NORA - Norwegian Open Research Archives
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    Driven precast concrete geothermal energy piles: Current state of knowledge

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    Geothermal 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

    What Characterizes the Productive Morphosyntax of Norwegian Children with Developmental Language Disorder?

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    Abstract 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

    Global Asymptotic Tracking for Marine Vehicles using Adaptive Hybrid Feedback

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    This paper presents an adaptive hybrid feedback control law for global asymptotic tracking of a hybrid reference system for marine vehicles in the presence of parametric modeling errors. The reference system is constructed from a parametrized loop and a speed assignment specifying the motion along the path, which decouples the geometry of the path from the motion along the path. During flows, the hybrid feedback consists of a proportional-derivative action and an adaptive feedforward term, while a hysteretic switching mechanism that is independent of the vehicle velocities determines jumps. The effectiveness of the proposed control law is demonstrated through experiments

    Learn, Teach, Heal: Articulations of Indigeneity and Spirituality in Indigenous Tourism in British Columbia, Canada

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    ‘Learn, Teach, Heal’ encapsulates what seems to be occurring in Indigenous Tourism on Vancouver Island and the Haida Gwaii in British Columbia, Canada. Operating as a ‘Tourist-researcher’ in 2017 and 2018, I was there at a time when Indigenous Tourism was booming, partly facilitated by the political movement of Truth & Reconciliation. Tourism is often seen as a shallow, commercial and artificial activity, yet such a view risks speaking over the various reasons why hosts choose to engage in the industry. This dissertation offers a case study based on tours, performances and interviews with six people. The research foregrounds the voices and experiences of: Andy Everson, Tana Thomas, Roy Henry Vickers, Tsimka Martin, K’odi Nelson and Alix Goetzinger. In listening to how they present their work, I study how indigeneity and spirituality were being articulated in ways that relate to processes of decolonisation. Whilst they were all engaged in tourism for their own different reasons, a common theme that emerged was the goal to use tourism to learn, teach and heal, both for themselves and for their guests. Learning how to be guides and performers, their languages, traditional practices, histories and politics, they were able to explore with tourists aspects of their indigeneity and spirituality, illustrate diversity of peoples and practices, and teach about their values and hopes for the future. Healing is gained through having a space to learn and to teach, and to restore pride to the communities by taking control of the narratives. It is my contention that Indigenous Tourism is offering these six people sites of ‘becoming’ and ‘reclaiming’ in a way that puts decolonisation into practice

    Total dominator chromatic number of k-subdivision of graphs

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    Let G be a simple graph. A total dominator coloring of G, is a proper coloring of the vertices of G in which each vertex of the graph is adjacent to every vertex of some color class. The total dominator chromatic (TDC) number χdt(G) of G, is the minimum number of colors among all total dominator coloring of G. For any k ∈ ℕ, the k-subdivision of G is a simple graph G1/k which is constructed by replacing each edge of G with a path of length k. In this paper, we study the total dominator chromatic number of k-subdivision of G

    The more experienced, the better prepared? New evidence on the relation between teachers’ experience and their readiness for online teaching and learning

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    In 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

    Global sensitivity analysis and optimal design of heat recovery ventilation for zero emission buildings

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    Energy-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

    The more experienced, the better prepared? New evidence on the relation between teachers’ experience and their readiness for online teaching and learning

    No full text
    In 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

    Phytochemical characterization and anti-inflammatory activity of a water extract of Gentiana purpurea roots

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    Ethnopharmacological relevance Gentiana purpurea was one of the most important medicinal plants in Norway during the 18th and 19th centuries, and the roots were used against different types of gastrointestinal and airway diseases. Aim of the study To explore the content of bioactive compounds in a water extract from the roots, a preparation commonly used in traditional medicine in Norway, to assess the anti-inflammatory potential, and furthermore to quantify the major bitter compounds in both roots and leaves. Materials and methods G. purpurea roots were boiled in water, the water extract applied on a Diaion HP20 column and further fractionated with Sephadex LH20, reverse phase C18 and normal phase silica gel to obtain the low molecular compounds. 1D NMR, 2D NMR, and ESI-MS were used for structure elucidation. HPLC-DAD analysis was used for quantification. The inhibition of TNF-α secretion in ConA stimulated peripheral blood mononuclear cells (PBMCs) was investigated. Results Eleven compounds were isolated and identified from the hot water extract of G. purpurea roots. Gentiopicrin, amarogentin, erythrocentaurin and gentiogenal showed dose-dependent inhibition of TNF-α secretion. Gentiopicrin is the major secondary metabolite in the roots, while sweroside dominates in the leaves. Conclusions The present work gives a comprehensive overview of the major low-molecular weight compounds in the water extracts of G. purpurea, including metabolites produced during the decoction process, and show new anti-inflammatory activities for the native bitter compounds as well as the metabolites produced during preparation of the crude drug

    Thin steel plates exposed to combined ballistic impact and partially confined airblast loading

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    Pre-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

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