This paper investigates the three-dimensional (3D) scattering of guided waves by a partly through-thickness, flat bottomed cavity with an irregular shape, in an isotropic plate. Both the scattered ...field and the standing field in the thinner plate beneath the cavity are decomposed on the basis of Lamb and SH waves, by including propagating and non-propagating modes. The amplitude of the modes is calculated by writing the nullity of the total stress at the boundary of the cavity, and the continuity of the stress and displacement vectors under the cavity. In the boundary conditions, the functions depend on the through-thickness coordinate, z, but contrary to the case where the cavity has a circular shape, they also depend on the angular coordinate θ. This is dealt with by projecting the z-dependent functions onto the basis of the guided wave displacements vectors, and by expanding the θ-dependent functions in Fourier series. Example results are presented for the scattering of the S0, SH0 and A0 modes by elliptical cavities of varying depth, and the scattering of the S0 mode by a cavity with an arbitrary shape. Results obtained with this model are compared with ones obtained with the finite element (FE) method, showing very good agreement.
► We study the scattering of guided waves by partly through-thickness, flat-bottomed cavities with irregular shapes in plates. ► We develop an analytical model and compare it to a finite element model. ► We present 2 examples: partly through-thickness cavities with elliptical and arbitrary shape. ► Results from the analytical and the finite element models show very good agreement.
Advances in the UK Toward NDE 4.0 Brierley, N.; Smith, R. A.; Turner, N. ...
Research in nondestructive evaluation,
11/2020, Letnik:
31, Številka:
5-6
Journal Article
Recenzirano
Odprti dostop
In the UK, the NDE community is making a coordinated effort to underpin and enable the full benefits of the large-scale trend toward comprehensive digitalization and automation of industrial ...processes and assets, frequently referred to as "Industry 4.0". Certain facets of what is now considered to be NDE 4.0 have been the subject of research for some time and have already gained industrial traction, while others are quite new, with unexplored potential and pitfalls. However, in these areas there is scope for learning from progress in fields outside of, but related to, NDE such as dimensional metrology. This paper reviews progress to date based on UK activities, considers some planned and potential research tasks in this domain, and highlights the major challenges the NDE community must tackle. In particular, as interoperability and data reuse are key features of Industry 4.0 practices, international and cross-domain efforts on data format standardization are needed. It is clear that, without the NDE community stepping up to the challenge, much of Industry 4.0 cannot be realized; yet if the NDE 4.0 vision is implemented comprehensively, NDE has the potential to become more capable, more valuable, and therefore more highly valued.
In this paper we describe hillslope‐scale, rainfall‐simulation experiments on karst shrublands dominated by Ashe juniper. These simulations, designed to mimic flood‐producing rainfall events, were ...carried out at two sites separated by 206 km within the Edwards Plateau of Central Texas. Five hillslope plots were instrumented—two shrub‐covered (canopy) plots and three intercanopy plots measuring 12–14 m in length. We repeated the experiments on the canopy plots after removing the shrubs. For the canopy plots, both before and after shrub removal, 50% or more of the water applied exited the plots as subsurface stormflow and no overland flow occurred. For the intercanopy plots, subsurface stormflow amounted to less than 10% of the water applied and overland flow was between 10 and 50%. These experiments demonstrate the importance of subsurface stormflow in semiarid karst shrublands during flood events, and more generally highlight the fact that subsurface stormflow is important in some semiarid landscapes.
We demonstrate the generation of Bessel beams using an acousto-optic array based on a liquid filled cavity surrounded by a cylindrical multi-element ultrasound transducer array. Conversion of a ...Gaussian laser mode into a Bessel beam with tunable order and position is shown. Also higher-order Bessel beams up to the fourth order are successfully generated with experimental results very closely matching simulations.
The rugged Hill Country of Central Texas is part of the extensive Edwards Plateau region. Significant portions of the Texas Hill Country overlie the Glen Rose Formation, which is characterized by a ...stair‐step topography formed by the weathering of interbedded carbonate materials having different weathering susceptibilities. This process has sculpted the strata into a series of “risers” and “treads” that mimic stairways. In this paper, we document the soil hydrology within the riser–tread catena. Our results are counterintuitive in that we find the highest infiltration and deepest soils on the steep riser slopes. In addition, we find that the riser subsoils are saturated or very wet for extended periods. On the basis of these findings, we suggest that (1) groundwater recharge on these hillslopes is minimal and occurs only in highly fractured zones; (2) the water‐holding capacity of the subsoils is sufficient for supporting the woody vegetation; and (3) runoff generation occurs as a combination of surface and subsurface flow, with the risers serving as sinks or recharge zones and the treads as source areas.
Rangelands have undergone—and continue to undergo—rapid change in response to changing land use and climate. A research priority in the emerging science of ecohydrology is an improved understanding ...of the implications of vegetation change for the water cycle. This paper describes some of the interactions between vegetation and water on rangelands and poses 3 questions that represent high-priority, emerging issues: 1) How do changes in woody plants affect water yield? 2) What are the ecohydrological consequences of invasion by exotic plants? 3) What ecohydrological feedbacks play a role in rangeland degradation processes? To effectively address these questions, we must expand our knowledge of hydrological connectivity and how it changes with scale, accurately identify “hydrologically sensitive” areas on the landscape, carry out detailed studies to learn where plants are accessing water, and investigate feedback loops between vegetation and the water cycle.
Rangelands cover a large portion of the earth's land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water ...supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using cesium-137 and lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall–runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.
Savanna ecosystems across the globe have experienced substantial changes in their vegetation composition. These changes can be attributed to three main processes: (1) encroachment, which refers to ...the expansion of woody plants into open areas, (2) thicketization, which is characterized by the growth of sub-canopy woody plants, and (3) disturbance, defined here as the removal of woodland cover due to both natural forces and human activities. In this study, we utilized Landsat surface reflectance data and Sentinel-1 SAR data to track the progression of these process from 1996 to 2022 in the significantly modified Post Oak Savannah ecoregion of Central Texas. Our methodology employs an ensemble classification algorithm, which combines the results of multiple models, to develop a more precise predictive model, along with the spectral–temporal segmentation algorithm LandTrendr in Google Engine (GEE). Our ensemble classification algorithms demonstrated high overall accuracies of 94.3 and 96.5% for 1996 and 2022, respectively, while our LandTrendr vegetation map exhibited an overall accuracy of 80.4%. The findings of our study reveal that 9.7% of the overall area experienced encroachment of woody plants into open area, while an additional 6.8% of the overall area has transitioned into a thicketized state due to the growth of sub-canopy woody plants. Furthermore, 5.7% of the overall area encountered woodland disturbance leading to open areas. Our findings suggest that these processes advanced unevenly throughout the region, resulting in the coexistence of three prominent plant communities that appear to have long-term stability: a dense deciduous shrubland in the southern region, as well as a thicketized oak woodland and open area mosaic in the central and northern regions. The successional divergence observed in these plant communities attests to the substantial influence of human modification on the landscape. This study demonstrates the potential of integrating passive optical multispectral data and active SAR data to accurately map large-scale ecological processes.
Existing standards for the characterization of the size, morphology, chemistry, and distribution of inclusions in steels using different techniques are briefly reviewed in this work. Strengths and ...shortfalls of different methods are discussed, and a combination of different criteria is used to quantitatively characterize the inclusions in a continuously cast high-carbon steel. It is shown that the main elements in the inclusions for the studied steel were Mn, S, Ti, Al, and oxygen and that alongside MnS and some Al
2
O
3
inclusions many non-metallic inclusions appeared in complex forms, consisting of silicates, sulfides, and different types of oxides. Duplex inclusions, mainly cores of Al
2
O
3
, or SiO
2
surrounded by MnS were the most common complex multiphase inclusions in this steel. An industrial approach was used to classify the inclusions into thirteen different oxide types. Based upon this approach, data are presented according to the chemistry of inclusions using diagrams featuring different quantitative parameters. Furthermore, it is shown that the number of oxides per unit area and the size of oxides, respectively, decreased and increased with increasing distance from the surface of the bloom which had solidified at the highest cooling rate.
The related phenomena of degradation and woody plant encroachment have transformed huge tracts of rangelands. Woody encroachment is assumed to reduce groundwater recharge and streamflow. We analyzed ...the long‐term (85 years) trends of four major river basins in the Edwards Plateau region of Texas. This region, in which springs are abundant because of the karst geology, has undergone degradation and woody encroachment. We found that, contrary to widespread perceptions, streamflows have not been declining. The contribution of baseflow has doubled—even though woody cover has expanded and rainfall amounts have remained constant. We attribute this increase in springflow to a landscape recovery that has taken place concurrently with woody expansion—a recovery brought about by lower grazing pressure. Our results indicate that for drylands where the geology supports springs, it is degradation and not woody encroachment that leads to regional‐scale declines in groundwater recharge and streamflows.
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