Model selection for dynamic reduction-based structural health monitoring following the Bayesian evidence approach

© 2019 Elsevier Ltd There usually exist multitudinous finite element (FE) models with varying level of complexity which can be developed from the engineering judgment for the purpose of structural system identification and health monitoring. By following the theory of Bayesian evidence statistic, this paper proposes a methodology to investigate the issues of FE model-class selection for choosing suitable parameterized structural models utilized in dynamic reduction-based structural health monitoring (SHM). By employing the concept of information divergence, the amount of information needed to be extracted from the measured data is explicitly quantified during the procedure of FE model updating-based structural health monitoring. Then, for achieving a trade-off between the complexity of a parameterized FE model class and that of its corresponding information-theoretic interpretation, such information is utilized for penalizing the complexity of model class to ensure that a relatively simple parameterization scheme can be achieved. The proposed methodology consists of calibration and subsequent monitoring stages, and the information obtained in the former stage is utilized as pseudo-data which is learned by the latter stage to improve the model parameter estimation by implementing the delayed rejection adaptive Metropolis algorithm. Through numerical case studies conducted for a four-storey two-bay steel frame structure considering semi-rigid connections as well as laboratory experiment performed for a two-storey bolt-connected steel frame model, the feasibility and validity of proposed methodology is demonstrated

Core–shell grain structures and ferroelectric properties of Na0.5K0.5NbO3–LiTaO3–BiScO3 piezoelectric ceramics

Legislation arising from health and environmental concerns has intensified research into finding suitable alternatives to lead-based piezoceramics. Recently, solid solutions based on sodium potassium niobate (K,Na)NbO3 (KNN) have become one of the globally-important lead-free counterparts, due to their favourable dielectric and piezoelectric properties. This data article provides information on the ferroelectric properties and core–shell grain structures for the system, (1−y)[(1−x)Na0.5K0.5NbO3 – xLiTaO3] – yBiScO3 (x=0–0.1, y=0.02, abbreviated as KNN–xLT–2BS). We show elemental analysis with aid of TEM spot-EDX to identify three-type grain-types in the KNN–LT–BS ternary system. Melting behaviour has been assessed using a tube furnace with build-in camera. Details for the ferroelectric properties and core–shell chemical segregation are illustrated

N(HI) and jet power/emission in AGNs

Neutral hydrogen (HI) 21 cm absorption has been detected against more and more powerful radio jets. In this work, based on the Guppta et al. 2006a sample, we present our preliminary study of the correlations between the HI column density N(HI) and the jet power, N(HI) versus the low frequency luminosity at 408MHz, and N(HI) versus the radio luminosity at 1400MHz.Comment: 3 pages, 1 figures, Multiwavelength Variability of Blazars Guangzhou, China, Sept. 22-24, 2010; will be published by JA

Changes in retirement plans in the English older population during the COVID-19 pandemic: The roles of health factors and financial insecurity

Over the course of 2020 and 2021, the COVID-19 pandemic disrupted lives globally. In the UK, unemployment rate continued to increase during and post-lockdown periods, and job security and financial wellbeing deteriorated. It is important to understand whether individual decisions related to retirement plans have changed systematically as a result of the pandemic, especially among older adults who experienced greater rates of pandemic unemployment. Using the English Longitudinal Study of Ageing, this article examines changes in retirement plans of older adults during the COVID-19 pandemic and estimates the impact of health and financial circumstances on these changes. In June/July 2020, 5% of 2095 participants reported planning earlier retirement, while 9% reported planning later retirement. We found that poor self-rated health and financial insecurity were associated with intentions to postpone retirement. Additional risk of later retirement associated with poor health was detected among those experiencing financial insecurity. In November/December 2020, 7% of 1845 participants reported planning earlier retirement, while 12% reported planning later retirement. We found that poor health was predictive of a lower relative risk of later retirement, while depressive symptomology and financial insecurity predicted a higher relative risk of later retirement. The findings imply a contextual role of health factors in, and a persistent influence of financial insecurity on, retirement planning in the older population

Case study on user knowledge and design knowledge in product form design

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Lithium Intercalation into the Excitonic Insulator Candidate Ta2NiSe5

A new reduced phase derived from the excitonic insulator candidate Ta2NiSe5 has been synthesized via the intercalation of lithium. LiTa2NiSe5 crystallizes in the orthorhombic space group Pmnb (no. 62) with lattice parameters a = 3.50247(3) Å, b = 13.4053(4) Å, c = 15.7396(2) Å, and Z = 4, with an increase of the unit cell volume by 5.44(1)% compared with Ta2NiSe5. Significant rearrangement of the Ta-Ni-Se layers is observed, in particular a very significant relative displacement of the layers compared to the parent phase, similar to that which occurs under hydrostatic pressure. Neutron powder diffraction experiments and computational analysis confirm that Li occupies a distorted triangular prismatic site formed by Se atoms of adjacent Ta2NiSe5 layers with an average Li-Se bond length of 2.724(2) Å. Li-NMR experiments show a single Li environment at ambient temperature. Intercalation suppresses the distortion to monoclinic symmetry that occurs in Ta2NiSe5 at 328 K and that is believed to be driven by the formation of an excitonic insulating state. Magnetometry data show that the reduced phase has a smaller net diamagnetic susceptibility than Ta2NiSe5 due to the enhancement of the temperature-independent Pauli paramagnetism caused by the increased density of states at the Fermi level evident also from the calculations, consistent with the injection of electrons during intercalation and formation of a metallic phase

Deformation mechanisms in ionic liquid spun cellulose fibers

This is the final version of the article. Available from the publisher via the DOI in this record.The molecular deformation and crystal orientation of a range of next generation regenerated cellulose fibers, produced from an ionic liquid solvent spinning system, are correlated with macroscopic fiber properties. Fibers are drawn at the spinning stage to increase both molecular and crystal orientation in order to achieve a high tensile strength and Young’s modulus for potential use in engineering applications. Raman spectroscopy was utilized to quantify both molecular strain and orientation of fibers deformed in tension. X-ray diffraction was used to characterize crystal orientation of single fibers. These techniques are shown to provide complimentary information on the microstructure of the fibers. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm−1, emanating from the backbone structure of the cellulose polymer chains was followed under tensile deformation. It is shown that the shift rate of this band with respect to strain increases with the draw ratio of the fibers, indicative of an increase in the axial molecular alignment and subsequent deformation of the cellulose chains. A linear relationship between the Raman band shift rate and the modulus was established, indicating that the fibers possess a series aggregate structure of aligned crystalline and amorphous domains. Wide-angle X-ray diffraction data show that crystal orientation increases with an increase in the draw ratio, and a crystalline chain slip model was used to fit the change in orientation with fiber draw ratio. In addition to this a new model is proposed for a series aggregate structure that takes into better account the molecular deformation of the fibers. Using this model a prediction for the crystal modulus of a cellulose-II structure is made (83 GPa) which is shown to be in good agreement with other experimental approaches for its determination.The Engineering and Physical Sciences Research Council (EPSRC) is acknowledged for funding provided under Grant No. EP/L017679/1

Sugar alcohols-induced oxidative metabolism in cotton callus culture

Sugar alcohols (mannitol and sorbitol) may cause oxidative damage in plants if used in higher concentration. Our present experiment was undertaken to study physiological and metabolic responses in cotton (Gossypium hirsutum L.) callus against mannitol and sorbitol higher doses. Both markedly declined mean values of relative fresh weight growth rates with the increase in their concentration intensities. The overall protein and malonaldehyde (MDA) contents increased in the stressed-shocked cells. Also, the mean values of various antioxidants such as superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and calalase (CAT) quantitatively improved over their respective controls. As a whole, MDA contents were higher in magnitude than that of different antioxidant enzymes. Also values of relative increase in case of POD were higher as compared to SOD showing the ability of cotton callus culture to scavenge H2O2 produced as a result of the activity of SOD. Our results show that both agents caused greater damage to the membranous structure in comparison to less activation of the antioxidants. As a whole, the overall change regarding fresh weight growth rates was less after 14-day stress regime, while the mean values of the antioxidant enzymes activities were lower after the 28-day stress period. Such decrease conveys the message that less reactive oxygen species (ROS) might have been produced.Keywords: Antioxidants, callus culture, Gossypium hirsutum L., osmotic stress, sugar alcoholsAfrican Journal of Biotechnology Vol. 12(17), pp. 2191-220

Violet electroluminescence of AlInGaN-InGaN multiquantum-well light-emitting diodes: Quantum-confined stark effect and heating effect

Electroluminescence (EL) from AlInGaN-InGaN multiquantum-well violet light-emitting diodes is investigated as a function of forward bias. Two distinct regimes have been identified: 1) quantum-confined Stark effect at low and moderately high forward biases; 2) heating effect at high biases. In the different regimes, the low-temperature EL spectra exhibit different spectral features which are discussed in detail. © 2007 IEEE.published_or_final_versio

Quantum dissipation and broadening mechanisms due to electron-phonon interactions in self-formed InGaN quantum dots

Quantum dissipation and broadening mechanisms in Si-doped InGaN quantum dots are studied via the photoluminescence technique. It is found that the dissipative thermal bath that embeds the quantum dots plays an important role in the photon emission processes. Observed spontaneous emission spectra are modeled with the multimode Brownian oscillator model achieving an excellent agreement between experiment and theory for a wide temperature range. The dimensionless Huang-Rhys factor characterizing the strength of electron-LO-phonon coupling and damping constant accounting for the LO-phonon-bath interaction strength are found to be ∼0.2 and 200 cm-1, respectively, for the InGaN QDs. © 2006 American Institute of Physics.published_or_final_versio