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Acoustic emission (AE) testing and Lamb wave inspection techniques have been widely used in non-destructive testing and structural health monitoring. For thin plates, the AEs arising from structural defect development (e.g., fatigue crack propagation) propagate as Lamb waves, and Lamb wave modes can be used to provide important information about the growth and localisation of defects. However, few sensors can be used to achieve the in situ wavenumber–frequency modal decomposition of AEs. This study explores the ability of a new multi-element piezoelectric sensor array to decompose AEs excited by pencil lead breaks (PLBs) on a thin isotropic plate. In this study, AEs were generated by out-of-plane (transverse) and in-plane (longitudinal) PLBs applied at the edge of the plate, and waveforms were recorded by both the new sensor array and a commercial AE sensor. Finite element analysis (FEA) simulations of PLBs were also conducted and the results were compared with the experimental results. To identify the wave modes present, the longitudinal and transverse PLB test results recorded by the new sensor array at five different plate locations were compared with FEA simulations using the same arrangement. Two-dimensional fast Fourier Transforms were then applied to the AE wavefields. It was found that the AE modal composition was dependent on the orientation of the PLB direction. The results suggest that this new sensor array can be used to identify the AE wave modes excited by PLBs in both in-plane and out-of-plane directions.

The aim of this paper is to discuss the effect of the sensor on the acoustic emission (AE) signature and to develop a methodology to reduce the sensor effect. Pencil leads are broken on PMMA plates at different source–sensor distances, and the resulting waves are detected with different sensors. Several transducers, commonly used for acoustic emission measurements, are compared with regard to their ability to reproduce the characteristic shapes of plate waves. Their consequences for AE descriptors are discussed. Their different responses show why similar test specimens and test conditions can yield disparate results. This sensor effect will furthermore make the classification of different AE sources more difficult. In this context, a specific procedure is proposed to reduce the sensor effect and to propose an efficient selection of descriptors for data merging. Principal Component Analysis has demonstrated that using the Z-score normalized descriptor data in conjunction with the Krustal–Wallis test and identifying the outliers can help reduce the sensor effect. This procedure leads to the selection of a common descriptor set with the same distribution for all sensors. These descriptors can be merged to create a library. This result opens up new outlooks for the generalization of acoustic emission signature libraries. This aspect is a key point for the development of a database for machine learning.

The failure mode of the nuclear reactor main pipeline is often the first break and then leakage, i.e., Leak-Before-Break (LBB). If the LBB analysis technique of the pipeline is used in the design, the double-end shear fracture accident of the pipeline can be avoided. In this paper, it is assumed that an annular penetration crack already exists in the pipeline, and the tip-opening displacement of the crack and the leakage rate of the pipeline under high pressure are calculated by using LBB theoretical analysis. Then, according to the assumed conditions, the LBB test design of the pipeline under high pressure is carried out, and the crack tip opening displacement δ and the leakage rate Q of the pipeline under high pressure are measured through the experiments.

Objective The aim of this prospective study is to comparatively assess the tear film, meibomian gland (MG), cornea and anterior chamber parameters and also subjective ocular complaints in patients with polycystic ovary syndrome (PCOS) and healthy control subjects. Materials and methods We included 53 eyes of the 53 patients diagnosed with PCOS and 57 eyes of the 57 healthy control subjects (who are non-pregnant, none of the following clinical findings of male pattern hair loss, hirsutism or acne and with regular menstrual cycles, who have no laboratory findings in her medical history that indicate hyperandrogenism, and who have ovaries that appear to be normal ultrasonographically. All subjects were referred to the masked ophthalmologist by the obstetrician and gynecologist. Participants underwent evaluation of the non-invasive tear film break-up time test (NI-BUT); loss of MGs by non-contact meibography , evaluation of cornea and anterior chamber parameters, and evaluation of subjective ocular complaints using the ocular surface disease index (OSDI ) . Results The mean age of PCOS group and controls was 25.08 ± 4.88 and 25.44 ± 5.00 years, respectively. There was no statistically significant difference between the PCOS and control groups in terms of age (p = 0.732). Mean non-invasive first tear film breakup times (NIF-BUT) values of PCOS group and controls were 6.15 ± 4.99 and 10.48 ± 5.81 s, and mean non-invasive average tear film breakup times (NIAvg–BUT) values of PCOS group and controls were 8.48 ± 4.27 and 11.94 ± 4.64 s, respectively; both cases refer to a significant difference between the groups (p = 0.000). In PCOS group, loss of MG in the upper lids was 40.21%, in the lower lids was 53.45%; on the other hand, in control group 15.76% and 21.47%, respectively; both cases refer to a significant difference between the groups (p = 0.000). The number of patients with abnormal OSDI scores (scores ≥ 13 points) was significantly higher in PCOS group (54.7%) than in controls (19.3%) (p = 0.000). Anterior chamber volume (ACV) measured by the topography device in PCOS group was significantly lower (156.5 and 167.4) (p = 0.024). Conclusion Findings of this study indicated that tear film stability impaired in patients with PCOS and that this impairment was accompanied by the loss of MG, which play a key role in tear film stability.

A shellular is a micro-architectured material, composed of a continuous smooth-curved thin shell in the form of a triply periodic minimal surface. Thanks to the unique geometry, a shellular can support external load by co-planar stresses, unlike microlattice, nanolattice, and mechanical metamaterial. That is, the shellular is the only stretching-dominated material with the highest strength at a density of less than 10 −2  g/cc. Therefore, it is expected to support internal pressure, too, by the bi-axial tensile stresses like a balloon. For more than 300 years, spherical and cylindrical vessels have been viable yet compromised options for storing pressurized gases. However, emerging green mobility necessitates a safer and more spatially conformable storage solution for hydrogen than spherical and cylindrical vessels these conventional vessels. In this study, we propose to use the shellular as a pressure vessel. Due to the distinct topological nature – periodic micro-cells constituting the triply periodic minimal surface, the alternative pressure vessel can be tailored individually for spatial requirements while ensuring safety with leak-before-break . For a given constituent material and prescribed pressure, the achievable internal volume-per-total weight of a P -surfaced, cold-stretched, double-chambered shellular vessel with a number of cells more than 15 × 15 × 15 can exceed the practical upper bound of both spherical and cylindrical vessels. For the applications, a thin shell with the large surface area of this micro-architecture is ideal for interfacial transfer of heat or mass between its two sub-volumes under internal pressure. A shellular is a micro-architectured material, composed of a continuous smooth-curved thin shell in the form of a triply periodic minimal surface. Here, authors propose schellular designs applied to pressure vessels and demonstrate its competitive practical features against spherical and cylindrical vessels.

We derive a structural break test for extremal dependence in β-mixing, possibly high-dimensional random vectors with either asymptotically dependent or asymptotically independent components. Existing tests require serially independent observations with asymptotically dependent components. To avoid estimating a long-run variance, we use self-normalization, which obviates the need to estimate the coefficient of tail dependence when components are asymptotically independent. Simulations show favourable empirical size and power of the test, which we apply to S&P 500 and DAX log-returns. We find evidence for one break in the coefficient of tail dependence for the upper and lower joint tail at the beginning of the 2007–08 financial crisis, leading to more extremal co-movement.

Given the increasing investment by Belt and Road Initiative (BRI) participants in the renewable energy industry, it is imperative to ascertain how much this investment contributes to economic growth. The objective of this study is to ascertain the extent to which renewable energy contributes to economic growth within the Belt and Road Initiative compared to non-renewable energy sources. Prior studies have yet to incorporate oil prices as a variable in the production function, among other output aspects. This study integrates the inclusion of real oil prices as a variable within the production function alongside capital, labor, renewable energy consumption, and non-renewable energy consumption. A cohort including 49 Belt and Road Initiative participants was formed, encompassing data from 1990 to 2019. The data has undergone an initial examination to assess cross-sectional dependence, slope heterogeneity, and structural break(s), and are verified. Hence, third-generation panel data analysis has been utilized. The continuously updated fully modified estimator and continuously updated biased corrected estimator provide evidence supporting the notion that renewable energy plays a substantial role in fostering economic growth within nations participating in the Belt and Road Initiative. Furthermore, this contribution is found to be more pronounced when compared to the impact of non-renewable energy sources. The study's findings inform policy recommendations at both the BRI and national level.

This study investigates the existence of long-run relationship between CO 2 emissions, economic growth, energy use, and urbanization in Saudi Arabia over the period 1971–2014. The autoregressive distributed lag (ARDL) approach with structural breaks, where structural breaks are identified with the recently impulse saturation break tests, is applied to conduct the analysis. The bounds test result supports the existence of long-run relationship among the variables. The existence of environmental Kuznets curve (EKC) hypothesis has also been tested. The results reveal the non-validity of the EKC hypothesis for Saudi Arabia as the relationship between GDP and pollution is positive in both the short and the long run. Moreover, energy use increases pollution both in short and long run in the country. On the contrary, the results show a negative and significant impact of urbanization on carbon emissions in Saudi Arabia, which means that urban development is not an obstacle to the improvement of environmental quality. Consequently, policy-makers in Saudi Arabia should consider the efficiency enhancement, frugality in energy consumption, and especially increase the share of renewable energies in the total energy mix.

The growth stimulating effect of energy has been long established in economic literature. Consequently, researchers and policy makers are trying to identify socio-economic determinants of energy consumption in both developed and developing countries to conserve energy. In the present study, we attempt to examine the non-linear and asymmetric effect of human capital and income disparity on energy demand in India over the period 1970–2014. The findings propose long-run co-integrating relationship between human capital, income inequality, and energy demand in the presence of asymmetric framework. It is found that increased level of human capital results in energy conservation as it decreases the energy demand, and higher income gap also results in lower energy demand as poor section may have restricted access to energy sources. Finally, the asymmetric causality test results reveal that only positive shock in income inequality tends to cause energy demand. From policy stand point, it can be recommended that government policies should be designed and implemented towards improvements in human capital to achieve sustainable economic growth in India since human capital found to be a significant component in energy conservation.