Instabilities and turbulence in highly ionized plasmas in a magnetic field Semiannual status report, 1 Sep. 1970 - 28 Feb. 1971

Instabilities and turbulence in highly ionized plasmas in magnetic field related to problems of thrustors for manned space flight and plasma generated energ

Radiation temperature measurements of the nitrogen afterglow plasma

Radiation temperature measurements of nitrogen afterglow plasm

An x-band waveguide cell for study of microwave propagation through magnetoplasma technical report no. 16

Metal X-band waveguide cell for study of microwave propagation through magnetoplasm

Microwave measurement of the probability of collision of low energy electrons in nitrogen technical report no. 17

Collision probability for momentum transfer of low energy electrons in nitroge

Drag-free estimation feasibility study

A drag compensation system for solar probes and other spacecraft that require a drag-free capability is presented. Estimation techniques, derived from modern control theory, are proposed

Perception of Affordances for Dribbling in Soccer:Exploring Children as Architects of Skill Development Opportunity

This study examined affordance perception for soccer dribbling using a mixed-methods approach in male grassroots soccer players. We examined how children construct and perceive skills practices for dribbling in soccer. Fourteen boys aged 10–11 years (Mean ± SD = 10.8 ± 0.4 years) who were regularly engaged in grassroots soccer participated in the present study. Children were provided with ten soccer cones and asked to create their own soccer dribbling pattern that would enable them to maximise the number of touches with a football and then dribble the ball in the pattern they had created for a 1 min period. Children were interviewed to explore their perception of affordances for soccer dribbling. The test of gross motor development-3 was used to assess fundamental movement skills (FMS), and the UGent soccer dribbling test was used to assess soccer dribbling skills. Children self-rated their own ability for soccer dribbling, as did their coaches. Pearson’s correlations were employed to examine the associations between quantitative variables, and thematic analysis was used to explore qualitative data. Results of the present study suggest that those children who created patterns with less space between cones accrued more touches of the football in their dribbling task (r = −0.671, p = 0.03). Children with a higher perception of their own dribbling ability had higher scores for FMS (r = 0.604, p = 0.049). Those children who scored better in actual soccer dribbling had higher scores for FMS (r = −0.746, p = 0.012) and were rated as better dribblers by their coaches (r = −0.67, p = 0.03). Interview data suggest a feedback loop between perception of ability and actual ability, which influenced the dribbling patterns that were created. This suggests that dribbling performance is scaled to the (perceived) action capabilities of the children, and children can act as architects in their own skill developmen

Calibration and Cross-Validation of Accelerometery for Estimating Movement Skills in Children Aged 8-12 Years

This study sought to calibrate triaxial accelerometery, worn on both wrists, waist and both ankles, during children’s physical activity (PA), with particular attention to object control motor skills performed at a fast and slow cadence, and to cross-validate the accelerometer cut-points derived from the calibration using an independent dataset. Twenty boys (10.1 ±1.5 years) undertook seven, five-minute bouts of activity lying supine, standing, running (4.5kmph−1) instep passing a football (fast and slow cadence), dribbling a football (fast and slow cadence), whilst wearing five GENEActiv accelerometers on their non-dominant and dominant wrists and ankles and waist. VO2 was assessed concurrently using indirect calorimetry. ROC curve analysis was used to generate cut-points representing sedentary, light and moderate PA. The cut-points were then cross-validated using independent data from 30 children (9.4 ± 1.4 years), who had undertaken similar activities whilst wearing accelerometers and being assessed for VO2. GENEActiv monitors were able to discriminate sedentary activity to an excellent level irrespective of wear location. For moderate PA, discrimination of activity was considered good for monitors placed on the dominant wrist, waist, non-dominant and dominant ankles but fair for the non-dominant wrist. Applying the cut-points to the cross-validation sample indicated that cut-points validated in the calibration were able to successfully discriminate sedentary behaviour and moderate PA to an excellent standard and light PA to a fair standard. Cut-points derived from this calibration demonstrate an excellent ability to discriminate children’s sedentary behaviour and moderate intensity PA comprising motor skill activity.N/

“Football- It’s in Your Blood”—Lived Experiences of Undertaking Recreational Football for Health in Older Adults

Physical inactivity is prevalent in older adults and contributes to age-related decline in function, health, well-being, and quality of life. Recreational football for older adults has shown promise for promoting health benefits. This study explores the lived experiences of older adults engaging in a walking and recreational football intervention and identifies factors that affect behaviours and can encourage change in this population. A purposive sample (n = 14; aged 67 ± 5 years) of the lived experiences of those participating in a recreational football intervention took part in two focus groups. The participants’ responses were grouped into three-time reflecting specific points in their lives: what stopped them from playing football, what got them playing, and what is needed for them to continue playing in the future. Within each of these time points in their lives, themes were identified. The key findings and practical recommendations were that football needs to be adapted and local, that the priority to play football changes over time, and that football itself is a fundamentally intrinsic motivator; ‘it’s in your blood’. The findings can be used to inform future interventions, encourage participation, and advise on the best practices for key stakeholders in the physical activity domain

Development Methods and a Scenegraph Animation API for Cluster Driven Immersive Applications

This paper presents a scenegraph animation application programming interface (API), known as the Animation Engine, which was constructed for software developers to easily perform smooth transitions and manipulations to scenegraph nodes. A developer can use one line of code to enter the property, end state and number of frames to describe the animation, then the Animation Engine handles the rest in the background. The goal of the Animation Engine is to provide a simple API that integrates into existing applications with minimal effort. Additionally, techniques to improve virtual reality (VR) application performance on a large computer cluster are presented. These techniques include maintaining high frame rates with 4096 × 4096 pixel textures, eliminating extraneous network traffic and reducing long model loading time. To demonstrate the Animation Engine and the development techniques, an application known as the Virtual Universe was created. The Virtual Universe, designed to run in a six walled CAVE, allows users to freely explore a set of space themed environments. The architecture and development techniques for writing a stable immersive VR application on a large computer cluster, in addition to the creation of the Animation Engine, is presented in this paper

Contemporary practices of strength and conditioning coaches in professional soccer

This study describes the contemporary practices of strength and conditioning coaches in professional soccer. Fifty-two strength and conditioning coaches from professional leagues across 18 countries completed an online survey, consisting of 45 questions, with eight sections: (a) background information, (b) muscular strength and power development, (c) speed development, (d) plyometrics, (e) flexibility development, (f) physical testing, (g) technology use, and (h) programing. A frequency analysis was used to assess and report responses to fixed response questions, and thematic-analysis used for open-ended questions to create clear, identifiable and distinct themes. All strength and conditioning coaches were educated to degree level or higher, 65% held strength and conditioning certifications and 54% held soccer coaching certifications. Concentric (100%) and eccentric (98%) modes of resistance were the most commonly prescribed, whereas the squat (including variations) (52%) was deemed the most important exercise for soccer players. Hang clean (33%) and multiple hops/lunges (89%) were the most programed Olympic weightlifting and plyometric exercises. Global Positioning Systems (94%) were the most utilized technology-based equipment. Time, scheduling and fixtures were the biggest issues faced, which made it difficult to periodize training programs and apply appropriate training loads. Furthermore, strength and conditioning coaches would like to further integrate technology to comprehensively monitor and test players, while also believing that technology will continue to be developed and integrated in the future. Strength and conditioning coaches from professional soccer can use the information from this study to review current practices and also provide ideas for diversifying or modifying future practices