996 resultados para Sound Speed
Resumo:
This study evaluated effects of defensive pressure on running velocity in footballers during the approach to kick a stationary football. Approach velocity and ball speed/accuracy data were recorded from eight football youth academy participants (15.25, SD=0.46 yrs). Participants were required to run to a football to cross it to a receiver to score against a goal-keeper. Defensive pressure was manipulated across three counterbalanced conditions: defender-absent (DA); defender-far (DF) and defender-near (DN). Pass accuracy (percentages of a total of 32 trials with 95% confidence limits in parenthesis) did not significantly reduce under changing defensive pressure: DA, 78% (55–100%); DF, 78% (61–96%); DN, 59% (40–79%). Ball speed (m·s−1) significantly reduced as defensive pressure was included and increased: DA, 23.10 (22.38–23.83); DF, 20.40 (19.69–21.11); DN, 19.22 (18.51–19.93). When defensive pressure was introduced, average running velocity of attackers did not change significantly: DA versus DF (m·s−1), 5.40 (5.30–5.51) versus 5.41 (5.34–5.48). Scaling defender starting positions closer to the start position of the attacker (DN) significantly increased average running velocity relative to the DA and DF conditions, 5.60 (5.50–5.71). In the final approach footfalls, all conditions significantly differed: DA, 5.69 (5.35–6.03); DF, 6 .22 (5.93–6.50); DN, 6.52 (6.23–6.80). Data suggested that approach velocity is constrained by both presence and initial distance of the defender during task performance. Implications are that the expression of kicking behaviour is specific to a performance context and some movement regulation features will not emerge unless a defender is present as a task constraint in practice.
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There has been an increasing number of fatal road crashes in Malaysia in the last two decades. Among those who die on Malaysian roads are children aged 0 to 18 years (i.e., 15.5% in 2009) (Mohamed, Wong, Hashim, & Othman, 2011) . The involvement of children in road trauma, and particularly children when they are in and around school zones, generates concern among the general public. The present study utilised an extended Theory of Planned Behaviour (TPB) framework, incorporating the additional predictors of mindfulness and habit, to understand drivers’ intention to comply with the school zone speed limit (SZSL). The study aimed to examine the extent to which TPB constructs, and additional predictors of mindfulness and habit, predicted drivers’ behavioural intention to comply with the SZSL. Malaysian drivers (N = 210) participated in this study via an online survey. Hierarchical regression was conducted, and the results showed that attitude, subjective norm, perceived behavioural control, and habit were significant predictors of intention to comply with the SZSL. Specifically, drivers who expressed more positive attitudes towards compliance, greater belief that significant others would want them to comply, and more confidence in their control of their speed were more likely to report an intention to comply. These drivers appear to have developed a positive habit of compliance, which may simply be a result of the engineering measures in place around school zones in Malaysia. Mindfulness was not a significant predictor in the final model. These findings provide some support for the explanatory value of the extended TPB framework in understanding the factors influencing drivers’ intention to comply with the SZSL. The present study also provides information of potential value in the development of interventions, such as public education and mass media campaigns, aimed at improving drivers’ compliance with the SZSL.
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Motorway off-ramps are a significant source of traffic congestion and collisions. Heavy diverging traffic to off-ramps slows down the mainline traffic speed. When the off-ramp queue spillbacks onto the mainline, it leads to a major breakdown of the motorway capacity and a significant threat to the traffic safety. This paper proposes using Variable Speed Limits (VSL) for protection of the motorway off-ramp queue and thus to promote safety in congested diverging areas. To support timely activation of VSL in advance of queue spillover, a proactive control strategy is proposed based on a real-time off-ramp queue estimation and prediction. This process determines the estimated queue size in the near-term future, on which the decision to change speed limits is made. VSL can effectively slow down traffic as it is mandatory that drivers follow the changed speed limits. A collateral benefit of VSL is its potential effect on drivers making them more attentive to the surrounding traffic conditions, and prepared for a sudden braking of the leading car. This paper analyses and quantifies these impacts and potential benefits of VSL on traffic safety and efficiency using the microsimulation approach.
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Introduction: Understanding the mechanical properties of tendon is an important step to guiding the process of improving athletic performance, predicting injury and treating tendinopathies. The speed of sound in a medium is governed by the bulk modulus and density for fluids and isotropic materials. However, for tendon,which is a structural composite of fluid and collagen, there is some anisotropy requiring an adjustment for Poisson’s ratio. In this paper, these relationships are explored and modelled using data collected, in vivo, on human Achilles tendon. Estimates for elastic modulus and hysteresis based on speed of sound data are then compared against published values from in vitro mechanical tests. Methods: Measurements using clinical ultrasound imaging, inverse dynamics and acoustic transmission techniques were used to determine dimensions, loading conditions and longitudinal speed of sound for the Achilles tendon during a series of isometric plantar flexion exercises against body weight. Upper and lower bounds for speed of sound versus tensile stress in the tendon were then modelled and estimates derived for elastic modulus and hysteresis. Results: Axial speed of sound varied between 1850 to 2090 m.s−1 with a non-linear, asymptotic dependency on the level of tensile stress in the tendon 5–35 MPa. Estimates derived for the elastic modulus ranged between 1–2 GPa. Hysteresis derived from models of the stress-strain relationship, ranged from 3–11%. These values agree closely with those previously reported from direct measurements obtained via in vitro mechanical tensile tests on major weight bearing tendons. Discussion: There is sufficiently good agreement between these indirect (speed of sound derived) and direct (mechanical tensile test derived) measures of tendon mechanical properties to validate the use of this non-invasive acoustic transmission technique. This non-invasive method is suitable for monitoring changes in tendon properties as predictors of athletic performance, injury or therapeutic progression.
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This study surveys and interrogates key conceptual frameworks and artistic practises that flow through the distinct but interconnected traditions of non-narrative film and experimental music, and examines how these are articulated in my own creative sound practise.
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Ramp metering is an effective motorway control tool beneficial for mainline traffic, but the long on-ramp queues created interfere with surface traffic profoundly. This study deals with the conflict between mainline benefits and thecosts of on-ramp and surface traffic. A novel local on-ramp queue management strategy with mainline speed recovery is proposed. Microscopic simulation is used to test the new strategy and compare it with other strategies. Simulation results reveal that the ramp metering with queue management strategy provides a good balance between the mainline and on-ramp performances.
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Young male drivers are over-represented in road-related fatalities. Speeding represents a pervasive and significant contributor to road trauma. Anti-speeding messages represent a long-standing strategy aimed at discouraging drivers from speeding. These messages, however, have not always achieved their persuasive objectives which may be due, in part, to them not always targeting the most salient beliefs underpinning the speeding behavior of particular driver groups. The current study elicited key beliefs underpinning speeding behavior as well as strategies used to avoid speeding, using a well-validated belief-based model, the Theory of Planned Behavior and in-depth qualitative methods. To obtain the most comprehensive understanding about the salient beliefs and strategies of young male drivers, how such beliefs and strategies compared with those of drivers of varying ages and gender, was also explored. Overall, 75 males and females (aged 17-25 or 30-55 years) participated in group discussions. The findings revealed beliefs that were particularly relevant to young males and that would likely represent key foci for developing message content. For instance, the need to feel in control and the desire to experience positive affect when driving were salient advantages; while infringements were a salient disadvantage and, in particular, the loss of points and the implications associated with potential licence loss as opposed to the monetary (fine) loss (behavioral beliefs). For normative influences, young males appeared to hold notable misperceptions (compared with other drivers, such as young females); for instance, young males believed that females/girlfriends were impressed by their speeding. In the case of control beliefs, the findings revealed low perceptions of control with respect to being able to not speed and a belief that something “extraordinary” would need to happen for a young male driver to lose control of their vehicle while speeding. The practical implications of the findings, in terms of providing suggestions for devising the content of anti-speeding messages, are discussed.
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Modern trains with different axle configurations, speeds and loads are used in railway networks. As a result, one of the most important questions of the mangers involved in bridge managements systems (BMS) is how these changes affect the structural behavior of the critical components of the railway bridges. Although researchers have conducted, many investigations on the dynamic effects of the moving loads on bridges, the influence of the changes in the speed of the train on the demand by capacity ratios of the different critical components of the bridge have not yet been properly studied. This study is important, because different components with different capacities and roles for carrying loads in the structure may be affected differently. To investigate the above phenomenon in this research, a structural model of a simply supported bridge is developed. It will be verified that the dynamic behavior of this bridge is similar to a group of railway bridges in Australia. Demand by capacity ratios of the critical components of the bridge, when it is subjected to a train load with different speeds will be calculated. The results show that the effect of increase or decrease of speed should not be underestimated. The outcome is very significant as it is contrary to what is currently expected, i.e. by reducing the speed of the train, the demand by capacity ratio of components may increase and make the bridge unsafe for carrying live load.
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The existing literature shows driving speed significantly affects levels of safety, emissions, and stress in driving. In addition, drivers who feel tense when driving have been found to drive more slowly than others. These findings were mostly obtained from crash data analyses or field studies, and less is known regarding driver perceptions of the extent to which reducing their driving speed would improve road safety, reduce their car’s emissions, and reduce stress and road rage. This paper uses ordered probit regression models to analyse responses from 3538 Queensland drivers who completed an online RACQ survey. Drivers most strongly agreed that reducing their driving speed would improve road safety, less strongly agreed that reducing their driving speed would reduce their car’s emissions and least strongly agreed that reducing their driving speed would reduce stress and road rage. Younger drivers less strongly agreed that these benefits would occur than older drivers. Drivers of automatic cars and those who are bicycle commuters agreed more to these benefits than other drivers. Female drivers agreed more strongly than males on improving safety and reducing stress and road rage. Type of fuel used, engine size, driving experience, and distance driven per week were also found to be associated with driver perceptions, although these were not found to be significant in all of the regression models. The findings from this study may help in developing targeted training or educational measures to improve drivers’ willingness to reduce their driving speed.
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Sound Musicianship is a book for music educators and musicians about musicianship—about musical skills, abilities, habits, sensibilities and understandings. Musicianship is explored as a form of craftsmanship. Like most crafts, music requires a balance of theoretical knowledge and practical skills that contribute to a highly tuned ability to appreciate and express music. In particular, the book explores general trends that influence musicianship in the twenty-first century, such as an increased reliance on digital media, greater awareness of the neurological basis for musical behaviour, a renewed interest in connections between bodily movements and musical expression, and increased cultural plurality resulting from more frequent travel, increased levels of migration and ubiquitous telecommunications. The book has a deliberate focus on the developmental aspects of musicianship, which will benefit those hoping to advance their own music learning or that of others. It includes a diverse range of views and perspectives on musicianship and is organised into five sections. The first four sections explore the implications of music understood as sound, experience, motion and culture, respectively. In these sections, leading researchers and thinkers outline important issues and debates that are relevant to developing the crafts of music making and they share insights into recent trends and understandings. The final section of the book looks at educational considerations and provides a series of case studies that document innovative approaches to developing musicianship. Readers will encounter some new, interesting and thought-provoking ideas within these pages. As we move further into the twenty-first century—with all the opportunities and challenges for music making it brings—the requirement to review our concepts of musicianship training will intensify, and the definition of a “sound basis” for a contemporary musicianship will evolve. This book is intended to help stimulate and inform that evolutionary process.
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The promise of ‘big data’ has generated a significant deal of interest in the development of new approaches to research in the humanities and social sciences, as well as a range of important critical interventions which warn of an unquestioned rush to ‘big data’. Drawing on the experiences made in developing innovative ‘big data’ approaches to social media research, this paper examines some of the repercussions for the scholarly research and publication practices of those researchers who do pursue the path of ‘big data’–centric investigation in their work. As researchers import the tools and methods of highly quantitative, statistical analysis from the ‘hard’ sciences into computational, digital humanities research, must they also subscribe to the language and assumptions underlying such ‘scientificity’? If so, how does this affect the choices made in gathering, processing, analysing, and disseminating the outcomes of digital humanities research? In particular, is there a need to rethink the forms and formats of publishing scholarly work in order to enable the rigorous scrutiny and replicability of research outcomes?
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In this practice-led research project I work to show how a re-reading and a particular form of listening to the sound-riddled nature of Gertrude Stein's work, Two: Gertrude Stein and her Brother, presents us with a contemporary theory of sound in language. This theory, though in its infancy, is a particular enjambment of sounded language that presents itself as an event, engaged with meaning, with its own inherent voice. It displays a propensity through engagement with the 'other' to erupt into love. In this thesis these qualities are reverberated further through the work of Seth Kim-Cohen's notion of the non-cochlear, Simon Jarvis's notion of musical thinking, Jean-Jacques Lecercle's notion of délire or nonsense, Luce Irigaray's notion of jouissant love and the Bracha Ettinger's notion of the generative matrixial border space. This reading then is simultaneously paired with my own work of scoring and creating a digital opera from Stein's work, thereby testing and performing Stein's theory. In this I show how a re-reading and relistening to Stein's work can be significant to feminist ethical language frames, contemporary philosophy, sonic art theory and digital language frames. Further significance of this study is that when the reverberation of Stein's engagements with language through sound can be listened to, a pattern emerges, one that encouragingly problematizes subjectivity and interweaves genres/methods and means, creating a new frame for sound in language, one with its own voice that I call soundage.
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This work was composed in relation to the author's research of the popularity of themes of ephemerality and affect in recent global art. This focus correlated with Chicks on Speed's ongoing inquiries into issues of collections and collecting in the artworld, articulated as 'the art dump' by the group. This work was subsequently performed as a contribution to a performance with international multidisciplinary group Chicks on Speed as a part of their residency during MONA FOMA in Tasmania.
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In this paper, a refined classic noise prediction method based on the VISSIM and FHWA noise prediction model is formulated to analyze the sound level contributed by traffic on the Nanjing Lukou airport connecting freeway before and after widening. The aim of this research is to (i) assess the traffic noise impact on the Nanjing University of Aeronautics and Astronautics (NUAA) campus before and after freeway widening, (ii) compare the prediction results with field data to test the accuracy of this method, (iii) analyze the relationship between traffic characteristics and sound level. The results indicate that the mean difference between model predictions and field measurements is acceptable. The traffic composition impact study indicates that buses (including mid-sizedtrucks) and heavy goods vehicles contribute a significant proportion of total noise power despite their low traffic volume. In addition, speed analysis offers an explanation for the minor differences in noise level across time periods. Future work will aim at reducing model error, by focusing on noise barrier analysis using the FEM/BEM method and modifying the vehicle noise emission equation by conducting field experimentation.
Resumo:
Background Commercially available instrumented treadmill systems that provide continuous measures of temporospatial gait parameters have recently become available for clinical gait analysis. This study evaluated the level of agreement between temporospatial gait parameters derived from a new instrumented treadmill, which incorporated a capacitance-based pressure array, with those measured by a conventional instrumented walkway (criterion standard). Methods Temporospatial gait parameters were estimated from 39 healthy adults while walking over an instrumented walkway (GAITRite®) and instrumented treadmill system (Zebris) at matched speed. Differences in temporospatial parameters derived from the two systems were evaluated using repeated measures ANOVA models. Pearson-product-moment correlations were used to investigate relationships between variables measured by each system. Agreement was assessed by calculating the bias and 95% limits of agreement. Results All temporospatial parameters measured via the instrumented walkway were significantly different from those obtained from the instrumented treadmill (P < .01). Temporospatial parameters derived from the two systems were highly correlated (r, 0.79–0.95). The 95% limits of agreement for temporal parameters were typically less than ±2% of gait cycle duration. However, 95% limits of agreement for spatial measures were as much as ±5 cm. Conclusions Differences in temporospatial parameters between systems were small but statistically significant and of similar magnitude to changes reported between shod and unshod gait in healthy young adults. Temporospatial parameters derived from an instrumented treadmill, therefore, are not representative of those obtained from an instrumented walkway and should not be interpreted with reference to literature on overground walking.