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On the variation operator for the Ornstein–Uhlenbeck semigroup in dimension one
Get PDFConsider the variation seminorm of the Ornstein–Uhlenbeck semigroup Ht in dimension one, taken with respect to t. We show that this seminorm defines an operator of weak type (1,\ua01) for the relevant Gaussian measure. The analogous Lp estimates for 1 < p< ∞ were already known
Evaluating the Trade-offs of Text-based Diversity in Test Prioritisation
No full textDiversity-based techniques (DBT) have been cost-effective by prioritizing the most dissimilar test cases to detect faults at earlier stages of test execution. Diversity is measured on test specifications to convey how different test cases are from one another. However, there is little research on the trade-off of diversity measures based on different types of text-based specification (lexicographical or semantics). Particularly because the text content in test scripts vary widely from unit (e.g., code) to system-level (e.g., natural language). This paper compares and evaluates the cost-effectiveness in coverage and failures of different text-based diversity measures for different levels of tests. We perform an experiment on the test suites of 7 open source projects on the unit level, and 2 industry projects on the integration and system level. Our results show that test suites prioritised using semantic-based diversity measures causes a small improvement in requirements coverage, as opposed to lexical diversity that showed less coverage than random for system-level artefacts. In contrast, using lexical-based measures such as Jaccard or Levenshtein to prioritise code artefacts yield better failure coverage across all levels of tests. We summarise our findings into a list of recommendations for using semantic or lexical diversity on different levels of testing
Quantifying timber illegality risk in the Brazilian forest frontier
Get PDFIllegal logging remains widespread across the tropics, leading to extensive forest degradation and trade in illegal timber products. By adapting environmentally extended input–output modelling to timber originating from Brazilian native forests, we demonstrate how distinct illegality risks can be mapped and quantified at species-level across the supply chain. We focus on high-value ip\uea hardwood from the Amazon state of Par\ue1, a leading producer of timber and contested forest frontier. Data on logging permits and state- and national-level Document of Forest Origin licences are used to estimate illegality risks due to missing or invalid logging permits, overstated ip\uea yields or discrepancies resulting from missing inflows of legal timber. We find that less than a quarter of all ip\uea entering supply chains between 2009 and 2019 is risk-free and highlight diversified strategies for the laundering of illegal timber across geographies. While legality does not ensure sustainability, this information can be leveraged to this end by supporting improved implementation and enforcement of forest regulations
Arabinoxylan source and xylanase specificity influence the production of oligosaccharides with prebiotic potential
Get PDFCereal arabinoxylans (AXs) are complex polysaccharides in terms of their pattern of arabinose and ferulic acid substitutions, which influence their properties in structural and nutritional applications. We have evaluated the influence of the molecular structure of three AXs from wheat and rye with distinct substitutions on the activity of β-xylanases from different glycosyl hydrolase families (GH 5_34, 8, 10 and 11). The arabinose and ferulic acid substitutions influence the accessibility of the xylanases, resulting in specific profiles of arabinoxylan-oligosaccharides (AXOS). The GH10 xylanase from Aspergillus aculeatus (AcXyn10A) and GH11 from Thermomyces lanuginosus (TlXyn11) showed the highest activity, producing larger amounts of small oligosaccharides in shorter time. The GH8 xylanase from Bacillus sp. (BXyn8) produced linear xylooligosaccharides and was most restricted by arabinose substitution, whereas GH5_34 from Gonapodya prolifera (GpXyn5_34) required arabinose substitution and produced longer (A)XOS substituted on the reducing end. The complementary substrate specificity of BXyn8 and GpXyn5_34 revealed how arabinoses were distributed along the xylan backbones. This study demonstrates that AX source and xylanase specificity influence the production of oligosaccharides with specific structures, which in turn impacts the growth of specific bacteria (Bacteroides ovatus and Bifidobacterium adolescentis) and the production of beneficial metabolites (short-chain fatty acids)
Wetland Mapping in Great Lakes Using Sentinel-1/2 Time-Series Imagery and DEM Data in Google Earth Engine
Get PDFThe Great Lakes (GL) wetlands support a variety of rare and endangered animal and plant species. Thus, wetlands in this region should be mapped and monitored using advanced and reliable techniques. In this study, a wetland map of the GL was produced using Sentinel-1/2 datasets within the Google Earth Engine (GEE) cloud computing platform. To this end, an object-based supervised machine learning (ML) classification workflow is proposed. The proposed method contains two main classification steps. In the first step, several non-wetland classes (e.g., Barren, Cropland, and Open Water), which are more distinguishable using radar and optical Remote Sensing (RS) observations, were identified and masked using a trained Random Forest (RF) model. In the second step, wetland classes, including Fen, Bog, Swamp, and Marsh, along with two non-wetland classes of Forest and Grassland/Shrubland were identified. Using the proposed method, the GL were classified with an overall accuracy of 93.6% and a Kappa coefficient of 0.90. Additionally, the results showed that the proposed method was able to classify the wetland classes with an overall accuracy of 87% and a Kappa coefficient of 0.91. Non-wetland classes were also identified more accurately than wetlands (overall accuracy = 96.62% and Kappa coefficient = 0.95)
Architecture landscape
Get PDFThe network architecture evolution journey will carry on in the years ahead, driving a large scale adoption of 5th Generation (5G) and 5G-Advanced use cases with significantly decreased deployment and operational costs, and enabling new and innovative use-case-driven solutions towards 6th Generation (6G) with higher economic and societal values. The goal of this chapter, thus, is to present the envisioned societal impact, use cases and the End-to-End (E2E) 6G architecture. The E2E 6G architecture includes summarization of the various technical enablers as well as the system and functional views of the architecture
Explosions in urban environments: Modelling of gas explosions and risk of premature shear failure in reinforced concrete structures
Get PDFThe risk for accidental gas explosions in urban environments has increased in Sweden in recent years. This is due to densification of existing urban centres and the rise of vehicles powered by alternative fuels. Because of this, blast-resistant design of reinforced concrete (RC) structures may eventually become a common aspect of urban development and structural engineering. This thesis aims at expanding the knowledge concerning explosion and blast loads in urban environments and the response of RC structures subjected to it. Two key research areas were identified. The first one deals with the strength of vapour cloud explosions (VCEs) on urban roads. The strength of the blast source is a necessary input to predict the blast load generated by VCEs. However, there is much subjectivity and inconsistency today in the determination of the explosion strength, particularly for the conditions on urban roads. This work used computational fluid dynamics (CFD) calculations in combination with the principles of factorial design to determine the expected strength for several explosion scenarios on urban roads and identify the most significant parameters affecting the resulting strength. For the studied scenarios, the explosion strength varied approximately from 2\ua0kPa to 100\ua0kPa. Moreover, the number of vehicles in the transversal direction (i.e., vehicles standing side by side) was found to have the most significant effect on the explosion pressure.The other area is concerned with the uncertainties related to the failure modes of blast-loaded RC one-way slabs. The motivation behind this research area is the need to prevent brittle shear failure in blast-loaded RC elements. The Monte Carlo method was used to determine the probability of premature shear failure of the blast-loaded slabs considering the uncertainties associated with the materials, geometry, and resistance models. The slabs were initially designed to have a balanced failure (i.e., the resistance to shear and bending failure are theoretically equal). Bending failure was found to be the expected failure mode for the studied cases. However, the likelihood of shear failure (particularly for slabs without stirrups) may still be considered relatively high, depending on the risk tolerability of a given design. Thus, an additional partial factor to enhance the confidence level regarding the preferred failure mode was put forward
A fluid flow model for the pressure loss through perforated plates
No full textA fluid flow through a perforated plate is a common problem in a wide variety of practical applications in thermal, mechanical, chemical, civil, nuclear, ocean and aerospace engineering. In this paper, we proposed a novel fluid flow model for the pressure loss through plates with circular perforations in both laminar and turbulent flows. The design of this model is based on the recent measurements conducted at ONERA in the framework of the on-going European Union H2020 INVENTOR project, as well as an existing model for laminar flows. The new model is then validated against existing numerical simulations in the laminar regime and experiments in the turbulent regime. Overall, the predictions given by the new model agree well with the numerical simulations and experiments, and are superior to other models in the literature. This is significant, considering that the present model is much simpler than these previous models. To demonstrate the application of the new model in numerical simulations, two-dimensional channel flows are simulated using Reynolds-averaged Navier-Stokes (RANS) equations with the new model as a pressure-drop source term added to the momentum equations. Results show that the RANS predictions agree very well with the present model predictions
FAN STAGE DESIGN AND PERFORMANCE OPTIMIZATION FOR LOW SPECIFIC THRUST TURBOFANS
No full textIn modern turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. An accurate description of the interdependencies of relevant performance and design attributes of the fan stage alone - such as efficiency, surge margin, fan-face Mach number, stage loading, flow coefficient and aspect ratio - are therefore necessary to estimate system level objectives such as mission fuel burn and direct operating cost with enough confidence during the conceptual design phase. The contribution of this study is to apply a parametric optimization approach to conceptual design of fan stages for low specific thrust turbofans based on the streamline curvature method. Trade-offs between fan stage attributes for Pareto-optimal solutions are modelled by training a Kriging surrogate model on the results from the parametric optimization. The trends predicted by the resulting surrogate model are analyzed both quantitatively and qualitatively. Most of the trends could be justified with some degree of physical reasoning or comparison with common guidelines from the literature. Trends of stage efficiency with Mach number and stage loading may indicate that shock losses have a larger impact on stage efficiency for designs with low stage loading compared to designs with high stage loading. Means to reduce the strength of the passage shock wave, such as blade sweep, may therefore be of more importance as stage loading is reduced