The dynamic inflow effect describes the unsteady aerodynamic response to fast changes in rotor loading due to the inertia of the wake. Fast changes in turbine loading due to pitch actuation or rotor speed transients lead to load overshoots. The phenomenon is suspected to be also relevant for gust situations; however, this was never shown, and thus the actual load response is also unknown. The paper’s objectives are to prove and explain the dynamic inflow effect due to gusts, and compare and subsequently improve a typical dynamic inflow engineering model to the measurements. An active grid is used to impress a 1.8m diameter model turbine with rotor uniform gusts of the wind tunnel flow. The influence attributed to the dynamic inflow effect is isolated from the comparison of two experimental cases. Firstly, dynamic measurements of loads and radially resolved axial velocities in the rotor plane during a gust situation are performed. Secondly, corresponding quantities are linearly interpolated for the gust wind speed from lookup tables with steady operational points. Furthermore,simulations with a typical blade element momentum code and a higher-fidelity free-vortex wake model are performed. Both the experiment and higher-fidelity model show a dynamic inflow effect due to gusts in the loads and axial velocities. An amplification of induced velocities causes reduced load amplitudes. Consequently, fatigue loading would be lower. This amplification originates from wake inertia. It is influenced by the coherent gust pushed through the rotor like a turbulent box. The wake is superimposed on that coherent gust box, and thus the inertia of the wake and consequently also the flow in the rotor plane is affected. Contemporary dynamic inflow models inherently assume a constant wind velocity. They filter the induced velocity and thus cannot predict the observed amplification of the induced velocity. The commonly used Øye engineering model predicts increased gust load amplitudes and thus higher fatigue loads. With an extra filter term on the quasi-steady wind velocity, the qualitative behaviour observed experimentally and numerically can be caught. In conclusion, these new experimental findings on dynamic inflow due to gusts and improvements to the Øye model enable improvements in wind turbine design by less conservative fatigue loads.
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Long-term care facilities are currently installing dynamic lighting systems with the aim to improve the well-being and behaviour of residents with dementia. The aim of this study was to investigate the implementation of dynamic lighting systems from the perspective of stakeholders and the performance of the technology. Therefore, a questionnaire survey was conducted with the management and care professionals of six care facilities. Moreover, light measurements were conducted in order to describe the exposure of residents to lighting. The results showed that the main reason for purchasing dynamic lighting systems lied in the assumption that the well-being and day/night rhythmicity of residents could be improved. The majority of care professionals were not aware of the reasons why dynamic lighting systems were installed. Despite positive subjective ratings of the dynamic lighting systems, no data were collected by the organizations to evaluate the effectiveness of the lighting. Although the care professionals stated that they did not see any large positive effects of the dynamic lighting systems on the residents and their own work situation, the majority appreciated the dynamic lighting systems more than the old situation. The light values measured in the care facilities did not exceed the minimum threshold values reported in the literature. Therefore, it seems illogical that the dynamic lighting systems installed in the researched care facilities will have any positive health effects.
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The dynamic inflow effect denotes the unsteady aerodynamic response to fast changes in rotor loading due to a gradual adaption of the wake. This does lead to load overshoots. The objective of the paper was to increase the understanding of that effect based on pitch step experiments on a 1.8 m diameter model wind turbine, which are performed in the large open jet wind tunnel of ForWind – University of Oldenburg. The flow in the rotor plane is measured with a 2D laser Doppler anemometer, and the dynamic wake induction factor transients in axial and tangential direction are extracted. Further, integral load measurements with strain gauges and hot-wire measurements in the near and close far wake are performed. The results show a clear gradual decay of the axial induction factors after a pitch step, giving the first direct experimental evidence of dynamic inflow due to pitch steps. Two engineering models are fitted to the induction factor transients to further investigate the relevant time constants of the dynamic inflow process. The radial dependency of the axial induction time constants as well as the dependency on the pitch direction is discussed. It is confirmed that the nature of the dynamic inflow decay is better described by two rather than only one time constant. The dynamic changes in wake radius are connected to the radial dependency of the axial induction transients. In conclusion, the comparative discussion of inductions, wake deployment and loads facilitate an improved physical understanding of the dynamic inflow process for wind turbines. Furthermore, these measurements provide a new detailed validation case for dynamic inflow models and other types of simulations.
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The effect of infill panels on the response of RC frames subjected to seismic action is widely recognised and has been subject of numerous experimental investigations, while several attempts to model it analytically have been reported. In this paper, the implementation, within a fibre-based Finite Elements program, of an advanced double-strut nonlinear cyclic model for masonry panels is described. The accuracy of the model is first assessed through comparison with experimental results obtained from pseudo-dynamic tests of large or full-scale frame models. This is followed by a sensitivity study whereby the relative importance of each parameter necessary to calibrate the model is evaluated, so that guidance on the general employment of the latter can be given. Furthermore, a representative range of values for the geometrical and material properties of the infill panels has been also defined. 1.
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In today’s intellectual capital literature, we see a shift from identifying intangibles towards understanding the dynamics of value creation. As it is not clear what “dynamic” stands for, the aim of this explorative and conceptual paper is to contribute to a better understanding of the dynamic dimension of IC. Based on a review of the early IC literature, the dynamic dimension (or dynamics) of intellectual capital seems to refer to the logic that value creation is the product of interaction between different types of (intangible) resources. As the idea of value creation through combination of knowledge resources is closely related to the New Growth Theory (Romer, 1990, 1994), this paper explores the New Growth Theory and its implications for the dynamic dimension of intellectual capital. Based on the exploration of the New Growth Theory, a conceptual model is presented in which the elements that constitute the dynamic dimension of intellectual capital are integrated. These elements are ideas, things, the process of knowledge creation, the process of continuous innovation, and institutions. The main conclusion of this paper is that the concept of knowledge is more closely related to the dynamic dimension of IC, than the concept of intellectual capital. Therefore, further research would probably benefit from approaching this topic from a knowledge management point of view. It is suggested that further research should focus on exploring the metaphors that contribute to a better understanding of the dynamics of IC, on the contribution that ideas can make to increase the effectiveness of knowledge management, and finally on the institutional arrangements that support the process of knowledge creation and innovation.
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The inefficiency of maintaining static and long-lasting safety zones in environments where actual risks are limited is likely to increase in the coming decades, as autonomous systems become more common and human workers fewer in numbers. Nevertheless, an uncompromising approach to safety remains paramount, requiring the introduction of novel methods that are simultaneously more flexible and capable of delivering the same level of protection against potentially hazardous situations. We present such a method to create dynamic safety zones, the boundaries of which can be redrawn in real-time, taking into account explicit positioning data when available and using conservative extrapolation from last known location when information is missing or unreliable. Simulation and statistical methods were used to investigate performance gains compared to static safety zones. The use of a more advanced probabilistic framework to further improve flexibility is also discussed, although its implementation would not offer the same level of protection and is currently not recommended.
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This research investigates the factors influencing the capital structure of 271 non-financial firms listed on the Korean Stock Exchange (KSE) over a broad period from 1995 to 2021, encompassing both stable and crisis conditions. Employing a dynamic panel data model and the generalized method of moments (GMM) estimation, we address the endogeneity issue introduced by the inclusion of lagged dependent variables. Our research integrates firm-specific internal factors with macroeconomic external variables to provide a comprehensive understanding of the influence of varying economic environments on capital structure. Our study suggests that in times of economic stability, the capital structure decisions of a firm are more influenced by internal factors such as profitability. However, in periods of economic downturns, it is the external macroeconomic market conditions that tend to have a greater impact on these decisions. It is also noteworthy that both book leverage (BL) and market leverage (ML) exhibit quicker adjustments during stable periods as opposed to periods of crisis. This indicates a higher agility of firms in adapting their capital structures in stable, normal conditions. Our findings contribute to the existing literature by offering a holistic view of capital structure determinants in Korean firms. They underscore the necessity of adaptable financial strategies that account for both internal dynamics and external economic conditions. This study fills a gap in current research, presenting new insights into the dynamics of capital structure in Korean firms and suggesting a multifaceted approach to understanding capital structure in diverse economic contexts.
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An important issue in the field of motion control of wheeled mobile robots is that the design of most controllers is based only on the robot’s kinematics. However, when high-speed movements and/or heavy load transportation are required, it becomes essential to consider the robot dynamics as well. The control signals generated by most dynamic controllers reported in the literature are torques or voltages for the robot motors, while commercial robots usually accept velocity commands. In this context, we present a velocity-based dynamic model for differential drive mobile robots that also includes the dynamics of the robot actuators. Such model has linear and angular velocities as inputs and has been included in Peter Corke’s Robotics Toolbox for MATLAB, therefore it can be easily integrated into simulation systems that have been built for the unicycle kinematics. We demonstrate that the proposed dynamic model has useful mathematical properties. We also present an application of such model on the design of an adaptive dynamic controller and the stability analysis of the complete system, while applying the proposed model properties. Finally, we show some simulation and experimental results and discuss the advantages and limitations of the proposed model.
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De zogenoemde “21th century skills” worden, aldus het Ministerie van Onderwijs, steeds belangrijker. Het zijn eigenschappen die we terugvinden in de eindtermen van vrijwel alle hbo-opleidingen en die – in de woorden van Donald Schön – de kern zijn van een “reflective practitioner” : een vakvrouw of –man, die zichzelf in complexe situaties kan sturen en daardoor productief blijft. Eerder onderzoek van het lectoraat Pedagogiek van de Beroepsvorming heeft aangetoond dat een leeromgeving gericht op zelfsturing aan drie condities moet voldoen: er moet sprake zijn van praktijkgestuurd onderwijs, studenten moeten de kans krijgen een dialoog aan te gaan over de zin en betekenis van hun ervaringen in het praktijkgestuurde onderwijs en studenten moeten medezeggenschap hebben over hun eigen leerproces. Met name het realiseren van een dialoog blijkt echter heel moeilijk te zijn. Zowel docenten als studenten (en ook de onderwijsmanagers) zijn gewend aan onderwijs waarin zin en betekenis nauwelijks ter discussie staat. Het gevolg is dat ze vooral gericht zijn op reproductief en niet op betekenis-gericht leren. Zelfsturing vereist evenwel deze laatste vorm van leren. Zelfsturing vereist een dialoog over de zin en betekenis van ervaringen die de student “raken”. Dergelijke ervaringen roepen veelal emoties op die in eerste instantie niet begrepen worden. Zin en betekenis zijn “geen dingen in een doosje”; ze worden gaandeweg duidelijk in een gesprek waarin de docent verklaart noch verheldert, maar samen met de student op zoek gaat naar de juiste woorden. Dat zijn woorden waarvan de student voelt dat ze haar in staat stellen iets uit te drukken dat voorheen nog niet onder woorden gebracht kon worden. In dit boek wordt vanuit verschillende perspectieven en op basis van empirisch onderzoek ingegaan op de vraag in hoeverre het hbo er in slaagt een dergelijke dialoog met haar studenten te realiseren. Tevens wordt stilgestaan bij methoden om zo’n dialoog te realiseren.
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Abductive thematic analysis blends empirical observations with theoretical frameworks, fostering a continuous and dynamic exchange between research evidence and theory. It is distinct from other forms of analysis as it is underpinned by pragmatism and is flexible in its adoption of theory to best answer the research question. As a result of an interplay between theory and data, a surprising, puzzling, or anomalous finding may lead to new insights. This flexible approach to inquiry can draw from theories dependent upon what is best able to explain the data. This results in a theoretically informed explanation for empirical phenomena, which may in turn unveil unique insights about theories, making it a valuable tool across diverse research domains in medical science. The guidelines in this paper aim to illuminate abductive thematic analysis, steering the reader through each step toward maximizing novel theoretical contributions and fostering a comprehensive understanding for researchers and educators.
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