161 research outputs found
Dynamic wind farm flow control using free-vortex wake models
A novel dynamic economic model-predictive control strategy is presented that improves wind farm power production and reduces the additional demands of wake steering on yaw actuation when compared to an industry state-of-the-art reference controller. The novel controller takes a distributed approach to yaw control optimisation using a free-vortex wake model. An actuator-disc representation of the wind turbine is employed and adapted to the wind-farm scale by modelling secondary effects of wake steering and connecting individual turbines through a directed graph network. The economic model-predictive control problem is solved on a receding horizon using gradient-based optimisation, demonstrating sufficient performance for realising real-time control. The novel controller is tested in a large-eddy simulation environment and compared against a state-of-the-art look-up table approach based on steady-state model optimisation. Under realistic variations in wind direction and wind speed, the novel controller yields additional gains in power production during transients as well as a reduction in yaw actuator usage
Building and sustaining Work Engagement – A participatory action intervention to increase Work Engagement in nursing staff
This study evaluated whether a participatory action research intervention with nursing staff on
acute care older people NHS wards in the UK was effective for increasing work engagement.
Mediation analyses between job resources, (social support, influence in decision-making), job
demands, work-related needs (autonomy, competence, relatedness), and work engagement
explored the presumed psychological mechanisms underlying the intervention. A nonrandomised,
matched control group, pre-test, post-test design involved three intervention and
five control wards. A significant decrease in relatedness, and a borderline significant decrease
in competence, was observed in the intervention group compared to the control group, with no
effect on work engagement (N=45). Work-related needs mediated between resources and
work engagement, supporting the Job Demands-Resources model and Self-Determination
Theory as an underlying explanatory theory. Intervention implementation was difficult,
highlighting the need for participant and organisational readiness for change, and strong
management support. This is the first known study to apply participatory techniques to
increase work engagement in nursing staff and explore the underlying explanatory
psychological mechanisms, offering a novel means of taking work engagement research
forward. Crucially, it highlights the challenges involved in intervention research and the
importance of including evaluations of intervention implementation alongside statistical
evaluations to avoid erroneous conclusions
Expert Elicitation on Wind Farm Control
Wind farm control is an active and growing field of research in which the
control actions of individual turbines in a farm are coordinated, accounting
for inter-turbine aerodynamic interaction, to improve the overall performance
of the wind farm and to reduce costs. The primary objectives of wind farm
control include increasing power production, reducing turbine loads, and
providing electricity grid support services. Additional objectives include
improving reliability or reducing external impacts to the environment and
communities. In 2019, a European research project (FarmConners) was started
with the main goal of providing an overview of the state-of-the-art in wind
farm control, identifying consensus of research findings, data sets, and best
practices, providing a summary of the main research challenges, and
establishing a roadmap on how to address these challenges. Complementary to the
FarmConners project, an IEA Wind Topical Expert Meeting (TEM) and two rounds of
surveys among experts were performed. From these events we can clearly identify
an interest in more public validation campaigns. Additionally, a deeper
understanding of the mechanical loads and the uncertainties concerning the
effectiveness of wind farm control are considered two major research gaps
Course and prognosis of recovery for chronic non-specific low back pain: design, therapy program and baseline data of a prospective cohort study
Background: There has been increasing focus on factors predicting the development of chronic musculoskeletal disorders. For patients already experiencing chronic non-specific low back pain it is also relevant to investigate which prognostic factors predict recovery. We present the design of a cohort study that aims to determine the course and prognostic factors for recovery in patients with chronic non-specific low back pain. Methods/Design. All participating patients were recruited (Jan 2003-Dec 2008) from the same rehabilitation centre and were evaluated by means of (postal) questionnaires and physical examinations at baseline, during the 2-month therapy program, and at 5 and 12 months after start of therapy. The therapy protocol at the rehabilitation centre used a bio-psychosocial approach to stimulate patients to adopt adequate (movement) behaviour aimed at physical and functional recovery. The program is part of regular care and consists of 16 sessions of 3 hours each, over an 8-week period (in total 48 hours), followed by a 3-month self-management program. The primary outcomes are low back pain intensity, disability, quality of life, patient's global perceived effect of recovery, and participation in work. Baseline characteristics include information on socio-demographics, low back pain, employment status, and additional clinical items status such as fatigue, duration of activities, and fear of kinesiophobia. Prognostic variables are determined for recovery at short-term (5 months) and long-term (12 months) follow-up after start of therapy. Discussion. In a routine clinical setting it is important to provide patients suffering from chronic non-specific low back pain with adequate information about the prognosis of their complaint
Passive movement therapy in patients with moderate to severe paratonia; study protocol of a randomised clinical trial (ISRCTN43069940)
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Altered muscular activation during prone hip extension in women with and without low back pain
<p>Abstract</p> <p>Background</p> <p>Altered movement pattern has been associated with the development of low back pain (LBP). The purpose of this study was to investigate the activity pattern of the ipsilateral erector spinae (IES) and contralateral erectorspinae (CES), gluteus maximus (GM) and hamstring (HAM) muscles during prone hip extension (PHE) test in women with and without LBP. A cross-sectional non-experimental design was used.</p> <p>Methods</p> <p>Convenience sample of 20 female participated in the study. Subjects were categorized into two groups: with LBP (n = 10) and without LBP (n = 10). The electromyography (EMG) signal amplitude of the tested muscles during PHE (normalized to maximum voluntary electrical activity (MVE)) was measured in the dominant lower extremity in all subjects.</p> <p>Results</p> <p>Statistical analysis revealed greater normalized EMG signal amplitude in women with LBP compared to non-LBP women. There was significant difference in EMG activity of the IES (P = 0.03) and CES (P = 0.03) between two groups. However, no significant difference was found in EMG signals of the GM (P = 0.11) and HAM (P = 0.14) among two groups.</p> <p>Conclusion</p> <p>The findings of this study demonstrated altered activation pattern of the lumbo-pelvic muscles during PHE in the women with chronic LBP. This information is important for investigators using PHE as either an evaluation tool or a rehabilitation exercise.</p
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