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Thin steel plates exposed to combined ballistic impact and partially confined airblast loading
No full textPre-formed defects created by high-velocity impact have the potential to reduce the structural integrity of lightweight, flexible structures. This study evaluates the effect of complex, partially confined detonations on thin steel plates with realistic pre-formed defects. Target plates containing pre-cut circular holes with a diameter of 8.0 mm are compared to target plates exposed to an initial ballistic impact from 7.62 mm APM2 projectiles. The target plates were exposed to blast loading generated from detonating C-4 inside a steel tube. The stand-off distance was fixed and set equal to the tube radius, where the rear end of the tube was kept open. All blast tests were recorded with several pressure sensors, synchronized with two high-speed cameras monitoring the dynamic response of the target plates. This allowed for a reliable experimental procedure, serving as a benchmark for different numerical methods. For similar loading conditions, the target plates containing initial ballistic impact showed a reduced fracture resistance during blast loading compared to the target plates with pre-cut circular holes. Two different numerical approaches were tested and compared, i.e., a purely Lagrangian particle-based approach and a fully coupled simulation approach using an ALE description of the blast domain. The ALE simulations were found to underestimate the structural response, while the particle-based approach overestimated the structural response
Global sensitivity analysis and optimal design of heat recovery ventilation for zero emission buildings
No full textEnergy-efficient building services are necessary to realise zero-emission buildings while maintaining adequate indoor environmental quality. As the share of ventilation heating needs grow in well-insulated and airtight buildings, heat recovery in mechanical ventilation systems is increasingly common. Ventilation heat recovery is one of the most efficient and viable means to reduce ventilation heat losses and save energy. Highly efficient heat exchangers are being developed or applied to maximise the energy-saving potential of heat recovery ventilation. Nevertheless, the effects of practical operating conditions and the constraints of heat recovery – such as variations in ventilation rates, frost protection, and the prevention of an overheated air supply over a long-term period, which may significantly influence realistic recovery rates – have been less considered in efforts to maximise the energy savings. It is unclear which design parameters for heat recovery devices have the greatest effect on the annual energy savings from ventilation.
This study proposes annual efficiency and annual net energy saving models for heat recovery ventilation that consider ventilation rate variations, the longitudinal heat conduction effect and operating controls. We use a global sensitivity analysis to quantify the contributions of various design input parameters to the variation in annual recovery efficiency and annual net energy savings. We identify the most influential parameters and their significant interaction effects for the annual energy performance of heat recovery ventilation. More attention should be paid to these most influential parameters during the design process. Furthermore, the optimal designs for rotary heat exchangers (as identified by a pattern-search optimisation algorithm) can improve annual net energy savings in demand-controlled ventilation by 33–48%, depending on the building areas. In combination with the reference year analysis presented in this study, heat recovery and demand-controlled ventilation can help to meet the need for highly efficient ventilation systems and zero-emission buildings
Hyaluronic acid-based hydrogels: drug diffusion investigated by HR-MAS NMR and release kinetics
No full textHydrogels based on hyaluronic acid (HA) and agarose–carbomer (AC) units have been prepared and explored as drug delivery systems. The complex architecture of the polymer network, such as mesh size, HA molecular weight and drug-polymer non-covalent interactions across the 3D polymer matrix, strongly influence the release capability/profile of these materials. In this study, High-Resolution Magic Angle Spinning (HR-MAS) NMR Spectroscopy has been used to investigate the transport behaviour of two different drugs, such as ethosuximide (neutral molecule) and sodium salicylate (net negative charge) within the AC and AC-HA hydrogel networks prepared with different mesh sizes. Analysis of the experimental data provides evidence of superdiffusive motion for all formulations containing sodium salicylate, while ethosuximide molecules undergo unrestricted diffusion within the gel matrix. We further speculate that the superdiffusive motion observed at the nanoscale can be responsible for the faster release of sodium salicylate from all hydrogel formulations
The more experienced, the better prepared? New evidence on the relation between teachers’ experience and their readiness for online teaching and learning
No full textIn the present study, we tested the common assumption that teachers with more experience consider themselves better prepared for online teaching and learning (OTL). Utilizing the data from a survey of 366 higher-education teachers from Portugal at the beginning of the COVID-19 pandemic in 2020, we performed structural equation modeling to quantify the experience-readiness relationship. The survey contained an assessment of teachers' OTL readiness which was measured by their perceptions of the institutional support, online teaching presence, and TPACK self-efficacy. In contrast to the linearity assumption “the more experienced, the better prepared”, we found robust evidence for a curvilinear relationship. Teachers’ readiness for OTL increased first and then decreased with more experience—this applied especially to the self-efficacy dimension of readiness. Further analyses suggested that the experience-readiness relationship does not only exist at the level of aggregated constructs but also at the level of indicators, that is, specific areas of knowledge, teaching, and support. We argue that both novice and experienced teachers in higher education could benefit from experience-appropriate, pedagogical, and content-related support programs for OTL
What Characterizes the Productive Morphosyntax of Norwegian Children with Developmental Language Disorder?
No full textAbstract
Little is known about the productive morphosyntax of Norwegian children with developmental language disorder (DLD). The current study examined morphosyntax in Norwegian-speaking children with DLD ( n =19) and a control group that was pairwise matched for age, gender, and intelligence quotient (IQ; n = 19). The children’s sentence repetitions were studied through the lens of Processability Theory. The group differences were largest for grammatical structures at the latest developmental stage of the processability hierarchy. The Norwegian subordinate clause word order, belonging to the latest stage of the processability hierarchy, stood out as particularly challenging for children with DLD. Only 2 children with DLD but 16 children in the control group produced a subordinate clause with subordinate clause word order. Categorization of children’s errors revealed that children with DLD made more errors of all types (addition, omission, substitution, inflection and word order) but especially errors of omission and inflection
Brazilian undergraduate nursing students’ critical thinking need to be increased: a cross-sectional study
No full textObjectives: to map Brazilian undergraduate nursing students’ critical thinking level and investigate the correlation between selected sociodemographic data and critical thinking domains.
Methods: in this descriptive cross-sectional study, participants’ (N=89) critical thinking was assessed using the Health Science Reasoning Test. Correlation between critical thinking domains and sociodemographic data was assessed using the Pearson correlation coefficient.
Results: the overall results showed a moderate level of participants’ critical thinking (mean = 70.7; standard deviation 5.7). A poor performance was identified in 5 of the 8 critical thinking domains. A significant positive correlation was found between education period and critical thinking (p<.001).
Conclusions: poor level in students critical thinking domains may lead to negative consequences for their learning outcomes. Further studies should be carried out to confirm our results, in addition to investigation of teaching methods that encourage and ensure the development of students’ critical thinking skills during nursing education
Salmon lice (Lepeophtheirus salmonis) in the stomach contents of lumpfish (Cyclopterus lumpus) sampled from Norwegian fish farms: Relationship between lice grazing and operational conditions
No full textCleaner fish are commonly used as a control measure against salmon lice infestations in salmonid farms. Lumpfish (Cyclopterus lumpus) is the most common cleaner fish species used in Norwegian farms. However, little is known about how different operational, including environmental, conditions affect the salmon lice grazing efficacy by lumpfish. In this paper, we analyse salmon lice (Lepeophtheirus salmonis) in the stomach contents of a large sample of more than 20,000 lumpfish from 80 different Norwegian farms. We investigate the proportion of lumpfish with salmon lice and the mean number of salmon lice in the stomach contents of the lumpfish. We further explore how the salmon lice contents vary with different factors like lumpfish weight, weight of salmonids, salmon lice abundance in the cage, cloud cover, and sea temperature. We find that 3.1% of the 24,693 lumpfish contained salmon lice. Most of the lumpfish with salmon lice in their stomach contents contained few (one or two) lice, while there were a few lumpfish which contained many salmon lice. We find more salmon lice in the stomach contents with increasing abundance of salmon lice in the sea cage, lower weight of the salmonids, and in clear weather. Interestingly, for the relationship between lumpfish weight and salmon lice in the stomach contents, we find increased salmon lice grazing from ca. 5 g up to an optimal weight of ca. 40 g, and then a decrease from 40 g. Surprisingly, we find no relationship between sea temperature and salmon lice per lumpfish. We find more salmon lice in the stomach contents of the lumpfish with comparatively high condition. By studying the factors associated with most efficient salmon lice grazing, our paper contributes to understanding how different operational factors affect salmon lice grazing by lumpfish. For controllable factors, the results thus contribute to guiding the best practice for use of lumpfish as a salmon lice control measure
Driven precast concrete geothermal energy piles: Current state of knowledge
No full textGeothermal energy piles are increasingly luring attention in the construction industry as a cost-effective and environmental friendly solution for heating and cooling buildings. Energy piles are used as the primary unit in the ground source heat pump systems, which exchange heat with the ground. Energy piles are generally categorized into driven (displacement) and cast-in-place (non-displacement) piles. The present paper aims to review the available methods of design and construction of driven precast concrete energy pile foundations and provides a clear understanding of its construction challenges. Additionally, precast and cast-in-place energy pile foundations are compared. This paper found that precast concrete-driven energy pile foundations are a competitive alternative to cast-in-place energy piles. Driven concrete energy piles have higher quality control and quality assurance in the construction process; they have an easier, faster, and more reliable installation. Several other advantages and limitations related to the technical, economical, and environmental aspects of such piles are discussed in detail. The driven precast concrete foundations have a large worldwide market; however, there is a lack of guidelines, design standards, and experience for using such foundations as energy piles
Vehicle assisted bridge damage assessment using probabilistic deep learning
No full textVehicle assisted monitoring has shown promising potential for the condition assessment of existing bridges in a road network, by removing practical complications faced in traditional Structural health monitoring (SHM) methods such as traffic interruption and dense deployment of sensors. However, the combination of different measurement sources during vehicle assisted monitoring has not yet been fully explored. This paper aims to evaluate the potential benefit of considering multiple measured responses from various sources, including fixed sensors on the bridge and on-board vehicle sensors. To this end, this paper proposes a Probabilistic Deep Neural Network, a stochastic data-driven framework for damage assessment. This framework enables the combination of vehicle and bridge responses to extract damage sensitive features for the classification of different damage states. In addition, the proposed method estimates the uncertainty of its predictions, providing an indication of the reliability of the result. The proposed method is validated using two numerical based case studies while considering realistic operational conditions, which include temperature oscillations, additional traffic, and measurement noise. The results from this study indicate that combining multiple sensor information results in lower uncertainties in damage detection and localisation. The results also suggest that the proposed method is robust in handling measurement noise and varying environmental conditions
The Nehari problem for the Paley--Wiener space of a disc
No full textThere is a bounded Hankel operator on the Paley–Wiener space of a disc in R2 which does not arise from a bounded symbol