, the original discrete Wannier-Stark (WS) ladder electronic states are each replaced by a semi-continuous band if a resonance condition is satisfied between the phonon frequency and the ladder spacing. In this regime, the original localized WS states can become {\em delocalized}, yielding both `tunneling' and `stretched' polarons. The transport properties of such a system would exhibit a modulation of the phonon replicas in typical tunneling experiments. The modulation will reflect the complex spectra with nearly-fractal structure of the semi-continuous band. In the off-resonance regime, the WS ladder is strongly deformed, although the states are still localized to a degree which depends on the detuning: Both the spacing between the levels in the deformed ladder and the localization length of the resulting eigenfunctions can be adjusted by the applied electric field. We also discuss the regime beyond small hopping constant and weak coupling, and find an interesting mapping to that limit via the Lang-Firsov transformation, which allows one to extend the region of validity of the analysis.Comment: 10 pages, 13 figures, submitted to PR

Ultrasonic testing of laboratory samples representing monopile wind turbine foundations

Wind energy turbines and offshore hydrocarbon platforms rely on injected concrete grout to support and transfer loads between steel substructures. Deterioration of this grout under large operational stresses can lead to a loss of bonding, the formation of gaps, crushing and the loss of grout from the annulus between the steel substructures. In this paper, the integrity of the grout between two steel panels is experimentally tested using a low-frequency ultrasound backscatter method[1]. The experimental results and modelled outcomes[1] are compared for grout condition classes, including: good condition, gaps between the grout and either steel panel and the complete absence of grout. Pearson correlation coefficients of over 83% are observed when comparing the notch magnitudes and the frequencies on the modelled and experimental reflectance spectra of the front and rear gap, as well as missing grout conditions. Kolmogorov-Smirnov (K-S) similarity tests on the modelled and experimental notch magnitudes indicate a 20% significance on the rear gap and front gap spectra and a 10% significance on the missing grout spectra. The significance of these tests supports the potential application of backscattered low-frequency ultrasound for grout condition inspection. However, development of automated condition recognition algorithms, based on either spectral characteristics or time-localised spectral features of the backscatter, is required to make routine inspection commercially viable

A weakly stable algorithm for general Toeplitz systems

We show that a fast algorithm for the QR factorization of a Toeplitz or Hankel matrix A is weakly stable in the sense that R^T.R is close to A^T.A. Thus, when the algorithm is used to solve the semi-normal equations R^T.Rx = A^Tb, we obtain a weakly stable method for the solution of a nonsingular Toeplitz or Hankel linear system Ax = b. The algorithm also applies to the solution of the full-rank Toeplitz or Hankel least squares problem.Comment: 17 pages. An old Technical Report with postscript added. For further details, see http://wwwmaths.anu.edu.au/~brent/pub/pub143.htm

Dynamic Vector and Raster Integrated Data Model Based on Code-Points

With the rapid development of remote sensing technology, the integration of raster data and vector data becomes more and more important. Raster data rnodels are used in tessellation spaces and vector data models are used in discrete spaces respectively. The relationships between tessellation space and discrete space have to be established for integrated data models. The minimum cells where both raster and vector data could be processed have to be defined. As it is very easy to establish relationships between vector points and corresponding raster cells, we defined those raster cells as Code-Points, the minimum cells where both raster and vector data could be processed. All vector elements such as lines, faces and bodies are composed directly or indirectly of Code-Points. This can be done by using interpolation algorithms to Code-Points in real-time. We have developed an integrated data model based on above procedures. In addition, we have developed a geometric primitive library for 3-Dimensional objects in order to improve the processing speed. This library could be hardware realized as a graphic accelerator card. If the conversion between vector and raster could be done in real time, the integrated data model could be used for operational integration of remote sensing and GIS. ? Springer-Verlag 2002.EI